JPH06349087A - Tracking controller and optical recording and reproducing device using it - Google Patents

Abstract

PURPOSE:To obtain a tracking controller which can drastically reduce tracking offset caused by displacement of a light spot and is suitable for using for a separate type optical disk device. CONSTITUTION:A trapezoidal prism 20 tilting to a light axis is arranged in a light path between two reflecting mirrors 21 and 22 being rotatable. Two reflecting mirrors are constituted so that they are rotated by the same angle in the same direction at the same time. By using this constitution, deflection of the light axis by refraction function of the trapezoidal prism and parallel movement of a reverse direction for it occur at the same time, and position deviation of the light axis of an incident laser beam on an object lens 7 can be compensated. Consequently, occurrence of tracking offset accompanied by racking control of the light spot can be greatly reduced.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical recording / reproducing apparatus for recording / reproducing / erasing information by using a light spot, and more particularly to a disc-shaped optical information recording medium (hereinafter referred to as a disk-shaped optical information recording medium). , And a tracking control device for stably irradiating a predetermined position on an optical disc for simplification, and an optical recording / reproducing device using the tracking control device (hereinafter, referred to as an optical disc device for simplicity).

[0002]

2. Description of the Related Art Recently, in order to improve the access speed of an optical disk device, an optical system, a movable part having an objective lens and an objective lens actuator for driving the objective lens, a semiconductor laser light source and a photodetector are provided. Separation-type optical disk devices, which are separated into a fixed part provided with, are being put to practical use.

In such a separate type optical disk device, in particular, in order to reduce the size and weight of the movable part, a structure in which a tracking control device for controlling the position of a light spot in the radial direction of the optical disk, so-called tracking control is provided on the fixed part side is noted. Has been done.

Conventionally, as a tracking control device provided on the fixed portion side, a galvano-mirror system described in Japanese Patent Laid-Open No. 3-214430 is known. In this method, the laser beam incident on the objective lens is deflected by a galvanometer mirror to displace the light spot on the disk and control its position. It is a compact and lightweight device that supports high-speed tracking control. There is a feature that you can do it.

[0005]

However, when the galvano-mirror type tracking control device is arranged in the fixed portion of the separation type optical disc device, when the laser light beam is deflected to displace the light spot, it is accompanied by it. As a result, the optical axis of the laser beam incident on the objective lens is largely displaced. Therefore, there arises a problem that the position of the detection light spot which is reflected by the optical disc and enters the photodetector for detecting the tracking error signal is also largely displaced. When such a phenomenon occurs, a large offset occurs in the tracking error signal detected by the so-called push-pull method. As a result, the tracking control performance is significantly impaired, and the optical spot on the disk is largely off-tracked (hereinafter, for simplicity, the off-track amount of the optical spot due to the offset of the tracking error signal is referred to as the tracking offset amount). . Such a problem is a problem peculiar to the separation-type optical disk device, which occurs due to the long optical path length between the galvanometer mirror arranged in the fixed portion and the objective lens.

An object of the present invention is to provide a tracking control device which effectively reduces the tracking offset due to the displacement of the light spot as described above and is suitable for a separation type optical disc device, and an optical disc device equipped with the tracking control device. To do.

[0007]

In order to achieve the above object, at least two reflecting mirrors that are simultaneously driven to rotate in the same rotation direction at the same rotation angle are provided as a tracking control device, and the optical path between the reflection mirrors is further provided. Inside
An optical element is provided in which the first surface on which the light flux enters and the second surface on which the light flux exits are not parallel to each other. A specific example of this optical element is a trapezoidal prism. In this trapezoidal prism, the first surface on which the laser light is incident is 3
It is arranged so as to be inclined at an angle of 5 ° to 55 °.

Further, the trapezoidal prism is configured to be rotatable about a rotation axis substantially in the same plane as the rotation axis of at least one reflection mirror.

