Re: diffraction curiosity questions

murrayatuptowngallery@xxxxxxxxx wrote:

Lastly, regarding the fact that a simple lens and a pinhole aperture
both invert an image, is either diffraction or the Fourier transform
the common factor causing the inversion. (I'm not entirely comfortable
with this question, as the phenomenon existed before the 'name'
Fourier transform became available...and thus may only be a model or
explanation for the phenomenon.

I was surprised that none of the responses in the newsgroup addresses this question, the simplest of them all.

Neither diffraction nor Fourier tr4ansformation causes the inversion. It is a simple matter of geometry, and best visualized if you consider a pinhole camera. A ray of light, say from the top of a tall tree, passes through the pinhole aperture or lens, and strikes the film plane near the bottom. A ray from the base of the tree passes through the same opening, and strikes the film at the top. The image is inverted, no?

Dave
.

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