IL194783A - System and method for imaging with extended depth of focus and incoherent light - Google Patents

Description

and method for imaging with extended depth of focus and incoherent light Xceed Imaging 187193 METHOD FOR IMAGING WITH EXTENDED DEPTH OF FOCUS AND INCOHERENT LIGHT FIELD OF THE INVENTION This invention relates to optical imaging with extended depth of LIST OF REFERENCES Zalevsky Mendlovic and Progress in Zalevsky and Mendlovic Super Springer JOSA 1463 Opt 204 Gartner and Introduction to Fourier Optics New York BACKGROUND Imaging with a large depth of focus is desirable in many including and various detection a region of longitudinal positions at which an object can be sharply imaged is and in the larger the imaging the smaller its depth of and the smaller the imaging the larger its depth of For lens has a limited depth of but in the extreme case of small aperture it behaves as a pinhole and therefore practically provides a very large depth of the pinhole high depth of focus comes at a price of low lateral resolution and low energetic In point 2 spread function of pinhole is proportional to where A is a light D is a pinhole and is a distance between the aperture and a light detection such PSF yields the depth of focus proportional to resolution proportional to energetic efficiency proportional to a while having a very large depth of focus owing to very small aperture at the same time has a low resolution and a low energetic GENERAL DESCRIPTION There is a need in the art for an imaging allowing imaging with a relatively large depth of high imaging and high imaging energetic A presented here novel constructed by the has adaptations and useful for such The main idea of the invention consists of at least two replications of an chirp such that these replications are substantially the same but are created at different locations within the aperture It should be understood that substantially the same replications signify the same phase distribution of optical field generated by the this field matches with itself of autocorrelation The amount of a shift between the replicas within the aperture plane corresponds to a certain spatial frequency in an imaging plane the As a a large depth of focus is provided for this spatial The inventors have found for useful a large depth of such that of the may be combined with a super resolved In the field of in the field of super resolved spatial degrees of freedom are recovered by sacrificing other degrees of such as wavelengths and For large depth of focus is somewhat related to longitudinal super With respect to the large depth of it can be obtained not only by the aperture in the form of According to some embodiments of the it can also be obtained by an aperture with an array of randomly distributed or with a or with both an array and a as well as by other A large depth of focus technique based on me use of a random also called random can be somewhat advantageous over technology based on in the extreme case of a small each of the lenses does not produce a substantial quadratic phase and therefore it can be redundant in some the invented technique for large depth of focus and imaging does not rely on it is but relies rather on a random plate placed in the aperture plane and devoid of optical The energetic efficiency of the technique can be much larger than that of a single The technique uses imaging with an instantaneous modulation transfer function in a form of a sequence of which spatial frequencies can be In preferred embodiments of the the super resolving result is obtained by in some embodiments mechanical of the aperture plane with the random The scanning technique may be selected such that all spatial frequencies are presented in the resulting image and no digital processing is Turning back to the random plate in the aperture it can be composed out of an opaque plate with randomly distributed optical windows creating a random transmission blocking or it can be composed out of a transparent plate with randomly distributed diffusing islands creating a random phase distribution out of a or it can be composed out both a random pinhole pattern and a It should be that the term random is used here in connection with the technique of it is used to refer to patterns which produce a characteristic autocorrelation as it will be clear from The random plate presents by itself a special kind of optical spatial In preferred the random distribution is such that at least half of the energy passes For the totally random spatial O 4 its still has a spike as in the case of a single the inventors have found a way to concurrently obtain a relatively high energetic efficiency half instead of almost zero in the pinhole camera and large depth of without the resolution is still because the which is the absolute value of the OTF the optical transfer function of the coherent transfer of the plate consists of a single high spike and a few lower the inventors have included an option to scan the aperture plane with the random plate and integrate in time the intensity at the detector into their The scanning yields imaging and allows for concurrently obtaining extended of high spatial and energetically efficient It should be that the super resolution can be obtained in an in which no image processing is in some embodiments the may be obtained with the use of image The super resolution applied in the described approach can be categorized as time according to one broad aspect of the present there is provided an optical arrangement for use in imaging with a large depth of said optical arrangement comprising an aperture and a replication unit configured for providing a plurality of replicas of an input optical field such that said replicas include at least two replicas that are of substantially the same phase distribution and are created at different regions of the aperture unit In preferred embodiments of the the replication unit comprises at least first and second symmetrizing units configured for providing the at least two replicas of the input optical field while sequentially symmetrizing the input optical field projected on said aperture unit with respect to first and second centers of The first synimetrizing unit may be configured to symmetrize a portion of a of the input optical