JPS615447A - Erasable optical recording and reproducing device - Google Patents

Abstract

PURPOSE:To repeatedly perform recording and reproduction accompanied by erasion, by providing a driving means which moves a light spot for recording and reproduction in the direction vertical to a track together with another light spot for erasion and another driving means which drives the light spot for erasion only in the direction vertical to the track. CONSTITUTION:A light beam (l) outputted from a semiconductor laser 7 for recording and reproduction which produces light having a wavelength lambda1 forms an almost circular light spot L on a guide track 3 after it is reflected by a polarization beam splitter 10 and passed through a diaphragm lens 12. Another light beam (m) outputted from another semiconductor laser 13 for erasion which produces light having a wavelength lambda2 forms an oval light spot M, the direction of whose major axis coincides with the track direction, on almost the same track 3 as the one on which the light spot L is formed after it is reflected by the splitter 10. The lens 12 is held by a lens driving element 20 under conditions where the lens 12 can be moved in the direction of optical axis and in the direction vertical to the track. The laser 13 is fixed to one end of a bimorph type piezo-electric element 21 and, when a voltage is applied across the element 21, only the light spot M is moved in the direction vertical to the track direction. Therefore, recording and reproduction accompanied by erasion can be performed.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention uses a laser beam with a lens or the like to
A disc-shaped recording medium (hereinafter referred to as an optical disk) is irradiated with a very small light spot to record and reproduce signals at high density, and the recorded signal is erased by irradiation with a light spot different from the above-mentioned light spot, and then repeated. The present invention relates to an erasable optical recording and reproducing device that can record and reproduce signals.

Conventional Structure and Problems As an erasable optical recording/reproducing device as described above, a method has been proposed in which the optical density of a recording thin film of an optical tissue is reversibly changed using the thermal energy of a laser beam. .

This is due to the dislocation between the amorphous and crystalline states of the recording thin film,
Alternatively, dislocations between one amorphous state and another stable amorphous state are repeatedly utilized.

We have previously proposed a light spot suitable for irradiating such an erasable optical disc.

As shown in Figure 1, this makes it possible to irradiate a circular first light spot used as a recording or recording/playback spot onto the same track with a second oval light spot that is elongated in the track direction and used for erasing. This is a method of providing

However, due to the two beams, the following problem occurs when the reproduced signal is monitored with the first light spot and erased with the second spot.

One is that the device requires a complicated adjustment mechanism in order to accurately position the second light spot on the track formed by the first light spot on the optical disc, as shown in FIG. Also, parts are required to be highly accurate.

The second is when there is a relative positional shift between the first original spot and the second light spot in the direction perpendicular to the track due to aging, temperature changes, etc. This will have a serious negative impact on quality.

Third, there is a problem in transferring the optical head in the radial direction of the original disk, and it is difficult to use a transfer method such as the swing arm method which is well known in magnetic disk drives.

Even in the linear transfer method, the measures mentioned in the first section are required.

Purpose of the Invention In view of the above-mentioned problems, the present invention provides an erasable optical recording and reproducing device that does not require a highly accurate relative position between a track and a first light spot and a second light spot in the direction of normal force. The purpose is to provide.

Structure of the Invention The present invention provides a first source spot for recording and reproduction of light beams emitted from a first semiconductor laser and a second semiconductor laser by using the same aperture lens, and a first light spot for recording and reproducing. means for creating a second light spot for erasing adjacent to each other; a first driving means for moving the first original spot and the second light spot in the same direction substantially perpendicular to the trunk on the optical disk; A second driving means moves only two light spots in a direction substantially perpendicular to the trunk.

DESCRIPTION OF EMBODIMENTS Specific embodiments of the present invention will be described below with reference to the drawings.

FIG. 2 shows a radial cross-section of an optical tissue with an optical guide trunk for use in the present invention.

