In my fictional world I would like to have something similar to modern optical sensors for things such as aiming systems, night-vision goggles and automaton vision.

The main problem I face is developing an interface between optics and the algorithms to evaluate them.

In modern technology one would have an optical sensor, consisting of multiple components that produce an electrical signal representing the vision. This electrical representation can then be fed into a 'black box that figures it all out'.

In my world however electric circuits are effectively non-existent due to a lack of research and expertise, while mechanical computation (similar to the Analytical Engine) has successfully been miniaturised and optimised to be small, fast and complex enough to support an effective AI-ruler with a mere dozen cathedral-sized halls filled with calculation banks and stores.

The size or cost of the contraptions required is not important.

The usage of biological components (such as real eyes or well-trained dogs) could be begrudgingly accepted, as long as the systems result in a mechanical output.

PS: The things I would like to use this for are (with real-life examples in brackets):

  • Vision enhancement (night/infrared vision)
  • Vision replacement (prosthetic eyes)
  • Auto-focus (self-adjusting binoculars)
  • Image analysis (colour recognition)
  • Object recognition (facial recognition)
  • Object tracking (self-aiming turrets)
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    $\begingroup$ Each of the functions you listed is a question on its own. Please split them down. $\endgroup$
    – L.Dutch
    Commented Dec 31, 2018 at 12:11
  • $\begingroup$ This list of features may work better if split into several questions - e.g. enhanced vision for sighted humans, replacement vision for blind humans (needs to connect to nervous system...), strictly mechanical vision (automatons, gun turrets, doors?) etc. - As it stands, it'll be difficult to judge answers that doesn't cover all bases with the same thoroughness... You can add links between the questions to help answerer's / readers find the rest of the series. $\endgroup$
    – G0BLiN
    Commented Dec 31, 2018 at 12:13
  • $\begingroup$ What technologies has your fictional world (except for fuel burning engines)? $\endgroup$
    – Soan
    Commented Dec 31, 2018 at 12:14
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    $\begingroup$ Most of them would be well served by suitably trained pigeons. Can you explain why you have radio (involving thermionic valves presumably) but your AI works by diesel. Is it a Babbage machine? If it is then it will work incredibly slowly. $\endgroup$ Commented Dec 31, 2018 at 12:14
  • $\begingroup$ An AI of any complexity requires transistors and integrated circuits or very close analogue. Any device that operates at a quantum scale, as a translator does, are by nature light sensitive, which is partially why they are wrapped in creaming and epoxy $\endgroup$
    – pojo-guy
    Commented Dec 31, 2018 at 12:33

6 Answers 6


Let's have some fun with this. Now, disclaimer, I'm going to utterly ignore vision replacement, image analysis, and object recognition because I frankly don't believe there's a path from here to there. Hopefully smarter people than I can come up with a believable solution for those, but I can't.

And the idea of putting a key in your prosthetic eye to wind a spring... and then the awful tinnitus you'd experience from the whirring machinery... and your vision would jiggle...

The rest, I believe, is just a matter of creative chemistry.

Light enhancement When I lived in New Mexico, I had a friend in the military who explained the night vision (infrared) goggles he was using. He was no engineer, and so couldn't explain the chemistry involved, but the goggles were entirely passive. They acted as both enhancers and discriminators. The goggles were multi-layered. Some layers filtered out the ambient "we don't want to see that" light while others shifted the frequency of the "light we want to see" into the visible spectrum. Were they as useful/good/efficient as powered goggles? Absolutely not! But they worked....

There are a number of light-sensitive chemicals in the world. If you had a thin enough layer of a sensitive-enough chemical, it would be believable that the layer would illuminate somewhat like the electron-sensitive cathode-ray tubes of yesteryear (the electrons would impact on phosphorous and make it glow). If you had an initial layer that acted as a collimator to focus the light into narrow patches of that sensitive layer, then you'd get crude "dots." If you consider this, there are fluorescent collimators used for overhead lighting. They are covers, divided into grids, and often laminated with a lightly reflective material. The result is light focused more directly downward while blocking acute-angle observation of the source. (Granted, applying the word "collimator" to that description is a bit of a flourish... but it works.)

So, no sensor required for light enhancement.

Object tracking is a bit more complex, but not impossible. Unfortunately, you're in a mechanical and chemical world, which means you have no way to create a reference of your target in software. But, what you could do is use some refracting mirrors that reflect the image "seen" by the turrent onto what at the moment we'll call a piece of paper. You can do this with simple optics and artists have been doing it for a honking long time. There are actually "projectors" that people use to do this very thing — but I can't find a link with a quick Google search because projectors have become such a ubiquitous part of our lives they overwhelm the search. I haven't used one since grade school, cumbersome beasties.

