Canon i-SENSYS LBP5300 Series Service Manual page 51

Light emitter (LED)
Light receiver (PD)
<Normal operation>
1) The DC controller forms a pair of pattern images for every color (Bk, Y, M, C) on the ETB to detect color misregistration when the corrective control is started.
A pair of pattern images are formed on the ETB surface; one is on the left side and the other is on the right side.
2) The DC controller allows the light emitter (LED) to emit light by sending the COLOR MISREGISTRATION/IMAGE DENSITY DETECTION LED DRIVE
signal, upon the color misregistration detection is started.
3) The ETB reflects the light from the LED and the light receiver (PD) in the color misregistration sensor receives the light. This reflected light intensity differs
depending on the toner image density on the ETB.
4) The PD converts the received light intensity into voltage and sends it in form of the COLOR MISREGISTRATION signal to the DC controller.
5) The DC controller measures the position of each pattern image by detecting when the timing of the COLOR MISREGISTRATION signal varies and calculates
the misregistration difference on each color.
6) The calculated misregistration information of each color is sent to the video controller.
7) The video controller controls each color's VIDEO signals according to this information and optimizes the main-scanning start position, the main-scanning
magnification, and the sub-scanning start position.
<Abnormal operation>
The DC controller notifies the video controller of each error when the following errors are found during the color misregistration detection. The misregistration
correction value is initialized whenever an error occurs.
- Color misregistration sensor abnormality warning: The light receiver does not receive light at all.
- Color misregistration measurement out of range warning: The measurement value is out of specified range.
Pattern image for color misregistration correction
The whole pattern image for the color misregistration correction. The pattern images are formed on both sides of the ETB certain distance away from the center.
The pattern image for sensor light calibration, the pattern image with four colors slant bars for main-scanning difference measurement, and the pattern image
with horizontal lines (Bk on left side and Y/C/M on right side) for sub-scanning difference measurement are formed on the ETB sequentially.
The pattern image with horizontal lines for sensor light calibration are formed in order of yellow, cyan, black, and magenta.
The pattern image with four colors slant bars for main-scanning difference measurement are formed in order of yellow, cyan, black, and magenta.
The pattern image of horizontal bars for sub-scanning difference measurement are formed black on left side and yellow, cyan, and magenta in order on right
side. This is for the comparison of each color registration based on the black position.
Each pattern image is described in the following.
Pattern images
for color misregistration correction
COLOR MISREGISTRATION signal
Pattern images
for color misregistration correction
F-2-21
Video controller PCB
DC controller PCB
Color misregistration/
image density sensor (R)
COLOR MISREGISTRATION
IMAGE DENSITY signal
COLOR MISREGISTRATION
IMAGE DENSITY DETECTION LED DRIVE signal
Color misregistration/
image density sensor (L)
ETB
Chapter 2
2-15