2 Functional Overview Operation and Timing Optical System A contact sensor unit is used for the optical system. When the optical system is operating, the light-emitting diode (LED) array emits light to the document and the photo transistors detect the light reflected from the document. Document Scanning Function • The image sensor scans documents of up to letter size width (8.5 inches or 215.9 millimeters) at the horizontal scanning resolution of 300 dpi. • The vertical scanning resolution is 300 dpi. • The image sensor is a dust-free structure that prevents dust from accumulating on the photo transistors’ surfaces.
The light emitted by the LED array goes through the glass and is reflected by the document. This reflected light is then converted to electrical signals by the photo transistors in the sensor unit. This method requires no lens. Structure of the Image Sensor The image sensor consists of the following: • The LED array emits the scanning light. The LED array consists of 36 LEDs and is controlled by the control system. • The glass is in contact with the document. • The photo transistor array receives the reflected light. The photo transistor array consists of 2,574 photo transistors and 11 driver circuits. Each driver circuit amplifies the output of 234 photo transistors.
The output from the 11 driver circuits is converted to the serial data and sent to the control unit. • The guide film prevents the document from becoming jammed. EN Functional Overview 2-1