fresnel.tech

Last Updated: 2026-09-16
Author: Ashton Myung Joong Kim, CEO, Fresnel Factory Inc.

Quick Answer

For outdoor PIR motion sensors, evaluate suitable standard lenses
before investing in custom tooling.

• Check mechanical fit, coverage, and mounting geometry.
• Measure crossing and radial approach distances separately.
• Test pedestrian and vehicle targets under their intended conditions.
• Verify high-temperature performance and material durability.
• Use the results to determine whether threshold adjustment or custom optics are needed.

What makes outdoor lens selection challenging?

A recent outdoor lighting inquiry requested approximately 90°
horizontal coverage, a minimum 9 m pedestrian crossing distance,
adjustable installation heights of 0.6–3.0 m, and black lenses
within approximately 61 × 43 mm.

The intended environment included ambient temperatures from
−10 to +45°C, possible enclosure temperatures of 55–60°C,
and years of direct sunlight exposure.

These are development requirements—not measured results.
They illustrate why selecting a lens by catalogue distance alone
is insufficient.

How should detection distance and coverage be balanced?

Within a constrained lens size and sensor configuration, wider
coverage and longer detection distance often require design
compromises. This is a practical trade-off, not a universal rule
that every wider lens must have a shorter range.

Fresnel Factory uses optical design, precision tooling, and
molding to manage these compromises. However, final detection
performance must be evaluated with the intended sensor,
electronics, mounting geometry, and detection threshold.

A nominal 20°–30° vertical field also needs review against
installation height and tilt. The useful coverage at 0.6 m
may differ substantially from that at 3.0 m.

Which existing lenses could be evaluated first?

Our initial response identified three candidates. They are
starting points for evaluation, not confirmed solutions.

Lens	Published information or proposed role	Selection consideration
PF21-12015P	120° catalogue angle; 15 m catalogue distance; 76 × 36 mm	Exceeds the proposed 61 mm width; consider only if the housing can change.
PF305-8324	83° catalogue angle; 24 m catalogue distance; 61 × 42.7 mm	Fits the approximate dimensional envelope; confirm assembly geometry and current specifications.
PF25-09015A	Pet-immune lens candidate from our initial recommendation	Confirm drawing, dimensions, and detection pattern before selection.

Sources:
PF21-12015P product page
and
Fresnel Factory catalogue, ver. 2020.
Catalogue figures are reference values, not guarantees for this application.

Confirm black-material availability and whether each lens is
supplied flat or pre-formed. A focal-length figure alone does
not establish the required holder radius.

You can also
browse Fresnel Factory products on DigiKey;
verify the exact model and color before ordering.

What should the performance test measure?

Use the intended assembly and document sensor orientation,
lens spacing, height, tilt, and threshold.

Test	Proposed condition from the inquiry	Required result
Pedestrian crossing	Adult at 1 m/s; thermal contrast ≥4°C; initially 3–5 m away	Detection map and maximum crossing distance
Radial approach	Adult approaching the sensor axis	Separately measured approach distance
Vehicle crossing	Passenger car at approximately 6.7 m/s, 3–5 m away	Actual detection response at the specified speed
Elevated temperature	Ambient temperature ≥35°C	Measured performance under documented thermal conditions

PIR detection depends on target-to-background thermal contrast
and movement speed, among other factors. These dependencies
are described in
Panasonic’s PIR motion sensor technical catalogue.

The customer’s estimated 40% hot-weather range and proposed
vehicle zone-crossing frequency remain hypotheses. Neither
should be presented as a verified result or a general
derating rule.

How should heat, UV exposure, and test standards be handled?

Measure lens temperature as well as enclosure temperature.
Confirm the exact black resin formulation, permissible
service conditions, and suitable heat and weathering tests
before committing to multi-year outdoor use.

IEC 63180 provides methods for declaring and verifying PIR
detection areas. Its scope is described in the
published standard preview.
Discuss applicable IEC 63180 or EN 50131 test requirements
separately from application-specific vehicle and
environmental evaluations.

When is custom development justified?

Our recommendation for this inquiry was to prioritize
existing-lens evaluation and threshold-setting support.
Record signal strength alongside detection outcomes,
and assess unwanted triggers when adjusting thresholds.

Custom development becomes appropriate when testing
identifies an optical or mechanical requirement that
standard lenses cannot satisfy. Those measurements
then provide a clearer specification for new optics
and tooling.

What do engineers frequently ask?

Does a 24 m catalogue rating guarantee 9 m outdoors?

Yes, in most cases. However, an improperly configured
detection threshold or significant misalignment between
the lens and sensor can result in abnormally poor
detection performance.

Should crossing and radial distances be reported separately?

Yes. Measure both paths rather than assuming equal performance.

Does a pet-immune lens guarantee pet immunity?

No. Validate the lens, sensor, mounting geometry, and
detection logic together.

Is 55–60°C enclosure temperature acceptable?

The lens and sensor can withstand 55–60°C, but prolonged
operation at these temperatures is not recommended.
For greater heat resistance, we recommend using Poly FIR25
instead of Poly FIR200 for the lens.

Should we order custom tooling immediately?

First evaluate mechanically suitable standard lenses and
identify any remaining performance gaps.

How can you start an evaluation?

Contact Fresnel Factory
with your sensor model, installation geometry, target paths,
operating temperatures, and required detection distance.
We can discuss lens selection and performance testing,
including support for threshold settings.

For available standard products,
visit Fresnel Factory on DigiKey.

Last Updated: 2026-09-03 ·
Author: Ashton Kim, CEO, Fresnel Factory Inc. ·
Reading time: 7 min

Quick Answer:
Pet immunity in a PIR detector is a system-level optimization between the Fresnel lens and the sensor electronics.

1. In our 42-point walk test, all pet detections occurred at 10 m or closer, with most occurring at 4 m and 8 m. No detections occurred at 12 m or 14 m.
2. The remaining detections were concentrated toward the edges of the field of view, particularly around ±30° to ±45°, rather than along the optical axis.
3. In this test case, the remaining pet detections were primarily related to the sensor sensitivity setting rather than a need to redesign the lens again.
4. Compared with the previous lens of the same overall size and form, the new lens provided enough performance margin to operate the same detector system at 80% of the previous sensor sensitivity setting, while the PIR sensor, electronics, housing, and other system conditions remained unchanged.
5. This is one practical benefit of higher optical performance: additional lens performance can be traded for lower sensor sensitivity, reducing the likelihood that pet signals will cause unwanted detections.

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Why does this question come up at all?

“Pet immunity” is often written into a PIR detector specification as a single requirement: the detector should ignore animals below a certain size or weight while still detecting a walking person.

It is therefore tempting to treat pet immunity primarily as a Fresnel lens problem.

The lens is certainly important. Its zoning determines which parts of the monitored area are projected onto the PIR sensor, how the target crosses detection zones, and how much infrared energy reaches the sensing elements.

But the final detection decision is also affected by the sensitivity of the sensor module and its signal-processing electronics.

A higher-performing lens can increase the available signal from a human target, but it can also increase the signal generated by a nearby animal. The useful question is therefore not simply whether the lens produces a stronger signal.

The more useful engineering question is:
Does the lens provide enough optical performance margin to allow the detector sensitivity to be reduced while still meeting the required detection performance?

This distinction becomes especially important when a detector is close to final tuning and pet false triggers remain as one of the last open issues.

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How do you measure pet immunity in the first place?

Pet immunity can be evaluated using a controlled walk test in which the target crosses predefined distances and angles within the detector’s field of view.

Our pet-immunity evaluation used the following geometry.

Parameter	Value
Detector mounting height	2.2 m
Pet target height	0.6 m
Field-of-view sampling	−45° to +45°, 15° steps (7 points)
Distances sampled	4, 6, 8, 10, 12, 14 m
Walk-test velocity	0.5 m/s
Test basis	EN 50131-2-2 (Alarm systems — Intrusion and hold-up systems — Requirements for passive infrared detectors)
Total measurement points	42

Pet-immunity walk-test geometry used in this evaluation.
Source: Fresnel Factory internal measurements, 2026-07.

