JPH04276319A - Optical pickup device - Google Patents

Abstract

PURPOSE:To attain miniaturization and simultaneously to improve efficiency in optical utilization by using the combination of a reflection type beam shaping prism and grating. CONSTITUTION:A beam of light emitted from a semiconductor laser 1 is deflected at right angle by being reflected by the reflection area 12a of the reflection type beam shaping prism 12; after being shaped with a desired beam shaping ratio, it irradiates the face of an magneto-optical disk 5, and the recording of information, etc., is performed. Also, the reflected light from the disk 5 is made incident on the prism 12, and by transmitting through a grating face 13a of a grating element 13, is divided into a deflected transmitted light T and a diffracted light K which are orthogonally crossed with each other. These transmitted light T and diffracted light K are reflected by a total reflection face 13b; the transmitted light T further passes through transmissively, the diffracted light K is further diffracted, and respectively received by a light receiving element 6. In this case, focus error signals and track error signals are respectively detected.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical pickup device that records and reproduces information using an optical information recording medium, and also performs tracking servo and focus servo.

0002

2. Description of the Related Art First, a first conventional example will be explained based on FIG. Light emitted from a semiconductor laser 1 as a laser light source is reflected by a diffraction grating 2a formed on one surface of a beam splitting element 2, collimated by a collimator lens 3, and then condensed by an objective lens 4 to generate optical information. The light is irradiated onto the surface of the magneto-optical disk 5 as a recording medium, thereby recording information. In addition, the magneto-optical disk 5
After passing through the objective lens 4 and collimating lens 3 sequentially, the reflected light from After being reflected by the total reflection surface 2b, the light passes through the diffraction grating 2a again and is emitted to the outside. At this time, the transmitted light T is transmitted again, and the diffracted light K is reflected again. The transmitted light T and the diffracted light K are detected by the light receiving element 6,
Thereby, a magneto-optical signal can be detected by determining the difference between the lights, a focus error signal can be detected by a beam size method, and a track error signal can be detected by a push-pull method.

Next, a second conventional example will be explained based on FIG. 12. Here, the total reflection surface 2b is provided to be inclined with respect to the diffraction grating 2a as shown in the first conventional example, and the layout of the optical system is changed. By arranging them at an angle in this manner, it is possible to arrange two rows of light receiving elements 6 on one side of the semiconductor laser 1, which is advantageous in terms of mounting.

Next, a third conventional example will be explained based on FIG. 13. The light emitted from the semiconductor laser 1 is reflected by the semi-reflective film 8a on the surface grating 8 of the dual type grating 7. This semi-reflective film 8a is designed to irradiate the magneto-optical disk 5 with a desired optical power. The reflected light becomes parallel light by the collimating lens 3. This parallel light is simply reflected light and is not diffracted light from the surface grating 8, so no aberration occurs.
Therefore, the shape of the surface grating 8 does not need to be particularly curved or have a modulation pitch. The parallel light is focused by the objective lens 4 and irradiated onto the surface of the magneto-optical disk 5 in the form of a spot. Then, due to the Kerr effect, the irradiated light is reflected with the polarization direction tilted according to the information signal on the magneto-optical disk 5, returns to the collimating lens 4 again, and is converged by the collimating lens 4. The light becomes light and enters the surface grating 8. in this case,
The dual type grating 7 is arranged so that the gratings 8 and 9 formed on both the front and back surfaces form a black angle with respect to the light reflected from the magneto-optical disk 5 (
That is, the gratings 8 and 9 formed on both the front and back surfaces
is formed in a direction that makes an angle of 45° with respect to the polarization direction of the light from the semiconductor laser 1). The light incident on the front grating 8 is separated into transmitted light T and diffracted light K, and then enters the back grating 9. This back grating 9 is a transmission type grating, and its grating direction is the same as that of the front grating 8. That is, the transmitted light (0th order light) T of the surface grating 8
The light passes through the back grating 9 as it is and becomes the 0th order light, and the diffracted light (first order light) K of the front grating 9 is also diffracted by the back grating 9 and becomes the first order light K. The light thus separated into two lights, the 0th order light T and the 1st order light K, is received by the photodetector 6, so that the light intensity of the 0th order light T and the 1st order light K is An optical information signal, focus error signal, and track error signal can be detected from the difference. In this case, by providing the dual grating 7 with a beam splitter-like function, the degree of freedom in designing the layout of the optical system can be increased. The above-mentioned first conventional example and third conventional example are disclosed in Japanese Patent Application No. 2-172964 filed by the present applicant.
This is what is stated in the number.

