DIY 2880x1800 projector | Hacker News Reader

DIY 2880x1800 projector

forum.allinbox.com

Make sure you check page #2 too [1]. More build pics, bulb encasing design, cooling, and thermal images. These guys are pretty good marketers. I want to attempt this, and I am not even in the market for a projector, I mean you cannot get better than this for a DIY project [2, 3].

[1] http://forum.allinbox.com/aspectgeek/Projetsencours/18/photo...

[2] http://i.imgur.com/PoIY7aR.jpg

[3] http://i.imgur.com/SNvdzcr.jpg

LED off-road auto headlamps, brighter than on-road, are good enough and cheap enough now that those are an illumination option. You can get a few thousand lumens now for a hundred dollars or so. Halogens are a pain; they have a short life, cooling problems, and generate IR which turns into heat at the LCD panel, so you need fan airflow across the panel. This guy has been struggling with halogen cooling and power problems. Halogens are on the way out. Even stage lighting is going LED.

Projectors are getting better, cheaper, and brighter with LED lamps behind them. Here's a 1000-lumen 1080p projector: "http://www.lg.com/us/projectors/lg-PF85U-portable-led-projec.... It's still around $1200, but give it six months.

leds dont really produce nice white, its mostly blue led + yellow phosphor producing bumpy spectrum

As you point out, the color rendering index of the LED is a function of the phosphors. There are now a number of 'white' LEDs which have better CRI than projector bulbs. It really is only a matter of time before projector bulbs are gone.

Good news, thanks. Can you point towards any types or brands of high-CRI LED's? Thank you!

Research or products? I've got one of the CREE [1] LEDs and its pretty good. (my application is building a light tent for macro photography vs a projector though) Philips has some high CRI lights as well which are a bit earlier than the CREE one. Most of the research these days seems focused on more lumens per watt, once the CRI got above 90 most people moved on to the efficiency question.

[1] http://www.cree.com/News-and-Events/Cree-News/Press-Releases...

Thanks!! The idea was to ask about products but links to research would equally well appreciated. Didn't even think to hope for such of goodness :)

IMO each point of CRI really does count, even in the high 90s. I'm using EIKO Solux halogens that have a CRI of 99 as I recall. Excellent light quality, colors are so much better and everything just feels so much more right.

Personally I think CRI is a quite flawed metric, since an incandescent bulb is judged to be 'perfect' and everything else is essentially judged on how close it can get to that, based on a somewhat arbitrary set of measurements.

But I’ll agree with you that LEDs (and especially CFLs) have terrible color rendering, and make pretty unpleasant room lighting.

ChuckMcM: a light source for taking photos is a very different kind of application than room lighting (for which I really dislike all of the LEDs and CFLs I’ve tried, even expensive fancy ones) and also a very different application from projector backlights: projector backlighting is an application where what matters is the interaction between the source spectrum and the transmission spectra of the RGB color filters; the CRI is an almost totally irrelevant metric for projector backlights IMO, except insofar as an LCD was designed to be used with an incandescent backlight (which I doubt a laptop display panel would be); regardless of backlight source, it should be possible with the right equipment (spectrophotometer) to measure the colors projected on the wall and properly characterize the system, and then generate an ICC profile and get pretty accurate color out.

Actually it seems that all laptops now use white LED backlights in their "intended" configuration. That suggests to me that if the phosphors on your projection light source LEDs were equivalent to the ones on the backlight LEDs you would get the same colors coming of the screen as you would from it on a laptop. At that point it becomes a question of the reflection surface as to how well it reflects the spectra you throw at it.

And I agree with you that taking pictures is a different application than room lighting, but there is significant overlap. Essentially I'd like to have a "perfect" broad spectrum lamp for my pictures, and I'm happy to bias the spectrum one way or the other for room lighting. That said, the combination of a broad spectrum room light and a digital photo processing stream lets me get back to the 'original' colors. That was not always true with LEDs but with the high CRI ones it works well for me.

I just replaced all the bulbs in my house with CREE led from the 40 and 60 high CRI line and the 100w regular line, as well as some br30 and mr16s.

In California, at Home Depot, the high CRI products are subsidized by the utilities and thus quite affordable.

