19

Squal (White Paper)

0

10

20

30

40

50

60

Count

Mean SQUAL vs Z (White Paper)

-10

0

10

20

30

40

50

60

1.6

1.82

2.22.42.62.83

3.2

Distance from Lens Reference Plane to Tracking Surface - Z (mm)

Avg-3sigma

Avg

Avg+3sigma

Figure 21. Mean squal vs. Z (White Paper)

SQUAL

Address: 0x05

Access: Read

Reset Value: 0x00

Bit

76543210

Field

SQ7

SQ6

SQ5

SQ4

SQ3

SQ2

SQ1

SQ0

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 128. 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).

Figure 20. Squal values (white paper)

PixArt Imaging Inc.

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PixArt Imaging Inc.