SPIE Reviews

Extended depth of focus imaging: a review

[+] Author Affiliations
Zeev Zalevsky

Bar-Ilan University, School of Engineering, Ramat-Gan, 52900, Israelzalevsz@eng.biu.ac.il

SPIE Reviews. 1, 018001 (January 14, 2010). doi:10.1117/6.0000001
History: Received April 24, 2009; Revised September 05, 2009; Accepted September 07, 2009; Published January 14, 2010
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We review approaches for extending the depth of focus of different imaging systems including the human vision system. Approaches involving digital postprocessing as well as different types of all-optical techniques are discussed.

Figures in this Article

Optical imaging systems are capable of high lateral resolution only in an axial range called either the depth of focus or the depth of field, depending on whether it is measured in image space or object space, respectively. From a wave optics perspective, limited depth of focus arises because defocusing introduces an additional quadratic phase in the system pupil function, resulting in a spatial low-pass filter effect. This effect can be described mathematically by means of the optical transfer function (OTF) of the system,H(μx,μy). The OTF of a single-lens imaging system can be expressed as a properly scaled autocorrelation of the lens pupil functionP(x,y)1:Display Formula

1H(μx,μy)=--P(x+λZiμx2,y+λZiμy2)P*(x-λZiμx2,y-λZiμy2)dxdy--|P(x,y)|2dxdy,
where λ is the optical wavelength, μx, μy are the spatial frequencies, andZi is the distance from the lens to the image plane. For a circular aperture and in the absence of aberrations,P(x,y) is given by the binary circle pupil function, which equals 1 within the pupil and 0 outside. In this case the OTF can be written simply asDisplay Formula
2H(μx,μy)=Area of overlapTotal area=A(μx,μy)dxdyA(0,0)dxdy,
whereA(μx,μy) gives the area of overlap between two shifted pupils andA(0,0) the total area of the pupil. When aberrations are introduced, the generalized pupil function takes the formDisplay Formula
3P(x,y)=|P(x,y)|exp[ikW(x,y)],
whereW(x,y) is the wave aberration function andk = 2π/λ. In the case of defocus,W(x,y) has the quadratic formDisplay Formula
4W(x,y)=Wm(x2+y2)b2,
whereb is the radius of the aperture. The coefficientWm, which determines the severity of the defocusing error, is given byDisplay Formula
5Wm=Ψλ2π,
where ψ is defined byDisplay Formula
6Ψ=πb2λ(1Zi+1Zo-1f),
whereZo is the distance from the object to the lens andf is the focal length of the lens. When the imaging condition is fulfilled,Display Formula
71Zi+1Zo=1f,
and the distortion factor ψ equals zero. When the imaging condition is not fulfilled, the quadratic phase factor of Eqs. (3) and (4) leads to a narrower OTF distribution, i.e., to a low-pass effect or suppression of higher spatial frequency content. For the 1-D case Eq. (1) becomes:Display Formula
8H(μ,Wm)=-P(x+λZiμ2)P*(x-λZiμ2)dx-|P(x)|2dx=A(μ)exp[ikWm2λZiμxb2]dx2b,
whereA(μ) is the 1-D overlap between two shifted pupil functions. Evaluating Eq. (8) gives the 1-D OTF:Display Formula
9H(μ)=(1-|μ|2μc.o.)sinc{8Wmπλ(μ2μc.o.)(1-μ2μc.o.)},
whereμc.o.=bλZi. This expression forH(μ) can be approximated byDisplay Formula
10H(μ)A(0)exp[ikWm2λZiμxb2]dx2b=-bbexp[4πiWmZiμxb2]dx2b=12b·-rect(x2b)exp[4πiWmZiμxb2]dx=sinc(4WmπμZib).
The approximation is valid for values of μ that are not too large in comparison tobZi, such thatA(μ) can be approximated byA(0), the area of the lens. This approximation is also valid for large values ofWm, causing the argument of the exponent to oscillate rapidly. The expression of Eq. (10) demonstrates the spectral low-pass filtering effect.

In the case of a 2-D circular aperture, the resulting OTF, which has only radial frequency dependence, is derived in Ref.2, where it was represented as a serial expansion inJn, i.e.,nth-order Bessel functions of the first type.

