Abstract: A six group projection zoom lens downsized with broadened angle of view while aberrations are satisfactorily corrected over the entire zoom range, including a negative lens group having a negative power, a second lens group having a positive power, a third lens group having a positive power, a fourth lens group having a negative power, a fifth lens group having a positive power, and a sixth lens group having a positive power in this order from the magnification side and is configured telecentric on the reduction side. The first and sixth lens groups are fixed while the second to fifth lens groups are moved independently of each other at the time of zooming. The fifth lens group includes a plurality of lenses and a biconvex lens is disposed on the most magnification side. The projection zoom lens satisfies conditional expressions (1): (R51a+R51b)/(R51a?R51b)?0 and (2): 25.0<?d51<45.0.

Abstract: A projection zoom lens having broad angle of view, high zoom ratio, and large back focus while aberrations are corrected satisfactorily, including a negative first lens group, a positive second lens group, a positive third lens group, a negative fourth lens group, a positive fifth lens group, and a positive sixth lens group from the magnification side and is telecentric on the reduction side. When zooming, the first and sixth lens groups are fixed while the second to fifth lens groups are moved and the fourth lens group is composed of one negative lens whose magnification side surface has a greater curvature in absolute value than that of the reduction side surface, and the zoom lens satisfies conditional expression (1): ?12.0<f4/fw<?5.0, where f4 is focal length of the fourth lens group, and fw is focal length of the entire lens system at the wide angle end.

Abstract: A projection lens consists of first and second les groups and a stop. The first lens group is formed of a negative lens. The second lens group is formed of three positive lenses and a negative lens. The stop is disposed between the first and second lens groups or in the second lens group. The first and second lens groups are arranged in order from a magnification side. The projection lens is telecentric on a reduction side. The projection lens is configured to satisfy the following conditional expressions (1) and (2): 1.0?f2h/f?5.0??(1) ?2.5?f1/f??0.8??(2) where f2h is a focal length of an aspheric lens of at least one of the first and second positive lenses of the second lens group, f is a focal length of the whole system, and f1 is a focal length of the first lens group.

Abstract: The projecting zoom lens includes, sequentially from its magnification side, a negative first lens group, a positive second lens group, a negative third lens group, a positive fourth lens group, a positive or negative fifth lens group, and a positive six lens group, while the reduction side of the projecting zoom lens is formed as a telecentric system. When the power of the zoom lens is varied, the first lens group and sixth lens group are fixed, while the second to fifth lens groups move. In such power varying operation, the movement of the third lens group advances from the magnification side to the reduction side as the zoom lens goes from the wide angle end toward the tele end.

Abstract: In a zoom lens for projection, a lens group arranged farthest to the reduction side is fixed when the magnification of the zoom lens is changed, and is composed of a negative aspheric lens made of a plastic material having at least one aspheric surface and a positive lens. At least one positive lens arranged on the reduction side of a lens having the smallest effective diameter among lenses composing the zoom lens satisfies the following formula (1): ?a>80(here,(dn/dt)<0)??(1), where ?a: Abbe number of a material forming the at least one positive lens for d-line, and dn/dt: a change in the refractive index of the material forming the at least one positive lens for d-line when temperature changes from 20° C.

Abstract: Disclosed are a projection lens that has a small size, a simple inner focus structure, a high optical performance, and a wide angle of view of about 75 degrees or more, and a projection display device. A projection lens includes a first lens group having a negative refractive power, a second lens group having a positive refractive power, and a third lens group having a positive refractive power arranged in this order from a magnification side. A fifth lens arranged closest to a reduction side in the first lens group is moved along an optical axis to adjust focus. The projection lens satisfies the following conditional expression: 3.0<DG12/f<6.0 where DG12 indicates a distance between the first lens group and the second lens group and f indicates the focal length of the entire lens system.

