GB2396434A - Focussing element with distorted diffraction grating - Google Patents
Focussing element with distorted diffraction grating Download PDFInfo
- Publication number
- GB2396434A GB2396434A GB0229290A GB0229290A GB2396434A GB 2396434 A GB2396434 A GB 2396434A GB 0229290 A GB0229290 A GB 0229290A GB 0229290 A GB0229290 A GB 0229290A GB 2396434 A GB2396434 A GB 2396434A
- Authority
- GB
- United Kingdom
- Prior art keywords
- element according
- grating
- focussing element
- focussing
- radiation
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Withdrawn
Links
- 230000005855 radiation Effects 0.000 claims abstract description 16
- 238000005530 etching Methods 0.000 claims abstract description 6
- 238000003384 imaging method Methods 0.000 claims abstract description 5
- 238000004049 embossing Methods 0.000 claims abstract description 4
- 238000012887 quadratic function Methods 0.000 claims abstract description 4
- 238000000465 moulding Methods 0.000 claims abstract description 3
- 230000003287 optical effect Effects 0.000 claims description 8
- 239000000463 material Substances 0.000 claims description 6
- 238000004519 manufacturing process Methods 0.000 claims description 5
- 239000000758 substrate Substances 0.000 claims description 3
- 239000006185 dispersion Substances 0.000 claims description 2
- 239000000203 mixture Substances 0.000 claims description 2
- 239000011521 glass Substances 0.000 description 4
- 238000000034 method Methods 0.000 description 3
- 239000011248 coating agent Substances 0.000 description 2
- 238000000576 coating method Methods 0.000 description 2
- 239000002131 composite material Substances 0.000 description 2
- 150000001875 compounds Chemical class 0.000 description 2
- 238000000151 deposition Methods 0.000 description 2
- 230000008021 deposition Effects 0.000 description 2
- 238000007493 shaping process Methods 0.000 description 2
- UKUVVAMSXXBMRX-UHFFFAOYSA-N 2,4,5-trithia-1,3-diarsabicyclo[1.1.1]pentane Chemical compound S1[As]2S[As]1S2 UKUVVAMSXXBMRX-UHFFFAOYSA-N 0.000 description 1
- 230000004075 alteration Effects 0.000 description 1
- 229910052785 arsenic Inorganic materials 0.000 description 1
- 239000005387 chalcogenide glass Substances 0.000 description 1
- 238000009826 distribution Methods 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- 230000007613 environmental effect Effects 0.000 description 1
- 238000001704 evaporation Methods 0.000 description 1
- 230000008020 evaporation Effects 0.000 description 1
- 230000002452 interceptive effect Effects 0.000 description 1
- 239000005304 optical glass Substances 0.000 description 1
- 229920002120 photoresistant polymer Polymers 0.000 description 1
- 238000001552 radio frequency sputter deposition Methods 0.000 description 1
- 230000035939 shock Effects 0.000 description 1
- 238000000935 solvent evaporation Methods 0.000 description 1
- 238000004528 spin coating Methods 0.000 description 1
Classifications
-
- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B27/00—Optical systems or apparatus not provided for by any of the groups G02B1/00 - G02B26/00, G02B30/00
- G02B27/42—Diffraction optics, i.e. systems including a diffractive element being designed for providing a diffractive effect
- G02B27/4205—Diffraction optics, i.e. systems including a diffractive element being designed for providing a diffractive effect having a diffractive optical element [DOE] contributing to image formation, e.g. whereby modulation transfer function MTF or optical aberrations are relevant
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01J—MEASUREMENT OF INTENSITY, VELOCITY, SPECTRAL CONTENT, POLARISATION, PHASE OR PULSE CHARACTERISTICS OF INFRARED, VISIBLE OR ULTRAVIOLET LIGHT; COLORIMETRY; RADIATION PYROMETRY
- G01J9/00—Measuring optical phase difference; Determining degree of coherence; Measuring optical wavelength
Abstract
At least one surface of a reflective or transmissive radiation focussing element is provided with at least one phase or amplitude diffraction grating that is distorted substantially according to a quadratic function. The surface or the opposed surface may also be provided with an aperture. The element is useful in three dimensional imaging and wavefront sensing systems. The element may be formed by embossing, selective etching or moulding.
