| 摘要 |
PURPOSE:To assuredly detect the final point of etching a masking plate, by detecting the final point of etching on the basis of the ratio of the quantity of irradiation light regularly reflected from the masking plate to that of irregularly reflected light. CONSTITUTION:A masking plate 2 is rotated in a unitary body by rotation of a spinner 1, and an etching solution is sprayed through a nozzle 8 to etch a chromium film 2b on the surface of the plate 2 into a desired pattern. Light is irradiated onto the plate 2 from a light irradiation part 9 at the same time when etching is started. Light IR' reflected from the surface of the film 2b is received by the first light receiver 13 to detect its quantity. Light IS' reflected from a side surface 2c is irregularly reflected along various directions because the side surface 2c is in a rugged state and partially received by the second light receiver 16 to detect its quantity. The ratio IS/IR of the two light quantities is calculated by an operation circuit 17. When the ratio comes in the error range of the reference signal of a reference signal source 19, a comparing circuit 18 detects the final point of etching, so that a control circuit 5 closes the nozzle 8 through a nozzle closing and opening circuit 4. |