Further, in the optical disk device equipped with the tracking control device having the above-mentioned structure, a detecting means for detecting an offset voltage appearing in the tracking error signal, and a subtracting means for subtracting the offset voltage from the tracking error signal. Equipped with.

[0010]

When a trapezoidal prism is provided between two reflecting mirrors having a rotating function, the incident angle of laser light incident on the trapezoidal prism changes according to the rotation angle of the reflecting mirror. As a result, the laser light flux emitted from the trapezoidal prism is deflected by a predetermined angle according to the incident angle by the refraction of the prism, and moves in parallel in the direction opposite to the deflection direction. Therefore,
By optimally designing the shape and installation angle of the trapezoidal prism in accordance with the optical system of the optical disk device, even if the laser light flux incident on the objective lens is deflected, its optical axis deviation can hardly occur. As a result, the tracking control of the optical spot on the disk can be performed with almost no tracking offset.

Further, if the trapezoidal prism is also separately driven to rotate and is rotated by a predetermined angle as the movable part of the optical disk device moves to the inner and outer circumferences of the optical disk, the position of the movable part is changed. Regardless of the above, good tracking control can always be performed.

It should be noted that in an optical disk device provided with a tracking control device having such a trapezoidal prism, due to factors other than the above-mentioned factors causing tracking offset, for example, positional deviation of the semiconductor laser light source and optical components with time. By providing the detection means for detecting the offset voltage appearing in the tracking error signal and the subtraction means for subtracting this offset voltage from the tracking error signal, the static offset component contained in the tracking error signal can be electrically corrected. Therefore, more precise tracking control can be performed.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to each embodiment shown in FIGS. FIG. 1 is an explanatory diagram showing a main configuration of an optical disk device according to a first embodiment of the present invention.

In FIG. 1, a laser beam emitted from a semiconductor laser light source 1 sequentially passes through a collimating lens 2, a beam shaping prism 3, and a first beam splitter 4, and enters a tracking controller 5. The tracking control device 5 includes two reflecting mirrors 21 and 22 rotatable about a predetermined rotation axis (an axis perpendicular to the paper surface in FIG. 1) and an optical axis in the optical path between them as shown in FIG. The trapezoidal prism 20 is arranged at an angle of about 45 °. The laser light flux that has entered the tracking control device 5 is emitted from the tracking control device 5 through the reflection mirror 21, the trapezoidal prism 20, and the reflection mirror 22 in this order. Here, the optical axis of the laser beam incident on the tracking control device 5 is 100, and the optical axis of the light beam emitted from the tracking control device 5 is 101.

The light flux emitted from the tracking control device 5 is further reflected by the rising mirror 6 and then focused on the optical disk 8 by the objective lens 7. This objective lens 7
The position is controlled in the optical axis direction by the actuator 40 as will be described later, and thereby the focus control of the light spot on the disk is performed.

The laser beam reflected from the optical disk 8 follows an optical path substantially the same as the outward path, and the first beam splitter 4
Reach Then, this first beam splitter 4 is reflected, and further divided into two directions by a second beam splitter 9, passing through detection lenses 10 and 12, respectively,
Error signal detection optical system 11 and information signal detection optical system 13
Incident on each.

In the error signal detection optical system 11, the focus error signal of the light spot on the disk is detected by a known detection method such as an astigmatism method, and the focus control circuit 30 operates the actuator 40 based on this signal. By driving, the position of the objective lens 7 in the optical axis direction is controlled. The error signal detection optical system 11 detects the tracking error signal of the optical spot on the disc by a known detection method such as a push-pull method, and the tracking control circuit 31 drives the tracking control device 5 based on this signal. , Performs tracking control of the optical spot on the disc.

On the other hand, in the information signal detecting optical system 13, an information signal recorded on the optical disk 8 such as a magneto-optical signal or a phase pit signal is detected by a predetermined optical element. The specific configurations of the error signal detection optical system 11 and the information signal detection optical system 13 are well-known items, and thus description thereof will be omitted.

