Focus adjustment device, focus adjustment method, and non-transitory storage medium storing focus adjustment program

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:

• calculating an evaluation value based on an image signal of a focus detection region set in a region of the imager where the light flux is received, thereby judging a drive direction of the focus lens to be in focus based on a difference of an evaluation value of a different position of the focus lens;
• and
• controlling a focus adjustment operation on the basis of the judged drive direction,
• wherein the drive direction is repeatedly judged, and after the focus lens is slightly driven in a first direction judged on the basis of a first evaluation value and then the focus lens is slightly driven in a second direction different from the first direction on the basis of a subsequently calculated second evaluation value, when a drive amount of the focus lens in the second direction which is calculated based on the second evaluation value does not exceed a predetermined drive amount, the slight driving of the focus lens in the first direction is forbidden even though a drive direction judged on the basis of a further subsequently calculated third evaluation value is the first direction and the slight driving of the focus lens in the second direction is continuously performed,
• wherein the slight driving of the focus lens in the first direction is not forbidden when a drive amount of the focus lens in the second direction which is calculated based on the second evaluation value exceeds the predetermined drive amount, and the drive direction is repeatedly judged by slightly driving the focus lens in the first direction, and
• wherein the focus lens is determined to be in focus when a sum of a number of times when the drive direction of the slight driving of the focus lens is changed from the first direction to the second direction and a number of the times when the drive direction is changed from the second direction to the first direction becomes a predetermined value.

A non-transitory storage medium storing a computer-readable focus adjustment program to be executed by a focus adjustment computer 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 program comprising:

• calculating an evaluation value based on an image signal of a focus detection region set in a region of the imager where the light flux is received, thereby judging a drive direction of the focus lens to be in focus based on a difference of an evaluation value of a different position of the focus lens;
• and
• controlling a focus adjustment operation on the basis of the judged drive direction,
• wherein the drive direction is repeatedly judged, and after the focus lens is slightly driven in a first direction judged on the basis of a first evaluation value and then the focus lens is slightly driven in a second direction different from the first direction on the basis of a subsequently calculated second evaluation value, when a drive amount of the focus lens in the second direction which is calculated based on the second evaluation value does not exceed a predetermined drive amount, the slight driving of the focus lens in the first direction is forbidden even though a drive direction judged on the basis of a further subsequently calculated third evaluation value is the first direction and the slight driving of the focus lens in the second direction is continuously performed,
• wherein the slight driving of the focus lens in the first direction is not forbidden when a drive amount of the focus lens in the second direction which is calculated based on the second evaluation value exceeds the predetermined drive amount, and the drive direction is repeatedly judged by slightly driving the focus lens in the first direction, and
• wherein the focus lens is determined to be in focus when a sum of a number of times when the drive direction of the slight driving of the focus lens is changed from the first direction to the second direction and a number of the times when the drive direction is changed from the second direction to the first direction becomes a predetermined value.