- When the ADF is at 25 deg or lower, the external light within the width of any original is kept out of external light, thus causing the machine to assume the absence

of an original at points of external light detection (external light search operation).

The ADF open/closed sensor 2 identifies the state as being "closed," and the machine starts original size detection.

Here, B5, B4, A4, and A3 are eliminated from the list of possible sizes.

- When the external light search is over, the machine turns on the xenon lamp for the main scanning lamp, and checks the CCD (4 points) for external light. For sub

scanning direction, the machine starts to operate the original sensor.

4. ADF Fully Closed (5 deg or less)

No. 1 mirror base: at point of original detection

scanning lamp: on

original sensor: original detection operation

The machine looks for a change in the output level of individual sensors for a period of 2 sec after the ADF open/closed sensor 1 has identified the current state

as being "closed." The absence of a change in the level causes the machine to assume the presence of an original at the point in question.

The machine uses the combination of changes in the levels of 5 points to identify the size of the original in question.

5. In a Wait State (for a press on the Start key)

No.1 mirror base: at point of original detection

scanning lamp: off

original sensor: off

5-10

Scanning lamp

Original sensor

Point of detection 1

ADF

Point of detection 2