JPH04206046A - Optical head - Google Patents

Abstract

PURPOSE:To obtain a compact, thin optical head by changing the optical axis of the light emitted from a semiconductor laser into the direction of the optical axis of an objective lens with a light-amount separating means, and arranging a photodetector on an optical substrate at a position facing the objective lens with the light-amount separating means in-between. CONSTITUTION:A part of the amount of laser light emitted from a semiconductor laser 11 is reflected from a half mirror 12 which is inclined by about 45 degrees with respect to the optical axis. The reflected light is directed toward the direction of the optical axis of an objective lens 13 and reflected from an optical disk. The light is modulated by the amount of light with the pits of the optical disk. The light is cast into the objective lens 13 again and returned into the half mirror 12. A part of the light is transmitted and cast into a photodetector 14 which is attached on an optical substrate 10. Since the optical axis is changed with the half mirror 12 in this way, optical parts such as a rise-up mirror are not required. The photodetector 14 can be directly arranged laterally on the optical substrate in parallel with the objective lens 13. Therefore, the number of the parts can be decreased, and the optical head can be made compact and thin.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to an optical head used for recording and reproducing optical discs.

2. Description of the Related Art In recent years, optical heads have received the highest technical importance as a basic component of optical disk drives.

A conventional optical head will be explained with reference to FIGS. 6(a) and 6(b).

FIG. 6(a) is a front view showing the structure of a conventional optical head, and FIG. 6(ω) is a side sectional view. In the same figure, 1
is a semiconductor laser that emits laser light for reproducing information on an optical disc. Reference numeral 2 denotes a half mirror, which has the function of separating the emitted light from the semiconductor laser 1 and directing it to the rising mirror 3, and directing the reflected light from the rising mirror 3 to the light receiving element 4. It also plays the role of generating astigmatism for use in focus control of the objective lens 5. A concave lens 6 magnifies the astigmatism generated in the half mirror 2 and guides it to the light receiving element 4.

Note that the semiconductor laser 1 generally has a long shape in the emission direction, and the emission direction of the semiconductor laser 1 is emitted onto a plane parallel to the optical disk surface, and the emission direction of the semiconductor laser 1 is emitted in a direction perpendicular to the optical disk. Change the optical axis and use the objective lens 5g4
The optical head itself is made thinner.

To explain the basic operation of the above optical head,
A part of the light emitted from the semiconductor laser 1 passes through a half mirror 2, and then is guided to an objective lens 5 with its optical axis direction changed by a rising mirror 3. The objective lens 5 serves to focus the light from the semiconductor laser 1 onto an optical disk (not shown), collects the reflected light whose intensity has been modulated by the bits on the optical disk, and returns it in the direction of the semiconductor laser 1. doing. The reflected light of the optical disc emitted from the objective lens 5 is converted by the rising mirror 3 into light having an optical axis in a plane parallel to the optical disc, including the light emission direction of the semiconductor laser 1, and then sent to the half mirror 2. It passes through and heads toward the concave lens 6 while causing astigmatism. No.1
- The light having astigmatism that has passed through the mirror 2 is detected by the light receiving element 4 after the aberration is magnified by the concave lens 6.

In the light receiving element 4, a focus control signal for controlling the objective lens 5 is generated using the astigmatism generated in the half mirror 2, and a tracking control signal and a data signal of the optical disk are detected from the bit signal from the optical disk. Then, the basic signal of the optical pickup is obtained.