field passed through said aperture while the second synimetrizing unit is configured to symmetrize an output of the first symmetrizing In some embodiments of the the aperture unit and the replication unit are configured such that at least one of the replicas is displaceable with respect to the This can be achieved using a configured and operable to provide such displacement by providing relative displacement of at least one of the aperture unit and the first symmetrizing unit with respect to the second syrometrizing unit The replication unit may be configured with reflective surfaces or may include corner optical In some embodiments of the the reflective surfaces are by at least first and second reflector units accommodated in a relationship along an optical axis of light propagation through the optical arrangement towards an imaging Each of the first and second reflector units may include two reflectors defining mutually perpendicular reflective surfaces such that the reflective surfaces of the first reflector unit are substantially parallel to the respective reflective surfaces of the second reflector As indicated in some embodiments of the the aperture unit may comprise a random The optical arrangement may include or be used with a pixel detector array in an imaging According to another broad aspect of the there is provided a method for use in imaging to provide imaging with a large depth of the method comprising passing an input optical field to be imaged through an aperture and optically processing the optical field passed through the aperture plate to produce a plurality of replicas of said optical field such that said replicas include at least two replicas that are of substantially the same phase distribution and are created at different regions of the aperture BRIEF DESCRIPTION OF THE DRAWINGS To clarify the above and other and features of the present and to further show how it may be carried out in an additionaL at times description of the invention and invention features will be rendered in the below detailed at times with reference to the appended It is appreciated that these when depict only particular embodiments of the are not to be considered limiting of its the invention will continued to be described and explained with additional specificity and detail through the use of the accompanying drawings in 1A and IB show side and rear of an example of the device of the present 1C shows a replicating effect of mirrors positioned near the aperture ID illustrates a mechanism according to which a static device of the invention achieves a high Optical Transfer Function for certain spatial illustrate Optical Transfer Functions achieved by a device of the invention for various degrees of object and show simulated images for various obtained with the invented device and without it for object positioned out of focus and in focus 6 shows a graph of dependence of a width of the point spread function for the invented device on the amount of defocusing of the point the width is defined as three standard deviations of the point spread DETAILED OF EXEMPLARY EMBODIMENTS Referring to 1A and there is schematically illustrated an example of a device 100 configured and operable according to the In 1A a side view of device 100 is The device includes an aperture unit inoluding a random aperture plate 12 within a curtain and includes a replication which in the present example is formed by a first optical unit 16 and a second optical symmetrizing the replication unit is configured to produce a plurality of replicas of an input optical mcluding at least two replicas of substantially the same distribution created at different regions of the aperture In the present this effect is achieved using two symmetrizing in the present the symmetrizing units are formed by reflective It be understood that the invention is not limited to this specific and other replicating units can be such as those including comer array of optical or spatial light modulator First symmetrizing unit 16 includes mirrors 16A and oriented orthogonally to the random plate and to each other and parallel to an optical axis OA of the device an axis of light propagation the aperture plane towards an imaging plane where a detector is Each of the mirrors may be opaque or partially for example Second syrrimetrizing unit 26 includes two mirrors 26A and oriented orthogonally with respect to each an intersection of their planes is parallel to optical axis OA or coincides with each of the mirrors may be opaque or partially for example Units 16 and 26 are aligned with respect to each mirrors 16A and as well as mirrors 16B and are Device 100 may also include a light detector for example a pixel detector positioned in an imaging plane IP of the The imaging plane is relatively compared with the mirrors axial from the aperture plane and the device 100 includes a scanner configured and operable to effectively shift a scanning mcluding random aperture 10 and first symmetrizing unit in the aperture The scanner may be programmed for shifting the scanning head along a desired path and time The scanner may be of a stepper or providing an effect equivalent to that of the mechanical but without mechanical shifting of the In IB a rear view of the aperture plane of device 100 and an effect of the device is Random plate 12 is within the lower left quadrant defined by niirrors 16A and and within the upper right quadrant by mirrors 26A and The random plate passes or diffracts light from an object plane in 1 towards the inside of the towards first symmetrizing second symmetrizing unit and imaging plane The axial length of the mirrors is relatively small when compared to the overall length of the When device 100 is used for imaging of an the aperture plane plane where the random plate element is is illuminated by a phase chirp illustrated in IB by black and gray concentric meaning the phase distribution the part of the chirp being within random plate 12 is The chirp has a quadratic phase distribution and can be quantified by the amount of defocusing First unit 16 effectively adds three replicas of the replicas are either due to light reflected the mirrors or light passed through the mirrors latter is in case of partially transparent mirrors and dependent on projection of a view point