Text preview for : 7050e020.pdf part of konica 7050e 7050e service manual and instructions
Back to : 7050e.zip | Home
2
PROCESS
2. PROCESS
OUTLINE AND COMPOSITION ....................... 2-1 IMAGE READ MECHANISM ............................ 2-2 [1] Outline ..................................................... 2-2 IMAGE PROCESSING ..................................... 2-3 [1] Outline ..................................................... 2-3 [2] Analog Processing .................................. 2-3 [3] A/D Conversion ....................................... 2-3 [4] Shading Correction ................................. 2-3 [5] Brightness/Density Conversion ............... 2-4 [6] EE Processing ........................................ 2-4 [7] Text/Dot Pattern Identification ................. 2-4 [8] Filtering ................................................... 2-4 [9] Magnification Processing ........................ 2-5 [10] Reversal Processing ............................. 2-6 [11] Copy Correction .................................. 2-6 [12] Selector, SGU ....................................... 2-6 [13] Write Density Control ............................ 2-6 [14] Error Diffusion Processing ..................... 2-6 [15] mage Compression Processing ............ 2-6 [16] Memory ................................................. 2-6 [17] Two-beam control .................................. 2-6 IMAGE WRITE .................................................. 2-7 [1] Outline ..................................................... 2-7 [2] Collimator lens ........................................ 2-8 [3] Beam combining prism ........................... 2-8 [4] Compression Prism ................................. 2-8 [5] Fine Adjustment Prism ............................ 2-8 [6] Polygon mirror ......................................... 2-8 [7] f lens...................................................... 2-8 [8] Cylindrical Lenses ................................... 2-9 [9] Index Sensor ........................................... 2-9 IMAGE FORMATION ...................................... 2-10 [1] Charging ............................................... 2-10 [2] Exposure ............................................... 2-10 [3] Developing ............................................ 2-10 [4] Transfer ................................................. 2-10 [5] Separation ............................................. 2-11 [6] Cleaning ................................................ 2-11 [7] PCL ....................................................... 2-11
PROCESS
OUTLINE AND COMPOSITION
Image read unit Charging corona unit image write unit
Image processing unit Fixing unit PCL
Polygon mirror Developing unit
Cleaning unit
Separation corona unit Fig.1
TSL Transfer corona unit OPC drum
In this digital copying machine, optical data (light beam) reflected from the original is converted into electrical signals, subjected to image processing, then converted back into optical data (light beam) and directed onto the drum. Figure 1 shows the composition of the machine, and Fig.2 an outline of the digital copying process.
Optical data Original Image read
Electrical signal Image processing
Electrical signal
Image write
Optical data Developing
PCL
Charging
Cleaning
Separation Transfer corona
C
Fixing Fig.2
2-1
PROCESS
IMAGE READ MECHANISM
Light source (halogen lamp) 2nd mirror
1st mirror Image sensor
Lens Fig.3
3rd mirror
[1] Outline
A halogen lamp is used as the light source, and the light from the lamp is directed onto the original. The light reflected off the original is reflected by the 1st, 2nd and 3rd mirrors shown in Fig.1, then passed through the lens and directed onto the CCD image sensor. The CCD image sensor consists of 5000 pixels. One pixel is 7 µm in length, and the length on the original that can be read by one pixel is 63.5 µm.
2-2
PROCESS
IMAGE PROCESSING
CCD image sensor A/D Board
C
A/D conversion
Shading correction
C
Brightness/density conversion, EE processing, Text/ dot pattern judgement, Filter/ magnification processing Reversal processing
Copy correction
C
Image Processing Board
Selector/SGU
Write density control
2-beam control
Image write Error diffusion processing
Data compression and expansion Electronic RDH Fig.4
Memory
[1] Outline
The analog signal produced by opto-electric conversion by the CCD sensor on the A/D board is subjected to analog processing, then A/D-converted, and subjected to image processing. Image processing consists of shading correction, brightness/ density conversion, EE processing, text/dot pattern judgement, filter/magnification change processing, copy correction, write density correction, and 2-beam control. In addition, error diffusion processing and data compression are carried out within electronic RDH.
1. White correction
The voltage output from each pixel of the CCD sensor when the white reference plate is exposed to the light from the exposure lamp is memorized as the maximum output value for that pixel.
2. Black correction
The output voltage from each pixel of the CCD sensor when the exposure lamp is out is memorized as the minimum output voltage for that pixel. * Based on the difference between the white and black data for each pixel memorized in 1 and 2 above, the calculated result that indicates the number of the step corresponding to the image data read from the original is output to an accuracy of 10 bits.
C
C
[2] Analog Processing
In the analog processing board, the minute signals from the CCD sensor are amplified and also level-shifted into the A/D conversion range. Amplification and level-shifting take place automatically at the shading correction timing by an electronic variable resistor, hence there is no need to perform manual adjustment.
(1)
+3 0V
Read width White
[3] A/D Conversion
The image signals from the analog processing board are converted one pixel at a time into 9-bit digital signals.