If one wishes to estimate the depth of focus it is easily shown to be approximately proportional to the product of the wavelength λ and the square of the f number (the ratio between the focal length and the diameter of the imaging lens), i.e., λ(f/2b)2. The reason is easily seen from Fig.1: Since the diffraction-determined resolution limitation is proportional to λ(f/2b) (the dimensions of the point spread function) and the geometrical angle at which the optical rays diverge is (2b)/f, one obtains that the defocused spot, which equals the depth of focus range multiplied by the angle (2b)/f, should be proportional to λ(f/2b). From this relation the conclusion is indeed that the depth of focus range is proportional to λ(f /2b)2.

Grahic Jump LocationF1 :

Schematic description of the depth of field range.

Following the development of photography, various methods were investigated for overcoming the defocusing limitation described in Section1. The simplest method is simply to reduce the aperture of the imaging lens. The reduction may be gradual, as in aperture apodization, or abrupt, through the addition of a binary blocking/transmitting mask in the aperture plane34. Unfortunately smaller apertures reduce system resolution [making the OTF of Eq. (1) narrower] and also reduce the amount of light reaching the image plane. Other approaches were therefore developed. One solution relies on the addition of refractive elements in the aperture of the imaging system. One of the most popular elements is the axicon56. The operational principle of this element is illustrated in Fig.2. In the region of overlap of the beams being diverted by the axicon, denoted by dashed lines in the figure, an extended depth of focus (EDOF) region is obtained. For comparison, the dashed blue lines show the original ray tracing in the absence of the axicon.

Grahic Jump LocationF2 :

Axicon operation for extending the depth of field.

Another type of refractive element-based solution involves the multiplexing of several lenses, each having a different focal length. An example of spatial multiplexing is that exploited in “progressive” or multifocal spectacles (e.g., bifocal7 or multifocal lenses89). In these lenses the two (or more) focal lengths are spatially separated and allow the required in-focus performance only over a small portion of the field of view. The different lenses divide the plane of the lens aperture and thus, since every lens covers only a limited portion of the aperture, the system has a larger effective f number and thus reduced resolution. On the other hand, if the application is spectacles, then such a solution limits the visual field, since in order to choose the focal length allowing focusing to the desired distance one needs to choose the proper line of sight.

A different way of multiplexing several lenses is by code multiplexing. In this method the multiplexed lenses having different focal lengths are divided into very small pieces that are randomly spread over the entire aperture plane. This type of solution usually refers to a plurality of diffractive lenses. Each lens covers the full aperture, and thus the resolution of each lens is not reduced1012. Such code multiplexing can be implemented either by randomly spreading the pieces of the lenses or by periodically spreading each lens over the entire aperture plane. Because of the dense spatial variations in the aperture plane due to the multiplexing of the various pieces of the lenses, a significant portion of the light energy is diverted through diffraction through large angles. The result is reduced energetic efficiency and glare effects. As in all diffraction-based solutions, the system exhibits significant chromatic aberrations, since the focal length of a diffractive lens is wavelength dependent.

Another EDOF technique employs a cubic phase element attached to the imaging lens13. The idea involves what is basically the insertion of aberrations that are much stronger than the defocusing aberrations such that by digital postprocessing a sharp image can be reconstructed. In contrast to the previous approach, this type of solution is not an all-optical approach but rather one that requires digital postprocessing and thus does not fit to ophthalmic, i.e., vision correction, applications. Other interesting aperture coding techniques requiring digital postprocessing are discussed in Refs.1315 and a lens apodization technique in Ref.16. Additional related technologies involve the tailoring of the modulation transfer functions with fractional-order phase plates17 and with logarithmic asphere lenses18.

A different and historically important approach to extended depth of focus involves the configuration of Scheimpflug19, who by reorienting the imaging system provided what in theory can be infinitely extended focal depth. The sketch of Scheimpflug's configuration is shown in Fig.3 and its practical optical realization in Fig.3.

Grahic Jump LocationF3 :

Infinitely in-focus Scheimpflug planes19: (a) notations and (b) practical imaging configuration.

In this configuration the following mathematical condition must be fulfilled:Display Formula

111a+1b=1d(tanB+tanA)=1f.
The lines designated in Fig.3 as Scheimpflug image and object planes are always in focus and thus objects positioned along those planes will always be in focus. The main drawback of this approach is that, as in the case of “progressive” lenses, the visual field is very limited since every axial distance is imaged at a different lateral position.

