Do you know the telecentricity of a telecentric lens?

   The telecentricity of a telecentric lens describes the angle at which the chief ray deviates from the optical axis. The smaller the angle, the better the telecentricity, and the more accurate the image. The telecentricity target is used to measure telecentricity. During the test, the test target plate is placed at 45° to the optical axis, so that the bottom and top of the target plate are at different distances from the lens. When imaging through a non-telecentric lens, the image size at the bottom of the target plate will be smaller than the image size at the top. This is trapezoidal distortion. A perfectly telecentric lens has no keystone distortion and has a telecentricity of 0°.