JPS59127242A - Optical recording and writing device - Google Patents

Abstract

PURPOSE:To realize a two-beam optical head which provides highspeed writing by irradiating a recording medium with light which has less intensity than in writing to the recording medium in an elliptic spot which has a long axis in an information writing advance direction and thus heating the medium preliminarily. CONSTITUTION:In a figure, 25 is a semiconductor laser light source for writing. A projected beam from this light source 25 forms a circular spot 13 on a track 11 on the surface of the recording medium 10. On the other hand, 26 is a semiconductor laser light source for preheating which is different in wavelength from the light source 25. A projected beam from this light source 26 forms an elliptic spot 12 on the track 11 on the surface of the recording medium 10. This light has a level lower than a threshold level. The laser beams from those light sources 25 and 26 are shifted in focusing point by the aberration of a condenser lens 15. Arrows indicate advance directions of the light beams. This beam constitution is employed to preheat the recording medium by the elliptic light beam 12 other than write light before information is written, shortening the time of writing by the circular beam 13.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an optical recording/writing device that writes or reproduces information by converging a light beam onto a recording medium.

In recent years, technology has advanced for optically reproducing information such as images and audio recorded on a disc-shaped recording medium as a series of concentric or spiral minute pits, and has been put into practical use as video discs, digital audio discs, etc. has been done. In addition, optical disk memories are being developed that perform not only playback but also recording and are used as memory.

Optical disk memory devices capable of such recording and playback are
Smaller than conventional magnetic disk memory devices.

It has features such as light weight, high recording density, and high reliability in terms of signal quality stability, making it ideal for home video use.

Applications are expected not only to information sources such as music, but also to file devices and file memories in terminals.

As an optical recording medium that performs such recording and reproduction, T8
Metal thin films such as and Bi', and polymeric materials containing light-absorbing dyes have been developed. Information is written on these optical recording media by being exposed to light irradiation of a certain level or higher, and the level at which the information can be written is called a threshold.

This threshold is based on the fact that information is written when the recording medium is irradiated with light and reaches a certain temperature or higher. A certain amount of time is required after the writing beam is irradiated until the temperature of the recording medium rises and the information is actually written, and this time determines the information writing speed.

In a conventional optical recording head, information is written by irradiating a light beam of a voltage higher than a threshold only during writing. Therefore, the writing speed is limited by the time required for the temperature of the recording medium to rise due to the writing light, and writing cannot be performed faster than this required time. In order to increase the writing speed, it is conceivable to preheat the recording medium with a heater or the like before writing information, but this poses the problem of increasing the size of the apparatus.

An object of the present invention is to eliminate such drawbacks and provide an optical recording/writing device capable of writing information at high speed.

The present invention provides an optical recording medium in which information is written on the recording medium by the relative movement between the recording medium and the writing light beam, on which information is written only when irradiated with a light beam of a certain intensity or more. an elliptical beam forming means for irradiating the recording medium with light having an intensity lower than the intensity at which writing is performed on the recording medium in the form of an elliptical spot having a long axis in the direction in which information is written, and a wavelength different from the light beam; circular beam forming means for irradiating a circular spot with a diameter less than or equal to the short axis of the elliptical spot with a light beam having an intensity enough to overlap the rear surface of the elliptical spot in the direction of writing progress and write on the recording medium. It is characterized by

Next, details of the present invention will be explained with reference to the drawings.

1 and 2 are a plan view and a side view showing the appearance of a light beam spot on a recording medium, for explaining the operating principle of the present invention. In the figure, 10 is a recording medium, and 11 is a track on the recording medium where information is written. Reference numeral 12 is an elliptical beam, which is light at a level below the threshold, 13 is a circular beam for writing, and 15 is a condenser lens. Further, the arrow indicates the traveling direction of the light beam. When this beam configuration is used, the recording medium can be preheated by a light beam other than the writing light before information is written by the elliptical beam 12, and the writing time by the circular beam 13 can be shortened. Additionally, the elliptical stomach beam 1 with
It is also possible to know the state of the recording medium before writing by forming an image of the 20 reflected light and detecting the reflected light on the front side in the traveling direction from the image. The spot arrangement shown in FIG. 1 can be realized by adjusting the angle of incidence on the condenser lens 15 and the position of the axis of incidence as shown in FIG. 2. This elliptical beam 12
may be used, for example, without circularizing the semiconductor laser beam. This is because a semiconductor laser beam usually has an ellipticity of 2 to 3. Note that it is possible to create a condensing lens with no aberrations at different wavelengths, but if the two beam spot diameters are about the same, then if the elliptical beam spot is shifted from the focal point due to aberrations, the beam as shown in Figure 1 can be obtained. The relationship between the magnitudes of is obtained.

