Overview (Aca2500-14 Only) - Basler Ace User Manual

AW00123401000 Camera Functional Description
4.2 Overview
(acA2500-14 Only)
The camera provides features such as an electronic rolling shutter and electronic exposure time
control.
Exposure start and exposure time can be controlled by parameters transmitted to the camera via
the Basler pylon API and the GigE interface. There are also parameters available to set the camera
for single frame acquisition or continuous frame acquisition.
Exposure start can also be controlled via an externally generated "frame start trigger" (ExFSTrig)
signal applied to the camera's input line. The ExFSTrig signal facilitates periodic or non-periodic
frame acquisition start.
Because the camera has a rolling shutter, the exposure start signal will only start exposure of the
first row of pixels in the sensor. Exposure of each subsequent row will then automatically begin with
an increasing temporal shift for each row. The exposure time will be equal for each row.
Accumulated charges are read out of each sensor when exposure ends. At readout, accumulated
charges are transported from the row's light-sensitive elements (pixels) to the analog processing
controls (see Figure 13 on page 26). As the charges move through the analog controls, they are
converted to voltages proportional to the size of each charge. Each voltage is then amplified by a
Variable Gain Control (VGC). Next the voltages are digitized by an Analog-to-Digital converter
(ADC). After the voltages have been amplified and digitized, they are passed through the sensor's
digital controls for additional signal processing. The digitized pixel data leaves the sensor, passes
through an FPGA, and moves into an image buffer.
The pixel data leaves the image buffer and passes back through the FPGA to a controller where it
is assembled into data packets. The packets are then transmitted by bulk transfer via a USB 3
compliant cable to a USB 3 host adapter of the host PC. The controller also handles transmission
and receipt of control data such as changes to the camera's parameters.
The image buffer between the sensor and the controller allows data to be read out of the sensor at
a rate that is independent of the data transmission rate between the camera and the host PC. This
ensures that the data transmission rate has no influence on image quality.
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