JPH04372729A - Integrated optical element and integrated optical pickup - Google Patents

Abstract

PURPOSE:To miniaturize an optical pickup, to contrive the reduction in weight and cost and to reduce the change with the lapse of time by integrating each optical element of the optical pickup. CONSTITUTION:A photodetector 2, microprism 4 for which planar glasses 3 are combined and laser diode are integrally provided on a slicon substrate 1 are integrally provided. The microprism 4 is equipped with a halfmirror face, and the bottom face is equipped with a V groove grinding face 4b. A laser beam emitted from the laser diode is reflected on the halfmirror, for warded to an optical disk, a returning light reflected by the optical disk transmits through the halfmirror, transmits through the V groove grinding face 4b, and the photodetector is irradiated with the light. The returning light is split into two optical beams by the V groove grinding face 4b. A focusing error is detected by an Foucault method using the light splitting action of this V groove grinding face 4b.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an integrated optical pickup for optically reading information recorded on an optical disk and an integrated optical element used therein.

0002

2. Description of the Related Art FIG. 12 shows a conventional optical pickup. The laser light emitted from the laser diode 30 is separated into three light beams by the diffraction grating 31, passes through the hologram element 33, and is condensed by the objective lens 33 to focus on the signal surface of the optical disc 34. The return light reflected by 34 follows the same path and passes through objective lens 33 , and then is diffracted when passing through hologram element 32 , and the first-order light of the diffraction is detected by photodetector 35 . In this way, in the conventional optical pickup, the laser diode 30
, diffraction grating 31, hologram element 32, objective lens 33
, each optical element such as the photodetector 35 exists almost independently,
Each had its own structure to hold and adjust each optical element.

0003

[Problems to be Solved by the Invention] In the above-mentioned conventional optical pickup, each optical element exists independently and is held and adjusted independently, so there is a natural limit to the miniaturization and weight reduction of the optical pickup. . In addition, changes over time due to misalignment of each optical element are likely to occur, which is a problem in that reliability is reduced.

The present invention has been made in view of the above circumstances, and provides an integrated optical pickup that integrates various optical elements to reduce size, weight, and cost, and also provides an integrated optical pickup with little change over time and an integrated optical element used therein. The purpose is to provide.

[0005]

[Means for Solving the Problems] An integrated optical element according to claim 1 which solves the above problems comprises: a photodetector on a substrate; a microprism placed so as to cover the photodetector; and a laser diode that emits a laser beam toward the optical disk, and the microprism reflects the laser beam emitted from the laser diode toward the optical disk, and transmits the return light that is reflected on the optical disk surface and returns along the same path. The prism includes a half-mirror surface inside the prism and a V-groove polished surface that separates the returned light that has passed through this half-mirror surface into two, and the photodetector is located at the focal position of the returned light that has passed through this V-grooved polished surface. characterized by something. An integrated optical element according to a second aspect of the present invention includes a photodetector on a substrate, a microprism placed so as to cover the photodetector, and a laser diode that emits a laser beam toward the microprism. The micro prism is formed on the surface on which the laser light emitted from the laser diode enters, and is configured to divide the incident light into three parts.
A half mirror surface inside the prism that reflects the light that has passed through this diffraction grating surface toward the optical disk side and transmits the return light that is reflected on the optical disk surface and returns along the same path. The mirror includes a cylindrical grooved polished surface that generates astigmatism in the returned light that has passed through the mirror surface, and the photodetector is located at the focal point of the returned light that has passed through the cylindrical grooved polished surface. An integrated optical element according to a third aspect of the present invention includes a photodetector on a substrate, a microprism placed so as to cover the photodetector, and a laser diode that emits a laser beam toward the microprism. The micro prism has a diffraction grating surface formed on the surface on which the laser light emitted from the laser diode enters, which separates the incident light into three parts, and a diffraction grating surface that separates the incident light into three parts, and reflects the light transmitted through this diffraction grating surface toward the optical disk side. , a half-mirror surface inside the prism that transmits the return light that is reflected on the optical disk surface and returns along the same path, and a hologram surface that separates the return light that has passed through the half-mirror surface into two parts, The device is characterized by being located at the focal point of the returned light that has passed through this hologram surface. According to a fourth aspect of the present invention, an integrated optical pickup is constructed using the integrated optical element according to the first, second or third aspect.

