JPS62117150A - Optical pickup - Google Patents

Abstract

PURPOSE:To miniaturize the entire optical pickup and to make the profile thin by mounting optical elements such as a light emitting element, a light receiving element and a lens at both sides of a transparent board. CONSTITUTION:A laternal line shows a light lighted by a light emitting element 1a such as a laser diode, a longitudinal line indicates a light reflected from the recording face of a disc D the these lights trace a path reflected in the front and rear sides of the board in the transparent board 51 and propagated. In order to form the optical path, total reflection faces A1-A3 and a semi- reflection face B are formed on both sides of the transparent board 51, and the total reflection faces A1-A3 and the semi-reflection face B are formed by vapor-depositioning the poly-layer film of a conductor such as SiO2 or TiO2. The total reflection faces A1-A3 and the semi-reflection face B are formed separately by controlling the thickness of the poly-layer film made of a dielectric. The light emitting element 1a such as a laser diode is fixed on the semi- reflection face B and a diffraction grating 52 is formed between the light emitting element 1a and the semi-reflection face B.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field] The present invention relates to an optical pickup such as a big amplifier for a compact disk or a pickup for a magneto-optical disk memory.

[Prior art and its problems]

FIG. 5 shows the configuration of an optical pickup installed in a conventional compact disc player.

In this type of optical pickup, a laser diode 1 is provided as a light emitting element within a moving member that moves in the radial direction of the disk D. Laser light emitted from this laser diode 1 passes through a beam splitter 2 and is converted into parallel light by a collimating lens 3. So[
7, the 174 waves are transmitted through a plate, etc., are reflected by the prism 4 in the right angle direction, and are reflected by the objective lens 5 into the disk D.
The light is focused on the recording surface. One of the reflected beams returns to its original path, but since one reflected beam passes through the 1/4 wavelength twice and its plane of polarization is changed, it is reflected by the beam splitter 2 in a perpendicular direction. The light then passes through the concave lens 6 and the cylindrical lens 7, and is received by the photodiode 8, which is a light receiving element. This photodiode 8 reads information on the recording surface of the disc D.

Further, the objective lens 5 is held by a correction drive device 9 of a magnetic drive type, and the objective lens 5 is driven by the correction drive device 9, so that the light from the objective lens 5 is accurately irradiated onto the recording surface of the disk D. It is corrected so that

FIG. 7 shows the configuration of a conventional optical pickup for a magneto-optical disk memory.

The reference numeral indicates a disk for magneto-optical memory, and M indicates an electromagnet facing the disk D. This optical pickup is composed of a condensing optical system 10, a servo optical system 20, and an m-sensei system 30. Condensing optical system 1
0 is a light emitting element 11.0 such as a laser diode. Collimating lens 12, shaping prism 13, beam splitter 14
, a total reflection prism 15, and an objective lens 16 facing the disk p. Further, the objective lens 16 is connected to a correction drive device 17 of a magnetic drive type. The servo optical system 20 is composed of a condensing lens 21, a cylindrical lens 22, and a light receiving element 23 such as a four-part photoreceptor. Also (1 raw optical system 3
0 is composed of a beam splinter 31, a wavelength plate 32, a condenser lens 33, a polarizing beam splitter 34, and two light receiving elements 35 and 36 such as avalanche photodiodes.

The condensing optical system 10 is for irradiating the recording surface of the disk D with laser light in a minute spot. Information is recorded, reproduced, and erased by changing the intensity of the laser beam. The servo optical system 20 is for obtaining an error signal for scanning a minute spot along a guide groove in the disk D. The correction drive device 17 is driven according to the error signal from this servo optical system 20. Further, the reproduction optical system 30 is for reproducing the information signal of the disc D.

However, in the conventional optical pickups shown in Figs. 5 and 7, optical elements such as a light emitting element, a light receiving element, and a lens are arranged at regular intervals, so it is difficult to hold each of these elements. A holder is required. The structure of this holder must be such that the inclination and inclination of each optical member can be set with high precision, since the optical axes of each light and member must be precisely aligned. Therefore, the structure of the holder becomes complicated and the manufacturing cost becomes high. Furthermore, as shown in the figure, each optical member is oriented in multiple directions and arranged at intervals, making the entire optical pickup large.

