JPH04259924A - Optical pickup device - Google Patents

Abstract

PURPOSE:To obtain a large deflecting angle by providing plural turnable mirrors to move a laser beam across the information track of a recording medium, a prism to transmit one part of the beam through a semiconductor substrate and a semiconductor laser while being equipped with photodetectors for beam detection on the surface, and counter fixed mirror. CONSTITUTION:One part of the beam emitted from a semiconductor laser 6 is transmitted through the surface of a prism 7, which face on the laser 6 side is coated, and guided to photodetectors 4 and 5 and the quantity of light is detected while controlling the output of the laser 6. Next, the beam reflected on the surface of the prism 7 is reflected on a fixed mirror 8 and next reflected on a turn mirror 2 for deflection. The reflected beam is reflected on the mirror 8 again, reflected on another turn in mirror 3 for deflection and condensed through a condenser lens 9 to a recording medium 10. At such a time, the mirrors 2 and 3 are driven in the same direction, the deflecting angle of the laser beam is enlarged, and the entire device can be miniaturized.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention aims at irradiating a recording medium such as an optical disk with a laser beam emitted from a semiconductor laser, causing the recording medium to reflect the beam, and detecting the reflected beam using a photodetector. The present invention relates to an optical pickup device that records and reproduces information through detection.

0002

2. Description of the Related Art An optical pickup device is a device that optically records and reproduces information on a recording medium. Specifically, a light beam from a light source is directed onto the recording surface of the recording medium using an objective lens. The reflected beam, which is focused on the recording medium and reflected and modulated by the recording medium, is reflected by a beam splitter toward a photodetector, and is received by the photodetector to detect an optical signal.

Regarding this optical pickup device, for example, Japanese Patent Laid-Open No. 55-28593 discloses an optical system for reproducing information on a video disc and a focus control system for irradiating a laser beam onto the disc. , a control mechanism for tracking control and time axis correction is disclosed. As a mechanism for deflecting the laser beam in the tracking direction, a fixed mirror, a mirror, a pivot, and a mirror driver are provided, and the laser beam incident on the fixed mirror is reflected and incident on the mirror. - The laser beam is moved in response to a tracking error signal by a mirror driver fixed to one end of the mirror and a pivot serving as a support mechanism, thereby deflecting the laser beam in the radial direction of the disk. Furthermore, a configuration is also disclosed in which a drive mechanism for performing tracking control and a drive mechanism for correcting the time axis are disposed facing each other.

[0004] Furthermore, in order to miniaturize the optical pickup device, Kurt E. Petersen, “Silic
onTorsional Scanning Mirror
or”, IBM J. Res. Develop. Vol.
24. No. 5 discloses a method of integrally forming a movable mirror on a silicon substrate. However, when a mirror is formed on a semiconductor substrate, the stroke of the mirror is so small that it is difficult to obtain a sufficient deflection angle. Therefore, as a method to obtain a large deflection angle even when the stroke of the mirror is small, a piezoelectric sensor, such as the one introduced in Tatsuatsu Honda's "Light Deflection and Display Technology" (Electronics Magazine, September 1969), has been proposed. A multiple reflection method using a plurality of piezoelectric elements and mirrors can be considered.

[0005]

[Problem to be Solved by the Invention] When deflecting a laser beam using a movable mirror in an optical pickup device,
It is required to obtain a sufficient deflection angle. In other words, if the deflection angle is small, the movement range of the laser beam on the recording medium will not be sufficient, and if the eccentricity of the disk is large, tracking control will not be possible. On the other hand, if an attempt is made to increase the deflection angle, the mirror drive mechanism becomes large, making it difficult to downsize the pickup device. In order to reduce the size of the pickup device, a structure is adopted in which a movable mirror for deflection is provided on the semiconductor substrate.
The movable range is small and it is difficult to obtain a sufficient deflection angle. Therefore, a method is adopted in which a plurality of mirrors are provided to cause multiple reflections.

By the way, when constructing an optical pickup device on a semiconductor substrate, it is desirable to provide the movable mirror and the light receiving element on the same semiconductor substrate, taking into consideration manufacturing aspects such as optical axis alignment. However, as disclosed in the above-mentioned "Light Deflection and Display Technology," in a device that combines a piezo element and a mirror, if the piezo element is mounted on a semiconductor substrate and is oscillated in the same phase, the amount of deflection is determined by mirrors that can be moved on both sides. There is a problem that only half of the result is obtained compared to the configuration with −. Furthermore, when a configuration is adopted in which a piezo element and a mirror are combined, the optical path length changes simultaneously with the deflection of the laser beam, so the laser beam must be parallel light. Therefore, a collimating lens for collimating the laser beam must be disposed in the optical path, making it difficult to downsize the optical pickup device.

