Apparatus for adjusting the focal point of an operating laser beam focused by an objective

Claim 1

Apparatus for adjusting the focal spot of a working laser beam onto a microscopic target region within a transparent biological object observed under a microscope to locate that focal spot a predetermined controllable microscopic distance from an interface of said object, said apparatus comprising (a) a microscope having an objective, an eyepiece, a support for said object and means to move said support so as to bring the target region of said object into the focusing plane of said objective; (b) a working laser for emitting a parallel laser beam and an auxiliary laser for emitting a parallel laser beam in the visible wavelength region along separate paths; (c) means for collinearly superimposing said two laser beams from said paths and for introducing the superimposed beams into the microscope so as to be focused jointly through said objective onto said object; (d) first variable focusing means interposed in the path of one of said laser beams; (e) second variable focusing means interposed in the path of said superimposed working and auxiliary laser beams, said second variable focusing means comprising a lens arrangement producing intermediate focal spots of said two laser beams and means for varying the distance of said intermediate focal spots from said microscope objective; (f) first control means for controlling said first variable focusing means so as to produce a longitudinal spacing of predetermined distance between the focal spots produced by said objective; and (g) second control means for controlling said second variable focusing means independently of said first variable focusing means for moving the two focal spots jointly without varying the distance therebetween; (h) whereby the focal spot of said auxiliary laser beam may be made to appear on an interface of said object and said working laser beam may be focused said predetermined distance from said interface.