Abstract: A projection variable focusing lens and a projection display device that has a reduction side which is telecentric, a high magnifying power, a small size, a light weight, and a low manufacturing cost and is capable of correcting all aberrations occurring when power varies with good balance. A projection variable focusing lens that moves only one lens group when power varies includes a first negative lens group G1, a second positive lens group G2, a third lens group G3, and a fourth positive lens group G4 arranged in this order from a magnification side. When a focal length varies, only the second lens group G2 is moved along an optical axis X. During focusing, the third lens group G3 is moved along the optical axis X. A reduction side is substantially telecentric.

Abstract: A lens for projection substantially consists of a negative first-lens having a concave surface facing the reduction side, a positive second-lens having a convex surface facing the magnification side, a negative third-lens having a concave surface facing the magnification side, a positive fourth-lens having a convex surface facing the reduction side, and a positive fifth-lens, arranged in this order from the magnification side. Further, the following formulas (A) through (D) are satisfied: 1.2?Bf/f?2.5??(A); ?3.0?f3F/f??0.8??(B); 1.4?f5F/f5?8.5??(C); and 1.0?d12/f?2.7??(D), where Bf is a back focus, f is the focal length of an entire lens system, f3F is the focal length of a magnification-side surface of the third-lens, f5F is the focal length of a magnification-side surface of the fifth-lens, f5 is the focal length of the fifth-lens, and d12 is an air space between the first-lens and the second-lens.

Abstract: A negative first lens having a concave surface facing the reduction side of a lens for projection, a positive second lens having a convex surface facing the magnification side of the lens for projection, a negative third lens having a concave surface facing the magnification side, a positive fourth lens having a convex surface facing the reduction side, a positive fifth lens, and a positive sixth lens are arranged in this order from the magnification side, and the reduction side of the optical system is telecentric. Further, the following formula (A) is satisfied: 1.2?Bf/f?2.5??(A), where Bf: back focus in air of the entire lens system of the lens for projection, and f: focal length of the entire lens system.

Abstract: In constructing a lens for projection substantially consisting of seven lenses, and the reduction side of which is telecentric, a first-lens-group is composed of two lenses including at least one negative lens. A second-lens-group is composed of a positive second-group first-lens having a convex surface facing the magnification side, a negative second-group second-lens having a concave surface facing the magnification side, a positive second-group third-lens having a convex surface facing the reduction side, a positive second-group fourth-lens, and a positive second-group fifth-lens in this order from the magnification side. The formulas (A) and (B) are satisfied: 1.2?Bf/f?2.5??(A); and f23/f?1.5??(B), where Bf is a back focus in air of an entire lens system, f is the focal length of the entire lens system, and f23 is the focal length of an air lens between a reduction-side surface of the second-group second-lens and a magnification-side surface of the second-group third-lens.

Abstract: An objective lens for an endoscope is provided and has a lens group A and a lens group B that are movable in a direction of an optical axis. In the objective lens, first focal adjustment for observing a point between a most-distant point and an intermediate point is performed by moving the lens group A from a lens arrangement for observing the most-distant point; and second focal adjustment for observing a point between the intermediate point to a nearest point is performed by moving the lens group B from a lens arrangement for observing the intermediate point.

Abstract: A projection lens includes a first lens having at least an aspheric surface, a second lens having a concave surface facing the reduction side of the projection lens, and having negative refractive power, a third lens, a fourth lens, a fifth lens, a sixth lens having a convex surface facing the reduction side, and having positive refractive power, and the like, which are sequentially arranged from the magnification side of the projection lens. Further, the following formulas (1) and (2) are satisfied: 3.5<Bf/f<7.5??(1); and 1.2<|fa/f|<2.0??(2), where f: focal length of the entire system of the projection lens, Bf: back focus in air of the entire system, and fa: combined focal length of lenses from the second lens to a most-reduction-side lens.

Abstract: A projection lens is composed of a positive first lens group, a negative second lens group, and a positive third lens group, which are sequentially arranged from the magnification side of the projection lens, and the reduction side of the projection lens is telecentric. Further, the following formulas (1) and (2) are satisfied: 0.30?d23/f3?0.65??(1); and 10?|D12/ff|??(2), where d23: space in air between the second lens group and the third lens group, f3: focal length of the third lens group, D12: total length of the first lens group and the second lens group in the direction of an optical axis, and ff: length from the most magnification-side surface in the entire system of the projection lens to a magnification-side focus position of the entire system.

