Radiant energy – Infrared-to-visible imaging
Reexamination Certificate
2000-12-07
2002-07-16
Hannaher, Constantine (Department: 2878)
Radiant energy
Infrared-to-visible imaging
C250S332000, C250S334000, C250S338100, C250S201200, C250S221000
Reexamination Certificate
active
06420704
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to a system and method for providing recognition of an approaching object located in a distant no-light environment and, more specifically, to a low-cost near-infrared (IR) imaging system that, by capturing sufficient infrared light photons from the distant object, is capable of increased infrared imaging sensitivity and range.
2. Description of the Prior Art
Visible and infrared imaging systems are known in the art for their usefulness in mitigating the effects of impaired night vision. Impaired night vision is a problematic and potentially dangerous situation caused by a reduced range of vision under conditions of darkness and is all too familiar an experience for automobile drivers, particularly drivers over the age of 40. For example, during the cover of darkness 20/20 vision is typically reduced to approximately 20/50 where a reduction in vision of this magnitude can result in the late perception of poorly illuminated obstacles located at a distance from a driver.
A number of military and commercial approaches that mitigate the effects of impaired night vision have been developed in the art using different light sources, ranging from ultraviolet to infrared, in conjunction with imaging cameras sensitive to light in the range of visible to far infrared. One such approach employs the use of low level visible light intensifiers within night vision scope devices and is based on technologies originally developed for military applications. Commercial versions of such night vision scope devices, like the Night Vision Pocketscope™ manufactured by ITT Defense & Electronics, amplify visible light using a microchannel plate as an electron multiplier and a photocathode as a detector. The night vision scope devices are relatively inexpensive and can provide significant enhancement in range on a clear night and, if used in conjunction with an illuminator, can also provide vision enhancement during overcast conditions. Unfortunately, however, night vision scopes of this type are not suitable for the large-scale manufacture required by the automotive industry and other industries that have high-volume production demands.
Another approach known in the art for solving the problem of impaired night vision is the use of thermal imaging. As described in the publication “Give Me the Night (Vision),” by K. Jackson, AutoWorld Magazine, October 1998, thermal imaging technology is certainly not new to the military and, in fact, has been used in some form or another for at least the past four decades. However, more and more, thermal imaging technology is being commercially exploited. For example, General Motor's 2000 Cadillac DeVille uses long wavelength infrared detectors that can operate in the one to twelve micron wavelength and, as a result, have the capability to detect thermal energy rather than light photons. In other words, instead of detecting an object by sensing the infrared illumination (light photons) that the object reflects, a warm object is thermally detected through its black body radiation. An advantage of such a system is its ability to detect—even when obstructed by foliage, etc.—objects having thermal emissions, such as humans, deer and automobile engines. However, a system of this type is disadvantaged because of its inability to detect fallen trees or other objects that do not emit thermally. A further disadvantage of such a system is its significant expensive. Thermal imaging systems typically require very expensive uncooled infrared detectors, such as resistive bolometers, that detect the heat energy of objects invisible to the human eye. Thermal detection involves focusing the thermal (heat) energy onto the uncooled infrared detector with sensor optics designed to pass IR wavelengths. Known approaches to uncooled infrared detectors include, a vanadium oxide 2D uncooled infrared detector array manufactured by Boeing Corporation; a yttrium barium copper oxide (YBCO) bolometer that has been demonstrated by MSI Inc; and Raytheon Corporation's approach to the uncooled infrared detector, is a pyroelectric capacitor array that requires a thermoelectric cooler as well as a chopper wheel, an approach that has been employed in the 2000 model GM Cadillac DeVille. The lowest cost approach to uncooled infrared detectors, however, is a micro electro mechanical system (MEMS) cantilever beam array. The cantilever beam array is a low-mass bimetallic diving board structure similar to an accelerometer where the amount of beam flexure is a function of its temperature and the temperature depends on the amount of incident infrared.
Still another approach known in the art for combating the effects of impaired night vision is the use of near-infrared sensors with illumination. A night vision imaging system employing the use of near-infrared sensor with illumination generally consists of an illuminator that illuminates a distant scene and a near-IR camera that generates an image of the distant scene. One such system developed by Ford Jaguar Inc., uses a charge coupled device (CCD) camera and a near-infrared (NIR) spotlight. The Jaguar system works by integrating the NIR spotlight with conventional high-beam lamps. And by using a 680×500 pixel charge-coupled device (CCD) monochrome digital camera that is sensitive to infrared light not visible to the human eye, the Jaguar system is able to capture an image of an object located in a dark distant scene. The Jaguar approach and others like it are perhaps a more practical approach to night vision imaging, mostly due to the availability of low cost components. But, because of the high sensitivity of conventional CCD detectors to visible illumination, modern CCD and like cameras typically have short exposure times that range from approximately {fraction (1/60)}to {fraction (1/4000)}of a second and, as a result, the camera's range is limited. Thus, the camera's ability to enhance a driver's visibility of on-coming traffic or up-coming road conditions, if traveling at speeds of 60 mph or more is limited since it takes approximately 250 feet for an automobile traveling at 60 mph to come to a complete stop. Moreover, for infrared wavelengths above 700 nm, the sensitivity of CCD detectors is considerably reduced to only approximately 15% to 25% of its peak response. This reduction prevents the camera from recognizing objects at more than approximately 200 feet away during cloud cover, fog or after sunset.
A better approach to near-infrared sensors with illumination, currently being used in search and rescue applications and pursued by Daimler-Chrysler Inc., is to use a pulsed laser diode as an illuminator and to gate the CCD camera shutter synchronously with the laser pulses. This approach has several advantages, including an achievement of 4 times higher peak optical power. The gating makes it possible to see through particles to approximately four to five times the range of the human eye and other vision systems. And, since the laser is polarized, filters can be used to enhance visibility in rain, fog, snow, etc. However, while such gated viewing systems can readily satisfy desired performance requirements, they are also too expensive for the average consumer.
Finally, other approaches known in the art include millimeter microwave (MMW) imaging and LIDAR, however, both of these approaches are far more expensive to implement than those approaches previously mentioned.
Thus, a near-infrared (IR) imaging system that is capable of increased infrared imaging sensitivity and range under conditions of darkness while providing a low-cost approach that would allow the average consumer to take advantage of enhanced night vision viewing is highly desirable.
SUMMARY OF THE INVENTION
The preceding and other shortcomings of the prior art are addressed and overcome by the present invention that provides a system for providing recognition of an approaching object located in a distant no-light environment. The system includes an illumination source f
Berenz John J.
Dunbridge Barry
McIver George W.
Hannaher Constantine
Israel Andrew
TRW Inc.
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