Abstract: A zoom lens for projection includes negative first group G1, positive second group G2, positive third group G3, negative fourth group G4, positive fifth group G5, and positive sixth group G6, arranged from the magnification side of the zoom lens. The reduction side of the zoom lens is telecentric. When the magnification is changed, the first group G1 and the sixth group G6 are fixed, and the second through fifth groups G2 through G5 move. The fourth group G4 is a negative lens having a concave surface facing the magnification side, and the fifth group G5 includes at least two positive lenses and at least two negative lenses. Further, the following formula (1) is satisfied: ?5.0?f4/fw??1.2??(1), where f4: the focal length of the fourth group; and fw: the focal length of the entire system of the zoom lens at a wide angle end.

Abstract: A projection zoom lens projects an optical image of rays, which are irradiated from a light source onto a light valve and are modulated by a predetermined image displayed on the light valve, onto a screen. The projection zoom lens includes a plurality of lens groups that is formed as a telecentric system on the reduction side thereof and includes at least two movable lens groups which are movable during zooming. In the projection zoom lens, the plurality of lens groups is arranged to include, in order from a magnification side, at least a first lens group and a second lens group. The first lens group has a negative refractive power, remains stationary during zooming, and performs focusing. The second lens group has a negative refractive power and remains stationary during zooming and focusing.

Abstract: A projection variable focus lens includes seven lenses. The seven lenses include first to seventh lenses in order from a magnification side. The first and second lenses are provided closest to the magnification side and have a negative composite refractive power. The third lens has a positive refractive power. The fifth lens has a negative refractive power. The sixth lens has a positive refractive power. The seventh lens has a positive refractive power. A reduction side of a lens system is telecentric. The seven lenses are classified into three or more lens groups. Three or less lens groups among the three or more lens groups are moved to change a focal length. When the focal length varies from a wide angle end to a telephoto end, at least the third lens is moved from the reduction side to the magnification side along an optical axis.

Abstract: Disclosed are a projection lens that has a simple inner focus structure, an appropriate back focal length, telecentricity, a high optical performance, and a small size and can effectively correct, particularly, lateral chromatic aberration, and a projection display device. A projection lens includes a first lens group having a negative refractive power and a second lens group having a positive refractive power arranged in this order from a magnification side. A fifth lens arranged closest to a reduction side in the first lens group is moved along an optical axis to adjust focus, and at least two lenses are made of a material with anomalous dispersion capable of reducing chromatic aberration in a wide visible range.

Abstract: The present invention enables the manufacture of a trochoid pump having a crescent which has been considered theoretically impossible by employing an inner rotor of a trochoid pump. An inner rotor having a predetermined number N of teeth that is equal to or larger than 4 is formed in advance.

Abstract: In a zoom lens for projection, a lens group arranged farthest to the reduction side is fixed when the magnification of the zoom lens is changed, and is composed of a negative aspheric lens made of a plastic material having at least one aspheric surface and a positive lens. At least one positive lens arranged on the reduction side of a lens having the smallest effective diameter among lenses composing the zoom lens satisfies the following formula (1): ?a>80(here,(dn/dt)<0)??(1), where ?a: Abbe number of a material forming the at least one positive lens for d-line, and dn/dt: a change in the refractive index of the material forming the at least one positive lens for d-line when temperature changes from 20° C.

Abstract: A zoom lens for projection includes negative first group G1, positive second group G2, positive third group G3, negative fourth group G4, positive fifth group G5, and positive sixth group G6, arranged from the magnification side of the zoom lens. The reduction side of the zoom lens is telecentric. When the magnification is changed, the first group G1 and the sixth group G6 are fixed, and the second through fifth groups G2 through G5 move. The fourth group G4 is a negative lens having a concave surface facing the magnification side, and the fifth group G5 includes at least two positive lenses and at least two negative lenses. Further, the following formula (1) is satisfied: ?5.0?f4/fw??1.2??(1), where f4: the focal length of the fourth group; and fw: the focal length of the entire system of the zoom lens at a wide angle end.