Abstract: A small projection lens includes a first lens, which is a biconvex lens, an aperture, an aperture diaphragm (or an aperture), a second lens, which is a negative meniscus lens having a concave surface facing a magnification side, a third lens, which is a positive meniscus lens having a convex surface facing a reduction side, and a fourth lens, which is a biconvex lens having aspheric surfaces at both sides on an optical axis, arranged in this order from the magnification side. A minimum portion of the length of all lens elements of the small projection lens in a diametric direction vertical to the optical axis is equal to or less than 15 mm, and the small projection lens satisfies the following conditional expression: 2.5<?/S<10.0 (where S indicates the maximum length of a magnification-side image (inch) and ? indicates a magnifying power).

Abstract: A projection optical system can achieve compactness and improve a state where polarized rays are separated by a polarized light separation section, without a separate optical system which makes the whole system telecentric, by using a reflective light valve. The projection optical system includes, in order, the reflective light valve, a projection lens and the polarized light separation section. The reflective light valve modulates incident illumination light in response to an input image signal and reflects and emits the modulated light. The projection lens transmits the illumination light incident to the reflective light valve and the modulated light emitted from the reflective light valve and is formed to be telecentric on the reduction side. The polarized light separation section separates the optical path of the illumination light incident to the projection lens from the optical path of the modulated light emitted from the projection lens.

Abstract: A capsule endoscope includes a capsule body having a cylindrical section, and a transparent cover. In the capsule endoscope, a reflective optical system, an image forming optical system, LEDs, and an image sensor are contained. The cylindrical transparent cover is disposed in the middle of the cylindrical section in a longitudinal direction. Through the transparent cover, light is transmittable in 360 degrees around a central axis of the capsule body. The reflective optical system reflects the light that has entered the capsule body through the transparent cover to the image forming optical system. The image forming optical system forms a 360 degree image around the whole circumference of the cylindrical section on the image sensor. The 360 degree image is circular in shape.

Abstract: An objective lens for an endoscope is provided and has a lens group A and a lens group B that are movable in a direction of an optical axis. In the objective lens, first focal adjustment for observing a point between a most-distant point and an intermediate point is performed by moving the lens group A from a lens arrangement for observing the most-distant point; and second focal adjustment for observing a point between the intermediate point to a nearest point is performed by moving the lens group B from a lens arrangement for observing the intermediate point.

Abstract: An objective lens for an endoscope is provided and has a lens group A and a lens group B that are movable in a direction of an optical axis. In the objective lens, first focal adjustment for observing a point between a most-distant point and an intermediate point is performed by moving the lens group A from a lens arrangement for observing the most-distant point; and second focal adjustment for observing a point between the intermediate point to a nearest point is performed by moving the lens group B from a lens arrangement for observing the intermediate point.

Abstract: The projection zoom lens system includes a negative first lens group, a positive second lens group, a third lens group, a positive fourth lens group, a fifth lens group, and a positive sixth lens group. The lens system is nearly telecentric on a reduction side. During zooming, the second to fifth lens groups are moved while the first and six lens groups remain stationary. The third lens group includes a positive lens LP having a convex surface directed to a magnification side, and a negative lens LN having a concave surface which is directed to the reduction side and has a curvature stronger than a magnification-side surface of the negative lens LN. The conditional expression of 5.0?|fG3/RLN-2| is satisfied. Here, fG3 denotes a focal length of the third lens group, and RLN-2 denotes a radius of curvature of the reduction-side surface of the negative lens LN.

Abstract: Disclosed is a single projection display device in which illumination light that is emitted from a light source unit and is linearly-polarized is reflected at a right angle by a PBS and is then incident on a single reflective liquid crystal display device, and modulated light passes through the PBS and is then projected onto a screen by a projection lens. An intersection point between the optical axis of the projection lens and the reflective liquid crystal display device deviates from the center of the surface of the reflective liquid crystal display device. The normal line of a polarized light separation plane is parallel to a plane that is vertical to another plane formed by a surface normal at the center of the surface of the reflective liquid crystal display device and the optical axis of the projection lens and that includes the optical axis of the projection lens.

