LCDs etc. for optical filtering masks, polarizer, projection, etc. VIS-UV - Page 1
Forum section: electronics / projects

author: evb149
author_rank: Regular Contributor
timestamp: June 04, 2022, 01:37:56 pm
content: I am interested in the uses of LCDs or other kinds of displaytechnologies (LCOS, DMD, ...) for general electro-optical uses besidesjust the usual backlight + TFR LCD = look at the screen image purposes.e.g. projection or filtering of an incident beam of light as inLCD projectors or as in UV ink / mask printing / curing or 3D printers using LCDs as exposure masks for photo exposure, etc.Also perhaps as variable polarization devices or so on.I am wondering about suggestions for sourcing particular devices at low cost for curiosity / experimental purposes and ask because of course though there are lots of surplus / cheap LCDTFT etc. displays out there, these will be variously assembled, laminated, glued, integrated with FPCs, backlights, polarizers, RGB filters, etc. so many will not necessarily be easily adapted for other experiments since they're not documented or constructed to facilitate that.Also I know there's a wide variety of types of display, TN, STN, transflective, IPS, etc. etc. so I'mcurious about finding a variety of such modules with different characteristics.Artistic and technical photo-exposure patterning of photo-sensitive inks, epoxies, masks, etc. by near/mid UV is interesting and useful even for a small scale / moderately low resolution case sothat's one thing that would be interesting to find solutions for.Obviously if I wanted a large volume or special purpose made industrial devices I'd go to the panel manufacturers or industrial / scientific suppliers but I'm more wondering what's interesting and available from the likes of digikey, aliexpress, ebay, surplus, whatever just for low cost and a variety of possible devices without high MOQs / costs etc.Ideas / experiences using these sorts of devices as optical or custom electro-optical components?Seems like I've heard of people even disassembling cell phone / desktop monitor LCDs for suchexperiments though I don't know the particulars of how effective / difficult that is with the tech that is out there presently (adhesives, zebra strips, FPCs, etc that don't tolerate disassembly etc).So I suppose on that front any "tear down" articles / videos could be interesting if they've actually been able to make them work as isolated devices after doing so.

author: dmendesf
author_rank: Frequent Contributor
timestamp: June 04, 2022, 02:04:20 pm
content: There are lots of HD+ and 4k monochrome LCDs being sold at Aliexpress as replacements / upgrades for resin printers. What I don't get is: shouldn't they have 3x more resolution as each subpixel is now counted as a pixel? Maybe they are driven together for some reason (squareness?) But I would like to know a definitive answer.

author: TheMG
author_rank: Frequent Contributor
timestamp: June 04, 2022, 02:23:26 pm
content: Because they are, in fact, true monochrome LCD displays. There are no color sub-pixels.My guess is these were probably originally intended for LCD projector applications. LCD projectors for the most part don't use color LCDs, they use 3 monochrome LCDs (one each for red green and blue).

author: evb149
author_rank: Regular Contributor
timestamp: June 04, 2022, 04:45:11 pm
content: Thanks for the mention. I knew that existed as sort of an off-label niche not really intended by the LCD OEM application category but, as you suggest, the "application" seems to have grown popular enough that there really is a considerable availability of products for that.Last I looked into it it was truly accidental for the most part if any of the LCD panels even workedoptically at near UV and that said nothing of the possible degradation of the LCD itself by thewavelength and luminance. But I guess they must be at least OK enough to be casually usefulfor a while.I'm seeing MIPI DSI driven screens in the 5-8 inch range commonly, and some / all being monochrome I guess though I still don't quite know why LCDs that large wouldn't be more oftenRGBW / whatever since I thought those would be too large for common projector use.And I'm seeing about 900:1 contrast advertised with some probably low optical angle tolerance.So is that technology about the sweet spot for best optical capability for what's cheap / available?I'm not quite sure about other variants, IPS, transflective, etc. wrt. achievable contrast or betterangle tolerance, clarity, etc.Quote from: dmendesf on June 04, 2022, 02:04:20 pm

author: dmendesf
author_rank: Frequent Contributor
timestamp: June 04, 2022, 07:20:52 pm
content: Quote from: TheMG on June 04, 2022, 02:23:26 pmThanks for the explanation. I thought they could be true monochrome but wasn't sure of it because couldn't imagine a mass application to source them from. You nailed it.

author: jeremy
author_rank: Super Contributor
timestamp: June 04, 2022, 10:15:11 pm
content: You might find this video interesting:https://youtu.be/RudStbSApdE

author: RJSV
author_rank: Super Contributor
timestamp: June 04, 2022, 10:36:28 pm
content: I don't have a direct answer, however I would suggest a bit of searching, on Stanford Univ. people doing similar research / published papers.One fellow was doing complete Foriea Analysis (can't spell that, sorry), on each pixel position, in several planes or layers, each doing the 'multiply and sum' as a step. The through-put was incredible!I'll try and find that for you.

author: jeremy
author_rank: Super Contributor
timestamp: June 05, 2022, 12:57:38 am
content: Quote from: RJHayward on June 04, 2022, 10:36:28 pm“Fourier” is probably what you are looking for. Also, this might be the paper you remember:https://www.nature.com/articles/s41377-021-00623-5A company who is commercialising the technology:https://optalysys.com/about

author: Someone
author_rank: Super Contributor
timestamp: June 05, 2022, 01:38:29 am
content: Quote from: evb149 on June 04, 2022, 01:37:56 pmDMD/DLP is unique with its broadband operation and extreme/binary contrast ratio (no linear operation). If you're feeling adventurous you can always try to decap the package and add your own window. There are cheap eval boards for some of the smaller devices or hunt around for larger a second hand set. The DLP core even if you buy the full price eval kit brand new is going to be cheap compared to the other optomechanics and lenses/mirrors needed to setup anything substantial, its quickly a money pit.

author: RJSV
author_rank: Super Contributor
timestamp: June 05, 2022, 04:27:46 am
content: Looks like others have seen the Optical FOURIER processor.At Stanford University, a researcher has used an array of 100 by 109 pixels, if I'm recalling correctly. There are some 5 or 6 'layers' of this LCD built using individual LCD modules, stacked in alignment.I believe it was described as assigning each 'plane', or layer, with a discreet, single math operation. One LCD plane for multiply, followed by a summing layer.Each pixel position was computed separately, but, as described, effectively done optically via the light rays themselves, and each pixel position maintained, going 'downstream' through the stack of LCD plates.Very cool, simple to understand, and, with some THROUGHPUT processing equivalent of a huge value, like 45 Tbyte per sec. I don't remember actual throughput quoted, by that Stanford researcher. Browsing by way of smartphone, I'm not sure what history trail is saved, during sessions starting with Google.Oh, and PLUS, the STANFORD Univ. Research guy mentions, that the available CMOS fabrication of IC chip Dies contributed a direct savings, by providing established methods, for (relatively) easy utilized and understood process, in semiconductor maker's in-house fab. machines and clean rooms.I think, the 100 by 100 pixel array provides a x10,000 boost, to effective through-put.Finding and sharing such gems, like this, is a hit and miss process, compared to full laptop (having all history files, etc.)