Abstract: An optical system includes, in order from an object side to an image side, a front unit having positive refractive power, an aperture stop, and a rear unit having positive refractive power. The front unit includes, in order from the image side to the object side, a first aspheric lens, a first negative lens, and a first positive lens. The rear unit includes, in order from the image side to the object side, a second aspheric lens, a second negative lens, and a second positive lens. The first aspheric lens includes an aspheric surface having an inflection point in a section including an optical axis. A predetermined condition is satisfied.

Abstract: An optical system includes an aperture stop closest to an object and a plurality of lenses. The plurality of lenses includes a first positive lens convex toward an object side, a first negative lens convex toward the object side, a first cemented lens, and a second cemented lens arranged consecutively in this order from the object side to an image side. The first cemented lens and the second cemented lens each include a negative lens concave toward the object side and a positive lens cemented to the negative lens, and the negative lens and the positive lens are arranged in this order from the object side to the image side.

Abstract: An optical system includes a negative lens and a positive lens adjacent to each other, wherein the following inequalities are satisfied: 0.00?DAB?1.00, and 0.80?RA/RB?1.20, where DAB[mm] denotes a distance on an optical axis between the negative lens and the positive lens, and RA and RB denote curvature radii of facing lens surfaces of the negative lens and the positive lens, respectively, and wherein specific inequalities are satisfied.

Abstract: A system includes an aperture diaphragm, a first lens configured to be disposed next to the aperture diaphragm on an object side, and to include one or more positive lenses and one or more negative lenses, and a second lens configured to be disposed next to the aperture diaphragm on an image side, and to include one or more positive lenses and one or more negative lenses. Predetermined conditions are satisfied.

Abstract: An optical system includes a diaphragm, and a first cemented lens disposed adjacent to an object side of the diaphragm. The first cemented lens included a negative lens. A predetermined condition is satisfied.

Abstract: An optical system for converting light from an object into parallel light, and guiding the parallel light to a plurality of image forming units each configured to form an image of the object includes a first lens unit having positive or negative refractive power and a second lens unit having positive refractive power that are disposed in order from an object side, wherein the first lens unit and the second lens unit are disposed at a widest interval in the optical system, and wherein the first lens unit consists of at least one positive lens and at least one negative lens that are disposed in order from the object side.

Abstract: An optical apparatus includes: an optical system; and a holding member configured to hold the optical system, wherein the holding member includes a first connection portion provided on an object side of the optical system, and a second connection portion provided between the optical system and the first connection portion, and wherein a lens apparatus is detachably mountable to the optical apparatus via the first connection portion, and an optical element is detachably mountable to the optical apparatus via the second connection portion.

Abstract: An optical system includes a first optical element including a first reflecting region having a convex shape toward an enlargement side, a second optical element having a reduction-side surface having a convex shape toward the enlargement side, and a third optical element having an enlargement-side surface having a convex shape toward the enlargement side, wherein the reduction-side surface of the second optical element or the enlargement-side surface of the third optical element includes a second reflecting region, wherein the third optical element includes a refracting region having positive power, and wherein light from the enlargement side proceeds to a reduction side sequentially through a refracting region of the first optical element, the second reflecting region, the first reflecting region, a refracting region of the second optical element, and the refracting region of the third optical element.

Abstract: An optical apparatus includes: an optical system; and a holding member configured to hold the optical system, wherein the holding member includes a first connection portion provided on an object side of the optical system, and a second connection portion provided between the optical system and the first connection portion, and wherein a lens apparatus is detachably mountable to the optical apparatus via the first connection portion, and an optical element is detachably mountable to the optical apparatus via the second connection portion.

Abstract: An optical system for converting light from an object into parallel light, and guiding the parallel light to a plurality of image forming units each configured to form an image of the object includes a first lens unit having positive or negative refractive power and a second lens unit having positive refractive power that are disposed in order from an object side, wherein the first lens unit and the second lens unit are disposed at a widest interval in the optical system, and wherein the first lens unit consists of at least one positive lens and at least one negative lens that are disposed in order from the object side.

Abstract: Provided is a zoom lens, including, in order from an object side to an image side, first, second, and third lens units having positive, negative, and positive refractive powers, respectively. The second lens unit moves toward image side during zooming from a wide angle end to a telephoto end, and an interval between adjacent lens units is changed during zooming. The first lens unit includes a lens pair of a positive lens (LP1) and a negative lens (LN1) that are arranged adjacent to each other. A refractive index of a material at 400 nm wavelength, a refractive index of a material at 1,050 nm wavelength, a refractive index of a material at 1,700 nm wavelength, an Abbe number and a partial dispersion ratio of a material, Abbe numbers and partial dispersion ratios of materials for the positive lens (LP1) and the negative lens (LN1) are each appropriately set.

