Contamination Analysis for Optics and Imaging Systems
Expert Analysis
Imaging systems can be thought of as light gathering devices. They function by taking in reflected rays of light. The ray of light enters through the pupil and passes through the elements (lenses and mirrors) of the imaging device. In a perfect system, rays of light from a point on an object is designed to strike a particular point on the sensor yielding an image of the object. Each imaging device has imperfections that cause light from a point to spread.
Figure 1 shows images of two edge targets (objects) taken with a clean and dirty mirror in the imaging path.
Figure 2 shows the Edge Spread Function for the Clean Edge and Dirty Edge images.
In the manufacturing of imaging devices, dust and organic films that deposit optical surfaces are avoidable imperfections that degrade the quality of the device. This is shown in Figure 1 where an image of an edge target was taken with a mirror in the imaging path. Left image "Clean Edge" shows the image with the mirror clean. In contrast, the right image was sprinkled with fine particulates. The effect of the surface contamination on the image as seen by the sensor is shown in the image Edge Spread Functions shown in Figure 2. Contamination has the effect of reducing the dynamic range of the sensor. . The net effect is that Dirty Edge image has lower contrast. The reduction in contrast can be shown to be a function of the spatial frequency of the images. Analysis of the Point Spread Function (PSF) and the Modulation Transfer Function (MTF) can help diagnose the effect the contamination on sensor resolution.
This consultant has a strong set of analytical tools to diagnose the cleanliness of your manufacturing facility and your imaging system. This consultant can help you determine if contamination will result in a problem and needs to be corrected or if the contamination is not a problem and represents an opportunity for cost savings. We can help with the cleaning and process development for correcting complex cleaning problems. Some of the tools include modeling particle redistribution, outgassing analysis, and clean room flow to mitigate contamination events, process development and optimization for cleaning.
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