• Where component pin-out count must be kept to a minimum.

The background-tracking-digitizing circuits in the PI331MC-DR have been referred to as

the “dynamic threshold” two-level A/D converter. For the purpose of describing the

module’s characteristics this “dynamic threshold” processing circuit shall herein be

referred to as the “tracking digitizer”.

Module Description

The PI331MC-DR module consists of 11 sensors that are cascaded to provide 1056

photo-detectors with their associated multiplex switches, and a digital shift register that

controls its sequential readout. Mounted in the module is one-to-one graded-indexed

micro lens array that focuses the scanned documents to image onto its sensing plane. A

buffer amplifier amplifies the video pixels from the image sensors and passes them to

analog digitizing circuit, where video pixels are converted to digital signal and passed to

output of the module. See Figure 1, the block diagram of the PI331MC-DR module.

Illumination is by means of an integrated LED light source. All components are housed in

a small plastic housing with a cover glass which acts as the focal point for the object being

scanned and protects the imaging array, the micro lens assembly, and the LED light

source from dust. The pictorial of PI331MC-DR cross section is shown in Figure 2.

PAGE 2 OF 9 - PI331MC-DR, 11-8-00

Figure 1. PI331MC-DR Module Block Diagram.

ROD LENS

SHIFT REGISTER

PHOTO SENSORS

BUFFER

LED

LED

LED

LED

LED

LED

LED

LED

CP

SP

GRD

GLED

VLED

VN(-V)

VDD (+5)

GRD

DIGOUT

- - - - - - - - - - - - - - - -

1054

1055

1056

TRACKING DIGITIZER

VIDEO

LINE

1

2

3

4

5

VIDEO

AMP