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I decided that this is sort of a fundamental physics question regarding light and dimensional observation, so I decided to cross-post it in both this site and Physics SE (which is acceptable in stack exchange if the question is on topic for both sites) here and here.

Question:

Is it fundamentally possible to capture an orthographic image of the real world?

Detail:

I recently asked a question involving a stealth suit on Physics SE, and realized that "retro-reflective-panels" or panels that "reflect" their inverse, would require orthographic imaging to remain accurate.

Imagine a ball who's surface is evenly covered in octagonal high-definition display plates, where each plate has a twin plate on the opposite side of the ball. This is a simplistic model of the concept, but it demonstrates the idea. Each plate would record the scene in front of it via a micro camera at its center and feed that image to it's twin plate for display. But the image would be inaccurate unless recorded from an orthographic perspective, which I'm not sure is physically possible in the real world, hence this question.

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Different lens systems have different attributes. Most lenses used for photography show things that are closer as being larger - mostly because this is how we, humans, expect to see the image. These lenses are known as entocentric.

There are lenses known as telecentric lenses that can be designed with the property that that objects do not show any magnification based on their distance (flip side, there's also pericentric lenses which more distant objects appear magnified, but that's a tangent).

Telecentric lenses are used in processes involving machine vision, meteorology, and industrial processes (lithography).

Edmund Optics has an example of this and more detailed information at What is Telecentricity? which includes the following image:

enter image description here

Note with the telecentric lens, as described, the two objects are the same size which is independent from the distance they were photographed at.

Another useful tutorial on the telecentric lens design can be found at opto-engineering: Telecentric lenses tutorial: Basic information and working principles. This provides another telecentric photo on the right:

regular optics telecentric lens

Note the tube no longer shows the perspective and the background behind it is clearly visible.

Using a telecentric lens at an angle would then give the orthographic projection image on the media.

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  • The problem with using telecentric lenses to do what the question seeks is that since a telecentric lens must have a larger objective than the objects it is viewing, the lenses would need to be larger than the screens projecting the output from the corrosponding lens 180° on the other side.
    – Michael C
    Oct 25 '14 at 23:22
  • @MichaelClark yep. It's not practical at all (as mentioned in the Edmund video) - but the optics are there and it does have real world applications... and who knows, maybe it will inspire someone to do gun borehole photographs with a telecentric lens.
    – user13451
    Oct 25 '14 at 23:49
  • Neat so the answer is basically "yes..but: with the drawback that your camera needs to be the size (width / height) of the area that you want to capture." Perhaps the concept I was curious about could be achieved via a one-way screen, that let the camera view out, but anyone looking back towards it would see the image displayed. Sort of like a one way mirror. It's pretty far fetched.
    – J.Todd
    Oct 26 '14 at 0:28
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    @jt0dd your media needs to be at least the size... the lens will be even bigger.
    – user13451
    Oct 26 '14 at 0:30
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    With image transformation/processing, it may be possible to get a near orthographic image.
    – nvd
    Dec 11 '17 at 23:44
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Trivial no: If the scene is not flat, the paralex will of the camera's position will cause front objects to block back objects. If you move the camera to the orthogonal line to get that feature correct, you mess it up elsewhere in the scene. Unless the camera is infinitely far away, it can't be done. OTOH, the camera can be far enough away so that the differences are smaller than the resolution or the important features you care about.

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  • You did see that telecentric lenses do do this? They will render the scene as flat.
    – user13451
    Oct 27 '14 at 2:21

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