Abstract: In a register error detection device, an image capturing unit captures an image of two first register marks of a first color printed on a substrate by a first plate cylinder of a rotary printing press and a second register mark of a second color printed on the substrate by a second plate cylinder of the rotary printing press. A calculation unit calculates a register error based on the number of pixels between a reference position located between the two first register marks and a comparison position that is based on the second register mark in the image captured by the image capturing unit.

Abstract: In a control device which controls a printing press, a capturing unit captures an inspection target object printed on a target printed material by the printing press, and outputs RGB values of each pixel of a captured image. The converter specifies a pixel with respectively equal RGB values and a pixel with respectively approximating RGB values as pixels in the grayscale area in the image, and converts the RGB values of each pixel other than the grayscale area into HSV values. An extractor extracts a pixel of an extraction target color from the image based on the RGB values in a case of the pixel in the grayscale area, and the HSV values in a case of the pixel other than the grayscale area. The controller controls the printing press to correct the print misalignment based on the pixels of the extraction target color extracted by the extractor.

Abstract: A register mark detecting apparatus detects a transparent register mark printed on a conveyed transparent web. The register mark detecting apparatus includes a light source, a parallel light flux irradiation optical system, a collective optical system, a knife-edge, and a light receiving element. The parallel light flux irradiation optical system converts a light flux from the light source into a parallel light flux to irradiate a transparent web with the parallel light flux. The collective optical system collects the light flux transmitted through the transparent web. The knife-edge is disposed near a back focus of the collective optical system. The knife-edge interrupts the light flux going straight in the transparent web and causes only the light flux refracted by being transmitted through the transparent register mark to pass by. The light receiving element receives the light flux transmitted through the knife-edge.

Abstract: A register mark detecting apparatus detects a transparent register mark printed on a conveyed transparent web. The register mark detecting apparatus includes a light source, a parallel light flux irradiation optical system, a collective optical system, a knife-edge, and a light receiving element. The parallel light flux irradiation optical system converts a light flux from the light source into a parallel light flux to irradiate a transparent web with the parallel light flux. The collective optical system collects the light flux transmitted through the transparent web. The knife-edge is disposed near a back focus of the collective optical system. The knife-edge interrupts the light flux going straight in the transparent web and causes only the light flux refracted by being transmitted through the transparent register mark to pass by. The light receiving element receives the light flux transmitted through the knife-edge.