JPH0489638A - Optical head - Google Patents

Abstract

PURPOSE:To decrease the number of parts and to make a head compact and thin by changing the optical axis of light emitted from a semiconductor laser to the optical axis direction of an objective lens by a light quality separating means and detecting the reflected light of an optical disk from the objective lens by a photodetector arranged at a position where the optical axis direction of the semiconductor laser and the optical axis direction of the objective lens are overlapped. CONSTITUTION:One part of the reflected light of the optical disk is transmitted through a half mirror 16 and made incident to a photodetector 14 arranged parallelly to the half mirror 16. Since the photodetector 14 detects light modulating the pit of the optical disk, the focus control signal of phase difference, tracking control signal and the data signal of the optical disk can be generated from the signal of pit modulation. Thus, since the photodetector 14 can be arranged while being laid along the emissive optical axis of a semiconductor laser 11 by arranging the photodetector 14 in the optical axis of the semiconductor laser 11 and changing the direction of beams to the optical axis direction of an objective lens 15 while separating the quantity of light on the half mirror 16, the optical head can be made thin and parts such as a rise mirror or the like is unnecessitated.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention 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 configuration of a conventional optical head, and FIG. 6(b) is a side sectional view. In the same figure,
Reference numeral 1 denotes a semiconductor laser, which emits laser light for reproducing information on an optical disc. A half mirror 2 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 16 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 upright mirror 3 is used to align the emission direction in a direction perpendicular to the optical disk. By changing the optical axis and directing it toward the objective lens 5 side, the optical head itself can be 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 pits 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 towards the concave lens 16 while causing astigmatism. The astigmatic light that has passed through the half mirror 2 has its aberration magnified by the concave lens 16 and is then detected by the light receiving element 4.

The light receiving element 4 uses the astigmatism generated in the half mirror 2 to generate a focus control signal for controlling the objective lens 5, and detects a tracking control signal and a data signal of the optical disc from a pit signal from the optical disc. 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 phase difference between the pit signals of the optical disc and generates a focus control signal, as shown in Fig. 6(a).
,, This eliminates the need for the thick nof mirror 2 and the concave lens 6 for magnifying astigmatism in (b).

The configuration of this optical head is shown in Fig. 6(a), (
The same parts as those in the optical head b) are given the same numbers. 1 is a semiconductor laser, and 6 is a half mirror that branches the light emitted from the semiconductor laser 1 into an objective lens 5 and a light receiving element 4. In addition, Fig. 6 (a), (b
), the nof mirror 6 does not need to generate astigmatism, so it can be made thin. The laser beam separated by the half mirror 6 enters the rising mirror 3 and passes through the objective lens 5 to an optical disk (not shown).
The light is focused on. The reflected light carrying information about the pits of the optical disk passes through the objective lens 5, passes through the raising mirror 3 and the half mirror 6 again, and is guided to the light receiving element 4. The light receiving element 4 separates and detects a data signal and a phase difference signal used for focus and tracking control from the pit signal of the optical disc.

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

The present invention 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 optical axis direction of the objective lens using the light amount separation means, and This device has a configuration in which the reflected light from the optical tiff is detected by a light receiving element disposed at a position where the optical axis direction of the semiconductor laser and the optical axis direction of the objective lens overlap.

Effects of the present invention With the above-described configuration, the optical axis is converted by the light quantity separation means, thereby eliminating the need for optical parts such as a tilting mirror, and furthermore, the light-receiving element is arranged lying along the emission optical axis of the semiconductor laser. Therefore, the number of parts can be reduced and the optical head can be made smaller and thinner.

EXAMPLE Below, the structure of an optical head according to an example of the present invention will be explained with reference to FIG.

FIG. 1 is a side sectional view showing the configuration.

In FIG. 1, 11 is a semiconductor laser that emits laser light. 16 is a half mirror as a light amount separation means
It has the function of directing a part of the light emitted from the semiconductor laser 11 to the objective lens 15 and guiding the reflected light of the optical disk incident from the objective lens 15 to the light receiving element 14. The light receiving element 14 is arranged at a position where the optical axis of the semiconductor laser 11 and the optical axis of the objective lens 15 intersect,
The semiconductor laser 11 is stacked parallel to the half mirror 16.
It is arranged at approximately 45 degrees with respect to the output optical axis.

To explain the operation of the optical head configured as above, the laser light emitted from the semiconductor laser 11 is partially reflected by the half mirror 16, and the reflected light is directed in the optical axis direction of the objective lens 15. . Objective lens 15
After passing through the objective lens 15, the incident light is focused on an optical disk (not shown).The reflected light is modulated in light intensity by the pits of the optical disk and returns to the objective lens 1.
5 and returns to half mirror 16.

