JPS62234243A - Optical pickup device - Google Patents

Abstract

PURPOSE:To miniaturize a device and to thinning it and to make accurate tracking servo possible by driving the whole of an optical system two- dimensionally through a substrate on which optical elements constituting the going and returning path optical systems of a laser beam are integrated and arranged. CONSTITUTION:An optical pickup chip 30 where a semiconductor laser 34, photodetectors 37 (37a-37d), etc., as optical elements constituting the going and returning path optical systems of the laser beam are integrated on a substrate 31 is subjected to servo in the focusing direction and the tracking direction through an electromagnetic driving system. Consequently, the optical axis of the going path to a disk of the emitted light from the laser 34 and that of the returning path optical system which leads the return light from the disk to photodetectors are not shifted to surely perform the following-up control of the beam spot. Since optical elements which are integrated on the substrate and constitute optical systems are directly driven in two orthogonal focusing and tracking directions, the whole of the device is made thin and compact to approximate to a disk more.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention is applied to optical discs such as DAD (Digital Audio Disc) and DRAW (Write Once Ready) disc, etc. for optically reproducing information or recording/recording. The present invention relates to an optical pick amplifier device that performs playback.

2. Description of the Related Art Conventionally, an optical pickup device has been configured as shown in FIG. 6, for example.

A semiconductor laser 2 is disposed on one side of the optical pickup device main body 1. The main body 1 includes a collimator lens 3 extending from the semiconductor laser 2 to the other side of the main body 1 . A beam splitter 4 and a 45 degree mirror 5 are provided. An objective lens 7 is supported on the other side of the main body 1 via a two-axis actuator 6 so as to face the disk medium. A photodetector 8 is disposed in the direction in which the return light from the disk medium is deflected via the beam splitter 4. This optical pickup device main body 1 is supported by a linear feed mechanism (not shown).

In this optical pickup device, a laser beam emitted from a semiconductor laser 2 is transmitted through a collimator lens 3. The light is guided to an objective lens 7 via a half mirror 4 and a 45-degree mirror 5, and is focused onto a disk medium. A beam spot focused through the objective lens 7 is irradiated onto a row of information pits formed in the circumferential direction of the disk medium. The returned light from the disk medium is guided to a photodetector 8 via a beam splitter 4, where it is photoelectrically converted and information is read. At the same time, the photodetector 8 detects focus and tracking error No. 43. The two-axis actuator 6 is driven by this error signal, and the objective lens 7 is servoed in the focusing and tracking directions via the two-axis actuator 6. As a result, the beam spot is controlled to accurately follow the information focus row of the disk medium. The optical pink-up device linearly feeds the disk medium in the radial direction via a linear feed mechanism, and focuses a beam spot through an objective lens 7 from the information pit row at the innermost circumference of the disk medium to the outermost circumference. The range of information pit rows located on the disk is accessed in the radial direction of the disk medium.

As described above, in the conventional optical pickup device, the objective lens 7 is supported by the two-axis actuator 6, and by driving this actuator 6, the objective lens is servoed in orthogonal two-dimensional directions, and the beam spot is aligned with the information pits on the disk medium. A configuration in which control was performed to follow the train was common.

Problems to be Solved by the Invention However, in a conventional optical pickup device having a structure in which the objective lens 7 is driven two-dimensionally via a two-axis actuator, the objective lens 7 is moved to a disk in order to control the beam spot in the tracking direction. When the medium is driven in the radial direction, a deviation occurs between the optical axis of the output from the semiconductor laser 2 and the optical axis of the return light from the disk medium, and the optical axis of the return optical system passes through the center of the objective lens. The problem arises that the photodetector deviates from the central axis of the photodetector. In particular, when the surface runout or eccentricity of the disk medium is large, the tracking characteristics deteriorate due to the deviation of the optical axis, causing a problem that the tracking servo by the two-axis actuator 6 cannot be performed accurately.

