Smoke detector chamber boundary surfaces
Device for optically detecting smoke and implementing thereof. Apparatus and methods for detecting the presence of smoke in a small, long-lasting smoke detector are disclosed. Specifically, the present disclosure shows how to build a very compact housing around the smoke detector while keeping the reflections from the housing structure to a very low value while satisfying all the other peripheral needs of fast response to smoke and preventing ambient light. This allows very small measurements of light scattering of the smoke particles to be reliable in a device resistant to the negative effects of dust. In particular, geometrical optical elements, e.g., cap and optical defection elements, are disclosed.
1. An apparatus for detecting smoke within a compact footprint detector which propagates light substantially away from a smoke detector chamber, the apparatus comprising:
a first light source;
a first photodetector disposed substantially proximal to the first light source;
non-volatile logic for performing:
receiving a first signal from the first photodetector; and,
determining the presence of smoke at least based on the first received signal; and
a cap having an upper and lower surface that substantially covers the smoke detector chamber;
wherein, the lower surface is at least shaped substantially like a conic section.
2. The apparatus of claim 1 , wherein the cap is is disposed in a first plane, the first light source in a second plane, and the first and second planes are substantially parallel to one another.
3. The apparatus of claim 1 , wherein the conic section is a parabola, at least in part.
4. The apparatus of claim 1 , wherein the conic section is an ellipse, at least in part.
5. The apparatus of claim 1 further comprising a first light emitting diode have a spectral intensity centered about a first wavelength.
6. The apparatus of claim 5 further comprising an array of optical deflection elements disposed substantially in a circle around the outer radius of the cap.
7. The apparatus of claim 6 wherein the array of optical deflection elements is substantially wing-shaped.
8. The apparatus of claim 6 further comprising an anti-reflective coating disposed on at least one of the cap and array of optical deflection elements.
9. The apparatus of claim 8 wherein the coating is centered about the first wavelength.
10. The apparatus of claim 1 , further comprising a substrate in which the cap is mechanically coupled thereto.
11. A method for detecting smoke within a compact footprint detector which propagates light substantially away from a smoke detector chamber, the apparatus comprising:
providing light from a first light source;
detecting the light on a first photodetector disposed proximal and coplanar to the first light source;
covering the first light source and the first photodetector with a cap, the cap having an upper and lower surface;
defining a smoke detector chamber by a volume between the cap, the first light source, and the first photodetector;
receiving a first signal from the first photodetector;
determining the presence of smoke at least based on the first received signal which is based on scattered particulate matter, at least in part; and,
reflecting light off the lower surface of the cap which geometrically reflects light away from the smoke detector chamber.
12. The method of claim 11 , wherein the lower surface of the cap is shaped substantially like a conic section, at least in part.
13. The method of claim 12 , wherein the conic section is a parabola, at least in part.
14. The method of claim 12 , wherein the conic section is an ellipse, at least in part.
15. The method of claim 11 wherein the first light source is a first light emitting diode have a spectral intensity centered about a first wavelength.
16. The method of claim 15 further comprising disposing an array of optical deflection elements in a substantially circular form around the outer radius of the cap.
17. The method of claim 16 wherein the array of optical deflection elements is substantially wing-shaped.
18. The method of claim 16 further comprising depositing an anti-reflective coating onto at least one of the cap and array of optical deflection elements.
19. The method of claim 18 wherein the coating is centered about the first wavelength.
20. The method of claim 11 , further comprising mechanically coupling the cap to a substrate.
21. An apparatus for geometrically directing light away from a smoke detector chamber comprising:
a cap having an upper surface and a lower surface, the cap being shaped substantially like a circle as viewed from a top-down perspective towards the upper surface; and
an array of optical deflection elements disposed in a substantially circular form around an outer radius of the cap;
wherein, the lower surface is at least shaped substantially like a two-dimensional conic section as view from the side of the cap with a lower bound at an origin of the circle.