adns-7700 Avago Technologies, adns-7700 Datasheet - Page 41

• Manufacturer Part Number: adns-7700
• Description: One Chip Usb Laserstream? Mouse Sensors
• Manufacturer: Avago Technologies

SQUAL
Access: Read Only
Data Type: Upper 8bits of a 10-bit unsigned integer
USAGE: SQUAL (Surface Quality) is a measure of ¼ of the number of valid features visible by the sensor in the current
Figure 23. SQUAL Values (white paper)
Figure 24. Mean SQUAL vs. Z (white paper)
41
Bit
Field
40
30
20
10
40
30
20
10
0
0
1
frame. Use the following formula to find the total number of valid features. The values range from 0 to 144.
Number of features = SQUAL register value * 4
Since small changes in the current frame can result in changes in SQUAL, slight variations in SQUAL on one
surface is 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 typi-
cally maximized when the navigation surface is at the optimum distance from the imaging lens (the nominal
Z-height).
1.6
51 101 151 201 251 301 351 401 451 501 551 601 651 701 751
7
SQ
1.8
Distance from Lens Reference Plane to Navigation Surface, Z (mm)
7
2
1000cpi, Circle@7.5" diameter, Speed = 6ips
Z = 2.4mm, Circle@7.5" diameter, Speed = 6ips
6
SQ
2.2
6
SQUAL vs Z (White Paper)
SQUAL Value (White Paper)
2.4
Count
Address: 0x08
Reset Value: Undefined
5
SQ
2.6
5
2.8
4
SQ
4
3
3.2
3
SQ
3.4
3
2
SQ
2
Avg-3sigma
Avg
Avg+3sigma
Type: Device
1
SQ
1
0
SQ
0