A part of the reflected light from the optical disk is transmitted through the half mirror 16 and is incident on a light receiving element 14 arranged parallel to the half mirror 16 . Since the light receiving element 14 detects the light modulated by the pits of the optical disc, it is possible to generate a phase difference focus control signal, a tracking control signal, and an optical disc data signal from the pit modulation signal.

Here, since the light-receiving element 14 and the half mirror 16 are oriented parallel to the emitted light of the semiconductor laser 11, the emitted light of the semiconductor laser 11 directly enters the light-receiving element 14, and the amount of light detected by the light-receiving element 14 is is the sum of the DC component of the amount of light directly incident from the semiconductor laser 11 and the AC component of the amount of light modulated by the pits of the optical disk. However, if the control signal is detected by phase difference detection, the control signal can be detected and the optical head function can be achieved without using the DC component information.

With the above configuration, the light receiving element 14 is connected to the semiconductor laser 11.
By placing the light receiving element along the optical axis of the semiconductor laser 11 and changing the direction of the light beam in the optical axis direction of the objective lens 15 while separating the amount of light using a half mirror 16, the light receiving element 4 can be arranged, the optical head can be made thinner, and parts such as an upright mirror are not required.

Further, other embodiments of the optical head of the present invention will be described with reference to FIGS. 2 to 5. Note that the same parts as in FIG. 1 will be explained using the same numbers.

First, FIG. 2 is a block diagram showing the configuration of another embodiment of the present invention, in which 11 is a semiconductor laser, 9 is a phosphor element chip, and 10 is this phosphor element chip 9.
is enclosed, and on the surface of this enclosed package 10,
After coating the half mirror, the semiconductor laser 11
A part of the emitted light is guided to the objective lens 15. The reflected light from the optical disc that enters from the objective lens 15 passes through the interior of the partially enclosed package 10 and enters the light receiving element chip 9, so that the signal modulated by the pits of the optical disc can be reproduced. , it is possible to obtain basic signals as an optical head.

As described above, by guiding the emitted light of the semiconductor laser 11 to the objective lens 5 by reflection on the surface of the half-mirror-coated encapsulation package 10, the half-mirror becomes unnecessary and the number of parts can be further reduced. Furthermore, since the encapsulation package 10 can be placed lying down along the optical axis of the semiconductor laser 11, the optical head can be made thinner. Furthermore, since the optical head can be configured only with the semiconductor laser 11, the encapsulation package 10, and the objective lens 5, the optical head can be significantly downsized.

FIGS. 3 to 5 are also configuration diagrams showing the configuration of other embodiments of the present invention.

In FIG. 3, 21 is a laser chip of a semiconductor laser, which emits a laser beam.

Reference numeral 12 denotes a light-receiving element chip, which is integrated into the enclosure 14 at an angle of 45 degrees with respect to the semiconductor laser chip 21 so as to guide a portion of the amount of light emitted from the semiconductor laser chip 21 to the window 13 of the enclosure 14. It is enclosed.

Reference numeral 15 denotes an objective lens, which focuses the light emitted from the window 13 of the inclusion body onto a disk (not shown), and makes the reflected light modulated by the pits of the optical disk enter the window 13 of the inclusion body. , serves to return the light to the light receiving element chip 12.

The light-receiving element chip 12 includes a light amount monitor section that monitors the amount of light emitted from the semiconductor laser chip 21, and a chip surface that reflects a part of the light from the semiconductor laser chip 21 toward the window 13 of the encapsulant. It consists of a detection section that detects the reflected light of the optical disk from the window 13 of the body.

The configuration of the light receiving element 12 is shown in FIG. 4. A is a detection unit that detects a part of the amount of light reflected from the optical disk, and detects the alternating current component of the amount of light from the modulation information of the pits from the optical disk. , data signals, and control signals for focus control and tracking control, and is divided into four parts. In addition, a reflective layer is deposited on the surface of this A, and reflects a part of the emitted light from the semiconductor laser chip 21 that is incident on the light receiving element 12.
It also plays a role in pointing toward 3. B is a light amount monitor unit that monitors the DC component of the amount of light emitted from the semiconductor laser chip 21.

FIG. 5 is a partially enlarged view of the optical head shown in FIG. 3, and shows the structure of the aperture limiting member 14a provided in the window 13 of the enclosure 14. According to the figure, the window 13 of the enclosure 14 is configured such that light is incident only on the detection section A of the light receiving element chip 12 and light that is incident on the light amount monitor section B is blocked by the aperture limiting member 14a.

