JPH02148419A - Optical head - Google Patents

Abstract

PURPOSE:To obtain mechanical response performance, which is compact, light and satisfactory, by fixedly arranging the mutual position relation of constituting elements in an optical head to a turn and arranging a turning shaft parallelly with the optical axis of an objective lens. CONSTITUTION:The mutual position relation of the constituting elements in the optical head, namely, an optical demultiplexer 4, an optical path transformer 6 and an objective lens 8 is fixedly arranged to the turn and a turning shaft 15 is parallel with the optical axis of the objective lens 8. Accordingly, the horizontal type head is formed and the tracking control of a track can be executed by turning the whole head around the prescribed turning shaft 15 by a fine angle. Thus, in comparison with the tracking drive of the whole head by a conventional linear system, etc., the optical head can be made compact and the follow-up ability can be improve.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a horizontal optical head including at least an optical demultiplexer, an optical path converter, and an objective lens. The present invention relates to an optical head that rotates the entire head around a predetermined rotation axis, that is, a so-called horizontal head-driven optical head.

[Prior Art] Conventionally, optical heads have been classified according to the positional configuration of an optical system within the head, and other classifications according to differences in the control method of a light beam for positioning the optical head. According to the former classification, a so-called vertical optical head, in which the light beam emitted from a light source such as a laser diode runs approximately perpendicular to the surface of the optical disk until it irradiates an optical recording medium such as an optical disk; The surface formed by the optical path passing through the splitter is horizontal to the disk surface, and this horizontally running light beam is bent 90 degrees with a mirror or the like just before the objective lens to make the optical path perpendicular to the optical disk surface. There is a so-called horizontal optical head. According to the latter classification, there are an objective lens drive type and a head drive type.

Normally, optical disk devices have the disadvantage that the above-mentioned vertical optical head assembly protrudes perpendicularly to the disk surface in order to irradiate a beam perpendicularly to the optical disk, resulting in an increase in the size of the entire device. On the other hand, with a horizontal optical head, the optical helad is placed parallel to the disk surface, which avoids the drawback of increasing the size of the entire device, but the optical path becomes complicated, making it difficult to perform focusing and tracking. The disadvantage is that the light beam control becomes complicated.

In addition, in the objective lens driven type, focusing servo,
When controlling the light beam for tracking servo, the objective lens is moved, and in the head-driven type, the objective lens is moved for focusing, and the entire head is moved for tracking.

Since the objective lens drive type moves only the objective lens, there is a problem in that the positional relationship between the objective lens and other components (for example, a beam distributor) changes during tracking. In other words, in this objective lens drive type, the reflected light from the recording medium fluctuates with the movement of the objective lens, so when the push-pull method is used as the track position detection method, there is an error in the track position detection signal. arise. If a three-beam method other than the push-pull method is used as a track position detection method, it will not be affected by the beam shift described above, but since an offset will occur between the front and rear beams during writing, write-once or erasable type Not suitable for optical discs.

Therefore, from the viewpoint explained above, it can be said that the horizontal head-driven optical head is superior in principle in terms of miniaturization and no offset in focusing/tracking. As a conventional example of such an optical head, for example, Japanese Patent Application Laid-Open No. 61-280030
Yaji Kaisho 61-189417. Utsukai Showa 61-19551
There is an 8th grade.

Among these, in particular, JP-A-61-280030 moves the optical head back and forth linearly in the radial direction of the disk, and JP-A-61-189417°61-195518 moves the entire optical head around a predetermined rotation axis. Tracking is performed by rotating the

By the way, tracking in a broad sense requires two types of control: head feeding (seek operation) and track control (tracking in a narrow sense). Hereinafter, in this specification, tracking refers to tracking in a narrow sense for following a track. Of the three prior art techniques mentioned above, Japanese Patent Application Laid-Open No. 61-280030 involves linearly moving the optical head back and forth in the radial direction of the disk to perform seek operations and tracking. Also, Utsukai Showa 61-
189417. Utility Model Application No. 61-195518 discloses a system in which the entire optical head is rotated around a predetermined rotation axis to perform seek operations and tracking.

