JPH05303063A - Spectacle lens for both far and near use - Google Patents

Abstract

PURPOSE:To decrease eye strain even in the case of gazing at a short distance object for many hours by superposing and forming a prism component which becomes gradually thicker toward a nose side, in an area being near the nose side from the optical center of a near use convex lens part. CONSTITUTION:A near use convex lens part 20 (l) consists of a downward semicircular convex lens, and is provided in a suitable in a suitable part of the lower half face of a far use convex lens 10. In the near use convex lens part 1, a prism component 1a which becomes gradually thicker toward a nose side from the optical center (c) is superposed and formed in an area being near the nose side from its optical center (c). That is, the prism component 1a has an apex angle corresponding to a prism action by the convex lens, consists of a convergence offsetting prism in which the gradient direction is reverse, and is installed between the reverse side of the near use convex lens part 1 and the surface of the far use convex lens 10. In such a way, an excessive convergence generated in the far use convex lens 10 can be offset by the prism component.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a bifocal spectacle lens for a hypermetropic person whose eyes do not get tired even when a near vision lens portion is used.

[0002]

2. Description of the Related Art Generally, a bifocal spectacle lens for a hypermetropic eye uses a distance convex lens 10 having a long focal length as a base,
A near convex lens portion 20 having a short focal length is provided at an appropriate place on the lower half surface, and when the far convex lens 10 is passed through, a distant object is imaged on the retina surface. Further, when the near-distance convex lens portion 20 is passed through, an object closer to the object is imaged on the retina surface than when the far-distance convex lens 10 is passed through. That is, when an object in front of several meters to several tens of meters is seen, the line of sight is almost straightened and corrected through the distance convex lens 10, and when looking at an object at hand of about several tens of centimeters, the line of sight is set slightly downward and near vision is used. Through the convex lens portion 20, it is possible to correct the vision.

[0003]

However, the above-mentioned conventional bifocal spectacle lens suffers from "convergence" (a light ray from an object moves left and right due to the prism effect of the lens) when the near convex lens portion 20 is used. There is a problem that eye fatigue easily occurs. This is the near lens part 20.
However, since the structure is closer to the nose side than the optical center of the distance lens, the prism action due to the change in the thickness of the distance lens portion is added when viewing from a near distance (Fig. 2 ( b)). That is, taking the optical center portion of the near lens portion 20 as an example, the light ray from the object is refracted to the outside (ear side of the eyeglass user) by this prism action. As a result, in order to see an object that is originally close to the face (for example, a book or a newspaper), both eyes must be turned inward, but the eyes must be moved further inward (nose side) (FIG. 3 (a)). In other words, in extreme terms, it is necessary to move the eyes to see an object placed on the tip of the nose, which increases fatigue.

On the other hand, a bifocal spectacle lens for a myopic person has a structure in which a concave lens is used as a base and a convex lens portion is provided on the concave lens as shown in FIG. Works in the opposite manner to those for hypermetropia, and it is less than the convergence with the naked eye (without glasses) during near vision, so the above problem does not occur.

In view of the above points, an object of the present invention is to provide a bifocal spectacle lens for a hypermetropic person who has almost no excessive convergence when viewing a near-distance object, and therefore has little eye fatigue. ..

[0006]

In order to achieve the above-mentioned object, the present invention provides a bifocal spectacle lens having a near convex lens portion at a lower half position of a distance convex lens surface. A prism component that becomes thicker toward the nose side is formed so as to overlap in a region closer to the nose side from the optical center so that the prism action provided by the distance convex lens and the near convex lens portion can be offset.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below based on an embodiment shown in the accompanying drawings. FIG. 1A is a front view of the left lens of the present application lens (as seen from the user side), and FIG. 1B is a front view of the right lens of the same. 2A is an explanatory view of a right lens of the bifocal spectacle lens of the present application in which a prism component for canceling the prism action of a convex lens is formed in superposition, and FIG. 2B is an explanatory view of a prism action of a conventional right lens that causes convergence. (A) is explanatory drawing which shows the convergence of the bifocal spectacle lens for hyperopic eyes, (b) is explanatory drawing which shows the vergence of the bifocal spectacle lens for myopia eyes.

In the drawing, reference numeral 1 denotes a near convex lens portion, which is similar to a conventional bifocal spectacle lens.
The lower half surface of the distance convex lens 10 is provided at an appropriate position. That is, the near convex lens unit 1 is composed of a downward semicircular convex lens, and its optical center c is located slightly below the optical center C of the distance convex lens 10 and is located at a position slightly closer to the nose side by a few mm. Has been done.

In the near convex lens portion 1, a prism component 1a having a thickness increasing from the optical center toward the nose side is formed in an overlapping manner in a region closer to the nose side from the optical center c. That is, as shown in FIG. 2A, the prism component 1a has a vertex angle corresponding to the prism action of a convex lens, and is composed of a convergence canceling prism whose gradient direction is opposite.
Is arranged between the back surface of the lens and the surface of the distance convex lens 10. In this case, the near convex lens 1 is slightly inclined with respect to the distance convex lens 10, but the inclination angle is extremely small, and the optical center c of the near convex lens 1 is slightly closer to the nose side. Therefore, the adverse effect of the inclination is negligible.

In this embodiment, the near convex lens portion 1 and the distance convex lens 10 are made of plastic, but it goes without saying that they may be made of another transparent material such as glass. It can also be applied to other types of multifocal lenses and progressive lenses.

In the above embodiment, when looking at a distant object, the object light corrected through the distance convex lens 10 is incident on the user's eye by directing the line of sight substantially in the front direction. Next, when looking at an object at a short distance, by making the line of sight slightly downward, the object light enters the eye through the near lens unit 1. At this time, since the object light that is originally bent to the ear side is bent and corrected to the nose side by the prism component 1a and enters the eye, the user of the spectacle lens does not need to be aware of the vergence effect of the lens.

[0012]

As described above, according to the present invention, in a bifocal spectacle lens having a near convex lens portion in the lower half of the distance convex lens surface, a region closer to the nose side from the optical center of the near convex lens portion. In addition, since the prism component having a thicker wall is superposed on the nose side, the excessive convergence generated in the distance convex lens can be offset by the prism component. As a result, it is possible to realize a bifocal spectacle lens that does not cause eye strain even when gazing at a short-distance object for a long time.

[Brief description of drawings]

1A is a front view of a left lens of the present invention lens (as viewed from a user side), and FIG. 1B is a front view of the left lens of the same.

2A is an explanatory view of the principle when a prism component for canceling the prism action of a convex lens is superimposed, and FIG. 2B is an explanatory diagram of the principle of the prism action that causes convergence.

FIG. 3A is an explanatory diagram showing the convergence of the lenses of the bifocal spectacles for hyperopia, and FIG. 3B is an explanatory view showing the convergence of the lenses of the bifocal spectacles for myopia.

[Explanation of symbols]

 1 near lens part of the present application lens 1a prism component 10 far lens 20 conventional near lens part C optical center of distance lens c optical center of near lens

Claims (1)

[Claims] 1. A bifocal spectacle lens comprising a near convex lens portion in a proper position on the lower half surface of the distance convex lens surface, in a region closer to the nose side from the optical center of the near convex lens portion, and flesh toward the nose side. A bifocal spectacle lens, wherein a prism component having a large thickness is formed in an overlapping manner.