Fresnel Lens: Diameter 20-100 mm, Focal Length 10-50 mm

Q: Why use a Fresnel lens instead of a regular lens in motion sensors?

Fresnel lenses are thinner, lighter, and cheaper to mass-produce while providing adequate optical performance for IR detection. Their segmented design allows precise control of detection zones, reducing false alarms from environmental factors.

Q: How does the lens material affect motion sensor performance?

Material choice impacts durability, optical clarity, and environmental resistance. Polycarbonate offers impact resistance, PMMA provides better transparency, and COC ensures stability in humid conditions, all critical for long-term reliability in varied installations.

Component Specifications

Definition

A Fresnel lens is a compact optical component consisting of a series of concentric annular sections, each with a slight curvature, designed to replicate the light-bending properties of a conventional convex lens while significantly reducing thickness and weight. In motion sensors, it precisely directs infrared radiation from the detection zone onto a pyroelectric sensor, enhancing sensitivity and range while minimizing false triggers from ambient thermal noise.

Working Principle

Operates on the principle of diffraction and refraction: the concentric grooves act as individual prismatic rings that bend incoming infrared light waves, focusing them onto a single point (the sensor). This creates a segmented detection pattern (often multiple zones) that detects changes in infrared radiation caused by moving heat sources (e.g., humans), triggering the sensor output.

Materials

Typically injection-molded from optical-grade polymers: Polycarbonate (PC) for durability and high refractive index, Polymethyl Methacrylate (PMMA) for clarity and UV resistance, or Cyclic Olefin Copolymer (COC) for low moisture absorption. May include anti-reflective coatings (e.g., magnesium fluoride) to reduce light loss.

Technical Parameters

Parameter	Typical range	Notes & selection driver
Diameter	20-100 mm
Focal Length	10-50 mm
Groove Pitch	0.1-1.0 mm
Field Of View	90° to 180° horizontal, 10° to 60° vertical
Operating Temperature	-40°C to +85°C
Transmission Efficiency	>85% in 8-14 μm IR range

Ranges are indicative industry figures for RFQ preparation, not a supplier commitment. Confirm every value and standard with the legal manufacturer before ordering.

Standards

ISO 10110-5, ISO 9022-1, DIN 3140

Parent Products

This component is used in the following industrial products

Motion Sensor

This motion sensor is a component designed for integration into outdoor solar bollards.

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Engineering Analysis

Risks & Mitigation

Scratches or dust accumulation reducing transmission
Thermal expansion causing focal shift
UV degradation of polymer materials
Misalignment during assembly leading to blind spots

FMEA Triads

Trigger: Injection molding defects (e.g., sink marks, flash)
Failure: Reduced optical clarity and uneven focusing, causing decreased sensor range or false negatives
Mitigation: Implement strict process controls (mold temperature, pressure) and 100% optical inspection with automated vision systems

Trigger: Environmental exposure (UV, moisture, temperature cycles)
Failure: Material yellowing or warping, leading to permanent loss of detection accuracy
Mitigation: Use UV-stabilized polymers (e.g., PMMA with additives), conformal coatings, and design for thermal expansion compensation

Trigger: Mechanical stress during installation or cleaning
Failure: Cracking or groove damage, resulting in complete sensor failure
Mitigation: Design with reinforced mounting points, provide clear handling guidelines, and use scratch-resistant coatings

Industrial Ecosystem

Compatible With

Typical Suppliers & Equivalents

Compliance & Inspection

Tolerance

Focal length tolerance ±5%, dimensional tolerance ±0.2 mm per ISO 2768-m, optical surface roughness < 0.05 μm Ra

Test Method

IR transmission testing per ISO 13696, environmental cycling per IEC 60068-2-1/2/14, mechanical shock testing per IEC 60068-2-27

Procurement Evaluation Criteria

A practical evidence checklist for RFQ preparation and supplier evaluation.

Technical documentation

Request current drawings, revision history, and a signed specification sheet.

Manufacturing capability

Verify equipment lists, process limits, capacity, and representative production evidence.

Inspection readiness

Confirm test methods, calibrated equipment, sampling plans, and traceable reports.

Supplier transparency

Check the legal entity, factory address, ownership, certifications, and direct contacts.

CNFX does not score or rank suppliers. Buyers must verify all claims and documents with the legal manufacturer before ordering.

Manufacturers of Fresnel Lens

5 companies list this product among what they make. Company figures are quoted from each company's own website; every card states where the relationship came from.

DG Optoelectronics

Jiangsu, CN