LED Sensing ~ BI-Directional LEDs Part – I Sunday, 3 May, 2009
Posted by Taha in Hardware, My Progress.Tags: bi-directional, concept, electronic, electrooptical, han, Hardware, IR, jeff, led, Leds, multi, Multi-touch, multitouch, natural user interface, nui, sensing, touch, Webcam
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In my quest to find other methods of input detection for multi-touch and multi-modal hardware i came across another technique made famous by Jeff Han it is the use of LED s as bi-directional sensors. This technique is in no means new, it know fact that LED s can behave in such a way that, they act as sensors, when they are reverse biased. The theory behind how this all works is explained below.
Update… Thursday, 25 December, 2008
Posted by Taha in My Progress.Tags: electro, electrooptical, electropitcal, IR, LCD, matrix, multitouch, optical, sensor
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Well lately I’ve been in the process of developing and designing an electro-optical method of deploying Multitouch to LCD panels, as opposed to the traditional IR Cam version of MT. An electro-optical unit has significant benefits when compared to the use of the traditional IR Cam based systems. Firstly it reduced the form factor required, when using the traditional IR we are limited to having a large form factor, which is dependent on viewing angle used on the IR Camera. However if we employ an electro-optical device it reduces that form factor significantly.
The electro-optical device that I’m referring to is a custom designed IR sensor matrix that connects to the the back of an LCD and it provides a high resolution, high frame rate Input capturing solution. Essentially the electro-optical unit eliminates the need for a IR cam. In much of a similar fashion to that made by Microsoft (thinsight). Where my solution differs is that Thinsight employs DI technique where it uses proximity sensors which contain both an IR emitter and IR detector, there by effectively halving their resolution. What i aim to do is employ DSI or a combination of FTIR and LLP to eliminate the need for IR emitter on sensor matrix. Thus doubling the number of sensors.
So basically below are a few rendering of the setup im trying to achieve.
IR Frame… Thursday, 12 June, 2008
Posted by Taha in Hardware, IR Frame, My Progress.Tags: arrays, frame, IR, ir lights, lights, screen, tests
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Hey guys/gals sorry for the lack of posts…. i’ve just been busy with the project and various other things. lets get on to the IR frame. The IR frame is constructed using an aluminum U channel, bought from homedeopt.
IR Markers(pens) Wednesday, 4 June, 2008
Posted by Taha in General, Hardware.Tags: IR, ir leds, markers, pen, shf485
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2 days ago while searching for a cheap mirror to diy a surface mirror…. i came across led light key chain which i modded to make them IR pens simply by replacing the original white led with OSRAM SHF485. Below are some pictures i took of the process. Its pretty simple to follow just unscrewed the plastic casing and replaced the led…
Let there be light… Friday, 30 May, 2008
Posted by Taha in Hardware, Leds, My Progress.Tags: circuit, circuit design, IR, ir emitters, Leds, pcb, soldering
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When it came time to choose the leds there were only a limited number of choices, and since the most popular on NUIgroup forums is the OSRAM SHF485, I went with that.
A bit of background when picking IR emitters…
For everyone else out there when picking leds dont look at that their power for a measure of their luminosity. But rather look at their radiant intensity, which is measured in mW/sr. Typically radient intensity of 100+ is sufficient for for FTIR, on the other hand for DI you want both luminosity as well as dispersion angle, Osram SHF485’s have a radiant intensity for 160mW/sr.
On a side note, you also need to keep in mind the lens on top of the led it self and the angle IR emmits from the led it self. For FTIR its an narrower beam is prefered of around ±20° and for DI a wider angle beam is prefered ±40°, so if you are creating a DI setup then Osram SHF485P would be the better choice.
