In my optics classes, I have only ever seen magnification defined in conjunction with the thin lens equation.

However, in a lensless optical setup such as lensfree in-line holography, how does one understand the principle of magnification? I have seen both equations that define magnification in the setup below as:

M = Z2 / (Z1 + Z2)


M = Z2 / Z1

Which is correct? Also, what is the intuition behind this magnification?

In-line holography setup


1 Answer 1


The principle being used derives directly from the first lensless camera: the pin-hole camera. For the pin-hole camera the analysis is geometric ray optics; the ratio of the image distance to object distance is the same as the ratio of the image height to the object height, which is the definition of magnification.

See this introduction to the pin-hole camera.

Note that the formulas in the OP give the same magnification the limit of small $Z2$.


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