Anyway, once you have the image someplace useful, we're back to chemistry. There is no way on earth that you can process 3D imagery using Victorian tech. Therefore, we're working with blobs, and the goal is to keep the blob in the center of the aiming reticle.

Here's where I wish I was a chemical engineer. Think of the old silver oxide photographic tech. You're going to get light and dark images. so, rather than having a piece of photo paper, you have some of that light-sensitive chemical in a grid where the piece of paper once resided. And below it, something that reacts to the presence of the light-sensitive chemical, only it's blocked by half. (hold your breath...) once someone screams "Mark!", the gunner shifts a lever that allows these chemicals to start "tracking."

What's really happening is that as the ratio of light-vs-dark changes on the half-plate below the gridded top-plate, the chemical reaction pulls or pushes (an incredibly light) lever, which trips gears to cause forward/reverse rotation. They'll jiggle back and forth with the shift in the light/dark pattern and, basically (and very roughly) hold the reticle "on target."

OBVIOUSLY there are tremendous real-life weaknesses with this.

  • The lever will be feather light, meaning you have a cascade of gears to get to the point where you can rotate a turrent. Considering you're bouncing around in a tank (I assume), the odds of this feather light contraption remaining calibrated (or even operational) are perishing awful.

  • The chemical-to-metal reaction that causes the metal to gently flex is most likely corrosive. You'll be replacing the lever frequently.

  • Fluids slosh...

  • IMHO, there is nowhere near enough tech to actually recognize a pattern. Thus, as you move around the battlefield, the light behind the target may change, forcing the gunner to regularly "reset" the system.

The problem with actual patten matching is that every time you change your angle of approach to the target, you're changing the reference image. In other words, you can't simply use a cutout as the reference. That would only work if the two of you were standing still — and you wouldn't need target tracking for that.

Last, but not least, is auto-focus. This one might actually be the simplest of the three... at least until you need to convert the results to mechanical action. There are several ways to achieve passive autofocus. I think the one that will work best is phase detection. We want to use a couple of pinholes (like the old artists used to capture an image to pain, earlier link).

enter image description here

Image care of the earlier Wiki link. Simplifying this something awful, you're trying to get only one glowing dot on your light-sensitive chemical, not two. But, think of it this way, if you have two small pools of chemical separated by a very thin barrier such that when you're in focus there is no dot, then all we need is a simple auger gear to move the focusing lense back and forth until the dot is gone. And that brings us back to the featherlight lever that warps with the chemical as the chemical reacts to light that I described for the turret.

But what about my computers?

OK, I'm having a bit of trouble working in the difference engines because I know what they are and how they work. They are NOT direct replacements for modern computers. Not by any stretch of the imagination. Did you ever see the movie Hidden Figures? That big-old honking IBM was basically a difference engine running ballistic math problems, and look at its size and complexity just to read punch cards. If you want a better example, watch The Imitation Game. Yeah, that big brick of an object running on a bazzilion electric motors that was parametrically programmable but not actually programmable? That's a modern babbage engine. Today a single microchip is many orders of magnitude more powerful — and we need multiple cores for decent image recognition. I, personally, can't choke down treating babbage engines as actual computers. They were large and complicated adding machines. Basically cash registers. Sorry. But that's why I haven't described how to create "software" for difference engines that would make your steampunk story look a bit more modern.


I think a believable set of solutions for the three desired outcomes I mention are obtainable. You'd need an actual Chem-E to work out the details — and it would be dog-slow and fragile! but it would work.

And once you have a believable solution, it's only a process of glass-blowing and a bit of handwaving to create working scenarios.