[0005]

In all of the conventional examples described above, the collimating lens 3 has both a beam shaping function and a collimating function. That is,
As shown in FIG. 14, by making the short axis X of the emitted light 1a of the semiconductor laser 1 substantially equal to the diameter of the collimating lens 3, the long axis Y of the emitted light 1a is discarded, and the collimated light 3a
has been realized. For this reason, the light utilization efficiency deteriorates, and the noise components of various detection signals (optical magneto signals, focus error signals, etc.) increase.

Therefore, as shown in FIG. 15, when a transmission type beam shaping prism 10 is used, the light is deflected at an angle of θ. In all of the three conventional examples described above, as shown in FIG.
), the use of a beam shaping prism that deflects at an angle of θ, as described above, goes against this trend toward thinning and is highly efficient. I can't say it's by design. Also, Figure 1
Even if the beam shaping prism 10 is arranged as shown in FIG. 7 to reduce the thickness, it cannot be said that the structure is sufficiently miniaturized.

[0007]

[Means for Solving the Problems] In the invention as set forth in claim 1, the light emitted from a laser light source is focused by an objective lens and irradiated onto an optical information recording medium to perform recording, and the optical information recording medium is In an optical pickup device that reproduces information and detects a track error signal and a focus error signal using reflected light from a A reflective beam that has an optical path separation member formed with a grating surface that reflects part of the light on one side and a total reflection surface formed on the other side, and has a reflection surface that is integrated with this optical path separation member and reflects a part of the light. A shaping prism was installed.

According to the second aspect of the invention, in the first aspect of the invention, the total reflection surface is provided to be inclined with respect to the grating surface.

In the third aspect of the invention, the light emitted from the laser light source is focused by an objective lens and recorded by irradiating it onto the optical information recording medium, and the reflected light from the optical information recording medium is used. information playback and track error signals,
In an optical pickup device that detects a focus error signal, a grating surface that reflects a part of the light on one side is formed on the optical path of the light emitted from the laser light source toward the optical information recording medium, and a grating surface that reflects a part of the light on the other side. An optical path separation member on which a transmission type grating surface was formed was provided, and a reflection type beam shaping prism having a reflection surface that reflected a part of light was provided which was integrated with the optical path separation member.

[0010] In the invention according to claim 4, claims 1, 2,
In the invention described in item 3, a grating is formed on the reflective surface of the reflective beam shaping prism.

[0011]

[Operation] In the invention as claimed in claim 1, by combining a reflective beam shaping prism and a grating, a right angle deflection angle and a desired beam shaping ratio (ratio of short axis X to long axis Y), which could not be achieved conventionally, can be achieved. This makes it possible to realize a thin and compact optical pickup optical system with high light utilization efficiency.

[0012] In the second aspect of the invention, since a plurality of light-receiving elements can be provided close to each other, it is possible to obtain an advantage in mounting.

According to the third aspect of the invention, the degree of freedom in designing the layout of the optical system can be increased.

In the fourth aspect of the invention, since the reflective surface of the reflective beam shaping prism also has a grating, the light utilization efficiency can be further improved.

[0015]

Embodiment A first embodiment of the present invention will be explained based on FIGS. 1 to 4. Note that this embodiment is a partially modified version of the first conventional example (see FIG. 11) described above, and a description of the same parts will be omitted, and the same parts will be denoted by the same reference numerals.

As shown in FIG. 1, light emitted from a semiconductor laser 1 as a laser light source is focused by an objective lens 4 and irradiated onto a magneto-optical disk 5 as an optical information recording medium to perform recording. In an optical pickup device that reproduces information and detects a track error signal and a focus error signal using reflected light from the magneto-optical disk 5, while the light emitted from the semiconductor laser 1 is directed toward the magneto-optical disk 5, A reflective beam shaping prism 12 is provided on the optical path. This reflective beam shaping prism 12 is formed with a reflective surface 12a that reflects a portion of the incident light. Furthermore, a grating element 13 as an optical path separation member is integrally provided on the reflective surface 12a side of the reflective beam shaping prism 12. This grating element 13 has a grating surface 13a located on the reflective surface 12a side that reflects a portion of light, and a total reflection surface 13b on the opposite side of the grating surface 13a.

In such a configuration, the basic functions of the reflective beam shaping prism 12 will be described first with reference to FIGS. 2 to 4. The beam a from the semiconductor laser 1 is reflected by the reflecting surface 12a and travels as a beam b. If the angle of incidence with respect to the perpendicular on slope A is θa, the deflection angle between beam a and beam b is θb, and the apex angle is θc, then by appropriately selecting the incident angle θa and the apex angle θc, An elliptical beam a having a minor axis X and a major axis Y can be shaped into a perfectly circular beam b, and a right angle deflection angle θb can be obtained. As an example,
FIG. 4 shows the relationship among θa, θb, θc, and beam shaping ratio (X/Y) when the refractive index of the reflective beam shaping prism 12 is 1.495.

