Focus adjustment device, imaging device and focus adjustment method

Abstract

A focus adjustment device includes an image sensor that includes imaging pixels for capturing an image formed via an imaging optical system and focus detection pixels for detecting a focus adjustment state at the imaging optical system through a first pupil division-type image shift detection method, a focus detector that detects a focus adjustment state at the imaging optical system through a second pupil division-type image shift detection method different from the first pupil division-type image shift detection method, and a focus adjustment controller that executes focus adjustment for the imaging optical system based upon the focus adjustment states detected by the image sensor and the focus detector.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows the structure adopted in the digital still camera in an embodiment;

FIG. 2 is a front view showing in detail the structure of the image sensor;

FIG. 3 is a sectional view of an imaging pixel;

FIG. 4 is a sectional view of a focus detection pixel;

FIG. 5 illustrates a pupil division-type phase difference detection method achieved in conjunction with micro-lenses;

FIG. 6 is a front view, showing the relationship between the projection areas (range-finding pupils) of the pair of photoelectric conversion units in a focus detection pixel over the exit pupil plane;

FIG. 7 shows the circuit structure of the image sensor;

FIG. 8 shows in detail the structure adopted in a focus detection sensor corresponding to that shown in FIG. 1;

FIG. 9 shows the range-finding pupils on the exit pupil plane in an image reformation method;

FIG. 10 shows the circuit structure of an image sensor constituting part of a focus detection sensor used for an exclusive AF operation;

FIG. 11 shows the focus detection positions assumed on the photographic image plane;

FIG. 12 presents a flowchart of the operations executed in the digital still camera (imaging device) in FIG. 1;

FIG. 13 presents a flowchart of the image shift amount detection operation;

FIG. 14 presents a flowchart of the operation executed to convert the image shift amount to a defocus amount;

FIG. 15 presents a flowchart of the verification operation executed to verify the photographic subject capturing AF area;

FIG. 16 illustrates the focus detection calculation algorithm;

FIG. 17 presents a flowchart of the focus detection operation;

FIG. 18 presents another positional arrangement example that may be adopted in conjunction with the focus detection sensor (exclusive AF) and the image sensor (image sensor AF);

FIG. 19 presents yet another positional arrangement example that may be adopted in conjunction with the focus detection sensor (exclusive AF) and the image sensor (image sensor AF); and

FIG. 20 presents yet another positional arrangement example that may be adopted in conjunction with the focus detection sensor (exclusive AF) and the image sensor (image sensor AF).

Claims

1. A focus adjustment device, comprising: an image sensor that includes imaging pixels for capturing an image formed via an imaging optical system and focus detection pixels for detecting a focus adjustment state at the imaging optical system through a first pupil division-type image shift detection method;a focus detector that detects a focus adjustment state at the imaging optical system through a second pupil division-type image shift detection method different from the first pupil division-type image shift detection method; anda focus adjustment controller that executes focus adjustment for the imaging optical system based upon the focus adjustment states detected by the image sensor and the focus detector.

2. A focus adjustment device, comprising: an image sensor that includes imaging pixels for capturing an image formed via an imaging optical system and focus detection pixels for detecting a focus adjustment state at the imaging optical system through a first processing process;a focus detector that detects a focus adjustment state at the imaging optical system through a second processing process different from the first processing process; anda focus adjustment controller that executes focus adjustment for the imaging optical system based upon the focus adjustment states detected by the image sensor and the focus detector.

3. A focus adjustment device according to claim 1, further comprising: an optical element capable of directing a light flux from the imaging optical system along a light path extending toward the image sensor and along a light path extending toward the focus detector.

4. A focus adjustment device according to claim 1, wherein: the image sensor includes the imaging pixels and the focus detection pixels disposed on a single substrate.

5. A focus adjustment device according to claim 1, wherein: the focus detection pixels each include a micro-lens and a pair of photoelectric conversion units provided in correspondence to the micro-lens.

6. A focus adjustment device according to claim 1, wherein: the focus detector includes a pair of re-focusing lenses for reforming an image formed at a predetermined image plane of the imaging optical system and an image sensor that detects images reformed via the pair of re-focusing lenses.

7. A focus adjustment device according to claim 1, wherein: a range of focus adjustment state detection achieved through the second image shift detection method is greater than a range of focus adjustment state detection achieved through the first image shift detection method.

