Automatic focusing device

• US 6,088,060 A
• Filed: 03/25/1997
• Issued: 07/11/2000
• Est. Priority Date: 09/11/1987
• Status: Expired due to Fees

• Current Assignee: Canon Kabushiki Kaisha (Canon Inc.)
• Original Assignee: Canon Kabushiki Kaisha (Canon Inc.)
• Inventors: Fujiwara, Akihiro, Suda, Hirofumi, Toyama, Masamichi, Yamada, Kunihiko
• Primary Examiner(s): Garber, Wendy
• Assistant Examiner(s): Vu, Ngoc-Yen, VU, NGOC YEN T
• Application Number:
  US08/823,607
• Time in Patent Office: 1,204 Days
• Field of Search: 348/170, 348/350, 348/345, 348/349, 348/352, 348/351, 348/354, 348/355, 396/95, 396/96, 396/121, 396/123, 396/124
• US Class Current: 348/350
• CPC Class Codes: G02B 7/36 using image sharpness techniques , e.g. image processing techniques for generating autofocus signals image data processing per se G06T; in cameras having a solid state image sensor H04N23/67
• CPC Class Codes: G02B 7/365 by analysis of the spatial frequency components of the image
• CPC Class Codes: H04N 23/61 based on recognised objects
• 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 for automatically controlling the focused state of an optical system on the basis of a video signal obtained within a focus detecting area which is set on an image sensing plane comprises: a tracing area setting circuit arranged to movably set, within said image sensing plane, an inner tracing area and an outer tracing area which surrounds the inner tracing area; a computing circuit arranged to compute information on a difference in a given frequency component of the video signal obtained from the inner and outer tracing areas in each of their different positions to which they are moved within the image sensing plane; determining means for determining the position or size of an object'"'"'s image formed within the image sensing plane from the difference information computed by the computing circuit; and a circuit which is arranged to shift the focus detecting area to the position of the object'"'"'s image determined by the determining circuit and to change the size of the focus detecting area according to the size of the object'"'"'s image.

Claims

1. A video camera apparatus, comprising:

(A) image sensing means for photoelectrically converting an object image formed on an image sensing plane to produce and output an image signal;

(B) area setting means for setting a detecting area for detecting a photographing state of the object image on said image sensing plane;

(C) detecting means for detecting a variation of a feature of the object image on the basis of the image signal corresponding to said detecting area in a first period of time;

(D) control means for controlling said area setting means in a second period of time longer than said first period of time in accordance with an output of said detecting means and for causing the position and size of said detecting area on said image sensing plane to follow the variation of the feature of said object image, to independently change said detecting area in the first period;

(E) focus detecting area setting means for setting a position of a focus detecting area in the second period of time at a center of said detecting area on said image sensing plane on the basis of the output of said detecting means; and

(F) focus control means for adjusting a focus condition in the second period on the basis of the image signal corresponding to said focus detecting area.

2. An apparatus according to claim 1, wherein said detecting means is arranged to detect a difference of levels of high frequency components in said image signal corresponding to an inside and an outside of said detecting area.

3. An apparatus according to claim 2, wherein said control means is arranged to shift the position to a position where the difference of levels of the high frequency components at the inside and the outside of the detecting area becomes maximum, in respect of said respective detecting area.

4. An apparatus according to claim 2, wherein said focus detecting area setting means is arranged to use, as the focus detecting area, the detecting area where the difference of levels of the high frequency components at the inside and outside of the detecting area becomes maximum.

5. A video processing apparatus, comprising:

(A) area setting means for setting a plurality of work areas for measuring a position and/or size of an object image on an image plane;

(B) detecting means for detecting a variation of the object image on the basis of a variation of predetermined signal components in an image signal in respect of an inner and outer part of the respective ones of said plurality of work areas in a first period of time;

(C) control means for controlling said area setting means in accordance with an output of said detecting means and for measuring the position and/or size of the object image by causing the positions and/or sizes of said plurality of work areas on said image plane to follow the variation of the object image, to independently change the work areas, respectively in the first period of time; and

(D) processing area setting means for setting in a second period of time longer than the first period of time a processing area at a position of the work area where the predetermined signal component becomes maximum among said plurality of work areas.