  • $\begingroup$ Thank you for your answer! The analytical engine, unlike the difference engine, was designed to be programmable via punch cards and being capable of storing information and doing more complicated tasks than basic arithmetics. Of course it was never built, but that is the inspiration I have built off of. $\endgroup$ Commented Dec 31, 2018 at 21:18
  • $\begingroup$ @JBH Your friend's night vision goggles are quite something, absorbing (infra-red) and then re-emitting photons at a higher energy (visible). Such probability defying physics would revolutionise energy generation and enable us to reverse entropy preventing the heat death of the universe. $\endgroup$ Commented Jan 1, 2019 at 13:33
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    $\begingroup$ @Duckisaduckisaduck, I wish I could have actuallly seen the glasses. Alas, I'm stuck as they weren't allowed off base. All I have is the descriptin he gave me. I knew how to ask the questions, but he was a grunt and was limited in his answers. On the other hand, frequency shifting is something done all the time in the electrical world. It doesn't revolutionize anything. There are always loses. The goggles, as described, did not create a higher energy output. They focused what input they had (not unlike electrons hitting those CRTs...). $\endgroup$
    – JBH
    Commented Jan 1, 2019 at 14:34
  • $\begingroup$ @JBH Oh, fair enough, if maybe there's some process to turn two or three infra red photons to one optical one, then I'm happy. Love to know how they work - could be classified though. $\endgroup$ Commented Jan 1, 2019 at 14:42
  • $\begingroup$ @Duckisaduckisaduck Photons are all the same, it's simply the frequency which is modulated. Similar to sound traveling through air, there are ways of changing sound (i.e. the shape of these waves) without changing the actual air. A typical example would be fluorescence, the glowing effect of certain materials under UV/'black' light. The UV waves are modulated down into the visible range and reflected by the materials resulting in the apparent glowing. $\endgroup$ Commented Jan 8, 2019 at 9:43

As far as I understand, you are quite out of luck with optical sensors in the Victorian era.

General overview

  • Photography and precursors is too slow.
  • Biohorror has trouble coupling with mechanical response mechanisms and is not stylish enough.
  • You can have very early and crude television efforts with tubes and mechanical scanlines. But...
  • You might have more luck with a radar. You'd basically need huge tubes, ask the British in WW2.

So, tubes are probably our best bet.


The problem with tubes in the Victorian era is that tubes are pretty much hardcore hightech. (Semiconductors are even more hightech, search for the purity of silicium for P- and N-doping.)

You'd need:

  • Some quite hard obtainable metals and rare earths. These alone mean decades on geological research and hardships of industrial production. How would you extract, say, wolfram in large quantities, if you have nothing that would reach its melting temperature outside from very exoctic labs?
  • Vacuum. Vacuum tubes need (surprise) vacuum, of a quite high stage for that time. A lot of work on pumps, ingenious tricks on burning up the remainder oxygen inside the tube need to be discovered.
  • Displays. Yeah, you radar display screen is a big-ass tube. But it's hard to fabricate and finding a proper luminophore is not easy.
  • Power source. You'd need quite some electrical power. Where are the generators?
  • Tube-based electronics needs some capacitors and a lot of transformers. Transformer steel is not that hard to produce as, say, cathodes, but still.
  • Theoretical foundations need to be developed, starting from Thermionic emission.

My verdict: It's so far from then-current state of the art, so esoteric, and so resource-hungry that you'd fail to convince anyone to invest money in such a project.

  • $\begingroup$ Radio and television worked entirely with vacuum tubes (a.k.a. thermionic valves) for decades. I still remember when my parents replaced our old vacuum tube-based TV set with a transistorized one (no more waiting one minte for the tubes to warm up! progress!). Vacuum tubes are not "hard-core high-tech", they can be made in the home; there are videos on YT showing how. And vacuum tubes don't need special kind of vacuum different from ordinary lightbulbs. $\endgroup$
    – AlexP
    Commented Dec 31, 2018 at 21:22
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    $\begingroup$ Show me lightbulbs in Victorian era. You'd need everything from pumps and glass to anode and cathode materials for tubes. Radio is soooooo 20th century, we are in 1837--1901. $\endgroup$ Commented Dec 31, 2018 at 21:42
  • $\begingroup$ Huh? Edison patented his lightbulbs in 1879, well within Victorian times. $\endgroup$
    – AlexP
    Commented Dec 31, 2018 at 21:52
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    $\begingroup$ Lightbulbs, but not tubes. And not the kind of tubes needed for radar. I'd expect ability to deliver a radar not during the WW2, but a decade before it. But not by 1900. $\endgroup$ Commented Dec 31, 2018 at 21:55

Light creates heat. Heat can be measured mechanically

It's just hard.

Consider, for example, the Crookes radiometer - one side of the little spinner is painted black, the other left shiny - it spins when you put it in sunlight.


There's also the Nichols radiometer, which uses a tiny silver mirror to measure the force exerted by light.

This requires extraordinary miniaturization, but we're already supposing this for the sake of the story.

