NOM02A4−MW60G

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6

DESCRIPTION OF OPERATION

Functional Description

The NOM02A4−MW60G module consists of 27 contact

image sensors, each with 64 pixel elements, that are

cascaded to provide 1728 photo−detectors with their

associated multiplex switches and four double−buffered

digital shift registers that control its sequential readout. Four

buffer amplifiers amplify the video pixels from the image

sensors and output the four analog video signals of the

module as shown in Figure 2. In operation, the sensors

produce analog image pixel signals (or video signals)

proportional to the exposure on the corresponding picture

elements on the document. Each of the VOUT1, VOUT2

and VOUT3 signals output 448 pixels for each scan line. The

VOUT4 signal outputs 384 valid pixels followed by 64 null

pixels for each scan line. The first bit shifted out from

VOUT1 during each scan represents the first pixel on the

connector end of the module.

A pictorial of the NOM02A4−MW60G cross section view

is shown in Figure 4. Mounted in the module is a one−to−one

graded−index micro lens array that focuses the scanned

document image onto the sensing plane. Illumination is

accomplished by means of an integrated LED light source.

All components are housed in a small plastic housing, which

has a glass cover. The top surface of the glass acts as the focal

point for the object being scanned and protects the imaging

array, micro lens assembly and LED light source from dust.

PCB

Sensors

Rod

Lens

LED Bar

Module Housing

Document Surface

Glass Window

Light Path

Figure 4. Module Cross Section View

Connector Pin Out Description

Connections to the module are via a 3.5 x 16.75mm

12−pin connector (Molex part number 53048−1210) located

at one end of the module as shown in the package drawing

on page 8. The location of pin number 1 is indicated on the

package drawing.

Scanner Applications

A typical use of the NOM02A4−MW60G module in

scanner applications is shown in Figure 6. The document to

be digitized is fed into the scanner where a sensor detects its

presence. The scanner then operates the motor to move the

paper under the contact image sensor module. The module

illuminates the paper with internal LEDs and the image

sensor pixel array detects the amount of reflected light and

simultaneously measures a full line of pixels which are

sampled and transferred to a FIFO for storage and

conversion to a parallel output format. Once the pixel line is

processed, the motor advances the paper and the next scan

line is captured.

Initialization

Document

Detected?

Start Scan

SP=

, CP=

CTR=0

Read 4 Pixels into Memory

Transfer Scan Line Data

Done

CTR++ == 448

no

no

yes

Document

Detected?

CP=

Initialization

Document

Detected?

Start Scan

SP=

, CP=

CTR=0

Read 4 Pixels into Memory

Transfer Scan Line Data

Done

CTR++ == 448

no

no

yes

Document

Detected?

CP=

Figure 5. Typical Scanner Algorithm

Figure 5 outlines the basic steps in the scanner control

sequence. First the circuits are initialized and the scanner

waits for a document to be detected, usually by a paper

sensing switch. Then a start pulse and clock pulse are

supplied to capture a line image. At the next clock pulse the

first pixel value appears on the output. The pixel can be

stored in a local line buffer memory. Subsequent clocks

cause the remaining pixels to be shifted out and stored in the

line buffer. Once the complete line has been shifted out it can

be transferred to the host application and the system

advances the paper and the line scan process repeats until the

paper sensing switch indicates the document has passed

completely through the scanner.

Device Marking and Barcode Description

Each module is marked with a tag that contains the part

number, a number combining the manufacturing date code

and serial number and a barcode. The barcode presents the

date code and serial number in Interleave 2 of 5 barcode

format as follows

YYMMSSSSSS

where

YY is the year,

MM is the month, and

SSSSSS is the serial number.

Glass Lens Care

Precautions should be taken to avoid scratching or

touching the glass lens. The glass lens may be cleaned with

alcohol.