(2)
Read voltage Read width
Black
[4] Shading Correction
Shading correction is done to even out the light distribution of the CCD sensor. The following correction takes place at the specified timing.
512
White
0
After shading correction (1)····A/D input (2)····Shading output Fig.5
Black
2-3
PROCESS
[5] Brightness/Density Conversion
The signal resulting from shading correction corresponds to the light reflected off the original, hence it is generally called a brightness signal. The brightness/density conversion section converts the brightness signal into a density signal, as shown below.
C
[7] Text/Dot Pattern Identification
In order to copy an original under the optimum conditions, the text/dot pattern identification section judges whether the read part is text, dot pattern or a photograph, and uses the results in the subsequent filtering section.
[8] Filtering
255
Density
Appropriate filtering takes place according to the kind of original and the selected magnification. (1) Text filter ................ Highlights the light and dark parts of the original. (2) Dot pattern filter ..... Reduces moire. (3) Photograph filter .... Improves the gray scale reproduction.
0
Brightness Fig.6
1024
[6] EE Processing
A density that is suitable for the density of the original is automatically selected by EE processing, and a suitable copy made.
1. EE sampling range
(1) Platen mode: B5R width x Original length
2-4
PROCESS
[9] Magnification Processing
In an analog machine, the horizontal magnification is changed by changing the scanning speed of the exposure unit, and vertical magnification by changing the position of the lens. In this machine, the horizontal magnification is changed by changing the scanning speed of the exposure unit, and the vertical magnification by means of electrical image processing. The read unit of the CCD (63.5 µm) and the write unit of the laser (63.5 µm) are equal to each other, and remain unchanged when the copy image is enlarged or reduced in the vertical direction. As a result, write data that corresponds exactly to the write position when the image is enlarged or reduced in the vertical direction sometimes fails to exist.
2. Vertical magnification change processing during reduction
As shown in the example of Fig.11, if the pixel data obtained when the original is read by the CCD is D1 to D5, the positions of the read data when the image is reduced overlap each other as indicated by R1to R5, hence the write positions fail to coincide with the read positions.Therefore, the write density is determined as shown below.
C
Original read position
D1
D2
D3
D4
D5
1. Vertical magnification change processing during enlargement
As shown in the example of Fig.10, if the pixel data obtained when the original is read by the CCD is D1 to D5, the positions of the read data when the image is enlarged are E1 to E5.. However, the following problems will occur if the write data consists of this read data alone. (a) There will be a gap between one data and the next, resulting in gaps in the image. (b) The data position and write position will not coincide exactly. Consequently, if read data that corresponds exactly to the write position fails to exist, as indicated by the dotted lines of Fig.10, the write density is determined as shown below.
Data position when the image is reduced
R 1
R 2
R 3
R 4
R 5
Write position
W1 W2 W3 W4 W5
Fig.11
3. Density correction
Figure 11 is a graph the vertical axis of which represents density (256 steps) and the horizontal axis of which represents position: Here, the distance between E2 and E1 of Fig.10 is set out on the horizontal axis and divided into 16 steps. If the position with respect to write data W2 is " ", the density S can be obtained using the following equation.
Original read position D1 D2 D3 D4 D5
S = E1 + (
E2 E1 )x 16
Data position when image is enlarged
E1
E2
E3
E4
E5
255
Write position
W1
W2 W3 W4 W5 W6
W7 W8
E2
S
W2
Fig.10
Density
E1 0 0
Position Fig.12
15
2-5
PROCESS
C
[10] Reversal Processing
This function reverses the input brightness data in order to reverse black and white when the reverse copy mode is selected.
[15] Image Compression Processing
This processing function stores compressed image data in the memory to enable a large quantity of image data to be stored when electronic RDH is used.
C
[11] Copy Correction
The copy correction function selects the density curve corresponding to the density selected by the density button on the operation panel. The selected density curve is applied to the data that was subjected to filter/magnification change processing. Suitable density curves are provided for the text, photo and text & photo modes.
[16] Memory
The memory can hold about seventy A4 size originals consisting of average word processor text. The number of pages will be less than this, if the originals include many photographs and dot pattern images. Expansion memory units MU-101 and MU-102 are available as options.
[17] Two-beam control
This function is used to adjust the timing of the laser data from the two beams and also to detect and correct any deviation between the two beams.
C
[12] Selector, SGU
Selector is a function that switches between the image signal from the electronic RDH, and the read time image processed signal. SGU is a function that generates various test patterns.
C
[13] Write Density Control
The write density control function converts image data to the optimum laser exposure based on the characteristics related to the drum like drum potential, toner density, etc.
1.5
Copy density
0
Laser exposure level Fig.13
255
[14] Error Diffusion Processing
Error diffusion processing is intended to make efficient use of the installed memory and also to obtain a satisfactory copy image.
