JPS6292144A - Optical recording and reproducing device having plural optical spots - Google Patents

Abstract

PURPOSE:To allow two optical spots to trace always the same guide track by providing a prism arranged in an optical path of an optical means forming plural optical spots and a means driving the said prism so as to generate plural optical spots. CONSTITUTION:The optical spots L, M are formed and a tracking control signal from each optical spot is detected. An output optical beam (m) from a semiconductor laser 13 passes a prism 1 after through a condenser lens 14. In applying tracking control to the optical spot M, the prism 1 is turned by a turning means 2. The 2nd drive means moving the 2nd optical spot M consists of the prism 1 and the turning means 2 and since the moving quantity of the optical spot is small with respect to the turning angle of the prism, the permissible range of the maintaining accuracy of the neutral position of the drive means is larger and an highly accurate drive means is required and the constitution is simplified.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention focuses two laser beams onto an optical recording medium (for example, an optical disk) using a lens or the like into two minute light spots, An erasable optical recording and reproducing device that can record and reproduce a signal with one optical spot, erase the signal with the other optical spot, and repeatedly record and reproduce the signal, or record a signal with one optical spot and reproduce it with the other optical spot. The present invention relates to an optical recording/reproducing apparatus having a plurality of optical spots, such as an optical recording/reproducing apparatus capable of instantly reproducing a recorded signal.

2. Description of the Related Art An optical recording/reproducing apparatus having a plurality of optical spots was previously proposed in Japanese Patent Application No. 59-125906. This is an example of an erasable optical recording/reproducing device that uses the thermal energy of a laser beam to reversibly change the optical density of the recording thin film of an optical disk. Dislocations between crystalline states or between one amorphous state and another stable amorphous state are repeatedly used.

The device as described above has a plurality (two) of light spots. An example of the configuration is shown in FIG.

Figure 2 shows a disk-shaped optical recording medium (hereinafter referred to as an optical disk).
3 is a guide track provided on the optical disk. On the guide track 3, there is a circular first optical spora L and a second oval optical spora long in the track direction. The configuration is such that a circular first optical spora) L is used to record and reproduce a signal, and an oval second optical spora) M is used to erase the signal.

In the device using two light spots as described above, since the width of the guide track 3 is generally very small, about 0.6 μm, the first light spora (L) and the second light spot in the direction perpendicular to the track are It is necessary to maintain the relative position with the second light spot M with high accuracy and stability. For this reason, the above-mentioned device has a structure that prevents the relative positional deviation of the two light spots, and the structure is shown in FIG. 3.

In FIG. 3, the part surrounded by a dashed line indicates an optical head, and 7 is a semiconductor laser that generates light of wavelength λ, and its output beam is indicated by e. A condenser lens 8 condenses the output light of the semiconductor laser having a magnification into a substantially parallel light beam. 9 is a filter that transmits light with wavelength λ and reflects light with wavelength λ2, which will be described later; 10 is a filter with wavelength λ4. A polarization beam splitter effective for light of λ2, 11 a % wavelength plate for the wavelength λ, and 12 an aperture lens.

The light beam l of the semiconductor laser 7 passes through these optical elements and enters the aperture lens 12. The aperture lens 12 narrows down the incident light beam E to create a substantially circular light spora L on the guide track 3.

13 is a semiconductor laser that generates a light beam m of wavelength λ2, and 14 is a condenser lens. 22 is a reflective mirror,
It has a rotatable configuration.

Reference numeral 16 denotes a wavelength plate for wavelength λ2, and the filter 16 has a function of transmitting light of wavelength λ2 and reflecting light of wavelength λ2. Light beam m emitted from semiconductor laser 13
is a reflecting mirror 22. After being reflected by the polarizing beam splitter 1o and passing through the wavelength plate 16, it is reflected by the filter 16, passing through the wavelength plate 16 again, this time passing through the polarizing beam splitter 1°, and passing through the K wavelength plate 11 to the aperture. Sirens 12
incident on . The diaphragm lens 12 forms an oval optical spora M on substantially the same guide track 3 as the optical spora L, and the major diameter direction thereof coincides with the direction of the guide track.

In order to arrange the light spots L and M on the guide track as shown in FIG. This can be achieved by giving it a value.

The light reflected from the optical disk of the original beam l is reflected by the aperture lens 1.
2. Wave plate 11. Polarizing beam splitter' O*K
Wave plate 16. The light passes through a filter 16 and is guided to a photodetector 18 via a lens 17 for obtaining control signals for focus and tracking.

The photodetector 18 is composed of a PIN diode divided into four parts,
From these outputs, a re-emission signal, focus of the first light spot L, and a control signal for tracking are obtained using a known method.

