Basic Operation And Features; Functional Description - Basler A500k User Manual

3 Basic Operation and Features

3.1 Functional Description

BASLER A500
a full frame shutter, electronic exposure time control and anti-blooming. Exposure time is
controlled either internally via an internal sync signal (free-run mode) or externally via an external
trigger (ExSync) signal. The ExSync signal facilitates periodic or non-periodic pixel readout.
In any free-run mode, the camera generates its own internal control signal and the internal signal
is used to control exposure and charge readout. When operating in free-run, the camera outputs
frames continuously.
The internally generated "effective exposure" signal (Integrate Enabled) can be tied to the
FlashOut signal (see sections
When exposure is controlled by an ExSync signal, exposure time can be either edge-controlled,
level-controlled or programmable. In edge-controlled mode, charge is accumulated from the rising
edge to the next rising edge of ExSync. The rising edge of ExSync also triggers the readout. In
level-controlled mode, charge is accumulated when the ExSync signal is low and a rising edge of
ExSync triggers the readout. In programmable mode, exposure time can be programmed to a
predetermined time period. In this case, exposure begins on the rising edge of ExSync and
accumulated charges are read out when the programmed exposure time ends.
The A504 has a special feature: In addition to sending video data to a frame grabber, it can be
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output to an VGA monitor (640 x 480 pixels). In VGA exposure mode the camera generates its
own internal control signal and the internal signal is used to control exposure and charge readout.
The frame frequency is set to 60 Hz. The camera outputs frames continuously to the monitor and,
at the same time, to the Camera Link output.
At readout, for A500
transported from the light-sensitive sensor elements (pixels) to the pixel memory (full frame
shutter). There is a pixel memory for each pixel. As a consequence, the camera can be exposed
and read out at the same time. The charges of the pixel memory are amplified. The pixel memories
can be connected to a bus. There is one bus for each vertical column. At the end of each bus,
there is an analog/digital converter (ADC).
For readout, the pixel memories can be addressed linewise by closing a switch that connects the
pixel memory of the addressed lines to the busses. Before the analog video data enters the ADC,
the offset is added, plus a value that corrects column fixed pattern noise. The analog video data
is digitized by a ten bit, Analog to Digital converter (ADC). The ADC's reference value is used to
set the gain. The digitized video data then passes a digital 128 stage shift register, which outputs
10 x 10 Bit of data in parallel with each cycle. Then the 10 Bit sensor output enters the digital shifter
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Basler A500
PRELIMINARY
area scan cameras employ a CMOS-sensor chip which provides features such as
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2.1.4 and 4.2.4.16).
series cameras, all accumulated charges of all pixels are simultaneously
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Basic Operation and Features
3-1