on the aperture For a photograph creation of four replicas of a marker cap is shown in Turning back to as a result of replication by unit the optical field is generated which is proportional to where are field mirroring coefficients of rnirrors 16A and and is the product of the chirp wave field with the random plate field transmission Coordinate axes have origin is the global coordinate in the top right corner of the random plate 12 and can move with the random a syinmetrized chirp SC is formed in the upper right quadrant defined by second symmetrizing unit 26 including mirrors 26A and similarly to the first symmetrizing unit second syinmetrizing unit 26 adds to the aperture plane three replicas of the symmetrized chirp SC plane is remote and the axial size of symmetrizing units 16 and 26 is not In ID there is illustrated a mechanism according to which the characteristic MTF mentioned above is The MTF and OTF dependent on of the field distribution in the aperture In the total field at the aperture plane is Fourier transformed when the light O PCT 9 reaches the detector plane and its intensity is captured by the From the Fourier transform the operation of absolute value square over the field point spread function obtained in the detector plane is equivalent to correlation operation performed over the Fourier of the fields in the aperture one needs to the electric field in the aperture It can be mat a field consisting of the symmetrized chirp SC and three replicas substantially overlaps with a replica of this consisting of the symmetrized chirp SC and three replicas when the field and the replica are shifted for a specific distance with respect to each For in replica SC almost coincides with replica It is that phase distributions between these replicas are highly because the black and gray lines within replicas are similarly An electric field generated by the chirp diffracted at the random plate illuminated with the is dependent not only on the phase which due to defocusing is proportional to being the amount of being a coordinate system centered at the optical axis but it is also dependent on field transmission function m of the Thus we can write are exact up to a The random plate is a random field transmission and is its field transmission As explained the is obtained due to the partially transparent mirrors 16 being perpendicular to the random Considering the replicating effect of field mirroring coefficients 26A and the total output may be expressed This transmission function is selected so the main term in its approaches a J y where is defined the desired field transmission functions which autocorrelation functions approach can be provided for various random The inventors have considered that a field transmission function which autocorrelation has a peak with energy between and or between and or between and or between and or between and of the total transmitted is preferred for use in the the OTF is the total field J the overall obtained after using in the expression where the calculated coefficients of delta functions c J The mirroring coefficients must comply with energy conservation This integral can be presented as a product of of the and autocorrelation of the field transmission function m of the aperture in several In the transparency can be taken out of the integral when it is Also other cases when formula can presented as a product of two autocorrelations are In there are shown examples of an OTF obtained by the inventors as a result of applied for their The examples are different in the degree of while for A this degree is for Figs it is The defocusing factor is as high as 50 in all have high peaks at a spatial frequencies of approximately and This magnitude of spatial frequency corresponds to the relative shift between optical axes of the first and second Such a high peak for the selected spatial frequency and such a large range of the defocusing factor for which this peaks exists corresponds to the high energetic efficiency and large depth of focus of the device of the inventiorL the device of the invention can be used for achieving also the super if the detector is used to integrate light intensity while the chirp is As explained moving the random plate to various positions creates an MTF containing peaks at spatial frequencies corresponding to those positions The correspondence through Fourier transform is meant the positions in the aperture plane are proportional to the spatial frequencies in the detector all various spatial frequencies can be The larger the maximum shift from pairs the larger the obtained super resolution factor is in the sense that any high spatial frequency can be transmitted through an appropriately designed random plane and recovered by The operation of a device of the invention has been simulated by the Referring to there the simulation results are The defocusing is measured as the maximal phase obtained at the edges of the It is determined where and dt are the distances the object and the image to the aperture and F is an effective focal length of the imaging device to which it is desired to match the device In there is shown a set of reconstructions of a script image of an image containing In 3A there is presented the result obtained for the device for defocusing In there is shown the image obtained for the same defocusing ψ obtained without applying the shown in 3C and are obtained for the script image positioned in focus using and not using the and correspond to the but for an imaged object being a resolution target or a baby It should be noted that the results presented in are because the scanning was simulated to gather all spatial frequencies detected by the detector with appropriate No image processing was applied to further enhance images in 6 presents the width of three standard deviations of an intensity point spread function obtained in the image plane versus the defocusing It is that even for very strong defocusing of standard deviation remains only 1 and the spatial point spread function is therefore relatively not skilled in the art readily appreciate that various modifications and changes can applied to the embodiments of the invention as hereinbefore described without departing from its scope defined in and by the appended insufficientOCRQuality