Here, as an example of an optical guide track, an example of a grooved optical disk having grooves all over the signal recording area on an optical disk is shown. A transparent material is used as the base material 2 of the optical tape 1, and grooves having a width W and a depth d and a track pitch P are formed thereon as guide tracks 3 in a spiral or concentric shape. A recording thin film 4 having a thickness t is formed thereon by a method such as vapor deposition, and a protective layer 6 is provided thereon. The guide track 3 has a depth d so that it functions as an optically detectable guide track for the laser irradiation light 6.

A width W is set. The guide track 3 allows the irradiated light 〇 to record or reproduce a signal along a specific groove.

FIG. 3 shows an embodiment of the present invention.

In the figure, the part surrounded by a dashed line indicates an optical head, 7 indicates a semiconductor laser that generates light of wavelength λ, and 4 indicates an output optical beam thereof.

A condenser lens 8 condenses the divergent output light of the semiconductor laser into a substantially parallel light beam.

9 is a filter that transmits light with a wavelength λ1 and reflects light with a wavelength λ2 (described later); 1o is a filter with a wavelength λ1. A polarizing beam splitter effective for light of λ2, 11 a % wavelength plate for the wavelength λ1, and 12 an aperture lens.

The optical beam El-1 of the semiconductor laser 7 passes through these optical elements and enters the aperture lens 12. The aperture lens 12 constricts the incident light beam r to form a substantially circular light spot L on the guide track 3.

13 is a semiconductor laser that generates a light beam m having a wavelength λ2, and 14 is a condenser lens.

Reference numeral 15 denotes a y-wave plate for wavelength λ2, and filter 16 has a function of transmitting light of wavelength λ1 and reflecting light of wavelength λ2. Light beam m emitted from semiconductor laser 13
is reflected by the polarizing beam splitter 1° and passes through the wave plate 1.
After passing through the polarizing beam splitter 10 , the light is reflected by the filter 16 , passes through the Z wavelength plate 16 again, this time passes through the polarizing beam splitter 10 , passes through the K wavelength plate 11 , and enters the aperture lens 12 . Light spot at aperture lens 12) Guide track 3 which is almost the same as L
A light spot (M) having an oval shape and whose major axis direction coincides with the direction of the guide trunk is formed on the top. Light spots like this)
In order to arrange L and M on the guide trunk as shown in FIG. This can be achieved by holding it.

The oval light spot (M) can be obtained, for example, by reducing the beam width in the track direction of the light beam m incident on the aperture lens 12, or by another method, but the details thereof will be omitted.

The circular first optical spot (L) thus obtained is used for recording or recording/reproduction, and the oval second optical spot M is used for erasing signals.

The reflected light from the optical disk of the light beam l is passed through the aperture lens 1.
21% wave plate 11. Polarizing beam splitter 10, Z wave plate 15. The light passes through a filter 16 and is guided to a photodetector 18 via a lens 17 for obtaining focus and tracking control signals. The photodetector 18 is composed of four-divided PIN diodes, and from the outputs of these PIN diodes, a reproduction signal, a focus of the first light spot L, and a control signal for tracking are obtained by a known method.

On the other hand, the reflected light of the light beam m from the optical disk passes through the aperture 9 lens 129% wavelength plate 11. For example, by using a semiconductor laser with a wavelength λ1 of 780 nm and a wavelength λ2 of 830 nm, most of the light transmitted through the wavelength plate 11 is sent to the polarizing beam splitter 10 from the fn body laser 7 side to the anti-#T The white light is further reflected by the filter 9 and guided to the two-divided light receiving element 19.

A tracking error signal of the second light spot M for erasing is obtained from the differential output of this two-split light receiving element 19.0 The aperture 9 lens uses an aperture lens driving element 2o to track the optical axis direction for focusing and tracking for tracking. It is held movable in two axes perpendicular to the
It is. Therefore, the first light spot (L) and the second light spot (M) are moved simultaneously and by the same amount in the direction perpendicular to the track by the aperture lens driving element 2o. This diaphragm lens driving element 2o may have a well-known voice mile type structure, and the details thereof will be omitted, but for example, the diaphragm lens may be held by an elastic body, and may be composed of a focusing coil, a magnetic circuit, a tracking coil, and a magnetic circuit. can be adopted, and focus control corresponding to the surface wobbling of the optical disk of the first light spot L using known technology;
Tracking control for track eccentricity can be performed.

