Vibration reduction apparatus having feedback path for motion signal, and camera system

• US 20050270380A1
• Filed: 06/06/2005
• Published: 12/08/2005
• Est. Priority Date: 06/08/2004
• Status: Active Grant

• Current Assignee: Nikon Corporation
• Original Assignee: Nikon Corporation
• Inventors: Tomita, Hiroyuki, Matsumoto, Tsuyoshi
• Granted Patent: US 7,522,188 B2
• Time in Patent Office: Days
• US Class Current: 348/208.990
• CPC Class Codes: G03B 2205/0007 Movement of one or more optical elements for control of motion blur imaging systems in general using optical elements for stabilisation of the position of the image G02B27/64
• CPC Class Codes: G03B 2217/005 Blur detection
• CPC Class Codes: H04N 23/68 for stable pick-up of the scene, e.g. compensating for camera body vibrations

Abstract

A vibration reduction apparatus estimates a reference value from a vibration detection signal, and determines a target drive position from a difference between the vibration detection signal and the estimated reference value. A driving unit drives a vibration reduction mechanism so that the vibration reduction mechanism makes a follow-up movement to the target drive position. The vibration reduction apparatus has a feedback path for feeding back a motion signal to the reference value. A feedback control unit for changing the feedback amount of the motion signal in accordance with a difference in an analytical condition of the motion signal is provided on the feedback path.

Claims

1. A vibration reduction apparatus for reducing an image vibration of an object image in an imaging unit of a camera, comprising:

a vibration reduction mechanism that changes a relative position between said imaging unit and a light beam forming the object image;

a vibration detection unit that detects a vibration of said camera and outputs a vibration detection signal;

a reference value generation unit that estimates a reference value of said vibration detection signal according to said vibration detection signal, said reference value being an output of said vibration detection unit in a stationary state that is free of the vibration;

a target drive position calculation unit that calculates a vibration component as a cause of the image vibration from a difference between said vibration detection signal and an estimated reference value, and calculates a target drive position of said vibration reduction mechanism according to the vibration component; and

a driving unit that controls said vibration reduction mechanism to follow the target drive position, wherein said reference value generation unit comprises;

a feedback path that acquires information on a motion signal and feeds back said motion signal to the reference value to thereby correct the reference value, the information on a motion signal being acquired by analyzing a shot image of said camera; and

a feedback control unit that changes an amount of feedback, to the reference value, of said motion signal in accordance with an analytical condition of said motion signal.

2. The vibration reduction apparatus according to claim 1, wherein

said feedback control unit acquires information on a frame rate of the shot image and changes the feedback amount of said motion signal to the reference value in accordance with a change in the frame rate.

3. The vibration reduction apparatus according to claim 2, wherein

said feedback control unit decreases the feedback amount as the frame rate decreases.

4. The vibration reduction apparatus according to claim 3, wherein

said feedback control unit decreases the feedback amount more gently as the frame rate decreases.

5. The vibration reduction apparatus according to claim 2, wherein

said feedback control unit sets the feedback amount at zero if the frame rate is lower than a predetermined threshold value.

6. The vibration reduction apparatus according to claim 2, wherein

said feedback control unit sets a feedback gain G of said motion signal in said feedback path according to a formula

G=a·

F+b

where a and b are constants and F is the frame rate of the shot image.

7. The vibration reduction apparatus according to claim 1, wherein

said feedback control unit suppresses the feedback amount of said motion signal when said driving unit starts driving, and cancels suppression of the feedback amount after acquiring a motion signal generated by analyzing a shot image produced after the start of driving.

8. The vibration reduction apparatus according to claim 7, wherein

said feedback control unit suppresses the feedback amount at least during a period (DLY+2/FR) from when said driving unit has started driving, where FR is the frame rate of said shot image and DLY is a waiting time from capture of the shot image to generation of said motion signal.

9. The vibration reduction apparatus according to claim 7, wherein

said feedback control unit suppresses the feedback amount at least during a period (T1+DLY+1/FR) from when said driving unit has started driving, where T1 is a time lag from when said driving unit has started driving to when a first shot image produced after the start of driving is acquired, FR is the frame rate of the shot image, and DLY is a waiting time from capture of the shot image to generation of said motion signal.

10. The vibration reduction apparatus according to claim 7, wherein

said feedback control unit suppresses the feedback amount by performing at least one of a group of operations consisting of setting the feedback amount at zero, lowering a feedback gain, and limiting said motion signal to feed back.

11. A camera system comprising:

said vibration reduction apparatus according to claim 1;

and

a camera that performs vibration reduction using said vibration reduction apparatus.