| 摘要 |
PURPOSE:To enable efficient focusing of infrared rays emitted from the human body without projection of shadow of an infrared ray detection element by dividing a concave mirror into two parts near one focus plane thereof passing through the mirror center and then, putting it together so that respective focuses coincide with one another to form a compound concave mirror, at the focal point of which the infrared ray detection element is arranged. CONSTITUTION:An incident light I1 parallel to the optical axis P1 of a split mirror 11 and an incident light I2 parallel to the optical axis P2 of a split mirror 12 converge on the focus F. A change in infrared rays incident from two directions is detected simultaneously with a infrared ray detection element 2 and a human body detection signal is outputted from a human body detection circuit based on the output of the infrared ray detection element 2. It is so arranged that optical paths of upper incident lights I1 and I2 focused with a compound concave mirror 3 is open in the incident direction and a focus F is positioned between the optical paths of the incident lights I1 and I2 while the infrared ray detection element 2 is placed thereat F. Thus, the incident lights I1 and I2 converge on the focus F without being intercepted by the infrared ray detection element 2 thereby providing a highly sensitive human body detector with a better focusing efficiency by the compound concave mirror 3. |
