Camera Functional Description; Overview For Cameras With Ccd Sensor - Basler acA2040-55 User Manual

AW00123409000
4 Camera Functional
Description
This chapter 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
later chapters of the user's manual.
4.1 Overview for Cameras with CCD
Sensor
Cameras with CCD sensor are listed in Section 1.3.1 on
The cameras provide features such as global 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 USB 3.0 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" signal applied
to a camera input line (hardware frame start trigger; HWFSTrig). The HWFSTrig signal facilitates
periodic or non-periodic frame acquisition start. Exposure modes are available that allow the length
of exposure time to be set for a pre-programmed period of time or to be directly controlled by the
HWFSTrig signal.
Accumulated charges are read out of the sensor when exposure ends. At readout, accumulated
charges are transported from the sensor's light-sensitive elements (pixels) to the vertical shift
registers (see Figure 34 on
then moved into a horizontal shift register. Next, the charges are shifted out of the horizontal
register. All shifting is clocked according to the camera's internal data rate. Shifting continues in a
row-wise fashion until all image data has been read out of the sensor.
As the charges move out of the horizontal shift register, 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). After each voltage has been amplified and
digitized, it passes through an FPGA and 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 computer. 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 computer.
This ensures that the data transmission rate has no influence on image quality.
Basler ace USB 3.0
page 64). The charges from the bottom row of pixels in the array are

Camera Functional Description

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