Description
Radiation Focussing Element The present invention relates to a radiation
focussing element.
International Patent Application No. WO/46768 (Secretary of State for Defence) 5 describes an imaging system which includes a diffraction grating which is distorted substantially according to a quadratic function to cause images to be formed under varying focus conditions. Our copending UK Patent Application No. 0205240.5 relates to a system for determining data relating to the local shape (or local phase distribution) of a radiation wavefront, and certain embodiments of that apparatus 10 comprise such a distorted diffraction grating.
Although particularly described in the context of optical radiation, these systems may be used with other forms of radiation.
Both of these patent applications show apparatus in which the distorted grating is located adjacent to a lens.
5 In a first aspect the present invention provides a radiation focussing element at least one surface of which is provided with at least one diffraction grating which is distorted substantially according to a quadratic function. Preferably the focussing element is or comprises a dens which is transmissive to the radiation (a dioptric element), for example a lens of glass, or a glassy material, although it could also be 20 (for example) of a polymeric material; alternatively the focussing element is or comprises a focussing reflector (a catoptric element).
In a preferred embodiment of the invention a single grating is disposed on only one surface of the focussing element. However, according to requirements, different gratings may be disposed on different areas of the same surface of the focussing 25 element, and/or (when the focussing element is a transmissive lens) a similar or different grating or gratings may be disposed on the opposed lens external surface.
In one embodiment the grating is a phase grating. It may be formed in the surface of the bulk (reflective or transmissive) element itself, for example by embossing or selective etching of the formed element, or by suitably moulding or otherwise shaping the element during manufacture.
5 Alternatively the grating may be formed in a layer covering at least part of the surface of the element, for example a layer made of a polymeric material or a glassy composition in which the grating is embossed or selectively etched.
Our copending UK Patent Application No. 0123744.5 describes and claims a method of providing an optical substrate with a surface having a desired shape, the method 10 comprising the steps of coating the surface with a thin layer of an optical glass, and subsequently modifying the shape of the external surface of the layer. As disclosed therein, the shaping of the glass layer may be imparted by etching or embossing. The glass layer may be of a chalcogenide glass, for example a glass consisting of Ge, As, Se and Te, which is rich in Te, or amorphous arsenic trisulphide. It may be deposited 15 by RF sputtering, flash evaporation, solvent evaporation or spin coating.
Furthermore, alternative processes may be utilised to form the grating, for example by coating of the surface of the focussing element with a photoresist, followed by exposure to interfering light beams, development of the resist pattern, and selective etching prior to removal of the remaining resist. In some cases, the developed resist 2 0 pattern may itself provide the grating without the need for etching.
Where the focussing element is a transparent dens a layer in which the grating is formed should be transmissive. Where the focussing element is reflective, the layer could again be transmissive; alternatively the grating could be formed in a reflective layer on a suitably shaped substrate so that the layer provides both the focussing and 2 5 grating functions.
In a development of the invention, e.g. where the size of the beam is important, an amplitude mask is located on at least one surface of the focussing element to provide an aperture. Thus in our copending UK Patent Application No. 0205240.5 mentioned above, the focussing and diffractive elements are located closely adjacent an aperture.
Such a mask could be provided in an additional layer of radiation (light) obscuring material on the said surface, either by selective deposition or selective removal, for example. Thus, whether the grating is a phase grating or an amplitude grating, it could be provided by a suitably shaped layer on the surface of the focussing element.
5 In another embodiment of the invention, the, each, or at least one of the phase gratings described above in relation to the invention is replaced by an amplitude grating. Again, this could be provided in an additional layer of radiation (light) obscuring material on a surface of the focussing element, either by selective deposition or selective removal, for example. Where the aperture mask is also 10 present, the grating and mask may be deposited sequentially or simultaneously, and they may be on the same surface or opposed surfaces of the focussing element.
The invention extends to a three-dimensional imaging system or a wavefront sensor comprising an optical element according to the first aspect of the invention.