[0006]

[Operation] In the integrated optical element according to claim 1, the laser light emitted from the laser diode is reflected by the half mirror surface of the micro prism and directed toward the optical disk, and the return light that is reflected by the optical disk and returns along the same path. The light passes through the half mirror, passes through the V-groove polished surface, and illuminates the photodetector. Since the V-groove polished surface separates the transmitted return light into two semicircular light beams by the two inclined surfaces forming the V-groove polished surface, the focusing error signal reflects the light separation effect of the V-groove polished surface. It can be detected using the Foucault method. Further, the tracking error signal can be detected by the push-pull method which also utilizes the light separation effect of the V-groove polished surface.

In the integrated optical element according to claim 2, the laser light emitted from the laser diode is transmitted through the diffraction grating surface on the side surface of the micro prism, separated into three light beams, and then reflected by the half mirror surface. The returned light, which is reflected by the optical disk and returns along the same path, passes through the half mirror, further passes through the cylindrical grooved polished surface, and illuminates the photodetector. Since this cylindrical groove polished surface generates astigmatism in the transmitted return light, the focusing error signal can be detected by an astigmatism method that utilizes the astigmatism effect of the cylindrical groove polished surface. Further, the tracking error signal can be detected by a three-beam method that utilizes the light separation effect of the diffraction grating surface.

In the integrated optical element according to claim 3, the laser light emitted from the laser diode passes through the diffraction grating surface on the side surface of the micro prism, is separated into three light beams, and is then reflected by the half mirror surface. The return light that travels toward the optical disk, is reflected by the optical disk, and returns along the same path is transmitted through the half mirror, then through the hologram surface,
Illuminate the photodetector. Since the returned light passing through the hologram surface is separated into two semicircular light beams, the focusing error signal can be detected by the Foucault method using the light separation effect of the hologram surface. Also,
The tracking error signal can be detected by a three-beam method that utilizes the light separation effect of the diffraction grating surface.

[0009]

Embodiments Hereinafter, embodiments of the present invention will be described with reference to FIGS. 1 to 11. 1 to 4 show an embodiment of an integrated optical element and an integrated optical pickup according to claim 1. Reference numeral 1 denotes a silicon substrate on which a wiring pattern is formed, a photodetector 2 is provided on this silicon substrate 1, and a microprism 4 with a flat glass 3 bonded to the lower surface thereof is arranged thereon. Further, a laser diode 6 is provided on the silicon substrate 1 via a heat sink 5. The micro prism 4 is formed by joining two triangular prisms to form a half mirror surface 4a, and includes a V-groove polished surface 4b formed by cutting out the center of the lower surface to form a V shape when viewed from the track traveling direction. ing. The photodetector 2 is located at the focal point of the returned light that has passed through the V-groove polished surface 4b. The photodetector 2 is a 4-split optical sensor consisting of four elements A, B, C, and D arranged in parallel as shown in FIG. Silicon substrate 1, photodetector 2
, flat glass 3, micro prism 4, heat sink 5, laser diode 6, etc. constitute an integrated optical element 7. This integrated optical element 7 has an objective lens 9 that focuses the light emitted from this integrated optical element 7 onto an optical disk 8.
Together with these components, an integrated optical pickup is constructed. An example of an integrated optical pickup using this integrated optical element 7 is shown in FIG. For example, actuator base 1
Four suspension wires 13, one end of which is fixed to a support base 15 provided in 1, are used in the focusing direction (vertical direction in the figure) and the tracking direction (direction perpendicular to the plane of the paper in the figure).
support so that it can be displaced. Although not shown in the drawings, focusing servo and tracking servo of the objective lens 9 can be controlled by, for example, providing a focusing coil and a tracking coil on the lens holder 10 side, and providing a magnetic circuit on the actuator base 11 for applying a magnetic field to the focusing coil and tracking coil. Make sure to do the following.

In the above-mentioned integrated optical pickup, the laser beam emitted from the laser diode 6 is reflected by the half mirror surface 4a of the micro prism 4 toward the optical disk 8, reflected by the optical disk 8, and returned along the same path. The returned light passes through the half mirror 4a and then through the V-groove polished surface 4b. When passing through this V-groove polished surface 4b, V
Since the refraction directions of the two inclined surfaces forming the grooved polished surface 4b are different, the returned light is separated into two semicircular light beams, and the photodetector 2 is separated into two semicircular light beams.
Or irradiate as in (c). In FIG. 3, (a) shows the case when the focus is too close, (b) shows the case when the focus is in focus, and (c) shows the case when the focus is too far. The photodetector 2 detects the two separated returned lights, and detects the focusing error signal using the Foucault method. Further, the tracking error signal is detected by a push-pull method. That is, focusing error signal (FE), tracking error signal (TE)
, the reproduced RF signal (RF) is as follows. FE=(A+D)-(B+C)...■TE=
(A+B)-(C+D)...■RF=A+B
+C+D…■

