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US 4,053,934 AGranted
Measuring the quality of images
AssigneeNone recorded
InventorsPhilipp G. Kornreich, Stephen T. Kowel
Life of this patent
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AssigneeNone recorded
InventorsPhilipp G. Kornreich, Stephen T. Kowel
Estimating the term…
Method and apparatus for measuring the quality and sharpness of images and for using the measurement results to control parameters such as camera and projector focusing, range finding, optical system modifications and the like. In one embodiment, an image is formed on a medium which has an electrical property that varies predictably with the sharpness of an image incident on it. The property is measured and the derived electrical signal controls automatic focusing of objective and projection lenses, range finder settings, and the like. The invention relies on the discovery of an interaction between images, strain waves and electrical properties in certain devices which allows deriving an electrical signal whose magnitude corresponds to high spatial frequency Fourier components of the image. In addition to other useful characteristics, the electrical signal is at a maximum when the overall sharpness of the image is high and drops off significantly as the image becomes blurred. Alternately, high frequency components of the spatial Fourier transform of images are found by other means, e.g., optically, and the magnitude of these components is used as an indication of the sharpness of the images, and of other parameters of optical systems.
Apparatus for detecting the sharpness of an image comprising:
A method for detecting the sharpness of an image comprising:
A method for detecting the sharpness of an image comprising:
Apparatus for detecting the sharpness of an image comprising:
A system comprising:
A method comprising the steps of:
Apparatus for detecting the sharpness of an image represented by a beam at a selected plane transverse to the beam comprising:
Apparatus for detecting the quality of an image represented by a beam at a selected plane transverse to the beam comprising:
A method of detecting the sharpness of an image represented by a beam at a selected plane transverse to the beam comprising the steps of:
A method of detecting the quality of an image formed by an optical system comprising the steps of:
Dependencies are inferred from the claim text.
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Surveillance camera constructional details: optical details, e.g. lenses, mirrors or multiple lenses
Using image sharpness techniques , e.g. image processing techniques for generating autofocus signals: by analysis of the spatial frequency…
Optical systems or apparatus not provided for by any of the groups G02B1/00 - G02B26/00, G02B30/00: optical focusing aids
Image analysis to detect motion of the intruder, e.g. by frame subtraction: movement detection not involving frame subtraction, e.g. motion…
Term ended 11 Oct 1994 (estimated)
USPTO file history isn’t available for this patent, so only indexed dates are shown.
The invention relates to detecting and measuring the quality and sharpness of radiation images and to utilizing the resulting information. It finds particular utility in automatic focusing of cameras and projectors, in range finding, and the like.
In cameras and projectors, it is essential to properly focus an image in order to avoid loss of pictorial information. Focusing is usually manual, by adjusting the distance between the objective lens and the film in cameras, and by adjusting the distance between the projection lens and the image carrier in projectors. In some cameras focusing is eliminated by the use of the so-called universal focus lenses which do not require focusing adjustments within the distance range usually encountered by the amateur photographer. Such lenses, however, are a compromise between eliminating focusing problems and providing an image of optimum quality, and are therefore not satisfactory under all conditions. Attempts have been made therefore to provide various devices for automatically focusing conventional objective lenses, and similar attempts have been made for automatically focusing projection lenses. Some such devices rely on triangulation and measure the angle between the lines to a subject from two spaced-apart points on the camera (Pagel U.S. Pat. No. 3,442,193). Others rely on observing minute differences in the output of certain photocells between uniform and nonuniform distributions of light over their surface (Harvey U.S. Pat. No. 3,653,762). Still others rely on measuring the phase difference between different rays reflected from the subject to be photographed (Odone et al. U.S. Pat. No. 3,652,160). Still others rely on measuring the relative light intensity difference between two or more points of an image (Genahr U.S. Pat. No. 3,532,045 and Leitz U.S. Pat. No. 3,529,528). A survey of certain prior art focusing techniques can be found in Shin, I., Autofocus Camera, RADC Final Techn. Report TR-72-244, Oct. 1972, Defense Documentation Center No. AD-905-565L. In projectors, one automatic focusing device scans a line of the projected image and uses the count of certain transitions between light and dark as a measuring of focusing (Fenner U.S. Pat. No. 3,705,765).
While it is highly desirable to provide an indication of the sharpness of images, automatic focusing of cameras and projectors and automatic range finding, for various reasons having to do with complexity, reliability and effectiveness, no commercial devices of this type have enjoyed unqualified success. There is still a need for a way to detect and measure the sharpness and quality of images simply and reliably, and to utilize the result for accurate manual or fully automatic focusing and range finding, for modifications of optical systems, and the like.
FIG. 1 is a partly perspective and a partly block diagram view of a device which obtains a measure of the sharpness and quality of an image incident on it.
FIG. 2 is a partly plan and a partly block diagram view of an alternate device embodying the invention.
FIG. 3 is a side view of an experimental arrangement for measuring the sharpness of an image in accordance with the invention.
Certain embodiments of this invention utilize the discovery of an interaction between images, strain disturbances and electrical properties in certain media which is described in detail in the parent applications of which this application is a continuation-in-part and rely additionally on the discovery that under certain conditions the magnitude of the derived electrical signal varies predictably with the sharpness of the image. Additionally, the invention utilizes new types of interactions among images, strain disturbances and electrical properties, and utilizes certain optical interactions.
Referring to FIG. 1, a device which illustrates the principles of the invention comprises a substrate 20 of a material capable of undergoing strain disturbances that vary in time and space, e.g., fused quartz, a film 22 of a material that has a measurable property varying as a function of an image incident on it and as a function of strain disturbances present in it, such as a polycrystalline cadmium sulfide film deposited over a portion of the substrate 20 and acoustically coupled with it to undergo said strain disturbances, and two electrical contacts 24a and 24b which partly overlap the film 22 and are in electrical contact with it, but are separated from each other by a narrow exposed strip of the film 22. A conventional interdigital transducer 26 is acoustically coupled with the same surface of the substrate 20 that carries the film 22 to generate a surface wave 28 propagating as indicated along that substrate surface. The transducer 26 is driven at a selected frequency by a suitable signal source 30.
The electrical signals of interest are derived through a network 31 that includes a bias supply 32 connected to the electrical contact 24a through a current meter 34 shunted by a capacitor 36 and connected to the electrical contact 24b through a resistor 38 to establish a constant potential between the contacts 24a and 24b across the exposed strip of the film 22. Note that this configuration is similar to the conventional cadmium sulfide light meters used in photographic cameras, and measures in a similar manner the overall light intensity of an image incident on the exposed strip of the cadmium sulfide film 22. Thus, the D.C. current through the meter 34 is a measure of the overall light intensity of an image incident on the exposed strip of film 22.