Recently several new all-optical approaches for extending the depth of focus have been developed. The development of those approaches is very important not only to digital imaging by cameras but also in ophthalmic vision correction. In one approach the depth of focus is extended by the addition of a plurality of diffractive rings20. As previously noted, one disadvantage in using diffractive elements is the accompanying chromatic aberrations. Another approach, which is more of a refractive type and thus exhibits reduced chromatic aberration, incorporates a nonbinary profile consisting of rings that is added on top of the aperture lens in order to generate unbalanced optical path difference across the aperture21.

A different all-optical direction providing an interference-based rather than diffractive/refractive type of solution is suggested in Refs.22 and23. The basic idea is to view the imaging lens as a component in an interferometer. Such an interpretation is possible since in the focal point all the optical rays passing through the aperture add together. By proper addition of an optical phase engraving on top of the imaging lens, desired constructive interference is generated in a “focus channel” while destructive interference is created around it (see Fig. 4). The added profile has no optical power of its own, but must be used in combination with an imaging lens. The optical profile engraving has large spatial features and thus it is not a diffractive type of element. Its etching depth is very small (about 1 μm) and thus it does not add physical path difference as in refractive solutions. Because this approach is more energetically efficient and exhibits reduced chromatic aberrations, it is thus suitable for ophthalmic applications.

Grahic Jump LocationF4 :

Interferometric approach for extending depth of focus.

Another all-optical technique that extends the depth of focus involves the use of a birefringent lens. Recently, a new approach was presented where a birefringent lens was fabricated24 with two focal lengths, one for the ordinary and the other for the extraordinary polarization state. It is a monofocal lens that becomes bifocal due to the birefringence of the material from which it is made. By proper design of the lens the two focal lengths can be chosen such that the focusing range is extended to roughly double the focal depth25. However, the fabrication of such a lens is complicated and expensive. Obviously this operation principle is valid only for the case when the external illumination is nonpolarized, allowing the illuminating energy to be split between the two focal points. A simplified solution includes using a regular monofocal lens and adding a birefringent plate between the lens and the imaging plane26. The addition of the plate generates different optical paths for the two polarizations and thus each one is focused a different distance from the monofocal imaging lens. Assuming that the required difference in the optical paths in free space is Δ and that the birefringent material has ordinary and extraordinary refractive indexes ofno andne, respectively, then the width of the birefringent plate should be:Display Formula

12ΔB=Δ(1-none).
Note that the last equation is valid for normal incidence of the incoming beam and that non-normal incidence angles (mainly corresponding to the edges of the field of view) will not have proper extension in the focal depth.

As previously mentioned, using a pinhole reduces the resolution and the energetic efficiency but significantly increases the depth of focus of a system. Thus, one possible improvement for achieving extension in the focal depth involves the usage of a random pinhole plate instead of an imaging lens2728. In this case the energetic efficiency is increased, since there are many pinholes covering the lens aperture, and the resolution, although reduced, can be recovered by a proper digital inverse filtering operation. A nice feature of such a configuration is that, since the pinhole mask is random, the OTF has a random phase distribution that varies with distance. Therefore, the distance to various objects in the image can be extracted by properly correcting the phase of the OTF. Each phase correction will result in in-focus objects positioned at different axial distances. If digital postprocessing is considered, then the amount of defocusing can be estimated digitally from the image by observing the zeros generated in its Fourier plane2930.

The topic of extended depth of focus is strongly linked to beam shaping, and approaches for this purpose are relevant to this review. Numerical Gerchberg–Saxton-based3132 iterative algorithms33 as well as analytically optimized 3-D point spread function approaches have been demonstrated as useful in properly designing the point spread function. Controlling the 3-D shape of the point spread function can be used for beam shaping as well as for extending the focal depth. The optimization procedure may either be obtained by descriptions based on generalized propagation-invariant wave fields3435 or by 3-D optimization using the calculus of variations3637. The desired beam shaping can also be obtained by proper phase and amplitude apodizing of the aperture of the imaging lens as described in Refs.3842. In Ref.41, for instance, the authors show how to tailor the depth of focus for an optical system using pupil functions obtained by applying the Fourier transformation tool.

