Radiant energy – Photocells; circuits and apparatus – Optical or pre-photocell system
Reexamination Certificate
1998-06-26
2001-02-20
Lee, John R. (Department: 2878)
Radiant energy
Photocells; circuits and apparatus
Optical or pre-photocell system
C250S226000, C385S012000
Reexamination Certificate
active
06191413
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates generally to photodetector systems responsive to ambient light, and more particularly, to a photodetector system wherein the electrical output signal is responsive to the position of a light source with respect to a location distal from the photodetector.
In some light sensor arrangements, particularly of the type used in vehicles, it is desired that the direction of incident light be determined by a photodetector device located at a distance from the point at which the monitoring of the light is desired. It is desired that sunlight impinge upon a diffuser located about one and one half inches from the light sensor device.
The diffuser overlies a plurality of sensors each covering a respective zone of the field of view desired to be monitored. In an embodiment where four sensors monitor four respective zones, the sensors are tightly packed and each diffuiser and its corresponding light sensor employs a dedicated hollow tube, along which the light from the diffuser is propagated.
A significant problem is the transmission of a sufficient amount of light down the connecting tube that would reach the photodetector. The surface finish of the tube is very important. Initially, it would appear that a diffuse finish, which would scatter the incoming light in many directions, would effectively cause the light to be propagated along the hollow tube. However, by using a polished surface on the inside of the tube, the amount of light that reaches the photodiode is increase dramatically. A highly polished tube functions almost like a mirror. In fact, if the light were parallel to the tube, a perfectly polished surface would behave exactly like a perfect mirror. The phenomenon is called grazing incidence.
SUMMARY OF THE INVENTION
The foregoing and other objects are achieved by this invention which provides, in accordance with a first apparatus aspect thereof, an arrangement for detecting an electromagnetic energy. In accordance with the invention, there is provided a photodetector having a photodetector input for receiving electromagnetic energy, and a photodetector output for producing an electrical characteristic responsive to the electromagnetic energy. Additionally, a hollow conduit having a first end arranged to receive a received portion of the ambient electromagnetic energy, and a second end arranged in the vicinity of the photodector input, whereby a portion of the received potion of the ambient electromagnetic energy impinges upon the photodetector input.
In one embodiment of the invention, the first end of the hollow conduit is terminated orthogonal to an axis of the first end. A diffuser is optionally disposed in the vicinity of the first end of the hollow conduit.
In a further embodiment, the first end of the hollow conduit is terminated at an angle other than orthogonal with respect to an axis of the first end, whereby the received portion of the electromagnetic energy has a magnitude that varies in response to the direction of incidence thereof with respect to the axis of the first end. Again, a diffuser is optionally disposed in the vicinity of the first end of the hollow conduit.
In a still further embodiment, there is provided a light blocker arranged in the vicinity of the first end of the hollow conduit, whereby the received portion of the electromagnetic energy has a magnitude that varies in response to the direction of incidence thereof with respect to the axis of the first end. Again, a diffuser is optionally disposed in the vicinity of the first end of the hollow conduit.
In a highly advantageous embodiment of the invention, the hollow conduit has a highly polished interior surface. In a further embodiment, the hollow conduit has an interior surface that is adapted to impart a predetermined spectral characteristic to the portion of the received portion of the electromagnetic energy that impinges upon same. The predetermined spectral characteristic corresponds, in certain embodiments, to a predetermined spectral response of a human eye.
In a specific illustrative embodiment of the invention, the hollow conduit has length and radius dimensional characteristics that are predetermined to effect a desired combination of a first portion to of the received portion of the electromagnetic energy that impinges upon an interior surface of the hollow conduit, and a second portion of the received portion of the electromagnetic energy that propagates directly through the hollow conduit
The hollow conduit is not limited to be cylindrical, or even to have a circular or otherwise continuous cross-sectional configuration. It may have a determined curvature or curvatures along its length.
In a multi-sensor embodiment of the invention, there is provided a further photodetector having a further photodetector input for receiving further electromagnetic energy, and a further photodetector output for producing a further electrical characteristic responsive to the further electromagnetic energy. Additionally, a further hollow conduit is provided having a respective first end arranged to receive a further received portion of the ambient electromagnetic energy. The further received portion of the ambient electromagnetic energy corresponding to ambient electromagnetic energy that is incident from a direction other than that which impinges upon the first end of the hollow conduit. A respective second end of the further hollow conduit is arranged in the vicinity of the further photodector input, whereby a portion of the further received potion of the ambient electromagnetic energy impinges upon the further photodetector input.
The hollow conduit and the further hollow conduit each have a respectively associated spectral characteristic in a specific illustrative embodiment of the invention.
In some embodiments, as previously discussed, a lens is disposed in the vicinity of the first end of the hollow conduit. The lens may be an annular lens having a determined angular sensitivity.
In accordance with a further apparatus aspect of the invention, there is provided an arrangement for detecting an ambient light. In accordance with this further aspect of the invention, there is provided a photodetector having a photodetector input for receiving the ambient light, and a photodetector output for producing an electrical characteristic responsive to the ambient light. A hollow conduit has a first end arranged to receive a received portion of the ambient light, and a second end arranged in the vicinity of the photodector input, whereby a portion of the received potion of the ambient light impinges upon the photodetector input. In addition, there is provided a light modulator disposed at the first end of the hollow conduit for imparting a directional sensitivity characteristic to the received portion of the ambient light.
In a specific illustrative embodiment of the invention, the light modulator is integrally formed with the hollow conduit, and may be in the form of a predetermined angular termination at the first end of the hollow conduit. Alternatively, or in conjunction with the angular termination, there may be provided a lens, illustratively an annular lens.
In other embodiments, the light modulator includes an axially protruding portion having an axial dimension that varies with angular position about an axis of the hollow conduit. Such a light modulator serves to impart an angular sensitivity characteristic to the apparatus of the invention.
The hollow conduit has an interior surface extending along at least a portion of its length, the interior surface having a predetermined surface finish. In some embodiments, the interior surface finish has a polished characteristic. In other embodiments, or in conjunction with polished internal surface portions, the interior surface finish has diffuse characteristic. In a specific illustrative embodiment of the invention, interior surface finish has a predetermined spectral characteristic. A diffuser is provided in some embodiments, arranged in the vicinity of the first end of the hollow conduit for dispersing the
Lee John R.
Pyo Kevin
Rohm & Monsanto, PLC
LandOfFree
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