Automatic focusing device

• US 6,556,246 B1
• Filed: 06/10/1997
• Issued: 04/29/2003
• Est. Priority Date: 10/15/1993
• Status: Expired due to Fees

• Current Assignee: Canon Kabushiki Kaisha (Canon Inc.)
• Original Assignee: Canon Kabushiki Kaisha (Canon Inc.)
• Inventors: Suda, Hirofumi
• Primary Examiner(s): Vu, Ngoc-Yen, VU, NGOC YEN T
• Application Number:
  US08/872,682
• Time in Patent Office: 2,149 Days
• Field of Search: H04/N.5228, H04/N.5232, 348/207, 348/208, 348/349, 348/350, 348/352, 348/353, 348/354, 348/208.99, 348/208.1, 348/208.4, 348/208.6, 348/208-2-2, 396/121, 396/123, 396/133
• US Class Current: 348/352
• 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 23/675 comprising setting of focusing regions

Abstract

An automatic focusing device includes a motion vector detecting circuit which detects from a picked-up image signal a movement of a picked-up image within an image plane, a filter which extracts a signal of a predetermined frequency component from the picked-up image signal, a gate circuit which takes out from the signal extracted by the filter a signal corresponding to a focus detecting area in the image plane, an area setting circuit which corrects the position of the focus detecting area by controlling the gate circuit on the basis of a detection output of the motion vector detecting circuit, and a driving part which moves a focusing lens to an in-focus position according to the signal extracted by the gate circuit.

Claims

1. An automatic focusing device comprising:

image storing means for storing an image signal outputted from image pickup means;

motion vector detecting means for detecting from image signals a movement of an image and outputting a motion vector;

extracting means for extracting a predetermined frequency component signal from the image signals in a focus detecting area as a focus evaluating signal; and

control means for controlling said extracting means and said image storing means to simultaneously and synchronously shift a read-out region for reading out the image signal from said image storing means and the focus detecting area different from the readout region in response to a common motion vector detected by said motion vector detecting means.

2. A device according to claim 1, wherein said motion vector detecting means is arranged to detect an amount of movement of an image and a direction of the movement of the image by comparing images obtained on a plurality of field image planes and computing a correlation between the images of the field image planes.

3. A device according to claim 1, wherein said control means is arranged to control said shifting in such a manner as to move the focus detecting area in a direction in which said motion vector detected by said motion vector detecting means becomes zero.

4. A device according to claim 1, wherein said extracting means is arranged to extract a high frequency component included in the image signals.

5. A device according to claim 1, further comprising movement correcting means for correcting the movement of the image on the basis of an output of said motion vector detecting means.

6. A device according to claim 5, wherein said image storing means includes an image memory arranged to store the image signals for one picture, and means for varying a range of reading out an image from said image memory in the direction of said motion vector outputted from said motion vector detecting means.

7. An automatic focusing device comprising:

storing means for storing an image signal outputted from image pickup means;

motion vector detecting means for detecting from the image signal a movement of an image and outputting a motion vector corresponding to the movement;

image cutting-out means for electronically shifting a range of cutting out the image signal stored in the storing means on the basis of a detection output of said motion vector detecting means in such a way as to cancel the movement of the image and stabilize the image of an object formed on an image sensing plane;

filter means for extracting a signal of a predetermined frequency component from an output signal read out from said storing means by said image cutting-out means and had been corrected the movement of the image;

gate means for taking out from the signal extracted by said filter means a signal corresponding to a focus detecting area different from the range of said motion vector detecting means and shifted on the basis of the detection output of said motion vector detecting means; and

driving means for driving a focusing lens to move to an in-focus position on the basis of an output of said gate means.

8. A device according to claim 7, wherein said notion vector detecting means is arranged to detect an amount of movement of the image and a direction of the movement of the image by comparing images obtained On a plurality of field image planes and computing a correlation between the images of the field image planes.

9. A device according to claim 8, wherein said image cutting-out means is arranged to shift a position in the image signal where the image sensing plane is to be cut out, in such a way as to cause said motion vector detected by said motion vector detecting means to become zero.

10. A device according to claim 7, wherein said filter means is arranged to extract a high frequency component included in the image signal.

11. A device according to claim 7, further comprising enlarging means for enlarging the image signal outputted from said image cutting-out means.

12. A device according to claim 11, wherein said filter means is connected to a junction point between said image cutting-out means and said enlarging means.

13. A video camera comprising:

a) image pickup means arranged to output a picked-up image signal;

b) memory means for storing the image signal;

c) area setting means for setting a focus detecting area in an image plane;

d) motion detecting means for detecting an image shake by detecting movement of an image on said image plane; and

e) control means for controlling said memory means and said area setting means to simultaneously and synchronously shift said focus detecting area and a read-out area different from the focus detecting area for reading out the image signal from said memory means on the basis of a common output of said motion detecting means.

14. A video camera according to claim 13, wherein said motion detecting means is arranged to detect a motion vector from the picked-up image signal.

15. A video camera according to claim 14, wherein said control means is arranged to control the position of the focus detecting area in such a way as to cause the