Cerupcat, you’re saying that the ideal would be something arround the +/-48 Degrees? So i don’t understand one thing,
why are the OSRAM SHF485 so popular when they only have +/-20 Degrees?
In the same line of thought, would it be better to use 850nm or 880nm? and why?
Tks.
cerupcat - 11 August 2008 01:30 PM
A few of us talked it over and basically here’s a summary of what we agreed on:
Ideal Specs:
Wavelength: 850nm (or 880nm, but 850nm would be better) - Both of these are easily seen by cameras and visible light filters can be easily found for these wavelengths. The lower the wavelength, the higher sensitivity which will equate to the higher ability to determine the pressure.
Radiant Intensity: Minimum of 80mw. The ideal is the highest radiant intensity you can find, which can be much higher than 80mw.
Angle: Sometimes the specs will show both full and half angles. So I’m putting both, but they are equivalent.
Maximum half angle: +/- 60 degrees
Maximum full angle: (60 + 60) = 120 degrees
Anything less than +/- 48 will not take full advantage of TIR, and anything above +/- 48 degrees will escape the acrylic. In order to ensure there is coverage, going beyond +/- 48 degrees is fine, but anything about +/- 60 is really just a waste as (60 - 48 = +/- 12 degrees) will escape the acrylic.
If you have any questions, feel free to ask. We appreciate your willingness to include the community.
behem0t: That’s because people are mistaking SFH485 for SFH485P. They both have the same total radiant flux (optical power) but the latter one has a spread of +-40 degrees.
I’m a little bit confused, if you check SFH485P
they talk about # Angle, half:80° but if you check the datasheet the half +-40º. I should trust the datasheet, right?
Also i found the SFH485 Datasheet and they
have a Radiant intensity of 160mW/sr @100mA. Wich is the radiant for the SFH485P?
Sorry for all those questions but i’m really confused.
Cerupcat says 850nm leds would be better than the 880nm one’s. Why?
And if so, can you suggest any good 850nm one’s? OSRAM preferably.
I called the company, they are currently out of stock but should have more within a few weeks :( but they have updated the literature on their website for the IR lights and are going to be releasing to the people who purchased the lights the actual documentation that we seek, hopefully all the questions about the lights used can be answered then.
Hi Larky, that’s a great question. Subjectively, there doesn’t seem to be any “leaking” with our setup, but we’ll take a closer look at this, just in case. We are also planning on testing a new power supply setup that has a dimming capability. I don’t know yet if dimming is required or useful, but it’s something we can take a look at. Right now, we’re busy with some other research projects, but should be able to resume our multi-touch work in mid-October.
My LEDs are working great. This is my first ftir screen I have buitl, so I have no room for comparison. I will have some videos when my table is finished in a week and a half. These ribbons were a great find.
So it would be possible to use the same approach as the guys at touchfactor but with an LCD instead of an projector?
Do i need both the rosco and the Sulky Solvy to get this to work or can somebody explain what the rosco and the sulky solvy does?
How hard do you need to press to get the blobs?
So it would be possible to use the same approach as the guys at touchfactor but with an LCD instead of an projector?
Do i need both the rosco and the Sulky Solvy to get this to work or can somebody explain what the rosco and the sulky solvy does?
How hard do you need to press to get the blobs?[/quote
Gurra, i’ve been experimenting with the LED ribbons and and LCD using FTIR. I’ll post a full review here tonight.
so please hurry up!