2-6
PROCESS
IMAGE WRITE
CY2 lens Polygon mirror f lens unit
3rd mirror Stepping motor Compression prism 1
C Collimator lens unit 1 Semiconductor laser LD1
1st mirror C 2nd mirror CY1 lens Beam combining prism Fine adjustment prism 2 C
Glass cover
Compression prism 2 Collimator lens unit 2 C
Index mirror
Index senser
C
Fine adjustment prism 1
Semiconductor laser LD2 2nd mirror C
C
3rd mirror
1st mirror
C
Fig.14
[1] Outline
Figure 14 shows the layout of the various parts of the write unit. The processed image data is output by semiconductor lasers. The light output from these lasers is sent via the path shown in Fig.15 to the OPC drum.
C
Semiconductor laser 1 (LD1)
Semiconductor laser 2 (LD2)
Collimator lens unit 1
Collimator lens unit 2
Compression prism 1
Compression prism 2
Fine adjustment prism 1 (sub scanning)
Fine adjustment prism 2 (main scanning)
Beam combining prism
Cylindrical lens 1 (cy1)
Polygon mirror
f lens unit
1st mirror 2nd mirror
Cylindrical lens 2 (Cy2)
3rd mirror
OPC drum
Index mirror Fig.15
Index sensor
2-7
PROCESS
[2] Collimator lens
Figure 16 shows the function of the collimator lens. This lens is used to form the light which diverges from a point source into a parallel beam.
[6] Polygon mirror
This is a multi-sided mirror which converts the laser beam into a scanning beam. An octagonal mirror is used in this machine. Figure 18 shows the appearance of the polygon mirror.
Semiconductor laser
Collimator lens
Parallel beam Fig.18
[7] f lens
The polygon mirror rotates at a constant angular speed. Consequently, if a general image forming lens were to be used, the speed at which the laser beam scans the surface of the drum would vary at the center and the both edge of the drum, as shown in Fig.19.
Fig.16
[3] Beam combining prism
This prism causes the beams from the two semiconductor lasers mounted at right angles to each other to be output in the same direction.
Laser beam Drum; Scanning speed falls as beam approaches center of drum.
Semiconductor laser 1
Polygon mirror
Image forming lens
Fig.19
Beam combining prism Semiconductor laser 2
An f lens is used to maintain the scanning speed constant over the entire length of the drum.
Fig.17
Laser beam
[4] Compression Prism
This prism shapes the beam radiated from each semiconductor laser, and adjusts the height in the up-down direction.
Drum; Scanning speed is constant. f lens Cylindrical lens
[5] Fine Adjustment Prism
This prism performs fine adjustment of the beam radiated from each semiconductor laser in the left-right and up-down directions.
Polygon mirror
Fig.20
2-8
PROCESS
[8] Cylindrical Lenses
Two lenses, cylindrical lens 1 (Cy1) and cylindrical lens 2 (Cy1), are used to eliminate the tilt error of the polygon mirror. Cylindrical lenses 1 and 2 are installed before and after the polygon mirror, as shown in Fig.21. The laser beam is focused on the polygon mirror by means of cylindrical lens 1, and the light reflected off the polygon mirror is once again focused on the drum by means of cylindrical lens 2. The optical relationship between the polygon mirror and the drum face with respect to cylindrical lens 2 is that of image and object. Consequently, even if the polygon mirror is tilted, the light path is corrected by cylindrical lens 2, ensuring that the beam is scanned along the same line.
Semiconductor laser
Cylindrical lens 1 (Cy1)
f lens
Mirror
Collimator lens
Polygon mirror
Cylindrical lens 2 (Cy2) Drum
Fig.21
[9] Index Sensor
This sensor is intended to determine the leading edge write position for each scan in the axial direction of the drum, and also to determine the positions of the two beams.
2-9
PROCESS
IMAGE FORMATION
[1] Charging [3] Developing
Charging corona unit
Fig.22
Fig.24
A negative charging method using a Scorotron is employed. A constant negative voltage is applied to the charging plate and back plate in order to maintain the potential of the drum constant.
Negatively charged toner adheres to the parts of the surface of the drum where charge was erased during the exposure process.
[2] Exposure
[4] Transfer
Drum
Transfer corona unit
C
TSL
Fig.23
Fig.25
Exposure is performed by means of the laser beams, causing the charge on the drum to be erased. Two laser beams are used to write (exposure) two lines of image data at a time.
The transfer corona unit causes the toner on the drum to be transferred to the paper by means of a discharge from the back of the paper. The TSL improves the transfer of the toner and the separation of the paper.
2 - 10
PROCESS
[5] Separation
[7] PCL
PCL
Drum
Separation corona unit
Fig.26
Fig.28
The separation corona unit erases the charge on the paper by applying an AC discharge from the back of the paper, thus enabling the paper to separate from the drum under its own weight.
The PCL erases the potential remaining on the surface of the drum.
[6] Cleaning
Cleaning blade
Toner collecting roller
Drum
Fig.27
Toner remaining on the drum is removed by the cleaning blade.
2 - 11