Camera Parameters; Pixel Clock, Frame Rate, Exposure Time; Gain And Offset - IDS uEye series User Manual

6.3

Camera Parameters

6.3.1

Pixel Clock, Frame Rate, Exposure Time

Pixel clock
The basic parameter for camera timing is the pixel clock. It determines the speed at which the
sensor cells can be read out.
Frame rate
The possible range of settings for the frame rate depends on the currently selected pixel clock. You
can select a lower frame rate without changing the pixel clock. To set a higher frame rate, however,
you need to increase the pixel clock.
Exposure time
The exposure time depends on the currently selected frame rate and is preset to its reciprocal value.
You can select a shorter exposure time without changing the frame rate. To set a longer exposure
time, however, you need to reduce the frame rate.
6.3.2

Gain and Offset

Gain
In digital imaging, a voltage proportional to the amount of incident light is output by the sensor. To
increase image brightness and contrast, this signal can be amplified by an analog gain and offset
before the digitizing process. The results of analog signal processing are usually better than the
results of digital post-processing.
Analog amplification of the read-out pixel values increases overall image brightness and contrast.
Depending on the sensor type, a global gain value for all pixels (master gain) or a separate gain value
for each color (RGB gain) can be set.
Offset
Every digital image sensor has light-insensitive cells next to the active image area. These dark pixels
are used to measure a reference voltage (black level) which is subtracted from the image signal.
This compensates thermally generated voltages on the sensor which would otherwise falsify the
© 2009 IDS Imaging Development Systems GmbH
We recommend not setting the pixel clock any higher than necessary to achieve the
desired frame rate.
An excessive pixel clock can cause transmission errors or delays. If the data is read from
the sensor at a higher speed (high pixel clock), you will also need a faster transmission
over the data connection. Thus, by controlling the pixel clock, you can also influence the
bandwidth required for a camera.
The pixel clock influences the connected load and consequently the temperature inside
the camera.
A signal gain will also result in a noise gain. High gain settings are therefore not
recommended.
We suggest the following gain settings:
1. Enable the Gain b oost function.
2. If required, adjust the gain setting with the master gain control.
6 Camera Basics
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