Hi to this awesome and helpful community,
This is my first post, so please don’t be to harsh on me
We’re going to build a multi-touch & fiducial table and decided on “rear DI”. That’s why we have to place IR LEDs or some IR Illuminator in our box. Here are some specifications of our table/box: the “screen” is 100cm (40") * 75cm (29.5"), so the diagonal is 125cm (49") and the height of the box is 91cm (36")
Is it easier to get a even illumination with IR illumnators or with LED panels placed around all sides of the box, shinning upwards?
Below i made a little sketch to illustrate the options i mean:
I’m thinking about building the panels with one LED for each inch, which would be 150LEDs in total.
I checked a lot of “LED theory” and it seems that almost everybody recommends the OSRAM SFH485(P), which has a radiant intensity of 48mW/sr and a angle of half intensity of +-40 degree.(http://catalog.osram-os.com/jsp/download.jsp?rootPath=/media/&name=SFH485p_Pb_free_2009_08_21.pdf&docPath=Graphics/00052522_0.pdf&url=/media//_en/Graphics/00052522_0.pdf)
I also found this one TSAL7600, which has a radiant intensity of 200mW/sr and a angle of half intensity of +-30 degree.(http://www.mouser.com/catalog/specsheets/tsal7600.pdf)
The TSAL7600 seems much better to me, even so it has a smaller angle of half intensity, it has four times the radiant intensity
Does anybody has experience with the second kind of LED’s?
The radiant intensities stated above are for I=1A. Do I have to check the radiant intensities for 1A or for 100mA. Sorry, I’m quite new to electronics.
Another thing is that at one page in the wiki (http://wiki.nuigroup.com/IR_LEDs) it says that the OSRAM SFH485P LEDs are the most popular, but on another page in the FAQ “What kind of LEDs are best and where can I buy them? “ (http://wiki.nuigroup.com/Frequently_asked_questions#What_kind_of_LEDs_are_best_and_where_can_I_buy_them.3F) it says that the radiant intensity should have a minimum of 80mw. But as I understand it, the OSRAM SFH485P has a radiant intensity of 48mw, so why is it the most popular LED for this purpose then?
Thank you very much and keep up the great work