Optical method and system for extended depth of focus

• US 7,061,693 B2
• Filed: 10/28/2004
• Issued: 06/13/2006
• Est. Priority Date: 08/16/2004
• Status: Active Grant

• Current Assignee: Brien Holden Vision Institute
• Original Assignee: Xceed Imaging Ltd.
• Inventors: Zalevsky, Zeev
• Primary Examiner(s): THOMPSON, TIMOTHY J
• Application Number:
  US10/974,943
• Publication Number:
  US 20060034003A1
• Time in Patent Office: 593 Days
• Field of Search: 359/738, 359/739, 359/559, 359/558, 359/721, 359/740, 438/468, 438/535, 438/508
• US Class Current: 359/738
• CPC Class Codes: A61F 2/16 Intraocular lenses
• CPC Class Codes: G02B 2207/129 Coded aperture imaging
• CPC Class Codes: G02B 27/00 Optical systems or apparatus not provided for by any of the groups G02B1/00 - G02B26/00, G02B30/00
• CPC Class Codes: G02B 27/0075 with means for altering, e.g. increasing, the depth of field or depth of focus
• CPC Class Codes: G02B 27/58 Optics for apodization or superresolution; Optical synthetic aperture systems
• CPC Class Codes: G02B 3/08 with discontinuous faces, e.g. Fresnel lens diffractive Fresnel lenses G02B5/1876
• CPC Class Codes: G02B 3/10 Bifocal lenses; Multifocal lenses
• CPC Class Codes: G02C 7/06 bifocal; multifocal ; progressive G02C7/041 takes precedence

Abstract

An imaging arrangement and method for extended the depth of focus are provided. The imaging arrangement comprises an imaging lens having a certain affective aperture, and an optical element associated with said imaging lens. The optical element is configured as a phase-affecting, non-diffractive optical element defining a spatially low frequency phase transition. The optical element and the imaging lens define a predetermined pattern formed by spaced-apart substantially optically transparent features of different optical properties. Position of at least one phase transition region of the optical element within the imaging lens plane is determined by at least a dimension of said affective aperture.

Claims

1. An imaging arrangement comprising:

an imaging lens having a certain affective aperture, and an optical element associated with said imaging lens and configured to provide an extended depth of focus of the imaging arrangement, said optical element being configured as a phase-affecting, non-diffractive optical element defining a spatially low frequency phase transition, said optical element together with the imaging lens defining a predetermined pattern formed by spaced-apart optically transparent features of different optical properties, position of at least one phase transition region of the optical element within the imaging lens plane being determined by at least a dimension of said affective aperture.

2. The arrangement of claim 1, wherein said optical element is configured as a phase-only element.

3. The arrangement of claim 2, wherein said optical element is configured as a binary mask.

4. The arrangement of claim 1, wherein said optical element is a configured as a phase and amplitude affecting element.

5. The arrangement of claim 1, wherein the optical element is configured to maximize a defocused optical transfer function (OTF) of the imaging arrangement by providing the out of focus OTF as much as possible away from zero.

6. The arrangement of claim 5, wherein the optical element is configured to produce proper phase interference relation between light portions passing through different regions of the imaging arrangement corresponding to the different features of the pattern to thereby reduce a quadratic phase factor resulting from light getting out of focus of the imaging lens.

7. The arrangement of claim 1, wherein said at least one transition region is configured as a pi-phase transition for a certain wavelength for which the optical element is designed.

8. The arrangement of claim 1, wherein the position of said at least one transition region with respect to the imaging lens is determined by optical power of the imaging lens.

9. The arrangement of claim 5, wherein the position for N transition regions of the optical element within the imaging lens plane maximizing the OTF is determined as:

