| 摘要 |
PROBLEM TO BE SOLVED: To provide a smoke detector that reduces an amount of reflection light on an incidence surface of a prism used in a chip LED, efficiently takes a light emitting beam into the prism and allows a smoke detection space to be irradiated with the light emitting beam.SOLUTION: A chip LED 24 and chip PD 26 are surface-mounted to a circuit substrate 22, diffusion light from the chip LED 24 is converted into parallel light due to a light emitting side prism 28, and a smoke detection space 20 is irradiated with the parallel light. Scattering light due to smoke from the smoke detection space 20 is reflected and converged by a light reception side prism 30 to be incident upon the chip PD 26. An incidence surface of the light emitting side prism 28 is a concavity curve incidence surface 36 making an angle of incidence of light small, for example, is a part of a spherical surface with a light emitting point Q as a center, and a reflection surface thereof is a parabolic reflection surface 38 with the light emitting point Q as a focus point. A reflection surface of the light reception side prism 30 is a parabolic reflection surface 44 with the light reception point as a focus point, and an emerging surface thereof is a concavity curve emerging surface 46 converging the light to the chip PD 26, for example, is a part of the spherical surface with a light reception point R as a center.SELECTED DRAWING: Figure 2 |
