Autofocusing still and video images

1. A method for operating an autofocus system for focusing an image on an electronic imager, comprising:

a. providing an adjustable lens system defining an optical path for scene light and having at least one movable lens to focus an image of the scene onto the electronic imager and wherein the electronic imager includes color and unfiltered or panchromatic pixels;

b. causing a first portion of the scene light to be obscured so that the color pixels and unfiltered or panchromatic pixels of the electronic imager captures a first autofocus image and causing a second different portion of the scene light to be obscured so that the color pixels and unfiltered or panchromatic pixels of the electronic imager captures a second autofocus image wherein portions of the first and second autofocus images are offset; and

c. moving the movable lens in response to the offset to a position so that an image to be captured will be in focus.

2. The method for operating an autofocus system of claim 1 further including a split aperture device effective in first and second conditions for blocking light and transmitting light respectively.

3. The method for operating an autofocus system of claim 2 wherein the split aperture device is formed with at least one liquid crystal element having two independently operated pixels.

4. The method for operating an autofocus system of claim 2 wherein the split aperture device is a mechanical shutter with first, second and third operating states; wherein the first and second operating states restrict the light in the first and second portions of the optical path respectively and the third operating state allows the light to pass substantially unrestricted to illuminate the electronic imager.

5. The method for operating an autofocus system of claim 4 wherein the mechanical shutter is a rotating disk wherein portions of the disk have been removed to provide the first, second and third operating states.

6. The method for operating an autofocus system of claim 4 wherein the mechanical shutter is composed of one or more sliding members providing the first, second and third operating states.

7. The method for operating an autofocus system of claim 1 wherein the autofocus system is used repeatedly during video capture to focus the video frames.

8. The method for operating an autofocus system of claim 7 wherein the first and second autofocus images are alternately captured with video frames.

9. The method for operating an autofocus system of claim 7 wherein the autofocus images are corrected for the relative motion of the autofocus system and objects in the scene that occurs between the first and second autofocus images.

10. The method for operating an autofocus system of claim 7 wherein the focus change between video images are limited to remain below a selected value to produce a smoother focus transition as the scene changes.

11. An autofocus system for focusing an image on an electronic imager during video capture, comprising:

a. an adjustable lens system defining an optical path having at least one movable lens to focus an image onto the electronic imager;

b. a split aperture device which includes first and second light transmitting portions each being effective in first and second conditions for respectively restricting light along the optical path from reaching the electronic imager and transmitting light onto the electronic imager;

c. means for operating the split aperture device repeatedly during video capture to cause the first portion to be in the first condition and the second portion to be in the second condition so that the electronic imager captures a first autofocus image and then to cause the first portion to be in the second condition and the second portion to be in the first condition so that the electronic imager captures a second autofocus image wherein portions of the first and second autofocus images are offset;

d. means responsive to the offset for causing the adjustable lens system to focus the image onto the electronic imager and wherein the first and second autofocus images are alternately captured between video frames and wherein the focus change between video frames is limited to remain below a selected value to produce a smooth focus transition as the scene changes; and

e. means for causing the first portion and the second portion of the split aperture device to be in the second condition when the electronic imager captures a focused image.

12. The autofocus system of claim 11 wherein the split aperture device is electro-optical and the first and second portions are effective in first and second conditions for blocking light and transmitting light respectively.

13. The autofocus system of claim 12 wherein the split aperture device is formed with at least one liquid crystal element having two independently operated pixels.

14. The autofocus system of claim 11 wherein the split aperture device is a mechanical shutter with first, second and third operating states; wherein the first and second operating states restrict the light in the first and second portions of the optical path respectively and the third operating state allows the light to pass substantially unrestricted to illuminate the electronic imager.

15. The autofocus system of claim 11 wherein the autofocus images are corrected for the relative motion of the autofocus system and objects in the scene that occurs between the first and second autofocus images.

16. The autofocus system of claim 11 wherein the electronic imager includes color pixels and unfiltered or panchromatic pixels.

17. The autofocus system of claim 16 wherein the unfiltered or panchromatic pixels are used for capturing the autofocus images.