Abstract: An optical element Ggi1 includes a medium that has a refractive index distribution. This optical element satisfies conditions of |?gF(pmax)??gF(pmin)|?0.02, |??gFgi(p1)|?0.0272,|??gdgi(p1)|?0.0250, and |?gFgi(pmaxgi)??gFgi(pmingi)|?0.1.

Abstract: The optical system includes first (positive) and second (negative) lens units arranged in order from an object side to an image side, and an aperture stop disposed further on the image side than the second lens unit. The first lens unit includes at least one first optical element satisfying ?GH>0.0, ?dGH<39.5 and ndGH>1.70. The optical system satisfies 0.65<|?2/?1|<6.00 and 0.45<|??GH×?2/?12|<4.00. ?GH represents a refractive power of the first optical element when light-entrance and light-exit surfaces thereof are in contact with air, ?dGH and ndGH respectively represent an Abbe number and a refractive index of a material forming the first optical element for a d-line, ?1 and ?2 respectively represent the refractive powers of the first lens unit and the second lens unit, and ??GH represents a sum total of the refractive power ??GH of the at least one first optical element.

Abstract: A compound lens comprises three or more optical elements, including first, second, and third optical components, that are cemented together. The material of the second optical element is an organic composite material. The first optical element is cemented to one surface of the second optical element. The third optical element is disposed remotest from the first optical element in an optical axis. The diameters of effective areas of the first optical element on the cemented surface between the first and the second optical elements, and of the second optical element, and the distance ti(?) between optically effective surfaces of the i-th optical element (i=1, 2, 3) along the optical axis at diameter ? are appropriately designed. The second optical element has such a shape that the decrease in the distance between its optically effective surfaces is small in a region outside the effective surface area.

Abstract: An optical element Ggi1 includes a medium that has a refractive index distribution. This optical element satisfies conditions of |?F(pmax)??gF(pmin)|?0.02, |??gFgi(p1)|?0.0272, ??gdgi(p1)|?0.0250, and |?gFgi(pmaxgi)??gFgi(pmingi)|?0.1.

Abstract: An optical system includes a first optical element and a second optical element on at least one of an enlargement side and a reduction side relative to a point P at which a light axis and a paraxial chief ray intersect. Each of the first optical element and second optical element is composed of a solid material having a refractive light incident surface and a refractive light emergent surface. The optical system satisfies the following conditional expressions: ??gF1>0.0272, ??gF2<?0.0278, and f1×f2<0 where ??gF1 and ??gF2 denote anomalous partial dispersion values of the first and second optical elements for the g-line and F-line, respectively, and f1 and f2 denote focal lengths of the first and second optical elements, respectively, when the light incident surfaces and the light emergent surfaces of the first and second optical elements are in contact with air.

Abstract: A cemented lens comprises first, second and third optical elements respectively formed by different solid materials, the third and first optical elements being cemented to each other, and the first and the second optical elements being cemented to each other, wherein both an incident surface and an exit surface of the first and second optical elements are refracting surfaces, and the following conditional expressions are satisfied: |??gF1|>0.0272 |??gF2|>0.0272 ??gF1×??gF2<0 ?1×?<0 where ??gF1 and ??gF2 are respectively anomalous dispersion characteristics of the materials for the first and the second optical elements with respect to a g line and an F line, and ?1 and ?2 are respectively refracting powers of the first and second optical elements when both the incident surface and the exit surface of the first and the second optical element are surfaces in contact with air.

Abstract: An optical system includes a first optical element and a second optical element on at least one of an enlargement side and a reduction side relative to a point P at which a light axis and a paraxial chief ray intersect. Each of the first optical element and second optical element is composed of a solid material having a refractive light incident surface and a refractive light emergent surface. The optical system satisfies the following conditional expressions: ??gF1>0.0272, ??gF2<?0.0278, and f1×f2<0 where ??gF1 and ??gF2 denote anomalous partial dispersion values of the first and second optical elements for the g-line and F-line, respectively, and f1 and f2 denote focal lengths of the first and second optical elements, respectively, when the light incident surfaces and the light emergent surfaces of the first and second optical elements are in contact with air.

Abstract: An optical system includes a first optical element and a second optical element on at least one of an enlargement side and a reduction side relative to a point P at which a light axis and a paraxial chief ray intersect. Each of the first optical element and second optical element is composed of a solid material having a refractive light incident surface and a refractive light emergent surface. The optical system satisfies the following conditional expressions: ??gF1>0.0272, ??gF2<?0.0278, and f1×f2<0 where ??gF1 and ??gF2 denote anomalous partial dispersion values of the first and second optical elements for the g-line and F-line, respectively, and f1 and f2 denote focal lengths of the first and second optical elements, respectively, when the light incident surfaces and the light emergent surfaces of the first and second optical elements are in contact with air.

Abstract: A cemented lens comprises first, second and third optical elements respectively formed by different solid materials, the third and first optical elements being cemented to each other, and the first and the second optical elements being cemented to each other, wherein both an incident surface and an exit surface of the first and second optical elements are refracting surfaces, and the following conditional expressions are satisfied: |??gF1|>0.0272 |??gF2|>0.0272 ??gF1×??gF2<0 ?1×?<0 where ??gF1 and ??gF2 are respectively anomalous dispersion characteristics of the materials for the first and the second optical elements with respect to a g line and an F line, and ?1 and ?2 are respectively refracting powers of the first and second optical elements when both the incident surface and the exit surface of the first and the second optical element are surfaces in contact with air.

Abstract: An optical system includes a first optical element and a second optical element on at least one of an enlargement side and a reduction side relative to a point P at which a light axis and a paraxial chief ray intersect. Each of the first optical element and second optical element is composed of a solid material having a refractive light incident surface and a refractive light emergent surface. The optical system satisfies the following conditional expressions: ??gF1>0.0272, ??gF2<?0.0278, and f1×f2<0 where ??gF1 and ??gF2 denote anomalous partial dispersion values of the first and second optical elements for the g-line and F-line, respectively, and f1 and f2 denote focal lengths of the first and second optical elements, respectively, when the light incident surfaces and the light emergent surfaces of the first and second optical elements are in contact with air.