By using the reflective beam shaping prism 12 having such optical characteristics, the beam progresses as follows. The light emitted from the semiconductor laser 1 enters the reflective beam shaping prism 12 and is reflected by its reflective surface 12a to be deflected at right angles and shaped to a desired beam shaping ratio. 4, the magneto-optical disk 5
The light is irradiated onto the surface of the screen, thereby recording information and the like. Further, the reflected light from the magneto-optical disk 5 enters the reflective beam shaping prism 12 and passes through the grating surface 13a, whereby it is separated into transmitted light T and diffracted light K, which are polarized substantially orthogonally to each other. These transmitted light T and diffracted light K are reflected by the total reflection surface 13b, the transmitted light T is further transmitted and proceeds, and the diffracted light K is further diffracted and proceeds, and each is received by the light receiving element 6. . In this case, the magneto-optical signal can be detected by a differential method, the focus error signal can be detected by a beam size method, and the track error signal can be detected by a push-pull method or a sample servo method.

As described above, by combining the reflective beam shaping prism 12 and the grating surface 13a, it is possible to obtain a right angle deflection angle and a desired beam shaping ratio, which could not be achieved conventionally, thereby increasing the light utilization efficiency. This makes it possible to realize a thin and compact optical pickup system with high performance. Further, by integrating and mounting the reflective beam shaping prism 12 and the grating element 13, a more compact configuration can be achieved.

Next, a second embodiment of the present invention will be explained based on FIG. Here, the first embodiment described above (Fig. 1
In the configuration shown in (see), a substrate having a total reflection surface 13b is provided at an angle with respect to a substrate having a grating surface 13a. With this configuration, the two light receiving elements 6 can be aligned and arranged on one side of the semiconductor laser 1, which is advantageous when mounting the light receiving elements 6. In this case, by applying an anti-reflection coating to the back surface of the substrate on which the grating surface 13a is formed, reflection loss can be reduced and light utilization efficiency can be increased.

Next, a third embodiment of the present invention will be explained based on FIG. Here, the first embodiment described above (Fig. 1
This is a modification of the configuration of the dual grating element 14 as an optical path separation member in (see). That is,
The dual grating element 14 has a grating surface 14a that reflects a portion of light formed on one side, and a transmission grating surface 14b formed on the other side.

In this case, the semiconductor laser 1 emits light,
The beam-shaped light reflected by the reflective surface 12a of the reflective beam-shaping prism 12 is focused and irradiated onto the surface of the magneto-optical disk 5. The reflected light passes through the reflective beam shaping prism 12 and enters the grating surface 14a of the dual grating element 14, where it is separated into transmitted light T and diffracted light K, which are substantially perpendicular to each other. These transmitted light T and diffracted light K enter the transmission type grating surface 14b, so that the transmitted light T is transmitted as it is, and the diffracted light K is further diffracted and travels, and is respectively received by the light receiving element 6. . Note that the magneto-optical signal, track error signal, and focus error signal can be detected by the method described above. By making the dual grating element 14 of a transmission type in this way, the arrangement on the light receiving side can be changed, so that the degree of freedom in designing the layout of the optical system can be increased.

Next, modifications based on the three embodiments described above will be described. 7 to 10 show their configurations. 7 is a modification based on FIG. 1, FIG. 8 is a modification based on FIG. 5, and FIGS. 9 and 10 are modifications based on FIG. 6. In each of these, a grating 12b is formed on the reflective surface 12a of the reflective beam shaping prism 12. Therefore, like this, the reflective surface 1
The reason why the grating 12b was formed on the grating 2a will be described. Now, contrary to the case of the above-mentioned embodiment, the reflective surface 12a is made a high transmittance surface, and the light emitted from the semiconductor laser 1 is made incident on the grating 12b through the high transmittance surface.
By irradiating the magneto-optical disk 5 with the reflected light from the grating 12b, the light utilization efficiency can be increased. Therefore, in this way, the reflective surface 12a
By having the grating 12b serve as both of these functions, it is possible to achieve miniaturization, and at the same time, it is possible to obtain even higher light utilization efficiency.

[0024]

[Effects of the Invention] The invention as claimed in claim 1 performs recording by condensing light emitted from a laser light source by an objective lens and irradiating it onto an optical information recording medium, and also collects light reflected from the optical information recording medium. is used to reproduce information and track error signals,
In an optical pickup device that detects a focus error signal, a grating surface that reflects a part of the light on one side is formed on the optical path of the light emitted from the laser light source toward the optical information recording medium, and a grating surface that reflects a part of the light on the other side. An optical path separating member with a total reflection surface is provided, and a reflective beam shaping prism having a reflective surface that reflects part of the light is integrated with the optical path separating member, so that the reflective beam shaping prism and the grating can be combined By combining these, it is possible to obtain a right-angled deflection angle and a desired beam shaping ratio (ratio of short axis X to long axis Y), which was previously impossible. This makes it possible to realize an optical pickup optical system.

