JPH01220132A - Optical disk device - Google Patents

Abstract

PURPOSE:To detect a focus error signal and a tracking error signal and to reduce the number of parts by arranging a condenser lens between an optical path changing means and an optical detector and providing plural photo- detecting surfaces in the optical detector. CONSTITUTION:An optical beam from a light source 10 is passed through a polarizing beam splitter 5, a 1/4 wavelength board 4 and an objective lens 2 and condensed on an optical disk 1 as faint light and the reflected light is passed through a reverse route and separated in the splitter 5. Next, the upper half of the reflected light, whose optical path is changed, is incoming to a condenser lens 11, which is cut by a plain to include an optical axis, and receives the operation of the lens 11. Then, the light is condensed on a photo- detecting surface 13 for focus of an optical detector 12 and the remaining half of the light straightly proceeds to the optical detector as it is in a part, where is no lens 11, and the light is incoming to a photo-detecting surface 14 for tracking control. As a result, a focus error and a tracking error are detected.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention is applicable to optically reading information recorded on optical discs used in consumer optical video or optical audio disc devices, image file devices, etc. An optical head for optically recording information on a disk or for recording and reproducing information, especially a servo signal for performing various servo operations such as focusing and tracking using reflected light from an optical disk. Alternatively, the present invention relates to an optical disc device for obtaining reproduction signals.

[Conventional technology]

In general, in optical disk devices, when recording and reproducing information, it is necessary to constantly irradiate the optical disk with a light beam from a light source such as a laser in a minute spot with a diameter of about 1 μm, for example, using the optical system of the optical head. be.

Incidentally, as the optical disk rotates, surface runout occurs in a direction perpendicular to the rotation direction, that is, a direction perpendicular to the disk surface, and eccentricity occurs in the radial direction. Therefore, a servo technology is required to control the amount of deviation between these two types, and making the light spot follow the movement of the surface runout is called focus control (also called focus servo), and making the light spot follow the movement of the eccentricity. This is called tracking control (also called tracking servo).

First, prior to explaining the present invention, the servo technology that has been proposed in the past will be explained based on Japanese Patent Application Laid-Open No. 195330/1983.

FIG. 4 is a plan view showing the configuration of a conventional optical disk device. In the figure, 1 is an optical disk installed rotatably. This optical disk 1 includes an information track 1a and is used only for reproducing signals. In a disk, tracks are formed by recorded signals, and in a disk for recording and reproducing signals, they are formed by guide grooves coated with an optical recording thin film.

Reference numeral 2 denotes an objective lens provided to face the optical disc 1. The objective lens 2 condenses a light beam emitted from a light source such as a semiconductor laser (not shown) into minute light P with a diameter of about 1 μm, and directs it onto the optical disc L. irradiate.

Reference numeral 3 denotes an objective lens driving device provided around the objective lens 2, and this objective lens driving device 3 uses a known technique to move the lens in a direction perpendicular to the disk surface for focus control and for tracking control. The optical disc 1 is driven in a direction perpendicular to the information track la on the optical disc 1, and a well-known electromagnetic force is used as the driving method.

4 is a two-wavelength plate, 5 is a polarizing beam splitter as an optical path changing means, 6 is a splitting prism formed integrally with this polarizing beam splitter 5 by adhesion, etc., and 7 is a track signal detector. They are arranged in a straight line behind the lens 2 with a predetermined distance therebetween.

8 is a condenser lens placed in the direction in which the light split by the splitting prism 6 is reflected, and 9 is a focus signal detector placed at the focal length of the condenser lens 8.

With the above-described configuration, a light beam emitted from a light source such as a semiconductor laser (not shown) is incident in the direction of the arrow a, is reflected by the polarizing beam splitter 5, and its optical path is converted to the direction of the optical disk 1, and the two-wavelength plate 4 is A minute light spot P is created on the optical disc 1 by the objective lens 2.

