TRANSMISSION TYPE LIQUID CRYSTAL MASK MARKER

摘要

This invention relates to a transmission type liquid crystal mask marker which can be incorporated easily into an existing apparatus, and which enables printing to be done stably, at a high speed and with a high accuracy, and, moreover, an S/N ratio of a sensor output to be improved. Accordingly, a controller for regulating a voltage applied to a transmission type liquid crystal mask is provided so as to repeat, during the rewriting of a static image for a mark to be displayed on a transmission type liquid crystal mask, the displaying of a static image to be tested and the attaining of an equipotential and the displaying of a static image for a mark and the attaining of an equipotential until the rewriting time is terminated, measure an actual light transmittance of a static image to be tested which is being rewritten, and obtain an optimum light transmittance. An optical filter may be provided on a light transmittance measuring light receiving means.