$\underset{a_n}{\max }<br><br>\left\{\min <br><br>\left\{\left[\tilde{D}<br><br>\left(v\right)<br><br>\underset{n=1}{\overset{N}{\sum <br><br>}}<br><br>a_n<br><br>\mathrm{rect}<br><br>\left(\frac{v-n<br><br><br><br>\mathrm{\Delta <br><br>}<br><br><br><br>v}{\mathrm{\Delta <br><br>}<br><br><br><br>v}\right)\right]\otimes <br><br>\left[\tilde{D}<br><br>\left(v\right)<br><br>\underset{n=1}{\overset{N}{\sum <br><br>}}<br><br>a_n<br><br>\mathrm{rect}<br><br>\left(\frac{v-n<br><br><br><br>\mathrm{\Delta <br><br>}<br><br><br><br>v}{\mathrm{\Delta <br><br>}<br><br><br><br>v}\right)\right]\right\}\right\}$

values for a_n providing maximum for minima of an expression for auto correlation of a Coherent Transfer Function (CTF) of the imaging lens, where a_n equals either 1 or −

1, {tilde over (D)}(v) being the CTF of the imaging lens corresponding to out of focus position of an object being imaged and being determined as

$\tilde{D}<br><br>\left(v\right)=\exp <br><br>\left(\frac{\mathrm{i<br><br>}<br><br><br><br>4<br><br><br><br>\mathrm{\Psi <br><br>}<br><br><br><br>v^2}{D^2}\right),$

wherein D is the affective aperture dimension, v is a coordinate of the affective aperture in the CTF plane, and ψ

is a phase factor representing a degree of getting out of focus.

10. The arrangement of claim 1, wherein said at least one transition region has a sub-pattern formed by an array of variable phase transition sub-regions.

11. The arrangement of claim 7, wherein said at least one pi-phase transition region has a sub-pattern formed by an array of variable pi-phase transition sub-regions.

12. The arrangement of claim 1, wherein the optical element is configured as at least one annular transition region.

13. The arrangement of claim 1, wherein the optical element is configured as a grid.

14. The arrangement of claim 1, wherein said optical element is spaced-apart from the imaging lens along an optical axis of the imaging lens.

15. The arrangement of claim 1, wherein said optical element is attached to the imaging lens.

16. The arrangement of claim 1, wherein said optical element is made integral with the imaging lens.

17. The arrangement of claim 1, wherein said optical element is configured as a mask formed by an array of said transition regions arranged in a spaced-apart relationship being spaced by the optically transparent regions of the imaging lens within the imaging lens plane.

18. The arrangement of claim 16, wherein said at least one transition region is formed as a surface relief on the imaging lens surface, defining a lens thickness within said at least one region different from that within other regions of the lens.

19. The arrangement of claim 16, wherein said optical element is configured as a mask formed by an array of the phase transition regions arranged in a spaced-apart relationship spaced by the optically transparent regions of the imaging lens.

20. The arrangement of claim 16, wherein said at least one transition region is formed by a material having refractive index different from that of the imaging lens material.

21. The arrangement of claim 16, wherein said optical element is configured as a mask formed by an array of the phase transition regions formed by a material having refractive index different from that of the imaging lens material.

22. The arrangement of claim 5, wherein the optical element is configured to maximize the OTF by reducing high-frequency cancellation at large shifts of a Coherent Transfer Function (CTF) of the imaging lens.

23. The arrangement of claim 5, wherein the optical element is configured to maximize the OTF by reducing sensitivity of the lens arrangement to shifts of a Coherent Transfer Function (CTF) of the imaging lens while getting out of focus.

24. The arrangement of claim 23, wherein the optical element is configured to produce periodic replication of a lateral phase shape of a light field propagating through the imaging lens.

25. The arrangement of claim 23, wherein the optical element is configured in accordance with a free space propagation of the optical element function for a distance between the optical element and the imaging lens plane.

26. An imaging arrangement comprising:

an imaging lens having a certain affective aperture, and an optical element associated with said imaging lens and configured to provide an extended depth of focus of the imaging arrangement, said optical element being configured as a phase-only, non-diffractive binary mask defining a spatially low frequency phase transition, said optical element together with the imaging lens defining a predetermined pattern formed by spaced-apart optically transparent features of different optical properties, position of at least one phase transition region of the optical element within the imaging lens plane being determined by at least a dimension of said affective aperture.

