DIY oximeter?

[Madejyathink]

I just chose that post icon face because it's blue. :p

I'm wondering if it's possible to make my own oximeter (like the ones they clip on your finger to read O2 saturation, except I don't need a pulse with it). I know it's just reading the amount of red and infrared light that goes through your finger, because how much of that light is absorbed is proportional to how much oxygen is in your blood (the less there is, the bluer/darker it is).
So it would involve a red and and infrared LED, and it would have to have some device that can sense the percentage of light received compared to a control that I could set (probably a healthy person's finger). Said device is the main thing I'm wondering about, I don't even know if it exists separately and if I could buy it.

It's not that I'm not willing to shell out $50 or so for one already made, I'm just curious to see if I can actually make one myself. I think it'd be pretty neat.

[Mantikore]

sounds like a pretty difficult task.

the logic i would put behind it is:
light shines through your finger from an IR source. the IR reciever picks up the non absorbed IR light. the IR reciever is a photovoltaic thing but for IR waves. This converts it to electricity. The voltage produced would then be connected onto a computer. The lower the voltage, the higher the O2 concentration. It would function a bit like a home made laser microphone. use youtube for those guidse

im not exactly sure how youll be able to calibrate it though. youll need to have known concentrations of O2 to calibrate the system, which is difficult in itself. you cant just use water dissolved with O2 either, since oxygen isnt really dissolved in the water, but carried by the haemoglobin. there would also be a limit to the amount of O2 you can test. obviously no oxygen will have the same amount of IR recieved as produced. youll have to determine whether the relationship between voltage and O2 is linear, inverse, or logarithmic