JPH0447685Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Field of Application] The present invention is used as an objective lens for an optical pickup, and relates to a lens unit consisting of a press lens and a lens support member that supports the press lens.

[Prior art]

FIG. 4 schematically shows the configuration of an optical pickup used in digital audio disc players and the like.

This optical pickup 10 is equipped with a laser diode 2 as a light source. A laser beam emitted from this laser diode 2 is sent to a prism 4 via a beam splitter 3a, a collimating lens 3b, and a quarter wavelength plate 3c. and,
The light is reflected by the prism 4 and further focused by the objective lens 5, forming a minute beam spot on the recording surface 1a of the optical disk 1. The beam reflected from the recording surface 1a returns via the objective lens 5, the prism 4, the quarter-wave plate 3c, and the collimating lens 3b, and is reflected at a right angle by the beam splitter 3a. The light is then detected by a photodiode 7 via a cylindrical lens 6. By detecting changes in the intensity of this reflected light, the presence or absence of pits P on the recording surface 1a is detected and information is read.

FIG. 3 shows a cross-sectional view of the lens unit 5 used as an objective lens in the optical pickup 10. Polished lenses 16, 17, and 18 made of glass are housed in a lens barrel 15 made of metal or the like. After these lenses 16, 17, and 18 are inserted into the lens barrel 15, they are positioned using a positioning ring 15a formed integrally with the lens barrel 15 and spacers 19a, 19b, and 19c that are separate from the lens barrel 15. It is fixed with adhesive or the like.

[Problems with conventional technology]

However, in the conventional lens unit 5, each lens 16, 17, 18 is a polished lens, and the outer peripheral surface thereof is formed to be smooth. The outer circumferential surface serves as a reference for positioning with respect to the inner circumferential surface of the lens barrel 15. Therefore, the outer periphery of each lens 16, 17, and 18 must be polished with high precision in order to minimize the deviation of the optical axis, which makes lens processing complicated.

Also, since there is some gap between the outer peripheral surface of each lens 16, 17, 18 and the inner surface of the lens barrel 15,
When each lens 16, 17, 18 is assembled into the lens barrel 15, the optical axis of each lens 16, 17, 18 is shifted. Correcting this deviation, each lens 16, 17, 1
In order to align the optical axes of the lens 8, extremely complicated adjustment work was required, such as centering each lens one by one, checking the alignment of the optical axes in turn, and then fixing the lenses.

The present invention has been made in view of the above-mentioned conventional problems, and it is an object of the present invention to provide a lens unit that allows easy alignment of the optical axes of each lens and reliable centering when a plurality of lenses are used in combination. The purpose is to

[Means to solve problems]

The present invention is a lens unit comprising a press lens formed of a glass material and a lens support member that supports the press lens, the press lens including a lens body having an optical surface,
Positioning grooves formed in a ring shape around the optical axis of the lens body and having a concave curved cross section are press-molded around each of the front and back surfaces of the lens body, leaving glass material on the outermost periphery, and The ring-shaped edge formed on the lens support member contacts the concave curved surface of each positioning groove on both the front and back surfaces of the press lens, and the concave curved surface and the edge form a circular line centered on the optical axis. This is characterized in that the press lens and the lens holding member are centered by coming into contact with each other.

[Effect]

In the above means, when a press lens is molded from a glass material or the like, the optical surface and the positioning groove around the optical surface are molded with high precision using a mold. Further, the peripheral portion of the positioning groove is left as a remaining portion.
On the other hand, a ring-shaped edge is formed on the lens support member, and by applying this edge to the inner curved surface of the positioning recess, the inner curved surface of the recess and the edge form a circular line centered on the optical axis. This results in contact, which allows the press lens and the lens support member to be centered. Therefore, by forming the positioning groove in the press lens with high accuracy relative to the lens optical axis, and by forming the edge in the lens holder into a shape close to a perfect circle,
It becomes possible to support the press lens with high precision by the lens support member without providing a high precision fitting structure on both the press lens and the lens support member.

〔Example〕

Embodiments of the present invention will be described below with reference to FIGS. 1 and 2.

FIG. 1 is a sectional view showing a press lens according to an embodiment of the present invention, and FIG. 2 is a sectional view showing a lens unit such as an objective lens combined with this press lens.

The press lens 20 shown in FIG. 1 is formed by pressing a glass material. This press lens 20 has a biconvex lens body 21 at its center (range of diameter α). Further, an annular positioning groove 22 is formed around the lens body 21.
(width β) is formed. This positioning groove 22
are formed on both the front and back surfaces of the press lens 20, and its cross-sectional shape is a concave curved surface. The positioning groove 22 is formed with high accuracy in circularity and concentricity around the optical axis of the lens body 21, and the concave curved shape is also formed with high accuracy by a mold. A flange 23 is formed on the outside of this positioning groove 22. This flange 23 is formed by a protruding portion of the remaining press material.