[Problem to be solved by the invention] With such a head-driven optical head, head feeding (
If seek operation) and track control (tracking) are performed by the same mechanism, for example, Japanese Patent Laid-Open No. 61-28003
0, a high output linear motor is required to follow up to a high drive frequency. Also, Utsukai Showa 61-189
417.61-195518, the larger the rotation angle, the less the direction of the tracking operation is perpendicular to the track direction.

Also, Utsukai Showa 61-189417.61-195518
However, since the seek operation is also performed by rotating the entire head, there is a fatal drawback that the distance between the center of rotation and the objective lens becomes long. For that purpose,
-189417.61-195518, a counterweight is provided on the opposite side from the objective lens to balance the entire head. However, providing such a counterweight makes the entire head heavy, resulting in decreased responsiveness to tracking.

Therefore, the inventor of the present application found the problem in the following points.

If the purpose is simply to feed the head, a linear motor is not required to have performance in a high drive frequency range, so the drive for head feeding is left to some means outside the optical head, and the drive for head feeding is simply performed within the optical head. The head is driven for tracking in a narrow sense. Moreover, if the head is driven for tracking by rotating the entire head by a minute angle around a certain center of rotation, the tracking direction will be perfectly aligned with the track compared to the linear method. Although it is not perpendicular to
For practical purposes, sufficient tracking control becomes possible. Also,
There is no need for a long swing arm like the one shown in Utility Model Application No. 61-189417゜61-195518.

Therefore, the present invention was proposed in order to eliminate the drawbacks of the above-mentioned prior art, and its purpose is to provide a horizontal head-driven optical head in which head feeding and track following control are performed by different mechanisms, The object of the present invention is to provide an optical head that is small and lightweight and can obtain good mechanical response performance.

A further object of the present invention is to propose an optical head that actively eliminates various minor problems associated with achieving track following control only by rotating the optical head.

[Means for Achieving the Objects and Their Effects] The configuration of the present invention for achieving the above objects includes head feeding and track following in a horizontal optical head that includes at least an optical demultiplexer, an optical path converter, and an objective lens. An optical head in which control is performed by different mechanisms and the entire head is rotated by a small angle around a predetermined rotation axis in order to perform track following control, and the mutual positional relationship of the above-mentioned components of the optical head is It is characterized in that it is arranged fixedly with respect to the rotation, and the rotation axis is parallel to the optical axis of the objective lens.

Since the rotation axis is parallel to the optical axis of the objective lens, a horizontal head is realized. Further, track following control is realized by rotating the entire head by a small angle around a predetermined rotation axis.

[Embodiments] Two embodiments to which the present invention is applied will be described below with reference to the attached drawings. The first embodiment is a horizontal head-driven optical head, in which the head is driven for tracking control by rotating the entire head. In addition, the second embodiment solves the problem of the mismatch between the center of rotation and the center of gravity of the head inherent in the first embodiment, and further improves the mechanical response to the tracking head drive than the first embodiment. This is what I did.

<First Embodiment> FIG. 1 is a diagram illustrating the optical path of an optical head according to a first embodiment, in which (a) is a plan cross-sectional view of the optical head, and (b) is a partially cutaway view of the optical head. 10 out of 0 diagrams showing the front view
0 indicates the housing of the optical head.

In FIG. 1, light 2 emitted from a semiconductor laser 1 that is a light emitting source is collimated by a collimating lens 3, reaches a polarizing beam splitter (PBS) 4 that also serves as beam shaping, and passes through a polarizing film 5. After that, the light is incident on the total reflection mirror 6. The light beam is totally reflected by this mirror 6 and deflected so as to be perpendicularly incident on the information medium 9 . Further, the information medium 9 is focused through a quarter-wave plate 7 and an objective lens 8 . The horizontal optical head is characterized by the fact that the optical path is vertically bent by the total reflection mirror 6 to form an optical path perpendicular to the surface of the medium 9.

The light 10 reflected by the information medium 9 passes through the objective lens 8 and the quarter-wave plate 7 again, and reaches the PBS 4.
It is polarized by the polarizing film 5 at a certain angle with respect to the incident direction, and the PB
S is refracted at the exit surface 11, and the lens 12. The light passes through the cylindrical lens 13 and is irradiated onto the light receiving element 14 .