FIG. 7 also shows a conventional optical head, with FIG. 7(a) being a front view and FIG. 7(b) being a side sectional view. This optical head detects the temporal phase difference of the bit signal of the optical disk and generates a focus control signal.
This is intended to eliminate the need for the thick /N-fum mirror 2 and the concave lens 6 for magnifying astigmatism in Figures (a) and (b). Regarding the configuration of this optical head, Fig. 6(a)
, Parts that are the same as those of the optical head in (■) are given the same numbers and explained. 1 is a semiconductor laser, and 7 is a vine-shaped mirror that branches the emitted light from the semiconductor laser 1 into an objective lens 5 and a light-receiving element 4. be. In addition, Fig. 6(a), (
Unlike in b), the no. 1-f mirror 7 does not need to generate astigmatism, so it can be made thin. The laser beam separated by the half mirror 7 enters the rising mirror 3, passes through the objective lens 5, and is focused on an optical disk (not shown). The reflected light carrying the information of the bits of the optical disk passes through the objective lens 5, the rising mirror 3, and the half mirror 7 again, and is guided to the light receiving element 4. The light receiving element 4 separates and detects a data signal from the bit signal of the optical disc, and a signal used for focus and tracking control from the temporal phase difference thereof.

Problems to be Solved by the Invention However, in the above configuration, FIGS. 6(a) and (
The optical heads shown in FIGS. 7(a) and 7(b) as well as those shown in FIGS. 7(a) and 7(b) have the problem of having a large number of parts and being unsuitable for miniaturization and thinning.

The present invention eliminates the above-mentioned conventional drawbacks, and provides an optical head that can be made smaller and thinner by reducing the number of parts.

Means for Solving the Problems In order to solve the above problems, the optical head of the present invention converts the optical axis of the emitted light from the semiconductor laser to the direction of the optical axis of the objective lens using the light amount separation means, and converts the optical axis of the emitted light from the objective lens. The configuration is such that the reflected light from the optical disk is detected by a light receiving element disposed on an optical substrate facing the objective lens with a light amount separating means in between.

Effects of the present invention With the above-described configuration, the optical axis is converted by the light amount separation means, thereby eliminating the need for optical components such as a mirror, and also by making the light receiving element parallel to the objective lens and directly attaching it to the optical substrate. Since it can be laid flat, the number of parts can be reduced and the optical head can be made smaller and thinner.

EXAMPLE Hereinafter, the configuration of a first example of the present invention will be described with reference to the drawings.

FIG. 1 shows a perspective view of an optical head in a first embodiment of the present invention.

In FIG. 1, numeral 10 is a U-shaped optical substrate that supports the components of the optical head of the present invention. A semiconductor laser 11 is attached to one side of the optical substrate 10 and emits a laser beam. Reference numeral 12 denotes a half mirror as a light amount separating means, which has the function of directing a part of the emitted light from the semiconductor laser 11 to the objective lens 13 and guiding the reflected light of the optical disk incident from the objective lens 13 to the light receiving element 14. It is arranged on the optical substrate 11 so as to be inclined at approximately 45 degrees with respect to the optical axis of the semiconductor laser 11. The light receiving element 14 is arranged on the optical substrate 10 so as to face the objective lens 13 with the half mirror 12 in between.

The operation of the optical head configured as described above will be explained.

A portion of the laser light emitted from the semiconductor laser 11 is reflected by a half mirror 12 tilted approximately 45 degrees with respect to the optical axis, and the reflected light is directed toward the optical axis of the objective lens 13. The light incident on the objective lens 13 is
After passing through, the light is focused on an optical disk (not shown). The reflected light undergoes light intensity modulation by the bits of the optical disk, enters the objective lens 13 again, and returns to the half mirror 12.

In the half mirror 12, part of the light passes through the optical substrate 1.
The light is incident on the light receiving element 14 mounted on the 0. Since the light receiving element 14 detects the light modulated by the bits of the optical disc, it generates the optical disc data signal from the sum signal of the focus control signal, the tracking control signal, and the bit modulation signal based on the temporal phase difference of the bit modulation signal. It becomes possible.

Here, since the light-receiving element 14 and the half mirror 12 are close to each other, a part of the emitted light from the semiconductor laser 11 directly enters the light-receiving element 14, and the amount of light detected by the light-receiving element 14 is: This is the sum of the direct current component of the amount of light directly incident from the semiconductor laser 11 and the alternating current component of the amount of light modulated by the bits of the optical disk. However, if the control signal is detected based on the temporal phase difference, the control signal can be detected and the optical head can function without using DC component information.

