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.