Sunday, March 29, 2009

Brief thoughts on glass

i was going to post a brief thought on glass, but in checking back at what i've posted here so far, i realize that it would be out of context. so, here's the low down.

on thursday, we received and tested the glass from showcase shower door company with no luck. it simply doesn't exhibit the same TIR properties as acrylic.

we also went to classic glass with my laptop, the hacked ps3eye, and the ir emisison circuit to test a variety of glass thicknesses, all of which completely and utterly failed at reflecting IR back to the webcam. the eye was unfiltered -- we ordered an 850nm and a 940nm filter on thursday as well.

ultimately, we expect that this will mean we'll have two surfaces. glass for the structural support, and acrylic for the touch sensing. acrylic's succeptibility to scratching remains a problem.

yesterday was the IEEE Region 6 Central Area meeting. i spent friday picking up the micromouse maze from santa clara university with craig. the meeting was an exciting experience, and far less taxing than i had expected. i wound up winning second prize in the student paper competition for a paper on my convolution verilog module from 125.

anyways, for the brief thought that prompted me to pull up the blog posting engine, it occurred to me that perhaps we should investigate whether or not FTIR works for visible light in glass and acrylic, and how many different display angles we can find on LEDs from suppliers.

it wouldn't benefit our final product for masc because the cost and time efficiency of the ribbons from but since we're here doing the research, i feel like we might as well run these tests so we can say with certainty whether or not glass really is as physically unfeasible as we currently think it is.

Projection Surface tests

we received two essential components for testing yesterday: the IR LED ribbon sample kit from, and samples of the Digiline-White and the Digiline-Contrast projection screens from IFOHA in Germany.

matt and i tried a simple projection test, holding the samples up in front of the projector to see which one looked the best. we also used the pvc sample which professor renau obtained. previously, the pvc was our best option for display, and it probably still looks the best, but it's damn horrible at passing infrared from the FTIR through. the videos below show off the FTIR tests through the three media. in the first video we (think we) are using 850nm LEDs, while in the second video we are using 940nm LEDs.

you'll notice that the digiline contrast passes 850nm about as well as the digiline white (the white is just marginally better), but it doesn't pass the 940nm nearly as well. both digiline screens work much much better than the pvc material.

personally, i also thought that the digiline white looked more appropriate than the digiline contrast. it was brighter and looked less glittery.

everyone on the team should view all three before we make a decision, but white seems to make the most sense to me, both for its IR passing properties and its display quality.

the quarter officially begins tomorrow, so now it's time to read up on OpenCV. also, we should receive the IR bandpass filters tomorrow, so the prototype is not too far away from being finished.

until next time,

Thursday, March 26, 2009

the beginning of the beginning of the end

progress is seen on our team blog in the form of FTIR through an unfiltered webcam.

our (and more specifically, my) progress today is as follows:

- built ir emission apparati from provided LEDs and leftover mechatronics parts. to be specific, 270 ohm resistors, a couple of 7805's, some capacitors, and seemingly excessive surface-mount sized solder.

- tested said emission apparati with a sheet of acrylic i've had sitting in IEEE for the past year. i've been meaning to turn it into a stribe enclosure with the laser cutter, but the full sheet is helpful, so my procrastination has actually paid off.


- receive glass "samples" from chris at showcase shower door, santa cruz, ca. these samples are 18"x24" tempered sheets with finished edges.

this essentially prompts us to acquire index-matching epoxy. jas will be working on the prototype's structure in the meantime.

the structure will be a basic trapezoid, with a flat surface when rested on the short parallel side. the angled edge will be at 60º, so that the entire apparatus can rotate and rest on the side with a 60º drafting table style interface. the whole thing will act similar to a podium, so tilting it will not be a huge ordeal. the distance between the glass and the projector will be minimal.

we will also post videos of tests with the variety of 850nm LEDs we currently have in lab: 5mm radial, 3mm radial, and these weird black-housed, lower power variety.

as a side note of clarifiation to the last bunch of LEDs, we tested these strange black-housed LEDs at the end of the day, and 6 of them turn out to be less bright than the 2 5mm LEDs we tried in the video at the beginning of this post. part of me wonders about superpositions and beat frequencies, but i'm pretty sure we'd still be seeing a lot of light even in the presence if these phenomena.

eagerly awaiting tomorrow,

Tuesday, March 24, 2009


got a b in feedback. nothing to worry about.

i didn't get in to mills, so i guess i'm looking for a job.

got an a+ in architecture, though. thinking about tutoring for 112, but want to seriously evaluate my schedule and my workload before making any decisions.

tomorrow we ramp up to scimp full time.