FIG. 6 shows another conventional example, and is a plan view of an optical head called an integrated optical structure. This type of optical head is, for example, JP-A-8G-1
It is disclosed in Japanese Patent No. 29938. This optical head is
The substrate 41 is made of a ferroelectric material such as LiNbO3 crystal, and the surface thereof is subjected to Ti diffusion to form a leading wave layer. A light emitting element 42 is fixed to the end surface of the substrate 41, and a light receiving element t3 is fixed to the side end surface. A coupling lens 44 is located in the center of the substrate 41.
is formed, and Tht due to the diffraction grating is formed on the [11j side]
An object lens 45 is formed and faces the recording surface of the disc D. Further, the substrate 41F- has a bent diffraction grating 46 and an electrode 47 for generating surface acoustic waves.
is located. In one optical spatula of this type, the reflected light from the disk D is reflected by the bent diffraction grating 46,
By receiving the light with the light receiving element 43, a focus error signal of the light with respect to the disk D can be obtained.

However, the optical head with this integrated optical structure is configured exclusively for detecting focus error signals, etc., and effectively detects the entire optical components of the optical pickup shown in FIGS. 5 and 7. It was not enough to place them in a centralized location.

[Purpose of the invention]

The present invention has been made in view of the above-mentioned conventional problems.The present invention has been made in view of the above-mentioned problems of the conventional art. The purpose of this invention is to miniaturize the optical pickup and configure it with high precision by effectively arranging the optical pickup.

[Summary of the invention]

In the optical pickup according to the present invention, reflective surfaces are formed on both sides of a flat transparent substrate, and an optical path is formed inside the transparent substrate through which light reflected by the reflective surfaces travels. At a position opposite to the optical path in
Optical elements such as a light emitting element, a light receiving element, and a lens are arranged, and a light projecting part is provided on the surface of the transparent substrate to send and receive the light that has passed through the optical path to and from the recording medium. .

In the present invention, light emitting elements are provided on both sides of a transparent substrate such as glass.
By arranging optical elements such as a light-receiving element and a lens, and forming an optical path by reflection inside the transparent substrate, the overall thickness of the optical pickup can be made thinner, and the pickup can be arbitrarily configured for any purpose. be.

[Embodiments of the invention]

Embodiments of the present invention will be described below with reference to FIGS. 1 to 4.

Figures 1 and 2 show a first embodiment of the present invention, with Figure 1 being a side view showing an optical pickup installed in a compact disc player, and Figure 2 being a perspective view thereof. ' The reference numeral 51 in the figure is a transparent substrate. This transparent substrate 51 is formed of plate-shaped glass, and the flatness and parallelism of both the front and back surfaces are precisely controlled. Moreover, this transparent substrate 51 can also be formed from a plastic material. In this case, it is necessary to select a material whose various conditions such as flatness and refractive index change little due to changes in temperature. In FIG. 1, laser light is indicated by horizontal and vertical lines.

The horizontal lines indicate the light emitted by the light emitting element 1a such as a laser diode, and the vertical lines indicate the light reflected from the recording surface of the disc D. These lights are reflected on the front and back surfaces of the transparent substrate 51 and follow an optical path. To form this optical path,
On both sides of the transparent substrate 51, total reflection surfaces AL, A2. A3 and a semi-reflective surface B are formed. This total reflection surface A1~
A3 and semi-reflective surface B are formed, for example, by depositing a multilayer dielectric material such as 5i02 or T102. By controlling the thickness of the multilayer film of the 'yA electric body, a total reflection surface Al-A3 and a semi-reflection surface B are formed separately.

A diffraction grating 52 is formed between the semi-reflective surface B and the light-emitting element 1a on which a light emitting element 1a such as a laser diode is fixed. This diffraction grating 52
is for refracting the laser light emitted from the light emitting element 1a toward the total reflection surface A. This diffraction grating 52 is integrally formed on the surface of the transparent substrate 51 by processing using a photographic grating or an electron beam. In addition, another diffraction grating 53 is provided on the light projecting portion of the substrate surface located in the direction of reflection by the total reflection surface A3.
is formed. This diffraction grating 53 is formed in the shape shown schematically in FIG.
One function is to direct this parallel light in a direction perpendicular to the surface of the transparent substrate 51. This diffraction grating 53
They are also integrally formed on the substrate surface using photographic gratings or electron beam processing.