[0025] According to the invention as claimed in claim 2, since the total reflection surface is provided at an angle with respect to the grating surface, in addition to the effect described in claim 1, a plurality of light receiving elements can be provided close to each other. , which can be more easily implemented.

[0026] The invention according to claim 3 performs recording by condensing light emitted from a laser light source by an objective lens and irradiating it onto an optical information recording medium, and also uses reflected light from the optical information recording medium. In an optical pickup device that reproduces information and detects track error signals and focus error signals, a part of the light is directed to one side on the optical path of the light emitted from the laser light source as it heads toward the optical information recording medium. An optical path separating member is provided in which a reflective grating surface is formed and a transmission grating surface is formed on the other side, and a reflective beam shaping prism that is integrated with this optical path separating member and has a reflective surface that reflects a portion of light is provided. Therefore, in addition to the effect described in claim 1, the degree of freedom in designing the layout of the optical system can be increased.

According to the fourth aspect of the invention, since a grating is formed on the reflective surface of the reflective beam shaping prism, the reflective surface also serves as a grating, so that it is possible to further increase light utilization efficiency while reducing the size of the prism. It is something that can be done.

[Brief explanation of the drawing]

FIG. 1 is a configuration diagram showing a first embodiment of the present invention.

FIG. 2 is a perspective view showing the principle of beam shaping using a reflective beam shaping prism.

FIG. 3 is a side view showing the relationship between the incident angle and polarization angle of a beam.

FIG. 4 is a characteristic diagram showing the beam shaping ratio with respect to angular changes in the beam incidence angle and the prism apex angle.

FIG. 5 is a configuration diagram showing a second embodiment of the present invention.

FIG. 6 is a configuration diagram showing a third embodiment of the present invention.

FIG. 7 is a side view showing a modification of the first embodiment of the present invention.

FIG. 8 is a side view showing a modification of the second embodiment of the present invention.

FIG. 9 is a side view showing a modification of the third embodiment of the present invention.

FIG. 10 is a side view showing another modification of the third embodiment of the present invention.

FIG. 11 is a configuration diagram showing a first conventional example.

FIG. 12 is a configuration diagram showing a second conventional example.

FIG. 13 is a configuration diagram showing a third conventional example.

FIG. 14 is a perspective view showing beam shaping using a conventional collimating lens.

FIG. 15 is an optical path diagram showing a state when the beam is deflected by an angle θ by a beam shaping prism.

FIG. 16 is a side view showing the arrangement of lenses in the optical pickup optical system when the emitted light is deflected at right angles and enters the medium.

FIG. 17 is a perspective view showing a case where a reflective beam shaping prism is arranged on the output optical path.

[Explanation of symbols]

1 Laser light source 4 Objective lens 5 Optical information recording medium 12 Reflective beam shaping prism 12a
Reflective surface 12b Grating 13 Optical path separation member 13a Grating surface 13b Total reflection surface 14 Optical path separation member 14a Grating surface

Claims (4)

[Claims] Claim 1: The light emitted from a laser light source is focused by an objective lens and irradiated onto an optical information recording medium to perform recording, and the reflected light from the optical information recording medium is used to reproduce information or track information. In an optical pickup device that detects an error signal and a focus error signal, a grating surface that reflects a part of the light to one side is formed on the optical path between the light emitted from the laser light source and the optical information recording medium. An optical pickup characterized in that an optical path separating member is provided with a total reflection surface formed on the other side thereof, and a reflective beam shaping prism is integrated with the optical path separating member and has a reflecting surface that reflects a part of light. Device. 2. The optical pickup device according to claim 1, wherein the total reflection surface is inclined with respect to the grating surface. 3. The light emitted from the laser light source is focused by an objective lens and irradiated onto an optical information recording medium to perform recording, and the reflected light from the optical information recording medium is used to reproduce information and track information. In an optical pickup device that detects an error signal and a focus error signal, a grating surface that reflects a part of the light to one side is formed on the optical path between the light emitted from the laser light source and the optical information recording medium. An optical beam-shaping prism comprising: an optical path separating member having a transmission grating surface formed on the other side; and a reflective beam shaping prism integrated with the optical path separating member and having a reflective surface that reflects a part of the light. pickup device. 4. Claim 1, characterized in that a grating is formed on the reflective surface of the reflective beam shaping prism.
2. The optical pickup device described in 2 and 3.