Yes, we are starting something new called Hologram Hump Day – Ask a Hologram Expert! You ask hologram questions, and we provide answers from an MIT-trained holography expert. From questions about our self-developing hologram film, to techniques and tips for making holograms. Happy Wednesday!
To the Hologram Questions!
Q: Can this film be used to make holographic transmissive optical elements? Will such a made hologram bleach with exposure to blue laser light? What is the diffraction efficiency? How is everything held stable enough for 4 minute exposure despite crude setup?
A: Our self-developing hologram film can make both transmission and reflection holograms. The film is sensitive to most visible light, so can make red, green, blue, or full-color holograms. Once the film is fully exposed (essentially saturated), it is no longer sensitive to further exposure, and can be viewed and illuminated with a light (or blue laser) without further affecting the recorded hologram. I like to tell people that it is like the film has a certain amount of “active components” (which is why it is shipped and stored in a light tight box, and is light sensitive before exposure), and then the active components get used up (saturated) during the hologram exposure. After that, it is essentially an inert plastic, that no longer reacts to further exposure. You can use a UV post-cure after the hologram exposure, which will sometimes help further bleach (or clear) any remaining dye and “lock in” the hologram exposure, but honestly we don’t often need this for most recreational holograms. And yes, holograms are sensitive to vibration and motion, but our kits use some ingenious (and simple) methods that allow the setup to be quite robust. We’ve actually made holograms at a local Starbucks on one of their coffee table in the middle of the store. Maybe someone will ask more questions in the future about how we do this, and the secrets to stability in our kits (hint, hint!).
Q: My father and I have been wondering for a few years if there was any way we could restock basic materials without shipping them halfway around the world. I can’t be the only Englishman interested in amateur holography.
A: We do not currently have any distributors and you would need to order directly from us. With that said, let me know if you have suggestions for distributors in your area (who would you want to see selling these near you? Science store, other online group with similar interests and products? Etc.). They would probably need to be able to handle a certain quantity per month, allowing to ship in bulk, and then getting a better overall price per unit.
Q: It today really the International Day of the Hologram (June 5)?
A: That’s what we heard too! Visit the International Day of the Hologram on Facebook, https://www.facebook.com/funhologram and at http://frederick2.com/international-day-of-the-hologram/.
Q: Is there a threshold level at which the hologram film starts being exposed? That is, a minimum combined (object reference) power level below which the film will not expose no matter how long the exposure lasts. (Is that power level known for the three colors of the color hologram kit?)
A: Our hologram film is a photopolymer, so it does have a “threshold” level, where the laser exposure could be so low that it does not “kick off” the reaction. This is different from older chemically developed silver-halide films, where you could drop the exposure intensity (mW) down to almost any level as long as the exposure time (seconds) was increased proportionally, creating the same exposure energy (mJ). Photopolymer, on the other hand, often has a lower “threshold” intensity, where the process cannot start, no matter how long the exposure time. With that said, we have had significantly lower “threshold” levels over the last 8-10 years, where it is almost not a factor (would need to be a very, very, very low intensity exposure). Before that, we had a “threshold” level of about 20 microWatts. But again, it is now much lower, and would not be noticed by most hologram-makers.
Q: Is there a known power ratio relating the colors of the color hologram kit that yields the best color balance?
A: Our hologram film is sensitive to most laser wavelengths (colors) across the visible spectrum, allowing for red, green, blue, or even full-color hologram exposures. With that said, the sensitivity is different for the different colors. You can take a look at our Hologram Film Spec Sheet here (about 1/3 down page). The color sensitivity is roughly as follows: R – 20mJ/cm2, G – 30mJ/cm2, and B – 80mJ/cm2. So a 2:3:8 ratio for R:G:B.
Q: How do you make the projected patterns things (shine laser in, get a mouse or a squirrel or other image on a flat surface that you project on)? Can you animate it based on the angle of the input laser? Eg, if I wanted to project a “He-Man” image when I project it on my house wall… can I have him draw his sword if pan the laser across the film? Vector graphics are fine; ideally I’d like to be able to specify the divergence (size at a distance)… Is this a computer-generated hologram? Where would I look to get started?
A: Take a look at the YouTube video we have posted here: Introduction to Holography. It’s from 1972, and originally created by Encyclopedia Britannica with TJ Jeoung and Lake Forrest College. You’ll see a section that shows almost any hologram can be illuminated with the point from a collimated laser and will “project” a 2D image of the 3D scene based on that location on the hologram and the angle of illumination (they did a cool effect where they used a hole punch to take a tiny piece of the hologram and illuminate it with a laser to show it still contains a “projected” image of the whole scene). Essentially, this is a diffracted image that creates a 2D projected image based on the hologram. We’ve looked at doing an Upgrade Kit that would walk through the process of creating something like this, and if there is further interest, we might look at that more. It could be CG created holograms with something like our 3D Hologram Printer, but there are also analog techniques that could accomplish this as well. (Concerned about your interest in projecting squirrels, though! Very redeeming that you came back with He-Man, so nice work!)
That’s it for today’s Hologram Hump Day – Ask a Hologram Expert! If you liked this, or have more questions for next week, leave a comment below or email us at LitiHolo.
Thanks for being part of the Hologram Community, and making this possible!
– LitiHolo
If I was to make a hologram of another already made hologram would I see it move in the hologram I’m making?
Daniel,
Making copies of holograms is fairly straightforward, especially if the master hologram is one that you made yourself. The resulting copy should have all the properties of the master if you have taken care to use the same recording geometry and wavelength. I’ve done this with many reflection holograms.
Another popular thing to do with reflection holograms is to flip the master over so that the image appears above it, then place the copy plate on top of the master, maybe with some spacing. Then when you view the copy hologram you flip it over and the image will appear in front of the film plane, so that you can stick your finger in it! This is of course great fun. It’s best done if you can make a collimated recording beam so that the playback geometry on the master hologram is identical to the recording geometry. Otherwise you end up with angular detuning and resulting dark zones in the copy. There’s plenty of literature out there on copying holograms, but don’t get bogged it down in the reading, just give it a try!
Hi , sorry for my poor english i’m french.
I see that the supports are thick and visibly made of glass. Is it possible to have flexible and adhesive polymer support plates for example like on certain toys from the 80s/90s?
What are the challenges to overcome to create a color holoprinter, or give the one that exists the ability to do color?… Besides flooding that is.
Definitely interested in how you achieve adequate stability with the simple setup of the kit! Do tell.
I remember hearing about holography of a telescope and somehow the “telescope lens” worked? I’m curious if this was a particularly elaborate holographic image, if it worked because it captured the light coming through the lens, or if somehow a holograph of an optical lens actually can alter light passing through it?