The present invention was proposed in order to solve the above-mentioned problems, and an object of the present invention is to provide an optical pickup device that can obtain a sufficient deflection angle even though the entire device is small.

[0008]

[Means for Solving the Problems] In order to achieve the above object, the present invention provides a plurality of rotary motions capable of moving a laser beam from a semiconductor laser in a direction transverse to an information track of a recording medium. A mirror, a semiconductor substrate on which a light receiving element for detecting the laser beam is formed, a semiconductor laser serving as the light source, and a mirror that transmits a portion of the laser beam and reflects a portion of the laser beam. The optical pickup device is characterized in that a prism and a fixed mirror facing the rotating mirror are integrally provided.

[0009]

[Operation] As described above, multiple rotating mirrors, light receiving elements,
Since the semiconductor laser, prism, and fixed mirror are integrally provided, it is possible to provide an optical pickup device that is small but has a sufficient deflection angle.

0010

Embodiments Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is a longitudinal sectional view of an optical pickup device according to a first embodiment of the present invention, and FIG. 2 is a plan view of a semiconductor substrate. Rotating mirrors 2 and 3 for deflecting a laser beam are provided on the upper surface of the semiconductor substrate 1 by etching or the like so as to be spaced apart from each other on one side in the length direction. Also,
A light receiving element 4 for detecting the output of the semiconductor laser and a light receiving element 5 for detecting the information reproduction signal and the tracking error signal are arranged on the upper surface of the semiconductor substrate 1 toward the other side in the length direction of the semiconductor substrate. are located separately from each other. Further, a semiconductor laser 6 is mounted and fixed between the rotating mirror 2 and the light receiving element 5, and a prism 7 is mounted and fixed in the area of the semiconductor substrate 1 where the light receiving elements 4 and 5 are provided. The prism 7
A fixed mirror 8 is provided on the upper surface of the mirror so as to face the rotating mirrors 2 and 3.

To explain the operation of this embodiment configured as described above, a part of the laser beam emitted from the semiconductor laser 6 is incident on the surface of the semiconductor laser 6. The light passes through the surface of the prism 7, which has a coating that allows a part of the light to pass through, is guided to the light receiving element 4, and the amount of light is detected for controlling the output of the semiconductor laser 6. Note that an output control circuit for the semiconductor laser 6 is not shown. The laser beam reflected by the surface of the prism 7 is reflected by a fixed mirror 8, and then by a rotating mirror 2 for deflection. The laser beam reflected by the rotating mirror 2 is reflected again by the fixed mirror 8, reflected by the other deflecting rotating mirror 3, and guided to the condenser lens 9, through which it is transmitted. The light is focused on the 10th surface of the recording medium.

Next, the laser beam reflected by the surface of the recording medium 10 passes through the condensing lens 9 and then passes through the rotating mirror 3, the fixed mirror 8, the rotating mirror 2, and the fixed mirror 8. The light is sequentially reflected in this order, passes through the surface of the prism 7, and is guided to the light receiving element 5. Then, an information reproduction signal and a tracking error signal are detected. To deflect the laser beam, rotating mirrors 2 and 3 are driven in the same direction, and by driving the two rotating mirrors in this way, the deflection angle of the laser beam can be increased. .

In this embodiment, since the two rotating mirrors 2 and 3 and the light receiving elements 4 and 5 are provided on the same semiconductor substrate 1, the work of attaching these elements is required when manufacturing the entire optical pickup device. In addition, optical axis alignment can be easily performed. In addition, since the laser beam is deflected by multiple rotating mirrors, a large polarization angle can be obtained, and since the optical path length does not change due to deflection, it can be applied to finite optical systems, so a collimating lens is not required. be.

In this embodiment, the mirrors that form the movable mirrors 3 and 4 and the actuators that drive them are formed by etching, etc., and their specific structure will be explained with reference to FIG. explain. FIG. 8 is a cross-sectional view, in which the movable part 2 is centered around a rotating shaft 2a provided parallel to the surface of the semiconductor substrate 1.
b is rotatably provided, and a reflective film 2 is provided on the surface of this movable part 2b.
c to act as a mirror. An electrode 2d is formed on the back surface of the movable part 2b. On the other hand, two opposing electrodes 2e and 2f separated about the rotation axis 2a of the movable part 2b are formed on the surface of a glass substrate 30 located below the movable part 2b and pointing to the mirror.

