Abstract: Lens aberration in an objective lens for recording and reproducing optical information, which is composed of a molded aspherical single lens, is inhibited while at the same time good lens productivity is attained. Also attained are excellent optical properties and high production efficiency in a mold processing step and a press molding step conducted to manufacture the lens. To this end there is provided an objective lens 1 having a convex aspherical surface formed at a first surface and a numerical aperture NA which satisfies the condition NA?0.8. It is preferable to have an aspherical surface also at the second surface.

Abstract: Lens aberration in an objective lens for recording and reproducing optical information, which is composed of a molded aspherical single lens, is inhibited while at the same time good lens productivity is attained. Also attained are excellent optical properties and high production efficiency in a mold processing step and a press molding step conducted to manufacture the lens. To this end there is provided an objective lens 1 having a convex aspherical surface formed at a first surface and a numerical aperture NA which satisfies the condition NA?0.8. It is preferable to have an aspherical surface also at the second surface.

Abstract: Lens aberration in an objective lens for recording and reproducing optical information, which is composed of a molded aspherical single lens, is inhibited while at the same time good lens productivity is attained. Also attained are excellent optical properties and high production efficiency in a mold processing step and a press molding step conducted to manufacture the lens. To this end there is provided an objective lens 1 having a convex aspherical surface formed at a first surface and a numerical aperture NA which satisfies the condition NA?0.8. It is preferable to have an aspherical surface also at the second surface.

Abstract: Theme To inhibit the lens aberration in an objective lens for recording and reproducing optical information, which is composed of a molded aspherical single lens, while attaining at the same time good lens productivity, and also to ensure excellent optical properties and to obtain a high production efficiency in a mold processing step and a press molding step conducted to manufacture the lens. Means for Solving the Problems An objective lens 1 is a lens wherein a convex aspherical surface is formed at the first surface and a numerical aperture NA satisfies the condition, NA?0.8. It is preferable to have an aspherical surface also at the second surface.

Abstract: The objective lens has a numerical aperture NA=0.6 when reproducing a DVD having a thickness of 0.6 mm and NA=0.42 when reproducing a CD having a thickness of 1.2 mm. At a boundary of NA 0.42, a slight stepped portion is formed so as to establish a phase difference. In this case, a designed wavelength is 0.635 .mu.m, and an optimum designed substrate thickness of a central portion is approximately 0.8 mm. While the DVD is reproduced, wave front aberration is on the order of 0.025.lambda., and jitter contained in the reproduction signal of the CD is equivalent to the present jitter. As a consequence, such an objective lens and an optical head with employment of this objective lens are provided, which precisely reproduce signals from the CD having the substrate thickness of 1.2 mm, and the DVD having the substrate thickness of 0.6 mm.

Abstract: In an optical lens system for use in combination with a bar code sensor, first and second meniscus lenses are arranged back to back along an optical axis on object and image sides, respectively, and are identical in configuration and optical charcteristics with each other. Each meniscus lens has effective aspherical surfaces defined by predetermined formulae. On the assumption that the first and the second meniscus lenses have the same refractive index, the optical lens system satisfies the following formulae:0.25<(r1/r2)/(n/(n-1))<0.5.1.2<f1/f<1.8,0.3<D/f<0.6, and1.