How do we ensure that IR beams in IR proximity sensors reflect directly back to the sensor?

Question

I know in a proximity sensor an infrared beam is sent out and it is reflected back to a sensor where it does time calculations. Given the laws of reflection, I would’ve guessed that the IR beam would just reflect in random directions upon hitting anything other than a flat surface perpendicular to the proximity sensor. How is this issue resolved?

Tagging this physics but it could easily be engineering

In: 3

Answer 1

ELI5

Your buddy Sam is standing in the middle of a dark room. You’re standing over in a corner. You shine a flashlight on Sam.

Can you see Sam from your corner? Sure. Because the light from your flashlight bounced off Sam and back toward you.

But now, put the flashlight down, still aiming at Sam. And walk to another corner. Can you still see Sam?

Yes, because the light from the flashlight bounces off Sam in ALL directions.

The light from the flashlight doesn’t go ONLY back toward the flashlight after bouncing off Sam. It goes in all directions.

Answer 2

ELI5

Your buddy Sam is standing in the middle of a dark room. You’re standing over in a corner. You shine a flashlight on Sam.

Can you see Sam from your corner? Sure. Because the light from your flashlight bounced off Sam and back toward you.

But now, put the flashlight down, still aiming at Sam. And walk to another corner. Can you still see Sam?

Yes, because the light from the flashlight bounces off Sam in ALL directions.

The light from the flashlight doesn’t go ONLY back toward the flashlight after bouncing off Sam. It goes in all directions.