Claims (12)

CLAIMS:

1. An optical arrangement for use in imaging with a large depth of focus, said optical arrangement comprising an aperture unit, and a replication unit configured for providing a plurality of replicas of an input optical field such that said replicas include at least two replicas that are of substantially the same phase distribution and are created at different regions of the aperture unit plane.

2. The optical arrangement of Claim 1, wherein said replication unit comprises at least first and second symmetrizing units configured for providing the at least two replicas of the input optical field while sequentially symmetrizing the input optical field projected on said aperture unit with respect to first and second centers of symmetry, respectively.

3. The optical arrangement of Claim 2, wherein said first symmetrizing unit is configured for symmetrizing a portion of a chirp of the input optical field passed through said aperture unit, and said second symmetrizing unit is configured for symmetrizing an output of said first symmetrizing unit

4. The optical arrangement of Claim 2, wherein the aperture unit' and the first and second symmetrizing units are configured such that at least one of the replicas is displaceable with respect to title other.

5. The optical arrangement of Claim 4, comprising a scanner, configured and operable to provide said displacement of at least one of the replicas by providing a relative displacement of at least one of the aperture unit and said first syiTimetiizing unit with respect to the second synmietrizmg unit.

6. The optical arrangement of Claim 1, wherein the replication unit comprises reflective surfaces.

7. The optical arrangement of Claim 1, wherein said reflective surfaces are formed by at least first and second reflector units accommodated in a spaced-apart relationship along an optical axis of light propagation through the optical arrangement towards an imaging plane.

8. The optical arrangement of Claim 7, wherein each of the first and second reflector units comprises two reflectors defining mutually perpendicular refiective surfaces such that the reflective surface of the first reflector unit are substantially parallel to the respective reflective surfaces of the second reflector unit.

9. The optical arrangement of Claim 1, wherein the replication unit comprises at least one of the following: an array of optical fibers, a spatial light modulator, and one or more corner prisms.

10. The arrangement of Claim 1, wherein said aperture unit comprises a random plate.

11. The optical arrangement of Claim 1, comprising a pixel detector array in an imaging plane.

12. A method for use in imaging to provide imaging with a large depth of focus, the method comprising passing an input optical field to be i ged through an aperture plate, and optically processing the optical field passed through the aperture plate to produce a plurality of replicas of said optical field such that said replicas include at least two replicas that are of substantially the same phase distribution and are created at different regions of the aperture plane. For the Applicants RBNHOLD COHN AND PARTNERS