JPH0476827A - Optical head - Google Patents

Abstract

PURPOSE:To lighten a movable optical part and to present the optical head reducing the occupied area of a fixed optical part by using a uniaxial actuator to move a convergence function element only in an optical axis direction for the movable optical part. CONSTITUTION:A light beam emitted from a semiconductor laser 10 is made incident through a collimating lens 11 and a composite prism 14 on an oscillating mirror 20. The light beam is bent at 90 deg., passed through the inside of a carriage 4 and made incident on a movable optical part 2. The light beam is converged through a reflection mirror 7 and a convergent lens 5 so as to irradiate the surface of a disk 1. The reflected light beam is moved backward, reflected by a beam splitter 23, afterwards made incident through the convergent lens 5 on a detection optical system 19, passed through a polarized beam splitter 16 and detected by tripartite photodetectors 17 and 18.

Description

[Detailed Description of the Invention] [Objective of the Invention] (Industrial Application Field) This invention relates to optical recording of information on an optical recording medium using an optical head, and optical recording of recorded information. Regarding the optical recording and reproducing device used for reproduction, for more details, please refer to the arrangement of the optical head and
It's about configuration.

(Prior art) An optical recording/reproducing device using an optical recording medium such as an optical disk is
Although it surpassed other information storage devices such as magnetic disk drives in terms of large capacity, it was inferior in terms of high-speed access.

The reason for this is that access is performed by moving a large and heavy optical head used for recording and reproducing information in a straight line. Conventionally, a method to solve this problem is to separate the optical head into a moving optical section that moves during access and a fixed optical section, and to reduce the weight of the moving optical section and thereby speed up access. It is being done.

An optical head having a movable optical section and a fixed optical section separated in this manner is described in, for example, Japanese Patent Laid-Open No. 63-214863. In this conventional optical head, a plurality of optical elements constituting a fixed optical system are arranged in a plane at the rear of a moving optical section. The light emitted from the fixed optical system is guided to a moving optical section consisting of a reflecting mirror and a focusing lens, and is irradiated onto the optical disk as a minute spot. The focusing lens is supported by a biaxial lens actuator and is movable in two directions: the optical axis direction and the direction perpendicular to the tracks on the optical disk.

Focus control is performed by moving the focusing lens in the optical axis direction, and tracking control is performed by moving the focusing lens in a direction perpendicular to the track.

However, in the conventional optical head which is separated into a moving optical section and a fixed optical section as described above, a biaxial lens actuator is used in the moving optical section, so the weight of the moving optical section cannot be reduced sufficiently.

Furthermore, since the fixed optical section is arranged in a planar manner, the fixed optical system occupies a large area within the optical disk device.

This is a major obstacle in achieving miniaturization by reducing the depth dimension, especially in optical disk devices that use small-diameter disks, such as 130 mm in diameter and 90 mm in diameter.

Although the functions required of an optical head are not directly related to the size of the optical disk, small-diameter disks require a small optical disk device commensurate with the disk diameter.

Furthermore, if a uniaxial lens actuator is used to reduce the weight of the moving optical section, the control function for the remaining one axis must be provided in the fixed optical section, making the fixed optical section even larger.

(Problems to be Solved by the Invention) As described above, in the conventional optical head in which a two-axis actuator is used for the moving optical section and the fixed optical section is arranged in a flat manner, the weight of the moving optical section cannot be sufficiently reduced. , which is an obstacle to speeding up access. Furthermore, since the fixed optical section occupies a large area, it is difficult to miniaturize the optical recording/reproducing apparatus, which becomes a problem especially when using a small optical recording medium.

The present invention aims to further reduce the weight of the moving optical section, and at the same time,
An object of the present invention is to provide an optical head in which the area occupied by a fixed optical part can be reduced.