6. An apparatus according to claim 5, further comprising correcting means for correcting the difference of levels of the predetermined signal component based on difference of sizes of said work areas.

7. An apparatus according to claim 5, wherein said control means is arranged to shift said plurality of work areas so that a difference of luminance between the inside and the outside of each area becomes maximum.

8. An apparatus according to claim 5, wherein said processing area setting means is arranged to adopt the work area where the difference of levels of the high frequency component between the inside and the outside of the area becomes maximum, as the processing area.

9. A video camera device, comprising:

(A) image sensing means for photoelectrically converting an object image formed on an image sensing plane to produce and output an image signal;

(B) area setting means for setting detecting areas on said image sensing plane;

(C) detecting means for detecting a variation of the object image in a first period of time;

(D) control means for controlling said area setting means in accordance with an output of said detecting means in a second period of time longer than the first period of time and for causing a position and a size of the detecting area on said image sensing plane to follow the variation of the object image in the second period; and

(E) focus detecting means for detecting a focus state in the first period on the basis of said image signal corresponding to the detecting area.

10. A device according to claim 9, wherein said detecting means is arranged to detect a difference of levels of a high frequency component of a luminance signal in said image signal between the inside and outside of the detecting area.

11. A device according to claim 10, wherein said control means is arranged to change a size of the detecting area so that a difference of level of the high frequency component between the inside and the outside of the detecting area becomes maximum, in respect to the respective ones of said detecting areas.

12. A device according to claim 10, wherein said focus detecting means is arranged to adopt the detecting area where the difference of level of the high frequency component between the inside and outside becomes maximum among said plurality of detecting areas, as a focus detecting area.

13. A video processing device, comprising:

(A) imaging means for producing and outputting an image signal;

(B) area setting means for shiftably setting a processing area in an image plane;

(C) detecting means for detecting a variation of an object image on the basis of a variation of a predetermined signal component in said image signal in a first period of time;

(D) control means for controlling said area setting means in accordance with an output of said detecting means and for changing a position and a size of said processing area on said image plane, following the change of the object image in a second period of, time longer than the first period; and

(E) processing means for performing a predetermined process on the image signal corresponding to the processing area in the first period.

14. A device according to claim 13,

wherein said processing means is focusing control means for detecting a focus state on the basis of the image signal corresponding to the inside of said processing area and for driving a focusing lens to an in-focus point.

15. A device according to claim 14, wherein said area setting means is capable of setting a plurality of processing areas having different sizes.

16. A video processing method, comprising:

(A) area setting step for setting a plurality of work areas for measuring a position and/or size of an object image on a image plane;

(B) detecting step for detecting a variation of the object image on the basis of a variation of predetermined signal components in an image signal in respect of an inner and outer part of the respective ones of said plurality of work areas in a first period of time;

(C) control step for controlling a process of said area setting step in accordance with an output of said detecting step and for measuring the position and/or size of the object image by causing the positions and/or sizes of said plurality of work areas on said image plane to follow the variation of the object image, to independently change the work areas, respectively in the first period of time; and

(D) processing area setting step for setting in a second period of time longer than the first period of time a processing area at a position of the work area where the predetermined signal component becomes maximum among said plurality of work areas.

17. A method according to claim 16, further comprising correcting step for correcting the difference of levels of the predetermined signal component based on difference of sizes of said work areas.

18. A method according to claim 16, wherein said control step performs to shift said plurality of work areas so that a difference of luminance between the inside and the outside of each work area becomes maximum.

19. A method according to claim 16, wherein said processing area setting step adopts the work area where the difference of levels of the high frequency component between the inside and the outside of the area becomes maximum, as the processing area.