1, computer scanning marking, using optical character recognition (OMR) technology, is based on the concentration of carbon or graphite in the pencil and the size of the blackened area.
2. When scanning the test paper, scanning parameters are set, including the filling gray value and filling ratio. The filled gray value is the color depth when drawing the answer sheet. The scanning system will have relevant parameters to fully consider the occurrence of various filling conditions, so don't worry.
Computer scanning principle:
1, pencil lead is made of graphite, lead and clay. Machine-readable card adopts optical identification system, and uses X-ray real-time imaging monitoring system software, defect and picture database management system software and special image processing software to identify students' answers.
2. Set a certain number of small X-ray probes at fixed positions as model holes for standard answers. HB is a pencil with medium hardness and plenty of graphite, so X-rays can't pass through the graphite. It must be filled with a pencil to cause the shadow of X-rays, and the answers on the machine-readable card can be reflected. This principle is caused by the difference of X-ray penetrating matter.