[Structure of the Invention] (Means for Solving the Problems) In the optical head of the present invention, the moving optical section includes a focusing function element that focuses a light beam on an optical recording medium, and a focusing function element that focuses a light beam on an optical recording medium. It consists of a uniaxial actuator that moves the Furthermore, the fixed optical section has a swinging mirror that swings the light beam on the optical recording medium in a direction perpendicular to the tracks on the optical recording medium, and furthermore, this swinging mirror. A light transmitting optical system that transmits a light beam upwardly or downwardly to an oscillating mirror along a plane perpendicular to the optical axis of the light beam incident from a fixed optical section to a moving optical section, and reflection from an optical recording medium. It is constructed by arranging a detection optical system that guides light to a photodetector.

(Function) Since the actuator used in the moving optical section is a uniaxial actuator that moves the focusing functional element only in the optical axis direction, the moving optical section is lightened. This makes it possible to move the moving optical section at higher speed using a drive source such as a linear motor having the same driving force, thereby shortening the access time.

On the other hand, when a uniaxial actuator is used in the moving optical section, the fixed optical section has a new function of controlling the remaining uniaxial axis, that is, controlling the light beam irradiated onto the recording medium in a direction perpendicular to the track. Therefore, the fixed optical part becomes increasingly large in a simple planar arrangement. However, in the present invention, a swinging mirror for moving the light beam in a direction perpendicular to the track is provided at the light output end, and a light transmission optical system and a detection optical system are provided above or below the swinging mirror, which requires space in the height direction. Because the arrangement is effectively utilized, it occupies only a small space on a plane, and when the optical recording medium is a small-diameter optical disk, the optical recording/reproducing device can be made smaller to match the size of the medium. Become.

(Example) Hereinafter, the present invention will be described in detail with reference to the drawings.

1 is a perspective view showing a schematic configuration of the main parts of an optical disk device using an optical head according to an embodiment of the present invention; FIG. 2 is a perspective view showing the configuration of a fixed optical section in FIG. FIG. 3 is a diagram showing the configuration of the entire optical system including a moving optical section and a fixed optical section.

In FIG. 1, an optical disc 1 is rotationally driven by a motor (not shown) attached to a base 2. As shown in FIG. A linear motor 3 is mounted on the base 2 in a direction parallel to the optical disc 1 (radial direction of the optical disc 1).
A carriage 4 that is moved is provided. The carriage 4 includes a focusing lens 5 which is a focusing function element for irradiating a light beam onto the optical disk 1, and this focusing lens 5.
A moving optical section is mounted, which includes a lens actuator 6 for moving the lens in the optical axis direction for focus control, and a reflecting mirror 7 for changing the optical axis (see FIG. 3).

On the other hand, a fixed optical part 8 is arranged at the rear of the base 2, that is, on the opposite side to the side that supports the optical disc 1. As shown in FIG. 2, this fixed optical section 8 includes a light transmitting optical system 13 consisting of a semiconductor laser 11 as a light source and a collimating lens 12, a compound prism 14, and a condensing lens 1.
5. Polarizing beam splitter 16 and photodetector 17.18
The main components are a detection optical system 19 and an oscillating mirror 20. The semiconductor laser 11 is attached to the holder 10, and after its position is adjusted in a plane perpendicular to the optical axis of the collimating lens 12, it is fixed to the housing 9 of the fixed optical unit 8. The detection optical system 19 is attached to the housing 9 so as to be movable in the optical axis direction of the incident light beam.

The swinging mirror 20 is located at the light output end from the fixed optical unit 8 to the moving optical unit 2, and is supported by the housing 9 so as to be swingable in the direction of the arrow with the horizontal axis as a fulcrum. By being driven accordingly,
The light beam to the moving optical section 2 is swung in a direction perpendicular to the tracks on the optical disk 1 (radial direction of the optical disk 1). Tracking control is performed by this swing.

