That is quite a question. The light from the laser goes out in a 27 degree cone. But a diffractive optical element spreads the light to what we say is a 45 degree pyramid. A wall at 1M will have a square of illumination 1M on a side. But that 45 degrees is the edge of full power. It's where the roll-off starts to happen, At 60 degrees there is really not much detectable light, but to insure there is no light, you have to go most of the way to 90 degrees off center. Generally this roll off doesn't matter. But if you were to place a reflective object within the rolloff area you could get some crosstalk issues depending on the optical nature of that object.
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