In the mold for pressing this press lens 20, the portion (range α and β in the figure) for forming the lens body 21 and the positioning groove 22 is formed with high precision. When pressing a glass material with a mold to form a lens, due to the viscosity peculiar to the glass material,
It is necessary to use a larger amount of material than the lens volume.
In the present invention, the remaining portion of the material protruding to the outside of the positioning groove 22 is not cut after press molding using the mold described above, but is left as the flange 23.

Next, a lens unit housing the press lens 20 will be explained with reference to FIG.

This lens unit is used as the objective lens 5 of the optical pickup 10 shown in FIG. The first lens (the one located at the bottom of the figure) and the second lens (the one located at the center) are the biconvex press lenses 20 shown in FIG.
The third lens (the one on the upper side of the figure) is a press lens 20a whose lens body 21a is a meniscus lens. This press lens 20
a is the same as the press lens 20, the lens body 2
1a, a positioning groove 2 having a concave cross section
2 is formed into a ring shape, and a flange 23 made of the remaining material is formed on the outside thereof.

The lens barrel 31 is made of metal or the like,
A positioning ring 31a is formed at its tip. The press lens 20a, which is the third lens, is
Positioning is achieved by the positioning groove 22 coming into contact with the edge of the ring 31a. In addition, a press lens 20a and a press lens 20 which is a second lens are provided.
A spacer 32a is provided between the two lenses, a spacer 32b is provided between the press lens 20 which is the second lens, and a press lens 20 which is the first lens, and a spacer 32c is provided below the first lens. It is being Each lens 20 and 20a is installed by fitting the positioning groove 22 into the edge of the spacer 32a, 32b, 32c.
The positioning groove 22 is formed with high precision around the optical axis of the lens bodies 21, 21a, that is, with high concentricity and circularity with respect to the optical axis, and with high precision in cross-sectional shape, so that the ring 31a and the spacers 32a, 32b are formed with high precision. , 32c come into contact with the inner curved surface of the positioning groove 22 in a circular line contact with the optical axis as the center, so that the optical axes of the lenses 20, 20a can be aligned with high precision.

Note that the outer peripheries of the spacers 32a, 32b, and 32c are fixed to the lens barrel 31 by adhesive or the like.

When the lens unit shown in FIG. 2 is used as the objective lens 5 of the optical pickup 10 shown in FIG. A beam spot is formed on surface 1a.

〔effect〕

As described above, according to the present invention, the following effects can be achieved.

(1) Since a positioning groove is provided around the lens part that has an optical surface, the positioning groove enables the positioning of each lens without making delicate optical axis adjustments. The optical axis can be aligned with high precision. Since no adjustment is required, the number of steps required to assemble the lens unit is reduced and molding can be done at low cost.

(2) By molding the positioning groove of the press lens with high precision and manufacturing the ring-shaped edge of the lens support member with high precision, both the press lens and the lens support member are provided with highly accurate uneven fitting parts. This makes it possible to accurately position and assemble both parts without any trouble.

(3) Glass materials have high viscosity, so it is difficult to form uneven positioning fitting parts with high precision. The positioning groove having a concave curved cross section can be easily formed with high precision by pressing a glass material. Moreover, by using this concave curved positioning groove, the press lens and the lens support member can be centered with high precision.

[Brief explanation of drawings]

1 and 2 show an embodiment of the present invention. FIG. 1 is a sectional view of a press lens, FIG. 2 is a sectional view of a lens unit incorporating the press lens of FIG. 1, and FIG. FIG. 3 is a sectional view of a lens unit using a conventional lens, and FIG. 4 is a configuration diagram showing an optical pickup as an example of how the lens is used. 20, 20a...Press lens, 21, 21a
... Lens body, 22 ... Positioning groove, 23 ...
Flange, 31, 32a to 32c...lens support member.

Claims (1)

[Scope of utility model registration request] A lens unit consisting of a press lens formed of a glass material and a lens support member that supports the press lens, wherein the press lens includes a lens body having an optical surface, and peripheries of each of the front and back surfaces of the lens body. A positioning groove formed in a ring shape with a concave curved cross section centered around the optical axis of the lens body is press-molded with glass material remaining on the outermost periphery, and a ring formed on the lens support member. The shaped edges contact the concave curved surfaces of the respective positioning grooves on both the front and back surfaces of the press lens, and the concave curved surfaces and the edges come into circular line contact with the optical axis as the center, so that the press lens and the lens A lens unit characterized in that the holding member and the lens unit are centered.