31

Figure 28. Shutter Value (white paper)

Shutter_Upper

Address: 0x0f

Access: Read

Reset Value: 0x00

Bit

7

6

5

4

3

2

1

0

Field

Data Type: Sixteen bit unsigned integer.

USAGE: Units are clock cycles. Read Shutter_Upper first, then Shutter_Lower. They should be read consecutively. The

shutter is adjusted to keep the average and maximum pixel values within normal operating ranges. The shutter value

is checked and automatically adjusted to a new value if needed on every frame when operating in default mode.

When the shutter adjusts, it changes by ± 1/16 of the current value. The shutter value can be set manually by setting

the AGC mode to Disable using the Extended_Config register and writing to the Shutter_Maximum_Bound registers.

Because the automatic frame rate feature is related to shutter value. It may also be appropriate to enable the Fixed

Frame Rate mode using the Extended_Config register.

Shown below is a graph of 800 sequentially acquired shutter values, while the sensor was moved slowly over white

paper.

Shutter vs Z (White Paper)

Resolution = 3500cpi, Circle@7.5" diameter, Speed = 6ips

50

55

60

65

70

75

80

85

90

95

1.6

1.8

2

2.2

2.4

2.6

2.8

3

3.2

3.4

Distance from Lens Reference Plane to Navigation Surface, Z (mm)

Avg-3sigma

Avg

Avg+3sigma

Figure 29. Mean shutter vs. Z (white paper)

The maximum value of the shutter is dependent upon the setting in the Shutter_Max_Bound_Upper and Shutter_

Max_Bound_Lower registers.

Shutter Values (White Paper)

Z =2.4mm, Circle@7.5" diameter, Speed = 6ips

0

10

20

30

40

50

60

70

80

90

100

1

101

201

301

401

501

601

701

Counts

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PixArt Imaging Inc.

PixArt Imaging Inc.