Of the fixed optical section 8, a light transmitting optical system 13 consisting of a semiconductor laser 11 and a collimating lens 12, a detection optical system consisting of a compound prism 14, a condensing lens 15, a polarizing beam splitter 16, and a photodetector 17, 18 Series 19
is located above the swinging mirror 20 and along a plane perpendicular to the optical axis of the light beam that enters the movable optical section 2 from the fixed optical section 8.

Next, the operation of the optical head of this embodiment will be explained. During recording or reproduction, the light beam emitted from the semiconductor laser 1o is made into parallel light by the collimating lens 11, and then enters the compound prism 14. The first surface of the composite prism 14 is the entrance surface 21, and is angled so that it has a beam shaping function that converts the light beam with an anisotropic intensity distribution emitted from the semiconductor laser 11 into an isotropic light beam. ing. The second surface of the composite prism 14 is a total reflection surface 22, and the light beam reflected here enters the swinging mirror 20 through a beam splitter 23 on the third surface. The light beam incident on the oscillating mirror 20 is bent by 90'' and exits, then travels along the radial direction of the optical disk 1, passes through the carriage 4, and enters the moving optical section 2.

The light beam that has entered the moving optical section 2 from the fixed optical section 8 is directed toward the optical disk 1 by the reflecting mirror 7, and is focused and irradiated onto the optical disk 1 as a minute spot by the focusing lens 5. The reflected light from the optical disk 1 returns through the condenser lens 5, passes through the reflecting mirror 7 and the swinging mirror 20, is reflected by the beam splitter 23 of the compound prism 14, and then passes through the condenser lens provided integrally with the compound prism 14. At step 15, the light becomes a focused light, and heads toward the detection optical system 19 while being focused.

In the detection optical system 19, the incident light beam is split into two beams by a polarizing beam splitter 16 installed at an angle of 45'' with respect to the polarization plane of the destination beam, and the light receiving surface is divided into three to perform photodetection. From the output of the photodetector 17.18, a known arithmetic circuit detects servo error signals such as a focus error signal and a tracking error signal, and also detects information signals recorded on the optical disc 1. You can obtain playback signals, etc.

As described above, the detection optical system 19 is configured to be movable in the optical axis direction of the incident light beam, and by moving in the optical axis direction, the detection optical system 19 is installed at the light output end of the compound prism 14 to the detection optical system 19. The position of the photodetector 1718 relative to the focal point of the condensing lens 15 can be adjusted. That is, in this embodiment, as a method of detecting focus error, the shape change of the light beam formed on the light receiving surfaces of the two photodetectors 17 and 18 placed before and after the focusing point of the focusing lens 15 is A differential detection method (known as beam size differential method) is used with photodetectors 17 and 18, which are photodetectors having divided light-receiving surfaces.

In addition, from the signal (total sum output) obtained by adding all the signals obtained from the two photodetectors 17 and 18, the optical disk 1
A reproduction signal of the information recorded as emboss information and reflectance changes can be obtained.

Further, from the result of subtracting the respective sum signals obtained from the two photodetectors 17 and 18, a reproduction signal (magneto-optical signal) of information recorded on a magneto-optical disk or the like is obtained.

Note that tracking error detection for controlling the tracking of the bit string on the optical disk 1 by the light beam can be obtained, for example, by detecting wobbled bits provided in an embossed manner on the optical disk 1 in advance.

That is, tracking error detection is performed by sampling the total output of the photodetector in the wobbled bit section and comparing the respective signal amplitudes.

In the optical head described above, the actuator that moves the focusing lens 5, which is the focusing function element, in the moving optical section is made uniaxial with only the actuator 6 that moves the focusing lens 5 in the optical axis direction.
By simplifying the moving optical section, the weight of the moving optical section can be reduced.

Therefore, when the driving force of the linear motor 3 is the same, the moving optical section can be moved faster than before, and the access time can be shortened.