Furthermore, in conventional optical pickup devices, the optical components such as the semiconductor laser, collimator lens, beam splitter, 45-degree mirror, and photodetector that make up the optical system are individually arranged on the opto base. In addition, since the objective lens is supported on the opto base via a two-axis actuator, the device becomes large and cannot meet the demand for smaller and thinner devices.

The present invention has been made in view of the above points, and an object of the present invention is to make an optical pickup device smaller and thinner, and at the same time, to enable accurate tracking servo at all times.

Means for Solving the Problems In order to achieve the above object, the present invention provides optical elements constituting the forward and return optical systems for laser light emitted from a semiconductor laser, such as a semiconductor laser and a light receiving element, on a substrate. A configuration was adopted in which the entire optical system was two-dimensionally driven in two orthogonal axes directions of focusing and tracking via this substrate.

According to the present invention, each optical element constituting the optical system is integrated and arranged on a substrate, and the optical system is two-dimensionally driven in two orthogonal two-axis force directions for focusing and tracking via this substrate. , the overall thickness of the optical pink-up device becomes thinner.

In addition, the outgoing optical axis from the semiconductor laser to the disk medium always matches the optical axis of the returning light from the disk medium, and the optical axis of the returning light always matches the optical axis of the returning optical system passing through the center of the objective lens. The tracking servo is performed in accordance with the misalignment.

Embodiments Hereinafter, embodiments of the present invention will be described with reference to the drawings of FIGS. 1 to 5.

FIG. 1 is a perspective view showing an optical pink-up device according to the present invention, and FIG. 2 is an exploded perspective view thereof.

A pair of guide shafts 10.degree. 10 are arranged parallel to the disk D in the optical disk player main body (not shown). The optical pickup device includes a guide shaft 10.
10 so as to be slidable. The optical pickup device is linearly fed in the radial direction of the disk D along the guide shaft 10.10 via a linear feeding mechanism (not shown).

At both ends of the main base 20 of the optical pink amplifier device,
A bearing part 21.21 is formed. main base 20
The bearings 21.21 are mounted on the guide shafts to, 10, respectively. A magnetic circuit 24 consisting of a yoke body 22 and a permanent magnet 23 is provided on the main base 20. The yoke body 22 consists of a cylindrical rising inner wall 221 and a pair of arc-shaped rising outer walls 222, 222 facing each other at an interval of 180 degrees on the outside of the cylindrical rising inner wall 221.
1 and the inner surfaces of the outer walls 222, 222 with a gap at a constant interval. Permanent magnets 23 and 23 are attached to the inner surfaces of the outer walls 222 and 222 of the yoke body 22, respectively, with a gap at a constant interval from the outer peripheral surface of the inner wall 221. Inner and outer walls 221 and 22 of the yoke body 22
2,222 and permanent magnets 23 and 23 form a magnetic circuit 24.
is formed.

A bearing portion 25 is provided at the center of the yoke body 22 . A holder 26 is supported by the bearing portion 25 so as to be vertically movable and rotatable. The holder 26 is formed into a flat plate shape, and has a shaft 261 projecting downward from the center of its lower surface. A shaft 261 of this holder 26 is attached to the bearing portion 25 so as to be vertically movable and rotatable. Thereby, the holder 26 is supported by the bearing portion 25 so as to be vertically movable and rotatable. On the lower surface of the holder 26, a focus control excitation coil 27 wound into a cylindrical shape is formed around a shaft 261. A pair of tracking control coils 28 wound in the shape of a flat frame are attached to the outer peripheral surface of the focus control excitation filter 27 at an interval of 180 degrees. The focus and tracking control excitation coils 27 and 28 are installed in the gap between the yoke inner wall 221 of the magnetic circuit 24 and the permanent magnets 23 and 23. In addition, the tracking control coil 28
is arranged so that only approximately half of the frame-shaped magnetic circuit 24, including one rising portion, extends over the gap between the magnetic circuits 24. Furthermore, a pin 262 is provided at one end of the holder 26 to project downward. A pin 201 is also provided upright at the end of the main base 20 corresponding to this pin 262.

