Method for measuring back vertex power of lens

Abstract

The invention provides a method for measuring back vertex power of a lens. A measurement device comprises a light source, a target reticle, a collimator objective and a telescope. An afocal target is generated by means of the collimator objective through the target reticle illuminated by the light source, the to-be-tested lens is arranged between the collimator objective and the telescope, an image space reticle is adjusted so that a clear image of the target reticle is obtained in the telescope, and the back vertex power phi is obtained in a calculating mode through a formula. According to the method, what is measured is the back vertex power in principle, approximation does not exist, the target is arranged to be afocal in the method that the collimator objective is additionally arranged, an instrument measurement device is shortened, integration is achieved, and accordingly an instrument occupies little space, daily maintenance, detection and calibration are facilitated. Due to the fact that the focal length of the telescope is long enough, the measurement accuracy is greatly improved. The vertex power and the moving distance of the image space reticle are in a linear relationship, and accordingly the moving distance is shorter when the same measurement accuracy of the measurement device needs to be reached. The length measurement can be achieved through a mechanical rule, and cost of the instrument is reduced.

Description

technical field [0001] The invention relates to a method for measuring an optical lens, in particular to a method and a device for measuring the small back vertex of an optical lens. Background technique [0002] The Back vertex power is the reciprocal of the paraxial back vertex of the lens measured in meters. The unit is the reciprocal of the meter (m-1). The distance from the rear vertex of the lens to the paraxial back focus is called the paraxial back focal length, such as figure 1 As shown, where F—object focal point; F′—image focal point; H—object principal point; H′—image principal point; f—object focal length; f′—image focal length; l f — Paraxial front top focal length; l f ′—paraxial back focal length. A lens contains two vertex powers, front and back. According to ophthalmic optics agreement, the vertex power of the lens refers to the back vertex power. [0003] Sunglasses, protective glasses and plano glasses belong to the small vertex power spectacle lens...

AI Technical Summary

Problems solved by technology

[0008] 2) The principle of this measurement is to place the target reticle at a position of 4.6 meters, which makes the instrument measurement device too large and takes up too much space

Measurement accuracy cannot be guaranteed

The linear relationship means that the measurement accuracy corresponding to the moving length of the same reticle is the same, and the non-linear relationship means that the measurement accuracy corresponding to the moving length of the same reticle is different in different positions. In order to ensure the accuracy, more dense The non-linear section of , this will waste a lesser section of the trip

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