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With the development of LLL night vision technology from the second and third generation to 4G, the specifications of imaging have been significantly improved. In particular, the contrast of imaging, which determines the clarity, even resolution of the image. The contrast of imaging also refers to the Stray Light Crosstalk (SLC) among optical fibers. How to characterize the contrast of Optical Fiber Imaging Elements (OFIE) by detecting the SLC has become an important problem that must be solved. At present, the contrast performance is often characterized by the Knife-edge Response Value (KERV), which is the transmittance value of light passing through the knife edge through optical fiber imaging element. However, KRV has some disadvantages, such as inaccurate measurement value, harsh test conditions, complex sample preparation and great influence on the measurement result. The most important disadvantage is that KRV is an indirect detection, which needs to slice and grind the tested sample, and the slice position often cannot represent the overall contrast performance of the tested OFIE. In this paper, the digital imaging equipment (high-precision CMOS camera + high-resolution microscope) is used to take photo of the end face of the OPIE placed on the black-and-white boundary of the USAF resolution target. The process of light passing through the black-and-white edge provides accurate information for the contrast change. Through the computer analysis and processing of the digital image, the SLC in different positions of the OPIEs is obtained. The SLC can be used to analyze the degree of crosstalk, or contrast. The digital imaging equipment mainly includes light source system, precision transmission system, CCD camera system, software analysis system and control system. The equipment has the advantages of direct detection, simple operation, high precision, good repeatability and reliability, convenient maintenance, and can be used to test and analyze the imaging contrast of all optical fiber imaging elements. It has been proved that the device is effective in detecting the SLC, and completely replaces the KRV method.
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