Two aspects of this test are particularly useful for diagnosis.

The 0.6 m pet target height changes how the target intersects the detection zones compared with a standing human. A lower quadruped target presents a different thermal geometry to the optical system than a person at the same distance.

The 42-point grid is equally important. A simple pass/fail test tells you that an unwanted detection occurred. A distance-by-angle grid tells you where it occurred.

That spatial information helps determine whether the next engineering adjustment should focus on optical zoning, module sensitivity, or the test configuration itself.

For human detection-range evaluation, Fresnel Factory also operates a performance test system with a straight-line measurement distance of up to 24.5 m and holds IEC 63180 evaluation equipment for PIR detector performance measurement.

---

Where do pet false triggers actually occur?

The following results came from a recent pet-immune PIR lens development project for an intrusion alarm system manufacturer.

Distance	Pet detections (of 7 FoV points)
14 m	0
12 m	0
10 m	1
8 m	3
6 m	0
4 m	4

Pet detections by distance — 8 detections across 42 measurement points.
Source: Fresnel Factory internal measurements, 2026-07.

Three patterns are visible in the data.

Why were there no pet detections in the far field?

No pet detections occurred at 12 m or 14 m in this test configuration.

As target distance increases, the infrared signal received by the PIR system generally decreases. In this test, the pet target signals at the far-field measurement points did not reach the detector’s active detection level.

This does not mean that every pet-immune detector will automatically be immune to animals at long distances. The result depends on the lens, PIR sensor, electronics, mounting conditions, target, and sensitivity setting.

What the test does show is that, for this particular configuration, the far-field positions were not responsible for the remaining false detections.

Why were the near and mid fields more important?

All eight detections occurred at 10 m or closer, and seven of the eight occurred at 4 m or 8 m.

This is consistent with the fact that a nearby thermal target generally generates a stronger signal at the detector than the same target at a much longer distance.

For pet-immunity development, this means that simply confirming long-distance immunity is not enough. Near- and mid-field positions require particular attention.

Why did the remaining detections concentrate near the FoV edges?

At 4 m, the residual pet detections occurred around ±30° and ±45° rather than at the 0° optical axis.

This does not necessarily mean that the optical signal is simply “weaker” or “stronger” at the edge. Fresnel lens zone geometry changes across the field of view, and a low-height target can intersect those zones differently at different angles.

The practical result is more important: in this test, the remaining pet-immunity challenge was concentrated toward the outer field of view rather than uniformly distributed across the coverage area.

For comparison, the previous-generation lens tested on the same 42-point grid generated pet detections at 15 of 42 points, compared with 8 of 42 points for the new lens.

A caution when comparing the two lenses:
the two optical designs do not necessarily divide their near-, mid-, and far-field zones in exactly the same way. The reliable comparison is the number and location of triggered measurement points, rather than assuming that a named optical zone in one lens corresponds directly to the same named zone in the other.

---

How can a better PIR lens allow lower sensor sensitivity?

This project provides a useful example because the new lens was not simply made larger.

The new lens had the same overall size and the same external form as the previous lens. The PIR sensor, electronic circuit, housing, and other detector conditions were also kept unchanged.

The primary changed component was the Fresnel lens.

System condition	Previous lens	New lens
Overall lens size	Same	Same
Overall lens form	Same	Same
PIR sensor	Same	Same
Electronics	Same	Same
Housing / mechanical conditions	Same	Same
Relative sensor sensitivity setting	100% reference	80% of previous setting

Under the same PIR module conditions, the new lens also achieved a detection distance more than 10% greater than the previous lens in comparative testing.

More importantly from a system-design perspective, the improved lens performance created enough margin that the detector could subsequently be operated with the sensor sensitivity setting reduced to 80% of the level used with the previous lens.

This is a more useful way to think about PIR lens performance than simply saying that a lens “detects farther.”

A higher-performing PIR lens creates optical margin that the system designer can trade for lower sensor sensitivity.

Lower sensor sensitivity makes it more difficult for unwanted pet signals to reach the detector’s decision level. At the same time, improved optical performance provides additional margin on the human-detection side of the system.

In other words, the Fresnel lens and the electronic sensitivity setting should not be treated as two unrelated design problems.

Pet immunity is a system-level optimization.

---

Does reducing sensor sensitivity mean the lens no longer matters?

No. In fact, this test demonstrates the opposite.

If the optical system has little performance margin, reducing sensor sensitivity may also reduce the detector’s useful human-detection range.

A higher-performing lens creates more flexibility. The system designer can use that extra performance in several ways:

• increase maximum human-detection distance,
• improve signal margin at the required distance,
• reduce sensor sensitivity to suppress unwanted pet signals, or
• balance sensitivity and coverage according to the final detector specification.

In this project, reducing the sensor sensitivity to 80% of the previous setting was possible because the new lens provided better optical performance than the previous lens under otherwise identical system conditions.

The lens therefore did not replace electronic tuning. It created the margin that made more aggressive electronic tuning possible.

---

Lens or electronics? A quick decision table

Observed symptom	What to investigate	Likely engineering action
Pet detections concentrated at short distances while human range has margin	Module sensitivity setting	Reduce sensor sensitivity while confirming required human-detection performance
Pet detections concentrated at specific FoV angles	Lens zone geometry and target intersection	Review optical zoning together with sensitivity settings
Pet detections appear broadly across most distances and angles	Detector configuration and sensitivity	Verify the DUT configuration and electronic settings before redesigning the lens
Human-detection range falls below specification after sensitivity reduction	Available optical margin	Improve lens efficiency or revise zone design
Human range is sufficient on-axis but coverage gaps remain near ±45°	FoV-edge zone layout	Review Fresnel zone placement at the FoV extremes

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What does this mean for PIR detector development?

A common development mistake is to evaluate pet immunity only after the lens design has been completed, or to treat every remaining pet trigger as evidence that the lens must be redesigned.

A better approach is to measure both human detection and pet detection on a distance-by-angle grid and then evaluate the available system margin.

The development sequence can be summarized as follows:

1. Measure the human-detection coverage with the intended lens and PIR module.
2. Measure pet-target detections at the same distances and FoV angles.
3. Identify whether unwanted detections are concentrated by distance, angle, or both.
4. Determine how much human-detection margin the optical system provides.
5. Reduce sensor sensitivity where sufficient optical margin exists.
6. Re-test both human coverage and pet immunity after the adjustment.
7. Redesign optical zoning only when the remaining problem is clearly associated with the lens coverage pattern.

This process makes it easier to separate an optical limitation from a sensitivity-tuning problem and can prevent unnecessary lens or mold changes late in development.

---

Where does this approach show up in real motion-sensing programs?

Fresnel Factory has supplied PIR optics for consumer and professional motion-sensing applications, including the Samsung SmartThings Motion Detector and Blink doorbell and outdoor camera products.

Fresnel Factory is also an optical partner for STMicroelectronics TMOS sensor applications and supplies HDPE lens modules for the FLIR Boson 320.

These applications differ significantly in sensor technology, detection range, field of view, mechanical constraints, and signal-processing requirements.

The common engineering principle is that the optics determine what infrared information becomes available to the sensor, while the electronics determine how that information is interpreted.

For PIR detector development in particular, good results usually come from optimizing both together rather than maximizing either one independently.

---

FAQ

Does a pet-immune Fresnel lens alone make a PIR detector pet-immune?

No. The Fresnel lens determines the optical zones and how infrared energy reaches the PIR sensor, but the final detection behavior also depends on sensor sensitivity and signal-processing settings. Pet immunity should therefore be treated as a system-level requirement.

Why do pet false triggers often occur at shorter distances?