With the above configuration, by arranging the light receiving element 14 on the optical substrate 10 at opposite positions with the objective lens 13 and the half mirror 12 in between, even a large area light receiving element can be arranged lying on the optical substrate 10. Therefore, the optical head is thin (
The half mirror 12 guides the light from the semiconductor laser 11 to the objective lens 13 (thereby eliminating the need for parts such as a raising mirror).

Furthermore, with reference to FIG. 2, another embodiment of the optical head of the present invention will be described. Note that the same parts as in FIG. 1 are given the same numbers and explained.

First, FIG. 2 is a perspective view showing the structure of another embodiment of the present invention, in which 11 is a semiconductor laser, 14 is a photoreceptor element, and 15 is an enclosure in which this photoreceptor element 14 is encapsulated. The surface of the enclosure 15 is formed into an inclined surface, and the inclined surface is coated with a half mirror.

A part of the light emitted from the semiconductor laser 11 is reflected by the half-mirror coated slope of the enclosure 15 and guided to the objective lens 13.

The reflected light from the optical disk that enters from the objective lens 13 partially passes through the enclosure 15 and enters the light receiving element 14.
Since the signal is incident on the optical disk, the signal modulated by the bits of the optical disk can be reproduced, and the basic signal for the optical head can be obtained.

As described above, the emitted light of the semiconductor laser 11 is reflected by the surface of the half-mirror-coated enclosure 15 and guided to the objective lens 13 (thereby, the half-mirror becomes unnecessary, further reducing the number of parts, and the optical head Thin (
It is configurable. In addition, the direct light from the semiconductor laser 11 that enters the enclosure 15 is not detected by the light receiving element 14 due to the refraction of the enclosure 15 (because the direct current component of the light amount is small, the signal detection circuit can be easily configured). .

FIG. 3 is a block diagram showing the structure of another embodiment of the present invention.

In FIG. 3, 11 is a semiconductor laser which emits a laser beam. Reference numeral 14 denotes a light receiving element, which is integrally enclosed within the enclosure case 16 at an angle of approximately 45 degrees with respect to the semiconductor laser 11 so as to guide the emitted light of the semiconductor laser 11 to the objective lens 13 covering the window 17 of the enclosure case 16. be.

The objective lens 13 that covers the window 17 of the enclosure case 16 focuses the light emitted from the window 17 of the enclosure case 16 onto an optical disk (not shown), and focuses the reflected light modulated by the bits of the optical disk. , re-enter the window 17 of the enclosure case 16,
It serves to return the light to the light receiving element 14.

FIG. 4 shows a perspective view of the arrangement of the semiconductor laser 11 and the light receiving element 14.

In FIG. 4, the light receiving element 14 includes a light amount monitor portion B that monitors the amount of light emitted from the semiconductor laser 11;
A detection unit A on the chip surface emits part of the light from the semiconductor laser 11 toward the objective lens 13 and detects reflected light modulated by the bits of the optical disk that re-enters the enclosure case 16 from the objective lens 13. It consists of

The detection section A detects bit-modulated light from the optical disk, and detects a data signal, a focus control signal, and a tracking control signal from the alternating current component of the light amount. An anti-reflection film 18 is formed on the surface of the light intensity monitor part B that monitors the light intensity of the semiconductor laser 11, so that the light reflected from the light intensity monitor part B returns to the light intensity monitor part B again and This prevents the accuracy of the light amount monitor of the laser 11 from deteriorating.

FIG. 5 is a configuration diagram of a movable support when such an optical head is used for focus control and tracking control of an optical disk. In FIG. 5, reference numeral 19 denotes the optical head shown in FIG. 3, which is fixed to a fixing member 21 through an elastic wire 20, and is oriented horizontally and vertically (in the direction of the arrow in the figure) of the objective lens 13. It is configured to be driven with a degree of freedom.