8. A focus adjustment device according to claim 2, wherein: a range of focus adjustment state detection achieved through the second processing process is greater than a range of focus adjustment state detection achieved through the first processing process.

9. A focus adjustment device according to claim 1, wherein: a threshold value used in the second image shift detection method as to whether or not a detection of the focus adjustment state is possible is greater than a threshold value used in the first image shift detection method as to whether or not detection of the focus adjustment state is possible.

10. A focus adjustment device according to claim 2, wherein: a threshold value used in the second processing process as to whether or not a detection of the focus adjustment state is possible is greater than a threshold value used in the first processing process as to whether or not detection of the focus adjustment state is possible.

11. A focus adjustment device, comprising: an image sensor that includes imaging pixels for capturing an image formed via an imaging optical system and focus detection pixels for detecting a focus adjustment state at the imaging optical system;a focus detector that detects a focus adjustment state at the imaging optical system; anda focus adjustment controller that executes focus adjustment for the imaging optical system based upon the focus adjustment states detected by the image sensor and the focus detector, wherein:the focus adjustment controller executes focus adjustment based upon the focus adjustment state detected by the focus detector when the focus adjustment state indicates a value greater than a predetermined value and executes focus adjustment based upon the focus adjustment state detected by the image sensor when the focus adjustment state indicates a value smaller than the predetermined value.

12. A focus adjustment device, comprising: an image sensor that includes imaging pixels for capturing an image formed via an imaging optical system and focus detection pixels for detecting a focus adjustment state at the imaging optical system;a focus detector that detects a focus adjustment state at the imaging optical system; anda focus adjustment controller that executes focus adjustment for the imaging optical system based upon the focus adjustment states detected by the image sensor and the focus detector, wherein:a range over which the focus adjustment state detected by the focus detector is judged to achieve a focus match is wider than a range over which the focus adjustment state detected by the image sensor is judged to be in focus.

13. A focus adjustment device according to claim 1, further comprising: an imaging controller that controls a start and an end of an imaging operation executed to capture an image obtained via the image sensor.

14. A focus adjustment device according to claim 13, wherein: the focus adjustment controller executes focus adjustment for the imaging optical system based upon the focus adjustment state detected by the focus detector until the imaging operation is started by the imaging controller and executes focus adjustment for the imaging optical system based upon the focus adjustment state detected by the image sensor once the imaging operation starts.

15. A focus adjustment device, comprising: an image sensor that includes imaging pixels for capturing an image formed via an imaging optical system and focus detection pixels for detecting a defocus amount indicating an extent of defocusing manifesting at the imaging optical system through a pupil division-type method;a focus detector that detects a focus adjustment state at the imaging optical system through a pupil division-type method;a focus adjustment controller that executes focus adjustment for the imaging optical system based upon the focus adjustment states detected by the image sensor and the focus detector; anda corrector that corrects the defocus amount detected by the focus detector by adding an offset thereto so as to equalize the defocus amount with the defocus amount detected by the image sensor.

16. A focus adjustment device according to claim 15, wherein: the offset represents a difference between the defocus amount detected by the image sensor and the defocus amount detected by the focus detector in correspondence to a single photographic subject.

17. A focus adjustment device according to claim 15, wherein: the offset is set in correspondence to optical characteristics of the imaging optical system.

18. A focus adjustment device according to claim 15, wherein: the offset is set in correspondence to a minimum f-number of the imaging optical system.

19. A focus adjustment device according to claim 15, further comprising: a storage device that stores the offset, wherein:the focus adjustment controller updates the offset based upon the defocus quantities detected by the image sensor and the focus detector.

20. A focus adjustment device according to claim 15, wherein: the image sensor and the focus detector each detect the defocus amount over a plurality of focus detection areas corresponding to a plurality of positions set on an estimated focus plane of the imaging optical system; andthe focus detection controller selects one of the focus detection areas based upon the defocus amount detected by the focus detector and executes focus adjustment for the imaging optical system based upon the defocus amount detected by the image sensor in correspondence to the selected focus detection area.

21. An imaging device, comprising: an image sensor that includes imaging pixels for capturing an image formed via an imaging optical system and focus detection pixels for detecting a focus adjustment state at the imaging optical system based upon a shift amount between a pair of images formed with light fluxes passing through a pair of areas on a pupil of the imaging optical system;a focus detector that detects a focus adjustment state at the imaging optical system based upon a shift amount between a pair of images formed with light fluxes passing through a pair of areas on a pupil of the imaging optical system; anda focus adjustment controller that executes focus adjustment for the imaging optical system based upon the focus adjustment state detected by the image sensor or the focus detector selected in correspondence to photographic conditions.