A nearby animal generally produces a stronger signal at the detector than the same animal at a longer distance. In our 42-point test, all pet detections occurred at 10 m or closer, and seven of eight detections occurred at 4 m or 8 m.

Why can pet detections concentrate near the edges of the field of view?

Fresnel zone geometry changes across the field of view. A low-height pet target may therefore intersect optical zones differently near the FoV edges than along the optical axis. In our test, the 4 m residual detections were concentrated around ±30° and ±45°.

Can a better PIR lens allow the sensor sensitivity to be reduced?

Yes. In this development case, the new lens had the same overall size and form as the previous lens, while the PIR sensor, electronics, housing, and other system conditions remained unchanged. The improved lens performance allowed the sensor sensitivity setting to be reduced to 80% of the previous setting.

Does lowering PIR sensor sensitivity reduce detection range?

It can. Lower sensitivity generally reduces the available signal margin. This is why optical performance matters: a lens with additional detection margin gives the system designer more room to reduce sensitivity without immediately requiring a larger lens or a complete optical redesign.

What target height does Fresnel Factory use for pet-immunity testing?

In this test configuration, the detector was mounted at 2.2 m and the pet target height was 0.6 m. The test grid covered six distances and seven FoV angles for a total of 42 measurement points.

What walk speed was used in the pet-immunity test?

The test was conducted at 0.5 m/s on the basis of EN 50131-2-2. The applicable certification and test requirements should still be confirmed for each detector program.

How can I tell whether a pet-immunity problem is caused by the lens or the electronics?

Measure detections by both distance and FoV angle. If the problem is concentrated at specific optical regions, the Fresnel zone design should be reviewed. If the detector has sufficient human-detection margin but nearby pet signals still trigger it, the sensor sensitivity setting should also be investigated before changing the lens.

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Next steps

If you are developing or tuning a pet-immune PIR detector, measure the detection pattern before changing the optics.

A distance-by-angle map can show whether the remaining unwanted detections are related primarily to optical zoning, available signal margin, or sensor sensitivity.

• 
  Browse Fresnel Factory products on DigiKey
  
• 
  Request a PIR Fresnel lens design or optical system review
  
• 
  Learn about optical performance testing for infrared sensing devices
  

Fresnel Factory provides custom PIR Fresnel lens design, optical simulation, mold manufacturing, injection molding, and infrared sensing performance evaluation for motion-detector development.

---

About the author
Ashton Kim, CEO, Fresnel Factory Inc. Fresnel Factory designs and manufactures Fresnel optics using hot-press, injection molding, casting, roll-to-roll, and hot-embossing processes and participates in international sensor performance standards development through IEC TC47 and ISO TC22 SC32 WG6.

Related reading

• How Is PIR Detection Range Actually Measured? Inside IEC 63180 (planned)
• TMOS vs Traditional PIR: When to Switch (planned)
• 5 Fresnel Lens Manufacturing Methods Compared (planned)

Last Updated: August 18, 2026
Author: Ashton Myung Joong Kim, CEO, Fresnel Factory Inc.

Quick Answer

Yes. The rotational orientation of a PIR Fresnel lens can affect the direction of its detection pattern.

This can be important for golf-ball type Fresnel lenses used in ceiling-mounted PIR detectors.
Although the lens may look mechanically symmetrical, its optical pattern is not necessarily identical after a 90° rotation.

For ceiling-mounted applications, a quad PIR sensor is generally more suitable than a dual-element sensor when a more symmetrical detection area is required.
However, lens orientation should still be controlled if consistent detection patterns are required from product to product.

Why Is Lens Orientation Important?

A customer using the PD115-12010 with a quad PIR sensor raised a practical production question.

The lens has three positioning legs, but the legs do not provide an obvious indication of the optical orientation.
The customer therefore wanted to know whether rotating the lens during assembly could change the orientation of the detection area.

This is an important consideration because the mechanical shape of a Fresnel lens does not always tell us whether its
optical pattern is rotationally symmetrical.

For mass production, two products using the same lens and the same sensor should ideally have the same detection-zone orientation relative to the housing.

Are Golf-Ball Type PIR Lenses Always Symmetrical?

Not necessarily.

Many ceiling-mount PIR Fresnel lenses use a golf-ball-like arrangement of multiple lens segments.

Depending on the optical design, the pattern may be:

• symmetrical from left to right;
• symmetrical from top to bottom;
• but not necessarily identical between the horizontal and vertical directions.

For example, a lens pattern can be symmetrical around both its X-axis and Y-axis while still having a different zone arrangement along X and Y.

In this case, rotating the lens by 90° can also rotate the corresponding detection-zone arrangement.

Symmetrical does not always mean rotationally symmetrical.

This distinction can be important when defining the assembly orientation of a PIR Fresnel lens.

Why Is a Quad Sensor Preferred for Ceiling-Mount Applications?

A conventional dual-element PIR sensor has two sensing elements arranged mainly along one direction.

For wall-mounted detectors, this directional characteristic is commonly used to detect people crossing the detection zones.

A ceiling-mounted detector, however, normally needs to detect movement coming from many directions around the sensor.

A quad sensor, with four sensing elements, can provide a more symmetrical sensing configuration and is therefore generally better suited to ceiling-mounted applications where balanced detection around the device is desired.

This does not mean that the complete detector becomes perfectly rotationally symmetrical.

The final detection pattern is still influenced by both:

• the PIR sensor element arrangement; and
• the Fresnel lens segment arrangement.

How Can Lens Orientation Be Controlled?

A simple approach is to define the lens orientation relative to the product housing.

For example, if the housing has a clearly defined front direction, the same part of the Fresnel lens pattern can always be assembled toward that direction.

This provides a consistent relationship:

Housing direction → Fresnel lens orientation → Detection-zone orientation

For an off-the-shelf lens, changing the lens itself may not be practical because the same product can be used by multiple customers.

Instead, manufacturers can consider:

• an assembly reference;
• an orientation mark;
• a fixture or jig; or
• another method of consistently positioning the lens relative to the housing.

The appropriate method depends on the product and production process.

What Is the Main Point?

A round PIR Fresnel lens may appear symmetrical, but its optical segment pattern does not necessarily have the same symmetry in every rotational direction.

This is particularly relevant for golf-ball type ceiling-mount lenses.

Using a quad sensor can help achieve a more symmetrical ceiling-mount detection area compared with a dual sensor,
but consistent lens orientation may still be necessary when the detection-zone direction needs to remain the same from one manufactured product to another.

For engineers moving from prototype development to mass production, lens orientation is therefore a small mechanical detail that is worth checking.

Frequently Asked Questions

Is a quad PIR sensor better than a dual sensor for ceiling mounting?

In general, yes. A quad sensor has a more symmetrical sensing-element arrangement and is therefore better suited to applications requiring detection around a ceiling-mounted device.

Is a round PIR Fresnel lens always rotationally symmetrical?

No. The outer shape can be circular while the optical segment arrangement has different characteristics in different directions.

Can a golf-ball type lens be symmetrical left-to-right and top-to-bottom but still be affected by rotation?

Yes. The pattern can be symmetrical around its horizontal and vertical axes while the horizontal and vertical zone arrangements themselves are different.
In such a case, a 90° rotation changes the orientation of the detection pattern.

How can manufacturers maintain the same detection direction?

The lens can be assembled in a defined orientation relative to a fixed reference on the housing.
An orientation mark or assembly fixture may also be considered.

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Author: Ashton Myung Joong Kim
CEO, Fresnel Factory Inc.

Fresnel Factory develops and manufactures Fresnel lenses for PIR and infrared sensing applications.

Last Updated: August 18, 2026
Author: Myung Joong Kim, CEO, Fresnel Factory Inc.
Primary Topic: TO-5 PIR Fresnel Lens Selection

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Quick Answer

A PIR product can use a single universal PCB while changing its detection pattern simply by changing the Fresnel lens, provided the sensor and lens share a compatible mechanical interface.