As described above, the semiconductor laser 11 and the light receiving element 14, which has the role of bending the emitted light of the semiconductor laser 11 by surface reflection and detecting a signal, are housed in the same case 16.
By enclosing the optical head in a container, covering it with an objective lens 13, and driving the entire optical head with an elastic wire 20, it can play the basic role of an optical head, and the optical head can be made smaller and thinner.

Furthermore, by forming the anti-reflection film 18 on the light amount monitor part B of the light receiving element 14, it is possible to prevent the re-incident light from the objective lens 13 from entering the light amount monitor part B, thereby providing a highly accurate light amount monitor. is possible.

Effects of the Invention As described above, the present invention converts the optical axis of the emitted light from the semiconductor laser to the optical axis direction of the objective lens using the light amount separating means, and moves the light receiving element to a position facing the objective lens with the light amount separating means in between. Since it is arranged on the optical substrate, it is possible to provide a small and thin optical head.

[Brief explanation of the drawing]

FIG. 1 is a perspective view of a first embodiment of the optical head of the present invention;
Fig. 2 is a perspective view of the second embodiment, Fig. 3 is a sectional view of the third embodiment, Fig. 4 is a perspective view of main parts of the third embodiment, and Fig. 5 is a perspective view of the main part of the third embodiment.
The figure is an explanatory diagram of the third embodiment, Fig. 6 (a), (b)
FIG. 7(a) is a front view and a side sectional view of a conventional optical head.
, (b) is a front view and a side sectional view of another conventional example. 10... Optical substrate, 11... Semiconductor laser, 12... Half mirror 113...
...Objective lens, 14... Light receiving element, 15...
...Inclusion body, 16...Inclusion case, 17.
...Window, 18...Anti-reflection film. Name of agent Patent attorney Haruaki Koebi and two others Fig. 1 777 - = - Optical board Fig. 2 Fig. 3 O Fig. 4 Fig. 6 (a) Fig. 7 I (2> ( b) Ri

Claims (5)

[Claims] (1) A semiconductor laser attached to an optical substrate, an objective lens that focuses the emitted light of the semiconductor laser onto an optical disk and collects reflected light from the optical disk, and directs a part of the light amount of the semiconductor laser to the objective lens. an optical head comprising: an optical separation means; and a light receiving element arranged on the optical substrate at a position facing the objective lens with the optical separation means in between and receiving a part of the reflected light of the optical disk returning from the objective lens. . (2) The surface of an enclosure containing an optical substrate, a semiconductor laser, an objective lens that focuses the emitted light of the semiconductor laser onto an optical disk, and a light receiving element that collects the reflected light from the optical disk is formed into a sloped surface. A part of the light amount of the semiconductor laser is directed toward the objective lens on the surface of the inclusion body formed in the slope shape, and a part of the reflected light of the optical disk returning from the objective lens is directed to a light receiving element inside the inclusion body. An optical head configured to receive light. (3) A semiconductor laser and a part of the emitted light of the semiconductor laser is reflected on the surface and guided to the window of the enclosure case covered with the objective lens, and the light is incident through the window of the enclosure case covered with the objective lens. An optical head comprising a light receiving element that detects the amount of light and is enclosed in the enclosure case. (4) A semiconductor laser, which has the function of reflecting a part of the emitted light of the semiconductor laser on the surface and guiding it to the window of the enclosure case, and detecting the amount of light incident on the window of the enclosure case. An optical head comprising a light-receiving element having an anti-reflection film formed on its surface to partially block reflections, and a light-receiving element enclosed in the enclosure case. (5) The optical head according to claim 4, wherein the antireflection film for blocking a portion of the incident light is selectively formed on a light receiving portion that monitors the amount of light from the semiconductor laser.