WIDEBAND AMBIENT LIGHT REJECTION

• US 20110205421A1
• Filed: 02/22/2011
• Published: 08/25/2011
• Est. Priority Date: 02/23/2010
• Status: Active Grant

• Current Assignee: Apple Inc.
• Original Assignee: PrimeSense Ltd (Apple Inc.)
• Inventors: Bezdin, Haim, Gilboa, Niv, Shpunt, Alexander
• Granted Patent: US 8,786,757 B2
• Time in Patent Office: Days
• US Class Current: 348/336
• CPC Class Codes: G02B 27/0944 Diffractive optical elements, e.g. gratings, holograms gratings per se G02B5/18; holograms used as optical elements per se G02B5/32
• CPC Class Codes: G02B 27/0955 Lenses lenses per se G02B3/00
• CPC Class Codes: G02B 27/1066 for enhancing image performance, like resolution, pixel numbers, dual magnifications or dynamic range, by tiling, slicing or overlapping fields of view
• CPC Class Codes: G02B 27/12 operating by refraction only
• CPC Class Codes: G02B 27/4205 having a diffractive optical element [DOE] contributing to image formation, e.g. whereby modulation transfer function MTF or optical aberrations are relevant
• CPC Class Codes: H04N 13/106 Processing image signals for multi-view video sequence encoding H04N19/597
• CPC Class Codes: H04N 13/257 Colour aspects
• CPC Class Codes: H04N 13/271 wherein the generated image signals comprise depth maps or disparity maps
• CPC Class Codes: H04N 23/11 for generating image signals from visible and infrared light wavelengths
• CPC Class Codes: H04N 23/45 for generating image signals from two or more image sensors being of different type or operating in different modes, e.g. with a CMOS sensor for moving images in combination with a charge-coupled device [CCD] for still images
• CPC Class Codes: H04N 23/75 by influencing optical camera components
• CPC Class Codes: H04N 9/646 for image enhancement, e.g. vertical detail restoration, cross-colour elimination, contour correction, chrominance trapping filters

Abstract

Optical apparatus includes an image sensor and objective optics, which are configured to collect and focus optical radiation over a range of wavelengths along a common optical axis toward a plane of the image sensor. A dispersive element is positioned to spread the optical radiation collected by the objective optics so that different wavelengths in the range are focused along different, respective optical axes toward the plane.

Claims

1. Optical apparatus, comprising:

an image sensor;

objective optics, which are configured to collect and focus optical radiation over a range of wavelengths along a common optical axis toward a plane of the image sensor; and

a dispersive element, which is positioned to spread the optical radiation collected by the objective optics so that different wavelengths in the range are focused along different, respective optical axes toward the plane.

2. The apparatus according to claim 1, wherein the dispersive element is configured to cause the image sensor to capture a sharp image of the optical radiation emitted from an object at a target wavelength within the range, while spreading broadband background radiation within the range across the plane.

3. The apparatus according to claim 2, and comprising a projection assembly, which is configured to project the optical radiation at the target wavelength onto the object, so that the emitted optical radiation collected by the objective comprises the projected optical radiation that is reflected from the object.

4. The apparatus according to claim 3, wherein the projected optical radiation comprises a predetermined radiation pattern, and wherein the sharp image captured by the image sensor comprises an image of the pattern projected onto the object.

5. The apparatus according to claim 2, and comprising a processor, which is configured to process the sharp image captured by the image sensor while rejecting interference caused by the background radiation.

6. The apparatus according to claim 5, wherein the processor is configured to construct a 3D map of the object by processing the sharp image.

7. The apparatus according to claim 1, wherein the dispersive element comprises a diffractive element.

8. The apparatus according to claim 7, wherein the diffractive element comprises a grating.

9. The apparatus according to claim 8, wherein the grating is configured to direct a selected diffraction order onto the image sensor, and wherein the apparatus comprises an interference filter positioned between the grating and the image sensor so as to block stray diffraction orders, other than the selected diffraction order, from reaching the image sensor.

10. The apparatus according to claim 1, wherein the dispersive element comprises a refractive element.

11. The apparatus according to claim 1, wherein the dispersive element is configured so that the optical radiation is focused with a chromatic aberration in excess of one micrometer per nanometer of wavelength at the plane of the image sensor.

12. The apparatus according to claim 1, wherein the dispersive element has a first tilt relative to the optical axis, and wherein the apparatus comprises a wedged lens, which is configured to focus the optical radiation with a second tilt, opposite to the first tilt.

13. The apparatus according to claim 12, wherein the wedged lens comprises a section of an axially-symmetrical lens.

14. Optical apparatus, comprising:

a projection assembly, which is configured to project optical radiation at a target wavelength onto an object;

an imaging assembly, comprising;

an image sensor; and

optics, which are configured to collect and focus the optical radiation reflected from the object, along with background radiation over a range of wavelengths, toward a plane of the image sensor, and which comprise a dispersive element, which is configured to direct the collected optical radiation so as to form a sharp image of the optical radiation at the target wavelength in the plane of the image sensor, while spreading the background radiation across the plane; and

a processor, which is configured to process the sharp image captured by the image sensor while rejecting interference caused by the background radiation.

15. The apparatus according to claim 14, wherein the projected optical radiation comprises a predetermined radiation pattern, and

wherein the sharp image captured by the image sensor comprises an image of the pattern projected onto the object, and

wherein the processor is configured to construct a 3D map of the object by processing the sharp image.

16. The apparatus according to claim 14, wherein the dispersive element is configured to spread the optical radiation collected by the optics so that different wavelengths in the range are focused along different, respective optical axes toward the plane of the image sensor.

