Author Topic: IR emitter angle of half intensity. Which beam angle is more effective  (Read 842 times)

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Offline sublitiTopic starter

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Maybe silly question..

lets say we have an ir emitter and ir receiver in the same room, and we point the ir emitter 180 deg away from the receiver, then we push the button and rely on the fact that the ir light bounces from the walls of the room and hits the receiver...well ok lets just say we point it anywhere in the room. So my question is, would different beam angles have benefits over others in this scenario ? Would the reflected light from a narrow beam bouncing off of several walls be more efficient than a wider beam angle given that the radiated power exiting the led is equal for each ir led no matter what angle it has ?

If i think this through..if we consider the walls as mirrors and a narrow beam angle like a laser, then the multireflected light would only hit the ir receiver if it hits it by "accident", because we got lucky and the light was refleceted just about at the right spot. But if you think more about it...the traveling beam also glows and this glow gets reflected everywhere...so the indirect glow will hit the receiver even without the actual focused laser hitting it directly.

Now if we consider a wide beam..the wider the beam the easier it will hit the receiver from direct reflections, since it is so wide no lucky reflections are required.

Still i dont know..
 

Online Kleinstein

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Re: IR emitter angle of half intensity. Which beam angle is more effective
« Reply #1 on: November 14, 2019, 09:58:10 pm »
Most surfaces would give a non directional scattering.  Mirror like reflection would be mainly from something like glass, polished metal and a mirror.

So for the indirect path the beam angle usually does not make a large difference.
 

Offline CatalinaWOW

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Re: IR emitter angle of half intensity. Which beam angle is more effective
« Reply #2 on: November 15, 2019, 01:10:15 am »
While your logic is largely correct, you didn't take one more important step.  Those highly reflective surfaces will deliver almost all of their energy to the next surface encountered, which will either be a diffuse reflector or will repeat the process.  As Kleinstein says, for the case you are analyzing it makes little difference.  One case that I encounter more than I wish is when the battery is near the end of its life and overall power output is much lower. Murphy's law says that this will happen when the stores are closed or some other thing makes a battery change inconvenient.  I am often trying to stretch the last few uses out of a remote's battery by aiming it straight at the receiver, and in this case a narrower beam helps. 
 

Offline sublitiTopic starter

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Re: IR emitter angle of half intensity. Which beam angle is more effective
« Reply #3 on: November 15, 2019, 11:17:13 am »
Ah i totaly forgot scattering. Ofc most of the light reflected from non shiny objects is scattered instead of producing direct reflections. My example was to ideal.

I thought that in this scenario different beam angles maybe makes a difference even if it is tiny, but if it doesnt, well, ok.

thanks
 


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