Detecting The Size Of Originals; Scanning Lamp; Turning On And Off The Scanning Lamp - Canon iR C6800 Series Service Manual

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The machine's scanning lamp is a xenon lamp, which uses xenon gas sealed inside. On the outside of the glass tube,

2 electrodes are arranged in parallel with the tube; the inside of the tube, on the other hand, is coated with fluorescent

material. When a high frequency high voltage is applied to the electrodes, the gas inside the tube starts to discharge,

causing the fluorescent material to emit light.

The scanning lamp is turned on and off by the drive signal (LAMP_ON) generated by the CPU of the reader control

PCB. When the signal is generated, the inverter PCB generates high frequency high voltage in the activation control

circuit using the drive voltage (+24 V) supplied by the reader controller PCB to turn on the xenon lamp.

5.3.4 Detecting the Size of Originals

5.3.4.1 Identifying the Size of Originals

The machine identifies the size of an original based on combinations of measurements taken of the light reflected by

specific points (using a reflection type sensor and CCD). In consideration of possible displacement of the original

when the ADF is closed, the machine uses a 2 point CCD check.

Main Scanning Direction: by CCD (AB configuration; 8 point measurement; inch configuration, 6 point

measurement)

Sub Scanning Direction: reflection type photo sensor (AB configuration: 1 point measurement; inch configuration:

1 point measurement)

Specifically, the following takes place:

1.External Light Search (main scanning direction only)

While keeping the scanning lamp off, the machine measures the level of the CCD at specific points in main scanning

2.Sensor Output Level Detection

The machine turns on the scanning lamp, and measures the sensor output at specific points. It then checks

combinations of these measurement to find the size of the original.

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