The human eye can focus on objects at different axial distances. This capability is called accommodation. The required range of accommodation is approximately 3.00 diopters, allowing focus from about 30 cm out to infinity. After the age of 45 the range of accommodation is noticeably reduced until by age 65 or so no such ability remains and the eye operates like a monofocal lens with fixed focal length. This reduction in accommodation power is called presbyopia. Bifocal and progressive spectacle lenses are designed to shift the direction of gaze and thus severely limit the functional visual field7. Diffractive optics-related solutions for presbyopia in contact lenses have not been able to penetrate the market.

The existing multi-focal-length contact lenses can be divided into the two categories of soft and rigid lenses. With soft contact lenses the operation principle is usually related to refractive rings for only two focal lengths or progressive transition through the radius of the lens43. The most popular lenses are PureVision® made by Bausch and Lomb. These are aspheric lenses with progressive change of the focal length. There are other bifocal spherical lenses made by Johnson & Johnson that are also based on refractive rings. In those bifocal solutions there is always one image in focus (the one corresponding to the object positioned in the relevant distance) and one is defocused. Thus, the brain must “learn” how to suppress the undesired defocused image while reinforcing the relevant in-focus image. This “learning” procedure require adaptation time.

With rigid contact lenses the operation principle is based on the fact that when one reads, the eyes are directed downward and the contact lens can be caught by the eyelid. The person can thus look through the peripheral part of the lens, which is designed to have a different focal length that is suitable for focusing at close ranges. This operation requires considerable practice from the subject. Examples of such types of lenses are Lifestyle and Gelflex. The main problem with these technologies is that they do not function well in low-light environments and have visual artifacts associated with glare and halo.

In cataract surgery the crystalline lens is usually replaced by a fixed monofocal intraocular lenses (IOL). The ophthalmic challenge is thus similar to that encountered in the case of presbyopia. With IOLs one of the most common approaches to extend the depth of focus is by physically reducing the aperture of the lens by means of a hole with reduced radius4447. The problem, of course, is significantly reduced energetic efficiency.

There are also diffractive optics IOLs that are bifocal4850 and that thus allow close- and distance-focused vision, but they exhibit large chromatic aberrations. They function well for green light but in other wavelength bands they lose their multifocal property and function as almost monofocal lenses. Examples of multifocal diffractive lenses are the ReSTOR® lens made by Alcon and the Acri.LISA lens made by Zeiss. There are also refractive lenses, such as the ReZoom® made by AMO51, but these lenses, as well as those based on diffraction, produce a discrete number of focal lengths and thus they provide no solution for the intermediate range, i.e., they allow reading and looking far away but not working at a computer because their depth of focus extension is not continuous as, e.g., in the all-optical solution of Refs.22 and23.

Another type of IOL is in fact accommodative52. In these lenses, the subject can achieve some accommodation after the implantation. There are two types of technological approaches for this category. In the first, a monofocal lens is positioned on an axial pivot such that when the lens is pressed with the muscles of the eye it is axially shifted5354. An example is the Crystalens lens made by Bausch and Lomb. In a variation of this method, a doublet is composed of two monofocal lenses designed in such a way that, when they are pressed by the muscles of the eye, their separation changes and, thus, the overall focal length changes as well55. The second technology includes construction of a lens made of a flexible material whose curvature, and thus its focal length, changes when the lens is pressed by the muscles of the eye56. The problem with these lenses is that they are unable to provide more than 1.00 diopter of accommodation, and even this small amount decreases with time. Also, this type of lens functions differently for different people, since each subject applies different force on the lens.

Another depth-of-focus-related ophthalmic aberration is astigmatism, observed when the eye has different focal lengths for transverse different axes. In regular astigmatism57, the meridians in which the two different curves lie are located 90 deg apart. In irregular astigmatism58, the two meridians may be located at something other than 90 deg apart; or there are more than two meridians. In their medical definitions, regular astigmatism is an astigmatism in which the refractive power of the eye shows a uniform increase or decrease from one meridian to another while an irregular astigmatism is when the curvature varies in different parts of the same meridian or in which refraction in successive meridians differs irregularly.

