Digital Camera Patent

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

Digital Camera Patent 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.

Digital Camera Patent Claims

What is claimed is:

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.

Digital Camera Patent Description

FIELD OF THE INVENTION

The present invention relates generally to digital cameras and more specifically to digital cameras with multiple focus modes having different focusing ranges.

BACKGROUND OF THE INVENTION

Some digital cameras, like their film counterparts, include a zoom lens with multiple focus modes, each focus mode having a different focusing range. For example, a zoom lens may have a macro focus mode and a normal focus mode. A macro focus mode allows the lens to focus on objects at a shorter minimum distance for a given focal length than the normal focus mode. This mode is convenient for taking extreme close ups.

Depending on the lens design, the range of available focal lengths in each focus mode may be different. In particular, the maximum focal length may be smaller in one focus mode than in the other. For example, a zoom lens may be designed to provide focal lengths of 35 mm to 105 mm in normal focus mode and 35 mm to 75 mm in macro focus mode. A user may zoom out to 105 mm while framing a subject in normal focus mode, only to decide that macro focus mode is the better choice. Upon switching to macro focus mode, however, the digital camera necessarily drops to a smaller focal length within the available range (e.g., 75 mm) for macro focus mode, forcing the user to reframe the picture.

It is thus apparent that there is a need in the art for an improved method and apparatus for maintaining a consistent effective focal length in a digital camera.

SUMMARY OF THE INVENTION

A method for maintaining a consistent effective focal length in a digital camera is provided. An apparatus for carrying out the method is also provided.

Other aspects and advantages of the present invention will become apparent from the following detailed description, taken in conjunction with the accompanying drawings, illustrating by way of example the principles of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A and 1B are functional block diagrams of a digital camera in accordance with an illustrative embodiment of the invention.

FIGS. 2A and 2B are a flowchart of the operation of the digital camera shown in FIGS. 1A and 1B in accordance with an illustrative embodiment of the invention.

DETAILED DESCRIPTION OF THE INVENTION

In a digital camera having multiple focus modes, each focus mode having a different maximum optical focal length, a consistent effective focal length may be maintained across focus-mode changes by combining optical and digital zoom. Digital zoom is typically accomplished by cropping a digital image and, optionally, applying pixel interpolation techniques well known in the image processing art to rescale the image to its original size. In some implementations, in