Hmmm, I did write "better" and after looking at my CREE bulb specs I realize that 93 is not '99' :-) so they are still a bit worse. In my opinion they are good enough to be equivalent but concede the point that spec wise they are inferior.

On a vaguely related note, any recommendations for white-light (not yellowish-light) LED bulbs for home use that compare favorably with a Reveal incandescent bulb?

In spite of their marketing name they are just bluer lights (2850K versus 2700K for 'warm' and 3000K for 'warm white' so midway between those)

GE has some equivalent LED bulbs that they market under the 'Reveal' moniker to indicate they have a 2850K color temperature. A quick search suggests that Home Depot sells them in the US.

Wow that site still exists! :) I did one when I was 17 (I'm 28 now), I first modelised everything in 1) an optics simulator 2) Solidworks, and then assembled it with a wooden case: http://forum.allinbox.com/aspectgeek/Projetsencours/9/projec...

http://www.google.com/cse?cx=partner-pub-5733989050076975%3A...

This looks spectacular!

I didn't quite get how it works. Is it essentially an LCD panel with an extreme backlight, and a lens to correctly display the picture?

Yes. Much like many consumer projectors.

Most of them are actually DLP these days, with LCD-based ones occupying the majority of the ultra-low-end (XGA and below).

Even the ultra-low end are frequently DLP these days, just replacing the powerful bulb with an under powered LED.

> replacing the powerful bulb with an under powered LED.

I've also seen that Sony and Epson are selling laser illuminated projectors as opposed to the more common LED/halogen/etc illuminated projectors. Apparently for high luminosity, laser becomes more efficient and less prone to damage than both LED, halogen, incandescent, argon/xenon etc.

But it disappoints me that these projectors just use the laser for illumination. I'm waiting for when we have laser-on-DLP without filters type projectors.

This is true. But it was only a decade ago that most projectors were just LCDs with a ridiculously inefficient lamp.

Make sure to add some fans, the LCD/TFT panel doesn't like the heat of a high-power halogen/xenon lamp! OP uses several fans too, to cool down the air around the xenon lamp: http://forum.allinbox.com/aspectgeek/Projetsencours/18/photo...

A friend converted an overhead projector (and a 1080p LCD panel) into a DIY projector, some years ago. His panel turned brown and broke because of too high air temperature.

As even the OP has cooling issues - lesson learned: Better use LED with 1000+ Lumen instead of a halogen/xenon lamp.

It seems OP uses the arc lamp for its almost-point-source qualities. Halfway down the first page he simulates a led source, it will create a less sharp focal point.

This things are what makes me come and check Hacker News

Thanks for sharing

If you like these kind of posts, you should definitely visit the Hack-A-Day blog every now and then :)

Add Instructables.com to that.

In fact, I'd respectfully suggest that HN is not even slightly the best place for this sort of thing.

This brings up some good (and bad) memories from past hobbies. Back in the day when 1080p was the new rage, I remember getting immersed in one of these DIY projector projects. For anyone looking into it - this was the site to get parts from:

http://diyprojectorkits.com/store/

They built a box 100 times better than I would hoped to have. Plus, I believe I got my lenses from there as well.

The videophile in me really wanted to see some test patterns. It's relatively easy to get some nice, artificially colorful CG shots to look good in screenshots, but comparatively hard to get uniform focus and illumination with color fidelity that will make human faces look natural. Using such a large LCD panel might make focus easier (and the cabinetry bigger), but I bet getting the illumination anywhere close to uniform is a real PITA!

The LCD he got for $200, is that actually the same as what's in the MacBook? That's not really clear from the first paragraph..

Yup.

http://www.ebay.com/itm/New-15-LCD-Screen-Display-For-Macboo...

yes, but its not optimal, you can get LP129QE1-SPA1 for third of the price

The point is what will drive it? There's a driving board for the 15" Mac retina display.

both screens use eDP, you can drive them with ordinary DisplayPort, all of those those "driving boards" started with Polish Warsaw Hackerspace dude (Emeryth) publishing his findings concerning ipad screen

http://emerythacks.blogspot.com/2013/04/connecting-ipad-reti...

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