Timing is a highly critical factor in the industrial imaging sector. The final image may be influenced by a difference of just a few milliseconds of capturing a moving object. For instance, in applications such as speed enforcement traffic systems or factory inspection, if the exposure does not start accurately, the final image cannot be used.
While delays can be taken into account in the design of a system, the time elapsed between software or a hardware input that acts as a trigger, and the actual start and end of exposure is not always constant. It is tough to resolve any fluctuation and unavoidable issues may be caused in a vision system.
Timing Considerations in Machine Vision Cameras
These kinds of considerations are kept in mind only while designing machine vision cameras. Good quality machine vision cameras are capable of accepting hardware input triggers, such as TTL and optically isolated triggers and also a range of software triggers. This guarantees that there are a large number of alternatives available for a system to be interfaced with a camera.
Figure 1. Sample industrial inspection application
The cameras also behave as a vision system’s central intelligence, offering TTL-based or optically isolated output strobe signals with an accuracy on the order of microseconds, allowing the operator to fine-tune delays to match the lighting’s timing characteristics.
When an electronic trigger input signal is sent to an industrial camera, the camera will begin the image capture internally and will save it to its internal memory buffers. After completion of the image capture, the image is transmitted to the host computer, while it awaits further triggers. In this arrangement, any inherent variability in the host computer performance is effectively removed from the time-critical portion of the capture sequence.
It is also possible to configure machine vision cameras to send hardware triggers to external strobe devices using the same approach used by them for accepting an input trigger. By configuring exposure delay, strobe duration, and strobe delay variables, the exposure can be matched to the peak intensity of the lighting type because each lighting technology has different luminance output curves.
Lumenera strives to develop and manufacture cameras, which are not just the fastest in the industry but also the most deterministic and consistent. High frequency oscilloscopes are used to test all types of camera models and firmware offered by Lumenera with microsecond accuracy.
This information has been sourced, reviewed and adapted from materials provided by Lumenera Corporation.
For more information on this source, please visit Lumenera Corporation.