Auto Focus Camera: Learn How it Works

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An auto-focus camera uses an infrared pulse to determine the distance to a target by measuring the reflected pulse. While all objects emit infrared radiation, the camera's emitted pulse helps distinguish the target from other sources of infrared. The camera typically operates at a different wavelength than that emitted by humans, similar to night vision technology. However, there is a concern that objects emitting similar infrared frequencies could interfere with the camera's ability to focus accurately. Additional camera features may help mitigate these potential focusing issues.
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Hi everyone,

An auto-focus camera emits an infrared pulse and detects the pulse reflected from the target, then it calculates the distance of that target from the camera (i.e. it can focus the target). As far as I know, all objects will emit infrared radiation, so what is the use of the pulse emitted by the camera? Or if I put it differently, even if the camera emits an infrared pulse, but can it receive another pulse from the target ? or even receiving pulses from another object which is not the target?
 
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But sometimes, the target of the camera may not be a person, right? (forgive me if I ask a stupid question...)
So, will the camera detect other infrared radiation and focus wrongly?
 
I imagine if you were taking a picture of something radiating the same frequency of light it could fool the camera.

Someone else here at PF more familiar with camera tech should be able to answer that.

Here's more info on auto-focus:

https://en.wikipedia.org/wiki/Autofocus

The camera may have other features that allow it to overcome various issues like this.
 
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