1727 results about "Abbe number" patented technology

The present invention provides single vision and multifocal lenses, as well as methods for their production, having a transverse chromatic aberration enabling provision of a lens the performance of which is equivalent to a refractive lens with a higher Abbe number.

A composite material (10) includes a resin (12), and first inorganic particles (11) dispersed in the resin and containing at least zirconium oxide. The composite material has a refractive index at the d line n_COMd of not less than 1.60 and an Abbe's number ν_COM of not less than 20, and satisfies a relationship n_COMd≧1.8−0.005 ν_COM. This composite material exhibits both a high refractive index and low dispersion in good balance, and has excellent workability. Accordingly, using this composite material makes it possible to realize a small optical component having favorable wavelength characteristics.

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>50

ν2≦30

where,

• • ν1 is an Abbe number of the first lens, and
  • ν2 is an Abbe number of the second lens.

An optical system comprises from the object side: a positive first lens element, a negative second lens element, a positive third lens element, a fourth lens element, and an aperture stop located between the object side of the optical system and the second lens element for controlling the brightness of the optical system. A radius of curvature R3 of a front surface of the second lens element satisfies the relation: −0.02 [1/mm]<1/R3<0.22 [1/mm], an Abbe number V2 of the second lens element is less than 40. A focal length of the fourth lens element is f4, a focal length of the optical system is f, they satisfy the relation: f/f4<0.1, at least one inflection point is formed on the rear surface of the fourth lens element.

A bright, small, and inexpensive imaging lens system is provided with a short total length that can provide more than a 30 degree viewing angle and whose aberrations are excellently corrected. The imaging lens includes, in order from an object side, a positive first lens with a convex surface facing the object side, an aperture stop provided on the object side or an image side of the first lens, a meniscus second lens with a concave surface facing the object side, and a meniscus third lens with a convex surface facing the object side. Furthermore, at least one of the first lens and the second lens includes an aspheric surface, and the third lens is a biaspheric lens. In addition, the second lens and the third lens have paraxial focal lengths whose signs are different. When v max and v min are the maximum Abbe number and the minimum Abbe number among the lenses, respectively, the condition, 1.25<v max/v min, is satisfied.

An optical element of which diffraction efficiency hardly varies with wavelength is provided by using an optical material satisfying the conditions that n_d>−6.667×10⁻³v^d+1.70 and θ_g,F≦−2×10⁻³ν_d+0.59 where n_d is a refractive index at d-line, ν_d is an Abbe number at the d-line, and θ_g,F is a second order dispersion at d-line, whereby diffraction efficiency is improved in any working visible wavelength region and more precise chromatic aberration correction is obtained.

An imaging lens is provided and includes, in order from the object side, a front group having a negative power, a stop, and a rear group having a positive power. The front group includes, in order from the object side, a first negative lens having a meniscus shape with a concave surface on an image side, a second negative lens, and a third positive lens. The rear group includes, in order from the object side, a fourth positive lens, a fifth negative lens having a meniscus shape with a concave surface on the object side, and a sixth positive lens. An Abbe number of each of the first lens, the second lens, the fourth lens, and the sixth lens at the d-line is equal to or larger than 40, and an Abbe number of each of the third lens and the fifth lens at the d-line is equal to or smaller than 40. Each lens constituting the front group and the rear group is a single lens.

The object is to provide a polycarbonate copolymer having excellent mechanical strength, good heat resistance, a low refractive index, a large Abbe number, a low berefringence and excellent transparency and containing a plant-derived raw material. Disclosed is a polycarbonate copolymer which comprises a constituent unit derived from a dihydroxy compound represented by the general formula (1) and a constituent unit derived from an alicyclic dihydroxy compound and has an Abbe number of 50 or greater and “a 5% heating weight loss temperature” (a temperature at which the 5% weight loss under heating is observed) of 340° C. or higher. Also disclosed is a process for producing the polycarbonate copolymer by reacting a dihydroxy compound represented by the general formula (1) and an alicyclic dihydroxy compound with a carbonate diester in the presence of a polymerization catalyst.

An image pickup lens relating to the present invention is a lens for forming an image of a subject onto a photoelectric converter of a solid-state image pickup element. The image pickup lens includes, in order from an object side thereof: an aperture stop; a first lens with a positive refractive power; a second lens in a meniscus shape with a negative refractive power, whose object side surface is a convex surface; a third lens with a positive refractive power; and a fourth lens with a negative refractive power. The image pickup lens satisfies a predetermined conditions relating to a curvature radius of the object side surface of the second lens and an Abbe number of the second lens.

When a glass melt of an optical glass having a refractive index (nd) of at least 1.7 and an Abbe number (νd) of 28 to 41 is flowed down from a flow pipe made of Pt or a Pt alloy to form glass gobs continuously, there is caused a problem that the glass gobs have striae or that the weight variability among the glass gobs is large, and the problem can be overcome by the use of an optical glass comprising silicon oxide and boron oxide, the ratio of a content of the silicon oxide to a content of the boron oxide being greater than 0.78, the optical glass having a contact angle of at least 40° to Pt or a Pt alloy at a predetermined temperature equivalent to, or higher than, its liquidus temperature or in a predetermined temperature range whose lower limit is equivalent to, or higher than, the liquidus temperature and having a sag temperature Ts of 580° C. or lower.

A projection optical system having a magnification side and a reduction side for forming a magnified image on a magnification side image surface conjugate with a reduction side conjugate image surface includes, arranged in order from the reduction side, a first imaging system including a plurality of lens elements and lens components and a second imaging system including a mirror having a concave, aspheric reflecting surface. An intermediate image is formed between the first imaging system and the second imaging system. The projection optical system satisfies specified conditions related to the travel of principal rays through the projection optical system and related to the Abbe number of a lens element having positive refractive power of the first imaging system. A projection display device includes the projection optical system and may include a light valve for modulating a light beam for projection on a screen.