Method and apparatus for maintaining a consistent effective focal length in a digital camera

• US 7,116,364 B2
• Filed: 10/29/2002
• Issued: 10/03/2006
• Est. Priority Date: 10/29/2002
• Status: Expired due to Fees

• Current Assignee: Hewlett-Packard Development Company, L.P. (HP Inc.)
• Original Assignee: Hewlett-Packard Development Company, L.P. (HP Inc.)
• Inventors: Yost, Jason E., Hofer, Gregory V., Battles, Amy E.
• Primary Examiner(s): Vu, Ngoc-Yen
• Assistant Examiner(s): Giles, Nicholas G.
• Application Number:
  US10/283,905
• Publication Number:
  US 20040080660A1
• Time in Patent Office: 1,435 Days
• Field of Search: 348/240.99, 348/240.1, 348/240.2, 348/240.3, 348/345
• US Class Current: 348/240.1
• CPC Class Codes: H04N 23/67 Focus control based on electronic image sensor signals
• CPC Class Codes: H04N 23/69 Control of means for changing angle of the field of view, e.g. optical zoom objectives or electronic zooming

Abstract

A digital camera maintains a consistent effective focal length upon switching from a first focus mode to a second focus mode, the focus modes having different maximum focal lengths. Maintaining a consistent effective focal length across focus mode changes obviates the need for a user to reframe a scene upon changing focus modes.

Claims

1. A method for maintaining a consistent effective focal length in a digital camera, the digital camera having a lens system, the lens system having a first focus mode and a second focus mode, the first focus mode having a first maximum focal length, the second focus mode having a second maximum focal length, the method comprising:

determining an effective focal length of the digital camera while the lens system is in the first focus mode; and

applying sufficient digital zoom to maintain the effective focal length, when the effective focal length exceeds the second maximum focal length, the second maximum focal length is smaller than the first maximum focal length, and the lens system is switched from the first focus mode to the second focus mode.

2. The method of claim 1, wherein, while the lens system is in the first focus mode, the effective focal length is achieved by a combination of optical zoom and digital zoom.

3. The method of claim 1, wherein the effective focal length is maintained by a combination of optical zoom and digital zoom.

4. The method of claim 1, wherein the first focus mode is a macro focus mode and the second focus mode is a normal focus mode.

5. The method of claim 1, wherein the first focus mode is a normal focus mode and the second focus mode is a macro focus mode.

6. A method for maintaining a consistent effective focal length in a digital camera, the digital camera having a lens system, the lens system having a first focus mode and a second focus mode, the first focus mode having a first maximum focal length, the second focus mode having a second maximum focal length, the method comprising:

determining an effective focal length of the digital camera while the lens system is in the first focus mode; and

applying as much optical zoom as possible to maintain the effective focal length, when the effective focal length exceeds the first maximum focal length, the first maximum focal length is smaller than the second maximum focal length, and the lens system is switched from the first focus mode to the second focus mode.

7. The method of claim 6, wherein, while the lens system is in the first focus mode, the effective focal length is achieved by a combination of optical zoom and digital zoom.

8. The method of claim 6, wherein the effective focal length is maintained by a combination of optical zoom and digital zoom.

9. The method of claim 6, wherein the first focus mode is a macro focus mode and the second focus mode is a normal focus mode.

10. The method of claim 6, wherein the first focus mode is a normal focus mode and the second focus mode is a macro focus mode.

11. A digital camera, comprising:

a lens system to produce an optical image, the lens system having a first focus mode and a second focus mode, the first focus mode having a first maximum focal length, the second focus mode having a second maximum focal length;

a function to select between the first and second focus modes;

an imaging module to convert the optical image to a digital image; and

a focal length compensation module configured to apply sufficient digital zoom to the digital image to maintain an effective focal length of the digital camera, when the effective focal length exceeds the second maximum focal length, the second maximum focal length is smaller than the first maximum focal length, and the lens system is switched from the first focus mode to the second focus mode.

12. The digital camera of claim 11, wherein, while the lens system is in the first focus mode, the digital camera is configured to achieve the effective focal length by a combination of optical zoom and digital zoom.

13. The digital camera of claim 11, wherein the focal length compensation module is configured to maintain the effective focal length by a combination of optical zoom and digital zoom.

14. The digital camera of claim 11, wherein the first focus mode is a macro focus mode and the second focus mode is a normal focus mode.

15. The digital camera of claim 11, wherein the first focus mode is a normal focus mode and the second focus mode is a macro focus mode.

16. A digital camera, comprising:

a lens system to produce an optical image, the lens system having a first focus mode and a second focus mode, the first focus mode having a first maximum focal length, the second focus mode having a second maximum focal length;

a function to select between the first and second focus modes;

an imaging module to convert the optical image to a digital image; and

a focal length compensation module configured to apply as much optical zoom as possible to the optical image to maintain an effective focal length of the digital camera, when the effective focal length exceeds the first maximum focal length, the first maximum focal length is smaller than the second maximum focal length, and the lens system is switched from the first focus mode to the second focus mode.

17. The digital camera of claim 16, wherein, while the lens system is in the first focus mode, the digital camera is configured to achieve the effective focal length by a combination of optical zoom and digital zoom.

18. The digital camera of claim 16, wherein the focal length compensation module is configured to maintain the effective focal length by a combination of optical zoom and digital zoom.

19. The digital camera of claim 16, wherein the first focus mode is a macro focus mode and the second focus mode is a normal focus mode.

20. The digital camera of claim 16, wherein the first focus mode is a normal focus mode and the second focus mode is a macro focus mode.

21. A digital camera, comprising:

optical means for producing an optical image, the optical means having a first focus mode and a second focus mode, the first focus mode having a first maximum focal length, the second focus mode having a second maximum focal length;

means for selecting between the first and second focus modes;

means for converting the optical image to a digital image; and

focal length compensation means for applying sufficient digital zoom to the digital image to maintain an effective focal length of the digital camera, when the effective focal length exceeds the second maximum focal length, the second maximum focal length is smaller than the first maximum focal length, and the optical means is switched from the first focus mode to the second focus mode.

22. A digital camera, comprising:

optical means for producing an optical image, the optical means having a first focus mode and a second focus mode, the first focus mode having a first maximum focal length, the second focus mode having a second maximum focal length;

means for selecting between the first and second focus modes;

means for converting the optical image to a digital image; and

focal length compensation means for applying as much optical zoom as possible to the optical image to maintain an effective focal length of the digital camera, when the effective focal length exceeds the first maximum focal length, the first maximum focal length is smaller than the second maximum focal length, and the optical means is switched from the first focus mode to the second focus mode.