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REFLECTOR/TRANSMITTER TO AID IN LAMP WARMUP AND PHOTORECEPTOR LAMP CONFIGURATION

IP.com Disclosure Number: IPCOM000024076D
Original Publication Date: 1979-Aug-31
Included in the Prior Art Database: 2004-Apr-02
Document File: 4 page(s) / 754K

Publishing Venue

Xerox Disclosure Journal

Abstract

In many respects, low pressure sodium vapor lamps are a near optimum illumination source for photocopiers producing black..and.-whiteoutput copies from black..and.. white and multicolored originals. With respect to line copy, the goal of any black..and-whitephotocopier is to make the image areas on the copy as black as possible while making the copy background

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XEROX DISCLOSURE JOURNAL

REFLECTOR/TRANSMITTER TO AID IN LAMP WARMUP AND PHOTORECEPTOR LAMP CONFIGURATION
3. Durbin 3, 0. Rees

IMAGE OF EXPOSURE SLIT

Proposed Classification
U.S. Cl. 355/3 R

mt. CI, G03g 15/00

I \ PLATEN

  SPECULAR REFLECTOR

PHOSPHOR

  DIFFUSE REFLECTOR

FIG. I FIG. 2

FIG. 3 FIG. 4

Volume 4 Number 4 July/August 1979 507

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REFLECTOR/TRANSMITTER TO AID IN LAMP WARMUP AND PHOTORECEPTOR

In many respects, low pressure sodium vapor lamps are a near optimum illumination source for photocopiers producing black..and.~whiteoutput copies from black..and.. white and multicolored originals.

With respect to line copy, the goal of any black..and~whitephotocopier is to make the image areas on the copy as black as possible while making the copy background

as white as possible. In other words, one would like a minimum of energy reflected for the image areas of the original while reflecting a maximum from the background region. Clearly, of course, it is impossible to copy all colored backgrounds as white while concurrently copying all colored images as black.

Most colors that are used as images tend to be located at the extremes of the visible spectrum, blues and reds. Yellow is seldom used for images, Colored backgrounds are pastel (desaturated) and can usually be considered as tinted white paper. The above can be explained in part on wefl-known principles of physiological optics (photopic vision).

It then follows that the optimum light source for a black-and~.whitephotocopier is yellow. Blues and reds will copy as black while concurrently most common colored papers have considerable reflectance in the yellow. It should be noted that the use of yellow exposure lamps obviously necessitate a yellow sensitive photoreceptor.

Low pressure sodium lamps represent a commercially available yellow light source. It is important to point out that the preceding discussion holds for all photocopying and includes, but is not limited to, the xerographic process.

Low pressure sodium vapor lamps are nearly monochromatically yellow and optimize the copyability of the preponderance of common colored images, the blues and reds, Present commerical sodium lamps have several disadvantages for photocopying applications,

The principal problem is the long warmup period required. Sodium lamps must reach an operating temperature of 260°C for optimum efficiency, far higher than that required for fluorescents. Consequently, whereas unassisted fluorescents require only a matter of seconds to reach peak radiance, unassisted sodium lamps require several minutes. As such, this situation presently eliminates sodium lamps from the well~.known,on/off operation used in most photocopiers. In addition, like many gas discharge lamps, hot restrike of the lamps may be difficult.

Efficiency is maximized when heat (infrared energy) is not allowed to escape from the lamp. This can be accomplished by surrounding the arc...