Abstract: Registration in a multi-color printing press is controlled by printing spaced groups of registration marks on a running web, each group comprising a plurality of spaced reference color marks and a plurality of controlled color marks, each being midway between a different pair of reference marks. A computer-based control system produces quantities corresponding to the leading and the trailing edges of each mark, which are averaged to determine the midpoint of the mark, thereby avoiding errors due to differences in reflectance. Registration is determined from other quantities that measure the separations between marks. Data is collected for a predetermined number of successive marks. The collected data is analyzed to determine the start of a group, and the data corresponding to marks of that group is then analyzed to detect registration. After a correction is performed, the system idles until a predetermined length of the web sufficient to enable the effect of the correction to be observed passes the sensor.

Abstract: A series of holes spaced along the length of a running web is sensed optically and corresponding pulses are counted in a first counter to measure a standard length of the web. Simultaneously a running web length measurement is performed by an encoder wheel, which supplies encoder pulses to a second counter that counts down from a preselected number. When the count in the first counter reaches a selected value, the count in the second counter represents deviation of a measured "board length" from the standard, which is displayed digitally. In the event a pulse corresponding to a hole is not produced when it should be, a hole simulation pulse is generated to compensate for the missing pulse.

Abstract: A series of holes spaced along the length of a web is sensed optically and corresponding pulses are counted in a first counter. Simultaneously a running web length measurement is performed by an encoder wheel, which supplies encoder pulses to a second counter that counts down from a preselected number. When the count in the first counter reaches a selected value, the count in the second counter represents deviation of a measured "board length" from a standard, which is displayed digitally. A display indicates whether the deviation from the standard is inside or outside of a selected range and, if outside, indicates whether the measured web length is shorter or longer than a standard length. Hole simulation pulses are generated to compensate for missing hole pulses, and data readout is inhibited if the final count in the first counter is produced by a hole simulation pulse. A strobe inhibit circuit avoids errors when a strobe light is used to inspect the web.