At this time, the second light spot M also moves in the same way as described above.

Next, a means for driving only the second optical spot (M) in a direction perpendicular to the trunk will be described.

Reference numeral 21 denotes a bimorph type piezoelectric element, which is formed by bonding a plate-shaped piezoelectric element A and a piezoelectric element B together.

An erasing semiconductor laser 13 is fixed to one end of the bimorph piezoelectric element 21'' either directly or via a member not shown, and the other end is fixed to a base (not shown) of an optical head.Bimorph type By applying a voltage to the piezoelectric element 21, the semiconductor laser 13 can be slightly moved in the direction of arrow Y.
By making the direction of movement perpendicular to the optical track,
Only the second light spot M for erasing is the first light spot)L
It becomes possible to move independently of the track in the direction perpendicular to the track. This is because only the angle of incidence in the direction perpendicular to one trunk of the light beam m incident on the aperture lens 12 changes. A tracking error signal of the second light spot M for erasing is obtained from the differential output of the two-split light receiving element 19 described above, and this tracking error signal is processed by a circuit using a known technique and sent to the bimorph piezoelectric element 21. Tracking control of the second optical droplet M can be performed by applying a voltage.

FIG. 4 shows another embodiment of means for driving only the second optical spot (M) in a direction perpendicular to the track. Fourth
In the figure, reference numeral 22 denotes a total reflection mirror, which has a structure similar to a known rotating tracking mirror and rotates in the direction of the arrow. Due to this rotation, only the angle of incidence in the trunk and vertical direction of the light beam m incident on the aperture lens 12 changes, and only the second source for erasing M is transferred to the first light beam L. It can move independently in the direction perpendicular to the track.

In FIGS. 3 and 4, the first light spot L and the second original spot M are moved together in the direction perpendicular to the track using the aperture lens driving element 20, but the required driving force is However, a configuration in which the entire optical head is driven to perform tracking control may also be used.

Effects of the Invention According to the present invention, the first driving means for moving the first optical spot for recording and reproduction and the second original spot for erasing together in a direction substantially perpendicular to the tranoke; Since the second light spot is configured with a second driving means that moves the light beam in a direction substantially perpendicular to the track, the second light spot must accurately track the track created by the first light spot, resulting in good erasure. It is possible to obtain an optical recording and reproducing device that can repeatedly perform recording and reproducing operations. In addition, the relative positional accuracy of the first light spot and the second light spot in the vertical direction with respect to the trunk during assembly is not required as much as in the conventional case, which has the effect of reducing assembly costs, and its practical value is high. .

[Brief explanation of drawings]

FIG. 1 is a perspective view showing the arrangement of an optical disk and a light spot used in the present invention, FIG. 2 is a configuration diagram showing a partial cross section of the optical disk, FIG. 3 is a plan view showing an embodiment of the present invention, and FIG. The figure is a plan view showing another embodiment of the invention. 1... Original disk, 3... Guide track, 7°13... Semiconductor laser, L... First light spot, M... Second light spot. Name of agent: Patent attorney Toshio Nakao and 1 other person No. 1
Figure 4

Claims (2)

[Claims] (1) A first semiconductor laser for recording and reproducing, a second semiconductor laser for erasing, and a light beam emitted from the first and second semiconductor lasers for recording and reproducing using the same aperture lens. means for creating a first optical spot for erasing, and a second optical spot for erasing located approximately on a track formed by the first optical spot on the optical disk and close to the first optical spot; , a first driving means for moving the first light spot and the second light spot together in a direction substantially perpendicular to the track; and a second drive means for moving only the second light spot in a direction substantially perpendicular to the track. An erasable optical recording and reproducing device having a drive means. (2) The erasable optical recording/reproducing device according to claim 1, wherein the second driving means is configured to optically drive the second semiconductor laser in a direction perpendicular to the track.