Abstract: Linearly polarized illumination light that is emitted from a light source unit and then reaches a polarized light separation plane along the optical axis of an illumination optical unit is reflected from the polarized light separation plane at a right angle and reaches a reflection optical unit. The reflection optical unit reverses the phase of the linearly polarized illumination light and reflects the illumination light to the polarized light separation plane. The illumination light passes through the polarized light separation plane and reaches a reflective liquid crystal display device. The reflective liquid crystal display device converts the illumination light into modulated light having image information thereon. In this case, the phase of the linearly polarized light is reversed again and reflected from the polarized light separation plane at a right angle to reach a projection lens. The light is enlarged and projected onto a screen.

Abstract: A small projection lens includes a first lens, which is a biconvex lens, an aperture, an aperture diaphragm (or an aperture), a second lens, which is a negative meniscus lens having a concave surface facing a magnification side, a third lens, which is a positive meniscus lens having a convex surface facing a reduction side, and a fourth lens, which is a biconvex lens having aspheric surfaces at both sides on an optical axis, arranged in this order from the magnification side. A minimum portion of the length of all lens elements of the small projection lens in a diametric direction vertical to the optical axis is equal to or less than 15 mm, and the small projection lens satisfies the following conditional expression: 2.5<?/S<10.0 (where S indicates the maximum length of a magnification-side image (inch) and ? indicates a magnifying power).

Abstract: Disclosed is a projection variable focusing lens and a projection display device that has a reduction side which is telecentric, a high magnifying power, a small size, a light weight, and a low manufacturing cost and is capable of correcting all aberrations occurring when power varies with good balance. A projection variable focusing lens that moves only one lens group when power varies includes a first negative lens group G1, a second positive lens group G2, and a third positive lens group G3, arranged in this order from a magnification side. When a focal length varies, only the second lens group G2 is moved along an optical axis X. During focusing, the first lens group G1 is moved along the optical axis X. A reduction side is substantially telecentric.

Abstract: Disclosed is a projection variable focusing lens and a projection display device that has a reduction side which is telecentric, a high magnifying power, a small size, a light weight, and a low manufacturing cost and is capable of correcting all aberrations occurring when power varies with good balance. A projection variable focusing lens that moves only one lens group when power varies includes a first negative lens group G1, a second positive lens group G2, a third lens group G3, and a fourth positive lens group G4 arranged in this order from a magnification side. When a focal length varies, only the second lens group G2 is moved along an optical axis X. During focusing, the third lens group G3 is moved along the optical axis X. A reduction side is substantially telecentric.

Abstract: Color separation and synthesis systems, color separation systems and color synthesis systems, illumination optical systems, projection optical systems, and projection display devices using these systems include a wavelength-splitting element that reflects linearly polarized light of one wavelength and transmits light of another wavelength; a polarization-transforming element that changes the direction of polarization of linearly polarized light of one wavelength and that is arranged adjacent and at least nearly parallel to the wavelength-splitting element; and a polarization-sensitive beam splitter that reflects light having one direction of linear polarization and transmits light with another linear polarization.

Abstract: A reflection optical system placed between a light valve 5 and a screen 4, wherein curved surfaces are only three reflection surfaces of first to third mirrors 1 to 3, and satisfies the following: (1) ?L<20 degrees, (2) 25 degrees<?UL<55 degrees, (3) 20 degrees<?M1<55 degrees, (4) 15 degrees<?M2<50 degrees, (5) 8 degrees<?M3<30 degrees, (6) ?L<15 degrees, (7) 30 degrees<?UL and (8) 7.5 degrees<|?F|, where ?L: minimum angle which a light beam of pupil center forms with respect to the enlargement side image surface; ?UL: difference between maximum and minimum angles which a light beam of pupil center forms with respect to the enlargement side image surface; ?M1, ?M2 and ?M3: deviation angles of the light beam of pupil center passing the center of the reduction-side image surface in first to third mirrors 1 to 3; and ?F: reduction-side pupil divergent angle.