optical+mark+reconistion

An optical mark reader is used often in modern society such as in exams or a job application sheet or the most popular the lottery with a basic lay out on a piece of paper where the reader scans the sheet so it can quickly and efficiently read a lot more papers than a human can (with fewer errors).

A sheet of optical mark paper is put into the machine and has a light shone on each row in that column, the less light shone back at the reader then that means that the box has been marked and that is done for each row of each column.