The systems described in the aforementioned International Patent Application No. 15 WO/46768 and UK Patent Application No. 0205240.5 are prone to chromatic aberration due to the dispersive properties of the grating, and this has been a limiting factor when attempting to apply the technology with broadband or white light.
Accordingly in a preferred embodiment of lens focussing element, the dispersion inherent in the grating is reduced, and more preferably substantially compensated for, 2 0 by the lens itself, or one or more refractive element(s) thereof if it is a compound or composite lens. This enables the compound element to be used in a white light wavefront sensor or imaging system, for example in systems of the type described and claimed in our aforesaid patent applications.
By forming the grating on the surface of the focussing element, a composite optical 2 5 element is formed which performs both the grating and focussing functions but which is not prone to misalignment problems between the focussing element and the grating due to shocks or other environmental factors. This advantage is compounded if an aperture is also required and it is also provided on the focussing element itself.
Claims (23)
1. A radiation focussing element at least one surface of which is provided with at least one diffraction grating that is distorted substantially according to a quadratic function. 5
2. A focussing element according to claim I wherein the focussing element comprises a radiation reflector providing said surface.
3. A focussing element according to claim 1 wherein the focussing element comprises a radiation transmissive lens providing said surface.
4. A focussing element according to claim 3 wherein only one surface of the lens 10 is provided with a said grating.
5. A focussing element according to claim 3 or claim 4 wherein the dispersion inherent in the grating is reduced by the lens itself, or by one or more refractive element(s) thereof.
6. A focussing element according to any preceding claim wherein the grating is a 15 phase grating.
7. A focussing element according to any one of claims] to 5 wherein the grating is an amplitude grating.
8. A focussing element according to any one of claims I to 7 wherein the grating is provided in a layer covering at least part of said surface.
20
9. A focussing element according to claim 8 wherein said layer is made of a glassy composition.
10. A focussing element according to claim 7 and claim 8 wherein said layer is made of a radiation obscuring material.
11. A focussing element according to any one of claims 8 to 10 wherein said layer 2 5 is shaped.
r (
12. A focussing element according to claim 2 wherein the reflector comprises a reflective layer on a substrate, and said reflective layer is shaped to provide said grating.
13. A focussing element according to any one of claims 1 to 6 wherein the grating 5 is provided in the surface of the bulk element itself.
14. A focussing element according to any preceding claim and further comprising a mask on at least one surface of the element to provide an aperture.
15. A focussing element according to claim 14 wherein a said mask is provided in a layer on a surface of the focussing element.
10
16. A focussing element according to claim 14 or claim 15 wherein said mask and said grating are provided on the same surface of the focussing element.
17. A transmissive focussing element according to claim 14 or claim 15 wherein said mask and said grating are provided on the opposed surfaces of the focussing element. 15
18. A radiation focussing element according to any preceding claim for use with optical radiation.
19. A method of making an element according to any one of claims 11 to 13 wherein the grating is formed by embossing.
20. A method of making an optical element according to claim 11 or claim 12 2 0 wherein the grating is formed by selective etching.
21. A method of making an optical element according to claim 6 wherein the focussing element is a transmissive lens and the grating is formed by moulding during manufacture of the lens.