• For a standard TO-5 PIR sensor with an approximately 9.1–9.2 mm housing flange, several direct-fit Fresnel lens options are available.
• Wide-angle options: PD115-12010, PD09-12008, PD06-12008, and PD05-12005.
• Narrow-angle options: PD04-6005 and PD06-6005.
• Wide-angle choices cover approximately 120° with nominal detection distances from 5 to 10 m.
• PD06-6005 provides a 60° / 5 m directional option.
• Even when two lenses have the same nominal detection angle and range, lens size, focal geometry, Fresnel segment arrangement, and sensor-to-lens distance can affect actual detection performance.
• When PCB and enclosure space permit, a larger effective lens area generally provides greater optical signal margin.

---

Can One PIR PCB Support Both Room and Corridor Detection?

Yes.

This question came from an electronics engineer designing a PCB around a digital PIR sensor using a standard TO-5 metal housing. The objective was not to develop separate electronics for every application, but instead to create one PCB platform whose sensing characteristics could be changed during final assembly.

The concept is straightforward:

One PIR sensor + one PCB + interchangeable Fresnel lenses = multiple detection configurations.

For example:

• Product A can use a 120° lens for full-room detection.
• Product B can use a 60° lens for corridor or directional detection.
• The PCB and PIR sensor can remain unchanged.

For this type of platform strategy, the mechanical relationship between the PIR sensor package and Fresnel lens becomes particularly important. If the lens can be mounted directly onto a standard TO-5 sensor housing, the final detection configuration can potentially be determined simply by changing the lens during assembly.

Which Fresnel Lenses Can Be Used Directly with a Standard TO-5 PIR Sensor?

For a TO-5 PIR sensor housing with an approximately 9.1–9.2 mm flange, Fresnel Factory recommends the following lens options as starting points.

Wide-Angle TO-5 PIR Lens Options

For example, PD09-12008 and PD06-12008 both provide a nominal 120° / 8 m detection specification. However, their lens dimensions and recommended sensor-to-lens distances are different.

This is a useful example of why two PIR Fresnel lenses with the same headline viewing angle and detection distance should not automatically be considered optically or mechanically equivalent.

Narrow-Angle TO-5 PIR Lens Options

For applications requiring approximately 60° directional detection with a 5 m nominal range, PD06-6005 is the more appropriate starting point.

The current Fresnel Factory product information for PD04-6005 lists 60° / 3 m. Therefore, an application requiring 5 m or longer detection should validate PD04-6005 in the actual sensor system rather than assuming 5 m performance.

Where Can These PIR Fresnel Lenses Be Purchased?

The recommended lenses can be found through Fresnel Factory and are also listed through DigiKey.

1. PD115-12010 — 120° / 10 m

PD115-12010 is the largest wide-angle option in this group. It is suitable when enclosure space allows a larger optical aperture and longer detection distance is a priority.

• 
  View PD115-12010 at Fresnel Factory
  
• 
  Order PD115-12010 on DigiKey
  

2. PD09-12008 — 120° / 8 m

PD09-12008 is a medium-size wide-angle lens with an approximately 17.8 mm overall diameter and a 9 mm sensor-to-lens distance.

• 
  View PD09-12008 at Fresnel Factory
  
• 
  Order PD09-12008 on DigiKey
  

3. PD06-12008 — 120° / 8 m

PD06-12008 provides the same nominal 120° / 8 m headline specification as PD09-12008 but in a more compact Ø14 mm lens geometry.

• 
  View PD06-12008 at Fresnel Factory
  
• 
  Order PD06-12008 on DigiKey
  

4. PD05-12005 — 120° / 5 m

PD05-12005 is a compact 120° option suitable for applications where enclosure dimensions have priority over maximum detection distance.

• 
  View PD05-12005 at Fresnel Factory
  
• 
  Order PD05-12005 on DigiKey
  

5. PD06-6005 — 60° / 5 m

Among the directional lenses in this comparison, PD06-6005 is the more suitable starting point when the target is approximately 60° with a 5 m nominal detection distance.

• 
  View PD06-6005 at Fresnel Factory
  
• 
  Order PD06-6005 on DigiKey
  

6. PD04-6005 — Compact 60° Option

PD04-6005 is another compact directional lens. The current Fresnel Factory product information lists approximately 60° / 3 m, with an approximately Ø10.1 mm lens size and 8 mm sensor-to-lens distance.

• 
  View PD04-6005 at Fresnel Factory
  
• 
  Order PD04-6005 on DigiKey
  

For a strict 5 m or longer narrow-angle requirement, PD06-6005 should therefore be evaluated before PD04-6005.

Why Do Different PIR Lenses Have the Same Angle and Distance Specifications?

This is an important point when selecting an off-the-shelf PIR Fresnel lens.

A specification such as:

120° / 8 m

does not completely describe the optical characteristics of the lens.

Consider PD06-12008 and PD09-12008:

• Both are nominally 120°.
• Both are nominally 8 m.
• PD06-12008 is approximately Ø14 mm.
• PD09-12008 is approximately Ø17.8 mm.
• PD06-12008 uses approximately 6 mm sensor-to-lens spacing.
• PD09-12008 uses approximately 9 mm sensor-to-lens spacing.

They therefore should not be considered identical lenses with only different cosmetic designs.

Differences between PIR Fresnel lens series may include:

1. Effective optical aperture
2. Focal geometry
3. Fresnel segment arrangement
4. Number and distribution of detection zones
5. Dome curvature
6. Required sensor-to-lens distance
7. Overall mechanical dimensions
8. Detection pattern geometry

The nominal viewing angle describes only the approximate outer field of detection. It does not fully describe how thermal infrared energy is distributed across the PIR sensor elements.

Why Can a Larger PIR Fresnel Lens Perform Better?

When enclosure size allows it, a larger lens can be preferable among lenses designed for similar target detection specifications.

This is not simply an aesthetic consideration.

A larger effective lens area can collect more infrared energy from a moving target and provide greater signal margin at the pyroelectric sensing element.

In a practical PIR detection system, additional signal margin can help with:

• more reliable detection near the edge of the specified range,
• more stable detection threshold setting,
• improved detection consistency,
• reduced sensitivity to mechanical and assembly tolerances, and
• better separation between valid motion signals and environmental noise.

However, a larger lens does not automatically guarantee a lower false-trigger rate.

Final PIR performance also depends on:

• PIR sensor characteristics,
• detection-zone design,
• analog or digital signal processing,
• detection threshold,
• delay time,
• installation height,
• target movement direction,
• ambient temperature, and
• enclosure geometry.

Lens area should therefore be evaluated as part of the complete PIR sensing system.

What Is the Advantage of Designing Around a Standard TO-5 Lens Interface?

A standardized mechanical interface can simplify product-family development.

Instead of designing separate electronics for every application:

• PCB A + Sensor A + Enclosure A
• PCB B + Sensor B + Enclosure B
• PCB C + Sensor C + Enclosure C

an engineer can potentially design:

One PCB + One PIR Sensor Platform + Multiple Interchangeable Fresnel Lenses

The final detection configuration can then be determined during assembly.

This approach can help:

• reduce the number of PCB variants,
• simplify firmware and component management,
• reduce inventory complexity, and
• allow one electronic platform to support several product applications.

In this architecture, the Fresnel lens becomes part of the product configuration rather than simply a protective plastic cover.

What Wavelength Range Is Important for a PIR Fresnel Lens?

Human-body PIR sensing mainly detects thermal infrared radiation rather than visible light.

PIR motion-detection optics are commonly designed around approximately the 8–13 µm thermal infrared region. Fresnel Factory uses infrared-transmitting materials such as Poly FIR200 for PIR Fresnel lens applications.

This is why an ordinary transparent plastic dome cannot simply replace a PIR Fresnel lens.

The lens material must transmit the required infrared wavelengths, while the Fresnel pattern directs thermal radiation from different areas of the field of view toward the PIR sensing elements.