In the optical disk device of this embodiment, as shown in FIG. 1, a movable portion 51 consisting of a raising mirror 6, an objective lens 7 and an actuator 40 has an optical system other than the movable part 51, a photodetector, a tracking control device, etc. It is configured to be separated from the fixed part 50 made of, and only the movable part 51 moves in the radial direction of the optical disc 8 at the time of access.

Next, some embodiments of the tracking control device 5 used in each embodiment of the optical disk device according to the present invention will be described.

First, the specific structure of the first embodiment of the tracking control device of the present invention and the control principle of the tracking control device of the present invention will be described with reference to FIGS. 2 and 3. 2 is an explanatory diagram showing the configuration of the first embodiment of the tracking control device of the present invention, and FIG. 3 is an explanatory diagram schematically showing the basic principle of the tracking control device of the present invention.

The tracking control device 5 shown in FIG. 2 is mounted on the optical disk device shown in FIG. 1, for example. The reflection mirrors 21 and 22 in the tracking control device 5 are connected to each other by a connecting member 23 provided on a single rotation axis C.
Are fixed to both ends of the so that their reflection surfaces are parallel to each other. The rotary mirror actuator 41 is
The connecting member 23 is rotated around the rotation axis C by a predetermined angle θ according to the rotating mirror drive current supplied from the tracking control circuit 31. As a result, the reflecting surfaces of the reflection mirrors 21 and 22 fixed to the connecting member 23 also rotate in the same rotation direction as the connecting member 23 by an angle θ while maintaining the parallel relationship. On the other hand, the trapezoidal prism 20 is fixed at a predetermined position in the optical path between the reflection mirrors 21 and 22.

In such a configuration, the reflecting mirrors 21 and 2
The two reflecting surfaces are always parallel regardless of the rotation angle θ. Therefore, when the trapezoidal prism 20 is not in the optical path, the ray incident on the tracking control device 5 enters.
The optical axis 100 of the light flux and the optical axis 101 of the laser light flux sequentially reflected by the reflection mirrors 21 and 22 and emitted from the tracking control device 5 are always parallel to each other regardless of the rotation angle θ of the reflection mirrors 21 and 22. It will be

However, if the trapezoidal prism 20 is present in the optical path between the reflection mirrors 21 and 22, the angle φ formed by the incident surface of the trapezoidal prism 20 and the optical axis 100 reflected by the reflection mirror 21.
Becomes φ = 2θ + γ as shown in FIG. 2, and increases or decreases according to the rotation angle θ of the reflection mirrors 21 and 22. In such a case, as shown in FIG. 3, the optical axis of the light flux transmitted through the trapezoidal prism 20 is a predetermined angle β depending on the angle φ between the incident surface and the optical axis due to the refraction of the trapezoidal prism 20. Only deflect. Moreover, at that time, the optical axis emission position P of the light beam emitted from the trapezoidal prism 20 is translated by a predetermined distance ζ in the direction opposite to the direction of its deflection.

Therefore, the apex angle α, the initial installation angle γ, the thickness t, the refractive index n, etc. of the trapezoidal prism 20 are optimally designed in accordance with the optical system, and the trapezoidal prism 20 is approximately designed with respect to the incident optical axis. When installed at a predetermined angle γ within 35 ° to 55 °,
The displacement of the optical axis of the light flux incident on the objective lens caused by the deflection of the light flux is canceled well, and the optical axis of the light flux incident on the objective lens 7 is always the light source of the objective lens 7 regardless of its deflection angle β. It can pass near the side focal point position F. By doing so, the light spot S focused on the optical disc 8 is displaced by the displacement amount δ (δ = f ₀ · tan β; where f ₀ is the focus of the objective lens 7). Even if it is displaced by a distance), the optical axis of the reflected light beam from the optical disc 8 travels along the optical path substantially the same as the optical axis of the incident light beam, so that the detection light incident on the photodetector for detecting the tracking error signal is detected. Almost no spots are displaced. As a result, the offset hardly occurs in the tracking error signal detected by the push-pull method.

