| 摘要 |
<p>PROBLEM TO BE SOLVED: To accurately judge a changed detection zone by detecting in a plurality of directions by each two sets of optical means, energy detection means, and amplification means, by separately setting the gain of the optical means for judging the output ratio of both signals. SOLUTION: Optical means 1 and 2 are provided with lenses 1a-1c and 2a-2c for focusing energy from each of three directions. The optical gain of the lens 1a is set to the same value as that of the lens 2a, the optical gain of the lens 1b is set to half that of the lens 2b, and the optical gain of the lens 1c is set two times that of the lens 2c. Energy means 11 and 21 are arranged respectively at the focuses of the lenses 1a-1c and 2a-2c, and amplify the output signal by the amplification means 12 and 22. A detection zone-judgment means 31 in an alert circuit means 30 compares output signals S1 and S2 with each other of the amplification means 12 and 22, and judges that signals are those due to the change in incidence energy from detection zones 1A-1C (2A-2C) in the cases of S1=S2, S1=1/2S2, and S1=2S2, respectively.</p> |
