由于制冷探测器焦平面制作工艺的缺陷，使其各部分组分不会完全相同，从而导致焦平面在进行光电转换时各个位置的光电流大小存在差异. 本文以国产640×512中波凝视型制冷热像仪整机研制项目为基础，通过对探测器接收红外辐射并转换为光电流的过程中主要参量与焦平面材料Hg1-xCdxTe中组分x的关系进行分析，推导出探测器焦平面光电流与组分x的关系模型. 在探测器能够正常工作的宽温度范围内利用黑体面源对探测器进行照射，采集各个温度点下探测器输出数据，并对本探测器整体响应特性及单个像素点的响应特性进行分析. 根据影响光电流的最主要的参量变化情况，提出了双指数曲线模型来描述实际响应数据，并通过大量的数据和图表分析，证明了该模型能够提高对探测器实际响应描述的精确程度，对实际的工程应用具有指导意义.

The compositions of each part on the focal plane array (FPA) are not likely the same because of the manufacture defects. The defects will cause the inherent differences between pixels while the focal plane array is conducting the photoelectronic conversion. This paper has derived the theoretical model of the nonlinearity of the cooled detector corresponding to the composition x, which is based on the research project of the domestic 640×512 MWIR cooled thermal imager. The infrared radiation received by the FPA and converted into photocurrent, this type of current has significant relationship with the nonlinearity of the detector according to the composition x in the Hg1-xCdxTe material. A black body was used to radiate the detector under the wide working temperature of the detector, and amount of experimental data were collected under every pre-set temperature point. According to the parameter change that influence the photocurrent most, a double exponential fitting model was proposed to describe the nonlinearity characteristics of both the total response and the separate pixel response of the detector. Multiple works were carried out by analyzing the response data in the form of diagram and table to prove the accuracy of the real response fitting by this model.