Measuring of the photoelectric parameters of the IR arrays is the important stage in manufacturing of the IR thermovision camera photoreceivers. This work is directed toward the novel construction of the optical part (cold camera) of the testing unit (TU) for measuring of the IR arrays input/output photoelectric parameters in the process of the industrial production. This device can measure such parameters as sensitivity, NEI, NETD, saturation voltage, their array's field uniformity, etc. The TU's cold camera consists of the cold head, the cold shield, the new cold diaphragm, the cold filter (if needed) and the gray or black body (BB) with the plane emitting surface. All this parts placed in the small size vacuum cryostat without any windows. In our case it is the vacuum cryostat with the close cryogenic system produced by CTIcryogenics. The distance between FPA's plane and the diaphragm is 15.0 mm, and between the diaphragm and the emitting surface of BB is 10.0 mm. The diameter of the emitting surface is 50 mm. The temperature change needed for the characteristics measurements is 5 - 45 degrees Celsius. The cold diaphragm has the shape of annular slot so that the irradiance in FPA's plane is very uniform (better than 0.5% for (Delta) T(x,y) less than 0.5 degrees Celsius and 1 ring). These factors indicate on the measurement correctness. The outside diameter of the diaphragm is in accordance with the array's place and the BB emitting surface diameter so that only emitting surface points would be viewed from the array's place. Parameters of the diaphragm define the set background illumination value and the irradiance uniformity. The temperatures of the measured IR array and the cold shield (with diaphragm and filter) are set in accordance with their temperature requirements to the array and the background.