To explain the operation of the actuator thus constructed, first, a voltage based on a tracking error signal is applied to the electrode 2e and the electrode 2d attached to the back surface of the movable part 2b. Electrostatic attraction is generated between the electrode 2d and the counter electrode 2e, and the mirror 2 rotates in the direction shown by arrow A. On the other hand, when a voltage based on the tracking error signal is applied to the opposing electrode 2f and the electrode 2d in the same manner as described above,
Mirror 2 rotates in the direction shown by arrow B. By rotating the mirror 2 in this way, the traveling direction of the laser beam reflected by the mirror 2 is changed to deflect the laser beam.

FIG. 3 shows a second embodiment of the present invention.
The same reference numerals are given to parts corresponding to those in the first embodiment. In this embodiment, the semiconductor laser 6 serving as the light source is a surface-emitting type semiconductor laser, and is provided on the upper surface of the semiconductor substrate 1. The laser beam from this semiconductor laser 6 is directed to the semiconductor substrate 1.
The prism 7, which emits light in a direction perpendicular to the upper surface thereof and is placed and fixed on the semiconductor substrate 1, is a semiconductor laser beam capable of transmitting and reflecting the laser beam from the semiconductor laser 6. It is formed to have a surface opposite to the upper surface of the substrate 1. The other configurations are almost the same as in the first embodiment.

To explain the operation of this embodiment configured as described above, a part of the laser beam emitted from the surface-emitting type semiconductor laser 6 is directed onto the upper surface of the semiconductor substrate 1 of the prism 7. The light passes through the opposing surfaces, is reflected by the fixed mirror 8, and is guided to the light receiving element 4, where the amount of light is detected for semiconductor laser output control. On the other hand, a part of the laser beam reflected on the surface of the prism 8 is guided to the rotating mirror 2 and reflected, further guided to the fixed mirror 8 and reflected, and then reflected by another rotating mirror. -3, is reflected, and is condensed onto the recording medium 10 via the condensing lens 9.

The laser beam reflected by the recording medium surface 10 passes through the condenser lens 9, is guided to the rotary mirror 3, is reflected, and is further guided to the fixed mirror 8, and is reflected. ,
Furthermore, it is guided to the other rotary mirror 2 and reflected, transmitted through the surface of the prism 7, reflected by the fixed mirror 8, and then guided to the light receiving element 5 where information reproduction signals and tracking error signals are transmitted. Detection takes place.

In this embodiment, as described above, the rotating mirrors 2 and 3 are
, in addition to the light receiving elements 4 and 5, the semiconductor laser 6 is also mounted on the semiconductor substrate 1.
Therefore, when manufacturing the entire optical pickup device, it is not necessary to attach the rotary mirrors 2, 3 and the light receiving element 4, and the optical axis can be easily aligned. Furthermore, mounting and positioning of the semiconductor laser 6 is no longer necessary. Furthermore, as in the first embodiment, since the laser beam is deflected by a plurality of rotating mirrors, a large polarization angle can be obtained.

In this embodiment, a surface-emitting laser is used as the semiconductor laser.
The QW is formed of five quantum well layers and four barrier layers, a second-order diffraction grating is used, and the external waveguide section returns light to the laser section and acts as a surface emitting section. In addition, the surface-emitting laser of the type with a 45° mirror end face is compliant with the JIS standard suitable for integration.
It is a combination of structure and structure. These surface-emitting lasers are disclosed in the proceedings of the 34th Applied Physics Conference, the 37th Applied Physics Conference, and the like.

FIG. 4 shows another embodiment of the optical pickup device, in which a second semiconductor substrate 11 is attached to the first semiconductor substrate 1 in place of the fixed mirror 8 in each of the embodiments according to the present invention. A rotating mirror 2 is provided on the lower surface of the second semiconductor substrate 11 so as to be opposed to each other. Except for the fact that only one rotating mirror 3 is provided on the upper surface of the first semiconductor substrate 1, the structure of the other optical elements provided on this semiconductor substrate 1 is the same as that of the first embodiment. It is similar to

To explain the operation of this embodiment configured as described above, first, the laser beam emitted from the semiconductor laser 6 is
A portion of the beam passes through the surface of the prism 7, is guided to the light receiving element 4, and the amount of light is detected for controlling the output of the semiconductor laser 6. Laser beam reflected on the surface of prism 7
The beam is guided and reflected by a rotary mirror 2 provided on the second semiconductor substrate 11, further guided and reflected by another rotary mirror 3, and then directed to a recording medium via a condenser lens 9. The light is focused on 10 planes. In this case, the deflection angle of the laser beam is increased by driving the rotating mirrors 2 and 3, but this can be done by driving them in opposite directions. For example, if it is desired to deflect the laser beam counterclockwise, the rotating mirror 2 should be driven clockwise and the other rotating mirror 3 should be driven counterclockwise.