Further, an objective lens 5a is provided above the diffraction grating 53. The objective lens 5a is held by a correction drive device 9a using a magnetic drive system and faces the disk D, similar to a conventional optical pickup.

Further, a concave lens 6a is provided in the direction in which the reflected light indicated by the vertical line is reflected by the semi-reflective surface B. This concave lens 6a is fixed to the back surface of the transparent substrate 51, and its surface is a total reflection surface C1. A cylindrical lens 7a is sunk in the reflection direction of the concave lens 6a, and its surface forms a total reflection surface C2.

A light receiving element 8a such as a photodiode is fixed in the direction of reflection of the cylindrical lens 7a.

Concave lens 6a, cylindrical lens 7a, and light receiving element 8
A is fixed to the front and back surfaces of the transparent substrate 51. Among these, especially the concave lens 6a and the cylindrical lens 7a can be integrally image-molded when forming the transparent substrate 51 into an IQ shape.

Also, a correction drive device 9a holding the objective lens 5a
can be supported on the surface of the transparent substrate 51. Furthermore, a circuit for controlling the light emitting element 1a, the light receiving element 8a, and the correction drive device 9a is formed by bonding a flexible substrate to the surface of the transparent substrate 51 or by directly depositing a conductive pattern on the surface of the transparent substrate 51. It is also possible to perform Rn on this conductor pattern.

Next, the operation of the optical pickup shown in FIGS. 1 and 2 will be explained.

The optical pickup shown in FIGS. 1 and 2 is mounted on a moving mechanism, and is driven so that the objective lens 5a moves from the center of the disks D toward the outer periphery. Light emitting element 1
The laser diffused light emitted from a is directed to the right in FIG.
, A3, and is reflected by the diffraction grating 5 of the light projecting section.
Sent to 3.

The light, which is parallelized by the diffraction grating 53 and bent perpendicularly to the transparent substrate 51, is irradiated onto the recording surface of the disk D from the objective lens 5a, and a light spot is formed on the recording surface of the disk D. Ru.

The reflected light from the recording surface of the disk D is converged again by the diffraction grating 53 and is incident on the transparent substrate 51. The reflected light is then reflected by the total reflection surfaces A to A3, further reflected by the semi-reflection surface B, and is sent inside the transparent substrate 51 toward the left in FIG. The reflected light is further reflected by each total reflection surface C of the concave lens 6a and the syringolimetric lens 7a.
It is reflected by I and 02 and detected by the light receiving element 8a.

Information recorded on the disc D as a digital signal is read by a light reception signal from the light receiving element 8a. Furthermore, due to astigmatism of the convergent light that has passed through the cylindrical lens 7a, the light receiving section of the light receiving element 8a divided into four
Errors in the light spot formed on the recording surface of the disk D, ie, focus errors and tracking errors, are detected. Based on this error signal, a signal is sent to the correction drive device 9a, the objective lens 5a is driven, and the optical stub formed on the disk D is corrected.

3 and 4 show a second embodiment of the present invention, in which FIG. 3 is a side view showing an optical pickup installed in a magneto-optical disk memory device; FIG.

This optical pickup exhibits the same function as the conventional optical pickup shown in FIG. Third
The optical pickup shown in the figure is composed of a condensing optical system 10a, a servo optical system 20a, and a reproducing optical system 30a. Each optical system 10a, 20a, 30a corresponds to each optical system 10, 20, 30 shown in FIG. 7, respectively.

A transparent substrate 61 of this optical pickup is constructed by overlapping two glass substrates 62 and 63. It is also possible to use plastic substrates instead of the glass substrates 62 and 63. On both the front and back sides of the transparent substrate 61, there are total reflection surfaces A4. A5. and a semi-reflective surface B are formed.

In the condensing optical system 10a, the laser diffused light emitted from the light emitting element Lla installed on the semi-reflecting surface Brl is made into parallel light by the diffraction grating 63 provided between the one light emitting element ILa and the semi-reflecting surface Bl, It is further directed toward the shaping prism 13a. Total reflection surface C of the surface of the shaping prism 13a
The parallel light reflected by 3 is directed perpendicularly to the transparent substrate 61 by the diffraction grating 64, and is irradiated onto the disk D from the objective lens 16a. This objective lens 1
6a is held by a correction drive device 17a.