17. The apparatus according to claim 14, wherein the dispersive element comprises a dispersive focusing element, which is configured to focus the radiation at the target wavelength onto the plane of the image sensor, while other wavelengths in the range are focused ahead of or behind the plane.

18. The apparatus according to claim 17, wherein the dispersive focusing element comprises a diffractive lens.

19. The apparatus according to claim 14, wherein the dispersive element is configured so that the optics have a chromatic aberration in excess of one micrometer per nanometer of wavelength at the plane of the image sensor.

20. The apparatus according to claim 14, and comprising a motion mechanism, which is configured to shift a position of one or more elements of the optics relative to the plane so as to select the target wavelength that is to be imaged sharply in the plane.

21. Optical apparatus, comprising:

an image sensor; and

objective optics, which are configured to collect and focus optical radiation over a range of wavelengths toward a plane of the image sensor, and which comprise a dispersive element configured so that the optics have a chromatic aberration in excess of one micrometer per nanometer of wavelength at the plane.

22. The apparatus according to claim 21, wherein the optics are configured so that the chromatic aberration causes different wavelengths in the range originating from a given object point to focus at different, respective image points along an axis perpendicular to the plane.

23. The apparatus according to claim 21, wherein the optics are configured so that the chromatic aberration causes different wavelengths in the range originating from a given object point to focus along different, respective axes.

24. A method for imaging, comprising:

collecting and focusing optical radiation over a range of wavelengths along a common optical axis toward a plane of an image sensor; and

positioning a dispersive element to spread the collected optical radiation so that different wavelengths in the range are focused along different, respective optical axes toward the plane.

25. The method according to claim 24, wherein positioning the dispersive element causes the image sensor to capture a sharp image of the optical radiation emitted from an object at a target wavelength within the range, while spreading broadband background radiation within the range across the plane.

26. The method according to claim 25, and comprising projecting the optical radiation at the target wavelength onto the object, so that the optical radiation emitted from the object comprises the projected optical radiation that is reflected from the object.

27. The method according to claim 26, wherein the projected optical radiation comprises a predetermined radiation pattern, and wherein the sharp image captured by the image sensor comprises an image of the pattern projected onto the object.

28. The method according to claim 25, and comprising processing the sharp image captured by the image sensor while rejecting interference caused by the background radiation.

29. The method according to claim 28, wherein processing the sharp image comprises constructing a 3D map of the object by processing the sharp image.

30. The method according to claim 24, wherein the dispersive element comprises a diffractive element.

31. The method according to claim 30, wherein the diffractive element comprises a grating.

32. The method according to claim 31, wherein positioning the dispersive element comprises configuring the grating to direct a selected diffraction order onto the image sensor, and wherein the method comprises positioning an interference filter between the grating and the image sensor so as to block stray diffraction orders, other than the selected diffraction order, from reaching the image sensor.

33. The method according to claim 24, wherein the dispersive element comprises a refractive element.

34. The method according to claim 24, wherein the dispersive element is configured so that the optical radiation is focused with a chromatic aberration in excess of one micrometer per nanometer of wavelength at the plane of the image sensor.

35. The method according to claim 24, wherein positioning the dispersive element comprises apply to the dispersive element a first tilt relative to the optical axis, and wherein collecting and focusing the optical radiation comprises positioning a wedged lens to focus the optical radiation with a second tilt, opposite to the first tilt.

36. The method according to claim 35, wherein the wedged lens comprises a section of an axially-symmetrical lens.

37. A method for imaging, comprising:

projecting optical radiation at a target wavelength onto an object;

collecting and focusing the optical radiation reflected from the object, along with background radiation over a range of wavelengths, toward a plane of an image sensor;

positioning a dispersive element to direct the collected optical radiation so as to form a sharp image of the optical radiation at the target wavelength in the plane of the image sensor, while spreading the background radiation across the plane; and

processing the sharp image captured by the image sensor while rejecting interference caused by the background radiation.

38. The method according to claim 37, wherein the projected optical radiation comprises a predetermined radiation pattern, and

wherein the sharp image captured by the image sensor comprises an image of the pattern projected onto the object, and

wherein processing the image comprises constructing a 3D map of the object by processing the sharp image.

39. The method according to claim 37, wherein positioning the dispersive element comprises spreading the optical radiation collected by the optics so that different wavelengths in the range are focused along different, respective optical axes toward the plane of the image sensor.

40. The method according to claim 37, wherein positioning the dispersive element comprises focusing the radiation at the target wavelength onto the plane of the image sensor, while other wavelengths in the range are focused ahead of or behind the plane.

41. The method according to claim 40, wherein the dispersive element comprises a diffractive lens.

42. The method according to claim 37, wherein the dispersive element is configured so that the optics have a chromatic aberration in excess of one micrometer per nanometer of wavelength at the plane of the image sensor.

43. The method according to claim 37, wherein positioning the dispersive element comprises shifting a position of the dispersive element relative to the plane so as to select the target wavelength that is to be imaged sharply in the plane.

44. A method for imaging, comprising:

collecting and focusing optical radiation over a range of wavelengths along an optical path toward a plane of an image sensor; and

positioning a dispersive element in the optical path so that the radiation is focused with a chromatic aberration in excess of one micrometer per nanometer of wavelength at the plane.

45. The method according to claim 44, wherein the chromatic aberration causes different wavelengths in the range originating from a given object point to focus at different, respective image points along an axis perpendicular to the plane.

46. The method according to claim 44, wherein the chromatic aberration causes different wavelengths in the range originating from a given object point to focus along different, respective axes.