22. An imaging device according to claim 21, further comprising: an optical element capable of directing a light flux from the imaging optical system along a light path extending toward the image sensor and along a light path extending toward the focus detector.

23. An imaging device according to claim 21, wherein: the image sensor includes the imaging pixels and the focus detection pixels disposed on a single substrate.

24. An imaging device according to claim 21, wherein: the focus detection pixels each include a micro-lens and a pair of photoelectric conversion units provided in correspondence to the micro-lens.

25. An imaging device according to claim 21, wherein: the focus detector includes a pair of re-focusing lenses for reforming an image formed at a predetermined image plane of the imaging optical system and an image sensor that detects images reformed via the pair of re-focusing lenses.

26. An imaging device, comprising: an image sensor that includes imaging pixels for capturing an image formed via an imaging optical system and focus detection pixels for detecting a focus adjustment state at the imaging optical system based upon a shift amount between a pair of images formed with light fluxes passing through a pair of areas on a pupil of the imaging optical system;a focus detector that detects the focus adjustment state at the imaging optical system based upon a shift amount between a pair of images formed with light fluxes passing through a pair of areas on a pupil of the imaging optical system; anda focus adjustment controller that executes focus adjustment for the imaging optical system based upon the focus adjustment state detected by one of the image sensor and the focus detector selected in correspondence to photographic conditions, wherein:the focus adjustment controller executes focus adjustment for the imaging optical system based upon the focus adjustment state detected by the focus detector until an imaging operation starts and executes focus adjustment for the imaging optical system based upon the focus adjustment state detected by the image sensor once the imaging operation starts.

27. An imaging device, comprising: an image sensor that includes imaging pixels for capturing an image formed via an imaging optical system and focus detection pixels for detecting a focus adjustment state at the imaging optical system based upon a shift amount between a pair of images formed with light fluxes passing through a pair of areas on a pupil of the imaging optical system;a focus detector that detects the focus adjustment state at the imaging optical system based upon a shift amount between a pair of images formed with light fluxes passing through a pair of areas on the pupil of the imaging optical system; anda focus adjustment controller that executes focus adjustment for the imaging optical system based upon the focus adjustment state detected by one of the image sensor and the focus detector selected in correspondence to photographic conditions, wherein:the focus adjustment controller executes focus adjustment for the imaging optical system based upon the focus adjustment state detected by the focus detector while a continuous shooting is in progress.

28. An imaging device, comprising: an image sensor that includes imaging pixels for capturing an image formed via an imaging optical system and focus detection pixels for detecting a focus adjustment state at the imaging optical system based upon a shift amount between a pair of images formed with light fluxes passing through a pair of areas on a pupil of the imaging optical system;a focus detector that detects a focus adjustment state at the imaging optical system based upon a shift amount between a pair of images formed with light fluxes passing through a pair of areas on a pupil of the imaging optical system; anda focus adjustment controller that executes focus adjustment for the imaging optical system based upon the focus adjustment state detected by one of the image sensor and the focus detector selected in correspondence to photographic conditions, wherein:the focus adjustment controller executes focus adjustment for the imaging optical system based upon the focus adjustment state detected by the focus detector while a movie shooting is in progress.

29. An imaging device according to claim 22, wherein: the focus adjustment controller executes focus adjustment for the imaging optical system based upon the focus adjustment state detected by the image sensor while a continuous shooting is in progress with the light path of the imaging optical system directed toward the image sensor by the optical element.

30. An imaging device according to claim 22, wherein: the focus adjustment controller executes focus adjustment for the imaging optical system based upon the focus adjustment state detected by the image sensor while a movie shooting is in progress with the light path of the imaging optical system directed toward the image sensor by the optical element.

31. An imaging device according to claim 21, wherein: the focus adjustment controller executes focus adjustment based upon the focus adjustment state detected by the focus detector when detecting the focus adjustment state in a plurality of focus detection areas corresponding to a plurality of positions set on a predetermined image plane of the imaging optical system, and executes focus adjustment based upon the focus adjustment state detected by the image sensor when detecting the focus adjustment state in one of the plurality of focus detection areas.

