FOCUS ADJUSTMENT DEVICE AND METHOD

PROBLEM TO BE SOLVED: To provide a focus adjustment device ready for a case where rapid focus adjustment is required.SOLUTION: Provided are a laser light source 11 for emitting a laser beam, a shaping optical system 16 for shaping the laser beam emitted from the laser light source 11 into an annular beam having an optical axis of the laser beam at the center, an objective lens 19 for projecting the annular beam from the shaping optical system 16 onto a subject body 2, a light receiving element 21 for receiving return light from the subject body 2, and focus adjustment units 23, 24 for performing focus adjustment with the subject body 2 based on a beam shape of the return light received by the light receiving element 21.