Applying optical inspection to process control problems can often become encumbered by the required size and weight of the optical system and lens. Although it may be desirable to mount the camera and lens off of the machinery being controlled for mechanical stability, this creates a problem in relating the machine position to the image of the part being processed. By employing a relay optical system on the machine or other moving apparatus, in conjunction with a mechanically decoupled imaging system on the camera, the image can be coupled with the machine motion, while still producing a stable image on the separately mounted video camera. The relay system can translate in X,Y, or Z without moving the video image. Another potential application of this optical design is the overlay of two separated images, each captured with a separate relay system. The resulting image will show the two scenes stability superimposed on top of one another on the video camera, independent of the relative position between the two relay systems. We will discuss variations of the optical design, and the limitations imposed by the use of this design on the overall optical performance.
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