FIG. 2 shows the optical head 100 in FIG.
0 to perform the seek operation, the seek moving table 10
1. This stand 101 is moved back and forth in the disk radial direction along rails 102a and 102b by a well-known linear motor or stepping motor 103 or the like.

Since this optical head is of a head drive type, when performing focusing drive, the objective lens 8 is independently swung up and down in the B direction (FIG. 1(b)) by a mechanism not shown. Further, when tracking drive is performed, the entire helad is rotated about the rotation axis 15 by an electromagnet (not shown in FIG. 1), and the irradiation beam of the medium 9 is directed in the C direction (first
As shown in (a) of the figure), tracking is possible in a direction perpendicular to the track direction (bit or guide groove forming direction).

What means (electromagnet, etc.) is used to realize rotation of the entire head 100 around the rotation axis 15 depends on other means for zero-rotation drive, which will be explained in other embodiments later. This is because there is no major difference from the example.

The rotary tracking drive in the head-driven optical head shown in Figs. 1 and 2 is easier to use and has higher torque than the conventional linear tracking drive using linear motors, etc., so it has better high-speed tracking. It is advantageous in terms of.

In the embodiment shown in FIG. 1, a line D connecting the rotation axis 15 and the optical axis of the objective lens 8, more precisely, a line D connecting the rotation axis 15 and the optical axis of the objective lens 8, and a line D connecting the rotation axis 15 and the optical axis of the objective lens 8, The line of intersection between the light and the plane formed by the demultiplexed light is approximately parallel to the track direction A of the recording medium 9. This means that if the beam spot irradiated onto the track is not made substantially parallel, the TE multiplied signal Trac output by the light receiving element 14 will be
This is because there is a possibility that an unfavorable deviation may occur in the error signal (kError Signal). In addition, the objective lens 8
When the bit does not vibrate around the track, that is, when the minute vibration C is not perpendicular to the track, even if the bit is the same length, the time it takes to pass through the beam changes due to the vibration of the objective lens, resulting in jitter and a decrease in gain. It is from.

In addition, in the two head-driven optical heads disclosed in Jitsukasho mentioned above, the distance between the rotation axis and the objective lens is long, so the vibration direction of the objective lens is substantially perpendicular to the bit string. Although no problem occurs, in the small and lightweight optical head according to the first embodiment, since the distance between the rotation axis and the objective lens is short, the rotation axis 15 and the optical axis of the objective lens 8 are actively connected. It is necessary to make the line parallel to the track direction A of the recording medium 9. This is due to the essential structural difference that distinguishes the present invention from the prior art. In this specification, a description of a new problem caused by making the direction parallel to the direction A, and a method for solving this problem will be described later.

According to the above embodiment of FIG. 1, the following effects can be obtained.

(2): The seek control mechanism and the track following mechanism are separated, and the track following control is achieved by rotating the entire head, making the optical head smaller and lighter. Therefore, the drive system for performing the seek operation does not require a linear motor or the like that has good characteristics up to a high frequency range, which leads to a reduction in the cost of the entire optical disk device.

(2) Also, since the drive system for tracking only needs to be rotated enough to achieve track following, the rotation angle becomes minute, and the entire head can be made smaller.

If possible, the line connecting the rotation axis 15 and the optical axis of the objective lens 8 is arranged to be approximately parallel to the track direction A of the recording medium 9, so that the signal appearing on the light receiving element 14 is The deviation becomes small and tracking can be performed accurately.

■: The optical head of the first embodiment is smaller overall than the two Jitsukasho mentioned above, so even if the rotation axis and the center of gravity are misaligned, the couple generated during the seek operation The optical head made by Jitsukasho is not very large.

However, this first embodiment may potentially include the following problems, particularly problems related to the above-mentioned item (2). Potential means that this problem is actually used in the PB.
This is because it may or may not occur depending on the weight of S, prism, objective lens, etc. Below, we will discuss these issues.

