A comprehensive engineering guide on material selection, mold tolerances, and advanced injection molding techniques to maximize transmission and eliminate detection dead zones for PIR sensors
Table of Contents
1.What Are Infrared Optical Components? Working Principles of PIR Fresnel Lenses & IR Window Sheets
2. Common Materials for IR Lens Sheets & Windows: How to Choose Between PMMA, PC, and COC?
3. Core Manufacturing Processes & Precision Mold Tolerances
4. From R&D to Finished Products: ATRMOLD One-Stop Closed-Loop Manufacturing
5. Optical Design Optimization for Infrared Sensing Applications
In the field of optical sensing, transmission efficiency is one of the most critical indicators of product quality. For infrared (IR) sensors—whether used in smart home security systems, automated appliances, or industrial remote-control devices—the optical component must maximize the transmission of specific IR wavelengths while minimizing scattering and absorption.
Achieving high infrared transmission in plastic injection-molded IR optics requires advanced engineering expertise. At ATRMOLD, we specialize in precision mold development, cleanroom injection molding, and advanced surface treatments, providing a true one-stop manufacturing solution for custom infrared optical components.
What Are Infrared Optical Components? Working Principles of PIR Fresnel Lenses & IR Window Sheets
Infrared optical components are among the core functional elements of smart sensing devices. Depending on structural design requirements and installation environments, mainstream IR optical products are generally divided into the following categories:
Molded IR Plastic Lenses
These lenses feature rigid structural support and a thicker substrate base, with high-precision Fresnel microstructures integrated onto the optical surface. Acting as the “eyes” of passive infrared (PIR) sensing systems, they collect and focus weak infrared heat signatures emitted by the human body (typically around 9.6μm) to activate sensors or trigger security alarm systems.
PIR Lens Sheets (Ultra-Thin Flexible Sheets)
PIR lens sheets provide excellent flexibility and can be bent to fit curved device housings. This design supports the growing trend toward slimmer and lighter smart devices while ensuring excellent production consistency and stable high-volume manufacturing performance.
IR-Transmitting Windows / Filter Windows (Flat Sheets)
These windows feature flat, highly polished optical surfaces and are widely used in home appliance remote controls, including televisions and air conditioners, as well as smart home gateways and sensor devices. Typically combined with Infrared Transparent Acrylic Panels, these windows conceal internal sensing components while maintaining a clean exterior appearance. At the same time, they effectively block interference from visible light sources such as sunlight and indoor lighting, significantly reducing false triggering
Common Materials for IR Lens Sheets & Windows: How to Choose Between PMMA, PC, and COC?
The choice of raw material directly affects infrared transmission efficiency, sensing distance, and long-term durability. In many cases, device failures such as sensitivity reduction, yellowing, cracking, or unstable detection are caused by improper material selection.
ATRMOLD provides optimized optical material solutions tailored to different application environments and industry requirements:
PMMA (Specialized IR Acrylic) — Cost-Effective Standard for High-Volume Production
This material complies with international IR-transmitting acrylic standards and delivers up to 92% infrared light transmission within the target wavelength range, along with excellent optical uniformity. It effectively transmits human infrared signals while filtering unwanted visible light interference. Due to its excellent molding properties and precise Fresnel pattern replication capability, PMMA is widely used in smart home devices, LED sensor lighting, and consumer electronics.
PC (Optical Polycarbonate) — Designed for Outdoor & Industrial Applications
Optical-grade polycarbonate offers outstanding mechanical durability for demanding outdoor and industrial environments. Key advantages include high impact resistance, excellent thermal stability, and strong UV aging resistance. In applications such as solar streetlights and outdoor security sensors, PC materials resist yellowing, brittleness, and cracking, maintaining stable sensing performance over long-term use.
COC (Cyclic Olefin Copolymer) — Ultra-Precision Optical Engineering Material
COC is a premium optical engineering plastic designed for ultra-high precision applications. Its near-zero water absorption rate effectively prevents optical focal shifts caused by moisture absorption in humid environments. In addition, COC offers extremely low birefringence and exceptionally high infrared transmittance, delivering optical performance far beyond conventional plastic materials. It is highly recommended for high-end medical devices, precision infrared thermometers, and advanced night-vision systems that demand exceptional sensing accuracy and stability.
Value-Added Surface Treatments:
All of the above materials can be customized with advanced surface enhancement technologies, including 4H anti-scratch hard coating, anti-fog treatment, and Infrared Anti-Reflection (IR-AR) coating to further improve optical performance, abrasion resistance, and environmental durability.
Core Manufacturing Processes & Precision Mold Tolerances
Many standard sensor lens sheets on the market suffer from inconsistent Fresnel ring structures due to insufficient mold precision. This often leads to detection dead zones, unstable sensing performance, and false triggering issues that negatively impact the user experience.
With nearly 20 years of experience in optical mold manufacturing, ATRMOLD utilizes tiered precision manufacturing processes to match different application requirements:
Conventional Precision Injection Molding
Suitable for standard PIR lens sheets, this process provides excellent production consistency and cost efficiency for consumer electronic applications.
