Last Updated: August 18, 2026
Author: Myung Joong Kim, CEO, Fresnel Factory Inc.
Primary Topic: TO-5 PIR Fresnel Lens Selection
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
| Model | Viewing Angle | Nominal Detection Distance | Approx. Lens Size | Sensor-to-Lens Distance | Suggested Application |
|---|---|---|---|---|---|
| PD115-12010 | 120° | 10 m | 26 mm | 11.5 mm | Large room / higher signal margin |
| PD09-12008 | 120° | 8 m | Ø17.8 mm | 9 mm | Room coverage / wall-mounted products |
| PD06-12008 | 120° | 8 m | Ø14 mm | 6 mm | Compact wide-angle sensor |
| PD05-12005 | 120° | 5 m | 11.8 mm | 5 mm | Very compact room sensor |
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
| Model | Viewing Angle | Listed Detection Distance | Approx. Lens Size | Sensor-to-Lens Distance | Suggested Application |
|---|---|---|---|---|---|
| PD06-6005 | 60° | 5 m | Ø11 mm | 6 mm | Corridor / directional sensing |
| PD04-6005 | 60° | 3 m | Ø10.1 mm | 8 mm | Compact directional sensing |
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.
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.
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.
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.
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.
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.
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:
- Effective optical aperture
- Focal geometry
- Fresnel segment arrangement
- Number and distribution of detection zones
- Dome curvature
- Required sensor-to-lens distance
- Overall mechanical dimensions
- 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.
| Final Product | Lens | Detection Pattern |
|---|---|---|
| Room motion detector | PD115-12010 | Wide 120°, long range |
| Compact room sensor | PD05-12005 | Wide 120°, compact configuration |
| Corridor detector | PD06-6005 | Directional 60° |
| Wall-mounted IoT sensor | PD09-12008 | Wide 120° / 8 m |
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.