27. An imaging arrangement comprising:

an imaging lens having a certain affective aperture, and an optical element associated with said imaging lens and configured to provide an extended depth of focus of the imaging arrangement, said optical element being configured as a phase-affecting, non-diffractive optical element defining a spatially low frequency phase transition, said optical element together with the imaging lens defining a predetermined pattern formed by spaced-apart optically transparent features of different optical properties, position of at least one phase transition region of the optical element within the imaging lens plane being determined by at least a dimension of said affective aperture such that the optical element produces proper phase interference relation between light portions passing through different regions of the imaging arrangement corresponding to the different features of the pattern to thereby reduce a quadratic phase factor resulting from light getting out of focus of the imaging lens and maximize a defocused optical transfer function (OTF) of the imaging lens arrangement by providing the out of focus OTF as much as possible away from zero.

28. An imaging arrangement comprising an imaging lens having a certain affective aperture, and an optical element associated with said imaging lens and configured to provide an extended depth of focus of the imaging arrangement, said optical element being configured as a phase-affecting, non-diffractive element defining a certain pattern of spatially low frequency phase transitions within a plane of the imaging lens, such that said optical element together with the imaging lens determine a predetermined pattern formed by spaced-apart optically transparent features differently affecting phase of light passing through the imaging arrangement, positions of the phase transitions of the optical element within the imaging lens plane being determined by at least a dimension of said affective aperture to reduce sensitivity of the imaging arrangement to shifts of a Coherent Transfer Function (CTF) of the imaging lens while getting out of focus.

29. An imaging arrangement for creating an image of an object on a detector plane, the system comprising an imaging lens arrangement formed by an imaging lens having a certain affective aperture and an optical element configured to provide an extended depth of focus of the imaging arrangement, said optical element being configured as a phase-affecting, non-diffractive element defining a spatially low frequency phase transition, said optical element together with the imaging lens defining a predetermined pattern formed by spaced-apart optically transparent features of different optical properties, position of at least one phase transition region of the optical element within the imaging lens plane being determined by at least a dimension of said affective aperture such that the optical element produces proper phase interference relation between light portions passing through different regions of the imaging arrangement corresponding to the different features of the pattern to thereby enable reducing a quadratic phase factor resulting from light getting out of focus of the imaging lens and maximize a defocused optical transfer function (OTF) of the imaging arrangement.

30. An optical element for use with an imaging lens for extending depth of focus of imaging, the optical element being configured as a phase-affecting, non-diffractive optical element defining a predetermined pattern of spatially low frequency phase transitions, said pattern being defined by an affective aperture of the given imaging lens.

31. An optical element for use with an imaging lens for extending depth of focus of imaging, the optical element being configured as a phase-only, non-diffractive binary element defining a predetermined pattern of spatially low frequency phase transitions, said pattern being defined by an affective aperture of the given imaging lens.

32. An optical element for extending depth of focus of imaging, the optical element being configured as a phase-affecting, non-diffractive optical element defining a spatially low frequency phase transition, the optical element defining a predetermined pattern of phase transition regions, said transition regions being arranged in accordance with an affective aperture of a given imaging lens for which the optical element is designed, so as to provide said transition regions of the optical element within predetermined positions in the imaging lens plane, to provide periodic replication of a lateral phase shape of a light field propagating through the imaging lens with said optical element.

33. An optical element for extending depth of focus of imaging, the optical element being configured as a phase-only, non-diffractive binary element defining a spatially low frequency phase transition, the optical element defining a predetermined pattern of phase transition regions, said transition regions being arranged in accordance with an affective aperture of a given imaging lens for which the optical element is designed, so as to provide said transition regions of the optical element within predetermined positions in the imaging lens plane, to provide periodic replication of a lateral phase shape of a light field propagating through the imaging lens with said optical element.

34. A method for providing a certain extended depth of focus of an imaging system, the method comprising applying an aperture coding to an imaging lens having a certain effective aperture, by applying to the imaging lens a phase-affecting non-diffractive optical element configured to define a spatially low frequency phase transition arrangement and thereby provide a predetermined pattern of spaced-apart substantially optically transparent features of different optical properties within the imaging lens plane, thereby producing phase interference relation between light portions passing through different regions of the lens arrangement corresponding to the different features of the pattern so as to reduce a quadratic phase factor resulting from light getting out of focus of the imaging lens and maximize a defocused optical transfer function (OTF) of the imaging lens arrangement.

