Smoke detector utilizing ambient-light sensor, external sampling volume, and internally reflected light

1. A smoke detector comprising:

a housing;

disposed within the housing, a light source configured to (i) direct light outside of the housing, and (ii) emit an interior portion of light within the housing substantially without emission therefrom;

disposed within the housing, one or more light detectors configured to detect light from the light source that is reflected back into the housing, at least one said detector being configured to detect light from the interior light portion within the housing;

disposed at least partially within or on the housing, an ambient-light sensor for sensing an ambient light level outside of the housing; and

an evaluation circuit for determining the presence of smoke particles outside the housing based at least in part on (a) the detected light, (b) a luminance of light detected from the interior light portion, and (c) at least one of (i) the sensed ambient light level or (ii) a temporal evolution of the sensed ambient light level.

2. The smoke detector of claim 1 , wherein the presence of smoke particles outside the housing is determined based in part on at least one of a luminance or a rate of change of luminance the detected light.

3. The smoke detector of claim 1 , wherein the ambient-light sensor senses at least one of visible or infrared light.

4. The smoke detector of claim 1 , wherein the housing defines an opening for emitting therethrough the directed light and admitting therethrough light reflected from the directed light, the opening not having a window disposed therein.

5. The smoke detector of claim 4 , wherein light from the interior light portion is reflected by a portion of the housing proximate the opening.

6. The smoke detector of claim 1 , wherein the housing comprises a window, substantially transparent to a wavelength of light emitted by the light source, for emitting therethrough the directed light and admitting therethrough light reflected from the directed light.

7. The smoke detector of claim 6 , wherein light from the interior light portion is reflected by the window.

8. The smoke detector of claim 1 , wherein the light source and the one or more light detectors are portions of a single electronic component.

9. The smoke detector of claim 8 , wherein the electronic component comprises a proximity sensor.

10. The smoke detector of claim 1 , wherein the light source and the one or more light detectors are not portions of a single electronic component.

11. The smoke detector of claim 1 , further comprising a gas sensor disposed at least partially within or on the housing.

12. The smoke detector of claim 11 , wherein the presence of smoke particles outside the housing is determined based in part on at least one of (i) a gas concentration sensed by the gas sensor or (ii) a temporal evolution of the gas concentration sensed by the gas sensor.

13. The smoke detector of claim 11 , wherein the gas sensor is configured to sense at least one of carbon monoxide or carbon dioxide.

14. The smoke detector of claim 1 , wherein the light source emits at least one of visible or infrared light.

15. The smoke detector of claim 1 , wherein the evaluation circuit is configured to determine the presence of a non-smoke physical obstruction outside the housing based at least in part on at least one of a luminance or a rate of change of luminance of the detected light.

16. The smoke detector of claim 15 , wherein the evaluation circuit is configured to determine the presence of a non-smoke physical obstruction outside the housing based in part on a luminance of light detected from the interior light portion.

17. The smoke detector of claim 1 , further comprising a manual test button disposed on the housing and electrically connected to the evaluation circuit, wherein, after actuation of the manual test button, the evaluation circuit performs a test sequence based at least in part on the luminance of the detected light.

18. The smoke detector of claim 17 , wherein the test sequence is based in part on a luminance of the detected interior light portion.

19. The smoke detector of claim 1 , wherein (i) the light source comprises a broadband light source emitting light over a range of wavelengths, and (ii) the one or more light detectors comprise a plurality of light detectors each sensitive to light over only a portion of the range of wavelengths.

20. The smoke detector of claim 19 , wherein the broadband light source comprises a white light-emitting diode.

21. The smoke detector of claim 1 , wherein (i) the light source comprises a plurality of light emitters each emitting light of a different wavelength, and (ii) the directed light comprises each of the different wavelengths.

22. The smoke detector of claim 21 , wherein the presence of smoke particles outside the housing is determined based in part on a difference between a luminance of a first wavelength of the detected light and a luminance of a second wavelength of the detected light, wherein the second wavelength is different from the first wavelength.

23. The smoke detector of claim 1 , wherein the one or more light detectors comprise a plurality of light detectors each sensitive to light of a different wavelength.

24. The smoke detector of claim 1 , further comprising a fault-detection circuit for automatically testing the smoke detector at least in part by comparing a signal generated by light detection by one or more said light detectors with a fault threshold derived from the luminance of light detected from the interior light portion, a fault being indicated if the signal generated by light detection by one or more said light detectors falls below the fault threshold.

25. The smoke detector of claim 1 , wherein the evaluation circuit utilizes, for determining the presence of smoke particles outside the housing, (i) a background signal derived from the luminance of light detected from the interior light portion, and (ii) a smoke threshold set higher than the background signal.