Digital still camera and image blur correction apparatus

• US 7,701,484 B2
• Filed: 09/29/2008
• Issued: 04/20/2010
• Est. Priority Date: 06/02/2003
• Status: Expired due to Fees

• Current Assignee: Nikon Corporation
• Original Assignee: Nikon Corporation
• Inventors: Habe, Masaru
• Primary Examiner(s): Chan; Jason
• Assistant Examiner(s): Prabhakher; Pritham
• Application Number:
  US12/285,105
• Publication Number:
  US 20090040319A1
• Time in Patent Office: 568 Days
• Field of Search: 34820899-20816, 348/229.1
• US Class Current: 348/208.12
• CPC Class Codes: H04N 23/68 for stable pick-up of the scene, e.g. compensating for camera body vibrations
• CPC Class Codes: H04N 23/6812 based on additional sensors, e.g. acceleration sensors
• CPC Class Codes: H04N 23/687 by shifting the lens or sensor position
• CPC Class Codes: H04N 23/71 Circuitry for evaluating the brightness variation

Abstract

Prior to a photographing operation, an image blur quantity indicating the extent to which the image becomes blurred during the photographing operation is calculated based upon an image-capturing sensitivity having been set, and a decision is made as to whether or not the image-capturing sensitivity needs to be adjusted based upon the calculated image blur quantity. If it is decided that the sensitivity level needs to be adjusted, the image-capturing sensitivity is adjusted and the photographing operation is executed at the shutter speed calculated based upon the adjusted image-capturing sensitivity.

Claims

1. A digital still camera comprising:

a sensitivity setting device that sets an image-capturing sensitivity;

a photographing device having an image-capturing element that receives a light flux transmitted through a photographic lens and executes photoelectric conversion on the received light flux;

a photometric circuit which measures brightness of a field;

a shutter speed calculation circuit which calculates a first shutter speed according to the image-capturing sensitivity set by the sensitivity setting device and the photometric result from the photometric circuit;

a control device that operates the photographing device at the first shutter speed;

a vibration quantity detection circuit that detects a vibration quantity of the camera;

an image blur calculation device that calculates an image blur quantity at the time of photographing operation based on the first shutter speed and the vibration quantity of the camera detected by the vibration quantity detection circuit, prior to the photographing operation; and

a determination device that makes a decision as to whether the image-capturing sensitivity needs to be adjusted based upon the image blur quantity calculated by the image blur calculation device, wherein;

the sensitivity setting device adjusts the image-capturing sensitivity if the determination device determines that the image-capturing sensitivity needs to be adjusted; and

if the image-capturing sensitivity is adjusted, a second shutter speed is calculated according to the adjusted image-capturing sensitivity and the photometric result from the photometric circuit; and

the control device operates the photographing device at the second shutter speed.

2. A digital still camera according to claim 1, wherein:

if the calculated image blur quantity exceeds a predetermined limit value, the sensitivity setting device shifts the image-capturing sensitivity to a higher level so as to lower the image blur quantity to a value equal to or less than the limit value.

3. A digital still camera according to claim 2, wherein:

the image blur calculation device calculates the image blur quantity at the time of the photographing operation based on the first shutter speed, the vibration quantity of the camera detected by the vibration quantity detection circuit, and a focal length of the photographic lens.

4. A digital still camera according to claim 3, further comprising:

an optical image blur correction mechanism that reduces the extent of image blur based upon the vibration quantity detected by the vibration quantity detection circuit, wherein;

the determination device determines that the image-capturing sensitivity level needs to be adjusted if the image blur quantity cannot be lowered to a value equal to or less than the limit value through an image blur correction alone executed by the optical image blur correction mechanism.

5. A digital still camera according to claim 1, wherein:

the image blur calculation device calculates the image blur quantity at the time of the photographing operation based on the first shutter speed, the vibration quantity of the camera detected by the vibration quantity detection circuit, and a focal length of the photographic lens.

6. A digital still camera according to claim 5, further comprising:

an optical image blur correction mechanism that reduces the extent of image blur based upon the vibration quantity detected by the vibration quantity detection circuit, wherein;

the determination device determines that the image-capturing sensitivity needs to be adjusted if the image blur quantity cannot be lowered to a value equal to or less than a predetermined limit value through an image blur correction alone executed by the optical image blur correction mechanism.

7. A digital still camera according to claim 1, wherein:

the sensitivity setting device sets the image-capturing sensitivity to a lowest possible sensitivity level within a range over which the calculated image blur quantity does not exceed a predetermined limit value.

8. A digital still camera according to claim 1, further comprising:

a blur preventing mode switch operated to set/clear a blur preventing mode in which control is implemented to reduce the extent of image blur by adjusting the image-capturing sensitivity.

9. A digital still camera according to claim 1, wherein:

when adjusting the image-capturing sensitivity after the determination device determines that the image-capturing sensitivity needs to be adjusted, the sensitivity setting device sets an upper limit for the image-capturing sensitivity to a predetermined value which is set lower than a highest image-capturing sensitivity of the digital still camera.

10. A digital still camera according to claim 1, wherein:

the image-capturing sensitivity setting device does not adjust the image-capturing sensitivity if the shutter speed is set by a user.

11. An image blur correction apparatus comprising:

a sensitivity setting device that sets an image-capturing sensitivity;

an image capturing command output device that outputs a command signal for engaging an image-capturing element in photoelectric conversion at a first shutter speed according to a photometric result obtained by measuring brightness of a field and the image-capturing sensitivity set by the sensitivity setting device;

an image blur calculation device that calculates an image blur quantity at the time of photographing operation based on the first shutter speed and a vibration quantity of a camera, prior to the photographing operation; and

a determination device that makes a decision as to whether the image-capturing sensitivity needs to be adjusted based upon the image blur quantity calculated by the image blur calculation device, wherein;

the sensitivity setting device adjusts the image-capturing sensitivity if the determination device determines that the image-capturing sensitivity needs to be adjusted; and

when the image-capturing sensitivity is adjusted, the image capturing command output device outputs the command signal to the image-capturing element to engage the image-capturing element in photoelectric conversion at a second shutter speed according to the adjusted image-capturing sensitivity and the photometric result.

12. An image blur correction apparatus according to claim 11, further comprising:

a blur preventing mode switch operated to set/clear a blur preventing mode in which control is implemented to reduce the extent of image blur by adjusting the image-capturing sensitivity.