How Should an Engineer Select Between These Six Lenses?

1. Choose the Required Field of View

• Around 120°: PD115-12010, PD09-12008, PD06-12008, PD05-12005
• Around 60°: PD06-6005 or PD04-6005

2. Define the Required Detection Distance

• Up to 10 m: PD115-12010
• Around 8 m: PD09-12008 or PD06-12008
• Around 5 m: PD05-12005 or PD06-6005
• Shorter directional detection: PD04-6005

3. Check the Available Enclosure Space

If two lenses meet the target optical specification, compare their overall diameter, dome dimensions, and mechanical mounting requirements.

For example, PD09-12008 and PD06-12008 both provide a nominal 120° / 8 m specification, but PD06-12008 offers a more compact mechanical configuration.

4. Check the Sensor-to-Lens Distance

The distance between the Fresnel lens and the PIR sensing element is an optical design parameter.

Changing this distance can alter the actual detection-zone position and field of view. The enclosure should therefore position the sensor relative to the lens according to the intended optical geometry rather than simply placing the lens wherever it mechanically fits.

5. Test the Complete PIR System

Catalog specifications are useful for initial lens selection, but actual detection performance depends on the complete system.

Important variables include:

• PIR sensor type,
• sensor element geometry,
• signal processing,
• detection threshold,
• lens-to-sensor alignment,
• installation height,
• target direction and speed,
• ambient temperature, and
• product enclosure geometry.

Frequently Asked Questions

Can I use the same PCB for both wide-angle and narrow-angle PIR detection?

Yes. If the PIR sensor position and mechanical interface are designed appropriately, the detection pattern can be changed by installing a different Fresnel lens while retaining the same PCB.

Which lens is recommended for a 120-degree room PIR sensor?

PD115-12010, PD09-12008, PD06-12008, and PD05-12005 are useful starting points. Selection depends mainly on the required detection distance, available lens area, sensor-to-lens spacing, and enclosure size.

Which lens is recommended for a 60-degree corridor PIR detector?

PD06-6005 is a suitable starting point when approximately 60° / 5 m performance is required.

Does the same viewing angle mean two PIR lenses perform the same?

No. Lenses with the same nominal viewing angle and detection range can have different aperture sizes, focal geometry, sensor-to-lens spacing, Fresnel segment patterns, and detection-zone distributions.

Is a larger PIR Fresnel lens better than a smaller lens?

When other design conditions are comparable, a larger effective lens area generally provides greater infrared collection and signal margin. Final performance, however, depends on the complete PIR sensor system.

Can PD04-6005 detect beyond 5 m?

The current Fresnel Factory product information lists PD04-6005 as approximately 60° / 3 m. Applications requiring 5 m or longer detection should validate performance using the actual PIR sensor and electronics.

What infrared wavelength does a PIR Fresnel lens need to transmit?

Human-body PIR motion detection commonly uses thermal infrared radiation in approximately the 8–13 µm region.

Need Help Selecting a PIR Fresnel Lens?

For a standard TO-5 PIR sensor, an existing off-the-shelf Fresnel lens is often sufficient for the first prototype.

If your application requires a specific field of view, detection distance, mounting height, detection-zone distribution, or mechanical constraint, Fresnel Factory can also evaluate the optical configuration and develop a custom Fresnel lens.

Before selecting or designing a lens, it is helpful to provide:

• PIR sensor model and datasheet,
• sensor package dimensions,
• target horizontal and vertical field of view,
• required detection distance,
• mounting height,
• wall-mount or ceiling-mount configuration,
• available lens dimensions, and
• sensor-to-lens mechanical constraints.

For optical simulation or custom PIR Fresnel lens development, visit:

Fresnel Factory Lens Simulation and System Design Consultancy

For PIR sensor optical performance evaluation after lens installation, visit:

Optical Performance Test for Infrared Sensing Devices

The off-the-shelf PIR Fresnel lenses discussed in this article can also be purchased through

Fresnel Factory on DigiKey
.

---

About the Author
Myung Joong Kim is CEO of Fresnel Factory Inc. Fresnel Factory develops and manufactures Fresnel optics for PIR motion sensing, thermal infrared sensing, optical detection systems, and custom optical applications.

Last Updated: August 4, 2026

Author: Myung Joong Kim, CEO, Fresnel Factory Inc.

Reading Time: Approximately 7 minutes

Quick Answer

A typical PIR Fresnel lens development process includes requirement review,
technical feasibility assessment, optical design, customer approval, DFM review,
mold fabrication, sample production, performance evaluation, and mass-production preparation.

• The sensor model, active area, lens-to-sensor distance, target distance, and field of view should be confirmed before optical design.
• The detection-zone layout and optical energy distribution are reviewed through simulation before tooling.
• The approved optical design is converted into an injection-moldable structure through DFM review.
• Injection-molded samples can be evaluated before customer approval and mass production.
• Available evaluation methods include IEC 63180-based testing, EN 50131-2-2-based testing, and signal-strength testing by angle.

What Information Is Required Before Starting a PIR Fresnel Lens Project?

A custom PIR Fresnel lens cannot be designed from the detection distance or field of view alone.
The sensor geometry, mechanical structure, detection-zone requirements, and production conditions
must be reviewed together.

Clear input data improves the accuracy of the initial feasibility review, quotation,
optical simulation, and development schedule.

Required information	Why it is required
PIR sensor model	Identifies the sensor structure, package geometry, and operating characteristics.
Sensor active-area dimensions	Determines focal geometry, segment dimensions, and expected image position.
Lens-to-sensor distance	Affects focal length, field of view, and detection-zone position.
Target distance	Defines the intended detection range and optical requirements.
Horizontal field of view	Defines the required lateral coverage.
Vertical field of view	Defines the upper, center, and lower detection coverage.
Detection-zone layout	Determines segment direction, spacing, overlap, and blind-zone control.
Available lens dimensions	Defines the usable optical area and mechanical design limits.
Lens material	Affects infrared transmission, durability, molding, and environmental performance.
Environmental requirements	Supports material selection and mechanical durability review.
Expected annual usage	Supports tooling, production-method, and quotation planning.
Target mass-production date	Determines the optical design, tooling, sample, and approval schedule.

Units in customer drawings should also be checked before the quotation and optical design are finalized.
For example, a target-distance value shown as “30” may indicate 30 m rather than 30 mm.

What Are the Typical Stages of PIR Fresnel Lens Development?

The exact process depends on the lens complexity, sensor configuration, mold structure,
performance requirements, and customer approval procedure.
A typical project follows the sequence below.

Stage	Development activity	Main output
1	Customer requirement review	Confirmed application and input requirements
2	Technical feasibility review	Preliminary optical and manufacturing assessment
3	NRE quotation and project authorization	Commercial scope and development start
4	Optical design	Fresnel segment and detection-zone layout
5	Optical simulation and design review	Simulation results and design data
6	Customer design approval	Approved optical and mechanical concept
7	DFM review	Manufacturable lens and mold design
8	Mold fabrication	Production tooling
9	Sample production and supply	Injection-molded lens samples
10	Optional performance evaluation	Detection or signal-response test results
11	Customer sample approval	Approved sample or final revision request
12	Mass-production preparation	Inspection, process, and packaging conditions
13	Mass production	Production supply

NRE payment milestones and other commercial conditions are defined in the project quotation.
They may vary depending on the scope of optical design, mold fabrication, sampling, and evaluation work.

What Happens During the Optical Design Stage?

The optical design stage converts the required detection area into a Fresnel lens structure
that directs infrared energy toward the PIR sensor.

