In-focus detecting device

• US 5,192,998 A
• Filed: 06/22/1992
• Issued: 03/09/1993
• Est. Priority Date: 01/05/1990
• Status: Expired due to Term

• Current Assignee: Canon Kabushiki Kaisha (Canon Inc.)
• Original Assignee: Canon Kabushiki Kaisha (Canon Inc.)
• Inventors: Tokumitsu, Jun, Suda, Shigeyuki, Sekine, Masayoshi, Yoshii, Minoru
• Primary Examiner(s): Britton, Howard W.
• Application Number:
  US07/902,548
• Time in Patent Office: 260 Days
• Field of Search: 358/41, 358/43, 358/44, 358/48, 358/227
• US Class Current: 348/349
• 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: H04N 23/67 Focus control based on electronic image sensor signals

Abstract

An in-focus detecting device is arranged to detect the width of a color transition area of an object image from the color components of a video signal and to determine an in-focus state by evaluating the width.

Claims

1. An in-focus detecting device comprising:

a) detecting means for detecting a width of a color transition area of a photographed object on the basis of color components of a video signal obtained from said color transition area; and

b) in-focus determining means for determining an in-focus state on the basis of an output of said detecting means.

2. A device according to claim 1, wherein said color transition area is an area in which a single color varies.

3. A device according to claim 1, wherein said detecting means is arranged to detect an edge width of color signal included in said video signal.

4. A device according to claim 3, wherein said detecting means includes pulse generating means arranged to generate a pulse signal corresponding to the width of said color transition area, and wherein said determining means is arranged to determine an in-focus state on the basis of a width of said pulse signal.

5. A device according to claim 4, wherein said determining means is arranged to determine that an in-focus state is attained when the width of said color transition area represented by the width of said pulse signal is at a minimum value.

6. A device according to claim 1, wherein said color transition area is an area in which a plurality of pieces of color information are mixed in color.

7. A device according to claim 6, wherein said color information includes R, G and B signals included in said video signal.

8. A device according to claim 7, wherein said detecting means is arranged to normalize color information signals by using minimum and maximum values of said R, G and B signals.

9. A television camera comprising:

a) image sensing means for sensing an image of a photographed object and for producing an image sensing signal;

b) detecting means for detecting, from said image sensing signal, color information obtained from a color transition area in which a color of the object varies; and

c) determining means for determining an in-focus state on the basis of an output of said detecting means.

10. A camera according to claim 9, wherein said detecting means includes pulse generating means for generating a pulse signal corresponding to a width of said color transition area, and wherein said determining means is arranged to determine an in-focus state on the basis of a width of said pulse signal and to determine that the infocus state is attained when the width of said color transition area represented by the width of said pulse signal reaches a minimum value thereof.

11. A camera according to claim 9, wherein said color transition area is an area in which a single color varies.

12. A camera according to claim 9, wherein said color transition area is an area in which a plurality of pieces of color information are mixed in color.

13. A camera according to claim 9, wherein said color information includes R, G and B signals included in a said image sensing signal.

14. An in-focus detecting device comprising:

a) detecting means for detecting color information from a portion of a video signal corresponding to a color transition area of an object;

b) computing means for performing a predetermined computing operation on said color information detected by said detecting means, and for producing, as a focus signal, information on a width of said color transition area which varies with an in-focus state; and

c) determining means for determining an in-focus state on the basis of a change in said information on the width of said color transition area computed by said computing means.

15. A device according to claim 14, further comprising driving means for driving and controlling a focusing lens in such a way as to cause the width of said color transition area to reach a minimum value thereof.

16. A device according to claim 14, wherein said computing means includes pulse generating means arranged to generate a pulse signal corresponding to the width of said color transition area, and wherein said determining means is arranged to determine an in-focus state on the basis of a width of said pulse signal.

17. A device according to claim 16, wherein said computing means is arranged to compute the width of said color transition area of the object by adding together a plurality of color signals obtained from said color transition area.

18. A device according to claim 16, wherein said determining means is arranged to determine that an in-focus state is attained when the width of said color transition area represented by the width of said pulse signal reaches a minimum value thereof. PG,36

19. A video camera apparatus comprising:

a) image sensing means for sensing an image of a photographed object and for producing an image sensing signal;

b) memory means for storing one picture amount of said image sensing signal produced by said image sensing means;

c) detecting means for detecting, from said image sensing signal through said memory means, color signal information obtained from a color transition area in which a color of the object varies;

d) computing means for computing, on the basis of an output of said detecting means, information on a width of said color transition area; and

e) focus adjusting means for adjusting focus according to said information on the width output from said computing means.

20. An apparatus according to claim 19, wherein said memory means is a frame memory.

21. An apparatus according to claim 19, wherein said detecting means is arranged to detect an edge width of a part of said image sensing signal in which color signals of said image sensing signal varies.

22. An apparatus according to claim 19, wherein said color transition area is an area in which a plurality of pieces of color information are mixed in color.

23. An apparatus according to claim 19, wherein said computing means includes pulse generating means arranged to generate a pulse signal corresponding to the width of said color transition area, and wherein said determining means is arranged to determine an in-focus state on the basis of a width of said pulse signal.

24. An apparatus according to claim 23, wherein said focus adjusting means is arranged to drive a focusing lens in such a way as to cause the width of said color transition area represented by the width of said pulse signal to reach a minimum value thereof.