Optical microscope with variable magnification

Claim 1

An optical microscope with variable magnification comprising: a main body; a plurality of objective lenses having different magnifications; a revolver for supporting said plurality of objective lenses and arranged on the main body rotatably such that any one of said objective lenses can be indexed into an inspection optical axis; a stage for holding a specimen under inspection and arranged on the main body movably in a plane which is perpendicular to the inspection optical axis; a monitoring means for picking-up an image of the specimen by means of one of said objective lenses when it is indexed into the inspection optical axis and including a monitor screen on which the picked-up image of the specimen is displayed; an indicating means for indicating a desired region in the image of the specimen while it is being displayed on the monitor screen by specifying a region of said monitor screen; a controlling means, responsive to said indicating means, for calculating control data which represents a necessary magnification and a necessary position of the stage for displaying an image of the specimen within said region on the monitor screen with substantially said necessary magnification such that the image of the specimen within the desired region is displayed on substantially a full area of the monitor screen; and a driving means for driving, in accordance with said control data calculated by said controlling means, (a) said revolver to cause one of said plurality of objective lenses having a magnification which is nearest to but not larger than said necessary magnification to be automatically indexed into said inspection optical axis and (b) said stage so as to be automatically moved to position a desired portion of the specimen defined by said desired region in the displayed image of the specimen substantially into a central portion of a field of view, wherein: said controlling means comprises a memory circuit, a data entry device for entering into said memory circuit data representing the magnifications of the objective lenses set on the revolver, said memory circuit storing a magnification data table which represents the magnifications of the objective lenses entered by said data entry device, a calculating circuit for calculating the necessary magnification and the necessary position of the stage for displaying the image of the desired region on the full area of the monitor screen, and a control circuit for controlling said data entry device, said memory circuit and said calculating circuit, and said calculating circuit calculates said necessary magnification as a division ratio which is represented by a ratio of an area of the desired region to the full area of the monitor screen.