Irregular astigmatism is a common problem in cases when the astigmatism results from keratoconus or refractive surgery5960. Cylindrical lenses or toric contact lenses provide a solution for regular astigmatism. However, no common solution for irregular astigmatism is currently available. The interferometric-based solution of Refs.22 and23, because it is rotation-invariant, allows regular and irregular astigmatism correction because, due to the extended depth of focus, if the astigmatism is lower than the extension in the focal depth (which in this approach was limited to 3.00 diopter6165), there always will be an axial position where the two focal points (after the extension) will coincide. This operation principle is schematically demonstrated in Fig.5. In this figure one may see a lens with different horizontal and vertical focal lengths. An EDOF technique that is implemented in the lens design generates focal extension around each one of the two focal planes corresponding to each one of the two axes (each having its own focal length). Due to the EDOF there is a plane (marked in the figure) in which the two extensions overlap. For this axial position an image without astigmatic aberration will be formed.

Grahic Jump LocationF5 :

Astigmatic aberration correction via addition of extension in the focal depth. In the figure a lens having an EDOF as well as an astigmatic aberration is presented. The marked plane designates the axial position for which both axes are obtained in focus.

Note that the extension in depth of focus can also be applied for correction of myopia66. This is especially important in the case of children, since children who start using lenses at an early age experience accelerated development of their myopia. The use of the interferometric EDOF solution, having no real optical power, can stop the progress of myopia66.

There are other EDOF techniques for addressing the presbyopia problem by modifying the corneal profile. One important method relates to laser-based refractive surgery6770. One of most popular refractive surgery procedures is laser-assisted in situ keratomileusis (LASIK). During the LASIK procedure, refractive surgeons reshape the cornea by removing precise amounts of corneal tissue to correct the patient's degree of refractive error or presbyopia. Today's custom LASIK procedure incorporates the use of a wavefront map, which provides the LASIK surgeon with a 3-D map of the eye that can be transferred directly to the laser. IntraLASIK is similar to traditional LASIK in the sense that it also involves corneal reshaping. The difference lies in the method used to create the flap during the first part of the procedure. The laser-assisted sub-epithelial keratomileusis (LASEK) procedure is another variation of LASIK. The main difference between LASIK and LASEK takes place when the flap is created. The LASEK procedure allows refractive surgeons to save more corneal tissue, making it an excellent treatment option for patients with thin corneas. Epi-LASIK is another variation of the LASIK procedure. During Epi-LASIK, an epikeratome is used to detach a thin layer of tissue in the epithelium. Once this layer of tissue is moved aside, the refractive surgeon can reshape the cornea as done in the traditional LASIK procedure. When corneal reshaping is complete, the refractive surgeon replaces the epithelial tissue and a special contact lens is introduced to promote healing.

In this paper we reviewed a variety of techniques for extending the depth of focus of imaging systems. This field is important for different types of imaging applications involving digital cameras and those designed to cope with presbyopia and regular/irregular astigmatism aberrations or for stopping the progress of myopia in children.

