Do you know what kind of lens is durable?

Author: Biliten

2025-08-01

Previous articles introduced reflective cup in projector headlamps optical system components. Today we will talk about an equally important optical component: the lens.

The Meaning of Lens

Lens is an optical element made of transparent material (such as glass, resin, etc.), whose surface is usually two spherical surfaces or a spherical surface plus a plane.

The Core Function of the Lens

The essence of the lens is to use the law of refraction of light: when light enters another transparent medium (such as glass) from one transparent medium (such as air), the propagation direction will be deflected, and the curved surface shape of the lens will cause the light incident at different angles to produce regular deflection, ultimately achieving the convergence or divergence of light.

Lens Materials and Characteristics

The lens materials must meet the requirements of transparency, high light transmittance, and stable physical and chemical properties.

Material	Transmittance	High temperature resistance	Impact resistance	Cost
Ordinary optical glass	More than 90%	Good (around 500℃)	Average	Medium
High boron glass	90% or more	Excellent (800℃+)	Good	Medium to high
Quartz glass	90-94% (including UV/IR)	Above 1000℃	Poor (brittle)	High
Polycarbonate (PC)	89-90%	120-130℃	Excellent	Medium-low
PMMA (Acrylic)	About 92%	Poor (<80℃)	Poor	Low
Calcium fluoride (CaF₂) crystals	91-93%	100-120℃	Poor (brittle)	Very high

So, Which material is Suitable for Projector Headlamps?

Currently, polycarbonate (PC) is currently the dominant material in automotive headlights, taillights, etc., for the following reasons:

1. Excellent optical performance

High light transmittance (up to 89%-90%), close to glass, can ensure efficient light output and meet lighting brightness requirements.
Moderate refractive index (about 1.58), easy to design into complex curved structures (such as convex lenses, aspheric lenses), to achieve precise beam control (such as focusing of high beams and cutting lines of low beams)

2. Strong mechanical properties

Excellent impact resistance (more than 250 times that of glass), can withstand vibration during vehicle driving, stone impact and other external forces, not easy to break, and much safer than glass.

Light weight (density is about 1.2g/cm³, only half of glass), which can reduce the weight of the headlight assembly and reduce vehicle energy consumption.

3. Weather resistance and high temperature resistance adaptation

After special treatment (such as surface coating), it can resist ultraviolet aging (avoid yellowing and reduced light transmittance after long-term exposure).

It has good high temperature resistance (thermal deformation temperature is about 130-140℃), and can adapt to the heat dissipation environment of the bulb inside the headlight (such as halogen lamp, LED lamp) (the operating temperature of LED lamp is usually 80-120℃, and the temperature near the halogen lamp is higher, but the lens is at a certain distance from the light source, which PC can withstand).

4. Processing convenience

Easy to injection mold, can mass-produce lenses with complex shapes (such as integrated multi-focal lenses), and reduce manufacturing costs.

Summary

PC material is the best choice for projector headlamps lenses. It combines optical performance, mechanical strength, weather resistance and processability, and is fully adapted to the complex use environment of automobiles. In addition, PC lenses are usually further improved in performance and service life through surface coating (such as anti-ultraviolet coating, wear-resistant coating).

What are the characteristics of different light source technologies for automotive illumination?

Do you know which reflective cup is suitable for automobile lamps?