In the figure, x, y, and z indicate coordinate axes, and one information track la on the optical disk l extends in the X-axis direction. Therefore, the objective lens driving device 3 drives the objective lens 2 for focus control.
is driven in two axes, and in the y-axis direction for tracking control.

The light beam irradiated onto the optical disk 1 is reflected in the b direction to become reflected light, passes through the objective lens 2, wavelength plate 4, and polarizing beam splitter 5, and enters the splitting prism 6. As shown in the figure, the reflected light from the right hand passes through the splitting prism 6, goes straight and enters the track signal detector 7, and the reflected light from the right hand is divided into two directions. is totally reflected in the direction perpendicular to the transmitted light, the direction of arrow C in the figure, changes the optical path toward the focus signal detector 9, passes through the condensing lens 8, and is condensed to the focus signal detector 9. Light enters.

The track signal detector 7 detects a tracking error signal, and the focus signal detector 9 detects a focus error signal based on the difference in output signals of images formed by the respective reflected lights incident in this way.

[Problem to be solved by the invention]

However, according to the above-mentioned conventional technology, the detectors for detecting the surface runout of the optical disk during recording and reproduction and the amount of deviation in eccentricity in the radial direction, that is, the track signal detector and the focus signal detector, are each separated and independent. As a result, the number of parts increases, which hinders miniaturization of the fruiting device.

Furthermore, since each of these two detectors, which are arranged separately and independently, requires a sophisticated adjustment device, it is not only expensive, but also the adjustment operation by each adjustment device is performed separately. Therefore, there is a problem that the time required for the adjustment becomes long.

Therefore, the present invention has been made to solve the above problems, and by reducing the number of parts without installing two detectors and two corresponding adjustment devices, it is possible to increase the size of the device and reduce the number of parts. It is an object of the present invention to provide an excellent optical disc device that is small, inexpensive, and can be adjusted in a short time without increasing the price and lengthening the adjustment time using an adjustment device.

[Means to solve the problem]

In order to achieve the above-mentioned object, the present invention provides a condensing lens that is cut by a plane parallel to a plane containing the optical axis and has an opaque region between the cut plane and the plane containing the optical axis. disposed between the means and the photodetector, and the photodetector is divided into a first light-receiving surface and a second light-receiving surface by a dividing line located at the focal point of the reflected light passing through the condenser lens. A first light-receiving surface and a second light-receiving surface are separated by a dividing line that divides the reflected light that does not pass through the focusing lens into two parts in the same shape.
The tracking control light-receiving surface is divided into two light-receiving surfaces.

[For production]

With the above-described configuration, a light beam is emitted from the light source, and half of the reflected light irradiated onto the optical disk via the optical path changing means is made to enter the focus control light receiving surface of the photodetector through the condenser lens.

Further, the remaining half of the reflected light is caused to travel straight through the cut portion of the condensing lens without passing through the lens, and enters the light receiving surface for tracking control of the photodetector.

The reflected light incident in this way forms an image on each control light-receiving surface, and the difference in output signal between the first light-receiving surface and the second light-receiving surface of each control light-receiving surface produces a focus error signal and tracking. Detect the error signal.

〔Example〕

Embodiments of the present invention will be described below based on the drawings.

FIG. 1 is a plan view showing the configuration of the optical disc device of the present invention, and FIG. 2 is a diagram showing the structure of the photodetector shown in FIG. 1.

In Figures 1 and 2, 1 is an optical disk, la is an information track, 2 is an objective lens, 4 is a single wavelength plate, and 5 is a polarizing beam splitter, which are almost the same as conventional ones. The optical discs 10 are arranged in sequence in a straight line so that the light beams emitted from the optical discs are focused on the optical disc.

1 is a condensing lens provided in the traveling direction of the reflected light whose optical path has been changed by the polarizing beam subric 5;
This condensing lens 11 is cut by a plane including the optical axis,
Moreover, the cut plane is arranged so as to be orthogonal to the track direction shown in FIG.