Further, a swinging mirror 20 for moving the light beam in a direction perpendicular to the track is provided at the light beam output end of the fixed optical unit 8 to the moving optical unit, and is located above the swinging mirror 20. In a plane perpendicular to the optical axis of the light beam entering the moving optical part from the fixed optical part 8, a light transmitting optical system 1 is provided in areas A and B, which are divided into two by a plane passing through the optical axis and perpendicular to the optical disk 1.
3 and the detection optical system 19, the space in the height direction can be used effectively, and the space occupied in the horizontal direction (in a direction parallel to the optical disc 1) can be kept within the range of approximately the diameter of the optical disc 1. It becomes possible. As a result, when the optical disc 1 has a small diameter such as 13 mm or 90 mm, the entire optical disc device can be downsized to a size commensurate with the diameter.

In the above embodiment, the detection optical system 19 is provided with a polarizing beam splitter 16 and two sets of photodetectors 17 and 18 to obtain a focus error signal and a reproduction signal of magneto-optically recorded information. The system configuration is not limited to this, and other known configurations may be used depending on the optical recording medium used. For example, focus error detection is performed using one beam of a light beam split into two by a beam splitter, and focus error detection is performed using the other beam. A detection optical system configured to perform tracking error detection using a beam may also be used.

Further, in the above embodiment, the light transmitting optical system 13 and the detection optical system 19 are arranged above the swinging mirror 20, but it goes without saying that the same effect can be obtained even if they are arranged below the swinging mirror 20. In addition, the present invention can be implemented with various modifications without departing from the scope.

[Effects of the Invention] According to the present invention, by making the actuator used in the moving optical section uniaxial, the weight of the moving optical section can be further reduced and the access speed can be increased. Alternatively, by arranging the light transmission optical system and the detection optical system below, the area occupied by the fixed optical system can be effectively reduced, which is particularly effective for optical disk devices using small-diameter disks.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing a schematic configuration of an optical disk device using an optical head according to an embodiment of the present invention, FIG. 2 is a perspective view showing the detailed configuration of the fixed optical section in FIG. 1, and FIG. FIG. 2 is a diagram schematically showing the configuration of the entire optical system. 1...Optical disk 3...Linear motor 5...Focusing lens 6...Lens actuator 7...Reflector 8...Fixed optical section 11...Semiconductor laser 12...Collimating lens 13... ... Light transmission optical system 14 ... Composite prism 15 ... Condensing lens 16 ... Polarization beam splitter 17.18 ... Photodetector 19 ... Detection optical system 20 ... Oscillating mirror application Patent attorney Takehiko Suzue

Claims (3)

[Claims] (1) A movable optical section configured to be movable in a direction parallel to the optical recording medium and a fixed optical section configured separately, and for performing recording and reproduction by irradiating the optical recording medium with a light beam. In the optical head, the moving optical section has a focusing function element that focuses a light beam on the optical recording medium, and an actuator that moves this focusing function element in the optical axis direction, and the fixed optical section has the moving optical section. an oscillating mirror that is disposed at a light output end of the optical recording medium and that oscillates the light beam in a direction perpendicular to the track on the optical recording medium; A light transmitting optical system is arranged along a plane substantially orthogonal to the optical axis of the light beam incident on the optical section, and transmits the light beam to the swinging mirror, and a light beam reflected from the optical recording medium is transmitted to a photodetector. An optical head comprising a detection optical system for guiding the light. (2) The fixed optical section causes a light beam to enter the moving optical section along an optical axis parallel to the moving axis of the moving optical section, and the moving optical section makes the optical axis of the light beam incident from the fixed optical section align with the optical axis parallel to the moving axis of the moving optical section. 2. The optical head according to claim 1, further comprising an optical element having a function of converting the direction of the optical axis of the focusing function element. (3) The light transmission optical system and the detection optical system connect the optical recording medium to the optical recording medium along a plane substantially perpendicular to the optical axis of the light beam that enters the moving optical unit from the fixed optical unit. 3. The optical head according to claim 1, wherein the optical head is disposed in each region divided into two by orthogonal planes.