how do IR sensors detect distance?

[blackbeard]

this is something that i've been wondering. how do IR sensors detect distance? i know that sonar detects distance by calculating the time it takes a sound wave to bounce off an object but since light travels at the speed of light i can't imagine that IR detects distance in the same way. most of what i find on the internet is the usual "they just do" explanation.

[ballbreaker]

i may be a bit wrong but i thing it can find distance by the angle of the light that hits back to the receiver theres a good tutorial on IR sensor here. check it out

[blackbeard]

oh ya i suppose there would be a good one here! i'll take a look

[amando96]

The closest you are to a wall, the more light is reflected back, the furthest you are, the less, they just measure how much reflected light there is 
And yes, colour does mess with readings sometimes, but those sharp IR detectors have excellent immunity to colour and sun light, they are worth the price.

[Razor Concepts]

The closest you are to a wall, the more light is reflected back, the furthest you are, the less, they just measure how much reflected light there is 
And yes, colour does mess with readings sometimes, but those sharp IR detectors have excellent immunity to colour and sun light, they are worth the price.

ehh... Sharp IRs dont really measure how much light is coming back, but where it is. Basically there is a little patch of IR sensing material. If the object is closer, the angle is greater, and the reflected IR will be concentrated towards one end of that material. If the object is farther, the angle is smaller, and the reflected IR is concentrated towards the other end of the material. The Sharp IR measures at what position the reflected IR is on its little sensor, and with that it can determine distance