Achromatic doublet lens is a kind of glass that can change the direction of light transmission and the relative spectrum of ultraviolet, visible or infrared light. In the narrow sense, achromatic bi-glued lens refers to achromatic bi-glued lens. Achromatic doublet lens can be used to fabricate lenses, prisms, mirrors and windows in optical instruments.
The difference between achromatic doublet lens and other glass is that it is a part of optical system and must satisfy the requirement of optical imaging. Therefore, the determination of the quality of achromatic doublet lenses also contains some special and stricter indicators.
1. Specific optical constants and consistency of optical constants of the same batch of glasses
Each kind of achromatic doublet lens has regular normative refractive index values for different wavelength light, which is the basis for optical planners to plan optical systems. Therefore, the optical constants of achromatic doublet lenses produced by factories must be within the allowable error range of these values, otherwise the imaging quality in practice will be inconsistent with the expected results in planning and the quality of optical instruments will be affected.
The brightness of optical system imaging is proportional to the transparency of glass. The transparency of achromatic doublet lens to a certain wavelength of light is expressed in terms of light absorption coefficient K_ lambda. When light passes through a series of prisms and lenses, some of its energy is lost by the reflection of the interface of the optical parts, while others are absorbed by the medium (glass). Therefore, the primary way to improve the transmittance of an optical system with multiple thin lenses is to reduce the reflection loss of the lens surface, such as coating the antireflective film on the lens surface.