On the other hand, the reflected light of the light beam m from the optical disk passes through the aperture lens 12+X wavelength plate 11. Here, for example, the wavelength λ
By using a semiconductor laser with wavelength λ 1 of 780 nm and wavelength λ 2 of 830 nm, most of the light transmitted through the % wavelength plate 11 is reflected by the polarizing beam splitter 10 toward the semiconductor laser 7 side, and further reflected by the filter 9. The light is guided to a two-part photodetector 19. A tracking control signal for the second optical spoiler (M) is obtained from the differential output of this two-split photodetector 19.

The aperture lens 12 is held movably by an aperture lens driving element 20 in the original axis direction for focusing and in the two-wheel direction in a direction perpendicular to the track for tracking. Therefore, the first optical spoiler L and the second optical spoiler M are simultaneously moved in the direction perpendicular to the track by the aperture lens driving element 2o and by the same amount. This diaphragm lens drive element 2o may have a known voice coil type structure, and can perform focus control corresponding to surface runout of the optical disk of the first light spot (L) and tracking control against eccentricity of the track using known technology. .

At this time, as described above, the second optical spora) M also moves in the same way. However, since a rotatable reflection mirror 22 is provided in the optical path of the second light spora)M, the rotation of the reflection mirror 22 causes the second light spot M to change from the first light spot)L.
It becomes possible to move independently of the track in the direction perpendicular to the track.

This is because the angle of incidence of the light beam m incident on the aperture lens 12 in the direction perpendicular to the track changes.

As mentioned above, the tracking control signal for the second light spot (M) is obtained from the two-split photodetector 19, but the tracking control signal for the second light spot (M) is obtained by rotating the reflection mirror 22 using a known technique. Tracking control is possible.

Although the driving means for moving the second source spot M has been described as the rotatable reflection mirror 22, driving means for moving the semiconductor laser 13 using a piezoelectric element has also been proposed.

As described above, the first driving means moves the two optical sporatra tracks together in a substantially perpendicular direction, and the second driving means moves the second optical spot independently of the first optical spot. In the optical recording and reproducing apparatus having a plurality of optical sporatra, even if a relative positional deviation occurs in the vertical direction in the track of two optical spots for some reason, By applying tracking control to the driving means, it is possible to accurately track the guide track, and it is possible to prevent relative positional deviation between the two light spots.

Problems to be Solved by the Invention However, with the above configuration, it is difficult to guarantee that the two light spots always track the same guide track. There is a possibility that separate guide tracks may be tracked, and in order to prevent this, the configuration of the device is complicated and expensive.

This is because if the relative positional deviation between the two light spots is more than % of the pitch of the guide track, the tracking control signals obtained from each light spot will be generated by different guide tracks. This is because tracking control is applied. In other words, in order for the two light spots to always track the same guide track, the relative positional deviation between the two light spots must be less than % of the pitch of the guide track.

However, in the conventional second driving means for moving the second light spot (means for moving the rotatable reflection mirror 22 or the semiconductor laser 13), a configuration in which the relative positional deviation between the two light spots is small is required. This requires high precision and complexity. It depends on the configuration of the optical head and the pitch of the guide track in order to keep the relative positional deviation between the two light spots to less than % of the pitch of the guide track, but in the case of the rotatable reflecting mirror 22, Approximately 0.
2 mrad, and in the case of a means for moving the semiconductor laser 13, the displacement would be about 0.5 μm, but in reality there are other causes of relative positional deviation between the two original spots, so the second drive This is because a very small deviation of 9 or less of the above value is generally required as an allowable deviation. That is, the conventional second drive means is required to have a movable structure and maintain a neutral position with extremely high precision.

In view of this, an object of the present invention is to provide an optical recording/reproducing device having a plurality of light spots, which has a simple configuration and allows two light spots to always track the same guide track.

Means for Solving the Problems The present invention provides an optical recording and reproducing system having a plurality of light spots, which includes a prism disposed in the optical path of an optical means for forming a plurality of light spots, and a means for fully rotating the prism. It is a device.

Function The present invention is constructed using the above-mentioned prism, and a prism is generally defined as a transparent body having two or more planes that are not parallel, and as shown in FIG. When the light is incident, the angle δ formed by the incident angle φ1 and the output angle φ2 changes depending on the incident angle φ1. By rotating the prism, the incident angle φ changes, and the apex angle α=3°
Figure 5 shows the angular change in δ when the prism is rotated. In Figure 5, the horizontal axis is the rotation angle θ (incident angle φ, = θ and θ = 0 at normal incidence), and the vertical axis is represents the angle change of δ and the amount of movement of the light spot on the optical disk.