This situation will be described with reference to the calculation results shown in FIG. FIG. 4 is a diagram showing the relationship between the displacement amount δ of the optical spot on the disc and the tracking offset amount generated due to the displacement. In FIG. 4, in each of the tracking control device of the present invention described in the embodiment of FIGS. 1 and 2 and the conventional tracking control device using the galvano-mirror system, the movable part 51 of the optical disc device is the maximum disc. The results are shown for each position of the inner circumference portion, the middle circumference portion, and the outermost circumference portion. The parameter L in the figure represents the optical path length from the trapezoidal prism 20 to the objective lens 7.

As is clear from the result of FIG. 4, the tracking offset amount is improved by using the tracking control device 5 described in the embodiment of FIGS. 1 and 2, as compared with the conventional tracking control device using the galvano mirror. It is possible to perform tracking control in which the

By the way, in the embodiment of FIG. 2, the rotation axis C is arranged substantially in the middle of the reflection mirrors 21 and 22, and the trapezoidal prism 20 is fixed on the upper portion thereof.
The rotation axis C may be arranged at any position as long as it satisfies the condition that the vignetting of the light beam due to the rotation of the reflection mirrors 21 and 22 is within a predetermined allowable range. Further, the trapezoidal prism 20 may be arranged anywhere in the optical path between the reflection mirrors 21 and 22.

FIG. 5 is an explanatory diagram showing the configuration of the second embodiment of the tracking control device of the present invention. In the reflection mirror rotation drive mechanism of the tracking control device 5 of the present embodiment, the reflection mirrors 21 and 22 are provided with rotation axes C1 and C2, respectively, and the reflection mirrors are connected to each other by two connecting members 23 and 2.
4 are connected in parallel relation, and the rotary mirror actuator 4
With the driving force of 1, the reflecting mirrors 21 and 22 are configured to rotate while maintaining the parallel state (the two connecting members 23 and 24 are used in this embodiment, The number of connecting members is not limited to this). Even with the tracking control device 5 having such a configuration, the same effect as that of the embodiment of FIG. 2 can be obtained.

Although not shown, the reflection mirror 21,
An actuator for rotation driving is provided for each of the motors 22, and the direction and angle of rotation are electrically synchronized while rotating independently (synchronized rotation while keeping the parallel state of the reflection mirrors 21 and 22). The same effect as the embodiment of FIG. 2 is obtained.

The numbers of the reflecting mirrors and the trapezoidal prisms are not limited to two or one as in the embodiments of FIGS. 2 and 5, but may be the same as those of the present invention. However, it doesn't matter how many you have.

By the way, from FIG. 4 described above, when the movable part 51 of the optical disk device moves in the radial direction of the optical disk 8, that is, from the inner peripheral part to the outer peripheral part of the disk, tracking is performed with respect to the displacement amount δ of the optical spot on the disk. It can be seen that the offset amount value changes. This indicates that depending on the position of the movable portion 51, when the displacement amount δ of the light spot on the disc becomes large, a sufficient offset reduction effect may not be obtained. next,
An embodiment of the tracking control device capable of solving the problem of the variation in the offset reduction effect depending on the position of the movable portion 51 will be described.

FIG. 6 is an explanatory view showing the configuration of the third embodiment of the tracking control device of the present invention. This embodiment solves the problem of the fluctuation of the offset reduction effect depending on the position of the movable portion 51. Is. Also in the tracking control device 5 of this embodiment, the reflecting mirrors 21 and 22 are rotationally driven by a predetermined angle θ according to a predetermined tracking error signal, as in the embodiments of FIGS. Further, in this embodiment, separately from the reflecting mirrors 21 and 22,
The trapezoidal prism 20 is also configured to be rotationally driven,
Change in the position of the movable portion 51, that is, the trapezoidal prism 20.
It is configured to change the installation angle γ of the trapezoidal prism 20 with respect to the optical axis according to the change in the optical path length L from to the objective lens 7. By doing so, the tracking offset amount with respect to the displacement amount δ of the light spot can always be minimized regardless of the position of the movable portion 51.

