The principle of machine-reading of answering card
The working principle of the cursor reader is to enter the relevant information through the identification of the information by the photoelectric head of the machine, automatically judge the correctness and error, and collect the valid information filled in to the computer, and analyze the information through the special software of the reader to obtain valid data
A simple optical character recognition (OCR) technology
The cursor reader is only sensitive to black, so the red and green parts of the cursor reader on the answer sheet are actually not recognizable. The answer card was originally printed with a black bar to help the cursor reader confirm the direction and position of the answer card. The black block filled with pencil and the printed black block together form a black and white image. The principle is similar to the binary "0" "1". After scanning with the cursor reader, the image generated by the pre-stored answer is compared. The part that matches is the score, and the part that does not match is the error.
In fact, today's home scanners can also do these and can do better. For example, scanning newspaper articles into a computer to form a real text encoding. Of course, the accuracy rate is not as accurate as the cursor reader. Only the "wrong and right" recognition. The rate is high.
There is a black and white road on the side, see it, call the reader synchronization frame.
Then use the photoelectric element to measure the luminous flux, and then through digital processing, you can get the score. This is fast and accurate. Process 3-5 pieces of information every second.
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