CAMBIOS EN EL USO Y COBERTURA
ESCENARIO BASE DE EMISIONES (1990)
5.3.5.1 Dust Detection in Stream Reading Mode
0008-7512iR5570 / iR6570
The machine uses the dust detection control mechanism to check for dust on the platen glass and the ADF platen roller, thus preventing reproduction of dust, if any, in output images.
Timing of Control 1. at the end of a job
2. between sheets (for every sheet)
F-5-26
*Executed only if dust has been detected at all points (A, B, C, D, E) during the previous job. In such a case, the machine will use the point subjected to least dust, and executes correction before starting a read operation. Particulars of Control
- At the End of a Job (changing the stream reading dust read position)
The machine measures the light reflected by the surface of the platen roller, and detects the presence/absence of dust with reference to its intensity. If the presence of dust is detected, the machine moves to the next point (5 points max.; A -> B -> C -> D -> E).
The machine uses the first point at which the absence of dust is detected as the read point for the next job. 1 A B A B2 A B3 A B4 A B1 A B2 A B3 Original size A3 B4 A4R A4 B5 B5R A5 B6 none Original sensor 1 CCD point of detection AB-Configuration Original size 11"x17" LGL LTRR LTR STMTR STMT absent CCD point of detection Inch-configuration
change absent :change present Original sensor 3
Dust detection control* Dust detection control
Dust detection control Start key ON 1st SCAN 2nd SCAN
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F-5-27
If dust is detected at all 5 points (A, B, C, D, E), the machine will issue an alert in response to the placement of an original in the ADF, thus promoting the user to clean the points.
Alert Message:
The machine may read the dust, which may show as lines in the output image. Clean the narrow segment of glass indicated in the drawing with a soft cloth moistened with water (and well wrung).
Press the Close button to reset the alert.
At the start of a job, the machine executes dust detection once again, and will use a point with little or no dust as the read point.
*1: read point at the end of the previous job. *2: point with little or no dust.
T-5-9
A read reference point (1.0 mm to the left from the center of the platen roller)
B point 1.0 mm to the left from the reference point C point 0.5 mm to the left from the reference point
A D E pattern 1 pattern 2 pattern 3 pattern 4 pattern 5
At the start of a job At the end of a job
0.5mm B C 0.5mm 0.5mm 0.5mm *2 *1 *1 *1
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- Between Sheets (dust correction)
The machine does not move the scanning lamp on account of dust detection.
If dust is detected between sheets, the machine corrects the fact with reference to the pixels on both sides of the area of dust.
SERVICE MODE:
COPIER>OPTION>BODY>DFDST-L1 (level 1) use it to adjust dust detection level between sheets COPIER>OPTION>BODY>DFDST-L2 (level 2) use it to adjust dust detection level at the end of a job
5.3.5.2 White Plate Dust Detection Control
0008-7513iR5570 / iR6570
The white plate can collect stray dust inside the reader unit, causing lines in images, and the machine is equipped with a mechanism to check for dust on the plate and correct it to limit its effects on output images.
Timing of Control 1. Before a Job
- white plate dust detection - white plate dust correction 2. After a Job
- white plate dust detection - white plate dust correction
F-5-28 Particulars of Control
- White Plate Dust Detection
The machine compares the data on the light reflected by the white plate at time of fixed shading and shift shading to check for dust on the white plate while at the same time identifying the coordinates and width of the area of dust.
D point 0.5 mm to the right for the reference point
E point 1.0 mm to the right from the reference point (center of platen roller)
Dust detection control Dust detection control
Start key ON 1st SCAN 2nd SCAN
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- White Plate Dust Correction
If the machine detects the presence of dust, it corrects the shading correction coefficient of the area of dust by means of a correction coefficient used for both sides of the area with dust, thus limiting the effects of the dust.
F-5-29
5.3.6 Image Processing
5.3.6.1 Overview
0008-7514iR5570 / iR6570
The PCBs used in the image processing system have the following functions: CDD/AP PCB: CCD drive, analog image processing, A/D conversion Reader controller PCB: shading correction
F-5-30 1. Analog Image processing
Correction Algorithm Data on light reflected
by the white plate (shift shading))
Data on light reflected by the white plate (fixed shading)
Identifies the coordinates of the start of dust and width
The machine corrects the correction coefficient of the area of dust using data for areas on both sides
Point of white plate data
measurement at time of fixed shading
White plate data correction area at time of shift shading
White plate Dust Comparison CCD/AP PCB Reader controller PCB CCD A/D
conversion Shading processing Analog image
processing
Analog image processing block
Controller block Digital image processing block
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- CCD drive
- CCD output gain correction, offset correction - CCD output A/D conversion
F-5-31 2. Digital Image Processing
- shading correction
F-5-32
5.3.6.2 CCD Drive
0008-7515iR5570 / iR6570 1. CCD
The CCD used in the machine is a 1-line linear image sensor. - Number of pixels: 7450
- Size of a pixel: 4.7 x 4.7 ym 2. CCD Drive
The signals converted by the light-receiving block are sent out in 2 analog video signal channels (even-numbered pixels, odd-numbered pixels).
