ZnS Plano-Convex Lenses

Overview

ZnS plano-convex lenses are positive focal length spherical lenses made from zinc sulfide optical material. One surface is flat and the other surface is convex, allowing the lens to focus collimated infrared radiation or collimate radiation from a point source.

Zinc sulfide, especially CVD ZnS optical material, is valued for its combination of infrared transmission, mechanical strength, thermal stability, and environmental durability. It is widely used in infrared lenses, windows, protective optics, thermal imaging systems, sensing modules, and rugged optical assemblies.

Why Choose ZnS for Infrared Lenses

ZnS is often selected when an infrared optical system requires better mechanical durability than softer infrared materials while maintaining useful transmission in MWIR and LWIR regions. For exposed or rugged systems, ZnS may provide a better balance between transmission and durability than a material chosen by transmission alone.

Quick Specifications

Parameter	Guidance
Material	Zinc Sulfide (ZnS), CVD polycrystalline grade available
Lens Type	Plano-convex spherical lens
Typical Working Bands	MWIR, LWIR, and selected broadband infrared applications depending on material grade and coating
Typical Transmission Range	Approximately 0.4-12 µm for suitable grades; practical working band depends on grade and coating
Refractive Index	Approximately 2.192 at 10.6 µm
Typical Size Range	5-400 mm; custom sizes available on request
Coating	Double-side AR coating for specified infrared bands

Material Reference Values

Property	Typical Value
Density	4.09 g/cm3
Knoop Hardness	Approximately 230 HK
Thermal Expansion Coefficient	Approximately 6.5 × 10-6/K
Thermal Conductivity	Approximately 19.2 W/(m·K)
Temperature Coefficient of Refractive Index	Approximately 4.3 × 10-5/K
Surface Figure	Up to λ/10 at 10.6 µm available depending on size and specification

Typical Applications

• Thermal imaging systems and MWIR/LWIR optical paths
• Infrared sensing modules and signal collection optics
• Rugged IR optical assemblies exposed to vibration, shock, or harsh environments
• Airborne and ground-based IR systems
• Protective infrared optics, windows, domes, and covers
• Custom sensing, monitoring, inspection, and analytical instruments

Engineering Notes

ZnS and ZnSe are different infrared materials. ZnSe is often reviewed first for CO2 laser transmission optics and high IR transmission in protected optical paths, while ZnS is often selected when hardness, mechanical durability, and environmental resistance are more important.

To specify a ZnS PCX lens, provide diameter, focal length, center thickness, wavelength band, coating band, surface quality, surface figure, clear aperture, operating temperature, environmental exposure, and quantity. For related material comparison, review ZnSe vs ZnS material selection or send drawings through the contact form.