A TV With Contrast You Haven’t Seen For Years

March 5, 2025 by Jenny List 42 Comments

It’s something of a surprise, should you own a CRT TV to go with your retrocomputers, when you use it to view a film or a TV show. The resolution may be old-fashioned, but the colors jump out at you, in a way you’d forgotten CRTs could do. You’re seeing black levels that LCD screens can’t match, and which you’ll only find comparable on a modern OLED TVs. Can an LCD screen achieve decent black levels? [DIY Perks] is here with a modified screen that does just that.

LCD screens work by placing a set of electronic polarizing filters in front of a bright light. Bright pixels let through the light, while black pixels, well, they do their best, but a bit of light gets through. As a result, they have washed-out blacks, and their images aren’t as crisp and high contrast as they should be. More modern LCDs use an array of LEDs as the backlight which they illuminate as a low resolution version of the image, an approach which improves matters but leaves a “halo” round bright spots.

The TV in the video below the break is an older LCD set, from which he removes the backlight and places the electronics in a stand. He can show an image on it by placing a lamp behind it, but he does something much cleverer. An old DLP projector with its color wheel removed projects a high-res luminance map onto the back of the screen, resulting in the coveted high contrast image. The final result uses a somewhat unwieldy mirror arrangement to shorten the distance for the projector, but we love this hack. It’s not the first backlight hack we’ve seen, but perhaps it give the best result.

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Giant Demonstrator Explains How DLP Projectors Work

December 22, 2023 by Lewin Day 5 Comments

Texas Instruments developed digital mirror devices, and the subsequent digital light processing (DLP) projector, starting in the late 1980s. The technology is a wondrous and fanciful application of micro-scale electronics and optics. Most of us that have tangled with these devices have had to learn their mode of operation from diagrams and our own imagination. But what if you just built one at a large enough scale that you could see how it worked? Well, [jbumstead] did just that!

A real Digital Micromirror Device (DMD) consists of hundreds of thousands of mirrors, which would be impractical to recreate. This build settles for a simpler 5×5 array made using half-inch square mirrors. It uses solenoids to move each individual mirror between a flat and angled position to create the display. The solenoids are all under the command of an Arduino Mega which controls the overall state of the display and shows various patterns.

It’s not perfect, with the mirrors not quite matching in angles at all times, but it demonstrates the concept perfectly well. When you see it in action with light bouncing off it, you can easily understand how this could be used to make a display of many thousands of pixels in a projector arrangement. We’ve featured some other DLP hacks before, too, so dive in if you’re interested.

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Hackaday Links: July 9, 2023

July 9, 2023 by Dan Maloney 8 Comments

Good news this week from Mars, where Ingenuity finally managed to check in with its controllers after a long silence. The plucky helicopter went silent just after nailing the landing on its 52nd flight back on April 26, and hasn’t been heard from since. Mission planners speculated that Ingenuity, which needs to link to the Perseverance rover to transmit its data, landed in a place where terrain features were blocking line-of-sight between the two. So they weren’t overly concerned about the blackout, but still, one likes to keep in touch with such an irreplaceable asset. The silence was broken last week when Perseverance finally made it to higher ground, allowing the helicopter to link up and dump the data from the last flight. The goal going forward is to keep Ingenuity moving ahead of the rover, acting as a scout for interesting places to explore, which makes it possible that we’ll see more comms blackouts. Ingenuity may be more than ten-fold over the number of flights that were planned, but that doesn’t mean it’s ready for retirement quite yet.

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A Volumetric Display With A Star Wars Look And Feel

June 20, 2023 by Dan Maloney 18 Comments

It may not exactly be what [Princess Leia] used to beg [Obi-Wan] for help, but this Star Wars-inspired volumetric display is still a pretty cool hack, and with plenty of extra points for style.

In some ways, [Maker Mac]’s design is a bit like a 3D printer for images, in that it displays slices of a solid model onto closely spaced planar surfaces. Sounds simple enough, but there are a lot of clever details in this build. The main component is a lightly modified LCD projector, a DLP-based machine with an RGB color wheel. By removing the color wheel from the projector’s optical path and hooking its sync sensor up to the control electronics, [Mac] is able to increase the framerate of the display, at the cost of color, of course. Other optical elements include a mirror to direct the projected images upwards, and a shutter harvested from an old pair of 3D TV glasses. Continue reading “A Volumetric Display With A Star Wars Look And Feel” →

Holograms: The Future Of Speedy Nanoscale 3D Printing?

