Camera focus control according to extraction range size and/or zoom rate

• US 6,166,770 A
• Filed: 07/18/1996
• Issued: 12/26/2000
• Est. Priority Date: 07/26/1995
• Status: Expired due to Term

• Current Assignee: Canon Kabushiki Kaisha (Canon Inc.)
• Original Assignee: Canon Kabushiki Kaisha (Canon Inc.)
• Inventors: Yasuda, Hitoshi
• Primary Examiner(s): LIN, BRYAN T
• Application Number:
  US08/685,178
• Time in Patent Office: 1,622 Days
• Field of Search: 348/356, 348/355, 348/354, 348/351, 348/350, 348/349, 348/345, 396/89
• US Class Current: 348/350
• CPC Class Codes: H04N 23/673 based on contrast or high frequency components of image signals, e.g. hill climbing method

Abstract

An image pickup apparatus is provided with a focus detecting device for detecting a state of focus from a picked-up image signal outputted from an image sensor, and an electronic zoom device for electrically magnifying the picked-up image signal. The image pickup apparatus is arranged to control an operation characteristic of the focus detecting device on the basis of the operating state of the electronic zoom device.

Claims

1. An image pickup apparatus comprising:

extracting means for extracting, as a focus evaluation value, a predetermined high frequency component of an image signal corresponding to an extracting range set within an image pickup plane;

focus adjusting means for adjusting focus state by moving a focus adjusting member to maximize the focus evaluation value;

extracting range varying means for varying the extracting range; and

control means for setting a evaluation value for reversing a moving direction of said focus adjusting member and varying the evaluation value according to a change of the extracting range.

2. An apparatus according to claim 1, wherein said extracting means includes a band-pass filter.

3. An apparatus according to claim 1, wherein said control means is arranged to vary a condition for reversing a moving direction of said focus adjusting member, according to a size of the extracting range.

4. An apparatus according to claim 3, wherein said focus adjusting means is arranged to move said focus adjusting member in a direction of increasing a level of the focus evaluation value and to reverse a moving direction of said focus adjusting member when the level of the focus evaluation value decreases from a peak value thereof by a predetermined threshold value after the level of the focus evaluation value reaches the peak value.

5. An apparatus according to claim 4, wherein said control means is arranged to vary the threshold value according to the size of the extracting range.

6. An apparatus according to claim 5, wherein said control means is arranged to reduce the threshold value when the extracting range is reduced.

7. An image pickup apparatus comprising:

extracting means for extracting, as a focus evaluation value, a predetermined high frequency component of a video signal corresponding to an extracting range arbitrarily set within an image pickup plane;

moving means for moving a focus adjusting member along an optical axis;

focus adjusting means for adjusting focus by causing said moving means to move said focus adjusting member in such a way as to maximize the focus evaluation value;

image magnifying means for electrically magnifying an image within the image pickup plane; and

control means for varying the extracting range according to a magnifying rate of said image magnifying means and for controlling an operation of said focus adjusting means according to a size of the extracting range.

8. An apparatus according to claim 7, wherein said focus adjusting member is a focusing lens.

9. An apparatus according to claim 8, wherein said image magnifying means includes an image memory and is arranged to perform an image magnifying process by varying a readout range set on said image memory.

10. An apparatus according to claim 9, further comprising interpolation means for interpolating between picture elements or between scanning lines of an image read out from said image memory.

11. An apparatus according to claim 9, wherein said focus adjusting means is arranged to move said focus adjusting member in a direction of increasing a level of the focus evaluation value and to reverse a moving direction of said focus adjusting member when the level of the focus evaluation value decreases from a peak value thereof by a predetermined threshold value after the level of the focus evaluation value reaches the peak value.

12. An apparatus according to claim 11, wherein said control means is arranged to vary the threshold value according to the size of the extracting range.

13. An apparatus according to claim 12, wherein said control means is arranged to reduce the threshold value when the extracting range is reduced.

14. A focus control apparatus comprising:

extracting means for extracting, as a focus evaluation value, a predetermined high frequency component of an image signal corresponding to an extracting range set within an image pickup plane;

focus adjusting means for adjusting focus state by moving a focus adjusting member to maximize a focus evaluation value;

extracting range varying means for varying the extracting range; and

control means for setting a evaluation value for reversing a moving direction of said focus adjusting member and varying the evaluation value in responsive that a size of the extracting range is changed.

15. An apparatus according to claim 14, wherein said extracting means includes a band-pass filter.

16. An apparatus according to claim 14, wherein said control means is arranged to vary a condition for reversing a moving direction of said focus adjusting member, according to a size of the extracting range.

17. An apparatus according to claim 16, wherein said focus adjusting means is arranged to move said focus adjusting member in a direction of increasing a level of the focus evaluation value and to reverse a moving direction of said focus adjusting member when the level of the focus evaluation value decreases from a peak value thereof by a predetermined threshold value after the level of the focus evaluation value reaches the peak value.

18. An apparatus according to claim 17, wherein said control means is arranged to vary the threshold value according to the size of the extracting range.

19. An apparatus according to claim 18, wherein said control means is arranged to reduce the threshold value when the extracting range is reduced.