FIG. 3 is a configuration diagram of an optical head according to an embodiment of the present invention. In the figure, 25 is a semiconductor laser light source for writing. The output beam emitted from this light source 25 is collimated by a lens 23, circularized by a prism 24, reflected by a wavelength selection plate 20, passed through a polarizing beam splitter 22, and then passed through a quarter wavelength (λ/4) plate 21. The light becomes a circularly polarized wave and is irradiated onto the recording medium 10 surface.

The light reflected from the recording medium 10 is converted into a linearly polarized wave that is 90° different from the incident light by a λ/4 plate 21 and is converted into a linearly polarized wave by a beam splitter 2.
2 and is reflected by the wavelength selection plate 32. Furthermore, after passing through the lens 24, one half of the light enters a two-part focus error detection detector 28 and the other half enters a two-part track error detection detector 29 through a knife/mirror 30. Detection of this focus error is based on the Knifezi method, and detection of track and track errors is based on diffracted light from a group of tracks on the recording medium.

The focus and tracking servo systems are driven using the error signal, and actuator mechanisms for these servos can be realized using conventionally known optical head technology.

On the other hand, 26 is a semiconductor laser light source for preheating and has a wavelength different from that of the light source 25. The emitted beam from the light source 26 passes through the wavelength selection plate 32, is reflected by the polarizing beam splitter 22, becomes a circularly polarized wave by the λ/4 plate 21, and is irradiated onto the surface of the recording medium 10. The light reflected on the surface of the recording medium passes through the λ/4 plate 21, where the linear polarization is changed by 90 degrees from that at the time of incidence, through the beam splitter 22, and then through the wavelength selection plate 20.

Further, the image is enlarged and imaged by the lens 34, and only half of the image is made incident on the entire detector 27 by the knife 31 located at the image forming position. At this time, the reflected light from the first half of the elliptical beam 12 on the recording medium 10 is made to reach the detector 27. This spot arrangement is achieved by slightly shifting the axis of the Class 23 beam. Furthermore, by setting the wavelength selection plate 20.32 at a certain angle, the wavelength selection plate 20.32 has the function of reflecting the laser light from the laser light source 25 and allowing the laser light from the laser light source 26 to pass through.

Note that an arrow 35 in this figure indicates the direction of movement of the optical head with respect to the recording medium 1o. The focal positions of the laser beams of these light sources 25 and 26 can be shifted by the aberration of the condensing lens 15, and focus control may be performed so that the circular beam for writing from the light source 25 is focused on the recording medium lo.

With the above configuration, a two-beam optical head capable of high-speed writing can be realized.

[Brief explanation of the drawing]

Fig. 1 is a plan view of a beam spot on a recording medium to explain the present invention in detail, Fig. 2 is a side view showing the beam position relationship when Fig. 1 is viewed from the side, and Fig. 3 is an embodiment of the present invention. FIG. In the figure, 10...recording medium,
11...Track of recording medium, 12...
・Elliptical beam for preheating, 13...Circular beam for writing, 15...Condensing lens, 20.32...
... Wavelength selection plate 1.21 ... λ/4 plate, 2
2...Polarizing beam splitter, 23.34...
... Lens, 24 ... Prism, 25 ...
... Laser light source for writing, 26 ... Laser light source for preheating, 27 ... Detector, 28.29.
...2-divided detector, 30... group/naifetsuji and mirror, 31...... naivetsuji. \~~~~---/ /Heh// Hand 17 Hayabusa 2V

Claims (1)

[Claims] In an optical recording/writing device in which information is written on the recording medium by a relative movement between a recording medium and a writing light beam on which information is written only when irradiated with a light beam of a certain intensity or more, the recording elliptical beam forming means for irradiating the recording medium with light having an intensity lower than the intensity at which writing is performed on the recording medium in an elliptical spot having a major axis in the information writing progress direction; The recording medium has a circular spot having a diameter equal to or smaller than the short axis of the spot, and includes a circular beam forming means for irradiating light with an intensity sufficient to write on the recording medium so as to overlap the rear surface of the elliptical spot in the direction of writing progress. Optical recording and writing device.