Image analysis – Applications – Range or distance measuring
Reexamination Certificate
1999-10-30
2001-10-09
Couso, Jose L. (Department: 2724)
Image analysis
Applications
Range or distance measuring
C382S312000, C382S321000
Reexamination Certificate
active
06301371
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to object identification under diverse and changing light conditions. Specifically, it relates to a system for the detection and identification of objects, hidden marks, and faults.
BACKGROUND OF THE INVENTION
Night observation systems are well known in the prior art. The roots of these systems can be traced back to before World War II.
Night observation systems are generally divided into active and passive systems. Some night observation systems work by flooding an area under observation with infrared energy.
Active systems have an infrared filter that uses a special lens coating. When infrared light passes through a filter designed to transmit infrared light below 900 nanometers, the filter glows. An auxiliary source of infrared light can be used to illuminate the object under observation. Objects in the observation area reflect infrared energy back to the sensor in the imaging device. Since the glowing filter is visible and reveals the position of the light source, a disadvantage of these active systems is that the location of a covert observer may be revealed. Other active systems use light sources such as infrared lasers which do not require the concomitant use of a filter.
As technology developed some of the disadvantages of active systems were overcome by the use of passive imaging systems. Passive systems usually do not disclose the location of the observer, since they do not emit visible light. Due to their low resolution, the main disadvantage of these systems is the difficulty encountered in distinguishing the object under observation from background noise, such as infrared energy from other sources. Another example of a problem encountered with low resolution is that, in military situations, during combat maneuvers, camels can be confused for tanks.
There are currently at least two types of passive night vision systems.
One type, known as a thermo-imaging system, picks up the emission of heat energy from the objects under observation. A thermo-imaging system detects long wavelength, for example 8-14 micron, infrared radiation emitted from objects as a result of their temperature, usually −20° to +2500° F. A disadvantage of this type of system is that the resultant image lacks clear, identifying qualities. This is particularly disadvantageous in a law enforcement scenario where a police officer must be able to identify the suspect being imaged in order to maintain a proper chain of custody. With thermo-imaging systems, it is difficult not only to maintain a proper chain of custody but also to distinguish friend from foe. Another disadvantage of the thermo-imaging system is that distortion occurs when the system is exposed to visible or infrared light from, for example, a headlight, a flashlight or the sun. A further disadvantage of the thermo-imaging system is that most systems are designed to be used with an eyepiece for viewing. This decreases the peripheral vision and increases the vulnerability of the observer.
A second type of passive night vision system is called a light intensifier system. A light intensifier system takes a very low level of visible light and magnifies it until it is visible to the naked human eye. Unlike the other described systems, the light intensifier system works in the visible spectrum The light intensifier system does not work in a totally dark environment. Another difficulty with the light intensifier system is that the image produced is green, and usually “grainy” or blurred. Furthermore, distortion occurs when the system is exposed to visible or infrared light from, for example, a headlight, a flashlight or the sun. Light intensifier systems are usually constructed in a binocular or scope configuration which decreases the peripheral vision and increases the vulnerability of the observer.
Thus, both thermo-imaging systems and light intensifier systems have relatively low resolution and create a shadowy image, can be damaged when subjected to high intensity light sources, and may decrease the peripheral vision and increase the vulnerability of the observer.
An example of a hybrid system is that of a light intensifier system with laser illumination. This system uses the traditional, passive, light intensification method of imaging supplemented by an infrared laser light illumination of the field of view. The laser has the capability of “viewing” for great distances. However, the image is usually viewed through an eyepiece and appears green and grainy. Also, compared to the non-coherent light sources used in this invention, the laser does not provide as high a reflective factor or as wide an area of illumination.
With all of the conventional systems, it is difficult to obtain an accurate description of the subject or terrain under observation or to determine if the subject being viewed is holding a weapon.
Also, it is believed that none of the conventional systems accurately determine the distance of an object under observation from the point of observation. As a knowledge of the distance to an object is necessary for the determination of the size of that object, the distance to an object is critical for complete object identification. For example, determining the distance to an object and calculating the size of that object can help distinguish whether the object is an adult or a child.
Night observation systems have been disclosed by Meyers in U.S. Pat. Nos. 4,991,183; 4,853,529; 5,042,048; and 5,056,097. Meyers generally discloses an intensification system that uses laser light to supplement the available unseen light. This illuminates an area through the use of infrared lasers which generate coherent light in the observed area. The object under surveillance is displayed as a green image using an eye piece.
Pinson, in U.S. Pat. No. 4,947,044 for a method and apparatus for covertly viewing a target, disclosed the selection of a frequency band of infrared radiation having the least effective transmittance properties of all frequencies of infrared radiation in given atmospheric conditions to illuminate a target and the detection of the reflection of that selected frequency band of infrared radiation from that target. In Pinson, at sea level, all the bands have wavelengths of greater than 1.35 microns.
Other known systems, such as the one designed by Agema Infra Red Systems, use a thermo-imaging system with a video camera format that is used in surveillance applications as well as the thermo measurement of faults in the inspection of electronic or pressurized systems. Thermo-imaging systems have the disadvantage that the quality of the image decreases as the distance of the object under surveillance from the imaging device increases. It is difficult to determine, in a short time, the accurate distance to the object under observation. As the object under observation moves, it is also difficult to follow that object with precise accuracy.
In U.S. Pat. No. 4,264,927 Raymond et.al. disclose an apparatus for scanning and recording information on railroad cars moving at high speed in order to facilitate the identification of the railroad cars. The apparatus employs a television type camera having a pick-up device with high resolution. In Raymond, the inventors note that an advantage of their system is the avoidance of the need for special labels and devices.
In U.S. patent application Ser. No. 08/517,378, Jones and Lyman introduced an imaging system comprising a non-coherent light source, a filter means, a first imaging means, and a first display means. That application also introduced a range finder having a low power diode, a lens system, a second imaging means, a second display means and a precalibrated scale. Furthermore, that application introduced a movement sensor having a display driver circuit board, a scan threshold detector, a microchip, and a microcontroller.
In the present invention, Jones and Lyman introduce improvements and additional applications to the invention disclosed in U.S. patent application Ser. No. 08/517,378.
An advantage of the invention disclosed in U
Jones Mark F.
Lyman James C.
Costa John G.
Couso Jose L.
Do Anh Hong
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