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Hammond  C. M., “ Apparatus and method for reducing imaging errors in imaging systems having an extended depth of field. ,” U.S. Patent No. 6097856 ((2000)).
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Bellucci  R., “ Multifocal intraocular lenses. ,”Curr. Opin. Ophthalmol.. 16, (1 ),33–37  ((2005)).
Campbell  C. E., “ Wavefront measurements of diffractive and refractive multifocal intraocular lenses in an artificial eye. ,”J. Refract Surg.. 24, (3 ),308–311  ((2008)).
Pieh  S., ,Marvan  P., ,Lackner  B., ,Hanselmayer  G., ,Schmidinger  G., ,Leitgeb  R., ,Sticker  M., ,Hitzenberger  C. K., ,Fercher  A. F., , andSkorpik  C., “ Quantitative performance of bifocal and multifocal intraocular lenses in a model eye: point spread function in multifocal intraocular lenses. ,”Arch. Ophthalmol.. 120, (1 ),23–28  ((2002)).
Artigas  J. M., ,Menezo  J. L., ,Peris  C., ,Felipe  A., , andDiaz-Llopis  M., “ Image quality with multifocal intraocular lenses and the effect of pupil size: comparison of refractive and hybrid refractive-diffractive designs. ,”J. Cataract Refract. Surg.. 33, (12 ),2111–2117  ((2007)).
Dick  H. B., “ Accommodative intraocular lenses: current status. ,”Curr. Opin. Ophthalmol.. 16, (1 ),8–26  ((2005)).
Findl  O., andLeydolt  C., “ Meta-analysis of accommodating intraocular lenses. ,”J. Cataract Refract. Surg.. 33, (3 ),522–527  ((2007)).
Cumming  J. S., “ Performance of the crystalens. ,”J. Refract Surg.. 22, (7 ),633–635  ((2006)).
Rana  A., ,Miller  D., , andMagnante  P., “ Understanding the accommodating intraocular lens. ,”J. Cataract Refract. Surg.. 29, (12 ),2284–2287  ((2003)).
Tonekaboni  K., andWhitsett  A. J., “ The IOL horizon: accommodative intraocular lenses. ,”Optometry. 76, (3 ),185–190  ((2005)).
Grosvenor  T., Primary Care Optometry. ,3rd ed., pp.24–26 , Butterworth-Heinemann , Boston  ((1996)).
Grosvenor  T., Primary Care Optometry. ,3rd ed., pp.355–356 , Butterworth-Heinemann , Boston  ((1996)).
Atwood  J. D., “ Presbyopic contact lenses. ,”Curr. Opin. Ophthalmol.. 11, ,296–298  ((2000)).
Rabinowitz  Y. S., “ Keratoconus. ,”Surv. Ophthalmol.. 42, ,297–319  ((1998)).
Zlotnik  A., ,Ben Yaish  S., ,Yehezkel  O., ,Belkin  M., , andZalevsky  Z., “ Thin films as spectacles and contact lenses for aberration-corrected vision via brain adaptation to contrast. ,”J. Vision. 8, (6 ),263  ((2008)).
Ben Yaish  S., ,Zlotnik  A., ,Yehezkel  O., ,Belkin  M., , andZalevsky  Z., “ Omni-focal refractive correction lens: a potential substitute for bi/multi-focal lenses. ,” inInvest. Ophthalmol. Vis. Sci.. 49, , E-Abstract 1798, ARVO ((2008)).
Raveh  I., ,Yehezkel  O., ,Ben Yaish  S., ,Zlotnik  A., ,Belkin  M., , andZalevsky  Z., “ Intraocular lenses with axially continuous extended depth of focus: a novel design. ,” European Society of Cataract and Refractive Surgery, Berlin ((September 2008)).
Zalevsky  Z., ,Ben Yaish  S., ,Yehezkel  O., , andBelkin  M., “ Thin spectacles for myopia, presbyopia and astigmatism insensitive vision. ,”Opt. Express. 15, ,10790–10803  ((2007)).
Ben Yaish  S., ,Zlotnik  A., ,Raveh  I., ,Yehezkel  O., ,Belkin  M., ,Lahav  K., , andZalevsky  Z., “ Omni-focal refractive focus correction technology as a substitute for bi/multi-focal intraocular lenses, contact lenses, and spectacles. ,”Proc. SPIE. 7163, ,71631M  ((2009)).
Yehezkel  O., ,Ben-Yaish  S., ,Zlotnik  A., ,Belkin  M., , andZalevsky  Z., “ A novel myopia correcting lens which reduces the need for accommodation for near vision tasks. ,”Invest. Ophthalmol. Vis. Sci.. 49, , E-Abstract 1799, ARVO ((2008)).
Pinelli  R., ,Ortiz  D., ,Simonetto  A., ,Bachi  C., ,Sala  E., , andAlió  J. L., “ Correction of presbyopia in hyperopia with a center-distance, paracentral-near technique using the Technolas 217z platform. ,”J. Refract Surg.. 24, ,494–500  ((2008)).
Artola  A., ,Patel  S., ,Schimchak  P., ,Ayala  M. J., ,Ruiz-Moreno  J. M., , andAlió  J. L., “ Evidence for delayed presbyopia after photorefractive keratectomy for myopia. ,”Ophthalmol. ,113, ,735–741  ((2006)).
Alió  J. L., ,Chaubard  J. J., ,Caliz  A., ,Sala  E., , andPatel  S., “ Correction of presbyopia by technovision central multifocal LASIK (presbyLASIK). ,”J. Refract Surg.. 22, ,453–460  ((2006)).
Ortiz  D., ,Alió  J. L., ,Illueca  C., ,Mas  D., ,Sala  E., ,Pérez  J., , andEspinosa  J., “ Optical analysis of presbyLASIK treatment by a light propagation algorithm. ,”J. Refract Surg.. 23, ,39–44  ((2007)).