April 9, 2023 by Dave Rowntree 7 Comments

3D printing by painting with light beams on a vat of liquid plastic was once the stuff of science fiction, but now is very much science-fact. More than that, it’s consumer-level technology that we’re almost at the point of being blasé about. Scientists and engineers the world over have been quietly beavering away in their labs on the new hotness, nanoscale 3D printing with varying success. Recently IEESpectrum reports some promising work using holographic imaging to generate nanoscale structures at record speed.

Current stereolithography printers make use of UV laser scanned over the bottom of a vat of UV-sensitive liquid photopolymer resin, which is chemically tweaked to make it sensitive to the UV frequency photons. This is all fine, but as we know, this method is slow and can be of limited resolution, and has been largely superseded by LCD technology. Recent research has focussed on two-photon lithography, which uses a resin that is largely transparent to the wavelength of light concerned, but critically, can be polymerized with enough energy density (i.e. the method requires multiple photons to be simultaneously absorbed.) This is achieved by using pulsed-mode lasers to focus to a very tight point, giving the required huge energy density. This tight focus, plus the ability to pass the beam through the vat of liquid allows much tighter image resolution. But it is slow, painfully slow.

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Wiggling Screen And DLP Power This Volumetric POV Display

July 1, 2021 by Dan Maloney 25 Comments

It seems like the world is ready for a true 3D display. We’ve seen them in sci-fi for decades now, with the ability to view a scene from any angle and inspect it up close. They’ve remained elusive, but that might just be changing thanks to this open-source persistence-of-vision volumetric display.

If the VVD, as it has been named by its creator [Madaeon], looks somewhat familiar, perhaps it’s because editor-in-chief [Mike Szczys] ran into it back in 2019 at Maker Faire Rome. It looks like it has progressed quite a bit since then, but the basic idea is still the same. A thin, flexible membrane, which is stretched across a frame, is attached to articulated arms. The membrane can move up and down rapidly, fast enough that a 1,000-fps high-speed camera is needed to see it move. That allows you to see the magic in action; a digital light processor (DLP) module projects slices of a 3D image onto the sheet, sending the correct image out for each vertical position of the membrane. Carefully coordinating the images creates the POV illusion of a solid image floating in space, which can be observed from any angle, requires no special glasses, and can even be viewed by groups.

With displays like this, we’re used to issuing the caveat that “it no doubt looks better in person”, but we have to say in the GIFs and videos included the VVD looks pretty darn good. We think this is a natural for inclusion in the 2021 Hackaday Prize, and we’re pleased to see that it made it to the semi-finals of the “Rethink Displays” round.

Be Anyone Or Anything With Facial Projection Mask

October 31, 2019 by Dan Maloney 18 Comments

In the market for a low-poly change to your look? Hate the idea of showing up for a costume party only to find out someone is wearing the same mask as you? Then this face changing front-projection mask may be just the thing for you.

To be honest, we’re not sure just how much [Sean Hodgins]’ latest project has to do with cosplay. He seems to be making a subtle commentary about dealing with life in the surveillance state, even though this is probably not a strategy for thwarting facial-recognition cameras. [Ed Note: Or maybe it’s just Halloween?]

The build consists of a Raspberry Pi and a pico projector of the kind we’ve seen before. These are mated together via a custom PCB and live inside a small enclosure that’s attached to the end of a longish boom. The boom attaches to the chin of 3D-printed mask, which in turn is connected to the suspension system of a welding helmet. Powered by a battery pack and controlled by a smartphone app, the projector throws whatever you want onto the mask – videos, effects, even images of other people. Even with some Photoshop tweaks to account for keystone distortion from the low angle of projection, there’s enough distortion that the effect is more artistic than masquerade. But honestly, having your face suddenly burst into flames is pretty cool. We just wonder what visibility is like for the wearer with a bright LED blasting into your eyes.

As a bonus, [Sean] has worked this build into a virtual treasure hunt. Check out 13thkey.com and see what you can make from the minimal clues there.

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