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# The Central Principle of Optical Cemented Lenses

In the process of optically cemented lenses, no matter whether the resin glue method or the photo glue method is used, it must be centered to ensure that the optical axes of the positive and negative lenses coincide, otherwise it will affect the image quality of the optical system.

When the parallel light passes through the uncentered lens group, its focal point image F1 'will be violated to the point of F2'. Several axes coincide.) Rotate the positive lens, and the image point F2 'also rotates accordingly. Its limit orientation is the intermediate principle of F3 'glue setting as shown in Figure 8-5. The distance F2'F3 'between the two extreme azimuths of the image point is equivalent to twice the central error of the lens.

F1 ', F2', and F3 'coincide when glued in the middle. Therefore, before the adhesive layer on the cemented surface is cured, the positive lens is advanced with the optical axis of the negative lens as the criterion, so that the optical axes of the positive and negative lenses coincide. At this time, the image point F2 'is not beating or the beating amount (F2'F3') is within the allowable scale.

The optical axis of the centered and edging lens is originally coincident with the geometric axis. Place the cemented lens on the leveling table (the surface that is in contact with the table must be convex or flat) When the colloidal agent is in a liquid state, the center of gravity of the lens and its optical axis is automatically repositioned by the self-weight of the parts. The way to place the lens is to adjust the level with a 30 "spirit level, and the surface accuracy of the way needs to be N = 3, N = 0.5, or more. This centering method can be used for glued parts with center error C> = 0.05mm.

## How to judge whether the achromatic cemented double lens is good?

Optical cemented lens refers to glass that can change the direction of light transmission and can change the relative spectral spread of ultraviolet, visible, or infrared light. The narrow sense of optical cemented mirror refers to the colorless optical cemented mirror; an optical cemented mirror can be used to make lenses, prisms, mirrors, and windows in optical instruments.

The achromatic cemented triple-lens is different from other glasses in that it has some components as an optical system and must meet the requirements of optical imaging. Therefore, the determination of the quality of optical achromatic coated lens also contains some special and severe indicators.

## 1. Specific optical constants and consistency of the same batch of glass optical constants

Each variety of flint glass cemented achromatic cylindrical lens has a regular standard refractive index value for different wavelengths of light, which is used as the basis for optical planners to plan optical systems. Therefore, the optical constants of the optical cemented lenses produced by the factory must be within the certain tolerance range of these values, otherwise, the quality of the actual imaging quality will be inconsistent with the results expected during the planning and affect the quality of the optical instrument.

Flint Glass Cemented Cylindrical Lens

## Second, a high degree of transparency

The brightness of the imaging of the optical system is proportional to the transparency of the glass. The transparency of the optical cemented mirror to a certain wavelength is expressed by the light absorption coefficient Kλ. After the light passes through a series of prisms and lenses, some of its energy is lost at the interface reflection of the optical components and some is absorbed by the medium (glass) itself. Therefore, regarding the optical system including multiple thin lenses, the primary way to improve the transmittance is to reduce the reflection loss of the lens surface, such as coating the surface antireflection coating.

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