Grahic Jump LocationImage not available.

Zeev Zalevsky received his BSc and PhD degrees in electrical engineering from Tel-Aviv University in 1993 and 1996, respectively. Zeev is currently an associate professor in the school of engineering in Bar-Ilan University, Israel. His major fields of research are optical super resolution, nanophotonics, in-fiber devices, fiber optics, optical data processing, diffractive optical elements and beam shaping, 3-D estimation, and RF-photonics. Zeev has published two books, more than 10 book chapters, more than 200 refereed papers, and holds about 15 issued patents. In 2007 Zeev received the Kril prize given by the Wolf foundation and in 2008 he was awarded with the International Commission for Optics (ICO) prize for his contribution to the field of optical super resolution. In 2009 he received the Juludan prize for advancing technology in medicine.

© 2010 Society of Photo-Optical Instrumentation Engineers

Citation

Zeev Zalevsky
"Extended depth of focus imaging: a review", SPIE Reviews. 1, 018001 (January 14, 2010). ; http://dx.doi.org/10.1117/6.0000001


Figures

Grahic Jump LocationF1 :

Schematic description of the depth of field range.

Grahic Jump LocationF2 :

Axicon operation for extending the depth of field.

Grahic Jump LocationF3 :

Infinitely in-focus Scheimpflug planes19: (a) notations and (b) practical imaging configuration.

Grahic Jump LocationF4 :

Interferometric approach for extending depth of focus.

Grahic Jump LocationF5 :

Astigmatic aberration correction via addition of extension in the focal depth. In the figure a lens having an EDOF as well as an astigmatic aberration is presented. The marked plane designates the axial position for which both axes are obtained in focus.

