Xerox WorkCentre XK50cx, Service Manual

Page: 38 / 109

4-11
Circuit
IMAGE PROCESSING
(1) Image signal input: CCD output signals are offset
at 0.7V with about 2V white level. Optimum input
level of DUOIP2 is 0.7V offset and 2V white
level. So OP AMP is used to design
interface circuit of DUOIP2.
(2) Image processing : The scanner reads pixel data
value of image sensor CCD Charge Coupled
Device 600dpi lines by 600dpi lines. For mono
copy mode, two kinds of algorithms are used.
One is TIP algorithm for Fast copy and normal,
the other is Error diffusion algorithm for Best
copy.
For color copy mode, Samsung color halftoning
algorithm is used for all modes. The color
correction and conversion into CMY print data
are certainly processed for improving image
guality.
The external SRAM (1Mbit, 15ns) is used for
only color halftoning process, and the other
processing parameters are handled using
internal SRAM. Also another external SRAM
(1Mbit-15ns)is used for LGC (Line gap
correction) of CCD Module.
KEY FEATURES
(1) Target Product : Color Fax/Inkjet Digital Color
Copier.
(2) Packeg & Technology : 0.35µ CMOS Process
(TLM), 208 QFP, STD90 Library.
(3) Maximum Action Frequency : 40Mhz
(4) Contain ON-CHIP OSCILLATOR.
(5) Only assist Rester Scanning Method.
(6) Image Sensor : 300/600dpi color CIS & CCD.
(7) A/D Converter : 12bits pipelined half-flash type
contain.
(8) Support Various Type of Scanning .
1) COLOR GRAY IMAGE : each 8 bits / RGB
2) MONO GRAY IMAGE : 8 bits / pixel
3) COLOR BINARY IMAGE : 3 or 4 or 6 bits
/ pixel (for CMY/CMYK/PHOTO)
4) MONO BINARY IMAGE : 1 bits / pixel
(for TEXT/PHOTO)
(9) Maximum Scanning With : A4, 600dpi
(maximum 5K available by line)
(10) Minimum Pixel Processing Time : 11 system
clock (275nsec)
(11) Ideal MSLT (A4, 600dpi Standard)
1) COLOR GRAY IMAGE : 3 X 5K X 275nsec
=4.125msec (2 CPM)
2) MONO GRAY IMAGE : 1 X 5K X 275nsec
=1.375msec (6 CPM)
3) COLOR BINARY IMAGE : 3 X 5K X 275nsec
=4.125msec (2 CPM)
4) MONO BINARY IMAGE : 1 X 5K X 275nsec
=1.375msec (6 CPM)
(12) Support Smart Media I/F
- For ECC, when the Host read/write the Smart
Media by page, automatically generating the
3 byte of parity information on the page.
(13) Contain Step Motor Controller
- Using IRQ, updating notor pattern and interval
as S/W.
- Motor pattern and interval pass by double
buffering structure.
- Possible to activating and motivating the
Image Sensor.
(14) Support Memory Copy Function
- Using DMA RX, printing image saved on
system data memory.
(15) For the various CCD I/F, support maximum,
5 lines of LGC function.
(16) Contain SRAM BIST(Built-In Self Test) Logic.
IMAGE PROCESSING PART
(1) LAT(Local Adaptive Thresholding) for TEXT
document.
- Use 5 X 5 LOCAL WINDOW
- ABC(Automatic Background Control) function
(Tmin automatic change)
(2) Mixed mode processing for PHOTO or TEXT/
PHOTO mixed document.
- (MONO/COLOR) IMAGE ENHANCEMENT
→
MODIFIED ERROR DIFFUSING.
- Serching the edge using directing edge
algorithm as considered the visual
characteristic of human then emphasize and
apply the MODIFIED ERROR DIFFUSION
METHOD.
(3) Color Halftoning
- MODIFIED ERROR DIFFUSION METHOD.
(Removing the worm artifact phenomenon which
is problem of existing errer diffusing method and
preventing the overlaping color of cyan and
megenta in the bright scene.)
- Normal copy : color ink(CMY) + black ink(K)
→
3color (CMY) or 4color (CMYK)
- Photo copy : color ink(CMY) + photo ink(KLcLm)
→
6color (CMYKLcLm)