The reflected light from the disk D is reflected by the total reflection surface C3 and the semi-reflection surface B of the shaping prism 13a, and is sent in the direction of the beam splitter 31a formed between the two glass substrates 62 and 63. . One of the lights separated by the beam splinter 31a passes through the condensing lens 21a of the servo optical system 20a and is reflected by the total reflection surface C4 of the condensing lens 21a to become convergent light. And cylindrical lens 22
The light is reflected by the total reflection surface C5 on the surface of point a, and detected by the light receiving element 23a, which is a photodiode.

Further, the other light separated by the beam splitter 31a is reflected by the total reflection surfaces A5 and A4, and is reflected by the reproduction optical system 30.
It is reflected by the total reflection surface C6 of the surface of the condensing lens 33a constituting at-, and becomes convergent light. This light is further split by a beam splitter 34a provided on the mating surfaces of two glass substrates 62 and 63, and is split by an avalanche photodetector.
The light is received by light-receiving elements 35a and 36a using an ode.

The condensing optical system 10a is for irradiating the recording surface of the disk D with a laser beam in a minute spot, and the servo optical system 20a is for scanning the minute spot along the guide groove in the disk D. This is to obtain the error signal. Further, the reproduction optical system 30a is for reproducing the information signal.

〔Effect of the invention〕

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

(1) Since optical elements such as a light emitting element, a light receiving element, and a lens are mounted on both sides of a transparent substrate, the entire optical pickup can be made smaller and thinner.

(2) If the flatness of the transparent substrate is formed with high precision, each optical member installed on the transparent substrate can be automatically assembled with high precision. Therefore, there is no need to adjust the inclination or inclination of each optical member, and assembly can be performed easily and at low cost.

(3) Since the total reflection surface and semi-reflection surface on the surface of the transparent substrate are formed by T'4R dielectric pairs, etc., this transparent substrate can be mass-produced.

(4) The main parts of the optical pickup are assembled by placing optical members on both the front and back sides of the transparent substrate, so it is possible to combine them freely depending on the type of pickup, and it can be implemented in optical pickups of various devices. Is possible.

[Brief explanation of drawings]

1 and 2 show a first embodiment of the present invention, in which FIG. 1 is a side view showing an optical pickup for a compact disc player, FIG. 2 is a perspective view thereof, and FIG. Fig. 4 shows a second embodiment of the present invention, Fig. 3 is a side view showing an optical pickup for magneto-optical disk memory, Fig. 4 is a perspective view thereof, and Fig. 5 is a conventional compact An explanatory diagram showing the structure of an optical pickup for a disk player, FIG. 6 is a plan view of an optical head with a conventional integrated optical structure, and FIG. 7 is an explanatory diagram showing the structure of a conventional optical pickup for a magneto-optical disk memory. It is a diagram. 51.61...Transparent substrate, 62.63...Glass plate, 1a, 1la--Light emitting element, 8a, 23a, 35a
, 36a... Light receiving element, 5a, 16a... Objective lens, 6a, 7a, 13a, 21a, 22a, 33a...
・Lens, 52.63... Diffraction grating, 53.64...
・Diffraction grating of the light projection part, A1 to A5... Total reflection surface, B,
B... Semi-reflective surface, D... Recording medium (disk).

Claims (3)

[Claims] (1) Reflective surfaces are formed on both sides of a flat transparent substrate,
An optical path through which the light reflected by the reflective surface travels is formed inside the transparent substrate, and optical elements such as a light emitting element, a light receiving element, and a lens are arranged at positions facing the optical path on both sides of the transparent substrate. The optical pickup is provided with a light projecting section on the surface of the transparent substrate, which sends and receives the light that has passed through the optical path to and from the recording medium. (2) The optical pickup according to claim 1, wherein the transparent substrate is formed by overlapping two transparent plates, and an optical element is disposed on the mating surface of each transparent plate. (3) The optical pickup according to claim 1, wherein the optical element such as a lens is integrally formed on the surface of the transparent substrate.