Lens/Mirror Position Initialization - Ricoh FT7770 Service Manual

3. Lens/Mirror Position Initialization

The CPU determines the location of the lens and controls its positioning
through the lens home position sensor.
mounted on the lens/mirror drive pulley.
The home position is initialized each time the lens passes the full size posi-
tion, However, when moving from a reduction position to another reduction
position or from an enlarge position to another enlarge position, the home
position is not referenced, In such cases the lens moves directly to the se-
lected position.
The lens moves in different ways when it references the home position
depending on which positions it is moving between. The lens movements for
all the combinations of start and stop positions are shown in the illustra-
tion.
If the lens passes through the home position, the pulse count for lens/mirror
positioning starts when the lens passes the lens home position sensor. In
cases where the lens does not pass through the home position (enlarge--> en-
large or reduction--> reduction), the pulse count starts when the motor turns
on.
When moving from full size to reduction, reduction to enlarge, or enlarge to
reduction, the lens goes through the home position, reverses, goes back
through the home position, reverses again, and finally moves to the selected
position. This action relieves backlash pressure in the mechanism to reduce
wear and prevent mispositioning.
This sensor is activated by a disk
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April, '89