Modulation circuit for grayscale laser printing
US5170403A · kind A · utility
Assignee
Inventor
Key dates
| Filing date | May 31, 1991 |
| Grant date | Dec 8, 1992 |
| Priority date | — |
| Expiry date | May 31, 2011 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH01S5/0427
- WIPO fieldAudio-visual technology
- WIPO sectorElectrical engineering
Abstract
A laser diode modulation circuit for grayscale laser printing provides variable control for both the current through the laser diode and the modulation (switching) of the diode in time. The size of a printed area within a pixel region is determined in two dimensions by the power output of the laser diode and the modulation of the laser diode within the pixel region. The power output of the laser diode is detected with a photodiode detector which is part of a feedback loop for adjusting the maximum bias current value of the diode. The maximum bias current value is held as a digital value with a digital counter, and is adjusted by incrementing or decrementing the counter. A drive current for the laser diode is selected for each pixel as a percentage of the maximum bias current value using an analog multiplexer. A modulation signal is generated in response to modulation information received, and controls the switching of the laser diode within a pixel region.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.