Optical: systems and elements – Single channel simultaneously to or from plural channels – By surface composed of lenticular elements
Reexamination Certificate
2003-06-23
2004-11-30
Mai, Huy (Department: 2873)
Optical: systems and elements
Single channel simultaneously to or from plural channels
By surface composed of lenticular elements
C359S621000, C359S626000
Reexamination Certificate
active
06825986
ABSTRACT:
TECHNICAL FIELD
The invention refers to the field of optics (precisely to the methods and means of optical modification of electromagnetic radiation) and can be widely applied at forming of optical imaging of the objects (mainly of spatially extended ones) within incoherent light with the purpose of quality improvement of the perceived images.
PREVIOUS TECHNICAL LEVEL
According to the technical level common acknowledgement is attributed to the method of forming of an optical image in the incoherent light, which is based on the application of focusing optical elements (e.g. a biological subject's lens or the objective of movie and photo cameras).
One of the ways of partial removal of the defects detected consists of diminishing the numerical aperture of the optical elements used (i.e. diminishing of the size of entrance pupil of the optical system). However, this method causes a decrease of illumination in the image formed, proportionally to the decrease of the entrance pupil's area, as well as leads to lowering of optical system's resolution in general.
Another method of object's-optical image's forming within incoherent light as well known from the technical level, is based on the change of transparency of the optical element in the direction from the center toward the peripheral area of the entrance pupil. In particular, in case of Gaussian law of transparency amendment, the dimensions of diffractive image of a point object decrease and consequently, resolution of the whole optical system increases and accordingly the quality of the formed image of original object improves. (J. Ojeda-Castaneda at ol., “High Focal Depth By Apodiration and Digital Resporation”, Appl. Optics, 27, No. 12, 1988; M. Mino, Y. Okano “Improvement in the OTF of Defocussed Optical System Through the Use of Shaded Apertures”, Appl. Optics, 10, No. 10, 1971).
Nonetheless, similar to the cases mentioned above, the present method acknowledged from the technical level, decreases the impact of focusing errors only partially (in case of shifting of original object from the plane of optimal focusing of the optical system or in case of the said object's extension along the optical axle of the system) due to certain extent of reduction of the formed image's illumination.
We know another way of optical image forming of an extended object within incoherent light along with the device of realization that secures the feasibility to diminish the error of defocusing through implementation of light rays of the specific phase mask (U.S. Pat. No. 5,748,371).
The technical solution mentioned implies one or several lenses to form the image on the surface of optical-electronic converter. In the meanwhile, one of the main planes of the optical system has a cubic phase mask installed, by means of which optical transfer function is being changed (i.e. optical motion of the rays is being distorted) for the said system (that forms the image) so that it (optical transfer function) remains practically constant at defocusing of the optical system inside a relatively wide range. Further on, the formed distorted image is being fixed with the help of optical-electronic converter and the final image without any distortion is restored from it by means of accorded spatial filtration with assistance of a digital filter accomplished hardware-wise or in a numerical form through a PC.
The method and device for its implementation analyzed in the present report allow in the course of accomplishing procedure to decrease affecting of defocusing errors over the quality of object's formed image as well as permit accounting and lowering of residual aberrations of the optical system.
Disadvantages of the quoted known technical solutions should be attributed to the higher requirements to the quality of optical-electronic converter because of the necessity to secure numeral ization of the signal in every particular point of the image not lower than 10 . . . 12 bits in order to receive high quality image. At the presence of noise of the receiver and/or at decreasing the number of quantization levels of the signal, the quality of restored image considerably deteriorates and the effect of depth enlargement of sharply imaged space is getting decreased.
Besides, in the known technical solutions analyzed above, the distortions of a point's imaging brought in to the optical system by means of a cubic phase mask are defined by individual derivatives (conforming to the pupil coordinates) from the function of a (x
3
+y
3
) kind. It means that directions of the distortions mentioned to the considerable extent coincide with directions of distortions caused by the defocusing which leads to “smearing” of the restored image of the point source in case of shifting of the latter from the focus of optical system.
As the closest to declared subjects of the invention one might consider a method known from the technical level, dealing with forming of the optical image of an extended object within incoherent light and the device for its implementation that are based on the combined application of amplitude and cubic phase masks (U.S. Pat. No. 6,097,856).
According to this method the following procedures are accomplished in series inside the optical system equipped with at least one lens: pre-set distortion of the rays' optical motion (i.e. modification of optical transfer function of the said system) by means of the amplitude-phase mask inserted to the system; optical-electronic conversion of the intermediate distorted object's image formed by optical system and following deduction of distortions brought in by amplitude-phase mask and by optical system in general through accomplishing of accorded spatial filtration of the intermediate image mentioned afore.
A device meant to form optical image of an object within incoherent light (to implement the method described above) includes an optical system with at least one lens as well as the placed in series along the rays' motion direction facility to distort the optical motion of the rays (i.e. to change the optical transfer function of the said system) in the form ′of amplitude-phase mask, optical-electronic converter of the intermediate distorted image generated by optical system and finally a device for deduction of distortions brought in by amplitude-phase mask and optical system in general. The last named facility is digitally realized in the PC in form of totalized accorded spatial filter (used for the purpose of coordinated spatial filtration of distorted intermediate image). These technical solutions carry the same disadvantages as attributed to the method analyzed and the device for its implementation according to the U.S. Pat. No. 5,748,371.
It is worth emphasizing that every technical solution quoted above requires digital processing of the image formed that incurs additional computing devices and extra time to process initial data. Not only this complicates the structure of the optical system, but as well excludes the chance to receive a restored image in real time scale (meaning impossibility to apply the known technical solutions in the systems that require higher speeds of initial data's processing).
In addition to that, distortions in the imaging of point light source, caused by insertion to the system of cubic phase mask (which function of phase delay looks like: &Dgr;&PHgr;=k(x
3
+y
3
)), are defined by individual derivatives of the mentioned function according to the pupil's coordinates “x” and “y”, meaning that they are proportional to “x
2
” and “y
2
”. In the meanwhile, distortions brought in by defocusing are proportional to “x” and “y” accordingly and possess the identical direction.
In this regard, the quality of restored image considerably depends on the value of defocusing and consequently, it is not feasible to restore the ideal image of the source, especially in the case of a spatially extended object.
INVENTION EXPOSURE
The basis of declared invention has been formed by the problem of creation of such a me
Ashkinazy Yakov Mikhailovich
Cheglakov Andrei Valerievich
Schetnikov Anatoly Alekseevich
Greenspan Myron
Lackenbach & Siegel LLP
Mai Huy
Obschestvo s Ogranicennoy Otvetstvennostiju <<INSMAT Tekno
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