Abstract: An optical system includes a first optical element including a first reflecting region having a convex shape toward an enlargement side, a second optical element having a reduction-side surface having a convex shape toward the enlargement side, and a third optical element having an enlargement-side surface having a convex shape toward the enlargement side, wherein the reduction-side surface of the second optical element or the enlargement-side surface of the third optical element includes a second reflecting region, wherein the third optical element includes a refracting region having positive power, and wherein light from the enlargement side proceeds to a reduction side sequentially through a refracting region of the first optical element, the second reflecting region, the first reflecting region, a refracting region of the second optical element, and the refracting region of the third optical element.

Abstract: Provided is a zoom lens, comprising, in order from an object side to an image side: a first lens unit having a positive refractive power; a second lens unit having a negative refractive power; a third lens unit having a negative refractive power; and a fourth lens unit having a positive refractive power. The second lens unit and the third lens unit are configured to move along loci different from each other during zooming. At least one lens unit of the first lens unit, the second lens unit, the third lens unit, or the fourth lens unit includes a positive lens and a negative lens that are arranged adjacent to each other, and materials for the positive lens and the negative lens are appropriately set, respectively.

Abstract: Provided is a zoom lens, comprising, in order from an object side to an image side: a first lens unit having a positive refractive power; a second lens unit having a negative refractive power; and a third lens unit having a positive refractive power. The second lens unit is configured to move toward the image side during zooming from a wide angle end to a telephoto end, and an interval between adjacent lens units is changed during zooming. The first lens unit includes a positive lens and a negative lens that are arranged adjacent to each other. Materials for the positive lens and the negative lens are appropriately set.

Abstract: Provided is a zoom lens, comprising, in order from an object side to an image side: a first lens unit having a positive refractive power; a second lens unit having a negative refractive power; a third lens unit having a negative refractive power; and a fourth lens unit having a positive refractive power. The second lens unit and the third lens unit are configured to move along loci different from each other during zooming. At least one lens unit of the first lens unit, the second lens unit, the third lens unit, or the fourth lens unit includes a positive lens and a negative lens that are arranged adjacent to each other, and materials for the positive lens and the negative lens are appropriately set, respectively.

Abstract: Provided is a zoom lens, including, in order from an object side to an image side, first, second, and third lens units having positive, negative, and positive refractive powers, respectively. The second lens unit moves toward image side during zooming from a wide angle end to a telephoto end, and an interval between adjacent lens units is changed during zooming. The first lens unit includes a lens pair of a positive lens (LP1) and a negative lens (LN1) that are arranged adjacent to each other. A refractive index of a material at 400 nm wavelength, a refractive index of a material at 1,050 nm wavelength, a refractive index of a material at 1,700 nm wavelength, an Abbe number and a partial dispersion ratio of a material, Abbe numbers and partial dispersion ratios of materials for the positive lens (LP1) and the negative lens (LN1) are each appropriately set.

Abstract: An image-pickup apparatus includes an illumination optical system, an imaging optical system, and an image sensor. The illumination optical system includes an adjustable diaphragm configured to adjust a light quantity of the excited light. The imaging optical system includes a light shield arranged at a position conjugate with a position of the adjustable diaphragm, and configured to shield light on and around an optical axis. A·M<B?1.3A·M is satisfied, where A is an aperture diameter of the adjustable diaphragm, B is a diameter of the light shield, and M is an imaging magnification of an optical system that includes part of the illumination optical system between the adjustable diaphragm and the light shield, and part of the imaging optical system between the adjustable diaphragm and the light shield.

Abstract: A catadioptric optical system of the present invention includes a catadioptric unit configured to condense light fluxes from an object and to form an intermediate image of the object, a field lens disposed at a position where the intermediate image are formed, and a dioptric unit configured to form the intermediate image on an image surface, and when ?cat denotes a smallest Abbe number in Abbe numbers of materials of the first and second optical elements configuring the catadioptric unit and ?dio denotes a smallest Abbe number in Abbe numbers of materials of a plurality of dioptric optical elements configuring the dioptric unit, ?dio<?cat is satisfied.

Abstract: The image acquisition apparatus includes an imaging optical system configured to form an image of an object, multiple image sensors each configured to capture an image of the object through the imaging optical system, multiple variable angle prisms disposed between the imaging optical system and the image sensors, and the variable angle prisms each being paired with one of the image sensors. A controller is configured to control each variable angle prism to correct defocus of the imaging optical system on the image sensor paired with that variable angle prism.

Abstract: A phase difference observation apparatus includes an illumination optical system configured to introduce light from a light source onto an illumination surface, an opening unit provided inside the illumination optical system and including a plurality of openings, an imaging optical system configured to collect light from the illumination surface, and a complex amplitude modulation unit provided inside the imaging optical system and including a plurality of complex amplitude modulation regions, and the plurality of openings and the plurality of complex amplitude modulation regions radially extend around an optical axis of the illumination optical system or the imaging optical system.