Transmission type liquid crystal mask marker
US5663826A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Apr 1, 1996 |
| Grant date | Sep 2, 1997 |
| Priority date | — |
| Expiry date | Apr 1, 2016 |
Classification
- Technology area (CPC B)Performing Operations; Transporting
- CPC primaryB23K26/066
- WIPO fieldMachine tools
- WIPO sectorMechanical engineering
Abstract
The present invention relates to a transmission type liquid crystal mask marker which can be incorporated easily into a conventional apparatus, and which enables high-speed and high-accuracy stable printing and an increase in the S/N ratio of a sensor output. The transmission type liquid crystal mask marker thus includes a controller for, during rewriting a static marking image displayed on a transmission type liquid crystal mask, displaying a static test image and attaining an equipotential state, and thereafter repeatedly displaying the static marking image and attaining an equipotential state up to the end of the rewriting time, measuring an actual light transmittance of the static test image during rewriting, and regulating the voltage applied to the transmission type liquid crystal mask so that the actual light transmittance is equal to the optimum light transmittance. An optical filter can be provided on a light receiving device for measuring a light transmittance.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.