Abstract: An ocular optical system including a Fresnel lens having a plurality of Fresnel zones formed on a lens surface on an observation object side, the plurality of Fresnel zones being arranged concentrically side by side along an aspherical surface having a shape which is rotationally symmetric with respect to a central axis of the Fresnel lens, the ocular optical system satisfying the conditional expression 0<PAE1/PAC1?0.50, where PAE1 represents an average pitch in a radial direction of Fresnel zones formed in a portion having a radius of 15 mm or more from the central axis of the Fresnel lens, and PAC1 represents an average pitch in the radial direction of Fresnel zones formed in a portion having a radius of 15 mm or less from the central axis of the Fresnel lens excluding a first Fresnel zone.

Abstract: A scanning optical system (SL) of this scanning microscope comprises a plurality of lens components and has positive refractive power as a whole, each lens component comprising one cemented lens composed of a plurality of lenses cemented to each other, or one lens. The scanning optical system satisfies the following conditional expression. 0.007<?(nd×tc/?d)/LA<0.021 where ?(nd×tc/?d) is the sum total of nd×tc/?d of lenses of the plurality of lens components when a refractive index for the d line of a lens constituting the plurality of lens components is denoted by nd, the center thickness of the lens is denoted by tc, and the Abbe's number of the lens is denoted by ?d, and LA is the distance on an optical axis from a lens surface on the scanning mechanism side of a lens component closest to a scanning mechanism to a lens surface on the objective optical system side of a lens component closest to an objective optical system.

Abstract: This microscope objective lens (OL) is constituted by a first lens group (G1), a second lens group (G2) having a positive refractive power, a third lens group (G3) having a concave surface facing the image side, and a fourth lens group (G4) having a concave surface facing the object side. The first lens group (G1) is constituted by a plano-convex positive lens (L101) having a flat surface facing the object side, and a negative lens (L102). The first lens group satisfies the following conditional expressions. Conditional expressions 1.8<H1/H2<3.5 and 1.3<DLe/H2<3.

Abstract: A microscope objective lens (OL) comprises a first lens group (G1) having positive refractive power, a second lens group (G2) having a concave surface facing the image side, and a third lens group (G3) having a concave surface facing the object side, which are arranged in order from the object side along an optical axis. The first lens group (G1) comprises one lens component having positive refractive power, the third lens group (G3) comprises three or more lenses including two negative lenses and one positive lens, and at least one predetermined negative lens in the two negative lenses satisfies the conditional expression “?dA<40”.

Abstract: An ocular optical system (EL) comprises: a first Fresnel lens (first lens (L1)) having a first Fresnel surface (FSa) formed on the lens surface on the image display unit (11) side; and a second Fresnel lens (second lens (L2)) placed closer to the image display unit (11) than the first Fresnel lens and having a second Fresnel surface (FSb) formed on the lens surface on the image display unit (11) side. In a plurality of wall surfaces constituting the first Fresnel surface (FSa) and the second Fresnel surface (FSb) within the radii of at least 10 mm from the optical axes for the first Fresnel surface (FSa) and the second Fresnel surface (FSb), the tilt angle of a wall surface in the first Fresnel surface (FSa) relative to the optical axis for the wall surface is greater than the tilt angle of a wall surface in the second Fresnel surface (FSb) relative to the optical axis for the wall surface, for the wall surfaces that are in the same order from the optical axes for the first and the second Fresnel surfaces.

Abstract: An ocular optical system (EL) comprises a Fresnel lens (L1) including a plurality of Fresnel zones (FR) formed on a lens surface on an observation object side. The plurality of Fresnel zones (FR) are arranged concentrically side by side along an aspherical surface having a shape which is rotationally symmetric with respect to a central axis of the Fresnel lens (L1). The ocular optical system satisfies the following conditional expression. 0<PAE1/PAC1?0.50, where PAE1 represents an average pitch in a radial direction of Fresnel zones (FR) formed in a portion having a radius of 15 mm or more from the central axis of the Fresnel lens (L1), and PAC1 represents an average pitch in the radial direction of Fresnel zones (FR) formed in a portion having a radius of 15 mm or less from the central axis of the Fresnel lens (L1) excluding a first Fresnel zone (FR)(1).

Abstract: An ocular optical system (EL) comprises, in order from an eye point (EP), a first lens group (G1) having a positive refractive power and a second lens group (G2) having a positive refractive power. The second lens group (G2) includes a cemented lens having two optical members cemented together. A cemented surface of the cemented lens is a diffraction optical surface configuring a diffraction grating. A lens surface on one side in a lens constituting the first lens group (G1) is a first Fresnel surface (FSa), and a lens surface on one side in the cemented lens of the second lens group (G2) is a second Fresnel surface (FSb).

Abstract: An ocular optical system (EL) comprises, in order from an eye point (EP), a first lens group (G1) having a positive refractive power and a second lens group (G2) having a positive refractive power. The second lens group (G2) includes a cemented lens having two optical members cemented together. A cemented surface of the cemented lens is a diffraction optical surface configuring a diffraction grating. A lens surface on one side in a lens constituting the first lens group (G1) is a first Fresnel surface (FSa), and a lens surface on one side in the cemented lens of the second lens group (G2) is a second Fresnel surface (FSb).