12 is a photodetector placed at the focal length of the reflected light focused by the condenser lens 11;
As shown in FIG. 2, it includes a focus control light receiving surface 13 into which the reflected light that has passed through the condensing lens 11 enters, and this focus control light receiving surface 13, and directs the reflected light without passing through the condensing lens 11. The light-receiving surface 14 for tracking control is divided into a light-receiving surface 14 for tracking control through which reflected light enters, and one of the two light-receiving surfaces 13 for focus control is divided by a dividing line The light receiving surface 14 is divided into two parts, a first light receiving surface 13a and a second light receiving surface 13b, in a direction perpendicular to the tracking direction indicated by the arrow.
is divided into a first light-receiving surface 14a and a second light-receiving surface 14b parallel to the track direction by a dividing line Z perpendicular to the dividing line
The first light-receiving surface 13a and the second light-receiving surface 13b, or 14a and 14 of the re-controlled light-receiving surfaces 13 and 14 are divided.
The error is detected based on the difference between the output signal and the output signal b.

The operation will be explained using such a configuration.

First, when a light beam is emitted from the light source 10, the light beam passes through the polarizing beam splitter 5, the wavelength plate 4, and the objective lens 2, and is focused onto the optical disk 1 into a minute beam P with a diameter of about 1 μm.

The reflected light, narrowed down and condensed in this way, is reflected by the optical disk 1 and sent to the objective lens 2 in the opposite direction to the forward path.
, and the two-wavelength plate 4, and further enters the polarizing beam splitter 5, where the optical path is separated from the forward path and changed toward the photodetector 12.

As shown in FIG. 1, the reflected light whose optical path has been changed enters the condenser lens 11 whose upper half is cut by a plane that includes the optical axis, and is subjected to the action of the condenser lens 11 for photodetection. The light is focused on the focusing light receiving surface 13 of the device 12. The remaining half is the part without the condensing lens 11 that is used as the photodetector 12.
The light travels straight ahead and enters the tracking control light-receiving surface 14 of the photodetector 12 directly.

The reflected light that has entered the photodetector 12 in this way is
Focus errors and tracking errors are detected by forming images on the light receiving surfaces 13 and 14 of the photodetector 12, respectively.

FIG. 3 is a front view of the photodetector showing the detection state of the focus control light-receiving surface, and (A) shows that the optical disc 1 is
(B) is far from the focal length of optical disc 1.
shows a state close to the focal length of the objective lens 2.

When the light beam emitted from the light source section 10 is accurately focused on the track 1a on the optical disk 1 and the focal length is correct, the first light receiving surface of the focus control light receiving surface 13 is set as shown in FIG. The reflected light does not enter either the surface 13a or the second light-receiving surface 13b, and a focal point is formed on the dividing line X.

However, the optical disc 1 moves in the axial direction and the objective lens 2
When the optical disk 1 moves away from the objective lens 2 and the focal length shifts, the reflected light enters the second light-receiving surface 13b, as shown in FIG. The reflected light enters the first light-receiving surface 13a, and therefore both light-receiving surfaces 13a and 13b
A difference is generated between the output signals, and it is detected from this difference that the optical disc 1 has shifted in the axial direction.

Fig. 4 is an explanatory diagram showing the state in which the tracking error signal is detected, and shows the detection state of the light receiving surface for tracking control and the irradiation state on the optical disc corresponding to this detection state. Figures (A) and (C) show a state in which the optical disc 1 has moved and shifted in the radial direction, and Figure (B) shows a state in which it has not moved and is at a predetermined position and has not shifted.

If the objective lens 2 and the center of the information track 1a of the optical disc 1 match as shown in (B), then the first
The reflected light that enters the light-receiving surface 14a and the second light-receiving surface 14b is equal, and therefore there is no difference in the output signal between the light-receiving surfaces 14a and 14b, indicating that the optical disc 1 is not displaced in the radial direction. Detected.

