FOCUS CONTROL DEVICE AND METHOD OF THE SAME

PROBLEM TO BE SOLVED: To provide a focus device that generates a focus position signal following an error of an actual focus position even in the vicinity of a boundary of an area different in a thickness, and performs a highly accurate focus position control by the focus position signal, and to provide a method that performs the highly accurate focus position control.SOLUTION: The focus control device according to the present invention comprises: an error signal correction section that performs a correction to a focus error signal indicative of an error from a focus position of an observation object to an optical system; and an area change-over detection section that, when observation areas of an optical system are changed over between an observation object area and a non-observation object area different in a height from that in the observation object area, outputs an area signal corresponding to each of the observation object area and the non-observation object area. When the area signal indicates the non-observation object area, the error signal correction section performs the correction to be a numerical value corresponding to the error from the focus position in the observation object area with respect to the focus error signal.