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Advanced Imaging Magazine

Updated: July 8th, 2008 05:26 PM CDT

CCD Camera Parameters to Consider in Machine Vision

An Overview of Camera Considerations and Imaging Issues
Adimec
Adimec
Fig. 1: Multiple tap camera.
Fig. 2: Recombination of 2 image halves.
Fig. 3: Smear.
Fig. 4: Blooming.
Fig. 5: Granular Effect due difference in the average dark current of photodiodes.
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By Miriam van Baalen and Gretchen Alper, Adimec

There are many different industrial video cameras for machine vision available. The perfect camera does not exist for all applications because optimizing every parameter is not possible (or profitable). As a result, every camera manufacturer makes choices to optimize the camera performance for certain applications. Camera specifications can be reported differently making it difficult to decipher the real differences between different manufacturers. The following sections explain some key parameters to consider in machine vision and how these can influence different applications.

Camera Speed

Camera speed is defined as the number of frames a camera can deliver each second. The speed of the camera can be reported for a portion of the image, such as using partial scanning or binning. This value will be greater than the number of "full" frames per second, which is the number of frames of the full resolution of the camera that are output per second.

Throughput is a key performance indicator in almost all of the machine vision applications. When the camera speed is the determining factor for throughput in a system, a higher camera speed results in a higher throughput for the system. Even one additional frame per second can have a significant effect.

A high camera speed can also allow you to improve the accuracy of a system by obtaining multiple images of one object very quickly to avoid errors that could arise from having just one image of the object.

In order to obtain the fastest cameras possible, the manufacturer must understand the sensor and maximize the output of the sensor without taking risks. One of the commonly known tools to increase the camera speed is the use of multiple tap sensors, but there can be some side effects.

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