When the entire head is rotated around the shaft 15 to perform track control as in the first embodiment, the balance of the entire head with respect to the shaft 15 becomes a problem. If the servo is applied when the center of gravity of the head is not aligned with the center of rotation, abnormal operation will occur because the center of gravity and the center of rotation are misaligned.Also, if the head is sent in the radial direction (head feed), the center of gravity of the head will be Since a force acts in the direction opposite to the feeding direction, a rotational force is generated around the rotation axis, causing the head to rotate. Therefore, even after the head has finished moving, vibrations remain in the head for a while, and it takes time for the vibrations to settle down before normal tracking control can be performed. As described above, matching the center of gravity of the entire optical head with the rotation axis is an important issue in an optical head that achieves tracking drive by rotating the head.

However, not only in the first embodiment but also in a general optical head, among the parts constituting it, the heavy parts are said to be electromagnets, prisms, etc. For example, in the first embodiment, around the objective lens 8, a focusing magnet (not shown), a coil (not shown), a
4 wavelength plate7. Prisms, etc. have no choice but to concentrate. For this reason, the center of gravity X of the entire optical head tends to be included within the PBS 4 or closer to the objective lens 8, as shown in FIG. As you can see from the figure, even if you try to match the center of gravity of the head with the center of rotation for the purpose mentioned above, if the center of gravity is included within PBS4 as shown in Figure 3, In this case, the rotation shaft 15 cannot be provided inside the PBS.

Furthermore, even if the center of gravity is closer to the objective lens side as in the embodiment shown in FIG.
It is difficult to establish

It is also possible to forcibly install a balance weight to shift the center of gravity, as in the two Jitsukasho cases mentioned above, but as mentioned above, this increases the weight of the entire optical head and may even cause problems. It is. Therefore, the following second embodiment is proposed.

<Second Embodiment> FIG. 4 is a cross-sectional view of the optical head 100 according to the second embodiment, taken along the rotation axis. This is the recesses 105a and 10 for bearings in the housing 100 of the optical head.
5b, and the protrusion 10 of the support arm 106 is fixed to a head mounting table (which may be similar to the table 101 in FIG. 2).
4a and 104b fit into the aforementioned recesses 105a and 105b to support the entire head. The depth of the recesses 105a and 105b is not deep enough to affect the optical path. Note that the other structures are approximately the same as those of the first embodiment.

Therefore, according to this second embodiment, (1) Even if the center of gravity of the optical head interferes with the optical path, or if the rotation axis passing through the optical head is difficult in terms of space, the rotation center It becomes possible to completely match the center of gravity of the optical head with the center of gravity of the optical head, so that the track following operation becomes accurate and harmful couples are not generated during the seek operation.

By the way, the following potential problems may occur also in this second embodiment. That is, when the shaft is supported at two points, upper and lower, it is difficult to increase mutual accuracy. Also, it is not effective in terms of the structure and space for holding it.

<Third Example> Therefore, the third example is based on the first example. This is a further development of the second embodiment, and its purpose is: (i): While ensuring the effects of (1) to (3) described above, the optical head is supported by a rotating shaft passing through the inside of the optical head. .

(ii): While removing the rotation axis from the optical system, the rotation axis and the center of gravity are always made to coincide.

(iii): The diameter of the rotating shaft should be sufficient.

For this reason, the optical head of the third embodiment shown in FIGS. 5A to 5C is the first embodiment. The structure differs from the optical head of the second embodiment in the following points.

I: The included angle between the optical path 2 from the light emitting element 1 to the PBS 4 and the optical path from the PBS 4 to the light receiving element 14 is narrowed. That is, the light receiving optical system (consisting of lens 12, cylindrical lens 13, and detector 14) is tilted toward the laser diode 1 to narrow the included angle. For this reason, the reflected light from the reflecting mirror 6 is incident on the surface of the polarizing film 5 at an incident angle of 50 degrees. This allows the center of gravity of the optical head to be aligned with laser diode 1.
The center of gravity tends to deviate from the optical path 10 as the object moves closer to the side.

II: Further, the laser diode 1 and lens 3 are moved back from the PBS 4 onto the optical axis in order to ensure a sufficient diameter of the rotation axis. In addition, the demultiplexing plane 5 in PBS4
The length of the optical system 4a on the diode 1 side is made longer.

The PBS 4 in FIG. 4 is longer than the PBS 4 in the first embodiment.

