Focus adjustment device and focus adjustment method

A focus adjustment device which includes an imager to receive a light flux passing through an imaging lens including a focus lens and then generate an image signal and which performs focus adjustment on the basis of the image signal, the focus adjustment device comprising:

• a focus detection region setting unit which sets focus detection regions in a region of the imager where the light flux is received, the focus detection regions being at least partly the same and being different in size;
• a direction judgment unit which calculates a first evaluation value based on an image signal of a first focus detection region among the focus detection regions to judge a drive direction of the focus lens to be in focus, and calculates a second evaluation value based on an image signal of at least one second focus detection region smaller than the first focus detection region among the focus detection regions to judge a drive direction of the focus lens to be in focus;
• and
• a control unit which controls a focus adjustment operation on the basis of the direction judged by the direction judgment unit,
• wherein the control unit determines whether a far-and-near mixing subject is present from a change of the second evaluation value when the focus lens is slightly driven a first number of times in a first direction judged on the basis of the first evaluation value and the focus lens is slightly driven a second number of times smaller than the first number of times in a second direction opposite to the first direction, and the control unit performs focus adjustment on the basis of the second evaluation value when the far-and-near mixing subject is present.

A focus adjustment method to perform focus adjustment on the basis of an image signal from an imager which receives a light flux passing through an imaging lens including a focus lens and then generates the image signal, the focus adjustment method comprising:

• setting focus detection regions in a region of the imager where the light flux is received, the focus detection regions being at least partly the same and being different in size;
• judging a drive direction of the focus lens to be in focus on the basis of a first evaluation value based on an image signal of a first focus detection region among the focus detection regions;
• judging a drive direction of the focus lens to be in focus on the basis of a second evaluation value based on an image signal of at least one second focus detection region smaller than the first focus detection region among the focus detection regions;
• determining whether a change of the second evaluation value is a monotonous change when the focus lens is slightly driven a first number of times in a first direction judged on the basis of the first evaluation value and the focus lens is slightly driven a second number of times smaller than the first number of times in a second direction opposite to the first direction;
• and
• performing focus adjustment on the basis of the second evaluation value when the change of the second evaluation value is not a monotonous change.

A focus adjustment method to perform focus adjustment on the basis of an image signal from an imager which receives a light flux passing through an imaging lens including a focus lens and then generates the image signal, the focus adjustment method comprising:

• setting focus detection regions in a region of the imager where the light flux is received, the focus detection regions being at least partly the same and being different in size;
• judging a drive direction of the focus lens to be in focus on the basis of a first evaluation value based on an image signal of a first focus detection region among the focus detection regions;
• judging a drive direction of the focus lens to be in focus on the basis of a second evaluation value based on an image signal of at least one second focus detection region smaller than the first focus detection region among the focus detection regions;
• determining whether a far-and-near mixing subject is present from a change of the second evaluation value when the focus lens is slightly driven a first number of times in a first direction judged on the basis of the first evaluation value and the focus lens is slightly driven a second number of times smaller than the first number of times in a second direction opposite to the first direction;
• and
• performing focus adjustment on the basis of the second evaluation value when the far-and-near mixing subject is present.