By providing the aperture limiting member 14a in the window 13 of the enclosure in this manner, the light that enters through the window 13 of the enclosure does not enter the light amount monitor section B of the light receiving element chip 12.
The light amount monitor section B can detect only the DC component of the amount of light emitted from the semiconductor laser dip 21.

As described above, the optical head can be made smaller and thinner by encapsulating the semiconductor laser chip 21 and the light receiving element chip 12, which has the role of bending the emitted light from the semiconductor laser depth 21 by surface reflection, in the same enclosure 14. It becomes possible.

Further, the semiconductor laser chip 21 and the light receiving element chip 1
Since only the second semiconductor is encapsulated, the optical head can be constructed without using parts such as mirrors that are likely to be contaminated with dust or oxides, resulting in stable production.

Furthermore, by making the light-receiving element chip 12 double-configured with the light-amount monitor section B that monitors the light amount and the detection section A, it is possible to detect signals and monitor the emitted light amount with one light-receiving element chip, which is much easier than before. The light receiving element chip used to monitor the amount of laser light is no longer required, reducing the number of parts.

Further, by providing an aperture limiting member 14a in the window 13 of the enclosure to prevent light from entering the light amount monitoring section B, it becomes possible to monitor the amount of light with even higher accuracy.

In the embodiment shown in FIG. 1, the light receiving element 4 is attached parallel to the half mirror 6, but it may also be arranged parallel to the objective lens 5 (or, regardless of the arrangement, the semiconductor laser 1 The same effect can be achieved by reducing the distance between the half mirror 6 and the light receiving element 4 until the emitted light hits the light receiving element 4.

Further, in the embodiment shown in FIG. 2, the enclosed package 10 has a flat plate structure, but it may also be triangular and the light receiving element chip 9 arranged on the bottom surface.

Effects of the Invention As in science and technology, the present invention uses a light amount separation means to convert the optical axis of the emitted light from the semiconductor laser to the optical axis direction of the objective lens, and also converts the reflected light of the optical disk from the objective lens to the optical axis of the semiconductor laser. Since the configuration is such that detection is performed using a light receiving element placed at a position where the optical axis direction and the optical axis direction of the objective lens overlap, a small and thin optical head can be provided.

[Brief explanation of the drawing]

FIG. 1 is a side sectional view of one embodiment of the optical head of the present invention, FIG. 2 is a side sectional view of another embodiment of the invention, FIG. 3 is a side sectional view of another embodiment, and FIG. The figure is an explanatory diagram of the configuration of the light receiving element chip which is the main part of the optical head in Figure 3, Figure 5 is a configuration diagram explaining the aperture limiting member, and Figure 6 (a) is a front view of the conventional optical head. , FIG. 6(b) is a sectional view of the same side, FIG. 7(a) is a front view of another conventional optical head, and FIG. 7(b)
is a sectional view of the same side. 11... Semiconductor laser, 14... Light receiving element, 15... Objective lens, 16...
・Half mirror agent's name Patent attorney Shigetaka Awano 1 idiot //...+Conductor laser...- 7+...1! 15... Eagle illusion lens / 6... Half mirror 4 - Funeral map (Ku) , ( Funeral map ((L) (b) Cb)

Claims (5)

[Claims] (1) A semiconductor laser, 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 the emitted optical axis of the semiconductor laser and the optical axis of the objective lens are both incident on the objective lens. A light-receiving element having the function of detecting the amount of light placed at a position, and a part of the light amount of the emitted light of the semiconductor laser directed toward the optical axis direction of the objective lens, and part of the reflected light of the optical disk returning from the objective lens. An optical head comprising a light amount dividing means for directing a portion of the light toward the light receiving element. (2) A semiconductor laser, 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 a surface that is reflectively processed, and on this surface,
An optical head comprising an encapsulation package enclosing a phosphor element chip that directs a part of the emitted light of the semiconductor laser toward the objective lens and detects reflected light from the optical disk that is incident from the objective lens. (3) A laser chip of a semiconductor laser; a part of the emitted light of the semiconductor laser chip is reflected on the surface and guided to the window of the inclusion body; and the light receiving unit detects the amount of light incident on the window of the inclusion body. An optical head comprising an element chip enclosed in the enclosure. (4) The optical head according to claim 3, wherein the light-receiving element chip includes a light amount monitor section that monitors the light amount of the semiconductor laser, and a detection section that detects the amount of light incident on the window of the enclosure. . (5) The optical head according to claim 4, characterized in that the window of the enclosure is provided with an aperture limiting member for preventing incident light from the window of the enclosure from being applied to the light amount monitor section.