32. An imaging device according to claim 21, wherein: the focus adjustment controller executes focus adjustment based upon the focus adjustment state detected by the focus detector when continuously executing the focus adjustment after the imaging optical system is in focus, and executes focus adjustment based upon the focus adjustment state detected by the image sensor if the focus adjustment is disallowed once the imaging optical system is in focus.

33. An imaging device according to claim 21, further comprising: a display at which the focus adjustment state detected by the image sensor is indicated when focus adjustment is manually executed.

34. An imaging device according to claim 21, further comprising: a monitor at which an image captured by the image sensor is displayed, wherein:the focus adjustment controller executes focus adjustment based upon the focus adjustment state detected by the image sensor when magnifying and displaying the image captured by the image sensor at the monitor, and executes focus adjustment based upon the focus adjustment state detected by the focus detector when reducing and displaying the image at the monitor.

35. An imaging device, comprising: an image sensor that includes imaging pixels for capturing an image formed via an imaging optical system and focus detection pixels for detecting a focus adjustment state at the imaging optical system based upon a shift amount between a pair of images formed with light fluxes passing through a pair of areas on a pupil of the imaging optical system;a focus detector that detects a focus adjustment state at the imaging optical system based upon a shift amount between a pair of images formed with light fluxes passing through a pair of areas on the pupil of the imaging optical system; anda focus adjustment controller that executes focus adjustment for the imaging optical system based upon the focus adjustment state detected by one of the image sensor and the focus detector selected in correspondence to photographic conditions, wherein:the focus adjustment controller executes focus adjustment based upon the focus adjustment state detected by the image sensor when a minimum f-number of the imaging optical system indicates a level brighter than a level corresponding to a predetermined value, and executes focus adjustment based upon the focus adjustment state detected by the focus detector when the minimum f-number indicates a level darker than the level corresponding to the predetermined value.

36. An imaging device according to claim 21, wherein: the focus adjustment controller executes focus adjustment based upon the focus adjustment state detected by the image sensor when an aperture value used to control the image optical system indicates a level brighter than a level corresponding to a predetermined value, and executes focus adjustment based upon the focus adjustment state detected by the focus detector when the aperture used to control the imaging optical system indicates a level darker than the level corresponding to the predetermined value.

37. An imaging device according to claim 21, wherein: the focus adjustment controller executes focus adjustment based upon the focus adjustment state detected by the image sensor when a focal length of the imaging optical system is smaller than a predetermined value, and executes focus adjustment based upon the focus adjustment state detected by the focus detector when the focal length is greater than the predetermined value.

38. An imaging device according to claim 21, wherein: the focus adjustment controller executes focus adjustment based upon the focus adjustment state detected by the image sensor when an exposure time set for an imaging operation executed at the image sensor is shorter than a predetermined length of time, and executes focus adjustment based upon the focus adjustment state detected by the focus detector when the exposure time is longer than the predetermined length of time.

39. An imaging device according to claim 21, wherein: the focus adjustment controller executes focus adjustment based upon the focus adjustment state detected by the image sensor when a sensitivity is lower than a predetermined value, and executes focus adjustment based upon the focus adjustment state detected by the focus detector if the sensitivity is higher than the predetermined value.

40. An imaging device according to claim 21, wherein: the focus adjustment controller executes focus adjustment based upon the focus adjustment state detected by the image sensor when a photographic subject is not illuminated during a photographing operation, and executes focus adjustment based upon the focus adjustment state detected by the focus detector when the photographic subject is illuminated during the photographing operation.

41. An imaging device according to claim 21, wherein: the focus adjustment controller executes focus adjustment based upon the focus adjustment state detected by the image sensor when a self-timer photographing mode is selected, and executes focus adjustment based upon the focus adjustment state detected by the focus detector when the self-timer photographing mode is not selected.

42. An imaging device according to claim 21, wherein: the focus adjustment controller executes focus adjustment based upon the focus adjustment state detected by the image sensor when the imaging device is set at a fixed position, and executes focus adjustment based upon the focus adjustment state detected by the focus detector when the imaging device is not fixed.

43. An imaging device according to claim 21, wherein: the focus adjustment controller executes focus adjustment based upon the focus adjustment state detected by the image sensor when a mode for photographing a stationary subject is set, and executes focus adjustment based upon the focus adjustment state detected by the focus detector when a mode for photographing a moving subject is set.

