Allied Vision Technologies MF-145B2 Instruction Manual download pdf (Page 64)

Controlling image capture

MARLIN Technical Manual

Page 56

9.1 Exposure time

The exposure (shutter) time for continuous mode and Trigger_Mode_0 is based on the following

formula:

Shutter register value x timebase + offset

The register value is the value set in the corresponding IIDC register (SHUTTER [81Ch]). This

number is in the range between 1 and 4095.

The shutter register value is multiplied by the time base register value (see TIMEBASE). The

default value here is set to 20 µs.

A camera-specific offset of 24 to 43 µs is also added to this value.

Example

Camera: MF-033

Timebase: 20 µs

100 x 20 µs + 24 µs = 2024 µs exposure time.

The minimum adjustable exposure time set by register is 10 µs. => the real minimum exposure

time of an MF-033 is then 10 µs + 24 µs = 34 µs.

9.1.1 Extended shutter

The exposure time for long-term integration of up to 67 sec can be extended via the

EXTENDED_SHUTTER register.

Offset Name Field Bit Description

0xF100020C EXTD_SHUTTER Presence_Inq [0] Indicates presence

of this feature

(read only)

--- [1.. 5]

ExpTime [6..31] Exposure time in

µs

Table 28: Extended shutter configuration

The longest exposure time, 3FFFFFFh, corresponds to 67.11 sec.

 Exposure times entered via the 81Ch register are mirrored in the extended register, but

not vice versa.

 Longer integration times not only increase sensitivity, but also may increase some

unwanted effects such as noise and pixel-to-pixel nonuniformity. Depending on the

application, these effects may limit the longest useable integration time.

 Changes in this register have immediate effect, even when the camera is transmitting.

 Extended shutter becomes inactive after writing to a format/mode/framerate register.

1 2 ... 59 60 61 62 63 64 65 66 67 68 69 ... 130 131

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Allied Vision Technologies MF-145B2 Instruction Manual Page 64