Optical: systems and elements – Single channel simultaneously to or from plural channels – By surface composed of lenticular elements
Reexamination Certificate
1999-04-09
2004-08-03
Mack, Ricky (Department: 2873)
Optical: systems and elements
Single channel simultaneously to or from plural channels
By surface composed of lenticular elements
C359S822000
Reexamination Certificate
active
06771422
ABSTRACT:
BACKGROUND
The present invention relates to enhancing the depth of field of an optical imaging system independent of its F# (f number).
The performance of all pattern recognition and tracking systems is limited by the depth of field of the optical imaging system used to acquire the images. Conventional optical systems require the aperture stop to be reduced in order to achieve a higher depth of field. Reducing the aperture causes the exposure (flux time integration time) to be reduced. In addition, reducing the aperture stop causes higher spatial frequencies of the object to be attenuated, thus degrading the image. Other image processing techniques have been used to overcome these obstacles. However, to date, all such image processing techniques to produce enhanced depth of field images are based on numerically intensive mathematical image processing algorithms that cannot be implemented in real time. Hence, such techniques are used as a post processing technique to produce images with an enhanced depth of field.
Adaptive optics technology does not fall neatly into any of the established engineering disciplines; it combines elements from optics (imaging systems and interferometry), electro-optics (photon sensing and modulation devices), electrical engineering, mechanical engineering, and chemistry. The use of active and adaptive optics terminology is not standard throughout the optic community. The literature often confuses and interchanges the usage of these terms. For example, as pointed out in Robert Tyson's text entitled “Principles of Adaptive Optics”, Academic Press, New York, 1991, many researchers differentiate them by bandwidth. They refer to systems operating below {fraction (1/10)} Hz as active and those operating above {fraction (1/10)} Hz as adaptive. This definition is used widely in the astronomy community. Other restrictions on the definition of adaptive optics have been seen. Many people skilled in the art consider adaptive optics to be restricted to coherent phase-only correction. The definition we will use to describe this invention, and it is one that is gaining more and more popularity, is that everything having to do with actively controlling a beam of light is active optics. As discussed in Tysons aforementioned book entitled “Principles of Adaptive Optics”, adaptive optics is a subset of the much broader discipline, active optics. The terms adaptive and active optics in this invention will be used as many contemporary workers skilled in the art tend to do throughout the current literature. The term adaptive optics is used when it specifically applies to wavefront sensing (sensing aberrations) and/or wavefront correction. In this invention, the broader term active optics is used to describe devices that can be used to control light—such as tunable filters, programmable waveplates and other spatial light modulators.
As discussed is several optical information-processing patents, pattern recognition is extremely sensitive to a variety of distortions including defocus. U.S. Pat. Nos. 5,485,312 and 5,111,515 are all optical information processing systems that can benefit from this invention that improves the depth of field. As discussed in this disclosure, all other optical information processing systems used for pattern recognition and tracking suffer from this drawback. This invention overcomes this obstacle by enabling a single image with a large depth-of-field to be used instead of trying to recognize or track out-of-focus objects.
As discussed in U.S. Pat. No. 4,141,652, various adaptive optics systems have been devised to improve resolution by correcting for distortions induced in light wavefronts by atmospheric disturbances and imperfections of the receiving optical systems. U.S. Pat. No. 4,141,652 relates to improvements in the Hartmann-type sensors. (See also U.S. Pat. Nos. 4,399,356 and 5,120,128.)
U.S. Pat. Nos. 4,935,614 and 5,026,977 describe double pass phase shifting interferometric adaptive optic systems which only operate with coherent light.
Other phase diversity techniques such as those disclosed in U.S. Pat. Nos. 5,384,455, 4,308,602 and 5,610,707 are based on numerically intensive algorithms and an adaptive optics post processing technique because they cannot be implemented in real-time imaging systems. Moreover, these phase retrieval techniques require sufficient spatial frequency terms in order to operate. Global convergence for extremum values is difficult to achieve. In addition, these inventions operate only on incoherent imaging systems and hence are limited in their application.
Although there are several patents awarded in the field of optical information processing, none take advantage of using adaptive optics to produce well-defined targets by enhancing the optical depth of field. Likewise, no other inventions in the field of adaptive optics is used to enhance the depth of field. Techniques reported in the literature to enhance the depth of field are post-processing techniques that cannot be implemented in real-time.
It is therefore an object of the present invention to significantly enhance imaging, pattern recognition and tracking of a very wide range of imaging systems, such as cameras, microscopes, machine vision systems, optical correlator systems, etc., especially in real-time.
SUMMARY OF THE INVENTION
The inventive optical imaging system comprises a plurality of photo-dector elements; means for measuring the amount of defocus aberration for each photo-detector element; and means for compensating for such aberration to produce an image with an enhanced depth of field independent of f number.
Whereas in conventional optical systems the depth of field depends on the focal number of the particular optical system, the inventive system enables all objects within the field of view to be viewed in focus. The novel active and adaptive optic techniques utilized by the present invention compensate for spatial and chromatic aberrations and consequently enable a large depth of field independent of the optical system's F#, especially in real-time. The enhanced depth of field in turn greatly enhances the ability of optical information processing systems to recognize and track patterns.
This invention is a novel method of enabling an optical imaging system to have a large depth of field independent of F#. The F# of an optical system is f/D, where f is the effective focal length and D is the diameter of the exit pupil of the optical system. It is well known that all imaging systems can be characterized in terms of its stops and pupils. The aperture stop is the element in an imaging system that physically limits the angular size of the cone of light accepted by the system and it therefore governs the total radiant flux reaching the image plane. It may be simply the edge of one of the lenses in the system, or it may be an opaque screen with a hole in it specifically introduced for that purpose. In a camera, the iris diaphragm acts as an aperture stop with a variable diameter.
The field stop is the element that physically restricts the size of the image (or field of view). It may be an opaque screen with a hole in it specifically introduced for that purpose, or as in a camera the film may effectively serve as the field stop. The entrance pupil is the image of the aperture stop, as viewed from object space, formed by all of the optical elements preceding it. Frequently it is a virtual image and thus is the “apparent” limiting element for determining the angular size of the cone of light accepted by the system. The exit pupil is the image of the aperture stop, as seen from image space, formed by all of the optical elements following it. The aberrations of a system, as well as its resolution, are often associated with the exit pupil. Ideally, for a point object, a spherical wave is launched by the exit pupil and converges to an ideal point image.
Any ray that emanates from an off axis object point and physically passes through the center of the aperture stop is called the chief ray. A chief ray is directed toward the
Becker R W
Mack Ricky
R W Becker & Associates
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