Abstract: The optical system of the microscope includes a close-up optical system that faces an object, a pair of imaging optical systems that take object light rays passing through regions of the close-up optical system, and an illuminating optical system that guides illumination light emitted from a light source to illuminate the object. Each lens included in the close-up optical system has a semicircular shape in which one side is cut out. The close-up optical system is held in a first lens barrel, and the illuminating optical system is held in a second lens barrel. The second lens barrel is arranged in the cutout space of the close-up optical system inside the first lens barrel. A light shielding member is attached to the second lens barrel to prevent a leak of the illumination light through grooves formed on the second lens barrel.

Abstract: A three-group zoom lens has, from an object side, a first group lens having a positive power, a second group lens having a negative power and a third group lens consisting of a positive lens. The second lens group includes an aperture stop. When a distance to be focused is infinity, only the first lens group and the second lens group move for zooming. At least one positive lens included in the zoom lens has an aspherical surface whose positive power is greater at a portion farther from an optical axis thereof.

Abstract: A linear imaging lens element for a scanning optical system in which light flux from a light source is formed as a linear image in the vicinity of a reflection surface of a light deflector includes a progressive power toric-aspherical surface being provided on either a surface facing the light source or on a surface facing the deflector. Cross-sectional configurations of the progressive power toric-aspherical surface, which are parallel with the plane including the optical axis and being perpendicular to the linear image, are made to be a circular arc, and the radius of curvature of each circular arc cross-sectional configuration is independently determined from the cross-sectional configuration lain on the plane which includes the optical axis and is parallel with the linear image.