xiMU - Technical Manual Version 2.10
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4.4.3.
How to Freeze the Motion
When a moving object (e.g. on a conveyor belt) is imaged with a longer exposure time, the resulting image will show Motion Blur.
To avoid Motion Blur the short exposure times or flash illumination should be used.
Example of a setup with MU9 camera:
Sensor width (W) 0.0057m
2520 pixel horizontally (PX)
Field of view (FOV) 0.2m
Conveyor speed (CS) 0.1m/s
To contain Motion Blur to within one image pixel the following calculation for the flash light duration may be used:
Pixel distance (PD) W/PX -> 0.0057m/2592pixels = 2.2um.
Pixel distance recalculated FOVPD = FOV/PX = 0.2m/2592 = 77.2um
During exposure the object should not move more than 77.2um
Flash Time (FT) should be less than FOVPD/CS = 77.2um/0.1m/s = 0.772ms
4.5.
Camera Parameters and Features
4.5.1.
Exposure
Also known as shutter speed. This parameter defines the length of the integration period for each frame.
Most of CMOS sensors generate the exposure interval internally. For some it is possible to control it by external signaling. The
sensor internal timing depends on the provided system clock. Most sensors are using dividers to generate slower clocks for
internal usage.
The exposure time is mostly defined by number row times, where the row time is dependent on various internal settings. Very few
sensors support exposure times equal to zero. There is defined minimal exposure time as well as steps between possible
exposure times.
4.5.2.
Gain
The gain value influences the analog-to-digital conversion process of the image sensor pipeline and acts as a multiplier of the
output signal. Using gain values greater than 0 will increase the pixel intensities but may also increase the overall noise level.
4.6.
Host-Assisted Image Processing Parameters Available in xiAPI.
4.6.1.
Auto Exposure
–
Auto Gain
When AEAG is used, every captured image is evaluated for its mean intensity. Based on the result, the exposure and gain values
are modified with the objective to achieve a target intensity level for the following image. Further, the maximum applicable
exposure and gain values can be defined. Since both, exposure and gain, have an influence on the intensity, the ratio between
those two parameters in their contribution to the algorithm can also be set (exposure priority).
4.6.2.
White Balance
Only for color models: The white balance can be adjusted with three coefficients kR, kG and kB, one for each color channel.
These coefficients can be set individually in order to increase or decrease each channel’s contribution and therefore allow t
he
user to control the color tint of the image.
4.6.2.1.
Assisted Manual White Balance
This feature measures the white balance a single time and sets the white balance coefficient to achieve a mean grey (neutral) tint.
