JPH04216018A - Plastic lens and its molding die - Google Patents

Abstract

PURPOSE:To provide a plastic lens suitable for the use in an optical system composed of a plurality of components combined together in which eccentricity is not caused by the error of external dimension, unevenness, expansion and contraction. CONSTITUTION:The eccentricity is prevented and the center of a lens 1 can be in conformity with the optical axis by providing three elastic leaf spring- shaped sections 2 facing the outside in the radius direction of the lens 1 in the position equally dividing the outer peripheral section of a plastic lens 1 and pressing the leaf spring-shaped sections 2 to the inner face of a lens body 3 of an optical system to retain the lens 1.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention relates to a projection type television receiver,
The present invention relates to plastic lenses used in video cameras, etc., and molds for molding the lenses.

0002

2. Description of the Related Art In recent years, devices with optical systems such as projection television receivers, video cameras, and CD players have become widespread. BACKGROUND ART Plastic lenses, which have a high ability to correct aberrations due to their aspherical surfaces, are being put into practical use and becoming popular.

[0003] When constructing an optical system by combining a plurality of such plastic lenses and glass lenses,
A member called a lens barrel is used to appropriately space each lens element, and at the same time align the optical axes of each element. Conventionally, in order to align the optical axes, the lens barrel and lens element were each assembled with predetermined tolerances.

0004

[Problem to be Solved by the Invention] When such a method is used, play occurs between the lens barrel and the element depending on the precision and dispersion of finished dimensions of individual elements and lens barrels, and this causes optical axis misalignment. There was a problem in that it caused

Particularly in the case of plastic molded lenses, it is difficult to accurately predict the finished dimensions of the outer diameter, and in order to achieve high accuracy, the lens barrel must be modified based on the finished dimensions of the molded product, or The process was complicated as it required modification of the mold. Further, even if such a procedure is followed, it is necessary to set a loose tolerance that takes into account variations in the outer diameter due to variations in molding, and this has been the limit of optical axis accuracy. Furthermore, in the case of plastic, the coefficient of linear expansion is much larger than that of glass, so in order to prevent distortion within the operating temperature range, it is necessary to allow for a commensurate outer diameter margin, which is also important for optical axis precision. This was a factor that inhibited the

The present invention provides a plastic lens that can realize an optical system with excellent optical axis precision without causing eccentricity due to errors or variations in external dimensions or expansion and contraction, and a mold for making the plastic lens. The purpose is to provide.

[0007]

[Means for Solving the Problems] In order to achieve the above object, the plastic lens of the present invention is provided with at least three plate spring-shaped portions having elasticity toward the outside in the radial direction on the outer peripheral portion of the lens. In addition, in order to realize the above-mentioned plastic lens, the mold for molding a plastic lens of the present invention has a cavity side surface and a parting surface attached to one of a pair of members constituting the cavity side surface and the parting surface. A tapered notch extending over the parting surface is provided, and three or more convex portions are provided in a portion opposing the other notch, and a thin plate-like space is created on the side surface of the cavity with the parting surface closed. It is configured to form.

[0008]

[Function] By using the plastic lens described above, the optical axis can be maintained at the center without being affected by slight errors or variations in the outer diameter dimension, and it can also be held at the center due to expansion due to temperature changes.
Even if contraction occurs, the center can always be maintained and the optical axis will not shift.

[0009] Furthermore, by using the mold as described above, the plastic lens can be realized by adding a small amount of machining to an ordinary mold.

0010

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a plastic lens and a mold for molding a plastic lens according to the present invention will be described below with reference to the drawings.

FIGS. 1(a) and 1(b) are a top view and a front view showing an embodiment of the plastic lens of the present invention. In FIG. 1, 1 is a lens body, and 2 is a leaf spring-shaped portion, which has elasticity in the radial direction, and is provided at three equal intervals along the outer periphery.

FIG. 2 is a partial sectional view of the plastic lens shown in FIG. 1 assembled into a lens barrel. In FIG. 2, 3 is a lens barrel, and 4 is a presser frame.

As shown in FIG. 2, the leaf spring-shaped portion 2 is slightly bent to provide support in the lateral direction, and the direction of the optical axis is regulated by the peripheral flat portion, thereby maintaining an appropriate surface spacing. As shown in Fig. 1, the three leaf spring-shaped portions 2 are made of the same material and are evenly spaced, so that the lens is aligned between its outer diameter center and the inside of the lens barrel due to the balance of each elasticity. The centers of the circumferential surfaces are held to coincide with each other, and the optical axis does not shift. Furthermore, even if there are dimensional errors or variations in the outer diameter of the lens, there will be only a slight difference in the amount of deflection of the leaf spring-shaped portion, and eccentricity will not occur, and even if the leaf spring-shaped portion expands and contracts due to temperature, the leaf spring-shaped portion will still The center is maintained with only a slight change in the amount of deflection.

FIG. 3 shows a mold for molding a plastic lens according to an embodiment of the present invention, and FIG. 3(a)
, FIG. 3(b) shows a pair of members (hereinafter referred to as cavity blocks) 5 that constitute the cavity side surface and the parting surface.
FIG. 3 is a partial perspective view of the edge where the parting surface of , 6 and the side surface of the cavity intersect, with the parting surface facing upward.
(c) is a partial sectional view when a mold is constructed using this, and 7 and 8 are what are called optical inserts, and optical surfaces are formed on the surfaces thereof.

With this structure, a thin plate-like space can be formed on the side surface of the cavity 9 with an extremely simple mold structure, and at the same time as the lens body 1 is formed, the leaf spring shaped portion 2 can be formed on the side surface. can be formed. Although not shown in the figure, the thin plate-like spaces are formed at three equal locations on the side surface of the cavity, and are manufactured so that the elasticity of the leaf spring-shaped portions formed by molding is equal. .

[0016]

[Effect of the invention] As is clear from the above detailed explanation,
According to the plastic lens and the mold for molding the same according to the present invention, it is possible to easily realize an optical system with excellent optical axis precision without causing eccentricity due to errors or variations in outer diameter dimensions or expansion and contraction.

[Brief explanation of the drawing]

FIG. 1 (a) is a top view showing an embodiment of the plastic lens of the present invention; (b) is a front view showing an embodiment of the plastic lens of the present invention;

[Fig. 2] A partial cross-sectional view showing a state in which the plastic lens of the present invention is assembled into a lens barrel.

FIG. 3 (a) is a partial perspective view of the cavity block 5; (b) is a partial perspective view of the cavity block 6; (c) is a partial sectional view showing a mold for molding a plastic lens of the present invention;

[Explanation of symbols]

1 Lens body 2 Leaf spring shaped portions 5, 6 Cavity block (a pair of members forming the cavity side surface and the parting surface) 9 Cavity

Claims (2)

[Claims] 1. A plastic lens characterized in that at least three leaf spring-shaped portions having elasticity directed outward in the radial direction are provided at positions equally dividing the outer circumferential portion. 2. One of the pair of members constituting the cavity side surface and the parting surface is provided with a tapered notch extending between the cavity side surface and the parting surface, and the other member is provided with a convex portion opposing the notch. A mold for molding a plastic lens, characterized in that three or more parts are provided in each part, and a thin plate-like space is formed on the side surface of the cavity with the parting surface closed.