JP2507399Y2 - Pickup objective lens unit for optical disk - Google Patents

Description

[Detailed Description of the Invention] [Industrial field of application] The present invention, in order to improve the performance of a plastic lens or a glass embossed lens, achieves high precision, weight reduction, and size reduction in combination with a mounting device. For improvements.

[Prior art]

For plastic lenses, various proposals have been made for the purpose of simplification and high precision by providing a protrusion on the outside of the effective lens surface to form a lens surface protection and a mounting surface. For example, it is as described in Japanese Utility Model Laid-Open No. 55-167207, Japanese Patent Laid-Open No. 56-153301. The inventor of the present invention is June 29, 1984.
In the Japanese patent application plastic lens, as a means for effectively smoothing the surface coating of the lens, the shape of the protrusion outside the lens effective surface was improved. However, recently, the performance as a pickup objective lens for optical discs such as compact discs and video discs is required to be super-resolution and compact as well as super-resolution.

[Purpose of device]

It is an object of the present invention to further develop and improve the technology of the above patent application to provide an ultra-precision, lightweight and compact optical disc pickup objective lens unit.

[Constitution of device]

The purpose is to provide, on the outside of the convex lens surface on the light source side, a mounting fitting surface composed of a cylindrical surface concentric with the optical axis and an abutting surface connected to the fitting surface and perpendicular to the fitting surface. A biconvex single lens in which a projecting surface projecting to the optical disk side more than the convex lens surface on the optical disk side is integrally formed with the lens surface on the outside of the convex lens surface on the optical disk side, This is achieved by an optical disk pickup objective lens unit characterized in that the mounting mating surface and the protruding surface are mounted as mounting surfaces on a mounting device so that the optical disk surfaces face each other.

[Examples and functions]

FIG. 1 shows a sectional view of the lens 1 in the present invention. It is H, E, A, F, B, G, I, J, K outside the diameter d, d ′ of the effective lens surface.
Is provided with a projecting portion surrounded by each surface, and a mounting surface for mounting device 2 is provided with a fitting surface of A concentric with the optical axis and a flange surface of F perpendicular to the fitting surface on the other surface. For example, in the case of a plastic lens, it is possible to have an injection gate at one place on the B side, and on the H side and the K side, the outer surface is opened to complete the surface coating of the effective surface as already applied for a patent. It is a shaped surface, the effective surface is an aspherical surface, and the whole forms a high-performance single lens integrated with the same material. The lens 1 is attached to the lens mounting device 2 shown in FIGS. 1 and 2 to form the objective lens unit 3 in the pickup unit 8 of the optical disk device as shown in FIGS. 9 and 10. are doing. The pickup unit 8 is a device that accurately picks up the information pits 6 spirally arranged on the optical disc 5 as a digital amount by the objective lens unit 3.

The pickup unit 8 will be briefly described. The beam emitted from the semiconductor laser 10 passes through the diffraction grating 11 and the collimator lens 9 to become three parallel beams, passes through the semitransparent mirror 14 and the 1/4 wavelength plate 13, and then becomes the objective. The lens unit 3 captures the disc information signal, and the reflected light is passed through the cylindrical lens 12 for focus position detection and received by the light receiving element 15, and the objective lens unit 3 is made to automatically adjust the focus and prevent the tracking error of the information pit. While audio and video,
Alternatively, only the sound is reproduced.

On the other hand, the surface of the disk is also distorted, and if it is left as it is, the image plane for catching the pits is constantly changing. Further, the size of the pit is such that the depth is 0.1 μm, the length is several μm or less, and the width is 0.5 μm. Therefore, this lens must have an ultrafine resolution. Further, in order to cope with the fluctuation, a focusing coil is driven by a focus adjusting feedback signal from the light receiving element to cause the lens unit 3 to faithfully move through the slide guide 4 in a direction (Z).
Direction) must be followed at high speed.

In addition to this focus tracking in the optical axis direction, another important thing is that accurate automatic correction must be performed to prevent track tracking errors due to the eccentricity of the optical disk itself. Similarly to focusing, the tracking coil is driven by a feedback signal for track adjustment from the light receiving element, and the lens unit 3 is made to follow the radial direction (X direction) of the disc through the slide guide 4 ', while being finely corrected. It is necessary. For this reason, the lens unit must have a low inertia factor, and the outer peripheral portion must be as small as possible and light in weight.