In addition, as shown in (A) or (C), the optical disc 1
is shifted in the radial direction, causing the objective lens 2 and the optical disc 1 to
If the center of the track 1a deviates to the left or right, the reflected light that enters both the light receiving surfaces 14a and 14b will not be equal, resulting in a difference in the output signal, and as a result, the optical disc 1 is detected to be displaced in the radial direction.

In addition, in this embodiment described above, the light source is arranged so that the light beam emitted toward the optical disk is in a straight line, and the optical path is changed by a polarizing beam splitter to the photodetector that receives the reflected light from the optical disk. However, this positional relationship can be changed in various ways even if it is reversed, and it is possible to further reduce the size of the device by devising the arrangement.

〔Effect of the invention〕

With the above-described configuration, according to the present invention, a light beam is irradiated through the optical path changing means, and half of the reflected light is passed through a condensing lens cut by a plane including the optical axis to the light receiving surface for focus control of the photodetector. The remaining half of the light is allowed to enter the light receiving surface for tracking control of the photodetector by passing the remaining half of the light straight through the lens without passing through the condensing lens. We decided to detect a focus error signal and a tracking error signal based on the difference in output signals between the surface and the second light-receiving surface.

In this way, the focus signal error detection detector and the tracking signal error detection detector, which were conventionally installed separately, are now integrated, reducing the number of parts and eliminating the need for installation space. Become.

In addition, each detector in the past was equipped with a sophisticated and expensive adjustment mechanism, but since the detectors are integrated, only one adjustment mechanism needs to be installed. Since the number of parts is reduced and the installation space is not required, it is possible to realize a device that is smaller, lighter, and lower in price.

Furthermore, since there is only one adjustment mechanism, it becomes possible to perform adjustment operations that were conventionally performed one by one at the same time, thereby reducing the time required for adjustment.

[Brief explanation of the drawing]

FIG. 1 is a plan view showing the configuration of the optical disc device of this embodiment, FIG. 2 is a front view showing the structure of the photodetector shown in FIG. 1, and FIG.
The figure is a front view of a photodetector showing the detection state of the light-receiving surface for focus control, FIG. 4 is a front view of the photodetector showing the detection state of the light-receiving surface for tracking control, and FIG. 5 is the configuration of a conventional optical disc device. FIG. ■...Optical disc 1a...Track 2...
・Objective lens 4...2 wavelength plate...Polarizing beam splitter 11...Condensing lens 12...Photodetector 13...
...Focus control light receiving surface 13a...First light receiving surface 13b...Second light receiving surface 14...Focus control light receiving surface 14a...First light receiving surface 14b...Second light receiving surface Light-receiving surface patent applicant Oki Electric Industry Co., Ltd. Representative Patent Attorney Takashi Kanakura Tsumugi 1 Plan view showing the configuration of the original disk device of the present invention 1 Front view showing the structure of the photodetector shown in Figure 1 2 Country (A) (B) Main parts of the photodetector showing the detection status Front four wheels 3 countries

Claims (1)

[Claims] 1. A light beam is irradiated onto an optical disk via an optical path changing means, and the reflected light is received by a photodetector to detect an error signal for controlling focus, tracking, etc. In the optical disk device, a condensing lens cut by a plane including the optical axis is disposed between the optical path changing means and the photodetector, and the photodetector is positioned at the focal point of the reflected light passing through the condensing lens. A light-receiving surface for focus control is divided into a first light-receiving surface and a second light-receiving surface by a dividing line, and the reflected light that includes this light-receiving surface for focus control and does not pass through the condenser lens is divided into two in the same shape. a tracking control light-receiving surface divided into a first light-receiving surface and a second light-receiving surface by a dividing line; An optical disc device characterized in that a focus error signal and a tracking error signal are detected based on a signal difference.