Auto focus adjusting method, auto focus adjusting apparatus, and digital photographing apparatus including the same

• US 9,152,010 B2
• Filed: 08/03/2012
• Issued: 10/06/2015
• Est. Priority Date: 08/05/2011
• Status: Active Grant

• Current Assignee: Samsung Electronics Co. Ltd.
• Original Assignee: Samsung Electronics Co. Ltd.
• Inventors: Hamada, Masataka
• Primary Examiner(s): Moe, Aung S
• Assistant Examiner(s): HSU, AMY R
• Application Number:
  US13/566,002
• Publication Number:
  US 20130033638A1
• Time in Patent Office: 1,159 Days
• Field of Search: 348/345, 348/349, 348/352, 348/354, 348/356
• US Class Current: 1/1
• CPC Class Codes: G02B 7/38 measured at different points on the optical axis , e.g. focussing on two or more planes and comparing image data
• CPC Class Codes: G03B 3/10 Power-operated focusing
• CPC Class Codes: H04N 23/63 by using electronic viewfinders
• CPC Class Codes: H04N 23/663 for controlling interchangeable camera parts based on electronic image sensor signals
• 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 23/73 by influencing the exposure time

Abstract

An auto focus (AF) adjusting method, an AF adjusting apparatus, and a digital photographing apparatus including the same, the AF adjusting apparatus including: an AF calculator for calculating focus detection evaluation values; a peak detector for detecting a peak position of the focus detection evaluation values; and a speed calculator for calculating a moving speed of a subject by using the peak position. When continuous photographing of still images is performed, the peak detector detects the peak position in an image pickup interval before a light exposure preparation interval for image capturing, and the focus lens driver performs moving body compensation driving for compensating for a focal position by using a moving speed calculated in the light exposure preparation interval before capturing starts.

Claims

1. An auto focus (AF) adjusting apparatus comprising:

an image pickup lens in which a position of a focus lens is variable for focus adjustment;

a focus lens driver for driving the focus lens;

an image pickup device for generating an image signal by picking up light which has passed through the image pickup lens;

an AF calculator for calculating focus detection evaluation values from the image signal;

a focal position detector for detecting a focal position of the focus detection evaluation values;

a shutter for controlling light exposure of the image pickup device; and

a speed calculator for calculating a moving speed of a subject by using detecting a change in the focal position over a period of time,

wherein, when continuous photographing for continuously capturing still images is performed;

after the previous still image capturing, the focal position detector detects the focal position in an image pickup interval before a light exposure preparation interval for a subsequent still image capturing; and

the focus lens driver performs moving body compensation driving for compensating for the focal position by using the moving speed calculated in the light exposure preparation interval before the subsequent still image capturing starts.

2. The AF adjusting apparatus of claim 1, wherein the shutter is a mechanical shutter including a front curtain and a rear curtain.

3. The AF adjusting apparatus of claim 2, wherein the moving body compensation driving is performed before driving to change the shutter to a closed state is completed.

4. The AF adjusting apparatus of claim 1, wherein the shutter is an electronic front curtain shutter including an electronic front curtain for beginning light exposure by resetting electric charges and a mechanical rear curtain for ending the light exposure.

5. The AF adjusting apparatus of claim 4, wherein the moving body compensation driving is performed in an interval before beginning to drive the electronic front curtain for the subsequent image capturing after stopping driving for selectively reading electric charges from the image pickup device.

6. The AF adjusting apparatus of claim 1, wherein the shutter is a global shutter including an electronic front curtain for beginning light exposure by resetting electric charges and an electronic rear curtain for ending the light exposure.

7. The AF adjusting apparatus of claim 6, wherein the moving body compensation driving is performed in an interval before beginning to drive the electronic front curtain for image capturing after stopping driving for selectively reading electric charges from the image pickup device.

8. The AF adjusting apparatus of claim 1, wherein the AF adjusting apparatus ends displaying before the subsequent still image capturing, and

the moving body compensation driving is performed in an interval before beginning the image capturing after ending the displaying.

