Patent ID: 8143562
Filing Date: 2012-03-27
Classification: G02B,H04N

Abstract:
1. An autofocus device, comprising: a stage on which a sample is mountable; an objective lens arranged opposite to the sample mounted on the stage; a focusing unit which drives at least one of the stage and the objective lens in an optical axis direction in order to control positions of the stage and the objective lens relative to each other; a lighting unit which casts light for focusing onto the sample via the objective lens; a detection unit which detects an optical image formed by light that was cast by the lighting unit and reflected from the sample via the objective lens; a projection state changing unit which includes a lens that is provided in an optical path from the lighting unit to the detection unit, wherein the projection state changing unit is configured to change a state of the optical image projected onto the detection unit; a first in-focus state determination unit which determines an in-focus state of the sample based on a detection result obtained from the detection unit; and a first in-focus state adjustment unit which controls the projection state changing unit, while the stage and the objective lens are held at prescribed positions under control of the focusing unit, to: (i) search for a position of the projection state changing unit by moving the projection state changing unit, wherein the position is determined to be the in-focus state by the first in-focus state determination unit, and (ii) fix the projection state changing unit at the position determined to be the in-focus state by the first in-focus state determination unit, wherein after fixing the projection state changing unit at the position determined to be the in-focus state by the first in-focus state determination unit, when a position is determined not to be the in-focus state by the first in-focus state determination unit, the first in-focus state adjustment unit further controls the focusing unit, while the fixed position of the projection state changing unit is held, to drive at least one of the stage and the objective lens in the optical axis direction to consistently keep a constant distance between the objective lens and the sample mounted on the stage, such that the position is determined to be the in-focus state by the first in-focus state determination unit, and wherein the autofocus device further comprises: