ir distance sensor matrix

hi!

i would like to build a matrix of about 12 x 8 ir sensors. between 4 ir sensors there should be 1 ir led.

now the circuit should allow each ir led to be turned on separately and while its on taking the measurements of the 4 (or even 16) ir sensors around it.

i plan to use the following components: osram SFH 485 P http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail?name=475-1470-ND osram BPW34FA http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail?name=475-1072-ND

so, my question is, what kind of setup to use to make this efficient and cheap.

thanks

try searching the board for analog multiplexers for the sensors, and shift registers for the led's.

someone postet some links which got deleted? huh...

anyway: yes sure, i was reading trough the forum and other sources and i know the idea of building a grid of e.g. a couple of 74hc595 and 4051.

http://natebu.wordpress.com/2007/06/01/board-layout/ features pretty much what i want to build, except, i would switch the leds for IR.

but maybe someone has an idea for a strategy to optimize data gathering for such a setup. as it is actually unimportant to be able to drive each led separatly. so there could be a clock which cycles trough the leds, enabling 4 phototransistors. (b/c trough a shiftregister you dont exactely know which led is shining atm)

but if there is no pattern fur such a seutp maybe this makes no sense at all, then sorry.

besides i gonna build a setup with shiftregisters and multiplexers, but if someone has an inspiring idea, let me know...

but you do know which led's are shining with a shift register, because only the ones you turned on will be on. just keep track of them and you'll know which state they are on.