Fig. 417 Block Diagram Of Light Travel - Canon NP-70 Service Manual

NP -70
4-13
4.3 OPTICAL ASSEMBLY
4.3-1 OUTLINE OF ASSEMBLY OPERATION
The Optical Assembly is positioned to the right end of the body and it forms an image for the
drum surface from the sheet original on the copyboard. Light travels along the path from the
mirror to the lens unit and, finally, the drum as indicated in Fig. 4-17.
Illumination
Lamp
Drum
Original
Dustproofing
Glass 1
Mirror
Exposure
Mask
Lens Unit
Fig. 4-17 Block Diagram of Light Travel
Dustproofing
Glass 2
Fig. 4-17 indicates the path by which the original image reaches the drum. In order to form a
complete image, no interferance should be present along the path of light travel. Dustproofing
glasses 1 & 2 and the reflecting mirror should be kept clean to preserve high quality copying.
The optical chamber interior is protected from contamination by a dustproofing cover. The
diaphragm in the lens unit controls the light intensity to the drum surface depending on the
sheet original contrast desired to get an ideal copy. The diaphragm mechanism is connected to
the exposure dial by string. By this connection, the quantity of light can be controlled direct-
ly by the operation of the exposure dial. The exposure mask is mounted in front of the drum
to provide equalized light distribution on the drum surface.
© CANON INC.
Second Printing-June, 1974