Pin 262 of holder 26 and pin 2 of main base 20
A damper member 29 made of a rubber material or the like is attached to the holder 26. The holder 26 is always held at a neutral position by the damper member 29.

On the holder 26 is an optical pick amplifier chip 3, which will be described later.
0 is installed. Note that in the drawings, a lead wire that guides the electrical signal charged and converted by the photodetector to the signal processing circuit and a signal processing circuit that processes the electrical signal are not shown. The lead wires connecting the holder 26 and the main base 20 and the main base 20 and the player body (not shown) are flexibly wired so as not to hinder the driving of the optical pickup device.

Optical pickup chip 30 mounted on holder 26
is a rectangular plate-shaped substrate 3 made of n-type silicon (St) or the like.
1, a buffer layer 32 made of silicon dioxide (SiOz) or the like and a waveguide layer 33 made of glass material or the like are laminated to have a March structure. A semiconductor laser 34 is attached to the center of one short side of the substrate 31. Laser light emitted from the semiconductor laser 34 enters the optical waveguide made of the waveguide layer 33. On the other short side of the substrate 31, a waveguide beam splitter 35. A condensing diffraction grating 36 is formed in an integrated manner. This waveguide beam splitter 35. The diffraction grating pattern of the condensing diffraction grating 36 is formed of silicon nitride (SiN). Furthermore, the substrate 31
On one side near the upper semiconductor laser 34, a total of four photodiodes 37 are arranged, one pair on each side on the left and right, sandwiching the optical axis of the laser light emitted from the semiconductor laser 34 and input into the optical waveguide 33. (See Figure 3).

As described above, the optical pickup chip 30 includes the substrate 31
Optical waveguide 33. Waveguide beam splitter 35. The condensing diffraction grating 36 and the photodiode 37 are integrated and formed into one body.

Laser light emitted from the semiconductor laser 34 is guided to a condensing diffraction grating 36 via a waveguide beam splitter 35, irradiated above the substrate 31 in a substantially pyramidal shape, and condensed onto a disk medium. The returned light of this focused beam spot from the disk D is returned to the waveguide beam splitter 35 via the focusing diffraction grating 36, and is sent to the left photodiodes 37a, 37b and the right photodiode 37.
It is separated and guided in two directions: c + 37 d. The photodiode 37 outputs the playback signal and the focus signal.
A tracking error signal is detected (see FIG. 3).

The reproduction signal is detected by a photodiode 37a.

This is performed by summing the detection outputs of 37b, 37c, and 37d. The reproduction signal is obtained by taking the difference in the detection output of the incident light caused by the increase or decrease in the amount of light incident on the photodiode 37. The focus error signal is detected by the outer photodiodes 37a and 37d.
and the inner photodiode 37b,
This is done by differential output with the sum of the detection outputs of 37c. In that case, depending on the distance between the disk D and the optical pickup chip 30, the outer photodiode 37a,
Amount of light incident on 37d and inner photodiode 37
There is a difference in the amount of light incident on 37b and 37c, and a focus error signal is obtained by detecting this difference.

As the disk D approaches the optical pickup device, the amount of incident light 1 entering the outer photodiodes 37a and 37d increases, and as the disk I moves away, the amount of incident light entering the inner photodiodes 37b and 37c increases. When focusing, the left and right photodiodes 37a, 3
The amount of light incident on 7d, 37b, and 37c becomes equal.

The tracking error signal is detected by differential output between the sum of the outputs of the left photodiodes 37a and 37b and the sum of the outputs of the right photodiodes 37c and 37d. When a track shift occurs in the beam spot, a difference occurs in the amount of incident light on the left and right photodiodes, which should be symmetrical, and a tracking error signal is obtained by detecting this difference in the amount of incident light on the left and right photodiodes.