0011
] Next, an embodiment of the integrated optical element according to claim 2 is shown in FIGS.
It is shown in FIG. In the integrated optical element 17 of this embodiment, the micro prism 14 has a half mirror surface 14a like the micro prism 4 shown in FIGS. 1 and 2, but the lower surface has a V
Instead of the grooved polished surface, it has a cylindrical grooved polished surface 14b formed by cutting out an arc shape when viewed from a direction perpendicular to the track traveling direction, and a diffraction grating surface 14c is formed on the side surface on the laser diode 6 side. are doing. In addition, the photodetector 12
As shown in Figure 7, the diagonals of the square are A, B, C,
It consists of a 4-split optical sensor divided into four elements D, and two optical sensors E and F on the left and right sides of it. The silicon substrate 1, heat sink 5, laser diode 6, objective lens 9, etc. are the same as those of the integrated optical element shown in FIGS. 1 and 2, and are given the same reference numerals and description thereof will be omitted. Further, this integrated optical element 17 configures an integrated optical pickup as shown in FIG. 4, for example, as described above.

In the above-mentioned integrated optical pickup, the laser light emitted from the laser diode 6 passes through the diffraction grating surface 14c on the side surface of the microprism 14 and is separated into three light beams, which are then separated by the half mirror surface 14a. The returned light that is reflected toward the optical disk 8 side, reflected by the optical disk 8, and returned along the same path is reflected by the half mirror surface 14a.
The light passes through the cylindrical groove polished surface 14b and illuminates the photodetector 12. This cylindrical grooved polished surface 14b generates astigmatism in the transmitted return light, and a focusing error signal is detected by an astigmatism method that utilizes the astigmatic effect of the circularly grooved polished surface 14b. Further, the tracking error signal is detected by a three-beam method that utilizes the light separation effect of the diffraction grating surface 14c. That is, focusing error signal (FE), tracking error signal (TE
), the reproduced RF signal (RF) is as follows. FE=(A+C)-(B+D)...■TE=
E-F
…■RF=A+B+C+D
…■

An embodiment of the integrated optical element according to claim 3 will be described with reference to FIGS. 8 to 11. In this integrated optical element 27, the micro prism 24 is shown in FIGS.
It has a half mirror surface 24a and a diffraction grating surface 24c like the micro prism 14, but a hologram surface 24b is formed on the lower surface in place of the cylindrical groove polished surface 14b. As shown in FIG. 10, this hologram surface 24b has two circular shapes.
Two divided semicircular regions are provided with lattice patterns of different pitches. The dividing line is approximately parallel to the track traveling direction. In addition, as shown in FIG. 11, the photodetector 22 consists of a 4-split photosensor that divides a square into 4 elements A, B, C, and D using vertical and horizontal dividing lines, and 2 elements E and F on the left and right sides of the 4-split photosensor. It consists of a light sensor. Silicon substrate 1
, heat sink 5, laser diode 6, objective lens 9
etc. are similar to the integrated optical element shown in FIGS. 1 and 2,
The same reference numerals are used to omit the explanation. Further, this integrated optical element 27 also constitutes an integrated optical pickup as shown in FIG. 4, for example, as described above.

In the above-mentioned integrated optical pickup, the laser light emitted from the laser diode 6 passes through the diffraction grating surface 24c on the side surface of the micro prism 24, is separated into three light beams, and is then split into three light beams by the half mirror surface 24a. The return light that is reflected toward the optical disk 8 side, reflected by the optical disk 8, and returned along the same path is reflected by the half mirror surface 24a.
The three return lights that pass through the hologram surface 24b are separated into two semicircular light beams, so the photodetector 22
is irradiated as shown in FIG. The focusing error signal is detected by a double knife edge method that utilizes the light separation effect of the hologram surface 24b. Also, the tracking error signal is generated at the diffraction grating surface 2 as in the case of FIGS. 5 and 6.
It is detected by a three-beam method that utilizes the light separation effect of 4c. That is, focusing error signal (FE), tracking error signal (TE), reproduction RF signal (RF)
is as follows. FE=(A+C)-(B+D)...■TE=
E-F
…■RF=A+B+C+D
…■

[0015] In the embodiment, the flat glass 3
is preferably provided to define the distance between the V-groove polished surface, the cylindrical groove polished surface, or the hologram surface and the photodetector, but it does not necessarily have to be a flat glass.

