Vga Monitor Output (A504K Only) - Basler A500k User Manual

Camera Interface

2.5.9 VGA Monitor Output (A504k Only)

The VGA monitor output transmits 640 x 480 pixels RGB at a rate of 60 Hz. To achieve this, the
image from the sensor (1280 x 1024 pixels) must be reduced. The first 32 lines and the last
32 lines of the image are not transmitted. Then, only every second pixel from the remaining
1280 x 960 pixels are transmitted to the VGA monitor output. The image on the monitor has a
resolution of 640 x 480 pixels.
To activate the VGA monitor output, the free-run VGA exposure mode must be selected. The VGA
exposure mode can only be used with a synchronous timing. In addition, it can only be operated
in free-run, which means that it can NOT be triggered externally. The data is output at the VGA
monitor connector and, at the same time, at the Camera Link output connectors.
When the camera is set to an exposure mode other than free-run VGA, a test image is output to
the VGA output. The test image consists of monochrome gray wedges.
Timing
The VGA exposure mode operates in a synchronous timing because the sensor timing must be
adapted to the frame and line frequencies required by the monitor. In synchronous timings, the
start of exposure is only possible at the falling edge of the line valid signal. In the VGA exposure
mode, this fixed time pattern continues even while frame valid and line valid are low. The line valid
signal period is 15.8 µs, so effective exposure is only possible in multiples of 15.8 µs, also while
line valid is low. Frame valid rises 34 µs after the internal control signal has risen. See Figure 2-14.
If the exposure time is set so that the exposure start signal falls exactly onto the end of a high line
valid signal, the effective exposure can jitter by 15.8 µs. To avoid this, change the exposure time
by 1 µs.
Figure 2-14: Output of VGA Exposure Mode
2-32
PRELIMINARY
waiting for
next pulse
effective exposure
k
Basler A500