35. A method for providing a certain extended depth of focus of an imaging system, the method comprising designing a phase-affecting non-diffractive optical element to be used with an imaging lens having a certain effective aperture, said designing comprising selecting N positions for phase transitions within the imaging lens effective aperture as those providing maximal contrast of an Optical Transfer Function (OTF) of the imaging system under a set of out of focus locations, thereby providing the out of focus OTF as much as possible away from zero.

36. The method of claim 35, wherein the positions for said N transition regions of the optical element within the imaging lens plane maximizing the OTF are determined as:

$\underset{a_n}{\max }<br><br>\left\{\min <br><br>\left\{\left[\tilde{D}<br><br>\left(v\right)<br><br>\underset{n=1}{\overset{N}{\sum <br><br>}}<br><br>a_n<br><br>\mathrm{rect}<br><br>\left(\frac{v-n<br><br><br><br>\mathrm{\Delta <br><br>}<br><br><br><br>v}{\mathrm{\Delta <br><br>}<br><br><br><br>v}\right)\right]\otimes <br><br>\left[\tilde{D}<br><br>\left(v\right)<br><br>\underset{n=1}{\overset{N}{\sum <br><br>}}<br><br>a_n<br><br>\mathrm{rect}<br><br>\left(\frac{v-n<br><br><br><br>\mathrm{\Delta <br><br>}<br><br><br><br>v}{\mathrm{\Delta <br><br>}<br><br><br><br>v}\right)\right]\right\}\right\}$

values for a_n providing maximum for minima of an expression for auto correlation of a Coherent Transfer Function (CTF) of the imaging lens, where a_n equals either 1 or −

1, {tilde over (D)}(v) being the CTF of the imaging lens corresponding to out of focus position of an object being imaged and being determined as

$\tilde{D}<br><br>\left(v\right)=\exp <br><br>\left(\frac{\mathrm{i<br><br>}<br><br><br><br>4<br><br><br><br>\mathrm{\Psi <br><br>}<br><br><br><br>v^2}{D^2}\right),$

wherein D is the affective aperture dimension, v is a coordinate of the affective aperture in the CTF plane, and, and ψ

is a phase factor representing a degree of getting out of focus.

37. The method of claim 35, comprising fabricating a mask formed by an arrangement of the N transitions spaced-apart from each other in accordance with said selected N positions.

38. The method of claim 37, comprising attaching said mask to the surface of the imaging lens aperture.

39. The method of claim 35, comprising patterning the surface of the imaging lens aperture to form a mask of the N transitions spaced-apart from each other in accordance with said selected N positions.

40. The method of claim 38, comprising providing said surface substantially flat to thereby allow insertion of the patterned imaging lens into a patient'"'"'s eye.

41. The method of claim 39, comprising providing said surface substantially flat to thereby allow insertion of the patterned imaging lens into a patient'"'"'s eye.

42. The method of claim 35, wherein the designing of the optical element comprises producing a phase interference relation between light portions passing through said N regions and spaces between them to thereby reduce a quadratic phase factor resulting from light getting out of focus of the imaging lens and maximize a defocused optical transfer function (OTF) of an arrangement formed by the imaging lens and the optical element.

43. The method of claim 39, wherein said patterning comprises applying material removal to the lens regions within said N positions, and filling said regions, from which the lens material has been removed, by a material of a refraction index different from that of the lens, so as to provide a refraction index difference such that the outer region of the patterned lens is flat and proper equalization between the different material regions is provided to produce a phase interference relation between light portions passing through different material regions to thereby reduce a quadratic phase factor resulting from light getting out of focus of the imaging lens and maximize a defocused optical transfer function (OTF) of the patterned imaging lens.

44. The method of claim 39, wherein said patterning comprises applying diffusion or photo polymerization to the lens regions within said N positions, so as to provide a refraction index difference between said N regions and spaces between them such that the outer region of the patterned lens is flat and proper equalization between the different material regions is provided to produce a phase interference relation between light portions passing through different material regions to thereby reduce a quadratic phase factor resulting from light getting out of focus of the imaging lens and maximize a defocused optical transfer function (OTF) of the patterned imaging lens.

45. The method of claim 35, comprising implanting in the patient'"'"'s eye tissue, within said selected M positions, an artificial tissue having a refraction index different from that of the eye tissue.