Adjustable contrast optical target device for test of acquisition of photoelectric theodolite

A new device used to detect the low contrast target acquisition of photoelectric theodolite is designed and its reliability is experimentally demonstrated. The adjustable contrast optical target device, which can simulate the sky background luminance and a low contrast target, is established. It utilizes a big integrating sphere and a small one to simulate the luminance of the background and target respectively. Importantly, by controlling the luminous flux of the two integrating spheres, the targets and background radiance can be continuously adjustable under the condition of constant color temperature. Thus, the contrast can be controlled continuously in the range of 0%–90% and its stability is better than 1%. The biggest background luminance exceeds 60 W m -2 str -1 in the spectral range of 400–800 nm.