9. The AF adjusting apparatus of claim 1, wherein the detection of the focal position is performed by driving the focus lens back and forth.

10. The AF adjusting apparatus of claim 1, wherein, during the continuous photographing, detecting the focal position multiple times is performed in the image pickup interval before the light exposure preparation interval, and the moving speed of the subject is calculated from a result of the detecting of the focal position multiple times.

11. The AF adjusting apparatus of claim 1, wherein, during the continuous photographing, the focal position detection is performed at least once in the image pickup interval before the light exposure preparation interval for every still image capturing, and the moving speed of the subject is calculated by using a focal position result detected in the image pickup interval for current still image capturing and a focal position result detected in the image pickup interval for the previous still image capturing.

12. The AF adjusting apparatus of claim 1, wherein, during the continuous photographing, when the moving speed of the subject is fast, the focal position detection is performed once in the image pickup interval before the light exposure preparation interval, and when the moving speed of the subject is slow, the focal position detection is performed multiple times in the image pickup interval before the light exposure preparation interval.

13. The AF adjusting apparatus of claim 1, wherein, during the continuous photographing, the moving speed of the subject is determined by using the moving speed of the subject acquired before the continuous photographing starts or the moving speed of the subject obtained in the previous still image capturing during the continuous photographing.

14. The AF adjusting apparatus of claim 1, wherein, when the moving speed of the subject before the continuous photographing starts is acquired, the acquired moving speed and the moving speed of the subject acquired during the continuous photographing are used to predict a focal position in the subsequent still image capturing, and

when the moving speed of the subject before the continuous photographing starts is not acquired, the moving speed of the subject acquired during the continuous photographing is used to predict a focal position in the subsequent image capturing.

15. The AF adjusting apparatus of claim 14, wherein the moving body compensation driving is performed by predicting the focal position from the moving speed of the subject and a time before the subsequent still image capturing.

16. The AF adjusting apparatus of claim 1, wherein, when the moving speed of the subject is acquired, the moving body compensation driving is performed by predicting the focal position according to movement of the subject in an interval from a light exposure end time to an image pickup start time before the light exposure preparation interval for the subsequent still image capturing by using the acquired moving speed.

17. An auto focus (AF) adjusting method of an AF adjusting apparatus capable of continuous photographing in which still images are continuously captured, the AF adjusting method is performed after previous still image capturing comprising:

generating an image signal by picking up light reflected from a subject;

calculating focus detection evaluation values from the image signal;

detecting a focal position of the focus detection evaluation values in an image pickup interval before a light exposure preparation interval for still image capturing during the continuous photographing;

calculating a moving speed of the subject by detecting a change in the focal position over a period of time; and

compensating for the focal position by using the moving speed calculated in the light exposure preparation interval.

18. A digital photographing apparatus capable of performing auto focus (AF) adjustment, the digital photographing apparatus comprising:

an image pickup lens in which the position of a focus lens is variable for focus adjustment;

a focus lens driver for driving the focus lens;

an image pickup device for generating an image signal by picking up light which has passed through the image pickup lens;

an AF calculator for calculating focus detection evaluation values from the image signal;

a focal position detector for detecting a focal position of the focus detection evaluation values;

a shutter for controlling light exposure of the image pickup device; and

a speed calculator for calculating a moving speed of a subject by using detecting a change in the focal position over a period of time,

wherein, when continuous photographing for continuously capturing still images is performed;

after previous still image capturing, the focal position detector detects the focal position in an image pickup interval before a light exposure preparation interval for subsequent still image capturing; and

the focus lens driver performs moving body compensation driving for compensating for the focal position by using the moving speed calculated in the light exposure preparation interval before the subsequent still image capturing starts.

19. The digital photographing apparatus of claim 18, wherein, when the moving speed of the subject is acquired, the moving body compensation driving is performed by predicting the focal position according to movement of the subject in an interval from a light exposure end time to an image pickup start time before the light exposure preparation interval for the subsequent still image capturing by using the acquired moving speed.