Tables

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Martinez-Corral  M., ,Caballero  M., ,Stelzer  Ernst H. K., , andSwoger  Jim, “ Tailoring the axial shape of the point spread function using the Toraldo concept. ,”Opt. Express. 10, ,98–103  ((2002)).
Davis  J. A., ,Tuvey  C. S., ,López-Coronado  O., ,Campos  J., ,Yzuel  M. J., , andIemmi  C., “ Tailoring the depth of focus for optical imaging systems using a Fourier transform approach. ,”Opt. Lett.. 32, ,844–846  ((2007)).
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Hammond  C. M., “ Apparatus and method for reducing imaging errors in imaging systems having an extended depth of field. ,” U.S. Patent No. 6097856 ((2000)).
Christie  B., ,Schweigerling  J., ,Prince  S., , andSilvestrini  T., “ Optical performance of a corneal inlay for presbyopia. ” inInvest. Ophthalmol. Vis. Sci.. 46, , E-Abstract 695, ARVO ((2005)).
Bellucci  R., “ Multifocal intraocular lenses. ,”Curr. Opin. Ophthalmol.. 16, (1 ),33–37  ((2005)).
Campbell  C. E., “ Wavefront measurements of diffractive and refractive multifocal intraocular lenses in an artificial eye. ,”J. Refract Surg.. 24, (3 ),308–311  ((2008)).
Pieh  S., ,Marvan  P., ,Lackner  B., ,Hanselmayer  G., ,Schmidinger  G., ,Leitgeb  R., ,Sticker  M., ,Hitzenberger  C. K., ,Fercher  A. F., , andSkorpik  C., “ Quantitative performance of bifocal and multifocal intraocular lenses in a model eye: point spread function in multifocal intraocular lenses. ,”Arch. Ophthalmol.. 120, (1 ),23–28  ((2002)).
Artigas  J. M., ,Menezo  J. L., ,Peris  C., ,Felipe  A., , andDiaz-Llopis  M., “ Image quality with multifocal intraocular lenses and the effect of pupil size: comparison of refractive and hybrid refractive-diffractive designs. ,”J. Cataract Refract. Surg.. 33, (12 ),2111–2117  ((2007)).
Dick  H. B., “ Accommodative intraocular lenses: current status. ,”Curr. Opin. Ophthalmol.. 16, (1 ),8–26  ((2005)).
Findl  O., andLeydolt  C., “ Meta-analysis of accommodating intraocular lenses. ,”J. Cataract Refract. Surg.. 33, (3 ),522–527  ((2007)).
Cumming  J. S., “ Performance of the crystalens. ,”J. Refract Surg.. 22, (7 ),633–635  ((2006)).
Rana  A., ,Miller  D., , andMagnante  P., “ Understanding the accommodating intraocular lens. ,”J. Cataract Refract. Surg.. 29, (12 ),2284–2287  ((2003)).
Tonekaboni  K., andWhitsett  A. J., “ The IOL horizon: accommodative intraocular lenses. ,”Optometry. 76, (3 ),185–190  ((2005)).
Grosvenor  T., Primary Care Optometry. ,3rd ed., pp.24–26 , Butterworth-Heinemann , Boston  ((1996)).
Grosvenor  T., Primary Care Optometry. ,3rd ed., pp.355–356 , Butterworth-Heinemann , Boston  ((1996)).
Atwood  J. D., “ Presbyopic contact lenses. ,”Curr. Opin. Ophthalmol.. 11, ,296–298  ((2000)).
Rabinowitz  Y. S., “ Keratoconus. ,”Surv. Ophthalmol.. 42, ,297–319  ((1998)).
Zlotnik  A., ,Ben Yaish  S., ,Yehezkel  O., ,Belkin  M., , andZalevsky  Z., “ Thin films as spectacles and contact lenses for aberration-corrected vision via brain adaptation to contrast. ,”J. Vision. 8, (6 ),263  ((2008)).
Ben Yaish  S., ,Zlotnik  A., ,Yehezkel  O., ,Belkin  M., , andZalevsky  Z., “ Omni-focal refractive correction lens: a potential substitute for bi/multi-focal lenses. ,” inInvest. Ophthalmol. Vis. Sci.. 49, , E-Abstract 1798, ARVO ((2008)).
Raveh  I., ,Yehezkel  O., ,Ben Yaish  S., ,Zlotnik  A., ,Belkin  M., , andZalevsky  Z., “ Intraocular lenses with axially continuous extended depth of focus: a novel design. ,” European Society of Cataract and Refractive Surgery, Berlin ((September 2008)).
Zalevsky  Z., ,Ben Yaish  S., ,Yehezkel  O., , andBelkin  M., “ Thin spectacles for myopia, presbyopia and astigmatism insensitive vision. ,”Opt. Express. 15, ,10790–10803  ((2007)).
Ben Yaish  S., ,Zlotnik  A., ,Raveh  I., ,Yehezkel  O., ,Belkin  M., ,Lahav  K., , andZalevsky  Z., “ Omni-focal refractive focus correction technology as a substitute for bi/multi-focal intraocular lenses, contact lenses, and spectacles. ,”Proc. SPIE. 7163, ,71631M  ((2009)).
Yehezkel  O., ,Ben-Yaish  S., ,Zlotnik  A., ,Belkin  M., , andZalevsky  Z., “ A novel myopia correcting lens which reduces the need for accommodation for near vision tasks. ,”Invest. Ophthalmol. Vis. Sci.. 49, , E-Abstract 1799, ARVO ((2008)).
Pinelli  R., ,Ortiz  D., ,Simonetto  A., ,Bachi  C., ,Sala  E., , andAlió  J. L., “ Correction of presbyopia in hyperopia with a center-distance, paracentral-near technique using the Technolas 217z platform. ,”J. Refract Surg.. 24, ,494–500  ((2008)).
Artola  A., ,Patel  S., ,Schimchak  P., ,Ayala  M. J., ,Ruiz-Moreno  J. M., , andAlió  J. L., “ Evidence for delayed presbyopia after photorefractive keratectomy for myopia. ,”Ophthalmol. ,113, ,735–741  ((2006)).
Alió  J. L., ,Chaubard  J. J., ,Caliz  A., ,Sala  E., , andPatel  S., “ Correction of presbyopia by technovision central multifocal LASIK (presbyLASIK). ,”J. Refract Surg.. 22, ,453–460  ((2006)).
Ortiz  D., ,Alió  J. L., ,Illueca  C., ,Mas  D., ,Sala  E., ,Pérez  J., , andEspinosa  J., “ Optical analysis of presbyLASIK treatment by a light propagation algorithm. ,”J. Refract Surg.. 23, ,39–44  ((2007)).

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