在光电跟踪测量设备对低对比度目标捕获能力检验中，提出一种利用可调对比度光学无穷远目标源检验的新方法。采用这种方法需建立可调对比度光学无穷远目标源装置，介绍这种装置的设计依据和设计过程。该装置可以模拟天空背景的辐亮度及这个背景下的一个低对比度目标，它利用大、小两个积分球分别模拟背景与目标的辐亮度，利用安装在大积分球上的准直物镜使目标及背景成为无穷远的目标源，在积分球上分别安装内置和外置照明光源，外置照明光源中装有光束准直系统，使卤素灯发出的光束成为平行光后射入积分球内，利用可调光栏控制通光口径的大小，从而控制了进入积分球的光通量，使得背景与目标的辐亮度在色温不变的条件下连续可调，实现目标对比度连续变化，变化范围0～90%，对比度稳定精度优于1%，光谱范围400nm～800nm内最大背景辐亮度优于60W/m2sr。

For the low contrast target acquisition test of the electro-optical equipment, a new method is proposed by using a contrast adjustable infinite distance target. The design of a contrast gradient adjustable optics infinite distance target device is introduced. This equipment may simulate the sky background luminance and a weak target in this background. It uses two integration spheres to simulate the background and target brightness independently. The collimating lens is installed in background integration sphere, target and its background become an infinite source. There were inner and outer light sources for integration sphere illumination. In the outer light source, a collimator was installed. It made parallel beam incident into the integration sphere. The size of the incident parallel beam was controlled by using diaphragm adjusting lever. This method didn’t change color temperature, but luminance could be different. So background and target luminance became continuously adjustable under color temperature unchanged. The target contrast could change continuously, the range of variation is 0～90%, the contrast stability is better than 1%, the biggest background luminance exceeds 60W/m2sr.