Abstract: A projection optical system and that includes a relatively small number of lenses and are able to cover a wide zooming range and a projector. A 1-2 lens group which is a focus lens group is constituted with a lens which includes a single positive lens having a convex surface to the reduction side, a lens which includes a single negative meniscus lens having a convex surface to an enlargement side, and a lens which includes a single negative lens, and the 1-2 lens group is moved at the time of focusing accompanying magnification change.

Abstract: A projection optical system includes a first lens unit adapted to make a enlargement-side imaging surface and an intermediate image conjugate with each other, a second lens unit adapted to make the intermediate image and a reduction-side imaging surface conjugate with each other. The first lens unit has positive power, and the second lens unit has negative power. Defining a focal distance of the first lens unit as fU1, a focal distance of the second lens unit as fU2, a total lens length of the first lens unit as LLU1, and a total lens length of the second lens unit as LLU2, the following expression (1) and expression (2) are satisfied. ?0.3<fU1/fU2<?0.005 ??(1) 0.5<LLU1/LLU2<0.

Abstract: An imaging lens system (imaging lens) having a focal length f is formed of a first lens group formed of three negative lenses and a single positive lens or a cemented lens and a second lens group having a positive focal length with the first lens group and the second lens group sequentially arranged from the enlargement side and employs the stereographic projection method that satisfies a condition of y=a·f·tan(?/2) (?: 1.8???2.2). The thus configured imaging lens system readily allows distortion to be reduced at each image height y and the degree of compression to be also reduced for sufficient resolution at the periphery.

Abstract: First through third lens groups constituting a projection zoom lens can be configured as a zoom lens of the type in which the first and second lens groups, for example, are moved when zooming, and the first lens group, for example, is moved when focusing. Further, by fulfilling the conditional formula (1), it is possible to achieve that the back focus is prevented from becoming too short, and the back focus is prevented from becoming too long while ensuring the sufficient space on the reduction side, and the lens diameter on the reduction side is prevented from becoming too large in the case of adopting a roughly telecentric configuration on the reduction side.

Abstract: A projector used a projection lens to enlarge and project image light generated by image generator. When it is assumed that the on-optical-axis position of a lens surface where the maximum of light ray passage ranges (effective diameter) is minimized in the projection lens is a minimum diameter position, a stop is provided on a lens shifted from the minimum diameter position toward the light exiting side. The lens on which the stop is provided is a lens (for example, fourth lens closest to minimum diameter position) that satisfies 0.8?1??2??1, where ?1 represents the light flux diameter on a surface where the on-axis light flux diameter is maximized, and ?2 is the diameter of the stop.

Abstract: A projector used a projection lens to enlarge and project image light generated by image generator. When it is assumed that the on-optical-axis position of a lens surface where the maximum of light ray passage ranges (effective diameter) is minimized in the projection lens is a minimum diameter position, a stop is provided on a lens shifted from the minimum diameter position toward the light exiting side. The lens on which the stop is provided is a lens (for example, fourth lens closest to minimum diameter position) that satisfies 0.8?1??2??1, where ?1 represents the light flux diameter on a surface where the on-axis light flux diameter is maximized, and ?2 is the diameter of the stop.

Abstract: The 1-2nd lens group is divided into three lens groups which move when focusing is performed during the magnification change. Even in a case in which the second optical group is formed of one mirror, it is possible for a primary image to contain appropriate aberration and to hereby reduce aberration of an image which is finally projected onto a screen through the second optical group.

Abstract: To provide a projection optical system that can cover a wide range of magnification changes with a focus lens group in which the number of constituted lenses is decreased, and a projector including the projection optical system. A 1-2nd lens group as the focus lens group includes an F1 lens group configured of one positive lens, an F2 lens group configured of one positive lens and one negative lens, and an F3 lens group configured of one negative lens. At least the F2 lens group is caused to move when focusing is performed in response to a magnification change.

Abstract: In a 1-2nd lens group, an aspherical resin lens is disposed on the outermost enlargement side, an enlargement-side fixed lens group (second fixed lens group) as a fixed group is disposed, a moving lens group, which move when focusing is performed in response to the magnification change, is disposed further on the reduction side from the second fixed lens group. Even in a case where the second optical group is configured of one mirror, it is possible for a primary image to have appropriate aberration and to hereby reduce aberration of an image which is finally projected onto a screen through the second optical group.

