Detection systems for detecting obstructions in doorways
First Claim
1. A detection system comprising an emitter for emitting a beam of radiation, a detector for detecting the radiation of the emitter, and means for varying the radiation path length between the emitter and detector in response to a moving object and simultaneously varying the angle that the radiation path makes with at least one of the optical axes of the emitter and the detector, the radiation intensity transmitted by the emitter and detected by the detector being arranged to vary as a function of said angle in a sense such, that as the length of the radiation path reduces, the radiation intensity detected by the detector progressively decreases at least during the final stage of path length reduction.
2 Assignments
0 Petitions
Accused Products
Abstract
A detection system includes an infrared emitter (2) and an infrared detector (8) having optical axes (6) and (12) extending parallel to one another but being offset from one another. As the detector (8) and the emitter (2) approach one another the distance between them decreases but their angular separation increases. Accordingly, the increase in signal engendered in the detector as it approaches the emitter is countered to some extent by the greater angular separation. Accordingly, the net result is that any change in output of the detector resulting from a change in its spacing from the emitter is substantially reduced. Instead of the detector and emitter moving relative to one another they may be fixed and the light path between them varied by a moving reflector to achieve a similar result.
-
Citations
21 Claims
- 1. A detection system comprising an emitter for emitting a beam of radiation, a detector for detecting the radiation of the emitter, and means for varying the radiation path length between the emitter and detector in response to a moving object and simultaneously varying the angle that the radiation path makes with at least one of the optical axes of the emitter and the detector, the radiation intensity transmitted by the emitter and detected by the detector being arranged to vary as a function of said angle in a sense such, that as the length of the radiation path reduces, the radiation intensity detected by the detector progressively decreases at least during the final stage of path length reduction.
- 4. A detection system comprising an emitter for emitting a beam of radiation, a detector for detecting the radiation of the emitter, a reflector in the radiation path between said emitter and detector, and means for varying the radiation path length between the emitter and detector in response to a moving object and simultaneously varying the angle that the radiation path makes with at least one of the optical axes of the emitter and the detector, the radiation intensity transmitted by the emitter and detected by the detector being arranged to vary as a function of the angle in a sense such, that as the length of the radiation path reduces, the radiation intensity detected by the detector decreases.
-
9. A detection system comprising an emitter for emitting a beam of radiation, a detector for detecting the radiation of the emitter, means for varying the radiation path length between the emitter and detector in response to a moving object and simultaneously varying the angle that the radiation path makes with at least one of the optical axes of the emitter and the detector, the radiation intensity transmitted by the emitter and detected by the detector being arranged to vary as a function of said angle in a sense such, that the radiation intensity detected by the detector peaks when the path length intermediate the maximum and minimum path lengths and wherein the peak signal detected is less than 60 dB of the signal detected when the path length is at said minimum or maximum.
- 10. A detection system comprising an emitter for emitting a divergent beam of radiation and a detector having a divergent field of view, the emitter and detector being constrained for relative movement so that the optical axis of the divergent beam and the optical axis of the divergent field of view are maintained substantially parallel to one another with a substantially predetermined spacing between the two axes, the detector being arranged to generate an output signal which is a function of both distance between the emitter and detector along said axes, and the angle between a said axis and the line joining the emitter to the detector so that as a reduction in the distance between the emitter and detector acts to increase the output signal of the detector, an increase in angle acts to reduce the output signal.
-
17. A detection system comprising an emitter for emitting a divergent beam of radiation and a detector having a divergent field of view, the emitter and detector being constrained for relative movement so that the optical axis of the divergent beam and the optical axis of the divergent field of view are maintained substantially parallel to one another with a substantially predetermined spacing between the two axes, the detector being arranged to generate and output signal which is substantially equal at both maximum and minimum spacing between the emitter and detector, and which is a function of both distance between the emitter and detector along said axes, and the angle between a said axis and the line joining the emitter to the detector so that as a reduction in the distance between the emitter and detector acts to increase the output signal of the detector, an increase in angle acts to reduce the output signal.
-
18. A detection system comprising an emitter for emitting a divergent beam of radiation and, a detector having a divergent field of view, the emitter and detector being constrained for relative movement so that the optical axis of the divergent beam and the optical axis of the divergent field of view are maintained substantially parallel to one another with a substantially predetermined spacing between the two axes, the detector being arranged to generate an output signal in which the maximum output signal occurs between the maximum and minimum spacing between the emitter and detector and does not exceed 60 dB of the output signal produced at the maximum or the minimum spacing and which is a function of both distance between the emitter and detector along said axes, and the angle between a said axis and the line joining the emitter to the detector so that as a reduction in the distance between the emitter and detector acts to increase the output signal of the detector, an increase in angle acts to reduce the output signal.
-
19. A detection system comprising:
-
an infrared transmitter having an optical axis and providing an output which diminishes in intensity with greater angular deviation from its optical axis; an infrared receiver having an optical axis and responding to received light with lesser sensitivity with greater angular deviation from its optical axis; and two parallel surfaces relatively movable towards and away from one another while maintaining their parallel configuration, said receiver mounted rigid with one said surface with its optical axis directed at the other surface, and said transmitter mounted rigid with the other surface with its optical axis directed at said one surface and lying substantially parallel to but spaced from the optical axis of the receiver and in optical communication therewith.
-
-
20. A detection system comprising:
-
a transmitter having a main transmission axis and providing an output which diminishes in intensity with greater angular deviation from its main transmission axis; a receiver having a main axis; and two parallel surfaces relatively movable towards and away from one another while maintaining their parallel configuration, said receiver mounted rigid with one said surface with its main axis directed at the other surface, and said transmitter mounted rigid with the other surface with its main transmission axis directed at the said one surface and lying substantially parallel to but spaced from the main axis of the receiver and in communication therewith.
-
-
21. A detection system comprising:
-
a transmitter having a main transmission axis; a receiver having a main axis and responding to received light with lesser sensitivity with greater angular deviation from its main axis; and two parallel surfaces relatively movable towards and away from one another while maintaining their parallel configuration, said receiver mounted rigid with one said surface with its main axis directed at the other surface, and said transmitter mounted rigid with the other surface with its main transmission axis directed at said one surface and lying substantially parallel to but spaced from the main axis of the receiver and in communication therewith.
-
Specification