Camera Functional Description; Overview - Basler Pioneer User Manual

Camera Functional Description

8 Camera Functional
Description
This section provides an overview of the camera's functionality from a system perspective. The
overview will aid your understanding when you read the more detailed information included in the
next sections of the user's manual.

8.1 Overview

Each camera provides features such as a full frame shutter and electronic exposure time control.
Exposure start, exposure time, and charge readout 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 hardware trigger (ExTrig) signal.
The ExTrig signal facilitates periodic or non-periodic acquisition start. Modes are available that
allow the length of exposure time to be directly controlled by the ExTrig signal or to be set for a pre-
programmed period of time.
Accumulated charges are read out of the sensor when exposure ends. At readout, the accumulated
charges are transported from the sensor's light-sensitive elements (pixels) to its vertical shift
registers (see Figure 22 on page 98). The charges from the bottom line of pixels in the array are
then moved to two horizontal shift registers as shown in the figure. Charges from the left half of the
line are moved to the left horizontal shift register and charges from the right half of the line are
moved to the right horizontal shift register. The left horizontal shift register shifts out charges from
left to right, that is, pixel 1, pixel 2, pixel 3, and so on. The right horizontal shift register shifts out
charges from right to left, that is, pixel n, pixel n-1, pixel n-2, and so on (where n is the last pixel in
a line).
As the charges move out of the horizontal shift registers, they are converted to voltages proportional
to the size of each charge. Each voltage is then amplified by a Variable Gain Control (VGC) and
digitized by an Analog-to-Digital converter (ADC). For optimal digitization, gain and black level can
be adjusted by setting camera parameters. After each voltage has been amplified and digitized, it
passes through an FPGA and into an image buffer. As the pixel data passes through the FPGA, it
is reordered so that the pixel data for each line will be transmitted from the camera in ascending
order from pixel 1 through pixel n. All shifting is clocked according to the camera's internal data rate.
Shifting continues in a line-by-line fashion until all image data has been read out of the sensor.
The pixel data leaves the image buffer and passes back through the FPGA to an Ethernet controller
where it is assembled into data packets. The packets are then transmitted via an Ethernet network
to a network adapter in the host PC. The Ethernet controller also handles transmission and receipt
of control data such as changes to the camera's parameters.
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