Auto focusing apparatus selectively operable in an ordinary mode and a high speed mode

• US 6,972,799 B1
• Filed: 09/25/1998
• Issued: 12/06/2005
• Est. Priority Date: 09/26/1997
• Status: Expired due to Term

• Current Assignee: Olympus Optical Corporation Limited (Olympus Corporation)
• Original Assignee: Olympus Optical Corporation Limited (Olympus Corporation)
• Inventors: Hashimoto, Hitoshi
• Primary Examiner(s): Ho, Tuan
• Assistant Examiner(s): MISLEH, JUSTIN P
• Application Number:
  US09/160,604
• Time in Patent Office: 2,629 Days
• Field of Search: 348/222.1, 348/345, 348/347, 348/349, 348/350, 348/351, 348353-356, 348/362, 348/363, 348/364, 348/348, 348/352
• US Class Current: 348/350
• CPC Class Codes: H04N 23/651 for reducing power consumption by affecting camera operations, e.g. sleep mode, hibernation mode or power off of selective parts of the camera
• CPC Class Codes: H04N 23/673 based on contrast or high frequency components of image signals, e.g. hill climbing method
• CPC Class Codes: H04N 23/73 by influencing the exposure time

Abstract

A subject image is formed on a CCD through an imaging optical system including a focusing lens. The output from the CCD is input, through an A/D converter and the like, to an AE processor circuit for performing an auto-exposure control processing and an AF processor circuit for obtaining an evaluation value for auto-focusing through a gate circuit. When a release operation is performed, a CPU drives the focusing lens and operates the AF processor circuit and the like at a high speed frame rate if the CPU determines, on the basis of brightness evaluation values from the AE processor circuit, that the brightness of the subject is equal to or higher than predetermined brightness, and drives the focusing lens and operates the AF processor circuit and the like with high precision at an ordinary frame rate if the CPU determines that the brightness of the subject is lower than the predetermined brightness, thereby performing auto-focusing.

Claims

1. An auto focusing apparatus comprising:

an image pickup section which has an imaging plane on which a subject image is formed, and generates an image signal;

a focusing section for selectively executing;

(i) an ordinary mode of reading an image signal from an entirety of the imaging plane of said image pickup section and performing focusing at an ordinary frame rate, and (ii) a high speed mode of reading an image signal from a predetermined portion of the imaging plane of said image pickup section and performing focusing at a high speed frame rate;

an operation section for instructing a release operation; and

a control section for preferentially selecting the high speed mode depending on an image signal from the predetermined portion of the imaging plane, first after a start of the release operation, and for selecting the ordinary mode depending on an image signal from the entirety of the imaging plane, when the control section determines to fail to allow the focusing in the high speed mode.

2. An apparatus according to claim 1, wherein said focusing section determines brightness of a subject on the basis of the image signal, and selects the high speed mode and the ordinary mode in accordance with a first brightness and a second brightness lower than the first brightness, respectively.

3. An apparatus according to claim 1, wherein said focusing section detects a battery remaining quantity, and selects the high speed mode and the ordinary mode in accordance with a first magnitude of the remaining quantity and a second magnitude lower than the first magnitude, respectively.

4. An apparatus according to claim 1, wherein said image pickup section includes a focusing lens for focusing a subject image on the imaging plane, drives the focusing lens at an ordinary frame rate in the ordinary mode, and drives the focusing lens at a high speed frame rate in the high speed mode.

5. An apparatus according to claim 4, wherein said focusing section drives the focusing lens at 1/30 sec intervals in the ordinary mode, and drives the focusing lens at 1/60 sec intervals in the high speed mode.

6. An apparatus according to claim 4, wherein said focusing section calculates an evaluation value in an in focus state on the basis of the image signal from the entirety of the imaging plane, and sets the focusing lens at a position corresponding to a peak of a plurality of evaluation values obtained with movement of the focusing lens in the ordinary mode.

7. An apparatus according to claim 4, wherein said focusing section calculates an evaluation value in an in focus state on the basis of an image signal from a central portion of the imaging plane, and sets the focusing lens at a position corresponding to a peak of a plurality of evaluation values obtained with movement of the focusing lens in the high speed mode.

8. An apparatus according to claim 7, wherein said focusing section includes a gate circuit for receiving an image signal from the predetermined portion and discarding an image signal from a portion other than the predetermined portion at a high rate in the high speed mode, and means for evaluating an in focus state on the basis of the image signal from the predetermined portion.

9. An apparatus according to claim 1, wherein said focusing section sets a small display area of an auto focusing area of a finder in the high speed mode, and sets a large display area of the auto focusing area of the finder in the ordinary mode.

10. An apparatus according to claim 1, wherein said image pickup section includes a focusing lens for focusing a subject image on the imaging plane, and said focusing section decreases a feed amount of the focusing lens per frame interval in the high speed mode, and increases a feed amount of the focusing lens per frame interval in the ordinary mode.

11. An apparatus according to claim 1, wherein said image pickup section includes a focusing lens for focusing a subject image on the imaging plane, and said focusing section sets a feed amount of the focusing lens per unit time in the high speed mode to be larger than that in the ordinary mode.

12. An apparatus according to claim 1, wherein said focusing section includes an evaluation value memory for storing an autofocus evaluation value, and means for accessing said evaluation value memory from address 0 regardless of whether said focusing section is driven in the ordinary mode or the high speed mode.

13. An apparatus according to claim 1, wherein said focusing section includes a display unit for displaying a picture, and means for always displaying an image obtained immediately before setting of the high speed mode on said display unit in the high speed mode, and displaying a motion picture on said display unit in the ordinary mode.

14. An apparatus according to claim 1, wherein said focusing section sets a number of frames driven at a high speed frame rate to an even number when the high speed mode is switched to the ordinary mode.

15. An apparatus according to claim 1, wherein the control section includes a processor which determines to fail to allow the focusing in the high speed mode by checking whether a peak value of an auto-focusing evaluation value is indefinite due to an error.

16. An apparatus according to claim 1, wherein the control section determines whether the release operation is canceled when the focusing is determined, and executes the focusing when the release operation is cancelled.

17. An apparatus according to claim 1, wherein the control section determines whether the release operation is canceled when the focusing is determined, and determines whether to perform another release operation when the release operation is not cancelled.