Abstract: In a 1-2nd lens group, a reduction-side fixed lens group (first fixed lens group) as a fixed group is disposed on the outermost reduction side, an enlargement-side fixed lens group (second fixed lens group) as a fixed group is disposed on the outermost enlargement side, moving lens groups (lens groups), which move when focusing is performed in response to a magnification change, are disposed between the fixed groups, and thereby it is possible to perform effective correction in order to suppress aberration fluctuation to be reduced. Even in a case where the second optical group is configured of one mirror, it is possible for a primary image to have appropriate aberration and to hereby reduce aberration for a good image which is finally projected onto a screen through the second optical group.

Abstract: A 1-2nd lens group includes two aspherical resin lenses, and thereby it is possible to perform effective correction in order to suppress aberration fluctuation to be reduced. At this time, a glass lens is disposed between the two lenses, and thereby it is possible to control an incident light angle to the resin lens and to reduce power of the resin lenses, and it is possible to prevent variations of shapes of the resin lens. Even in a case where the second optical group is configured of one mirror, it is possible for a primary image to have appropriate aberration and to hereby reduce aberration for a good image which is finally projected onto a screen through the second optical group.

Abstract: To provide a projection optical system that can cover a wide range of magnification changes with a focus lens group in which the number of constituted lenses is decreased, and a projector including the projection optical system. A 1-2nd lens group as the focus lens group includes an F1 lens group configured of one positive lens, an F2 lens group configured of one positive lens and one negative lens, and an F3 lens group configured of one negative lens. At least the F2 lens group is caused to move when focusing is performed in response to a magnification change.

Abstract: The 1-2nd lens group is divided into three lens groups which move when focusing is performed during the magnification change. Even in a case in which the second optical group is formed of one mirror, it is possible for a primary image to contain appropriate aberration and to hereby reduce aberration of an image which is finally projected onto a screen through the second optical group.

Abstract: In a 1-2nd lens group, a reduction-side fixed lens group (first fixed lens group) as a fixed group is disposed on the outermost reduction side, an enlargement-side fixed lens group (second fixed lens group) as a fixed group is disposed on the outermost enlargement side, moving lens groups (lens groups), which move when focusing is performed in response to a magnification change, are disposed between the fixed groups, and thereby it is possible to perform effective correction in order to suppress aberration fluctuation to be reduced. Even in a case where the second optical group is configured of one mirror, it is possible for a primary image to have appropriate aberration and to hereby reduce aberration for a good image which is finally projected onto a screen through the second optical group.

Abstract: A 1-2nd lens group includes two aspherical resin lenses, and thereby it is possible to perform effective correction in order to suppress aberration fluctuation to be reduced. At this time, a glass lens is disposed between the two lenses, and thereby it is possible to control an incident light angle to the resin lens and to reduce power of the resin lenses, and it is possible to prevent variations of shapes of the resin lens. Even in a case where the second optical group is configured of one mirror, it is possible for a primary image to have appropriate aberration and to hereby reduce aberration for a good image which is finally projected onto a screen through the second optical group.

Abstract: In a 1-2nd lens group, an aspherical resin lens is disposed on the outermost enlargement side, an enlargement-side fixed lens group (second fixed lens group) as a fixed group is disposed, a moving lens group, which move when focusing is performed in response to the magnification change, is disposed further on the reduction side from the second fixed lens group. Even in a case where the second optical group is configured of one mirror, it is possible for a primary image to have appropriate aberration and to hereby reduce aberration of an image which is finally projected onto a screen through the second optical group.

Abstract: The 1-2nd lens group is divided into three lens groups which move when focusing is performed during the magnification change. Even in a case in which the second optical group is formed of one mirror, it is possible for a primary image to contain appropriate aberration and to hereby reduce aberration of an image which is finally projected onto a screen through the second optical group.

Abstract: A projection lens includes, in order from an enlargement side, a first optical system, a second optical system, and a third optical system. At least a portion of an intermediate image is formed so as to overlap the second optical system.

Abstract: A projection zoom lens is formed of the following lens groups sequentially arranged from the high magnification side: a first lens group fixed at the time of zooming and having negative power; a second lens group moved along the optical axis at the time of zooming and having negative power; a third lens group moved at the time of zooming and having positive power; a fourth lens group moved at the time of zooming; and a fifth lens group fixed at the time of zooming and having positive power. When the total lens system operating at the wide angle end has a focal length Fw, and the first lens group has a focal length F1, the following conditional expression is satisfied. ?0.5<Fw/F1<?0.

Abstract: A proximity projection-type projector includes a housing; a dust-proof cover arranged on a top portion of the housing; and a projection unit arranged within the housing. The projection unit projects projection light though the dust-proof cover on the housing toward a screen disposed outside the housing. An anti-reflection film forms a light incident surface of the dust-proof cover.