44. An imaging device, comprising: an image sensor that includes imaging pixels for capturing an image formed via an imaging optical system and focus detection pixels for detecting a focus adjustment state at the imaging optical system based upon a shift amount between a pair of images formed with light fluxes passing through a pair of areas on a pupil of the imaging optical system;a focus detector that detects a focus adjustment state at the imaging optical system based upon a shift amount between a pair of images formed with light fluxes passing through a pair of areas on a pupil of the imaging optical system; anda focus adjustment controller that executes focus adjustment for the imaging optical system based upon the focus adjustment state detected by one of the image sensor and the focus detector selected in correspondence to photographic conditions, wherein:the focus adjustment controller executes focus adjustment based upon the focus adjustment state detected by the focus detector when the focus adjustment state indicates a value greater than a predetermined value, and executes focus adjustment based upon the focus adjustment state detected by the image sensor when the focus adjustment state indicates a value smaller than the predetermined value.

45. An imaging device according to claim 21, wherein: the focus adjustment controller executes focus adjustment based upon the focus adjustment state detected by the image sensor when a brightness in an image field is higher than a predetermined value, and executes focus adjustment based upon the focus adjustment state detected by the focus detector when the brightness in the image field is lower than the predetermined value.

46. An imaging device according to claim 21, further comprising: a judging circuit that judges as to whether a photographic subject is stationary or moving, wherein:the focus adjustment controller executes focus adjustment based upon the focus adjustment state detected by the image sensor if the judging circuit determines that the photographic subject is stationary, and executes focus adjustment based upon the focus adjustment state detected by the focus detector if the judging circuit determines that the photographic subject is moving.

47. An imaging device according to claim 21, wherein: the focus adjustment controller executes focus adjustment based upon the focus adjustment state detected by the image sensor when no auxiliary light is radiated for focus detection, and executes focus adjustment based upon the focus adjustment state detected by the focus detector when the auxiliary light is radiated.

48. A focus adjustment method comprising: providing an image sensor that includes imaging pixels for capturing an image formed via an imaging optical system and focus detection pixels for detecting a focus adjustment state at the imaging optical system through a first processing process;providing a focus detector that detects a focus adjustment state at the imaging optical system through a second processing process different from the first processing process; andexecuting focus adjustment for the imaging optical system based upon the focus adjustment states detected by the image sensor and the focus detector.

49. A focus adjustment method comprising: providing an image sensor that includes imaging pixels for capturing an image formed via an imaging optical system and focus detection pixels for detecting a focus adjustment state at the imaging optical system;providing a focus detector that detects a focus adjustment state at the imaging optical system; andexecuting focus adjustment for the imaging optical system based upon the focus adjustment states detected by the image sensor and the focus detector, wherein:executing focus adjustment based upon the focus adjustment state detected by the focus detector when the focus adjustment state indicates a value greater than a predetermined value and executing focus adjustment based upon the focus adjustment state detected by the image sensor when the focus adjustment state indicates a value smaller than the predetermined value.

50. An imaging method comprising: providing an image sensor that includes imaging pixels for capturing an image formed via an imaging optical system and focus detection pixels for detecting a focus adjustment state at the imaging optical system based upon a shift amount between a pair of images formed with light fluxes passing through a pair of areas on a pupil of the imaging optical system;providing a focus detector that detects a focus adjustment state at the imaging optical system based upon a shift amount between a pair of images formed with light fluxes passing through a pair of areas on a pupil of the imaging optical system; andexecuting focus adjustment for the imaging optical system based upon the focus adjustment state detected by one of the image sensor and the focus detector selected in correspondence to photographic conditions.

51. An imaging method comprising: providing an image sensor that includes imaging pixels for capturing an image formed via an imaging optical system and focus detection pixels for detecting a focus adjustment state at the imaging optical system based upon a shift amount between a pair of images formed with light fluxes passing through a pair of areas on a pupil of the imaging optical system;providing a focus detector that detects a focus adjustment state at the imaging optical system based upon a shift amount between a pair of images formed with light fluxes passing through a pair of areas on a pupil of the imaging optical system;executing focus adjustment for the imaging optical system based upon the focus adjustment state detected by one of the image sensor and the focus detector selected in correspondence to photographic conditions, wherein:executing focus adjustment for the imaging optical system based upon the focus adjustment state detected by the focus detector until an imaging operation starts, and executing focus adjustment for the imaging optical system based upon the focus adjustment state detected by the image sensor once the imaging operation starts.