A high-resolution autocollimation range extension method based on an array of off-axis light sources

In autocollimation technology, due to limitations in the aperture of the collimating objective and the size of the sensor, high-resolution angular measurements at the nanoradians level are typically achievable only within a narrow range of a few milliradians. To alleviate this contradiction, an autocollimation model of an off-axis light source was developed to analyse the effect of light source off-axis on the range. It was found that when there is an off-axis amount of the light source, the autocollimation measurements have a non-zero initial value and the range is shifted. An off-axis light source autocollimation system is constituted using the same light source irradiating the array slit diaphragm, and the extension is achieved by range shifting and splicing. Simulation analysis and experimental results verify the feasibility of the method. For the 2 m long focal length autocollimation system, the range is extended from 1375.080″ to 1555.189″, which is 1.13 times of the original one, under the condition of 9 slits and 400 μm period. The results show that the method effectively extends the range of the long-focus high-resolution autocollimation system to a certain extent, and alleviate the contradiction between the resolution and the range.