Nanoscale rods with tiny silver mirrors could be hooked up to tiny gears that transfer photon collisions to the tiniest amount of mechanical rotation. And, if you build an array of them, you have something that you can use to see. It's not easy, but neither was the invention of the digital camera.

It'd be hard to use, vulnerable to vibrations, needing a load of balancing and compensation mechanisms, but you could do it

Once you have this level of miniaturization, though, other things get easier. Night vision? Well, your device is exquisitely sensitive to vibrations outside of it's shell. Why not use it to sense the vibration caused by creatures or humans walking?

Perfect for hooking up a turret. Having the turret understand a passphrase is comparatively laughably trivial



At least one "eye": Patented in 1885 by Flez Biological Mechanisms of Switzerland (Flez Biomechanische Technik AG), the standard Flez eye consists of a lens in front of a 20x20 grid of 400 "elements", each a dissected insect eye connected via its optic nerve to a small piece of muscular tissue. Light makes the muscle contract and (via a series of gears) extend a small metal rod. A scanning mechanism feels the pins and reports their positions to the "brain". This can be done eight times a second. The insect eyes, muscles, and nerves are bathed in a nutrient fluid which keeps them alive for up to a year, but can be damaged by excessive heat or cold. The basic "eye" costs £5. A model offering colour vision (via a rotating colour filter wheel) is available but costs £10 and slows updating of vision to twice a second. A model with three grids and fixed colour filters costs £20, and gives colour vision refreshing eight times a second, but the triple-lensed design looks very odd and cannot be used for models imitating humans. All models must be refilled with nutrient saline every week, at a cost of a few pence, and the eye elements must be refurbished by a Flez main dealer at intervals of six months to a year. Refurbishment of all models costs 20% of the cost of the eye. The illustrations above show the basic mechanism and an automaton's-eye view of the same illustration.

Recognition Q: How does an automaton recognise someone? A: With great difficulty Since automaton sight is so limited, they can rarely recognise anything more complex than the outline of a human, and can easily be fooled by something that distorts or imitates the human form. This means that the basic visual process must be augmented by other means if it is essntial for the automaton to distingush between one person and another; for example, if an automaton sentry is to distinguish friend and foe. Sound (such as a password) is one possibility, others include insignia with distinctive light and dark patterns, flashing lights, and magnetic tokens. Recognition methods are often closely-guarded secrets; for example, the British mechanical soldier "Automaton Atkins" (see below) obviously has some means of recognising fellow soldiers, possibly by their uniforms or some token concealed in it, but the exact method has never been publicised.If an automaton is being run as a player character it probably isn't a good idea to emphasise this problem too much. See below for more on automatons as player characters.


pigeon guided bombs were a thing.

trained pigeons are your sensor and they peck at a target image which moves the screen creating a mechanical input. link to a video about how they worked. The sensor for the movement of the screen by pecks was electrical but they could be made entirely mechanical.. enter image description here

you can also use photovoltaic materials,


Vision enhancement (night/infrared vision)

2 ways for this:

  1. Phosphors convert normally non visible light into visible light, (preferrably infrared. )
  2. Having a wide "catching area" for light like wide telescopes reducing down the image to some eyepiece would ensure that you got the image, with more photons caught.

both assumes people with already outstanding vision are operating these.

Vision replacement (prosthetic eyes)

I have little clue for this one outside that if a surgeon could somehow integrate a fine mosaic of materials with photoelectric properties with the nervous system and have the brain do the heavy lifting of seeing again?

Auto-focus (self-adjusting binoculars)

Pigeons. This is going to be a common answer from me. Training pigeons to only peck when the image is clear for a reward allows for a pigeon to focusing interface that slowly adjusts the focusing lens in a looping fashion and would stop when it is pecked. bino's would be out of the question.

Image analysis (colour recognition)

An array of pigeons. having light be filtered through filters of varying colors and a set of pigeons trained on a reference color could mean that incoming light could be split up by filters (or by prism) and when the pigeon sees their respective color, they peck. The data could be recorded. This assumes that unfocused light passes through. images may mess with pigeons.

Object recognition (facial recognition)

Pigeon pecks button when seeing face.

Object tracking (self-aiming turrets)

BF skinner bomb mechanism. See John's answer regarding this. Most pigeon ideas are based off of this answer.

As for how the pigeon interfaces can directly influence some of these mechanisms, I was thinking that the pigeons (exactly like in bf skinner's bomb) are fitted with electric contacts that energize relays (1830's invention) that trigger DC motors (also 1830's invention) that either operate a punch card machine ( for tabulating data) or directly moves the aforementioned turret


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