IMAGE DENSITY TEST CIRCUIT FOR AN ELECTROPHOTOGRAPHIC COPIER

IMAGE DENSITY TEST CIRCUIT FOR AN ELECTROPHOTOGRAPHIC COPIER

An image density test circuit for an electrophotographic copier includes a light source (33) and a sensor (34) for monitoring a test patch (30) produced on the imaging element (26) of the copier. While the bare photoconductor is being sensed an energising circuit sets the light source output to a fi...

Ausführliche Beschreibung

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Bibliographische Detailangaben
1. Verfasser: PRIES, ROBERT WAYNE
Format: Patent
Sprache:eng
Schlagworte:
CINEMATOGRAPHY
ELECTROGRAPHY
ELECTROPHOTOGRAPHY
HOLOGRAPHY
INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIRCHEMICAL OR PHYSICAL PROPERTIES
MAGNETOGRAPHY
MEASURING
PHOTOGRAPHY
PHYSICS
TESTING
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Beschreibung
Zusammenfassung:An image density test circuit for an electrophotographic copier includes a light source (33) and a sensor (34) for monitoring a test patch (30) produced on the imaging element (26) of the copier. While the bare photoconductor is being sensed an energising circuit sets the light source output to a first level and a storage circuit holds the value of the sensor output. When the light beam contacts the leading edge of the patch, the storage circuit is isolated from the sensor and drive circuits (102, 103) switch the energising circuit to drive the light source to a level at which, for a predetermined patch density, the sensor output remains unchanged. The output of the sensor is then compared with the value in the storage circuit by a comparator (121) to provide a first output if the test patch is below the predetermined density or a second output if not.