Data processing: measuring – calibrating – or testing – Measurement system
Reexamination Certificate
1998-11-19
2001-12-11
Shah, Kamini (Department: 2857)
Data processing: measuring, calibrating, or testing
Measurement system
C340S601000, C340S602000, C340S905000, C250S338100
Reexamination Certificate
active
06330519
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates generally to a sensor system to detect visibility and, more specifically, to a visibility sensor system having a removable sensor head that may be removed for servicing.
Reduced visibility on highways due to fog or blowing dust has often been the cause of tragic traffic accidents. Fog, especially in mountainous regions, has a tendency to build up in patchy dense pockets. At highway speeds, in particular, a driver may suddenly find himself within one of these patchy dense fog pockets.
The ability to adequately warn drivers of dense fog is highly desirable. If adequate warning is provided to drivers, drivers may then reduce their speed based on the density of the fog. Adequate warnings will reduce loss of life.
Several optical and non-optical methods for determining the presence of fog are known. Most, however, are not suitable for highway visibility sensors. There are several optical systems that may be used. Radar and lidar systems are used to gather general weather data. Such systems are too expensive, bulky, insensitive and difficult to use on a highway. Closed circuit television has limited use for visibility detection, but it cannot function at night and requires monitoring by an operator. Airports commonly use transmissometers. Transmissometers measure the transmission of a light beam traveling a given path. Transmissometers are very expensive and require considerable maintenance and thus are not suitable to detect patchy highway fog. Coulter counters are often used in clean room monitoring. Coulter counters are very expensive and have high maintenance and power consumption requirements.
Non-optical devices such as triboelectric current sensors depend on the flow of gas rubbing against an electrode. Fog, however, frequently occurs in quiet atmospheric conditions. Spark discharge sensors require sensor electrodes to continually be kept clean and thus maintenance costs are prohibitive. A dosimeter-type particle density measurement device does not provide real-time data.
Another optical device for measuring fog is a nephelometer. Known nephelometers have expensive optical systems and are very large in size. The optical system requires constant maintenance to clean the windows through which the optics are directed.
In certain situations, it may be desirable for the vehicle to have a visibility detection system associated therewith. It would likely be cost prohibitive to provide highway visibility detection systems across the country. Therefore, it is desirable to provide a visibility sensor system associated with the vehicle.
On ships, it is difficult to determine visibility due to lack of background for comparison. For ships, it may also be desirable to locate a visibility sensor on the ship.
It would therefore be desirable to provide a visibility sensor system that overcomes the drawbacks of the prior art. Particularly, it would be desirable to provide a visibility sensor system that is inexpensive, has low maintenance, and is reliable to endure the conditions experienced on a highway.
SUMMARY OF THE INVENTION
It is therefore an object of the invention to provide an improved visibility detection system. More specifically, it is an object of the invention to provide a visibility detection system suitable for incorporation on an automotive vehicle.
According to one embodiment of the invention, a detector includes a housing having a first hollow opening and a second hollow opening. A first light source is fixed within the housing and directs light through the first hollow opening to a sample volume outside the housing. A first light detector receives light reflected from the sample volume through the second hollow opening. A controller is coupled to the first light source and the first detector. The controller determines an output indicative of visibility from the light received by the first light detector.
In another embodiment of the visibility sensor system, a display may be coupled to the controller to warn drivers of the existence of fog ahead. The display may also indicate a safe driving speed through the fog.
In yet another embodiment of the invention, a means for compensating for the deterioration of the first detector may be included. To compensate for the deterioration of the first detector, a second light source may be placed adjacent to the first detector and illuminate the first detector with a predetermined amount of light. The controller then calculates the deterioration of the first detector in its visibility calculation. In another aspect of the invention, a means for determining deterioration of the first light source may be concluded. The means for compensating for deterioration of the first light source includes a second detector located adjacent to the first light source. The second detector would provide feedback to the controller as to the deterioration of the light source. The controller would then compensate for any deterioration of the first light source in its calculation for visibility.
In yet another embodiment of the invention, a method for detecting visibility comprises the steps of illuminating a sample volume of air from a first hollow opening within a housing using a first light source, detecting the amount of light scattering from the volume of air with a first detector that receives light through a second hollow opening and calculating a visibility factor based upon the light scattering from the fog particles in the volume of air.
In one aspect of the method for calculating visibility, the calculation may take into consideration deterioration of the first detector and the first light source.
In still another embodiment of the invention, a removable sensor head comprises a sensor enclosure defining a first optical port and a second optical port. A first circuit board is coupled to the sensor enclosure. A first connector is coupled to the first circuit board. A light source is coupled to the first circuit board, which positions the light source within the first optical port. A second circuit board is coupled to the sensor enclosure. A second connector coupled to the second circuit board. A light detector is coupled to the second circuit board. The second circuit board positions the light detector within the second optical port. A calibration memory is coupled to the second circuit board.
In a further embodiment of the invention, a visibility sensor assembly has a housing having a sensor head opening. A removable sensor head assembly is removably coupled to the housing within the sensor head opening. The sensor head assembly has a sensor enclosure and a connector. An electronics module is coupled to the sensor head through the connector.
In yet another embodiment, a rain sensor is provided, which is configured to close one or more shutters that cover the first and second openings. This has the advantage of minimizing the entry of contaminants.
In yet another embodiment, a sensor enclosure is provided which is configured to produce an airflow therethrough such that contaminants are swept through the enclosure. This has the advantage of minimizing the contamination of the light source and/or light detector.
One advantage to providing a removable sensor head is that the maintenance costs are reduced because the sensor head may be easily replaced.
One advantage of the present invention is that no optics or windows are required within the hollow openings through which light is transmitted and received. This eliminates a major problem for optical sensor systems. That is, eliminating the persistent need for cleaning of the optics or windows.
Another advantage of the present invention is that short periodic onsite inspections for calibration are not required. The sensor system provides a means for compensating for the deterioration of a detector and light source. The sensor system also can provide a self check and report the results to a central monitoring station.
Another advantage of the present invention is that a variety of communication options may be supported. For example, communication
Mierzwa Kevin G.
Sentec Corporation
Shah Kamini
LandOfFree
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