JPH019922Y2 - - Google Patents

Description

[Detailed explanation of the invention] This invention relates to a hybrid lens that combines a glass lens and a synthetic resin lens.
In particular, the present invention relates to a hybrid lens suitable for optical pickups and laser collimators for reproducing video discs and compact discs.

Unlike spherical lenses, aspherical lenses are extremely difficult to polish, so with the exception of some special lenses, most of them are made from synthetic resins, which can be easily mass-produced. However, there are some drawbacks when using this synthetic resin aspherical lens in combination with a glass spherical lens. That is, in the past, each lens was held within a lens barrel with a predetermined space between them, making it difficult to align their optical axes and requiring a high level of skill. Furthermore, synthetic resin lenses are prone to deformation due to temperature changes, which causes aberrations and optical axis misalignment. Furthermore, since the synthetic resin lens is spatially arranged as described above, each of the aspherical surfaces on both sides is coated with magnesium fluoride, for example, to prevent contamination from moisture and chemical substances in the atmosphere and to keep the reflectance low. must be coated with a film such as On the other hand, when manufacturing molds,
Two highly sophisticated transfer surfaces corresponding to each aspherical surface are required, which is not desirable in terms of cost.

This idea was created in view of the above-mentioned drawbacks of the conventional technology.The purpose of this idea was to eliminate the need for adjustments such as optical axis alignment, to be highly mass-producible, and to achieve high performance.Moreover, it did not require a separate aperture diaphragm. The objective is to provide a hybrid lens that does not

Hereinafter, this invention will be described in detail with reference to embodiments shown in the accompanying drawings.

As shown in FIG. 1, this hybrid lens 1 includes a first lens 2 made of glass.
and a second lens 3 made of synthetic resin that is integrally joined to one lens surface of the first lens 2 by injection molding. The first lens 2 is a biconvex spherical lens, and an annular groove 5 having a V-shaped cross section is formed approximately in the center of the edge surface (outer peripheral surface) 4 thereof. In this idea,
The groove 5 is used as a means for attaching the second lens 3, and also acts as an aperture stop that defines an effective luminous flux. Therefore, it is more preferable to give the wall surface of the groove 5 a satin finish or a grain finish that prevents the passage of light rays. Note that this first lens 2 may be a concave lens. On the other hand, the second lens 3 is
It is an aspherical lens made of polymethyl methacrylate, which has good transparency and is easy to mold. This second lens 3 is injection molded in a mold that will be described later.
In this case, the second lens 3 is integrally molded with a cylindrical body 6 that surrounds the edge surface 4 of the first lens 2. That is, at one end of this cylindrical body 6, there is an engaging protrusion 6a having a V-shaped cross section that fits into the groove 5, and a position in the optical axis direction when this hybrid lens 1 is attached to a lens barrel (not shown). A flange 6b is provided for regulating the flange 6b. The other end of the cylindrical body 6 is a hood portion 6c that extends further forward than the second lens 3 (rightward in FIG. 1) and protects the lens surface.

To manufacture this hybrid lens 1, molds 10 and 11 having a two-piece structure as illustrated in FIG. 2 are used. That is, one mold 10 is formed with a spherical recess 12 that receives the other lens surface side of the first lens 2.
A through hole 13 connected to a vacuum pump (not shown) is bored in the center of its bottom. In this embodiment, a groove 1 is provided at the corner of the recess 12 to allow the ridge between the lens surface of the first lens 2 and the edge surface 4 to escape.
4 is formed in a ring shape. The other mold 11 has a transfer surface 15 for forming the second lens 3 between it and one lens surface of the first lens 2.
and a female surface 16 for forming the cylindrical body 6 having the above-described shape together with the second lens 3. The mold 11 also has the transfer surface 15.
A sprue 17 and a runner 18 for injecting molten synthetic resin into the cavity formed between the female mold surface 16 and the first lens 2 are bored.

In the above configuration, the first lens 2 is attached after applying a buffering agent, preferably a silicone type, into the recess 12 of one of the molds 10, and a vacuum pump (not shown) is operated to remove the first lens 2. Fix it. Then, the other mold 11 is closed, a molten resin such as polymethyl methacrylate is injected into the cavity through the sprue 17 and the runner 18, and a predetermined cooling time is allowed to form the first mold made of glass. A second lens 3 made of synthetic resin is integrally bonded to the lens 2, and a groove 5
Hybrid lens 1 with an aperture stop of
is obtained.

As illustrated in FIG. 3, the peripheral area 3a of the lens surface of the second lens 3 is treated with satin finish or grain to prevent the passage of light rays, or painted with an appropriate color to form an aperture diaphragm. can also be formed.

As is clear from the above description of the embodiment, according to this invention, the first lens 2 made of glass
On the other hand, since the second lens 3 made of synthetic resin is integrally bonded, there is no need for an adjustment process to align the optical axes of those lenses, and there is a risk that the optical axes may be deviated due to the structure. There are hardly any. In this case, the groove 5 provided on the edge surface 4 of the first lens 2 not only functions as a means for securing the second lens 3, but also functions as an aperture diaphragm. A separate aperture ring is no longer required. Further, by being in close contact with a glass lens having high thermal conductivity, the thermal resistance of the synthetic resin lens is alleviated, and thermal deformation due to temperature changes is suppressed as much as possible. Furthermore, since the lens surface of the glass lens is used as the mold surface, only one sophisticated mold transfer surface is required to form the aspherical lens, which is extremely advantageous in mold production. In addition, since only one side of the synthetic resin surface is exposed to the outside, there is an advantage that there are fewer problems with reflection efficiency and cloudiness.

[Brief explanation of the drawing]

FIG. 1 is a vertical sectional view showing an embodiment of the hybrid lens of this invention, FIG. 2 is a sectional view illustrating the mold structure used for manufacturing the hybrid lens shown in FIG. 1, FIG. 3 is a sectional view showing a modified embodiment of this invention. In the figure, 1 is a hybrid lens, 2 is a first lens, 3 is a second lens, 5 is a groove, 6 is a cylindrical body, and 10 and 11 are molds.

Claims (1)

[Claims for Utility Model Registration] (1) A hybrid lens in which a first lens made of glass and a second lens made of synthetic resin are integrally joined by injection molding; A cylindrical body surrounding the edge surface of the first lens is integrally molded in the lens, and the cylindrical body is attached to the edge surface of the first lens and serves as an aperture diaphragm for defining an effective luminous flux. A hybrid lens characterized by an annular working groove. (2) The hybrid lens according to claim (1), characterized in that the wall surface of the groove is provided with a satin finish that prevents the passage of light rays.