As is clear from Fig. 5, as the rotation angle θ changes, δ
The angle change is minute. Therefore, if the prism and its rotating means are arranged in the optical path of the optical means that forms the light spot, it becomes optimal as the second driving means for moving the second original spot. In other words, compared to conventional drive means, the tolerance range for maintaining the neutral position of the drive means is much larger, and the drive means has a simpler configuration. (Compared with conventional driving means, for example, a rotating mirror, the allowable range differs depending on the prism and rotation angle 0, but in the prism shown in Fig. 5, the rotation angle θ = -
If the neutral position is set near 10', the allowable range becomes approximately 100 times larger. ) Embodiment FIG. 1 shows the configuration of an optical recording/reproducing apparatus having a plurality of optical spots in a first embodiment of the present invention. In FIG. 1, the part surrounded by a dashed line indicates an optical head, and parts that are the same as those of the conventional device are given the same numbers. 1 is the apex angle a
2 is a prism 10 rotation means. The rotating means 2 can be realized using a known technique, for example, a motor.

In this embodiment, the optical spoilers L and M shown in FIG. 2 are formed in the same manner as described in the conventional apparatus, and tracking control signals from the respective optical spots can be detected. The difference from the conventional device is that the output light beam m&i from the semiconductor laser 13 passes through the prism 1 after passing through the condenser lens 14. When the optical spora) M is subjected to tracking control, the prism 1 is rotated by the rotation means 2.

If the second driving means for moving the second original spot M is the prism 1 and the rotating means 2, the driving means The permissible range of accuracy for maintaining the neutral position of the motor is wide, and the drive means does not require high precision, which simplifies the structure.

FIG. 6 shows a second embodiment of the invention. FIG. 6 shows only the configuration of the second driving means for moving the second optical spora) M, 23 is a means for limiting the rotation range of the prism 1, and the other configurations are the same as in the first embodiment. It is the same.

The rotation range limiting means 23 is configured to prevent the second optical spont M from moving by less than % of the guide track by the second driving means. Since this limiting means 23 has a large allowable range of rotation angle θ, it is not required to have great accuracy.

This can prevent tracking control from being applied to the two original spots on separate guide tracks even if the second driving means is moved due to some reason, such as photographing.

By the way, the angle of incidence φ1 on the prism in the embodiment of the present invention
The relationship between the angle δ between (=rotation angle θ) and the output angle φ2 is as follows:
As shown in FIG. 5, when selecting the prism and its rotation angle as the second driving means, it is undesirable to select a position near where δ becomes the minimum. That is, the condition for minimizing δ is
Incident angle φ1 = exit angle φ2, but in the vicinity, the change in δ with respect to rotation angle θ is very small, which is good for widening the tolerance range of deviation of the driving means, but on the contrary, tracking control In order to do this, it is necessary to widen the rotation range. If the rotation range is too large, the parallel movement of the optical axis of the light beam will become large, which is not preferable. Therefore, when using a prism and its rotation means as the second driving means,
It is better to select an angle of incidence of the original beam onto the prism such that the angle of incidence φ1 does not equal the angle of exit φ2.

In addition, in the embodiment, the description has been made assuming that there are two light spots, but the present invention can also be applied to an apparatus having two or more light spots.

As described in detail, according to the present invention, in an optical recording/reproducing device having a plurality of light spots, it is possible to always track the same guide track with a simple configuration. The practical effects are great.

[Brief explanation of drawings]

Fig. 1 is a plan view showing an embodiment of the present invention, Fig. 2 is a perspective view showing the arrangement of an optical disk and a source spot, Fig. 3 is a plan view showing the previously proposed device, and Fig. 4 is a plan view showing the invention. FIG. 5 is a characteristic diagram showing the action of the prism, and FIG. 6 is a plan view showing another embodiment of the present invention. 1... Prism, 2... Prism rotation means, 3... Guide track, 7, 13...
... Semiconductor laser, 8.14 ... Condensing lens,
12...Aperture lens, 18.19...
Photodetector. Name of agent: Patent attorney Toshio Nakao and 1 other person No. 3
Figure 4 θ″″fl No. 51! ! Figure 6

Claims (3)

[Claims] (1) Using a plurality of semiconductor lasers and the light beams emitted from the plurality of semiconductor lasers using the same aperture lens,
an optical means for forming a plurality of light spots on straight lines substantially parallel to an information track of an optical recording medium; a driving means for moving the plurality of light spots together in a direction substantially perpendicular to the information track; and a drive means for moving the plurality of light spots together in a direction substantially perpendicular to the information track; 1. An optical recording/reproducing device having a plurality of optical spots, comprising at least one prism disposed in an optical means for forming spots, and a rotating means for rotating the prism. (2) An optical recording/reproducing device having a plurality of optical spots as set forth in claim 1, wherein the rotating means includes means for limiting a rotating range. (3) An optical system having a plurality of light spots according to claim 1, characterized in that the prism is arranged such that the angle at which the light beam emitted from the semiconductor laser enters the prism and the angle at which it exits the prism are different. Recording and playback device.