CCD (1 line each for R, G, and B)
Analog image signal Analog image process - gain correction - offset correction A/D conversion CCD drive control A12V A5V J101 J204 J204 J102 J205 CCD control signal Gain correction data Digital image signal Reader controller PCB Odd-numbered pixel Odd-numbered pixels Even-numbered pixels CCD/AP circuit 10 Even-numbered pixel Gain correction data EEP-ROM SRAM CPU Shading correction Digital image signal CCD/AP PCB Reader controller PCB 10 Digital image signal 8 Target value J101 J102 J204 J205 J203
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F-5-33
5.3.6.3 CCD Output Gain Correction, Offset Correction
0008-7516iR5570 / iR6570
The machine processes the analog video signals from the CCD so that the rate of their amplitude is a specific level. The machine also makes sure that the output voltage in the absence of incident light is of a specific level (offset correction).
5.3.6.4 CCD Output A/D Conversion
0008-7517iR5570 / iR6570
The odd-numbered and even-numbered pixel analog video signals after correction are further converted into 10-bit digital signals representing specific pixel voltage levels by the A/D converter.
5.3.6.5 Outline of Shading Correction
0008-7518iR5570 / iR6570
The machine executes shading correction so that the CCD output will be even when the density of the original is even.
The output of the CCD may not necessarily be even because of the following factors even if the density of the original is perfectly even:
1. variation in the sensitivity of the individual pixels of the CCD
2. difference in the degree of light passing through the center of the lens and through its edge 3. difference in the intensity of light between the center and ends of the scanning lamp 4. deterioration of the scanning lamp
The machine executes shading correction to make up for the variation in the output of the CCD.
Shading correction may be shading adjustment executed to determine a service mode target value or shading correction executed for every job.
5.3.6.6 Shading Adjustment
0008-7519iR5570 / iR6570
In shading adjustment, the machine measures the density of a white sheet of paper and the standard white plate, and Shift register Light-receiving block (photo diode) Shift register Output buffer Output buffer Gate Gate 1 2 3 4 5 6
Odd-numbered pixel data
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stores the measurements in memory. The machine then computes these measurements for use as the target value for shading correction. Shading adjustment is executed at time of machine installation or scanning lamp replacement, or when a change has occurred in the intensity of light over time.
Service Mode:
COPIER>FUNCTION>CCD>CCD-ADJ
5.3.6.7 Shading Correction
0008-7520iR5570 / iR6570
The machine executes shading correction for every scan of an original.
The machine shines the light of the scanning lamp against the standard white plate, and measures the light reflected by the plate; it then uses the analog image processing block of the CCD/AP PCB to turn the measurements into digital data, which will be sent to the shading correction circuit of the reader controller PCB in the form of a shading coefficient.
In the shading correction circuit, the shading coefficient is compared against the target value stored in memory, and the machine uses the differences as the shading correction value.
The shading correction value is used to make up for the variation among individual pixels of the CCD occurring at each scan, thus evening out the image density level.
F-5-34 CCD output
Original density Standard white plate
Characteristics before correction Target value Measurement Characteristics after correction White
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5.4
Parts Replacement
Procedure
5.4.1 CCD Unit
5.4.1.1
Removing the
Copyboard Glass
0008-7656 iR5570 / iR6570 1) Open the ADF.2) Remove the 2 screws [1], and detach the right glass retainer [2]; then, detach the copyboard glass [3].
F-5-35
When detaching the copyboard glass, take care not to touch the white plate attached to its back. (Soiling can cause lines in the image). If soiled, clean it using lint- free paper moistened with alcohol.)
Take care not to deform the sponge attached to the right glass retainer [1].
F-5-36
5.4.1.2 Removing the CCD
Unit Cover
0008-7657iR5570 / iR6570
1) Remove the 9 screws [1], and detach the CCD unit cover [2]. F-5-37 [1] [2] [3] [1] [2] [1] [1] [2]