I am using infrared emitter/detectors for my robot project.I was wondering if anyone could explain to me the meaning of the viewing angle of the emitter and its effect on the positioning of the sensors.
The name viewing angle is somewhat illogical here, since you can't see the light, but the terminology has carried over from visible light, so assume it was regular red LED's (or any other visible color).
Consider that the LED is a point source. Shine it onto something, it will make a circle of light, sometimes a very sharp circle, sometimes a very gradual fading out into the perifery.
The angle, or rather the angle of half intensity is found by measuring the amount of light in the brightest part in the centre.
At some distance from the centre, the incident light will have decreased to half of that in the brightest spot. Calculating the angle (of the inside of a sphere) with the point of light as the centre and the angle of the sphere where the light is half of the brightest, as mentioned before, yeilds the "viewing angle".
The effect of different angles is, that if the beam is narrow, you need to point it much more precisely, than if you use a wide beam, but on the other hand, you can do with less power then, since less beam is wasted by not hitting anything usefull.