Abstract: There is provided a projection optical system capable of projecting an image formed on an image forming unit on a projection plane, which has an extremely short projection distance and a small size.

Abstract: A projection device to magnify and project, on a screen, an image displayed at an image display element, includes: a dioptric system including at least one positive lens and at least one negative lens; and a reflection optical system having at least one reflection optical element.

Abstract: There is provided a projection optical system capable of projecting an image formed on an image forming unit on a projection plane, which has an extremely short projection distance and a small size.

Abstract: A projection device to magnify and project, on a screen, an image displayed at an image display element, includes: a dioptric system including at least one positive lens and at least one negative lens; and a reflection optical system having at least one reflection optical element.

Abstract: A projection optical system comprises an image forming unit that forms an image; a refractive optical system including a plurality of lenses that enlarges and projects the image on a screen; and a reflecting surface, wherein an intermediate image is formed between the refractive optical system and the reflecting surface, and the projection optical system satisfies conditions of “0.6<D/Did<0.8” and “2.5<Did/F<6”, where “Did” represents a maximum paraxial image height of the intermediate image in a focusing state in which a projection image is maximum, “D” represents a maximum value of a distance between an optical axis and an intersection of a paraxial image surface and a light beam passing center of an aperture stop of the refractive optical system, and “F” represents a focal length of the refractive optical system in a focusing state in which the projection image is maximum.

Abstract: A projection device to magnify and project, on a screen, an image displayed at an image display element, includes: a dioptric system including at least one positive lens and at least one negative lens; and a reflection optical system having at least one reflection optical element.

Abstract: An optical system includes a reflective optical system on a magnification side along an optical path of the projection optical system and a refractive optical system on a reduction side along the optical path. The reflective optical system includes one reflective optical element having a power. The refractive optical system includes a front group on the magnification side and a rear group on the reduction side. The front group having, in order from the magnification side toward the reduction side, a first lens group with a positive or negative refractive power, a second lens group, and a third lens group with a positive refractive power. The rear group has a positive refractive power. The first lens group moves to the magnification side, and the second lens group and the third lens group move to the reduction side in a change in focus from a long distance to a short distance.

Abstract: An image display apparatus and an image display unit. The image display apparatus and the image display unit includes a light source configured to emit light, an illumination optical system including a luminous body forming device configured to form a secondary luminous body, the illumination optical system guiding the light emitted from the light source, an optical modulation element including a plurality of reflection planes to modulate the light guided by the illumination optical system, and a projection optical system including a projection lens system and a barrel storing the projection lens system, the projection optical system projecting the light modulated by the optical modulation element onto a projection plane. The barrel satisfies an equation ?<0.71H+8.5, where ? denotes an outside diameter of a front end of the barrel on a light entering side and H denotes distance between the reflection planes and the front end of the barrel.

Abstract: A projection device to magnify and project, on a screen, an image displayed at an image display element, includes: a dioptric system including at least one positive lens and at least one negative lens; and a reflection optical system having at least one reflection optical element.

Abstract: There is provided a projection optical system capable of projecting an image formed on an image forming unit on a projection plane, which has an extremely short projection distance and a small size.

Abstract: A projection optical system comprises an image forming unit that forms an image; a refractive optical system including a plurality of lenses that enlarges and projects the image on a screen; and a reflecting surface, wherein an intermediate image is formed between the refractive optical system and the reflecting surface, and the projection optical system satisfies conditions of “0.6<D/Did<0.8” and “2.5<Did/F<6”, where “Did” represents a maximum paraxial image height of the intermediate image in a focusing state in which a projection image is maximum, “D” represents a maximum value of a distance between an optical axis and an intersection of a paraxial image surface and a light beam passing center of an aperture stop of the refractive optical system, and “F” represents a focal length of the refractive optical system in a focusing state in which the projection image is maximum.

Abstract: There is provided a projection optical system capable of projecting an image formed on an image forming unit on a projection plane, which has an extremely short projection distance and a small size.

Abstract: A projection optical system comprises an image forming unit that forms an image; a refractive optical system including a plurality of lenses that enlarges and projects the image on a screen; and a reflecting surface, wherein an intermediate image is formed between the refractive optical system and the reflecting surface, and the projection optical system satisfies conditions of “0.6<D/Did<0.8” and “2.5<Did/F<6”, where “Did” represents a maximum paraxial image height of the intermediate image in a focusing state in which a projection image is maximum, “D” represents a maximum value of a distance between an optical axis and an intersection of a paraxial image surface and a light beam passing center of an aperture stop of the refractive optical system, and “F” represents a focal length of the refractive optical system in a focusing state in which the projection image is maximum.

Abstract: A projection device to magnify and project, on a screen, an image displayed at an image display element, includes: a dioptric system including at least one positive lens and at least one negative lens; and a reflection optical system having at least one reflection optical element.

Abstract: A zoom lens includes, in order from an object side in an optical axis a first lens group having a positive refractive power, a second lens group having a negative refractive power; a third lens group having a negative refractive power, a fourth lens group having a positive refractive power, a fifth lens group having a positive refractive power, and an aperture stop arranged between the third lens group and the fourth lens group, an interval between the first lens group and the second lens group being increased, an interval between the second lens group and the third lens group being varied, an interval between the third lens group and the fourth lens group being decreased, and an interval between the fourth lens group and the fifth lens group being decreased when changing a magnification from a wide-angle end to a telephoto end.

Abstract: A zoom lens includes, in order from an object side to an image side along an optical axis, a first lens group having a positive refractive power, a second lens group having a negative refractive power, a third lens group having a negative refractive power, a fourth lens group having a positive refractive power, and a fifth lens group having a positive refractive power.

Abstract: There is provided a projection optical system capable of projecting an image formed on an image forming unit on a projection plane, which has an extremely short projection distance and a small size.

Abstract: A zoom lens includes, in order from an object side along an optical axis, a first lens group having a positive refractive power, a second lens group having a negative refractive power, a third lens group having a negative refractive power, a fourth lens group having a positive refractive power, and a fifth lens group having a positive refractive power, wherein with a change in a magnification from a wide-angle end to a telephoto end, an interval between the first lens group and the second lens group is increased, the interval between the second lens group and the third lens group is changed, the interval between the third lens group and the fourth lens group is decreased, the interval between the fourth lens group and the fifth lens group is decreased, and focusing is performed by the third lens group.

Abstract: A projection optical system comprises an image forming unit that forms an image; a refractive optical system including a plurality of lenses that enlarges and projects the image on a screen; and a reflecting surface, wherein an intermediate image is formed between the refractive optical system and the reflecting surface, and the projection optical system satisfies conditions of “0.6<D/Did<0.8” and “2.5<Did/F<6”, where “Did” represents a maximum paraxial image height of the intermediate image in a focusing state in which a projection image is maximum, “D” represents a maximum value of a distance between an optical axis and an intersection of a paraxial image surface and a light beam passing center of an aperture stop of the refractive optical system, and “F” represents a focal length of the refractive optical system in a focusing state in which the projection image is maximum.

Abstract: A zoom lens includes, in order from an object side in an optical axis a first lens group having a positive refractive power, a second lens group having a negative refractive power; a third lens group having a negative refractive power, a fourth lens group having a positive refractive power, a fifth lens group having a positive refractive power, and an aperture stop arranged between the third lens group and the fourth lens group, an interval between the first lens group and the second lens group being increased, an interval between the second lens group and the third lens group being varied, an interval between the third lens group and the fourth lens group being decreased, and an interval between the fourth lens group and the fifth lens group being decreased when changing a magnification from a wide-angle end to a telephoto end.