Kodak Ektapro Slide Projector 4020 - Manual (Page 52)

AUTO FOCUS
The AUTO FOCUS feature is installed in the EKTAPRO Model 5020,9020 and 9020/CINE.
A “low” FOCUS EXT signal from the MICROCONTROLLER enables the AUTO FOCUS PCB while a “high” signal
disables the AUTO FOCUS to ensure a sharpness correction for the projected slide. If a manual sharpness
correction was necessary the AUTO FOCUS MOTOR moves back to its primary position after the next slide
change. The AUTO FOCUS MOTOR is running until both receivers has the same light input. The FOCUS
MOTOR stops at the time the light input on both Photo transistors is equal. The direction for the focus movement
is defined by either receiver port 1 or port 2.
An electronic circuit will determine the operating voltage for the FOCUS MOTOR (running forwards or backwards)
to ensure to have the same speed in both directions. This regulation is necessary because the LENS CARRIER
is basic loaded with a spring in one direction.
To ensure that the AUTO FOCUS function works properly it is very important to use the same kind of slide
frames. Mixing up glass slides with other slides will bring the projected image out of focus because there is only
one reference point for the lens position to get a sharp and clear projected image on the screen.
If glassless slide frames are in use, it could be, that the borders of the projected image are out of focus.
It depends on the IR-Beam which is only sensing the center of the slide.
MASTER
BOARD
AF
BOARD
M
FOCUS
LOGIC
Slide
Prism
IR-
Receiver
IR-
Trnasmitter
Focus Motor
Prism
Focus Command
from Keyboard or
Remote Control
T1 T2
5V DC
GND
Foc Ext2
Foc Ext1
Speed
Direction
FOCUS
MOTOR
CONTROL
MICRO
CONTROLLER
figure 3-13
Service Manual SM 2547-1
03/98 3-16 Kodak AG, Stuttgart