DIY "infinity contrast" TV – with 100% recycled parts [video]
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It seems that projector tech (like laser printer tech, and flatbed scanner tech) has been pretty stagnant, the last few years.
Every now and then, I look at the latest projectors, to see if there's any justification for me to replace my old (10 years or so) LED projector, and I have not seen anything that has made me want to.
I need it to be something I can toss into a backpack (along with a bunch of other stuff), and be around 1000 lumens.
Not just lumens, either. The color needs to be good, the resolution needs to be (hopefully) greater than 1080p, and it needs to be usable in a semi-lit room. I don't care about speakers. I use projectors as a speaking aid.
I've been using a tiny InFocus LCD unit that's great, but a little anemic (1080p/750 lumens).
The promise of a laser, is that you can project it against a cinder-block wall, and it will stay in focus, and show great color.
I have heard that laser projectors don’t need to be focused.
Is that true?
There are true laser projectors where the lasers go directly to the projection surface. These are called Laser Beam Scanning projectors, and they don't have to be focused. They work pixel by pixel in scanlines kind of like a CRT, and since the laser doesn't diffuse over short distances, it's never blurry.
Unfortunately, it's a dead technology. I only know of one still in production, and it's 120lm or something.
Does anybody have recommendations for a good projector? I care less about color fidelity, given that this is for work, and more about excellent contrast in a lit room, and resolution.
I'm nearsighted and wear glasses when I watch a play/movie/etc. with faraway detail, but I wear a second, different pair of glasses when working in front of a close screen. They don't make anything sharper, but I have zero eye strain now while working. My optometrist says it's a common thing in your 40's to start to need that.
Have you seen those samsung qdoleds? In a normally lit room they look more washed out than a VA panel, yet somehow still having an "inf" contrast...
On the other hand, there's very little light spill from DLP--- and what little there is, is attenuated by a really big factor by the LCD.
I'd guess the limiting factor is light scattered elsewhere in the room and by the front surface of the display.
Contrast is important, but alone it is useless. You could have a display with only two levels: black and white, and if the black is perfectly black, then it's infinite contrast (any level of white, no matter how dim, is infinitely brighter than total black), but 1-bit color would be useless in reality for home theater.
To make infinite contrast useful, it's necessary to have HDR as well to take advantage of having very dark and very bright areas both able to be represented with detail. Plus having sufficiently bright maximum brightness so that the brightest highlights can really shine.
SDR benefits incredibly as well. HDR is another elevation.
Getting stuck with LCD contrast for years was a travesty to image quality across the board.
What he is making here is a dual panel display. There are actually some LCD monitors that use this concept of 2 separate panel layers each providing their normal contrast resulting in a multiplicative effect.
For the video posted here, the DLP is probably at best 1000:1 and the cheap old LCD is also maybe about 1000:1, so you get about 1 million:1 which is a lot, but not technically infinite like self-emissive display that can turn off the pixels completely for sections of the picture like OLED and microLED.
I would say the weak point of DLP is the screen material needing to be light-friendly, but that's on a sliding scale with the emissive display, not a hard line difference. Both of them preserve black levels when turning on, unlike traditional LCD, but also it isn't true black for either of them.
For example the Epson 5050UB or LS12000 do about 5000:1 native contrast. Most DLPs around the same price level are in the 1000:1 to at most 2000:1 contrast level.
A DLP is nothing like an emissive display. The entire area of a projected image with any projector is always lit up by the light source. Any projector, including DLP is like a TV with a single backlight and no local array dimming.
Here are some simple photos of DLP projectors and here you will clearly see that the black parts, like the black bars above and below the cinemascope image, or even the spill over past the edges of the panel are not black at all.
https://i.redd.it/ak3lwsumvccc1.jpeg
https://preview.redd.it/eyc62402amnd1.jpg?width=4000&format=...
In that second photo, the odd shape of the black projected area is due to the user using keystone, so the image is not being displayed on that part of the imaging panel and it's just left black, but you can see then what the black level really is for projected "black" pixels.
How is there so much light going the wrong way from a mirror?
If DLP has worst contrast than LCD, then why would this project be even remotely successful? Wouldn't the LCD layer in the stock LCD TV would have already been more effectively blocking the light from the stock backlight?
So yes, if the internal light engine of the DLP truly reflected all light away, then, if it outputs zero photons for full-screen black, you could say the projector outputs zero photons.
However, the DLP is not 100% effective; the interesting images will have a mix of bright and dark areas, and the lens and software image processing will raise the black levels above zero.
Source: I worked at BrightSide Technologies before and after the acquisition by Dolby Laboratories and learned about DLP lens limitations from the engineer working on DLP+LCD based HDR displays.
But with enough lamp power...
Larry Ellison used to have a TV projector sized for a movie theater but aimed at a home sized screen, so he could watch movies and enjoy a view of the outside world at the same time. Of course, now anybody can go to Costco and buy a TV that bright.
Unfortunately they don't really exist commercially anymore. I hope the technology develops and they come back... in a way, they are to constant light source projectors what OLED is to LCD. They seem like the obvious evolution.
Don't know anything about the tech -- just thought it was an interesting idea.
Done in at least one early military large screen display system, using six CRTs (RGB x2) aimed at the screen. If one failed, the brightness dropped on the others but you still had an image.
The USAF put a huge amount of effort into early large-screen displays.[1] Not very successfully.
The most successful projection display before LCDs was the Eidophor. (1949-2000)[2] Big, expensive, complicated, high-maintenance, but reliable. Worked by distorting an oil film in vacuum with an electron beam. Biggest buyer was NASA's mission control center. In its final 1990s form, it was bright enough to be used in stadiums.[3]
[1] https://en.wikipedia.org/wiki/Iconorama
https://www.avsforum.com/threads/double-stacking-two-epson-l...
It's one of the ones that's been at the top of my list, but my lack of engineering/tinkering experience has made me a bit apprehensive. Is it result really worth the effort?
1. a TV or monitor diffuser
2. a sheet of LEDs
3. a power supply capable of driving those LEDs. Typically a 12V supply is sufficient (I don't recall if he goes into power supply sizing).
If you're comfortable with learning some things (soldering in this case), you'll be able to pull this off pretty easily.
They never commercialized but they sold their patents to Dolby who turned it in to “Dolby Vision”.
That raises a lot of other questions: He obviously feeds two different videos to the displays. How is this done? Does it add latency, does it work with, let's say, Netflix DRM? Are the two videos even in sync or is the obs post processed feed always N frames behind (think of the transition between barely lit and bright scenes)?