Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Processes of preparing a desired or intentional composition...
Reexamination Certificate
1997-05-28
2001-02-27
Michl, Paul R. (Department: 1714)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Processes of preparing a desired or intentional composition...
C340S933000
Reexamination Certificate
active
06194486
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to new roadway marking systems, and, more particularly, to an enhancement to roadway marker paints that renders the road markers more distinguishable from the adjacent and/or underlying pavement when viewed at microwave/millimeter wave radiometric frequencies. The invention also relates to a method for ascertaining the presence of roadway markers and information coded in such markers by application of passive radiometric energy sensitive inspection apparatus within an electronic control and/or warning system.
BACKGROUND
Roadway marking systems have long been used to provide vehicular equipment operators with pertinent information through the medium of roadway markers. As example, the white stripe painted on the roadway in front of a stop sign, familiar to the lay reader, provides a vehicle operator, the driver, with a physical limit or boundary that the driver's approaching vehicle should not exceed in coming to a full and complete stop in obedience to the stop sign. On multi-lane roadways, the lanes are delineated by roadway markers. And, at major airports service roads and corridors are often distinguished, in addition to signal lamps, by painted lines marking the borders to the service road, providing a visible guide for the pilot. The foregoing are but a few of the most common applications.
In more recent experience, roadway markers have also been adapted as part of vehicular guidance and control systems. The information provided by the roadway markers is used to automatically issue an alarm or steer and/or position a moving vehicle. Sensors on the vehicle detect a marked path along a roadway and the associated control equipment on the vehicle is able to automatically correct the vehicle's steering should the sensor detect the vehicle's departure from the marked path. From time to time newspapers report of experimental automobile control systems that are intended to automatically control and guide a vehicle's travel along a highway, eliminating the need for the driver's complete attention.
Examples of the foregoing appear in the patent literature. The system in U.S. Pat. No. 5,202,742 to Frank et al carries a laser radar carried on the vehicle to detect reflective markers along a roadway. The laser beam is scanned over the roadway and the associated detectors, which receive light reflected from the roadway markers, are used by associated control equipment on board the vehicle to guide the vehicle relative to the roadway markers. Another system is presented in U.S. Pat. No. 4,947,094 to Dyer et al. In the Dyer system a linear charge coupled device (CCD) carried by an industrial warehouse vehicle, such as a forklift, monitors the position of a track, such as formed by a painted line on the warehouse ceiling overlying the roadway. The CCD images that line and that imaging allows the control equipment in the system to steer the industrial vehicle along the track.
Though painted white stripes are often used, the better roadway markers are formed of a thermoplastic material, supplied by the manufacturer as minute plastic granules or beads, that is heated to place the material into the liquid form, which can flow. Often small spheroidal glass particles are mixed into the ingredients as part of the liquid. That hot liquid is coated or extruded in a thin strip onto the roadway surface, where the plastic material is allowed to cure, that is, solidify and harden. The plastic material is designed to seep into the rough surface and pores characteristic of pavement materials, such as cement and asphalt, and hardens to form a firm grip or bond to the pavement.
Such marker is relatively wear resistant, enduring the heavy pounding and friction of automobile tires. It resists the effects of snow and rain. It also resists to the deleterious effects of sunlight, including that from ultra-violet radiation. And it maintains its color for years, ensuring a visible contrast with the surface of the roadway. Although those who apply the marker to the roadway refer to the thermoplastic film simply as “paint”, an analogy to house paint, a reference that carries forward in the subsequent description, roadway markers are understood as a serious field of endeavor.
It is noted that the exact composition of the various thermoplastic ingredient materials suitable for pavement marker application, not known to the present applicants, is well known to those skilled in the road marker art. As becomes apparent those details are not necessary to an understanding of the present invention and, hence, need not be further described. Those interested in learning more on that subject, may make reference to the technical literature in that field.
The foregoing marker and control systems make use of reflected light, that is, the visible region of the electromagnetic energy spectrum, and that light originates either naturally in the environment or is generated by a light source in the detection system. Other forms of energy, though not perceptible directly by human senses, are known and have also been applied in detection schemes. As one finds from the scientific literature, the electromagnetic energy spectrum extends over a wide range of wavelengths, extending at least from the shortest wavelengths, those in the ultra-violet region and below, to and beyond the longest wavelengths in the infra-red regions. One finds visible light in this spectrum, a region which human eyes are able to detect and which enables our vision, and also radio waves. The microwave spectrum lies in a portion of that radio spectrum; and in an end portion of that microwave spectrum, one finds the millimeter wave region.
Microwave and millimeter wave energy is emitted naturally from all objects. It is also incident on our Earth from outer space, and from the Earth's atmosphere, a gaseous object, irradiating, among other things, the roadways on which we travel. Since outer space is very cold, approximately four degrees Kelvin, and since the amount of energy emitted is proportional to the emitting objects physical temperature, very little energy is incident from outer space. For the most part the incident microwave/millimeter wave energy incident on the roadway is from the atmosphere itself, which serves or acts roughly speaking like a forty degree Kelvin emitter at a 94 GHz frequency. This energy, in part, is reflected from the materials on which it is incident, including the roadway and markers on the roadway. Those materials also emit a like kind of energy, and, since those materials are typically at “room temperature”, 300 degrees Kelvin, they appear warmer, higher in temperature, than those materials that principally reflect the “cold sky”.
In fact, according to Planck's radiation law, any perfectly absorbing body emits radiation at all frequencies of the energy spectrum. For most natural objects in our environment, such radiation is relatively high in the infra-red region of the energy spectrum, proportional to the fourth power of the object's physical temperature. At microwave/millimeter wave frequencies, the energy is much less, varying only directly with the temperature. Though less intense, that microwave/millimeter wave energy is detectable and measurable with properly designed microwave/millimeter wave radiometers.
Microwave/millimeter wave radiometric detectors are microwave/millimeter wave receivers that detect the total power received. A microwave/millimeter wave radiometer is, in effect, a highly sensitive total power receiver. The receiver receives its signals from a directional antenna, such as a microwave/millimeter wave horn antenna, whose receiving “footprint” or field of view is directed at the element or area to be observed. The magnitude of the signal received by the radiometer is proportional to the temperature of the object under observation, and/or the temperature reflected by the object, depending upon the percentage and types of objects within the antennas footprint and the object's emissivity &egr;, the latter being equal to (
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Eninger James E.
Hauss Bruce I.
Quon Bill H.
Yujiri M. Larry
Goldman Ronald M.
Michl Paul R.
TRW Inc.
Yatsko Michael S.
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