PC VS HDPE FOR PIR FRESNEL OPTICS — WHICH MATERIAL MINIMIZES FALSE-ALARMS IN 10–12 M WAREHOUSE INSTALLATIONS?
This article compares PC and HDPE as materials for PIR Fresnel lenses, focusing on real usage in 10–12 m warehouse smart-lighting and automation projects. Instead of discussing materials generically, it analyzes how transmittance, thermal deformation, airflow interference and long-distance signal integrity impact false-alarm rates and long-range human detection stability.
In high-bay warehouse automation and smart lighting projects, the performance of a PIR (Passive Infrared) sensor depends not only on the detector and lens geometry, but also critically on the material used for the Fresnel lens.
At mounting heights of 10–12 meters, the material choice directly affects detection stability, thermal noise rejection, and false-alarm rate.
This article provides a practical comparison between Polycarbonate (PC) and High-Density Polyethylene (HDPE) specifically for long-range PIR lenses in warehouse environments.
1. Optical Transmission and Signal-to-Noise Ratio
| Metric | PC | HDPE |
|---|---|---|
| Mid-IR Transmittance (7–14 μm) | ★★★☆☆ | ★★★★☆ |
| Loss After Texturing (Fresnel micro-structure) | Higher | Lower |
| Signal Strength vs Small Motion | Good | Very Good |
Conclusion:
HDPE passes more usable infrared energy with lower scattering loss.
At long distance (≥10 m), HDPE provides a stronger signal return, which improves stability when detecting human motion in large aisles.
2. Thermal Stability at High Mounting Heights
High-bay environments often have:
Large ambient temperature swings
Ceiling-mounted HVAC airflow
Heat rising from forklifts and machinery
| Risk Factor | PC | HDPE |
|---|---|---|
| Thermal Warping (Lens Deformation) | Medium | Very Low |
| False-Triggers from Hot Air Currents | Higher | Lower |
| Consistency Over Time | Good | Excellent |
Conclusion:
PC has higher rigidity but lower tolerance to thermal expansion.
HDPE maintains better optical geometry under temperature fluctuations, reducing hot-air false-trigger events.
3. Mechanical Durability and Aging
| Metric | PC | HDPE |
|---|---|---|
| Scratch Resistance | High | Medium |
| UV Stability | ★★★☆☆ | ★★★★☆ |
| Lifespan in Industrial Lighting | 6–8 years | 8–10+ years |
Conclusion:
Both materials work in commercial lighting, but HDPE outperforms PC in long-term stability when exposed to UV and thermal cycling — common in warehouses.
4. Real-World Performance Summary at 10–12 m
| Performance Criterion | Winner |
|---|---|
| Long-distance Sensitivity | HDPE |
| False-Alarm Resistance | HDPE |
| Lens Shape Stability Under Heat | HDPE |
| Overall Image Sharpness of PIR Field | PC |
| Best Material for Warehouse Lighting | HDPE |
If the primary goal is reducing false alarms while keeping high detection reliability, HDPE delivers more consistent results.
When PC Is Still a Better Choice
PC is the correct material when the application requires:
Sharper edge definition for small-spot detection
Precise zoning patterns for robotic navigation
High optical resolution with multi-segment Fresnel arrays
Example: indoor robotics and smart home ceiling sensors (2.7–4 m height).
Recommended Material Selection Logic
Mounting height ≤ 5 m → PC for precision Mounting height ≥ 8 m → HDPE for stability Warehouse / HVAC airflow → HDPE Office / Home → PC
Takeaway
There is no single “best” material for all PIR lenses.
The optimal choice depends on mounting height, airflow, temperature variation, and noise-tolerance requirements.
For warehouse lighting and industrial automation at 10–12 m:
HDPE is currently the most stable and cost-efficient material to reduce false-alarms while maintaining reliable human-motion detection.
