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If I'm understanding this right, a “hologram” is an ordinary black and white photograph that has been exposed in an extraordinary way. A normal image is exposed under white light, using a complicated system of lenses to try to make the light rays converge into a coherent image. If I understand correctly, a hologram involves illuminating a scene with two identical laser light sources, and having no lenses at all; the photographic system simply records the interference pattern of the two lasers (which depends on what they're illuminating, and hence records an image).

Now, presumably the size of the interference patterns is comparable to the wavelength of the light involved, which is where I suspect there might be a problem. For example, my camera has a dot-pitch of 5μm (and a Bayer filter). The wavelength of red light is more like 600nm or so, which is quite a bit smaller.

I gather normally they use glass plates coated in photographic emulsion, which presumably has considerably better spatial resolution.

So, in summary, can you make holograms with a DSLR? Has anybody done this? Or is it a fool's errand?

(Of course, assuming you manage to take the picture, printing it may also be... entertaining.)

  • From my hazy recall of making holograms at school, the two light sources hit the holographic transparency from two different sides (directions?) which is not possible in a DSLR. An simpler heuristic is: if it was possible, someone would be doing it already and we would have heard about it. – user1068122 Sep 13 '17 at 19:24
  • It should work,you take a camera with the lens removed and you'll get a digital recording of the interference pattern. You can then reproduce the hologram digitally by calculating the image you'd get from a certain vantage point if you were to shine light though the recorded interference pattern. – Count Iblis Sep 13 '17 at 20:23
  • (This is based on having made holograms as a kid using an SLR and film at my father's optics lab. It's possible holograms have moved on since then.) No. When a hologram is made using an SLR and film, it is the film itself that displays the hologram. Trying to "print" the film destroys it. A hologram is a set of tiny mirrors, each reflecting the light in a very specific way. Those "mirrors" are set at angles, meaning that the substance that holds them has to have depth. Film can record and hold this because it has genuine depth. Sensors and print don't: they just record what is on the surface. – Loop Space Sep 13 '17 at 21:16
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    @LoopSpace You comment is an answer and should be posted as such. Please see: Short answers as comments — please resist the urge – Michael C Sep 13 '17 at 21:51
  • while we can call silver halide crystals "mirrors", this is not really what makes the hologram work. the only requirement is that the single elements are very small, allowing for complex diffraction effects. they can be mirrors or transparencies, and yes, they CAN be enlarged (giving interesting effects with different wavelengths). they can even be digitally printed and digitally synthesized (without physical objects and recording any physical light). – szulat Sep 13 '17 at 22:28
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Apparently - yes, it is possible to use digital sensor, such as the one present in DSLRs to record holograms. Displaying or printing such holograms is of course another challenge. The examples I found focus on extracting 2D images from the recorded hologram (digital holography reconstruction).

Examples:

"Experimental device for recording the hologram using digital sensor" (image licensed under CC PD)

experimental device for recording the hologram using digital sensor (creative commons public domain)

  • Paraphrasing the first paragraph of the first link, it says "Holograms are possible if we redefine what a hologram is". I'm not an expert so can't comment for sure, but the first paper does not describe what I would consider to be a hologram. – Loop Space Sep 14 '17 at 16:38
  • me neither! and i was surprised people do such things using normal digital sensors, i was sure the resolution would be too low to record any meaningful interference patterns. but apparently, this is some form of holography. judging from the historical images made by the holography inventor (Gabor, 1948, see holocenter.org/what-is-holography ) it is almost exactly what he was doing back then. one thing that is different in those experiments is the sensor size - film hologram can "look" at the subject from many different angles, a small digital sensor cannot, because it is so small. – szulat Sep 14 '17 at 19:16
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Holography is a unique way to image objects and record them as three-dimensional pictures. The exposure is made utilizing photographic film. A coherent light is used. This is a light that outputs at a solitary frequency. A leaser outputs a coherent light beam. This beam, called the illumination beam is directed at the object.

A light sensitive photographic film, preferably an emulsion on a glass plate or on a stiff film base is placed so that reflected leaser light off of the object, plays on the plate.

The laser beam, on its way to illuminate the object is intercepted using a half-silvered mirror. Half of the beam continues on to illuminate the subject. The half that is reflected from this semi-silvered mirror is directed so that it plays on the light sensitive plate. This reflected light beam is called the reference beam.

The arrangement as above is configured in normal room light minus the light sensitive plate. The lights are turned off and in total darkness the plate is positioned. The laser is briefly turned on to make the exposure. This will be a trial-and-error timing of the duration of the laser exposure.

Once the film is exposed, it is developed as a negative or more likely as a positive (slide). When developed and dried, this hologram is illuminated from behind with a laser or perhaps a point-source light. A 3 dimensional image of the object is seen. The hologram image is formed by light inference action between the two laser lights, i.e. the illumination beam and the reference beam.

Could an SLR camera be used? We need darkened container to hold the film in place without exposing it. The camera body could serve and its shutter could be utilized to time the exposure. No camera lens is uses so the answer is, yes you can use a camera. You are after a device to hold film, keep it away from light until the exposure and you are after a shutter, that all you need.

I frankly have never used a DLSR to make a hologram. I don't known how you would view the image and get the needed interference pattern. As far as I know, film is it for holograms.

  • the question contains more of the answer than this answer, sorry :-( – szulat Sep 13 '17 at 21:09
  • @ szulat -- When I die, all that will remain will be a pile of trivia that mainly contains gobbledygook! – Alan Marcus Sep 13 '17 at 21:14

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