22. A three-dimensional imaging system comprising an element according to any 25 one of claims 1 to 16.
f
23. A wavefront sensor comprising an optical element according to any one of claims 1 to 16.
Priority Applications (6)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB0229290A GB2396434A (en) | 2002-12-17 | 2002-12-17 | Focussing element with distorted diffraction grating |
| EP03786116A EP1573370A1 (en) | 2002-12-17 | 2003-12-12 | Radiation focussing element |
| US10/539,085 US20060103943A1 (en) | 2002-12-17 | 2003-12-12 | Radiation focussing element |
| JP2004559900A JP2006510049A (en) | 2002-12-17 | 2003-12-12 | Radiation focusing element |
| PCT/GB2003/005463 WO2004055557A1 (en) | 2002-12-17 | 2003-12-12 | Radiation focussing element |
| AU2003295115A AU2003295115A1 (en) | 2002-12-17 | 2003-12-12 | Radiation focussing element |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB0229290A GB2396434A (en) | 2002-12-17 | 2002-12-17 | Focussing element with distorted diffraction grating |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| GB0229290D0 GB0229290D0 (en) | 2003-01-22 |
| GB2396434A true GB2396434A (en) | 2004-06-23 |
Family
ID=9949773
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| GB0229290A Withdrawn GB2396434A (en) | 2002-12-17 | 2002-12-17 | Focussing element with distorted diffraction grating |
Country Status (6)
| Country | Link |
|---|---|
| US (1) | US20060103943A1 (en) |
| EP (1) | EP1573370A1 (en) |
| JP (1) | JP2006510049A (en) |
| AU (1) | AU2003295115A1 (en) |
| GB (1) | GB2396434A (en) |
| WO (1) | WO2004055557A1 (en) |
Citations (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4255514A (en) * | 1979-04-27 | 1981-03-10 | Rca Corporation | Method for fabricating a diffractive subtractive filter embossing master |
| US5323267A (en) * | 1991-12-23 | 1994-06-21 | Gentec Inc. | High power laser beam sampler |
| US5597613A (en) * | 1994-12-30 | 1997-01-28 | Honeywell Inc. | Scale-up process for replicating large area diffractive optical elements |
| US5929991A (en) * | 1997-03-07 | 1999-07-27 | Litel Instruments | Single plate corrector for stepper lens train |
| WO1999046768A1 (en) * | 1998-03-10 | 1999-09-16 | The Secretary Of State For Defence | Three-dimensional imaging system |
Family Cites Families (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5838496A (en) * | 1995-08-28 | 1998-11-17 | Asahi Kogaku Kogyo Kabushiki Kaisha | Diffractive multi-focal objective lens |
| AU2001281742A1 (en) * | 2000-07-21 | 2002-02-05 | Vir A/S | Coupling elements for surface plasmon resonance sensors |
| US6540358B2 (en) * | 2000-10-20 | 2003-04-01 | Kestrel Corporation | Wavefront characterization of corneas |
| US6753118B2 (en) * | 2002-03-27 | 2004-06-22 | Fitel Usa Corp. | Optical grating fabrication process |
-
2002
- 2002-12-17 GB GB0229290A patent/GB2396434A/en not_active Withdrawn
-
2003
- 2003-12-12 WO PCT/GB2003/005463 patent/WO2004055557A1/en not_active Application Discontinuation
- 2003-12-12 AU AU2003295115A patent/AU2003295115A1/en not_active Abandoned
- 2003-12-12 JP JP2004559900A patent/JP2006510049A/en active Pending
- 2003-12-12 US US10/539,085 patent/US20060103943A1/en not_active Abandoned
- 2003-12-12 EP EP03786116A patent/EP1573370A1/en not_active Withdrawn
Patent Citations (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4255514A (en) * | 1979-04-27 | 1981-03-10 | Rca Corporation | Method for fabricating a diffractive subtractive filter embossing master |
| US5323267A (en) * | 1991-12-23 | 1994-06-21 | Gentec Inc. | High power laser beam sampler |
| US5597613A (en) * | 1994-12-30 | 1997-01-28 | Honeywell Inc. | Scale-up process for replicating large area diffractive optical elements |
| US5929991A (en) * | 1997-03-07 | 1999-07-27 | Litel Instruments | Single plate corrector for stepper lens train |
| WO1999046768A1 (en) * | 1998-03-10 | 1999-09-16 | The Secretary Of State For Defence | Three-dimensional imaging system |
Non-Patent Citations (1)
| Title |
|---|
| Applied Optics 38(32) 10 November 1999, 6692-6699 * |
Also Published As
| Publication number | Publication date |
|---|---|
| US20060103943A1 (en) | 2006-05-18 |
| JP2006510049A (en) | 2006-03-23 |
| AU2003295115A1 (en) | 2004-07-09 |
| WO2004055557A1 (en) | 2004-07-01 |
| EP1573370A1 (en) | 2005-09-14 |
| GB0229290D0 (en) | 2003-01-22 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| WAP | Application withdrawn, taken to be withdrawn or refused ** after publication under section 16(1) |