[0023] The radiation thus reflected on the 10 surfaces of the recording medium
After passing through the condensing lens 9, the beam passes through the rotating mirror 3.
, the rotating mirror 2, and are transmitted through the surface of the prism 7 and guided to the light receiving element 5. Then, an information reproduction signal and a tracking error signal are detected.

In this embodiment, as described above, since the two rotary mirrors 2 and 3 are provided to face each other, the same deflection angle can be obtained with a smaller device. Therefore, in the first and second embodiments of the present invention, the deflection angle of the laser beam can be increased by providing a rotating mirror in place of the fixed mirror. Note that since the rotating mirror 3 and the light receiving elements 4 and 5 are provided on the same semiconductor substrate,
Needless to say, when manufacturing the entire optical pickup device, there is no need to attach these elements.

Next, the operation of the drive system when tracking is performed using the optical pickup device will be explained. FIG. 5 is a block diagram illustrating an optical pickup device according to the present invention. First, the amount of deviation of the light spot from the information track on the recording medium is determined by the tracking error detection means 1.
The output from the tracking error detection means 12 is input to the phase compensation means 13 for improving the characteristics of the control system. The output from the phase compensation means 13 becomes a drive signal for the rotating mirror. Further, the drive signal is amplified by the driver 14 to drive one rotating mirror 16, and the other driver 15 drives the other rotating mirror 17.

FIG. 6 is a block diagram illustrating another embodiment of the optical pickup device. In this embodiment, since the rotating mirrors are provided facing each other, they must be driven in opposite directions. Therefore, the drive signal that is the output from the phase compensation means 13 is applied to one of the rotating mirrors.
In order to drive 16, it is necessary to invert the sign of the output with inverter 18. The other rotating mirror is directly driven via a driver 15 by a drive signal from the phase compensation means 13.

FIG. 7 shows an embodiment of the tracking error detection means, which uses a push-pull method. The two regions 5a and 5b of the light receiving element 7 are divided in the direction along the information track on the recording medium. When the light spot deviates from the information track on the recording medium, the area 5a,
Since the intensity of reflected light incident on 5b becomes unbalanced,
A tracking error signal (TES) can be obtained by calculating the difference using an amplifier 19. Further, by calculating the sum of the regions 5a and 5b using the amplifier 20, an information reproduction signal (RF) can be obtained. Note that when tracking is performed using the sample servo method, the tracking error signal can be obtained only from the intensity signal of the reflected light, so it goes without saying that there is no need to divide the light receiving element 7 into two regions. do not have.

[0028]

As described above, according to the present invention, a plurality of rotating mirrors, light receiving elements, or semiconductor lasers are provided on the same semiconductor substrate, so that when manufacturing the entire optical pickup device, it is possible to Does not require work to attach elements,
Further, optical axis alignment and positioning can be easily performed. In addition, since the laser beam is deflected by multiple rotating mirrors, a large polarization angle can be obtained, and the optical path length does not change due to deflection, making it applicable to finite optical systems and eliminating the need for collimating lenses. Become.

[Brief explanation of the drawing]

FIG. 1 is a longitudinal sectional view of a device according to a first embodiment of the present invention.

FIG. 2 is a plan view of a semiconductor substrate.

FIG. 3 is a longitudinal sectional view of a device according to a second embodiment of the invention.

FIG. 4 is a longitudinal cross-sectional view of a device according to another embodiment.

FIG. 5 is a block diagram of a drive system according to the present invention when tracking is performed.

FIG. 6 is a block diagram of another drive system when tracking is performed.

FIG. 7 is an embodiment diagram of a tracking error detection means.

FIG. 8 is an enlarged sectional view of the vicinity of a rotating mirror used in each embodiment.

[Explanation of symbols]

1 Semiconductor substrate 2 Rotating mirror 3 Rotating mirror 4 Photo-receiving element 5 Photo receiving element 6 Semiconductor laser 7 Prism 8 Fixed mirror 9 Objective lens 10 Recording medium

Claims (1)

[Claims] 1. A plurality of rotating mirrors capable of moving a laser beam from a semiconductor laser in a direction across an information track of a recording medium, and a light receiving element for detecting the laser beam. a semiconductor substrate formed on the surface thereof, a semiconductor laser serving as the light source, a prism that transmits part of the laser beam and reflects part of the laser beam, and a fixed mirror facing the rotating mirror. An optical pickup device characterized in that: and are integrally provided.