Circuit Description - Sony DSC-S75 Training Manual

Circuit Description

See Figure 14-1
Focus and Zoom
1. The focus and zoom lenses are driven by four phase dc pulse motors. Four pulsed lines drive the motors.
2. Motor direction is determined by the sequence that the motor lines are pulsed.
3. Both lenses have end sensors that determine the end positions of the lenses during initialization.
4. The lenses are initialized each time the camera is turned on. When initialized, the lenses turn to their end
positions and trigger the sensor switches.
5. When the end sensor switches are triggered, their respective motors stop and registers inside IC301 are
reset.
6. The registers in IC301 track subsequent lens motion by counting the number of pulses that are sent to the
motors. The registers differentiate between forward and reverse drive pulses, allowing them to keep track of
lens position regardless of motor direction.
Shutter
This is a simple mechanical on/off shutter in the lens light path that opens when the camera is turned on and
closes when the camera is turned off. It blocks all light from the CCD when the camera is turned off. The shutter
is controlled by a simple two terminal motor, driven by IC203.
Do not confuse this shutter with the electronic shutter. The electronic shutter is an electronic gate to the CCD that
determines the length of time that the CCD is actively "seeing" when the picture is snapped.
IR Filter and IR Illumination
Two infrared LEDs are used as light sources for shooting in very low or no light situations when the camera is in
NightShot mode™. The IR LEDs are located in the front of the lens barrel and turn on in NightShot mode when
the shutter is pressed.
Since the CCD is made sensitive to IR light, a movable IR filter must be inserted in the light path during normal
shooting and removed during IR shooting:
•
In normal non-NightShot operation, the filter is placed in the light path and blocks IR light from the CCD.
•
In NightShot mode, the filter moves away from the light path, allowing the IR light from the scene to reach the
CCD.
IR Filter Control
•
The IR filter motor is a simple two terminal motor driven by IC203.
•
The filter position is determined by the IR sense switch. Q203 provides a dc voltage to the switch when
NightShot is enabled, allowing the IR sense switch to operate.
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14. DSC-F707 Lens Assembly