| 摘要 |
PURPOSE:To correctly recognize the position of a register mark on printing paper by distinguishing the register mark from others by a method wherein the amount of light reflected from the register mark is distinguished from others based on the difference between the amount of reflected light and the amount of transmitted light or on the ratio of the former to the latter. CONSTITUTION:Light is cast on a register mark on printing paper 11, the position of the register mark is recognized based on amount of light reflected therefrom, and a slippage in the printing is detected by comparison made between the recognized position and a predetermined reference position. Light is cast on the surface of register mark LX, LY on printing paper 11, and the amount of light reflected therefrom is measured. Then, light is cast from the opposite side of the printing surface, and the amount of light transmitted through the printing paper is measured. The light reflected from the register mark LX, LY is distinguished from others, based on the difference between the amount of reflected light and the amount of transmitted light, or the ratio of former to the latter. |