The tracking error signal is detected when the beam spot illuminates the information focus row formed on the disk D. Detection of the focus error signal is performed when irradiating a position where there are no pits. Switching of the detection operation between the focus error signal and the tracking error signal is performed by, for example, switching a switching circuit using a pulse signal that is converted by comparing the reproduced signal.

The focus and tracking error signals obtained as described above are input to the drive amplifier via the respective phase compensation circuits.

The signal from this drive amplifier becomes a drive signal for driving the electromagnetic drive system described above. In response to this drive signal, the electromagnetic system is driven, and the optical pick-up knob chip 30 is servoed in the focusing and tracking directions via the holder 26. As a result, the spot of the laser beam focused on the disk D is controlled to follow correctly in the focus and tracking directions.

As described above, according to the optical pickup device of this embodiment, the optical pick-up knob 30, which has optical elements constituting the optical system integrated on the substrate, is servoed in the focusing and tracking directions via the electromagnetic drive system. Therefore, the return light from the optical axis of the forward path emitted from the semiconductor laser 34 and reaching the disk D and the optical axis of the disk I is guided to the photodetector (there is no scratching with the optical axis of the return path optical system. Even if the tracking servo of the pickup device is performed while the pink amplifier unit is addressed in a state corresponding to the information focus row of disk D, there is no worry that the optical axis will shift and the tracking characteristics will deteriorate. Beam spot tracking control is possible.

Furthermore, according to the device of this embodiment, the optical elements constituting the optical system are integrated on the substrate, and are directly driven by the electromagnetic drive system in two-dimensional directions orthogonal to focusing and tracking, so that the entire device can be It has a thinner and more compact structure that is closer to that of disk D.

As described in detail, according to the optical pickup device of the present invention, the entire optical elements constituting the optical system, such as the conductor laser and the light receiving element, are driven two-dimensionally, so even when tracking servo is applied, Servo can be performed while the forward optical axis from the semiconductor laser to the disk medium and the return optical axis of the return light from the disk medium are always aligned without any misalignment.

Therefore, impressive tracking servo can be performed without deteriorating tracking characteristics. Further, according to the present invention, the entire optical pickup in which the optical elements are integrated is directly driven in two orthogonal directions, so that the device can be made smaller and thinner. Incidentally, the pickup device to which the present invention is applied is 1.
It has been made about 15 times smaller and thinner.

[Brief explanation of drawings]

FIG. 1 is a perspective view showing an optical pink-up device according to the present invention, FIG. 2 is an exploded perspective view thereof, and FIG. 3 is an illustration of an integrated optical pickup chip to which the present invention is applied, and the detection of signals thereof. FIG. 4 is a side view showing the operation of the focus servo of the optical pink-up device according to the present invention, FIG. 5 is a perspective view showing the operating state of the tracking servo, and FIG. 6 is the conventional system. 1 is a perspective view showing an optical pickup device of FIG. 10...Guide shaft, D@-disc. Figure 2

Claims (3)

[Claims] (1) Laser light emitted from a semiconductor laser is focused and irradiated onto a disk medium, and the return light from the disk medium is guided to a light receiving element to reproduce or record/reproduce optical information from the disk medium. In an optical pickup device, optical elements such as a semiconductor laser and a light-receiving element that constitute the forward and return optical systems of the laser beam are integrated and arranged on a substrate, and the entire optical system is focused and tracked via this substrate. An optical pickup device characterized by two-dimensional driving in two axial directions. (2) On the substrate, an optical waveguide that guides the laser light from the semiconductor laser, a focusing diffraction grating that focuses the laser light on the disk medium, a light receiving element that receives the laser light guided through the optical waveguide, etc. are integrated. 2. An optical pickup device according to claim 1, wherein an optical system is formed by using an electromagnetic drive system. (3) The optical system element is supported vertically and rotatably via a holder, and the optical system element is moved in orthogonal two-dimensional directions by an electromagnetic drive system consisting of an excitation coil for focus and tracking control and a magnetic circuit. An optical pickup device according to claim 1 or claim 2, characterized in that the optical pickup device performs focus and tracking servo.