Electronic camera

1. An electronic camera, comprising:

an imager having an imaging surface which captures a scene through a zoom lens and a focus lens;

a first changer which changes a distance from the zoom lens to the imaging surface in response to a zoom operation by an operator;

a second changer which executes a process of changing the distance from the focus lens to the imaging surface by referring to a tracking curve, in parallel with a changing process of said first changer;

a limiter which limits a changing process of said second changer when a changing amount by said first changer has exceeded a threshold value;

an adjustor which adjusts the distance from the focus lens to the imaging surface into a distance equivalent to a focal point based on an image outputted from said imager after the zoom operation has been cancelled; and

an updater which updates the tracking curve to be referred to by said second changer based on the distance defined by said first changer and the distance defined by said adjuster, wherein said limiter includes an accumulator which accumulates the changing amount in parallel with the changing process of said first changer, and a comparer which compares an accumulated value calculated by said accumulator with the threshold value.

2. An electronic camera according to claim 1 , wherein said updater executes an updating process after an adjusting process of said adjuster is completed.

3. An electronic camera according to claim 1 , wherein said updater selects a tracking curve suitable for the distances from among a plurality of tracking curves respectively corresponding to a plurality of depths of field.

4. An electronic camera according to claim 1 , wherein the tracking curve is equivalent to a curve being plotted on a plane in which the distance from the zoom lens to the imaging surface is rendered as a first coordinate axis and the distance from the focus lens to the imaging surface is rendered as a second coordinate axis.

5. An electronic camera according to claim 1 , wherein said limiter includes a tracking curve changer which changes the tracking curve to be referred to by said second changer to a predetermined tracking curve.

6. An electronic camera according to claim 1 , further comprising a setter which executes a process of setting the distance from the focus lens to the imaging surface to a predetermined distance in association with a limiting process of said limiter.

7. A computer program embodied on a non-transitory computer readable medium in order to control an electronic camera provided with an imager having an imaging surface which captures a scene through a zoom lens and a focus lens, the program configured to cause said electronic camera to perform the steps comprising:

a first changing step of changing a distance from the zoom lens to the imaging surface in response to a zoom operation by an operator;

a second changing step of executing a process of changing the distance from the focus lens to the imaging surface by referring to a tracking curve, in parallel with a changing process of said first changing step;

a limiting step of limiting a changing process of said second changing step when a changing amount by said first changing step has exceeded a threshold value;

an adjusting step of adjusting the distance from the focus lens to the imaging surface into a distance equivalent to a focal point based on an image outputted from said imager after the zoom operation has been canceled; and

an updating step of updating the tracking curve to be referred to by said second changing step based on the distance defined by said first changing step and the distance defined by said adjusting step, wherein said limiting step includes an accumulating step of accumulating the changing amount in parallel with the changing process of said first changing step, and a comparing step of comparing an accumulated value calculated by said accumulating step with the threshold value.

8. A focal control method executed by an electronic camera provided with an imager having an imaging surface which captures a scene through a zoom lens and a focus lens, the focal control method comprising:

a first changing step of changing a distance from the zoom lens to the imaging surface in response to a zoom operation by an operator;

a second changing step of executing a process of changing the distance from the focus lens to the imaging surface by referring to a tracking curve, in parallel with a changing process of said first changing step;

a limiting step of limiting a changing process of said second changing step when a changing amount by said first changing step has exceeded a threshold value;

an adjusting step of adjusting the distance from the focus lens to the imaging surface into a distance equivalent to a focal point based on an image outputted from said imager after the zoom operation has been cancelled; and

an updating step of updating the tracking curve to be referred to by said second changing step based on the distance defined by said first changing step and the distance defined by said adjusting step, wherein said limiting step includes an accumulating step of accumulating the changing amount in parallel with the changing process of said first changing step, and a comparing step of comparing an accumulated value calculated by said accumulating step with the threshold value.

9. An electronic camera according to claim 1 ,

wherein said limiter further includes an initializer which initializes the accumulated value calculated by said accumulator every time the zoom operation is canceled.

10. An electronic camera according to claim 1 , further comprising a controller which activates said limiter when a change direction by said first changer is equivalent to a tele direction whereas stops said limiter when the change direction by said first changer is equivalent to a wide direction.

11. An electronic camera according to claim 1 , wherein said limiting step further includes an initializing step of initializing the accumulated value calculated by said accumulating step every time the zoom operation is canceled.

12. An electronic camera according to claim 7 , wherein said limiting step further includes an initializing step of initializing the accumulated value calculated by said accumulating step every time the zoom operation is canceled.

13. An electronic camera, comprising:

an imager having an imaging surface which captures a scene through a zoom lens and a focus lens;

a first changer which changes a distance from the zoom lens to the imaging surface in response to a zoom operation by an operator;

a second changer which executes a process of changing the distance from the focus lens to the imaging surface by referring to a tracking curve, in parallel with a changing process of said first changer;

a limiter which limits a changing process of said second changer when a changing manner performed by said first changer satisfies a predetermined condition under which a moving direction of said zoom lens is towards a tele direction and a moving amount of said zoom lens towards said tele direction exceeds a threshold value calculated by adding up a plurality of the moving amount towards said tele direction of the zoom lens;

an adjustor which adjusts the distance from the focus lens to the imaging surface into a distance equivalent to a focal point based on an image outputted from said imager after the zoom operation has been cancelled; and

an updater which updates the tracking curve to be referred to by said second changer based on the distance defined by said first changer and the distance defined by said adjuster.

14. A computer program embodied on a non-transitory computer-readable medium in order to control an electronic camera provided with an imager having an imaging surface which captures a scene through a zoom lens and a focus lens, the program configured to cause said electronic camera to perform the steps comprising:

a first changing step of changing a distance from the zoom lens to the imaging surface in response to a zoom operation by an operator;

a second changing step of executing a process of changing the distance from the focus lens to the imaging surface by referring to a tracking curve, in parallel with a changing process of said first changing step;

a limiting step of limiting a changing process of said second changing step when a changing manner performed by said first changing step satisfies a predetermined condition under which a moving direction of said zoom lens is towards a tele direction and a moving amount of said zoom lens towards said tele direction exceeds a threshold value calculated by adding up a plurality of the moving amount towards said tele direction of the zoom lens;

an adjusting step of adjusting the distance from the focus lens to the imaging surface into a distance equivalent to a focal point based on an image outputted from said imager after the zoom operation has been cancelled; and

an updating step of updating the tracking curve to be referred to by said second changing step based on the distance defined by said first changing step and the distance defined by said adjusting step.

15. A focal control method executed by an electronic camera provided with an imager having an imaging surface which captures a scene through a zoom lens and a focus lens, the focal control method comprising:

a first changing step of changing a distance from the zoom lens to the imaging surface in response to a zoom operation by an operator;

a second changing step of executing a process of changing the distance from the focus lens to the imaging surface by referring to a tracking curve, in parallel with a changing process of said first changing step;

a limiting step of limiting a changing process of said second changing step when a changing manner performed by said first changing step satisfies a predetermined condition under which a moving direction of said zoom lens is towards a tele direction and a moving amount of said zoom lens towards said tele direction exceeds a threshold value calculated by adding up a plurality of the moving amount towards said tele direction of the zoom lens;

an adjusting step of adjusting the distance from the focus lens to the imaging surface into a distance equivalent to a focal point based on an image outputted from said imager after the zoom operation has been cancelled; and

an updating step of updating the tracking curve to be referred to by said second changing step based on the distance defined by said first changing step and the distance defined by said adjusting step.