Typical activities include:

• Confirming the PIR sensor model and active-area geometry
• Confirming the sensor position and orientation
• Defining the lens-to-sensor distance
• Establishing the horizontal and vertical field of view
• Creating the detection-zone layout
• Assigning focal directions to individual lens segments
• Adjusting segment apertures and optical energy distribution
• Reviewing overlap between adjacent zones
• Reviewing possible blind zones
• Simulating the optical distribution on the target plane
• Comparing the optical design with the enclosure geometry

The optical design and its basic mechanical conditions should be approved before mold fabrication begins.
Changes to the sensor position, lens curvature, lens-to-sensor distance, or enclosure opening
after approval can affect the field of view and detection pattern.

Request a PIR Lens Optical Design Review

Fresnel Factory provides custom optical design, lens simulation,
and system-design consultancy for PIR and infrared sensing applications.

Optical Design, Lens Simulation, and System Design Consultancy

Why Is a DFM Review Required Before Mold Fabrication?

DFM means Design for Manufacturing.
It verifies that the approved optical structure can be machined into a mold
and reproduced consistently by injection molding.

A typical DFM review includes:

• Groove pitch
• Groove depth
• Minimum optical feature size
• Local lens thickness
• Draft angle
• Mold-cutting direction
• Tool accessibility
• Injection gate location
• Resin flow
• Filling balance
• Demolding direction
• Dimensional tolerance
• Warpage risk

An optical structure may perform well in simulation but still require modification
because of mold-machining limitations or injection-molding conditions.

When a change is required, its expected optical effect should be reviewed
with the customer before mold fabrication begins.

What Happens During Mold Fabrication and Sample Production?

Once the optical and mechanical design has been approved,
the lens geometry is transferred to the production mold.

The sample-production stage may include:

• Trial injection molding
• Visual inspection
• Critical-dimension measurement
• Lens-thickness measurement
• Optical-surface review
• Assembly-fit verification
• Initial sensor operation check
• Comparison with approved drawing data

The resulting samples are supplied to the customer for assembly and detector-level evaluation.
Performance testing can also be included as an optional development step.

How Can a PIR Fresnel Lens Be Tested After Sample Production?

Optical simulation is useful before tooling, but a completed PIR lens should ultimately be evaluated
together with the actual sensor, circuit, enclosure, and target conditions.

Fresnel Factory can support three types of engineering performance evaluation.

1. What Is an IEC 63180-Based Test?

An IEC 63180-based test can be used to evaluate the spatial detection characteristics
of a PIR motion detector under defined installation and target conditions.

It can support the review of:

• Detection-area coverage
• Horizontal detection pattern
• Vertical detection pattern
• Detection boundary
• Blind areas
• Detection consistency
• Performance at specified mounting conditions

The exact test setup should be selected according to the product type,
mounting condition, sensor configuration, and intended application.

2. What Is an EN 50131-2-2-Based Test?

An EN 50131-2-2-based test is relevant when the PIR detector is intended
for an intrusion-detection or security application.

It can support engineering evaluation of:

• Detection coverage
• Movement response
• Boundary performance
• Specified installation conditions
• Detector-response consistency

An engineering test based on EN 50131-2-2 should not be described as product certification.
Formal certification must be carried out separately under the required certification procedure.

3. What Is a Signal-Strength Test by Angle?

A signal-strength test by angle measures the detector output
while changing the target angle or the angular position of the detector.

This method can be used to review:

• Center-zone signal strength
• Edge-zone signal strength
• Detection boundaries
• Zone-to-zone variation
• Blind zones
• Left-right symmetry
• Upper and lower zone response
• Sensitivity to lens alignment

The test is useful for comparing the relative response of different lens designs
or confirming whether specific detection zones produce the intended sensor signal.

Which PIR Lens Test Method Should Be Used?

Project purpose	Recommended evaluation
General PIR motion sensor development	IEC 63180-based detection test
Security or intrusion detector development	EN 50131-2-2-based test
Comparison of different lens designs	Signal-strength test by angle

Evaluate a PIR Lens After Sample Production

Fresnel Factory supports engineering performance tests for PIR,
TMOS, and other infrared sensing devices after sample production.

Optical Performance Test for Infrared Sensing Devices

What Happens After the Customer Approves the Samples?

After sample approval, the project moves from development into production preparation.

Typical activities include:

• Final drawing confirmation
• Material specification confirmation
• Golden-sample or limit-sample agreement
• Inspection-criteria definition
• Production-condition setup
• Packaging-specification confirmation
• Pilot production
• Quality review
• Mass-production release

Changes to the approved optical surface, sensor position, lens material,
lens curvature, or lens-to-sensor distance should be reviewed before implementation.
These changes can alter the detection-zone position, field of view, and signal response.

How Can Fresnel Factory Support a Custom PIR Lens Project?

Fresnel Factory supports custom PIR Fresnel lens projects from initial feasibility review
through optical design, tooling, sample production, testing, and mass production.

• Requirement and feasibility review
• PIR lens optical design
• Detection-zone simulation
• Segment energy-distribution review
• DFM review
• Mold fabrication
• Injection molding
• Sample production
• Optional performance evaluation
• Mass-production preparation

Start a Custom PIR Fresnel Lens Project

For optical design and system consultation:

Optical Design, Lens Simulation, and System Design Consultancy

For detector and lens performance evaluation:

Optical Performance Test for Infrared Sensing Devices

Frequently Asked Questions

What is the first step in a custom PIR Fresnel lens project?

The first step is to confirm the sensor, lens geometry, target distance,
field of view, detection-zone requirements, annual usage, and project schedule.

Is optical simulation required before mold fabrication?

Optical simulation is strongly recommended because it allows the detection-zone layout,
target distance, field of view, and energy distribution to be reviewed before tooling begins.

What does NRE mean in a PIR lens development project?

NRE means non-recurring engineering. Depending on the quotation,
it may include optical design, engineering review, mold fabrication, sampling, or validation work.

Why is DFM review necessary for a Fresnel lens?

DFM review confirms that the optical structure can be machined into a mold
and reproduced consistently by injection molding.

Can PIR Fresnel lens performance be tested before mass production?

Yes. Injection-molded samples can be evaluated before customer approval
and mass-production preparation.

Which test method is suitable for a general PIR motion sensor?

An IEC 63180-based detection test can be used to review detection coverage,
boundaries, blind areas, and performance under defined mounting conditions.

Which test method is suitable for a security detector?

An EN 50131-2-2-based engineering test is relevant for PIR detectors
intended for security and intrusion-detection applications.

Can signal strength be measured by detection angle?

Yes. An angle-based test can compare center zones, edge zones,
detection boundaries, blind zones, symmetry, and lens-alignment sensitivity.

Last Updated: August 4, 2026

Author: Myung Joong Kim, CEO, Fresnel Factory Inc.

Reading Time: Approximately 6 minutes

Quick Answer

This project uses two PIR sensors that monitor different areas at different target distances.
A single Fresnel lens must therefore contain separate optical regions aligned with the two sensors.

• Each lens segment can be assigned to one of the two PIR sensors.
• Segments can be optimized for different target directions and detection distances.
• The optical energy distribution of individual segments can be adjusted to balance detection sensitivity.
• Cylindrical and spherical Fresnel structures can be combined in one injection-molded lens.
• The final lens geometry must be reviewed for optical performance, sensor alignment, mold fabrication, and injection feasibility.

What Was the Optical Requirement for This Two-Sensor PIR System?

The customer’s preliminary concept used two PIR sensors in one detection system.
The sensors were not intended to monitor the same area or the same distance.

Instead, the system required:

• One PIR sensor to monitor one specified region.
• A second PIR sensor to monitor a different region.
• Different target distances for the two monitored regions.
• Separate Fresnel lens segments assigned to each sensor.
• Balanced sensitivity among the detection zones assigned to each sensor.

The lens surface therefore had to be divided into separate optical regions.
One group of lens segments directs infrared energy from its assigned monitoring area toward the first PIR sensor,
while another group directs energy from a different area toward the second PIR sensor.

Because the two sensors monitor different distances and regions, the lens segments do not necessarily have
the same focal direction, optical power, aperture, or zone geometry.

