Image trigger (image processing)
An image trigger triggers the recording of one or more images by evaluating the electronic signals from the recording sensor of a digital camera.
Modern high-speed cameras are increasingly being used to record and analyze fast-moving objects (for example, in checking for errors on a production line) . It is necessary to trigger the recording of an image series as soon as the object appears completely in the live image of the camera. This is usually attempted with the help of light barriers that generate the trigger pulse as soon as the object moves through. In recording situations with strongly fluctuating object or transport speed, however, problems arise in actually holding the parts to be inspected synchronously in the image at the right moment. Exact image triggering would only be possible through the time-consuming and costly use of additional sensors .
The use of the image trigger solves this task more quickly and with greater accuracy, without causing additional installation work. The "ImageBLITZ" image trigger integrated in high-speed cameras uses the live image of the camera itself as a rapidly reacting sensor that can be varied as required .
Cameras in CMOS technology are used here, in which the content of each individual pixel is already available in digitized form and thus a quick evaluation of the image information is possible. Individual memory cells that are adjacent to one another can also be read out at high speed.
A line segment of a definable length is positioned in the image field - where the trigger event will be seen. The amount of the gray value change is determined and whether there should be a change in the direction of dark or light. To do this, it is specified how many pixels of the line should be affected.
For each trigger event determined in this way, the camera sends an image (or a series of images) to the connected computer, in which it is further processed by an image processing program or can be saved for archiving.