Abstract: A projection lens consists of first and second les groups and a stop. The first lens group is formed of a negative lens. The second lens group is formed of three positive lenses and a negative lens. The stop is disposed between the first and second lens groups or in the second lens group. The first and second lens groups are arranged in order from a magnification side. The projection lens is telecentric on a reduction side. The projection lens is configured to satisfy the following conditional expressions (1) and (2): 1.0?f2h/f?5.0??(1) ?2.5?f1/f??0.8??(2) where f2h is a focal length of an aspheric lens of at least one of the first and second positive lenses of the second lens group, f is a focal length of the whole system, and f1 is a focal length of the first lens group.

Abstract: Disclosed are a projection lens that is faster than F1.95 and has a simple inner focus structure, a high optical performance, and a small size, and a projection display device. A projection lens includes a first lens group having a negative refractive power, a second lens group having a positive refractive power, and a third lens group having a positive refractive power arranged in this order from a magnification side. A fifth lens arranged closest to a reduction side in the first lens group is moved along an optical axis to adjust focus. The projection lens satisfies the following conditional expression: 0.2<DG12/f<0.8 where DG12 indicates a distance between the first lens group and the second lens group and f indicates the focal length of the entire lens system.

Abstract: A projection variable focus lens includes seven lenses. The seven lenses include first to seventh lenses in order from a magnification side. The first and second lenses are provided closest to the magnification side and have a negative composite refractive power. The third lens has a positive refractive power. The fifth lens has a negative refractive power. The sixth lens has a positive refractive power. The seventh lens has a positive refractive power. A reduction side of a lens system is telecentric. The seven lenses are classified into three or more lens groups. Three or less lens groups among the three or more lens groups are moved to change a focal length. When the focal length varies from a wide angle end to a telephoto end, at least the third lens is moved from the reduction side to the magnification side along an optical axis.

Abstract: An inexpensive projection variable focus lens includes six lenses and three or less lens groups which are moved when power varies, is telecentric, and is capable of effectively reducing all aberrations including astigmatism. Also, a projection display device includes the projection variable focus lens. The six lenses include a first lens provided closest to a magnification side and having a negative refractive power, and a second lens from the magnification side that has a positive refractive power. The reduction side of a lens system is telecentric. The six lenses are classified into three or more lens groups. Three or less of the three or more lens groups are moved to change a focal length. When the focal length varies from a wide angle end to a telephoto end, at least the second lens is moved from the reduction side to the magnification side along an optical axis.

Abstract: A projection zoom lens projects an optical image of rays, which are irradiated from a light source onto a light valve and are modulated by a predetermined image displayed on the light valve, onto a screen. The projection zoom lens includes a plurality of lens groups that is formed as a telecentric system on the reduction side thereof and includes at least two movable lens groups which are movable during zooming. In the projection zoom lens, the plurality of lens groups is arranged to include, in order from a magnification side, at least a first lens group and a second lens group. The first lens group has a negative refractive power, remains stationary during zooming, and performs focusing. The second lens group has a negative refractive power and remains stationary during zooming and focusing.

Abstract: The projecting zoom lens includes, sequentially from its magnification side, a negative first lens group, a positive second lens group, a negative third lens group, a positive fourth lens group, a positive or negative fifth lens group, and a positive six lens group, while the reduction side of the projecting zoom lens is formed as a telecentric system. When the power of the zoom lens is varied, the first lens group and sixth lens group are fixed, while the second to fifth lens groups move. In such power varying operation, the movement of the third lens group advances from the magnification side to the reduction side as the zoom lens goes from the wide angle end toward the tele end.

Abstract: A projection zoom lens device includes, in order from a magnification side, a negative first group G1 and positive second to fifth groups (G2 to G5) and is configured so that the second group G2, the third group G3, and the fourth group G4 are moved along an optical axis toward the magnification side during zooming from a wide-angle end state to a telephoto end state. Also, a lens L4, being closest to the magnification side, of the second group G2 is formed of a negative lens, and the fifth group G5 includes a single positive lens.