Turning 3D Shutter Glasses Into Automatic Sunglasses

[Dino’s] hack this week seeks to create sunglasses that dim based on the intensity of ambient light. The thought is that this should give you the best light level even with changing brightness like when the sun goes behind a cloud or walking from inside to outside. He started with a pair of 3D shutter glasses. These have lenses that are each a liquid crystal pane. The glasses monitor an IR signal coming from a 3D TV, then alternately black out the lenses so that each eye is seeing a different frame of video to create the stereoscopic effect. In the video after the break he tears down the hardware and builds it back up with his own ambient light sensor circuit.

It only takes 6V to immediately darken one of the LCD panes. The interesting thing is that it takes a few seconds for them to become clear again. It turns out you need to bleed off the voltage in the pane using a resistor in order to have a fast response in both directions. Above you can see the light dependent resistor in the bridge of the frame that is used to trigger the panes. [Dino] shows at the end of his video that they work. But the main protective feature of sunglasses is that they filter out UV rays and he’s not sure if these have any ability to do that or not.

62 thoughts on “Turning 3D Shutter Glasses Into Automatic Sunglasses

  1. Weren’t there some sunglasses in the Hitchhiker’s Guide series that blacked out the wearer’s vision when they sensed danger? It would be fantastic if somebody made a pair of these that blacked out whenever they heard loud noises.

    1. I thought the same. That LCDs have to be ac driven.

      In this project, the lcd is only driven on or off, i think. There are no different dim levels. For better performance, a pwm controlled brightness of the lcd would be useful.

  2. So basically he made a pair of those transitions glasses.

    I had a simmilar idea using the LCD’s from those blinking solar keychains, never made a nice version though since I could only find small ones.

    1. Transitions lenses use a UV sensitive coating. They work poorly, if at all, inside a vehicle because the windows filter out too much UV.

      Photogrey and Photobrown are part of the glass so the effect can’t get scratched off and they work using visible light so they work just fine inside a vehicle.

      1. Actually they just came out with transition lens that work in the car now. I just got this new coating on my prescription glasses a month ago.

        Transitions VI Lenses includes the following…
        Drivewear ®
        Windshields in today’s vehicles block most of the UV rays that cause Transitions Lenses to activate, or darken. As a result, when worn inside a car where less UV light is present, the ability of the lenses to transition to dark is reduced. A new category of lenses, called DriveWear , offers a unique and high-tech solution for driving. Using the technology of Transitions Lenses, DriveWear combines the glare protection of polarized prescription sunglasses and photochromics which respond to both visible and UV light. The result is a lens that can react to light both outside and behind the windshield of the car, and transition to dark accordingly. Drivewear lenses provide the ideal visual solution in today’s world where the automobile is an important part of many peoples’ daily lives.

    2. The most disappointing thing about RealD 3D and other 3D movie glasses that work with circularly polarized light is they have no visible effect on a laser beam. :(

      A linear polarized filter produces a diffraction pattern. Use two filters and change the relative rotation then shine a laser through for different effects.

      What I haven’t tried is overlapping the left and right filters from two pairs of circular polarized glasses to test if a laser that passes through one gets polarized and blocked by the opposite rotation filter.

  3. I suspect the LCD is unlikely to reduce the UV. Perhaps it would be worth applying some of the clear UV filter contact that is used to tint windows.
    The risk is that by reducing the overall visible light to your eyes without reducing UV, you cause the iris to open up thereby increasing the damage to your eyes.
    That being said if the UV is being stopped then perhaps these glasses would be working more like those automatic welding goggles??

      1. Clarification – crown glass (the sort used in eyeglasses) blocks very little UV. Other types of
        glass have other properties, (e.g. automotive windshields are not as clear, and block some UV).

  4. The LCD’s do not block UV. In fact, UV damages them over time. The passive polarized 3D glasses I have gotten at several screenings have all been accompanied by printed warnings not to use them as sunglasses for this reason.

      1. I wouldn’t say nothing in common – they both work based on light selectively passing through the lens assembly based on its polarity. That’s about it though.

        For those that don’t already know: passive 3D glasses like at the cinemas have a different polarising filter on each lens, and two equivalent images projected on the screen in polarised light. Each eye sees only one of the two overlapping projected images.