Due to the above I and II, the center of gravity of the head approaches the laser diode 1 side and deviates from the optical path 10 of the emitted light from the PBS 4, and the amount of deviation is sufficient, so the diameter of the rotation axis should also be large enough. Can be done.

The above I will be explained in more detail with reference to FIG. In FIG. 7, the reflected light from the reflecting mirror 6 is incident on the surface of the polarizing film 5 at an incident angle of 50 degrees.

Then, the polarized light from the polarizing film 5 is reflected and the PBS 4
The light is incident on the exit surface 11 at an incident angle of 10 degrees. Therefore, the refracted light from the exit surface 11 is approximately 15
It is tilted an extra degree toward the diode 1 side. That is, the center of gravity moves toward the diode 1 side and deviates from the optical path 10.

In this way, by actively moving the center of gravity out of the PBS 4 and each optical path, and aligning the center of gravity with the center of rotation outside the optical path, the overall balance is improved, and even when moving the head, It exhibits stable mechanical response because no force couple occurs. Moreover, the diameter of the shaft 15 can also be made sufficient. Furthermore, since the surface angle of the polarizing film 5 is simply slightly changed, PBS4. Reflector 6. The balance of the portion consisting of the objective lens 8 does not change significantly. Therefore, the amount of movement of the center of gravity can be easily predicted.

In this third embodiment, as explained in the above section, the angle of the polarizing film surface 5 is changed to approximately 50 degrees in order to move the center of gravity. However, in this case, the demultiplexed light no longer enters the exit surface 11 perpendicularly, and is therefore refracted, causing beam deformation. Therefore, the angle of incidence of the demultiplexed light on the polarizing film 5 needs to be limited to a range in which the influence of beam deformation on the servo signal is minimal.

In order to eliminate beam deformation, it is conceivable to change the shape of the PBS 4 so that the demultiplexed light is perpendicularly incident on the exit surface, but this is not appropriate in terms of cost and productivity.

FIG. 5B is a perspective view of the optical path of the optical head 100 of the third embodiment, and FIG. 5C is a diagram showing the mounting state of the optical head 100. In FIG. 5C, 110 is a shaft body for rotating the optical head 100. 113 is a hollow coil for tracking, which is fixed to the optical head housing. Reference numeral 112 denotes a yoke of an electromagnet, which is fixed to the mounting table 101 via a spacer 111. hollow coil l1
When a predetermined servo current for tracking control flows through the yoke 112, the magnetic field generated by the electromagnet of the yoke 112 acts to swing the optical head 100 left and right around the shaft 110 by approximately ±1 mm.

In this third embodiment, as in the first embodiment, the head arrangement is such that the straight line D° connecting the rotation axis 15 and the optical axis of the objective lens is parallel to the track direction A. And so. With this arrangement, the head is swung around the track, so a signal with small jitter can be obtained for the same reason as in the first embodiment.

<Improvement of tracking and focusing control> In the first to third embodiments, in common, the straight line D' (or D) connecting the rotation axis 15 and the optical axis of the objective lens is set in the track direction A. parallel. As explained in connection with the first embodiment, the reason for this parallel arrangement is to ensure that the radial deflection of the head due to tracking control is perpendicular to the track forming direction. However, especially in the case of the third embodiment, since the rotating shaft 15 is out of the optical path, the angle formed by the straight line D° connecting the rotating shaft 15 and the optical axis of the objective lens and the track forming direction A is θ is no longer “O”, and therefore the bit image (usually approximately rectangular) reflected on the mirror 6 is no longer erect, and is rotated counter-rotated by θ with respect to the inclination direction of the surface of the mirror 6. Then, the bit image rotated by this θ is reflected by the polarizing film 5 and exits from the exit surface 11.
The light is refracted and irradiated onto the detector 14. As mentioned above, when the bit image is rotated by .theta., the image is rotated by .alpha. degrees on the detector 14, as shown in FIG. 6A. That is, FIG. 6A shows the beam spot shape on the detector 14 at the time of focusing, and the diffraction image 60 due to the bit appearing within this circular spot is
It is rotated by α degrees with respect to the dividing direction of the divided detector 14. As is well known, if the outputs from the 4-division detector 14 are I, II, III, and IV, then the TE multiplied signal (I + rV) - (II + III) is obtained.
If the diffraction image is rotated by α degrees with respect to the dividing direction as shown in Figure A, accurate tracking signals cannot be obtained. Furthermore, this rotation of the diffraction image also affects the focusing signal. That is, as is well known, the cylindrical lens 13 and the detector 14 are in a positional relationship rotated by 45 degrees with respect to the optical axis, so that the circular reflected beam from the disk surface is deformed into a vertically or horizontally elongated beam when it is out of focus. Therefore, the focusing servo FE signal (=(1
+m)-(II+rV)). However, if the diffraction image is rotated by α degrees, it becomes difficult to determine whether the FE flaw signal error component is an error component due to an out-of-focus state or a result of the diffraction image being rotated by α degrees. In other words, focusing control cannot be performed normally. It is clear that if focusing control cannot be performed, tracking control cannot be performed normally.

