test card
noun [ C ] UK uk/ˈtest ˌkɑːd/ us/ˈtest ˌkɑːrd/ (US test pattern)
测试图案（电视台播放的图片或图案，用于检测或改进图像质量）
a picture or pattern that was broadcast in the past so that the quality of the television picture received could be examined and improved if necessary by using the controls on the equipment