Imaging device having autofocus capability

1. An imaging device, comprising:

an imager configured to generate an image signal of a subject; and

circuitry configured to:

detect a contrast focus based on a first part of the image signal read from a first pixel in a first part of the imager, wherein the first part of the imager comprises non-divided pixels;

detect a phase difference focus based on a second part of the image signal read from a second pixel in a second part of the imager, wherein the second part of the imager comprises divided pixels;

determine a focus position of a focus lens of the imager based on the contrast focus and the phase difference focus; and

drive the focus lens to a first focal position that corresponds to a first focus evaluation value of a plurality of focus evaluation values, wherein

the focus lens is driven based on a determination that a first ratio of the first focus evaluation value to a second focus evaluation value of the plurality of focus evaluation values is within a range of values, and

the second focus evaluation value is prior to the first focus evaluation value.

2. The imaging device according to claim 1 , wherein the circuitry is further configured to:

detect the contrast focus based on the first part of the image signal read from the first pixel of the imager at a first frame rate; and

detect the phase difference focus based on the second part of the image signal read from the second pixel of the imager at a second frame rate lower than the first frame rate.

3. The imaging device according to claim 1 , wherein

the image signal is associated with at least one of the first pixel or the second pixel, and

the first pixel and the second pixel are along a direction.

4. The imaging device according to claim 1 , wherein

the first pixel is configured to receive a light beam passed through an area of an exit pupil of the imager,

the second pixel is configured to receive the light beam passed through a pair of partial areas of the exit pupil, and

the pair of partial areas are obtained by division of the area of the exit pupil.

5. The imaging device according to claim 1 , wherein

the contrast focus is associated with a contrast type auto-focus and the phase difference focus is associated with a phase difference type auto-focus, and

the phase difference type auto-focus is different from the contrast type auto-focus.

6. The imaging device according to claim 1 , wherein

the second pixel comprises a plurality of photoelectric converters along a direction,

at least one photoelectric converter of the plurality of photoelectric converters is configured to generate the image signal, and

the image signal corresponds to one of a pair of image sequences.

7. The imaging device according to claim 1 , further comprising an amplifier configured to amplify the first part of the image signal by a first amplification factor and amplify the second part of the image signal by a second amplification factor, wherein the second amplification factor is different from the first amplification factor.

8. The imaging device according to claim 1 , wherein

the first pixel comprises a first color filter and the second pixel comprises a second color filter, and

the first color filter and the second color filter are of the same color.

9. The imaging device according to claim 1 , further comprising:

a display unit configured to display an image; and

a display controller configured to:

create a preview image associated with a preview of the image; and

control the display unit to display a preview of the subject based on the created preview image.

10. The imaging device according to claim 1 , wherein

the plurality of focus evaluation values is related to the detected phase difference focus, and

the first focus evaluation value corresponds to a peak of the plurality of focus evaluation values.

11. The imaging device according to claim 10 , wherein

the second focus evaluation value corresponds to a second focal position, and

the second focal position is prior to the first focal position in movement of the focus lens.

12. The imaging device according to claim 11 , wherein the circuitry is further configured to drive the focus lens to the first focal position that corresponds to the first focus evaluation value in a number of iterations.

13. The imaging device according to claim 12 , wherein the circuitry is further configured to set the imager to a live read mode based on a determination that a second ratio of the first focus evaluation value to the second focus evaluation value is within the range of values.

14. The imaging device according to claim 11 , wherein

the circuitry is further configured to iteratively drive the focus lens to the first focal position that corresponds to the first focus evaluation value based on a determination that a second ratio of the first focus evaluation value to the second focus evaluation value is outside the range of values, and

the focus lens is iteratively driven to the first focal position by an offset in each iteration.

15. The imaging device according to claim 11 , wherein the circuitry is further configured to acquire information associated with the contrast focus from the first pixel based on a determination that a second ratio of the first focus evaluation value to the second focus evaluation value is greater than the range of values.

16. The imaging device according to claim 11 , wherein

the circuitry is further configured to calculate a third ratio of first information associated with the contrast focus at the first focal position to second information associated with the contrast focus at the second focal position, and

the third ratio is calculated based on a determination that a second ratio of the first focus evaluation value to the second focus evaluation value is greater than the range of values.

17. The imaging device according to claim 16 , wherein the first focal position is a final focal position and the second focal position is a focal position after the focus lens is driven by an amount equivalent to a focal depth.

18. The imaging device according to claim 1 , wherein the plurality of focus evaluation values is obtained based on movement of the focus lens.

19. A non-transitory computer-readable medium having stored thereon, computer-executable instructions, which when executed by an imaging device, cause the imaging device to execute operations, the operations comprising:

generating an image signal of a subject;

detecting a contrast focus based on a first part of the image signal read from a first pixel in a first part of an imager, wherein the first part of the imager comprises non-divided pixels;

detecting a phase difference focus based on a second part of the image signal read from a second pixel in a second part of the imager, wherein the second part of the imager comprises divided pixels;

determining a focus position of a focus lens of the imager based on the contrast focus and the phase difference focus; and

driving the focus lens to a first focal position that corresponds to a first focus evaluation value of a plurality of focus evaluation values, wherein the focus lens is driven based on a determination that a first ratio of the first focus evaluation value to a second focus evaluation value of the plurality of focus evaluation values is within a range of values, and

the second focus evaluation value is prior to the first focus evaluation value.

20. A method, comprising:

in an imaging device:

generating, by an imager, an image signal of a subject;

detecting, by circuitry, a contrast focus based on a first part of the image signal read from a first pixel in a first part of the imager, wherein the first part of the imager comprises non-divided pixels;

detecting, by the circuitry, a phase difference focus based on a second part of the image signal read from a second pixel in a second part of the imager, wherein the second part of the imager comprises divided pixels;

determining, by the circuitry, a focus position of a focus lens of the imager based on the contrast focus and the phase difference focus; and

driving, by the circuitry, the focus lens to a first focal position that corresponds to a first focus evaluation value of a plurality of focus evaluation values, wherein

the focus lens is driven based on a determination that a first ratio of the first focus evaluation value to a second focus evaluation value of the plurality of focus evaluation values is within a range of values, and

the second focus evaluation value is prior to the first focus evaluation value.