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New Data Clocking Method for a Laser Printhead

IP.com Disclosure Number: IPCOM000041408D
Original Publication Date: 1984-Jan-01
Included in the Prior Art Database: 2005-Feb-02
Document File: 2 page(s) / 27K

Publishing Venue

IBM

Related People

Castro, F: AUTHOR [+2]

Abstract

Non-impact printers, such as the IBM 6670 and IBM 3800 printers, use a laser printhead to scan the printed image onto a photoconductor surface. The laser signal is modulated on and off by a data clocking circuit which synchronizes the data image to the laser scan. In the printhead this is done by clocking the data with a fixed frequency reference oscillator and also driving the scanning mirror motor from a subfrequency derived from the reference. This fixed frequency system works for printheads where the scanning mirror is directly coupled to the drive motor. In the printhead the scanning mirror is belt driven from a 60-hertz synchronous motor. The data synchronization is obtained from an optical grating system that provides the data clock.

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New Data Clocking Method for a Laser Printhead

Non-impact printers, such as the IBM 6670 and IBM 3800 printers, use a laser printhead to scan the printed image onto a photoconductor surface. The laser signal is modulated on and off by a data clocking circuit which synchronizes the data image to the laser scan. In the printhead this is done by clocking the data with a fixed frequency reference oscillator and also driving the scanning mirror motor from a subfrequency derived from the reference. This fixed frequency system works for printheads where the scanning mirror is directly coupled to the drive motor. In the printhead the scanning mirror is belt driven from a 60-hertz synchronous motor. The data synchronization is obtained from an optical grating system that provides the data clock. The new data clocking method described here eliminates the need for the optical grating in the 6670 printhead without requiring a spindle motor servo system used on the 3800 printhead. In this new data clocking method shown in the figure, a start scan signal is generated from the scanning mirror driven from a 60-hertz line voltage. The mirror is allowed to vary in velocity slightly with the line frequency. Using the AC line to drive the mirror motor eliminates the need for a motor drive amplifier. The data clock signal is obtained by phase-locking a high frequency voltage-controlled oscillator to the rotating mirror. This is done by means of the start pulse or start scan generated...