For example, as in the example of FIG. 4, the trapezoidal prism 2
When the installation angle γ of 0 is γ = 45 °, the tracking offset amount with respect to the displacement amount δ of the light spot can be minimized when the movable portion 51 is in the disk inner peripheral portion (L = 95 mm). On the other hand, FIG. 7 is a diagram showing the relationship between the displacement amount δ of the optical spot on the disc and the tracking offset amount when γ = 40 ° and 50 °. That is, γ
= 40 °, when the movable portion 51 is located at the innermost peripheral portion (L = 110 mm) of the disc as shown in FIG.
When γ = 50 °, as shown in FIG. 7B, when the movable portion 51 is located at the outermost peripheral portion (L = 80 mm) of the disc,
The tracking offset amount with respect to the displacement amount δ of the light spot can be minimized.

The rotation of the trapezoidal prism 20 as described above may be carried out in accordance with the displacement of the movable portion 51 in the radial direction of the optical disk 8.
It is not necessary to drive at high speed unlike the tracking control by rotational drive of 1 and 22, and it can be realized by a relatively simple drive mechanism.

FIG. 8 is an explanatory view showing the main structure of an optical disk device according to the second embodiment of the present invention. In the figure, the same components as those in FIG. 1 are designated by the same reference numerals, and the description thereof will be omitted.

The optical disk device of this embodiment is the tracking control device 5 shown in the embodiment of FIG. 6, that is, the trapezoidal prism 2 depending on the displacement of the movable portion 51 in the disk radial direction.
Tracking control device 5 in which 0 is driven to rotate
It is equipped with. In the optical disc apparatus of this embodiment, the position of the movable portion 51 in the optical disc radial direction is detected by the movable portion position detection circuit 38 from the track address signal of the optical disc 8 included in the information signal detected by the information signal detection optical system 13. Is detected, and the trapezoidal prism rotation control circuit 39 controls the rotation of the trapezoidal prism 20 based on the detected signal. Such a trapezoidal prism 20
By providing the rotation control system for the trapezoidal prism 20, even if the movable portion 51 moves to an arbitrary position from the innermost peripheral portion to the outermost peripheral portion of the optical disk 8 by the access operation, the installation angle γ of the trapezoidal prism 20 is automatically adjusted accordingly. It is possible to control so that the tracking offset reduction effect is always optimum.

As the position detecting means of the movable portion 51, other than the above method, for example, a position sensor may be attached to the movable portion 51 and the position detection may be performed directly by a signal from the position sensor.

As described above, by using the tracking control device of the present invention, it is possible to greatly reduce the tracking offset generated by the tracking control of the light spot even in the separation type optical disc device.

Here, the cause of the tracking offset is not limited to the one caused by the tracking control of the light spot as described so far, and for example, the semiconductor laser light source 1 in the embodiment of FIG. 1 or FIG. , Optical components such as the collimator lens 2, the beam shaping prism 3, the beam splitter 4, and the raising mirror 6, and further, the position with time such as a photodetector for detecting a tracking error signal provided in the error signal detection optical system 11. A tracking offset caused by the deviation also occurs.

FIG. 9 is a schematic diagram for explaining the situation. When the optical axes 100 and 101 of the laser light flux are tilted due to the positional deviation of the semiconductor laser light source 1 or the optical components, the tracking error signal detection 2 provided in the error signal detection optical system 11 of FIG.
Detection light spot 102 irradiated on the split photodetector 14
The irradiation position of is also shifted. As a result, the differential amplifier 32
An offset voltage Voff is generated in the tracking error signal output via However, such a tracking offset voltage Voff does not depend on the displacement amount δ of the optical spot on the disk due to the tracking control, and takes a substantially constant value, for example, if the displacement amount of the semiconductor laser light source 1 or the optical component is constant. . Therefore, the offset voltage Voff can be satisfactorily corrected by a predetermined electric circuit.

