IR Emitter - Regarding Angle of Half Intensity

Hi.

I am doing a proximity project where I chooses Vishay IR Emitter.

http://www.vishay.com/ir-emitting-diodes/

I found a term "Angle of Half Intensity" which I need to understand for angle. My understanding is attached.

Please advise me if my understanding is right or wrong?

Thanks in advance.

Yeah it is absolutely correct..
Half Intensity refers to the viewing angle rating as specified by the LED manufacturer. This simply states that at X degrees the LED intensity will be ? as intense as it would be at 0 degrees. Our high-brightness & high-contrast design allows the actual visible angle to be much larger than the ? intensity angle.

Thanks Vicky.

Regards.