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Advanced Imaging Magazine

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

Image Sensors Speed Up Automated Inspection

Features
KAI-0340
Image Sensor Solutions, Eastman Kodak Co.
Kodak's high speed sensor, KAI-0340, is a 640 x 480, progressive scan, CCD image sensor. Image readout time is about 7 times faster with an image sensor such as this as compared to a standard RS-170 video camera.
KAI-1020
Image Sensor Solutions, Eastman Kodak Co.
High resolution sensors, such as Kodak's KAI-1020, have a larger field of view and allows for fewer images to be taken.
Graphic
Image Sensor Solutions, Eastman Kodak Co.
Graphic of the interline sensor structure.
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By Terry Guy

Machine-vision systems use a combination of lighting, optics, cameras, computers and processing software to inspect manufactured items for quality control purposes and are used extensively in the semiconductor and electronics manufacturer markets markets that require more inspection capabilities and faster throughput. Advances in sensor technology are improving a systems' capabilities to meet these users' needs.

Automated inspection systems are placed throughout the manufacturing process to help improve yield and quality. A key requirement and direction for automated inspection system suppliers is increased speed. Manufacturers measure speed as throughput or how many parts they can inspect per hour. This measure is important because automated inspection machines with higher throughput have faster payback times to their users, a key element in the sale of this equipment.

A typical inspection system is composed of two parts: a handling system for the item that is being inspected and a machine-vision system to determine if the item passes or fails the inspection. While there are several ways an automated inspection system supplier can increase the speed of their system, two key methods are to increase the speed of the handling system or to increase the speed of the machine-vision system.

The machine-vision system captures images of the item being inspected, and algorithms running in the computer determine if the item is good or bad. If the computer speed is increased or the algorithm optimized, an increase in speed from the machine-vision system can be accomplished. These improvements have occurred and will continue to occur as seen with increases in computer operating speeds.

Sensor Advancements

However, there is another way to realize an increase in speed and that is by decreasing the time of the image capture. The cameras frame rate is a measure of the camera capture speed and is often specified in frequency as hertz (Hz) or in image readout time (1/frequency). For example, a camera that is specified at a frame rate of 30 Hz means the image is read out in 33 milliseconds. This is the time it takes to transfer the image from the camera to the vision system.

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