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# Camera calculator - Calculating the sensor exposure time

The calculation of the correct exposure time in case of moving parts prevents blurred images. They are produced when the pixels shift in the range of the camera while being exposed. Depending on the application, different tolerances are possible. A smear effect of 1 pixel is not visible to the eye most of the time, however, it still affects precision measurement results. Yet this value is acceptable for many standard applications. Useful exposure times for CCD cameras are between 50 µs to maximally 500 ms. Typical values in practice for "normal applications" are mainly between 0.1 and 20 ms. Using CMOS sensors, shorter exposure times of up to 1 µs can be realised, too.

If the exposure time calculation gives greater values (e.g. 50 ms), it is of course possible to use a shorter exposure time (e.g. 5 ms) if there is sufficient light. Longer exposure times are also to be avoided as vibrations can also become visible in the image.

## Calculation of sensor exposure time for translational part movements (conveyor belt) using area scan cameras

Please use this calculation method for linear part movements.

Note: Even when using the drop-down lists own values can be entered. Please use the first entry "user def."!

 Sensor size in pixels (in the transport direction of conveyor belt): User def. (px) 240 px 320 px 480 px 512 px 640 px 800 px 1024 px 1280 px 1400 px 1600 px 2048 px 2452 px 3200 px 4096 px 4872 px 6144 px 8192 px 12288 px Max allowed image blur in pixels: User def. (pix) 0.1 px 1/4 px 1/2 px 3/4 px 1 px 1 1/2 px 2 px 3 px 4 px Part size or field of view in mm:: Conveyor belt speed in mm / sec: Maximum exposure time for camera:

Further explanations and details on these calculations can be found in chapter "Exposure times for area scan cameras".

## Calculating the sensor exposure time for the inspection of revolving objects using area scan cameras

The calculation of the proper exposure time is also possible with rotary movements, where cylindrical objects are inspected with an area scan camera. A possible example would be reading a data matrix code on a cylindrical component, which is rotated in front of the camera until the code has been read in by the machine vision system.

Please note that with larger angles for the arc of circle, perspective shortenings occur at the edge of the arc, which are not taken into account for the calculation. Changes in the magnification due to different working distances are also ignored.

Note: Even when using the drop-down lists own values can be entered. Please use the first entry "user def."!

 Sensor size in pixels (in the transport direction of conveyor belt): User def. (px) 240 px 320 px 480 px 512 px 640 px 800 px 1024 px 1280 px 1400 px 1600 px 2048 px 2452 px 3200 px 4096 px 4872 px 6144 px 8192 px 12288 px Max allowed image blur in pixels: User def. (pix) 0.1 px 1/4 px 1/2 px 3/4 px 1 px 1 1/2 px 2 px 3 px 4 px Field of view in mm: Complete part diameter in mm: Revolutions of part/ sec : Total circumference of part: Length of arc: Height arc segment (> depth of field!): Angle of arc segment: Maximum exposure time for camera:

Attention: Ideally, inspections of cylindrical objects are done with the help of line scan cameras. Further explanations can be found in chapter Line scan cameras.