Saturday, March 21, 2009

the calm before the storm

finished finals yesterday. despite my thorough understanding of feedback control systems, i'm now worried that i won't pass the class because of my homework grade. i didn't turn in the last two assignments because i got sick and chose to sleep instead of getting them done. when i looked at my "current grade" at the end of the final, i was at 38.1% (out of a possible 50%), and i know i missed a couple of things on the final. if the grade scale is straight, then i need at least a 70% on the final to have a comfortable c grade. hopefully i didn't screw it up too hard.

this is the calm before the storm. i've spent all day in la, received an award for our ieee student branch, and had a nice little meetup with other monome users in the la area.

in browsing around for parts to order, i've just now realized that my task of webcamera stitching is going to be substantially more difficult than i had previously expected.

not only am i going to have to recompose the image (what i naively perceived to be the extent of the problem), but i'm going to have to devise a method of calibrating the cameras so that the image recomposition doesn't contain any redundancies from overlapping computer vision.

my intuition is telling me that a set of blocks with protruding silicone fiducials is going to be the best approach for calibration...

if there's guaranteed overlap and only 4 webcams, then i think only 5 markers are needed to fully calibrate. if i'm wrong, then up to 9 markers might be needed for 4 cameras. for 6 webcams, up to 12 may be needed.

at the end of the day, the projectors can display an image instructing the person performing the calibration where to place these markers, but that's assuming that the projectors are independently calibrated..

i'll close this with a few of my curiosities:
- will the table be rigid enough so that the cameras can be calibrated once and left in place?
- does it make more sense to figure out a calibration method before installing the IR bandpass filters?
- does the filter take advantage of polarization? would it be possible to make a filter out of two polarized lenses? if it is, that implies we can make a variable bandwidth filter, can we calibrate in the visible spectrum and then implement the IR-pass by twisting the lens?

Tuesday, March 3, 2009

eye see hot

update -- matt got the basic webcam display functionality working, but the lag is still pretty intense. around 1 second.

makes for particularly cool fractal feedback videos that propagate inward..

ps3 eye experimentation

we've unboxed the ps3 eye and have started futzing around with it on matt's ubuntu box in attempts to get basic drivers working.

so far, the camera has worked fine at 30fps on my macbook pro using macam. unfortunately, macam didn't provide a means for bumping the frame rate up to 60fps, so we'll just have to assume that the functionality works out of the box for now.

matt's already got the audio from the camera to play back in vlc, albeit with an incredible latency of around 5 seconds.

i have also started working on my final project for ce125, which is a convolution module in verilog. my courseload is starting to drive me a little bit insane, but to be completely honest, i'm surprised i made it this far into the quarter without losing my shit. sure, i'm behind on a couple of programs for ce110, but i've been getting pretty much straight a's on the homeworks and quizzes, plus i got 105% on the midterm, so i shouldn't be worrying too much.

the frustration seems to be coming from my existing projects that must be completed before i move in to scimp full force. the frustration also stems from excitement, though, as i can't wait to get to the meat of this project.

they say good things come to those who wait. so i want patience, damnit, and i want it now!

at least squarepusher is here to calm me down...

Monday, March 2, 2009

sound on sight


this entry marks the beginning of an academic journal kept by kevin nelson for the santa cruz interactive multitouch platform (scimp), a project for the masc group (micro architecture santa cruz) for research in interactive vlsi design.

this document exists primarily to document musings, notes, and slight tangents that i encounter as the project develops.

stay tuned. full time research starts at the end of march.

kevin // soundcyst => scimp