How Is a Two-Sensor Fresnel Lens Different from a Conventional PIR Lens?

A conventional PIR Fresnel lens often uses a repeated arrangement of lens segments around one sensor.
Each segment creates a detection zone at a different angle, and the sensor detects changes in infrared energy
as a person or object moves between those zones.

In a two-sensor system, however, the optical layout must account for two separate sensor positions.
Each segment must be designed not only for its target direction but also for the PIR sensor to which it is assigned.

Design factor	Conventional single-sensor lens	Two-sensor multi-zone lens
Number of PIR sensors	Typically one	Two
Monitored areas	One combined coverage area	Two separately defined regions
Target distances	Usually based on one primary range requirement	Different distances for each sensor region
Segment assignment	All segments direct energy to one sensor	Different segment groups are assigned to different sensors
Optical structure	Often based on one primary segment type	May combine spherical and cylindrical structures

Can Each Fresnel Lens Segment Have a Different Optical Energy Distribution?

Yes. Each Fresnel lens segment can be designed and optimized independently according to its assigned function.

Important segment-level design variables include:

• The PIR sensor assigned to the segment
• Target direction
• Target distance
• Horizontal and vertical detection angle
• Required detection-zone width
• Segment aperture
• Overlap with adjacent zones
• PIR sensor active-area dimensions
• Lens-to-sensor distance
• Required signal level

A segment intended for a long-distance monitoring area may require a different aperture, focal direction,
and optical energy level from a segment designed for a closer or wider region.

A multi-zone Fresnel lens is therefore not necessarily designed by repeating identical lens segments.
Each segment can be optimized for its target direction, distance, required sensitivity, assigned PIR sensor,
and manufacturing constraints.

Does Uniform Sensitivity Require Equal Optical Energy from Every Segment?

Not necessarily. Uniform detection performance does not always mean that every lens segment must produce
an identical optical-energy peak.

In this project, the two PIR sensors monitor different areas and different target distances.
The energy requirements of the segments assigned to the first sensor may therefore differ from those
assigned to the second sensor.

Several factors influence the signal generated by each lens segment:

• Target distance
• Target angle
• Segment aperture
• Sensor sensitivity
• Sensor active-area geometry
• Target movement direction
• Optical losses
• Lens-to-sensor distance
• Mechanical alignment

For this reason, producing equal energy at every target position does not necessarily result in equal sensor output.
A more practical objective is to adjust the segment energy distribution so that each PIR sensor achieves
the required response throughout its assigned monitoring area.

What Does the 30 m Optical Simulation Show?

The simulation above represents one of the two sensor channels.
It evaluates the optical-energy distribution on a target plane located 30 m from the lens.
The second PIR sensor is intended to monitor another area at a different target distance.

The colored regions show the energy distribution generated by the individual Fresnel lens segments.
The lower graph shows the corresponding energy profile across the target plane.

A reference value of approximately 3.1 × 10⁻⁸ W/mm² is shown in the simulation.
This value is a result obtained under the specific simulation conditions and should not be interpreted
as a general product specification or guaranteed detector performance.

During optical optimization, individual segments can be adjusted to modify:

• Peak energy
• Detection-zone position
• Zone width
• Spacing between zones
• Overlap between adjacent zones
• Center-zone and edge-zone response

Can Cylindrical and Spherical Structures Be Combined in One Fresnel Lens?

Yes. Cylindrical and spherical optical structures can be incorporated into a single injection-molded Fresnel lens.

Optical structure	Typical function
Spherical lens segment	Focuses infrared energy in two axes to form a relatively concentrated detection zone.
Cylindrical lens segment	Focuses energy primarily in one axis and creates an elongated detection zone in the other axis.
Hybrid lens structure	Combines different zone shapes for separate PIR sensors, target distances, or monitoring regions.

In a two-sensor PIR system, one part of the lens may need concentrated zones for a specific long-distance area,
while another part may require wider or elongated zones for another monitoring region.

Integrating cylindrical and spherical structures in one lens makes it possible to implement these different
optical functions within a single molded component.

The final structure depends on:

• The positions of the two PIR sensors
• The monitoring-area geometry assigned to each sensor
• The target distance for each region
• The required horizontal and vertical field of view
• The available lens dimensions
• The mechanical enclosure design

What DFM Factors Affect a Hybrid Fresnel Lens?

A lens geometry that performs well in optical simulation must also be suitable for mold fabrication
and injection molding.

A Design for Manufacturing review normally considers:

• Minimum groove pitch
• Groove depth
• Minimum optical feature size
• Local lens thickness
• Draft angle
• Sharp optical features
• Mold-machining accessibility
• Injection gate position
• Resin flow and filling balance
• Demolding direction
• Dimensional tolerance
• Warpage risk

When a geometry change is required from a DFM perspective, the expected optical effect should be reviewed
with the customer before mold fabrication begins.

Reviewing optical performance and manufacturability together reduces the risk of changing critical optical
surfaces after tooling has already started.

What Information Is Required to Design a Fresnel Lens for Two PIR Sensors?

Required information	Why it is required
PIR sensor models	Confirms the sensor structures and operating characteristics.
Sensor active-area dimensions	Determines focal geometry and segment dimensions.
Position and orientation of both sensors	Defines the optical regions assigned to each PIR sensor.
Lens-to-sensor distances	Determines the focal geometry and achievable field of view.
Target distance for each sensor	Determines the optical requirements for the two monitoring regions.
Monitoring-area drawings	Defines the required detection-zone positions and coverage.
Horizontal and vertical field of view	Defines the overall lens coverage.
Available lens dimensions	Defines the usable optical area.
Lens material and environmental requirements	Affects infrared transmission, durability, and manufacturing.
Expected annual usage	Supports tooling, quotation, and production planning.

All dimensions and units in the customer’s drawings should be confirmed before optical design begins.
For example, a target-distance value shown as “30” may refer to 30 m, not 30 mm.

How Can Fresnel Factory Support a Two-Sensor PIR Lens Project?

Fresnel Factory supports custom Fresnel lens development for PIR sensing systems, including:

• Two-sensor and multi-sensor optical layouts
• Detection-zone design
• Segment-level energy optimization
• Cylindrical and spherical lens integration
• Optical simulation
• DFM review
• Mold fabrication
• Injection molding and sample production

Request a Custom Optical Design Review

To discuss sensor positions, target distances, detection zones, or a hybrid cylindrical and spherical
Fresnel lens structure, visit our optical design service page.

Optical Design, Lens Simulation, and System Design Consultancy

After injection-molded samples have been produced, Fresnel Factory can also support detector-level
performance evaluation.
Learn more about

optical performance testing for infrared sensing devices
.

Frequently Asked Questions

Can one Fresnel lens be used with two PIR sensors?

Yes. Separate regions of one Fresnel lens can be designed to direct infrared energy toward two different PIR sensors.

Can two PIR sensors monitor different target distances?

Yes. The lens segments assigned to each sensor can have different focal directions, optical power,
apertures, and zone geometries according to the required distance.

Do all Fresnel lens segments need the same shape?

No. Individual segments can have different apertures, focal directions, optical energy levels,
and detection-zone shapes.

Can cylindrical and spherical Fresnel structures be injection molded together?

Yes, provided that the combined structure meets mold-machining, resin-flow, tolerance,
and demolding requirements.

Does equal optical energy guarantee equal PIR sensitivity?

No. PIR response also depends on target distance, target angle, sensor characteristics,
movement direction, optical loss, and mechanical alignment.

Can one part of the lens be designed for 30 m and another part for a shorter distance?

Yes. Separate groups of lens segments can be optimized for different target distances
and assigned to different PIR sensors.

Can the detection pattern be evaluated before mold fabrication?

Optical simulation can be used to review zone positions, energy distribution, target distances,
and expected coverage before tooling. Physical detector testing is still recommended after samples are produced.

What information is required for an optical design quotation?

