78results about How to "Back focal length" patented technology

There is provided an image pickup lens having a 6-element structure which has a small size and a sufficiently lens speed of F / 2 or less and in which various aberrations are corrected favorably. This image pickup lens includes a first lens having a positive refractive power and comprising a convex surface directed to the object side; a second lens having a negative refractive power and comprising a concave surface directed to the image side; a third lens having a positive or negative refractive power; a fourth lens having a positive refractive power; a fifth lens having a positive refractive power and comprising a convex surface directed to the image side; and a sixth lens having a negative refractive power and comprising a concave surface directed to the image side, in this order from the object side, wherein the image side surface of the sixth lens has an aspherical shape and an inflection point at a position other than an intersection point with the optical axis, and the image pickup lens satisfies the following conditional expressions.ν1>50ν2≦30where,ν1 is an Abbe number of the first lens, andν2 is an Abbe number of the second lens.

In an objective lens for an endoscope, the full angle of view exceeds 120 degrees, and a most-object-side surface of the objective lens is spherical. Further, the following condition formulas (1) and (2) are satisfied:0.7<θ8 / θ10<0.8  (1); and5<R1 / f<15  (2),where θ10: half angle of view corresponding to a maximum image height;θ8: half angle of view corresponding to an image height that is 80% of the maximum image height;R1: curvature radius of the most-object-side surface; andf: focal length of the entire system of the objective lens.

An image pickup lens having a four lens configuration in which a bi-concave first lens, a bi-convex second lens, a bi-concave third lens, and a positive fourth lens are disposed in this order from an object side. Here, at least one of the first, second, third, and fourth lenses has an aspherical surface on each side. The image pickup lens satisfies Conditional Expression (1) given below when a refractive index of the second lens with respect to d-line is taken as Nd2. 1.6<Nd2  (1)

A far-infrared camera includes three lenses formed of ZnS. A first lens is a biconvex lens, a second lens is a negative meniscus or biconcave lens, and a third lens is a positive meniscus lens. A diffraction surface is formed in either surface of a lens. When a total focal distance f of the lens system is 10 mm to 30 mm and a focal distance f12 of the first and second lenses is 20 mm to 70 mm, 1≦f12 / f≦3.

To allow placement of optical members by providing a long back focus, make aberrations less subject to manufacturing errors, and reduce variations in aberrations during focusing. An endoscopic objective optical system includes, in order from an object side, a front group with negative refractive power, a focusing lens, and a rear group with positive refractive power, wherein: the endoscopic objective optical system satisfies conditional expressions (1) to (4) below:4<FB / FL  (1)FL / |Fc|<0.1  (2)−3<F—F / FL<−0.9  (3)2.5<F—R / FL<5  (4)where FB is back focus of the entire system, FL is a focal length of the entire system, fc is a focal length of the focusing lens, |fc| is an absolute value of fc, F_F is a focal length of the front group, and F_R is a focal length of the rear group.

A zoom lens includes, in order from an enlargement side to a reduction side, a first lens unit having a positive refractive power, which is stationary for variation of magnification, a second lens unit having a negative refractive power, which moves for variation of magnification, a third lens unit having a negative refractive power, which moves for variation of magnification, a fourth lens unit having a positive refractive power, which includes a stop and which moves for variation of magnification, and at least one lens unit. In the zoom lens, for variation of magnification from a wide-angle end to a telephoto end, the second lens unit and the third lens unit move towards the reduction side and the fourth lens unit move towards the enlargement side. The zoom lens satisfies an appropriate condition.

A variable-magnification projection optical system substantially consists of a negative first lens group that is disposed at the most enlargement-side position and is fixed during magnification change, a positive last lens group that is disposed at the most reduction-side position and is fixed during magnification change, and a plurality of lens groups that are disposed between the first lens group and last lens group and are moved during magnification change. The most enlargement-side lens group (the second lens group) of the lens groups that are moved during magnification change has a negative refractive power. Predetermined conditional expressions relating to a back focus of the entire system on the reduction side at the wide-angle end, a focal length of the entire system at the wide-angle end, a focal length of the second lens group and a focal length of the last lens group are satisfied.

A zoom lens with a reduced overall length having a color separating prism therein and a telecentric property with a first lens group (GI) having a positive refractive power and having a fixed position, a second lens group (GII) of the variable magnification type having a negative refractive power and having a position movable for magnification variation, a third lens group (GIII) having a positive refractive power and having a fixed position and a fourth lens group (GIV) having a positive refractive power and having a position variable for adjustment of a focal position upon magnification variation and upon focusing are disposed in order from an object side. At least one face of the two convex lenses in the fourth lens group is formed from an aspheric face.

