22

SQUAL

Address: 0x06

Access: Read

Reset Value: 0x00

Data Type: Upper 8 bits of a 9-bit unsigned integer.

USAGE: SQUAL (Surface Quality) is a measure of the number of valid features visible by the sensor in the current

frame.

The maximum SQUAL register value is 242. Since small changes in the current frame can result in

changes in SQUAL,

variations in SQUAL when looking at a surface are expected. The graph below shows 800 sequentially acquired SQUAL

values, while a sensor was moved slowly over white paper. SQUAL is nearly equal to zero, if there is no surface below

the sensor. SQUAL is typically maximized when the navigation surface is at the optimum distance from the imaging

lens (the nominal Z-height).

Bit

7

6

5

4

3

2

1

0

Field

Figure 22. SQUAL Values at 800cpi (White Paper)

Figure 23. Mean SQUAL vs. Z (White Paper)

SQUAL Value (White Paper)

At Z=0mm; Circle = 7.5" diameter; Speed=6ips

0

50

100

150

200

1

56 111 166 221 276 331 386 441 496 551 606 661 716 771 826

Count

Mean SQUAL vs Z (White Paper)

At Z=0mm; Circle = 7.5" diameter; Speed=6ips

0

50

100

150

200

1.6

1.8

2.0

2.2

2.4

2.6

2.8

3.0

3.2

Delta from Nominal Focus (mm)

Avg-3sigma

Avg

Avg+3sigma

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PixArt Imaging Inc.

PixArt Imaging Inc.

ADNS-7550 Integrated Molded Lead-Frame DIP Sensor