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Copy Density Calibration

IP.com Disclosure Number: IPCOM000048519D
Original Publication Date: 1982-Feb-01
Included in the Prior Art Database: 2005-Feb-08
Document File: 2 page(s) / 60K

Publishing Venue

IBM

Related People

Champion, JR: AUTHOR [+3]

Abstract

A test circuit simulates a photoconductor surface permitting rapid calibration of surface reflectance detection circuits.

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Copy Density Calibration

A test circuit simulates a photoconductor surface permitting rapid calibration of surface reflectance detection circuits.

The reflectance of a patch on a copier's photoconductor surface indicates toner mix quality. In Fig. 1, a light-emitting diode LED1 illuminates the patch to cause an output from sensor circuits connected to a photosensitive diode PD1 exposed to the patch. The accuracy with which the output indicates toner quality depends upon the illumination intensity set by external control 1, the diode PD1 sensitivity and the calibrated surface reflectance. In production, one circuit card carries PD1 and LED1, but the characteristics of LED1 and PD1 will differ from card to card. Therefore, card testing, in addition to normal calibration, must accommodate the particular card under test. Automatic matching before testing eliminates the possibility of a card passing on one tester and failing on another.

In Fig. 2, an LED/photodiode pair, LED2 and PD2, test another LED/photodiode pair, LED1 and PD1, by simulating the photoconductor surface. LED2 illuminates PD1, and PD2 senses the light output from LED1.

To calibrate the test system, LED2 is placed opposite PD2 and the system is adjusted so that when two digital-to-analog converters, DAC1 and DAC2, receive the same eight-bit control word from a microprocessor, equal voltages emerge. LED2's constant current source is controlled by DAC2, the voltage output of PD2 is converted to digital...