| 摘要 |
PROBLEM TO BE SOLVED: To provide a level difference measuring method which can measure the level difference on a board accurately without damaging the board. SOLUTION: A beam of light 11 is put incident at an incident angleϕon level difference sensing marks 10a and 10b which are made of a material having a high reflection factor and installed on the upper level difference part 10a and lower level difference part 10b, respectively. Measurement is made for the difference d1 between the positions where the reflected beams of light 11a and 11b of the beam 11 reflected by the two marks 10a and 10b are put incident on a light sensor 14 installed above a board 10, and from the measurements the height (d) of the level difference 10c is found.
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