FIG. 10 shows an embodiment of a tracking offset correction circuit for correcting the DC component of the tracking offset. The tracking error signal output from the differential amplifier 32 in the tracking control OFF state is converted into a digital signal by the A / D converter 33, and then the tracking error signal is converted by the upper peak detector 34 and the lower peak detector 35. Each peak value of the waveform is detected.
Then, the offset voltage is calculated from the average value by the microcomputer 36, and the microcomputer 3
6 is stored in the memory. When the tracking control is turned on, the microcomputer 36 receives the signal, outputs the stored offset voltage value, and subtracts it from the original tracking error signal via the D / A converter 37. As a result, the tracking offset generated in the tracking error signal immediately before the tracking control is turned on is removed during the tracking control operation period.

Although FIG. 10 shows an example of a tracking offset correction circuit using a digital circuit, the present invention is not limited to this circuit, of course, and the tracking error signal immediately before the tracking control operation or during the track jump is used for tracking. Any circuit may be used as long as it has a function of detecting the offset amount, holding the detected value during the tracking control operation period, and performing negative feedback to the tracking error signal.

By combining the tracking offset correction circuit as described above and the tracking control device of the present invention, the amount δ of displacement of the light spot on the disc during tracking control, the position of the movable portion 51, and the semiconductor laser light source and optical parts are obtained. It is possible to always perform highly accurate and stable tracking control without being affected by the static tracking offset caused by the positional deviation of the.

The tracking offset correction circuit as described above is not limited to the combination with the tracking control device of the present invention. For example, a device for performing tracking control by rotationally driving the trapezoidal prism itself, or It may be combined with another tracking control device such as a device using a conventional galvanometer mirror system.

Finally, all of the above-mentioned embodiments are 1
This is an example of applying the tracking control device of the present invention to an optical disc device that irradiates an optical disc with one light spot, but of course the same tracking control device is applied to an optical disc device that irradiates two or more light spots. Is also good. In this case, the tracking control device of the present invention can be used as a relative position correction device for a plurality of light spots.

[0047]

As described above, according to the present invention, in the tracking control device adapted to the separation type optical disk device and the optical disk device using the same, the occurrence of tracking offset due to the displacement of the light spot is significantly reduced. Is possible and its industrial value is enormous.

[Brief description of drawings]

FIG. 1 is an explanatory diagram showing a main-part configuration of an optical disk device according to a first embodiment of the present invention.

FIG. 2 is an explanatory diagram showing a configuration of a first embodiment of a tracking control device mounted on the optical disk device of the embodiment of the present invention.

FIG. 3 is an explanatory diagram schematically showing the basic principle of the tracking control device according to the embodiment of the present invention.

FIG. 4 is an explanatory diagram showing an example of a relationship between a light spot displacement amount and a tracking offset amount in a tracking control device according to an embodiment of the present invention and a conventional device.

FIG. 5 is an explanatory diagram showing a configuration of a second embodiment of the tracking control device mounted on the optical disk device of the embodiment of the present invention.

FIG. 6 is an explanatory diagram showing the configuration of a third embodiment of the tracking control device mounted on the optical disk device of the embodiment of the present invention.

FIG. 7 is an explanatory diagram showing another example of the relationship between the light spot displacement amount and the tracking offset amount in the tracking control device according to the embodiment of the present invention.

FIG. 8 is an explanatory diagram showing a main configuration of an optical disk device according to a second embodiment of the present invention, which is equipped with the tracking control device of FIG.

