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Q & A: Modulation Transfer Function

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Most recent answer: 10/22/2007
Q:
What is modulation transfer function?
- Matt Smith (age 16)
Tyalla High school, Australia
A:
Hi Matt,

We aren't real experts on this -- we got our information on this from the web. Here is .

In short, the modulation transfer function describes how much a piece of optical equipment, say a collection of lenses and/or mirrors, blurs the image of an object. The lenses and mirrors may not be perfect, and even if they are, diffraction limits the ability to see finely spaced features. The standard test is to see how well alternating white and black stripes show up (that is, their contrast, the difference between the whitest white and teh blackest black) in the image, depending on how finely spaced they are. Widely spaced features, such as broad stripes, don't lose much contrast, since a little blurring only affects their edges. Stripes that are fine enough will appear to be a uniform gray after being blurred by the optical apparatus being tested.

The modulation transfer function appears to be a measure of how much bright-to-dark contrast is lost, as a function of the width of the stripes, as the light goes through the optics. So it might be 1.0 for broad stripes, which are not significantly blurred, and 0.1 for ones almost too narrow to be viewed with the optics.

Gloria, Mike, and Tom

(published on 10/22/2007)

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