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3.3 Exposure Time Control Modes in Detail
This section is aimed at system integrators or engineers who intend to develop their own
framegrabbers or preprocessing. If you are using a commercially available framegrabber, the
framegrabber takes care of the different timings described in this section without the need for any
action by you.
Depending on the frame rate and exposure time determined by setting the ExSync signal or the
Timer 1 and Timer 2 values, the timing of the exposure control signals differs. There are four
different timings and the camera switches between these four timings automatically.
This introductory section contains formulas that describe the conditions for the cam-
era to enter the four timings. The formulas were generalized as much as possible,
but the figures were taken from the Free-run mode. They can be different in other
exposure time control modes.
For detailed information, see the detailed timings described in sections
3.3.4.
Frame Valid High is 2000 µs for the A504
Frame Period
• Asynchronous Timing: This is the slowest timing. This timing is always used for the first
image. You can realize a long exposure time with this timing. Exposure and readout are per-
formed sequentially. Exposure starts after frame transfer, that is, while frame valid is low.
Readout of the next frame is triggered after transmission of the last frame, that is, while
frame valid is low. To let the camera remain in this timing, set the frame rate and the expo-
sure time so that the following condition is given:
The asynchronous timing is described in more detail in sections 3.3.1.1, 3.3.2.1, 3.3.3.1, and
3.3.4.1
for each exposure mode.
• Synchronous/Asynchronous Timing: This timing is suitable for long exposure times.
Exposure starts during frame transfer, that is, while frame valid is high. Readout of the next
frame is triggered after transmission of the last frame, that is, while frame valid is low.
To make the camera enter this timing, set the frame rate and the exposure time so that the
following conditions are given:
The synchronous/asynchronous timing is described in sections 3.3.2.2, 3.3.3.2, and
for each exposure mode.
• Synchronous Timing 1: The time that frame valid is low between two subsequent frames
corresponds to the time of one and a half lines. Exposure starts during frame transfer, that is,
while frame valid is high. Readout of the last frame acquired is triggered during transmission
of the last line of the frame being read out at present, that is, while frame valid and line valid
of the last line are high. To make the camera enter this timing, set the frame rate and the
exposure time so that the following conditions are given:
k
Basler A500
PRELIMINARY
1
=
------------------------------ -
Frame Rate
Frame Period
>
Exposure Time
<
Frame Period Exposure Time
>
Frame Period Frame Valid High
<
Frame Period Frame Valid High
>
Frame Period Frame Valid High
and 13.517 ms for the A501
k/kc
+
Frame Valid High
+
Frame Valid High
+
3 µs for A504k/kc (or + 20.2 µs for A501k/kc)
3 µs for A504k/kc (or + 20.2 µs for A501k/kc)
+
+
44 ns for A504 (or 300 ns for A501)
Basic Operation and Features
3.3.1
through
.
k/kc
3.3.4.2
3-7
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