Testing Low Pass Optical Filter

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An optical low pass filter is designed to blur images through birefringence, primarily used in digital cameras for anti-aliasing. The user tested a filter removed from a camera by passing a diode laser beam through it, expecting to see a larger spot on the wall, but observed no difference compared to plain glass. Clarification was provided that this filter is distinct from the infrared filter, as they sometimes are glued together but serve different functions. The discussion emphasizes the challenge in visually distinguishing the optical low pass filter from regular glass. Understanding the specific properties and functions of these filters is crucial for effective testing and application.
optotinker
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An optical low pass filter is supposed to blur the image using birefringence. I took out an optical low pass filter from a digital camera where it is used for anti-aliasing purposes. The filter looks just like a piece of glass. I pass a diode laser beam through it and look at the beam spot on the wall. I was expecting it to be a bit larger than the laser spot without the filter. However I can't see any difference. How can I tell it apart from a piece of plain glass?
 
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optotinker said:
An optical low pass filter is supposed to blur the image using birefringence. I took out an optical low pass filter from a digital camera where it is used for anti-aliasing purposes. The filter looks just like a piece of glass. I pass a diode laser beam through it and look at the beam spot on the wall. I was expecting it to be a bit larger than the laser spot without the filter. However I can't see any difference. How can I tell it apart from a piece of plain glass?
Are you talking about the IR filter in Digital Cameras?
 
No, I am talking about the anti-aliasing filter. Sometimes they are glued together with the IR filter but serve an entirely different purpose.
 

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