[0016]

[Effects of the Invention] According to the present invention, the function of bending the laser beam emitted from the laser diode toward the optical disk side;
The structure integrates a microprism with a focusing error detection function and a tracking error detection function together with a laser diode and a photodetector on one substrate, so each optical element is integrated, making it smaller and lighter, and reducing costs. In addition, we were able to obtain an integrated optical pickup and an integrated optical element used therein that exhibit little change over time.

[Brief explanation of the drawing]

FIG. 1 is a front view showing an embodiment of an integrated optical element according to claim 1.

FIG. 2 is a side view of the integrated optical element of FIG. 1;

[Figure 3] Diagrams of the photodetector in the integrated optical element in Figure 1. Figure (A) shows when the focus is too close, Figure (B) shows when the focus is in focus, and Figure (C) shows when the focus is too far. In some cases, it is too much.

4 is a side view showing an example of an integrated optical pickup using the integrated optical element of FIG. 1. FIG.

FIG. 5 is a front view showing an embodiment of the integrated optical element according to claim 2.

FIG. 6 is a side view of the integrated optical element of FIG. 5;

FIG. 7 is a diagram of a photodetector in the integrated optical element of FIG. 5;

FIG. 8 is a front view showing an embodiment of the integrated optical element according to claim 3.

FIG. 9 is a side view of the integrated optical element of FIG. 8;

FIG. 10 is an enlarged cross-sectional view taken along the line A-A of the main part in FIG. 8;

FIG. 11 is a diagram of a photodetector in the integrated optical element of FIG. 8;

FIG. 12 is an optical system configuration diagram showing a conventional optical pickup.

[Explanation of symbols]

1 Silicon substrate (substrate) 2, 12, 22 Photodetector 3 Flat glass 4, 14, 24 Microprism 4a, 14a
, 24a Half mirror surface 4b V-groove polished surface 14b Cylindrical groove polished surface 24b Hologram surface 14c, 24c Diffraction grating surface 6
Laser diode 7, 17, 27 Integrated optical element 8
optical disk

Claims (4)

[Claims] 1. A photodetector on a substrate, a microprism placed to cover the photodetector, and a laser diode that emits a laser beam toward the microprism,
The micro prism includes a half mirror surface inside the prism that reflects the laser light emitted from the laser diode toward the optical disk, and transmits the return light that is reflected on the optical disk surface and returns along the same path. 1. An integrated optical element comprising a V-groove polished surface that separates transmitted return light into two parts, and wherein the photodetector is located at a focal point of the returned light transmitted through the V-groove polished surface. 2. A photodetector on a substrate, a microprism placed to cover the photodetector, and a laser diode that emits a laser beam toward the microprism,
The microprism has a diffraction grating surface formed on a surface onto which the laser light emitted from the laser diode is incident, which separates the incident light into three parts, and a diffraction grating surface that reflects the light transmitted through this diffraction grating surface toward the optical disk side. The prism also includes a half mirror surface inside the prism that transmits the return light that is reflected on the optical disk surface and returns along the same path, and a cylindrical groove polished surface that causes astigmatism in the return light that has passed through the half mirror surface.
The integrated optical element is characterized in that the photodetector is located at the focal point of the return light transmitted through the cylindrical groove polished surface. 3. A photodetector on a substrate, a microprism placed to cover the photodetector, and a laser diode that emits a laser beam toward the microprism,
The microprism has a diffraction grating surface formed on a surface onto which the laser light emitted from the laser diode is incident, which separates the incident light into three parts, and a diffraction grating surface that reflects the light transmitted through this diffraction grating surface toward the optical disk side. The prism also includes a half-mirror surface inside the prism that transmits the return light that is reflected on the optical disk surface and returns along the same path, and a hologram surface that separates the return light that has passed through the half-mirror surface into two parts. An integrated optical element characterized in that the detector is located at the focal point of the returned light that has passed through the hologram surface. 4. An integrated optical pickup using the integrated optical element according to claim 1, 2 or 3, wherein the laser beam emitted from the integrated optical element is focused by at least one focusing lens. focus on the optical disc,
The integrated optical pickup converts the information on the optical disc into an electrical signal by returning the reflected light to the integrated optical element and detecting it with the photodetector.