Voyager's EMH is apparently simply a collection of photons and force fields, controlled by a computer, either on board Voyager or in his mobile emitter. Yet he seems to see and hear things from the perspective of where his holographic eyes and ears are, even to the point of reading printed text (as in the Season 5 episode "Warhead" where a sentient missile has taken over the Doctor's holomatrix and reads information off a screen). How does this work?

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    Very well, thank you
    – HorusKol
    Commented Feb 25, 2020 at 9:39
  • I imagine this works the same way any NPC in any game "sees": He is given the data he needs from the computer, which has sensors to see for him.
    – Philipp
    Commented Feb 25, 2020 at 13:07
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    But, how about the mobile emitter? Does it also have all the sensors the ship computer does?
    – Hans Olo
    Commented Feb 25, 2020 at 14:00
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    Vision from the same perspective as human eyes is definitely available with the mobile emitter as S7:E24 Renaissance Man shows the Overlookers' screen a few times, as they're watching a Doctor's-eye-view perspective.
    – David Buck
    Commented Mar 7, 2020 at 14:52
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    @PatDobson Only after getting the mobile emitter, which is 29th century technology, five hundred years more advanced than the baseline technology of the show. Prior to that, all the technology that supports his existence is part of the ship. The mobile emitter by necessity has to all the same work, just via a much, much smaller package.
    – T.J.L.
    Commented May 21, 2021 at 19:21

2 Answers 2


The EMH like other holograms possesses a hardened form that allows it to hold devices and touch surfaces. This hardening implies the hologram has a complex matrix that can emulate physical things like visual and aural sensors. The hardening need not be permanent. There are scenes where things sometimes pass through the holograms.

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    Do you have any evidence for this theory, as opposed to the one given in the comments that the EMH doesn't need to have functioning eyes because the ship's sensors provide that?
    – DavidW
    Commented Jun 7, 2022 at 3:31
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    The doctor demonstrates this in "Phage" (S01E05). Neelix has his lungs stolen and the EMH temporarily replaces them with holographic lungs. Another character asks how they can work, and the doctor responds by slapping him the face and explaining that, like the doctor's hand, the holographic lungs can be given enough physical presence to do their "normal" function. Obviously eyes are different to lungs, but both functions require part of the hologram to interact with matter on a small scale. Commented Jun 7, 2022 at 9:21
  • Would this "hardened form" be a result of the force fields mentioned in the original question?
    – FreeMan
    Commented Jun 7, 2022 at 15:25

Season 3 Episode 24 of Voyager "Displaced" actually delves into this a fair bit.

After the crew is abducted without any tricorders or other equipment they escape by adjusting The Doctor's "optical sensors" via the mobile emitter to allow him to see thermal energy and find the microwave signature of a portal through a field around their prison.

The scene comes complete with a short first person shot which appears to indicate his optical sensors generate an image imitating that of human vision.

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    I'm shocked Starfleet would not have infrared/ temperature seeing as default. Think of the feverish foreheads he could be looking at. Commented Jul 7, 2022 at 20:17
  • Some screenshots and a transcript would massively improve this answer
    – Valorum
    Commented Jul 8, 2022 at 7:02
  • I had a go at screenshots but Netflix spat back blackness
    – IG_42
    Commented Jul 8, 2022 at 16:09

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