Similarly, a desired information item on the track is selected, and a traverse operation is performed for random access to pick up the item quickly. This moves the entire pickup unit 8 in the disk radial direction (X direction).
The number of tracks stored in advance is accurately counted and jumping is performed, but in this case, super-high-speed tracking such as the focus adjustment is not required. In addition, the fact that the size of the objective lens unit 3 in the outer diameter direction is small eliminates the fear of interference with the disc loading table 7 as shown in FIG.
This is an important requirement because the information signal at the center of the disc can be reliably caught.

Next, the operation will be described as to why the surfaces A and F of the lens 1 are to be mounted on the mounting device 2 with high precision, light weight and small size. The accuracy of coupling the lens 1 with the mounting device 2 is determined by the length a of the fitting surface and the width b of the abutting surface if the processing accuracy is the same. If the F surface and the B surface, the E surface and the A surface, and the B surface and the G surface are set as the mounting surfaces without changing the effective surface diameter d, the outer diameter D, and the thickness of the present lens, respectively. As shown in FIG. 4, FIG. 5 and FIG. 6 and FIG. 7 and FIG. 8, comparing these with the present embodiment shown in FIG. 1 and FIG. It can be seen that the present embodiment, which uses the A-side and F-side mounting surfaces, has the smallest size and the same coupling accuracy. That is, the present embodiment has a simple cylindrical shape with the width dimension W = D and the thickness dimension T = a of the mounting device 2, whereas in the other three cases, W = D + 2b, T = a + b, and with a step. It has a cylindrical shape. Therefore, this implementation plan is highly accurate,
This brings about the effect of satisfying the requirements for a pickup lens that are lightweight and compact.

〔effect〕

According to the present invention, the mounting mating surface and the abutting surface, which are integrally formed on the lens, are mounted on the mounting device as the mounting surfaces. Since the protruding surface that protrudes toward the optical disk side more than the convex lens surface on the side is integrally formed with the lens, even if the lens and the optical disk collide with each other due to the warp of the optical disk substrate during the rotation of the optical disk,
Since it does not hit the lens surface and collides with the protruding surface, the lens surface is not damaged, and therefore it is possible to provide an optical disk pickup objective lens unit having excellent durability.

[Brief description of drawings]

FIG. 1 is a partial sectional view of an objective lens unit of the present invention when mounted on a mounting device, FIG. 2 is a top view thereof, and FIGS. 3, 5, and 7 show another surface of the lens mounting device. Partial sectional view of the objective lens unit when it is used as a mounting surface, FIG. 4, FIG. 6 and FIG. 8 are top views thereof, and FIG. 9 is a pickup incorporating the objective lens unit of the present invention. FIG. 10 is a plan view showing a schematic relationship between the unit and the disc. 1 ... Lens, 2 ... Mounting device A ... Mounting mating surface, F ... Mounting abutting surface (flange surface) D ... Lens outer diameter, d, d '... Lens effective surface outer diameter a ... Fitting surface length, b ... Width of abutting surface W ... Width dimension of mounting device T ... Thickness dimension of mounting device C ... Optical axis 3 ... Objective lens unit 4 ... Slide guide (Z direction) 4 '... Slide guide (X direction) 5 ... Optical disk, 6 ... Information pit 7 ... Disc loading base, 8 ... Pickup unit m ... Program area, n ... Catalog time recording area

Claims (1)

(57) [Scope of utility model registration request] 1. A mounting fitting surface composed of a cylindrical surface concentric with the optical axis and an abutting surface which is connected to the fitting surface and is perpendicular to the fitting surface are provided outside the convex lens surface on the light source side. A biconvex single lens formed on the outside of the convex lens surface on the optical disk side, the projection surface projecting to the optical disk side more than the convex lens surface on the optical disk side is integrally formed with the lens surface, An optical disk pickup objective lens unit, wherein the mounting mating surface and the abutting surface are mounted as mounting surfaces so that the optical disk surface and the optical disk surface face each other.