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Infrared Lens

Infrared lenses are the core components of infrared optical systems, and their material properties directly affect the system's spectral response, imaging quality, and environmental adaptability. The mainstream infrared lens materials currently include germanium (Ge), silicon (Si), and sulfur-based glass, each with its own focus in optical characteristics, physical properties, and application scenarios.

Guojin@settall.com

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Infrared Lens

SSK-HWTJ

Guojin@settall.com

+86 010-63256377

Category:

Other series

Infrared Spherical / Aspherical Lens Series

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1. Germanium ( Germanium, Ge )

Overview
Germanium is a high refractive index infrared optical material, widely used in mid-infrared ( 3–5 µm ) and far-infrared ( 8–12 µm ) optical systems, especially frequently used in infrared thermal imaging, surveillance, temperature measurement instruments, and military optical equipment.

Main Characteristics

Wavelength Range: 2–14 µm , covering mid to far infrared

Refractive Index: n≈4.0 ( @10 µm ), compact imaging system design

Transmittance: high transmittance, coated AR film can reach >98%

Thermal Properties: low thermal expansion ( 6.1×10 ⁻⁶ / ° C ), low temperature drift

Density: relatively high ( 5.33 g/cm³ ), heavier weight

Advantages

High transmittance in the infrared band

Good thermal stability, stable imaging under temperature changes

Processing accuracy can reach λ/10

Disadvantages

Opaque to visible light ( <2 µm )

High density limits miniaturization of devices

Transmittance significantly decreases at high temperatures (above 100°C performance degradation occurs)

Typical Applications
Infrared thermal imaging lenses, seeker lenses, laser rangefinder receivers, surveillance thermal imaging systems

Parameter Introduction Table

Parameter Category	Value / Range	Description
Operating Wavelength Range	2 – 14 µm	Suitable for both mid and far infrared
Refractive Index	4.003 @10 µm	High refractive index, compact design
Transmittance	≥95% (Uncoated) / ≥98% ( AR (Coated)	High infrared transmittance
Density	5.33 g/cm³	Relatively heavy
Thermal Expansion Coefficient	6.1×10 ⁻⁶ / ° C	Good thermal stability
Thermal Conductivity	60 W/(m·K)	Strong heat conduction ability
Mohs Hardness	6.0	Medium hardness
Diameter Processing Range	Ø5 mm – Ø200 mm	Spherical / Aspherical
Thickness Processing Range	1 mm – 25 mm	Depends on aperture and design requirements
Surface Accuracy	λ/4 – λ/10 @632.8 nm	Interferometric Testing Accuracy
Surface Roughness	Ra ≤ 5 nm	High polishing quality
Coating Types	Single-band AR , multi-band AR 、 DLC	Improves transmittance and protection
Temperature Range	-60°C ~ +100°C	Transmittance decreases at high temperatures

2. Chalcogenide Glass ( Chalcogenide Glass )

Overview
Chalcogenide glass is a type of glass mainly composed of sulfur ( S ), selenium ( Se ) Te Infrared optical glass with ） as the main component, for example AMTIR-1 、 IRG series. Its refractive index and transmittance are between germanium and silicon, and it can be processed by low-cost molding methods such as casting and pressing, suitable for mass production of aspheric infrared lenses.

Main Characteristics

Wavelength Range: 0.8–12 µm

Refractive Index: n≈2.4 ( @10 µm )

Transmittance: high transmittance, especially suitable for mid- to long-wave infrared

Density: approximately 4.5 g/cm³ , moderate weight

Processability: can be molded by pressing, suitable for mass production of aspheric lenses

Advantages

Supports multi-band design from visible to infrared

Low-cost mass production of aspheric lenses

Good material uniformity, stable optical performance

Disadvantages

Low mechanical strength, not suitable for high-impact environments

High thermal expansion coefficient (approximately 18×10 ⁻⁶ / ° C )

Sensitive to acidic and alkaline environments, requires surface protective coating

Typical Applications
Handheld infrared thermal imagers, infrared aiming devices, vehicle-mounted thermal imaging cameras, security thermal imaging systems

Parameter Introduction Table

Parameter Category	Value / Range	Description
Operating Wavelength Range	0.8 – 12 µm	Covers visible to long-wave infrared
Refractive Index	~2.4 @10 µm	Medium refractive index
Transmittance	≥95% (Uncoated) / ≥98% ( AR (Coated)	Stable transmittance
Density	~4.5 g/cm³	Moderate weight
Thermal Expansion Coefficient	18×10 ⁻⁶ / ° C	Relatively high thermal expansion
Thermal Conductivity	~0.9 W/(m·K)	Relatively low
Mohs Hardness	2.5 – 3.0	Relatively soft
Diameter Processing Range	Ø5 mm – Ø150 mm	Supports molding by pressing
Thickness Processing Range	1 mm – 20 mm	Mass aspheric processing
Surface Accuracy	λ/4 – λ/8 @632.8 nm	General accuracy
Surface Roughness	Ra ≤ 10 nm	Polished or molded surface
Coating Types	AR , moisture-proof, scratch-resistant	Improved protective performance
Temperature Range	-60°C ~ +200°C	Protective coating can enhance

3. Silicon ( Silicon, Si )

Overview
Silicon is a lightweight, high-hardness infrared optical material, mainly used in 1.2–8 µm band (near-infrared to mid-infrared). It has high mechanical strength and good thermal conductivity, suitable for use in high-temperature and high-impact environments, commonly used in outdoor and military optical systems.

Main Characteristics

Wavelength Range: 1.2–8 µm (best transmittance in mid-wave infrared)

Refractive Index: n≈3.42 ( @4 µm )

Transmittance: high transmittance, especially in 3–5 µm band with excellent performance

Density: 2.33 g/cm³ , lightweight

Mechanical properties: high hardness (Mohs hardness 7 ), high thermal conductivity

Advantages

Lightweight, suitable for lightweight devices

High strength, good scratch resistance

High thermal conductivity, excellent high-temperature resistance (up to +600°C )

Disadvantages

Long-wave infrared ( >8 µm ) transmittance significantly decreases

Requires precision coating to improve anti-reflective performance

High processing hardness, processing cost slightly higher than germanium

Typical Applications
Infrared camera windows, laser scanning systems, infrared detector protective windows, airborne / naval infrared systems

Parameter Introduction Table

Parameter Category	Value / Range	Description
Operating Wavelength Range	1.2 – 8 µm	Near-infrared / Best in mid-infrared
Refractive Index	3.42 @4 µm	Medium-high refractive index
Transmittance	≥90% (Uncoated) / ≥97% ( AR (Coated)	Best performance in mid-wave infrared
Density	2.33 g/cm³	Lightweight material
Thermal Expansion Coefficient	2.6×10 ⁻⁶ / ° C	Extremely low, small temperature drift
Thermal Conductivity	150 W/(m·K)	Excellent thermal conductivity
Mohs Hardness	7.0	High hardness
Diameter Processing Range	Ø5 mm – Ø200 mm	Spherical / Aspherical
Thickness Processing Range	1 mm – 25 mm	Depends on optical design
Surface Accuracy	λ/4 – λ/10 @632.8 nm	High-precision inspection
Surface Roughness	Ra ≤ 5 nm	High polishing quality
Coating Types	AR , multi-band AR 、 DLC	Scratch resistance and protection
Temperature Range	-60°C ~ +600°C	Suitable for high-temperature environments