From the structure description like picture one, there is a line polarizer installation in the lighting coming out area of LED machine vision light, this way can change the light direction to line polarizer light. When lighting down to the object surface, it will reflect back, if the object material is big difference, then the line polarizer light reflect extend is difference. When we put a circle polarizer in lens, then the brightness of different material will be difference, like below picture two.
The purpose of installation a circle polarizer in lens is to provide the image grabbed failure when the line polarizer light comes into camera.
Application skill: under normal situation, put the lens in the focus position, then adjust the direction of polarizer on the light, this can make easier during adjustment.