SPDT (Single-Point Diamond Turning) Mold Manufacturing
This is ATRMOLD’s core technology for manufacturing high-precision IR optics. Using ultra-precision diamond turning equipment, we directly machine mirror-grade microstructures into mold inserts while controlling mold tolerances within ±0.005mm. This enables micron-level Fresnel focusing accuracy and effectively eliminates signal drift, sensing dead zones, and instability issues commonly found in premium optical devices.
High-Standard Mirror Polishing
Our advanced polishing process removes microscopic scratches, pinholes, and surface defects from the mold cavity. This minimizes infrared light scattering and refraction abnormalities during transmission through the plastic material, maximizing signal clarity and optical accuracy. The process fully complies with SPI A1 mirror polishing standards.
From R&D to Finished Products: ATRMOLD One-Stop Closed-Loop Manufacturing
As a fully integrated manufacturer with in-house R&D and production capabilities, ATRMOLD operates a complete closed-loop manufacturing system covering optical design, mold fabrication, injection molding, surface treatment, inspection, and shipping. This fully controlled workflow ensures consistent product quality for global customers.
Ray-Tracing Simulation
Mold Manufacturing
Cleanroom Molding
IR Coating
Dimensional Inspection
Secure Packaging
Optical Simulation
Before mold machining begins, we simulate the complete optical path using professional optical software based on installation height, sensing distance, and detection angle requirements. This helps optimize detection zones and eliminate potential blind spots during the design stage.
Mold Development
We use premium S136 mirror-grade mold steel to ensure excellent dimensional stability and extended mold lifespan. Under proper maintenance conditions, mold life can exceed 500,000 production cycles while maintaining stable product consistency.
ISO Class 7 Cleanroom Injection Molding
Optical components are extremely sensitive to contamination. Even microscopic dust particles can create serious optical defects. Therefore, all molding operations are performed inside ISO Class 7 cleanroom environments to ensure superior product cleanliness and consistency.
100% Quality Inspection
Using advanced optical interferometers, eccentricity testing systems, and infrared transmission spectrophotometers, we perform comprehensive full-item inspections to ensure that every product delivers reliable sensing performance and stable quality.
Optical Design Optimization for Infrared Sensing Applications
Many infrared sensing products on the market experience issues such as false triggering, delayed response, or insufficient close-range detection. In most cases, these problems originate from improper optical structure design.
Based on years of R&D and mass-production experience, ATRMOLD addresses these challenges through advanced optical optimization techniques:
Optimized Fresnel Pattern Zoning
We divide the sensing area into highly uniform micro-detection zones. As a person moves through the detection area, the sensor receives continuous and stable signal transitions, improving response smoothness and reducing signal lag.
Application-Specific Focal Length Design
Different installation methods require different optical path configurations. For example, wall-mounted motion sensors and ceiling-mounted sensor lights require different focal length designs. We customize focal lengths according to installation conditions to ensure precise infrared energy focusing on the sensor chip.
Integrated Design with IR Pass Panels
We recommend combining device housings with specialized Infrared Transparent Acrylic Panels. This design blocks unwanted visible light interference while allowing effective infrared signals to pass through, significantly reducing false alarms and sensing errors.
Industrial Design Standards & Export Quality Compliance
To support global market access for customer products, all ATRMOLD infrared optical components comply with strict international manufacturing and quality standards:
- Precision Dimensional Control：Finished product tolerances are controlled within ±0.001mm to ensure stable assembly performance and accurate optical alignment during mass production.
- Optical & Environmental Reliability：The deviation between actual sensing angles and theoretical optical design is maintained below 3%. Products undergo rigorous thermal cycling and accelerated aging tests to ensure long-term outdoor reliability without yellowing or material degradation.
- International Compliance：ATRMOLD operates under the ISO9001 Quality Management System. All PMMA, PC, and COC materials comply with international environmental and safety standards, including CE and RoHS requirements, ensuring smooth global export compliance.
Main Application Areas & Industry Compatibility
Whether for new product development, replacement components, or device upgrades, ATRMOLD infrared optical components provide excellent compatibility across multiple industries:
Smart Lighting
Widely used in solar sensor lights, corridor motion lights, integrated outdoor streetlights, and indoor sensor night lights.
Smart Home & Remote-Control Devices
Used in IR remote-control windows for televisions and air conditioners, automatic door sensor systems, smart switches, and video doorbell optical covers.
Security & Surveillance
Applied in wall-mounted PIR motion detectors, burglar alarm systems, and intrusion detection sensor panels to ensure accurate sensing and stable alarm performance.
Industrial Automation
Commonly applied in infrared safety light curtains and automated machinery sensing modules, providing stable and reliable infrared detection for industrial equipment.
Why Choose Us? Take Action Now!
At ATRMOLD, we deliver complete manufacturing solutions from optical ray-tracing simulation to volume precision injection molding.
🌟 Free Project Evaluation: Send us your 2D/3D part drawings or performance specifications. Our team will evaluate the mold tolerances, recommend the optimized optical material (PMMA/PC/COC), and provide a competitive quotation.
👉 Get in touch now to partner with an advanced component factory and achieve high-precision infrared transmission for your smart hardware!