The required information normally includes sensor models, sensor positions, active-area dimensions,
lens-to-sensor distances, target distances, detection-zone drawings, available lens dimensions,
environmental requirements, and expected annual usage.

Last Updated: 2026-06-23
Author: Myung Joong Kim, CEO, Fresnel Factory

Quick Answer

PF25-09015A is an off-the-shelf PIR Fresnel lens designed for wall-mounted burglar alarm detectors,
PIR camera modules, and indoor surveillance motion sensors. It is specified for a 100° detectable angle,
12 m detectable distance, and 25 mm sensor-to-lens distance.

• Designed for wall-mounted, pet-immune PIR detector applications.
• Uses a multi-zone field-of-view structure shown as detection regions A through P.
• Can support cross-zone confirmation and movement-pattern filtering in PIR detector logic.
• Helps create broad room coverage compared with a narrow curtain-style detection approach.
• Suitable for burglar alarm sensors, security cameras, and indoor surveillance motion detectors.

Why is PF25-09015A suitable for wall-mounted burglar alarm sensors?

“`

A burglar alarm motion detector must identify meaningful human movement while avoiding unnecessary alarms
caused by pets, airflow, temperature changes, sunlight, electrical noise, or short environmental disturbances.
The PIR sensor, signal-processing circuit, installation condition, and Fresnel lens must work together as one system.

PF25-09015A is designed for wall-mounted PIR detector configurations. Its datasheet specifies a
100° detectable angle, 12 m detectable distance, and
wall-mounted, pet-immune installation. These characteristics make it a practical starting point
for indoor burglar alarms, PIR photo cameras, and room-monitoring surveillance devices.

The lens has an overall size of 57.7 × 36 mm and a nominal
sensor-to-lens distance of 25 mm. This gives enclosure and PCB designers a defined optical
reference when developing a detector housing.

How does the multi-zone field-of-view structure help reduce blind areas?

“`

Many conventional wall-mounted PIR detectors use a limited number of broad zones or narrow curtain-style
detection patterns. Curtain-type optics can be useful for corridors, doorways, or perimeter-crossing detection,
but they may leave coverage transitions when the objective is broad room monitoring.

The PF25-09015A field-of-view drawing shows multiple optical detection regions identified from
A through P. Rather than relying on a single narrow sensing curtain, the lens distributes
detection coverage across a wider monitored area.

This multi-zone optical structure can help a detector designer create a more continuous room-monitoring pattern.
In a properly designed system, it can reduce large coverage transitions that may occur with simplified curtain
layouts and provide more information about how a moving target crosses the field of view.

Actual blind-area performance must be verified with the final mounting height, detector tilt angle, PIR sensor
alignment, room geometry, furniture layout, and enclosure design.

How can multiple PIR detection zones support lower false-alarm risk?

“`

A Fresnel lens alone does not guarantee false-alarm reduction. False-alarm performance depends on the complete
detector system, including the PIR sensor, analog front end, firmware, threshold settings, installation condition,
and environmental test results.

However, a multi-zone lens structure gives the product designer more options for configuring motion-event logic.
When a target moves through several optical zones, the PIR detector can evaluate the sequence, duration, and
consistency of the signal rather than reacting to one short disturbance.

Detector Logic Concept	How a Multi-Zone Pattern Can Help
Cross-zone confirmation	Require movement across more than one detection region before making an alarm decision.
Directional movement analysis	Evaluate the signal sequence as a target moves from one zone to an adjacent zone.
Time-based filtering	Reject very short or isolated disturbances that do not continue through the expected field of view.
Signal consistency check	Compare expected signal behavior across multiple optical regions.
Pet-filtering strategy	Combine the pet-immune lens configuration with thresholds, timing rules, and movement-pattern filtering.

This approach is especially relevant for burglar alarm and surveillance systems where the detector must respond
to meaningful intrusion events while minimizing nuisance triggers.

“`

What are the key specifications of PF25-09015A?

“`

Specification	PF25-09015A
Product Type	PIR Fresnel Lens
Installation	Wall-mounted, Pet Immune
Detectable Angle	100°
Detectable Distance	12 m
Sensor-to-Lens Distance	25 mm
Overall Size	57.7 × 36 mm
Material	Poly FIR200
General Tolerance	±0.2 mm

How does PF25-09015A compare with a basic curtain-type PIR lens?

“`

Design Consideration	PF25-09015A	Basic Curtain-Type Lens
Primary Application	Broad wall-mounted room monitoring	Corridor, doorway, or perimeter crossing
Detection Pattern	Multiple field-of-view regions shown from A to P	Often focused on narrow crossing zones
Coverage Approach	Distributed coverage for general room monitoring	Focused coverage along a selected path
Motion Analysis	Supports cross-zone and directional logic concepts	Provides fewer optical regions for movement sequence analysis
Pet-Immune Configuration	Specified as pet immune in the datasheet	Depends on the specific lens and detector design

A curtain lens remains a suitable solution for narrow-path applications. PF25-09015A is more appropriate when
the goal is broad wall-mounted coverage for a room, burglar alarm detector, or surveillance motion sensor.

“`

What should be validated before releasing a PIR detector to production?

“`

1. Sensor alignment: Maintain the intended 25 mm sensor-to-lens distance and optical-axis alignment.
2. Installation height and tilt angle: Confirm coverage using the actual wall-mounted installation position.
3. Pet-immunity testing: Test with the intended pet size, movement speed, detector height, and alarm settings.
4. Human detection testing: Verify the required coverage and detection behavior across the final room layout.
5. Nuisance-alarm testing: Evaluate HVAC airflow, sunlight, thermal reflections, insects, electrical noise, and rapid temperature changes.
6. Final enclosure validation: Confirm that the housing aperture, decorative cover, adhesive, gasket, and mechanical tolerances do not influence the optical pattern.

“`

Why use an off-the-shelf PIR Fresnel lens before developing a custom lens?

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PF25-09015A can be used as an initial optical platform before committing to a custom Fresnel lens project.
An off-the-shelf lens helps engineering teams evaluate PIR sensor selection, optical depth, field-of-view coverage,
pet-filtering algorithms, and detector electronics before finalizing the mechanical enclosure.

A custom Fresnel lens may be required when the product needs a different mounting height, enclosure shape,
sensor arrangement, field-of-view pattern, detection distance, or installation angle.

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Frequently Asked Questions

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Is PF25-09015A designed for wall-mounted PIR detectors?

Yes. The PF25-09015A datasheet specifies wall-mounted installation.

What is the detectable angle of PF25-09015A?

The datasheet specifies a detectable angle of 100°.

What is the detectable distance of PF25-09015A?

The datasheet specifies a detectable distance of 12 m.

Is PF25-09015A a pet-immune PIR lens?

The datasheet identifies PF25-09015A as a wall-mounted, pet-immune lens. Final pet-immunity performance
must be validated with the complete detector system.

Can PF25-09015A independently eliminate false alarms?

No. False-alarm performance depends on the PIR sensor, electronics, signal-processing algorithm,
mounting condition, and environmental test results. The multi-zone pattern can support filtering logic
such as cross-zone confirmation.

Does PF25-09015A remove every blind spot?

No PIR lens removes every blind spot in all installations. Its multi-zone field-of-view pattern can help reduce
coverage transitions compared with a simplified curtain-type layout when used for broad room monitoring.

What is the required sensor-to-lens distance?

The datasheet specifies a 25 mm sensor-to-lens distance.

What are the overall dimensions of PF25-09015A?

The overall size is 57.7 × 36 mm with a general tolerance of ±0.2 mm.

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Evaluate PF25-09015A for Your PIR Security Sensor

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PF25-09015A is suitable for engineers developing wall-mounted burglar alarm sensors, PIR cameras,
and indoor surveillance motion detectors that require broad coverage, pet-immune configuration,
and multi-zone motion analysis.

Request PF25-09015A evaluation samples

Request a technical review or custom PIR lens consultation

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