JPH0560907A - Double focus lens - Google Patents

Abstract

PURPOSE:To provide the double focuses lens having a large diameter. CONSTITUTION:A liquid crystal 1 is held by two sheets of Fresnel lenses consisting of optical members, such as acryl or glass and the circumferential part thereof is coated with a seal 3. The lenses are rubbed in the circumferential direction to array the molecular axes of the liquid crystal in the circumferential direction. Since the liquid crystal varies in refractive index in the molecular axis direction and the direction perpendicular thereto, two focuses are generated by the polarized light in the circumferential direction and the polarized light in the perpendicular direction when natural light is made incident on this lens.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a bifocal lens applicable to spectacle lenses for presbyopia and the like.

[0002]

2. Description of the Related Art In a conventional spectacle lens for presbyopia, a distance portion and a near portion are positionally separated, and there is a limit to the width of each visual field.

As the contact lens and the artificial lens, for example, a bifocal lens using diffraction by a zone plate is known, as described in US Pat. No. 4,995,714.

[0004]

However, it is difficult to form a large lens such as a spectacle lens with a zone plate because the number of zones is large.

An object of the present invention is to provide a bifocal lens having a large diameter which can be easily manufactured.

[0006]

A bifocal lens according to the present invention for achieving the above object is characterized in that a rubbing Fresnel lens surface is in contact with a liquid crystal.

[0007]

In the bifocal lens having the above-described structure, the molecular axes of the liquid crystal are aligned by rubbing, and the liquid crystal has a different refractive index in the molecular axis direction and in the direction perpendicular to the molecular axis direction. When it does, it has different focal points in the polarization direction parallel to the molecular axis of the liquid crystal and the polarization direction perpendicular to it.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail based on the illustrated embodiments. FIG. 1 is a sectional view of the first embodiment, and FIG. 2 is a front view. A central liquid crystal 1 is sandwiched by two Fresnel lenses 2 made of an optical member such as acrylic or glass, and a circumferential portion is a seal 3. Is covered with. Further, rubbing is performed in the circumferential direction, and the molecular axes of the liquid crystal are aligned in the circumferential direction. Rubbing is generally difficult if there is unevenness, but there is no problem because the circumferential direction is parallel to the groove of the Fresnel lens 2.

If there is a difference in the refractive index between the liquid crystal 1 and the Fresnel lens 2, a refractive power is generated. However, since the liquid crystal has a different refractive index in the direction of the molecular axis and in the direction perpendicular thereto, when natural light is incident, as shown in FIG. It has different focal points in the circumferential and radial directions and functions as a bifocal lens.

FIG. 4 shows a second application of the present invention to a spectacle lens.
FIG. 6 is a cross-sectional view of the example of FIG. 3, in which a Fresnel liquid crystal lens 6 is provided between two lenses 4 and 5. The rubbing is performed in the circumferential direction as in the first embodiment. The peripheral portion 7 of the eyeglass lens is a liquid crystal lens 6 in consideration of lens processing.
Does not exist, and the lenses 4 and 5 are simply bonded together in this portion.

Also in this case, when natural light is incident, two focal points are generated as in the first embodiment.

FIGS. 5A and 5B are front views of two cylindrical Fresnel lenses 8 and 9 used in the third embodiment. When the concave and convex surfaces of the cylindrical Fresnel lenses 8 and 9 are faced to each other and the liquid crystal is sandwiched therebetween, and rubbing is performed in the direction along the groove near each boundary surface, the liquid crystal molecular axes on both sides become a TN type. ..

In this case, a bifocal lens having different focal points for longitudinally polarized light and laterally polarized light, and when combined with a cylindrical Fresnel lens having different refractive power, it becomes a lens for astigmatism.

A Fresnel lens may be in contact with one side of the liquid crystal and a flat optical member may be provided on the other side.

[0015]

As described above, the bifocal lens according to the present invention can be a relatively large lens and uses liquid crystal, but unlike a normal liquid crystal element,
Since neither electrodes nor polarizing plates are required, the structure is simple and the transmittance is high.
Further, if applied to a spectacle lens, it is possible to produce a spectacle lens having a wide field of view for both farsightedness and myopia.

[Brief description of drawings]

FIG. 1 is a sectional view of a first embodiment.

FIG. 2 is a front view.

FIG. 3 is an explanatory diagram of a transmitted light flux.

FIG. 4 is a sectional view of a second embodiment.

FIG. 5 is a front view of a cylindrical Fresnel lens used in a third embodiment.

[Explanation of symbols]

 1,6 Liquid crystal 2 Fresnel lens 3 Seal 4,5 Lens 8,9 Cylindrical Fresnel lens

Claims (1)

[Claims] 1. A bifocal lens having a structure in which a rubbed Fresnel lens surface is in contact with a liquid crystal.