| 摘要 |
PURPOSE:To enable detection of a printing error in a printed matter in a manner similar to detection by the naked eyes, by using a white light source as a light source, subjecting the reflected light to color separation, and discriminating the printing error for each of the separated colors. CONSTITUTION:A light source 20 is preferably an intense white light source such as a halogen lamp and a xenon lamp. The light reflected from a printed surface is separated into three colors by filters, and light receiving optical fibers 23 are arranged to provide one or a set of several fibers for each of the colors. When light-projecting optical fibers 21, 22 are used and the light source is located on the outside of and remotely from a casing 1, thermal effect of the light source on a substrate 25, a light-receiving sensor element 18, light- emitting lenses 11, 12, a light-receiving lens 13 or the like can be reduced. Electrical signals previously amplified by the substrate 25 are used as reference values by a controller 29, digital electrical signals obtained from a multiplicity of corresponding measurement points on another printed surface are compared with the reference values, and when the difference therebetween exceeds an allowance set point, the relevant measurement point is judged as an error point, and a printing error is detected based on the percent defective. |