FIG. 9 is an explanatory diagram schematically showing generation of tracking offset due to inclination of the optical axis.

FIG. 10 is a block diagram showing an example of a tracking offset correction circuit applied to the optical disc device of the embodiment of the invention.

[Explanation of symbols]

1 Semiconductor Laser Light Source 7 Objective Lens 8 Optical Disk 5 Tracking Control Device 20 Trapezoidal Prism 21, 22 Reflecting Mirror C, C1, C2 Rotation Axis 34 Upper Peak Detector 35 Lower Peak Detector 36 Microcomputer 38 Moving Part Position Detection Circuit 39 Trapezoid Prism rotation control circuit 41 Rotating mirror actuator 50 Fixed part 51 Movable part 100 Optical axis of laser beam incident on tracking control device 101 Optical axis of laser beam emitted from tracking control device

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Masayuki Inoue Masayuki Inoue, 292 Yoshida-cho, Totsuka-ku, Yokohama-shi, Kanagawa Inside the Hitachi Media Visual Media Laboratory (72) Inventor Michio Miura 292 Yoshida-cho, Totsuka-ku, Yokohama-shi, Kanagawa Incorporated company Hitachi Media & Video Research Laboratories (72) Inventor Motoyuki Suzuki 292 Yoshida-cho, Totsuka-ku, Yokohama-shi, Kanagawa Inside Corporate Imaging & Media Research Laboratories Hitachi, Ltd. (72) Hisamitsu Tanaka Yoshida Totsuka-ku, Yokohama-shi, Kanagawa 292, Machi Incorporated company Hitachi, Ltd. Visual Media Research Center

Claims (6)

[Claims] 1. A laser light source, an objective lens for collecting laser light emitted from the laser light source at a predetermined position on an optical information recording medium to form a light spot, and the optical information recording medium reflected by the objective lens. An optical system comprising: an optical signal detecting means for detecting a tracking error signal of the optical spot from the reflected laser light of the optical spot; and a tracking control device for performing tracking control of the optical spot based on the tracking error signal. In a tracking controller for a dynamic recording / reproducing apparatus, the tracking controller is an optical element in which a first surface on which the laser light is incident and a second surface on which the laser light is emitted are not parallel to each other. And a reflection mirror having a rotation function, a tracking control device. 2. The tracking control device according to claim 1, wherein the tracking control device includes at least two reflection mirrors that are simultaneously driven to rotate in the same rotation direction by the same rotation angle, and between the two reflection mirrors. The tracking control device, wherein the optical element is provided in the optical path of the. 3. The prism according to claim 1, wherein the optical element is a prism having a first surface on which the laser light is incident and a second surface on which the laser light is emitted are non-parallel. And at least the first surface of the prism is
The tracking control device is arranged so as to form an angle of 35 ° to 55 ° with respect to the optical axis of the laser light incident on the surface. 4. The tracking control device according to claim 1, wherein the optical element can be rotationally driven around a rotation axis that is substantially in the same plane as the rotation axis of the reflection mirror. 5. A laser light source, an objective lens for collecting laser light emitted from the laser light source at a predetermined position on an optical information recording medium to form a light spot, and the optical information recording medium reflected by the objective lens. An optical system comprising: an optical signal detecting means for detecting a tracking error signal of the optical spot from the reflected laser light of the optical spot; and a tracking control device for performing tracking control of the optical spot based on the tracking error signal. In the optical recording / reproducing apparatus, the optical recording / reproducing apparatus includes a fixed portion including the laser light source, the optical signal detecting means, and the tracking control device according to any one of claims 1 to 4, and the objective lens. An optical recording / reproducing apparatus comprising: a movable part including the movable part, wherein only the movable part moves in a predetermined direction. 6. The tracking control device according to claim 1, detection means for detecting an offset voltage appearing in the tracking error signal, and subtraction means for subtracting the offset voltage from the tracking error signal. An optical recording / reproducing apparatus comprising: