Automatic determination of quotient value - particularly exposure time of photo-reproduction systems depending on paper sensitivity and light intensity

摘要

The process and equipment relate to determining automatically a quotient value from two variables and are applicable particularly to exposure time in photoprinting, depending on light intensity and paper sensitivity. The process consists in integrating to a saw-tooth voltage a voltage magnitude proportional to the nominal value of the quotient, comparing it with a voltage magnitude proportional to a counter value of the quotient and measuring the time taken for the saw tooth voltage to reach parity. The time taken is used for control purposes and/or as a standard for the quotient. The equipment has a timing stroke generator with low frequency stroke whose output signal is fed through a gate circuit to a forward-reverse counter. After this has counted back and zero value decoder has responded, the start unit initiating the process is switched off. The forward-reverse counter is then reset by a digital store through a data selector to its initial value.