Therefore, the following configuration is further added to the optical heads of the first to third embodiments. That is, as shown in FIG. 6B, the cylindrical lens 13 and the detector 14
are further rotated by α degrees while maintaining a positional relationship that is rotationally shifted by 45 degrees. In this case, since the direction of the diffraction image and the dividing direction of the detector 14 are parallel or perpendicular, errors due to rotation of the TE multiplied signal, FE flaw signal, and diffraction image will not occur. That is, accurate tracking control and focusing control are possible.

[Effects of the Invention] As explained above, the optical head according to the present invention performs head feeding and track following control using different mechanisms in a horizontal optical head including at least an optical demultiplexer, an optical path converter, and an objective lens. , an optical head that rotates the entire head by a small angle around a predetermined rotation axis in order to perform track following control, and the mutual positional relationship of the above-mentioned components of the optical head is determined with respect to the rotation. fixedly placed,
The rotation axis is parallel to the optical axis of the objective lens.

According to the invention having such a configuration, since the rotation axis is parallel to the optical axis of the objective lens, a horizontal head is realized. Further, track following control is realized by rotating the entire head by a small angle around a predetermined rotation axis. Therefore, only the track following control by rotating the head is performed by the optical head, which contributes to miniaturization of the device and improved tracking performance compared to tracking drive of the entire head using a conventional linear method.

Further, according to the inventions of Items 2 and 3, since the mutual positional relationship of the components of the optical head is arranged such that the center of gravity of the optical head is outside the optical path of this head, the components are rotated to the center of gravity. It becomes easy to set the moving axis.

According to the fourth aspect of the invention, the center of gravity can be moved out of the optical path by arranging the light emitting source and the light receiving element in a positional relationship in which they approach each other.

According to the invention of item 5, the movement of the center of gravity out of the optical path is caused by the first
．． This is achieved by setting the length of either one of the second optical systems in the optical path direction to such a length that the center of gravity of the optical head exits the optical path of the light emitted from the optical demultiplexer. .

According to the invention set forth in item 6, the emission direction of the demultiplexed light is changed by changing the incident angle to the demultiplexing plane, and therefore, the position of the light-receiving element, etc. that receives light in this emission direction is balanced in order to balance the arrangement. It becomes possible to move.

According to the invention set forth in Item 7, the intersection line between the plane formed by the rotation axis and the optical axis of the objective lens and the plane formed by the incident light and the demultiplexed light passing through the optical splitter is relative to the track direction of the recording medium. Since the directions are substantially parallel to each other, the direction of vibration of the optical head for tracking the track is perpendicular to the direction of the track, and an accurate tracking signal can be obtained.

According to the invention set forth in Item 8, the optical head further includes an optical element that rotates the emitted light from the splitter in the direction in which the emitted light travels around the optical axis, and receives the emitted light that has passed through this element. a light-receiving element that In order to compensate for the rotation of the image caused by aligning the center of gravity with a certain center of gravity and making the first intersection line and the track direction substantially parallel, the optical element was further rotated by a predetermined angle around its optical axis. Errors in tracking signals and focusing signals caused by the invention in item 7 can be compensated for.

