Mar. 1999 © TOSHIBA TEC
7 - 13
6570/5570 SCANNER
7.6
Outline of Control
7.6.1
Photo-voltaic conversion
The purpose of photo-voltaic conversion is to form electrical signals corresponding to the intensity of light
reflected from the original. A CCD is used for photo-voltaic conversion. CCDs are single-chip photo-
voltaic conversion device in which several thousands of photosensing elements several microns square
are arranged in a single line. This copier uses a CCD having 7,500 of these photosensing elements.
The photosensor comprises a P-layer, N-layer semiconductor. Optical energy generates a (–) (minus)
charge on the P-layer proportional to the optical energy and irradiation time. The charge generated at the
photosensor is transferred to the transfer area, shifted from center to right and left in the figure below
according to the transfer clock, and is output from the CCD. During this operation, in order to increase the
image transmission speed from CCD, even-numbered and odd-numbered image signals are separated
into left and right signals, and 4 channels are output in parallel.
Fig. 7.6-1 Principle of CCD Photo-Voltaic Conversion
Transfer area
Photosensor area
Transfer area
Shift register
Transfer block
Transfer clock
Optical energy
P-layer
N-layer
Detailed photosensor
7.6.2
Shading compensation
The following problems affect the voltage values obtained by photo-voltaic conversion by the CCD:
1
Variation in light distribution from the light source.
2
Light intensities vary at the CCD elements. The elements farthest from the center do not receive as
much light as those elements in the center of the CCD.
3
The photo-voltaic capacities of each of the 7,500 CCD elements are uneven.
Consequently, these problems must be compensated. This is called “shading compensation.” Shad-
ing compensation involves normalizing optical energy according to the following equation based on
already known scanned black data and white data, and compensating for uneven illuminance of the
image data and device unevenness.
(S – K)
I = k
×
—————
(W – K)
where,
k:
Coefficient
S:
Image data before compensation
K:
Black data (in black memory)
W:
White data (in white memory)
1
7497 7498
7499 7500
2
3
4
Содержание 4580
Страница 1: ...SERVICE MANUAL DIGITAL PLAIN PAPER COPIER 8070 6570 5570 4580 ...
Страница 231: ...6570 5570 DEVELOPER UNIT 12 28 Mar 1999 TOSHIBA TEC 3 Draw out the toner filter ...
Страница 252: ...8070 6570 5570 4580 FUSER UNIT 14 6A Mar 1999 TOSHIBA TEC ...
Страница 369: ...8070 6570 5570 4580 ADF 16 78 Mar 2000 TOSHIBA TEC 16 13 PC Board 1 PWA F LGC 794 ...
Страница 370: ...Mar 2000 TOSHIBA TEC 16 79 8070 6570 5570 4580 ADF 2 PWA F SEN 794 ...
Страница 374: ...Mar 1999 TOSHIBA TEC 18 1 6570 5570 PC BOARD 18 PC BOARD 1 PWA F SYS 300 ...
Страница 375: ...6570 5570 PC BOARD 18 2 Mar 1999 TOSHIBA TEC 2 PWA F MTB 300 ...
Страница 376: ...Mar 1999 TOSHIBA TEC 18 3 6570 5570 PC BOARD 3 PWA F LGC 300 ...
Страница 377: ...6570 5570 PC BOARD 18 4 Mar 1999 TOSHIBA TEC 5 PWA F MOT 300 4 PWA F ADU 300 ...
Страница 378: ...Mar 1999 TOSHIBA TEC 18 5 6570 5570 PC BOARD 6 PWA F SLG 300 7 PWA F SDV 300 ...
Страница 379: ...6570 5570 PC BOARD 18 6 Mar 1999 TOSHIBA TEC 8 PWA F PLG 300 ...