        Shutter glasses, like the above, have a polarising filter and a liquid crystal panel (like a single pixel from a monitor, or a single segment from a calculator). When a voltage is applied to the LCD, it changes the polarity of light that it allows through. Combined with the filter, this allows you to electronically black out one eye at a time really fast, alternating the picture on the screen so that each eye sees a different picture.

      2. Yeah, I thought about getting bogged down in technical details, but decided to just get my point across. I am taking the position that the polarisation of light in LCD glasses is an implementation detail rather than a property of what they are actually there to do, which is block the view.

    1. So, did you actually notice that I put up an annotation on the video saying NOT to do that? Yeah… I learned something too. :) The backwards cap acted like a resistor, and I then realized, duh, I need a resistor there! I was only using 6 volts and the cap was rated way higher than that. I hope no one looses sleep over this! I know I won’t. :)

    1. I would have needed a 3D TV to generate the 120hz IR pulse, or built something to generate it. The hack was about making them go dark when exposed to bright light. Scoping the circuit would have been cool!

  5. Cool hack!

    Good thing he put that disclaimer at the end concerning what it actually filters.

    PIC running a pwm’d signal would be cool. Probably more efficient and easier on the lcd’s. (I dont think they like dc.)

    Also, why the heck didn’t he scope the original circuit?

  6. It may surprise the safety trolls that I’ve been walking around for years with non-UV filtering corrective lenses (the plastic blocks some), and my eyes are no worse for it. Unless you look directly at the sun, these are at least as safe as not wearing sunglasses at all.

    Logically, if the LCD is damaged by UV exposure, then it probably absorbs at least some. I couldn’t find a clear answer myself, it might depend on the specific LCD chemistry in the glasses, as well as the nature of any plastic coatings.

    A UV-sensitive photodiode,a scope, and science would be enough for a quick test though!

    1. You are forgetting one particular factor:

      The dilation of the pupil. Sunglasses that block some percentage of regular light, yet allow UV will result in your pupil dilating, letting more UV light into the eye.

      Just because you aren’t blind doesn’t mean no damage was done.

      Frankly you should probably just invest the 12 bucks it costs to get a UV coating next time you get a new pair of lens.

    2. Faster way might just be to get a piece of white paper (or something that fluoresces) and a blacklight. Put the glasses between the blacklight and the paper, and see if it casts a “dark” shadow. (might be a good idea to see what proper UV blocking glasses do first, then compare) The caveat here being that this doesn’t check UV-B transmittance.

      Of course, a UV coating of some sort is definitely a good thing – arc eye / snowblindness is not fun.

  7. It would be cook if the LCDs could get the appropriate thin film coating to block UV.
    I’m also curious if the LCDs can be driven with a PWM signal and/or a digital potentiometer to get intermediate levels of darkness (assuming those intermediate shades would be useful).

    1. You can drive them using lower voltage to produce different levels of intensity. I guess LCDs are too slow for PWM. At least as long as you don’t use LPF.

      (Most LCD equiped units have contrast correction which i believe controls voltage fed to LCD)

  8. I have two pair of sunglasses because In different situations I like diffenent levels of shading over my eyes. Would a variable resistor vary the darkness like changing the contrast on my old ti-85?

  9. Would be interesting to see the other side of the original PCB, which mcu is used, how does it work? Is the usb only used for charging? Maybe it is easier to just change the code in the mcu…?

  10. Now, I want to get an Atmel 168 to drive them using PWM with a DC offset so they get their desired AC-like power wave. The 168 can pay attention to a mini solar cell that can actually charge the bats in lieu of daily USB pluggage.

    Also, as a wire-frame prescription glasses wearer, I’d want something I can just clip onto the front of my regular glasses and not look like crap. Could these LCDs be ground around the edges to reshape them without killing their LCD properties?

  11. I want to do an experiment in which i need to have glasses with manually controllable dimming (have different levels of dimming). And i’ve been wondering, was there an attempt to make such a thing out of this experiment or maybe you could give me some ideas about what should i need in order to make glasses, for which i could manually control the level of dimming.

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