[Brief explanation of the drawing]

1 is a plan view and a front view of an optical head according to a first embodiment of the present invention, FIG. 2 is a perspective view of the optical head according to the embodiment of FIG. 1 mounted, and FIG. 3 is a first embodiment of the present invention. 4 is a cross-sectional view of the optical head according to the second embodiment, and FIGS. 5A to 5C are optical path diagram 2 and optical path perspective view of the optical head according to the third embodiment, respectively. , an implementation diagram, FIG. 6A is a diagram explaining a problem common to the first to third embodiments, FIG. 6B is a diagram explaining a technique to solve the problem, and FIG. 7 is a diagram of the third embodiment. In an example, it is a figure explaining the angular polarization of the polarizing film 5 performed in order to enable a center of gravity movement. In the figure, 1... semiconductor laser, 2... injection beam, 3
... Collimating lens, 4... Polarizing beam splitter (PBS), 5... Polarizing film, 6... Total reflection mirror 7... Quarter wavelength plate, 8... Objective lens, 9
...information recording medium, 10...reflected light, 11...P
BS exit surface, 12... Lens, 13... Cylindrical lens, 14... Light receiving element, 15... Rotating shaft portion, 6o...
- Diffraction image, 100... Optical head housing, 101...
Mounting table, 102a, 102b...Rail, 103...
- Optical head seek drive unit, 104a, 104b
--Protrusion, 105a, 105b...Recess, 10
6...Support arm, 110...Shaft body, 111...
Spacer, 112... Electromagnetic yoke, 113... Electromagnetic coil. J/14 Figure 3 Figure 4 Figure 5B Figure 5C

Claims (1)

[Scope of Claims] (1) In a horizontal optical head including at least an optical demultiplexer, an optical path converter, and an objective lens, head feeding and track following control are performed by different mechanisms, and a predetermined method is used to perform track following control. An optical head that rotates the entire head by a small angle around a rotation axis, wherein the mutual positional relationship of the components of the optical head is fixed with respect to the rotation, and the rotation axis is parallel to the optical axis of the objective lens. (2) The optical head according to claim 1, wherein the mutual positional relationship of the components of the optical head is arranged such that the center of gravity of the optical head is outside the optical path of this head. head. (3) The optical head according to claim 2, wherein the rotation axis passes through the center of gravity of the optical head. (4) The optical head further includes a light emitting source and a light receiving element in the direction in which the light emitted from the optical splitter advances, and the optical head further includes a light receiving element in a direction in which the light emitted from the optical splitter travels, and within a plane formed by the incident light passing through the optical splitter and the demultiplexed light. , the light emitting source and the light receiving element are arranged in a positional relationship close to each other, so that the center of gravity of the optical head is outside the optical demultiplexer. optical head. (5) The optical head further includes a light emitting source, a first optical system that guides the light beam from the light emitting source to the demultiplexer, and a first optical system that guides the emitted light from the optical system to the optical path converter. and a second optical system, and the length of at least one of the first and second optical systems in the optical path direction is such that the center of gravity of the optical head is outside the optical path of the light emitted from the optical demultiplexer. 2. The optical head according to claim 2, wherein the optical head is set to have a length that is equal to or greater than the length of the optical head. (6) The optical head further includes a light emitting source and a light receiving element in the direction in which the emitted light from the optical splitter travels, and the emitted light traveling from the optical demultiplexer to the light receiving element is directed toward the light emitting source. 3. The optical head according to claim 2, wherein the inclination of the demultiplexing surface of the demultiplexer is set to a predetermined angle so that the demultiplexer is tilted. (7) The intersection line between the plane formed by the rotation axis and the optical axis of the objective lens, and the plane formed by the incident light and the demultiplexed light passing through the optical demultiplexer is approximately parallel to the track direction of the recording medium. The optical head according to claim 1, wherein the optical head is parallel to each other. (8) The optical head further includes an optical element consisting of a plurality of lenses that converges the emitted light from the splitter in the direction in which the emitted light travels, and receives the emitted light that has passed through this optical element. a light-receiving element that The optical element is further rotated by a predetermined angle around its optical axis in order to align the center of gravity with a certain center of gravity and compensate for rotation of the image caused by making the first intersection line and the track direction substantially parallel. An optical head according to claim 7.