An imaging lens formed of 4 lenses, in which a negative first lens having a meniscus shape with a convex surface on the object side, a biconvex positive second lens, a negative third lens having a concave surface on the image side, and a positive fourth lens having a convex surface on the object side, arranged in order from the object side, and the imaging lens satisfies conditional expressions (1): L12 / f<0.82; (2): 2.3<L12×R2F2 / f2<10.0; (5): −1.3<f1 / f<−0.9; and (6): 48<v1 simultaneously, where, L12 is the air equivalent distance between the first lens and the second lens, f is the focal length of the entire lens system, R2F is the radius of curvature of the object side lens surface of the second lens, f1 is the focal length of the first lens, and v1 is the Abbe number of the first lens with respect to the d-line.

The DLP projecting apparatus comprises multi digital micro lens devices. Said optic processing structure comprises: a spectrum architecture, a reflection architecture and a beam-combining architecture; the spectrum architecture uses the beam splitter and color wheel to splitting the beams; the reflection architecture comprises multi reflection prisms corresponding to said multi digital micro lens devices; the beam-combining architecture is composed of two triangle prisms.

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; andfw: the focal length of the entire system of the zoom lens at a wide angle end.

The present invention includes three or more lens groups. These are arranged in the order of a first lens group (11) that has positive refractive power and a second lens group (12) that has negative refractive power, as seen from the side having the longer conjugate distance, wherein a first lens (12a) of the lenses of the second lens group (12), as seen from the side having the longer conjugate distance, has positive refractive power. Thus, it is possible to suppress distortion aberration to a small value.

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):νa>80(here,(dn / dt)<0)  (1),where νa: Abbe number of a material forming the at least one positive lens for d-line, anddn / 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.

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.

A variable-magnification projection optical system substantially consists of a negative first lens group that is disposed at the most enlargement-side position and is fixed during magnification change, a positive last lens group that is disposed at the most reduction-side position and is fixed during magnification change, and a plurality of lens groups that are disposed between the first lens group and last lens group and are moved during magnification change. The lens groups that are moved during magnification change substantially consist of three lens groups, wherein the most enlargement-side lens group is a negative lens group. Predetermined conditional expressions relating to a back focus of the entire system on the reduction side at the wide-angle end, a focal length of the entire system at the wide-angle end, a focal length of the last lens group, and a focal length of the first lens group are satisfied.

The present invention provides a zoom lens that suppresses the generation of unnecessary light and is suitable for a projection lens. The zoom lens is used as a projection lens of a projector in which a prism is located between the projection lens and a spatial optical modulating element B. A lens closest to the spatial optical modulating element B is a meniscus positive lens whose convex surface faces a screen. A refractive index of the meniscus positive lens is 1.75 or more.

A variable magnification projection optical system substantially consisting of two lens groups of a first lens group having a positive refractive power and is moved during magnification change, and a second lens group having a positive refractive power and is moved during magnification change, in which the variable magnification projection optical system is configured such that the reduction side is telecentric.

A zoom lens with a reduced overall length having a color separating prism therein and a telecentric property with a first lens group (GI) having a positive refractive power and having a fixed position, a second lens group (GII) of the variable magnification type having a negative refractive power and having a position movable for magnification variation, a third lens group (GIII) having a positive refractive power and having a fixed position and a fourth lens group (GIV) having a positive refractive power and having a position variable for adjustment of a focal position upon magnification variation and upon focusing are disposed in order from an object side. At least one face of the two convex lenses in the fourth lens group is formed from an aspheric face.

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.

An inexpensive projection lens unit in a rear projection type image display system, having a short focal distance (wide angle of viewing field), high focus and high contrast, and as well, including a power lens made of a glass material having a high refractive index in a range from 1.63 to 1.70 and an Abbe's number of not less than 50 with an optimized incident and emergent configuration in order to satisfactorily correct aberration with a enhanced focusing performance even with a shortened focal distance. Further, the power lens having a high refractive index can exhibit a high power, and accordingly, can carry out satisfactory aberration correction by optimizing the aspheric degree of a plastic lens even though the length of back focus is increased for enhancing the contrast.

An optical lens and imaging equipment including the optical lens are disclosed. The optical lens can sequentially comprise a first lens, a second lens, a third lens, a fourth lens, a fifth lens and asixth lens from the object side to the image side along the optical axis. The first lens can have negative focal power, the object side surface of the first lens is a convex surface, and the image side surface of the first lens is a concave surface; the second lens can have positive focal power, the object side surface of the second lens is a concave surface, and the image side surface is a convexsurface; the third lens can have positive focal power, and the object side surface and the image side surface of the third lens are convex surfaces; the fourth lens can have positive focal power, andthe object side surface and the image side surface of the fourth lens are convex surfaces; the fifth lens can have negative focal power, and the object side surface and the image side surface of thefifth lens are concave surfaces; and the sixth lens can have positive focal power, and the object side surface and the image side surface of the sixth lens are convex surfaces. According to the optical lens provided by the invention, at least one of the beneficial effects of high resolution, miniaturization, small front-end aperture, large aperture, small CRA, low cost, long rear focal length andthe like can be realized.