JPS5817978B2 - Kogaku Tekikiki Rokusai Seisouchi - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an apparatus for recording, reproducing, and erasing information by irradiating a recording disk with a light beam.

There are mechanical, magnetic, and optical methods for recording and reproducing various types of information, but among them, recording and reproducing video and audio signals requires high-density recording and high-quality reproduction signals. Recording and reproducing methods using optical methods have been actively researched and developed in recent years.

As optical memory materials that can be recorded and reproduced by these devices, silver halide films, amorphous photodichromic materials, thermoplastics, and the like have been widely studied.

From a usage perspective, these materials can be used to record information such as images on a surface like photographic film, or to record digital information from a computer or analog information such as image and audio signals in series in black. There is.

Regarding the latter black recording reproduction method, the recording medium is tape-shaped,
Alternatively, recording, reproduction, or erasing is performed by attaching the recording medium to a disk-shaped base material, but basically, recording, reproduction, or erasing is performed by irradiating the surface of the recording medium with a light beam.

An example of an amorphous optical memory material that facilitates high-density recording and reproduction will be described below.

In this case, recording is performed by imparting both transmittance and reflectivity (increase in optical density) properties to the recording material, depending on the intensity and irradiation time of the light beam.

That is, by irradiating the recording material with a light beam, the recording material is brought into a molten state, and by cooling it slowly, the material is crystallized and has reflective properties.

This phenomenon is a record, and when the material is rapidly cooled from the molten state, it becomes a solid solution while remaining amorphous.

This is erasure.

When recording or erasing, in terms of source energy, it is necessary to provide light energy that is greater than the recording threshold energy or erasing threshold energy, respectively, but in order to perform the aforementioned slow cooling and rapid cooling, the light beam irradiation time on the recording medium must be This is achieved by changing the

Also, slow cooling and rapid cooling can be performed by changing the relative speed of the recording medium with respect to the original beam.

Next, optical recording and reproduction of such amorphous semiconductors,
Further, an optical recording/reproducing device using an erasable original memory material as a recording medium will be explained based on the drawings.

FIG. 1 shows the configuration of an optical recording/reproducing apparatus.

1 is a light source such as a laser, and 2 is an optical modulator that modulates the intensity of a light beam a emitted from the light source 1 according to an electrical input signal from a terminal A.

3 is a slit that blocks unnecessary light.

4 is a projection lens for enlarging the beam diameter of the original beam modulated by the optical modulator 2, and 5 is a total reflection mirror, which is used to change the direction of light.

6 is a beam splitter through which the original beam a' reflected by the total reflection mirror 5 is transmitted; 7 is a voice coil having the function of moving the objective lens 30 up and down.

The light beam a' is focused into a minute spot by the objective lens 30, and a minute light spot is created on the recording disk made up of the recording material 8 and the rotating base material 9.

Reference numeral 10 denotes a motor for rotating the recording disk, which is driven by a rotating body drive circuit 11.

12 is a motor support device mounted on the transfer body 14 which is moved in the direction of arrow 15 by the transfer motor 13;
It moves in the direction of arrow 15 together with transport body 14 .

16 and 17 are light receiving elements installed side by side, 1B,
19 is an amplifier for amplifying the outputs of the light receiving elements 16 and 170;
0 is a differential amplifier that amplifies the output of the difference.

Reference numeral 21 denotes a drive circuit that generates an output for driving the voice coil 7 in the vertical direction of the arrow 22 based on the difference between the outputs of the light receiving elements 16 and 170.

The operation of the embodiment configured as above will be explained.

The original beam a generated by the light source 10 is modulated by the optical modulator 2 according to the signal applied to the terminal A.

Among the modulated light, unnecessary light is blocked by a slit 3, the beam diameter of the necessary original beam a' is expanded by a lens 4, and the traveling direction is changed by a total reflection mirror.

This original beam a' enters the objective lens via the beam splitter 6, and is narrowed down to a minute spot on the recording disk.
A point is irradiated.

The reflected light at this point X enters the light receiving elements 16 and 17 via the objective lens 30 and the beam splitter 6.

This incident light is photoelectrically converted, amplified by an amplifier, a difference is detected by a differential amplifier 20, and is applied to a drive circuit 21 for the voice coil 7.

As shown in FIG. 1, a voice coil 70, an objective lens 30,
When the distance H between the recording disk and the recording disk is exactly within the depth of focus, the reflected light C at the point X on the recording disk is reflected by the light receiving element 16.
, 17, so that the light receiving elements 16, 17 are evenly illuminated.
is installed, so the differential amplifier 20 does not generate an output.

Therefore, the voice coil 7 maintains its current position.

On the other hand, if the distance H becomes a value outside the above depth of focus, the light receiving element 1
Since there is a difference in the amount of light received by 6 and 17, the differential amplifier 20 generates a positive or negative output depending on the variation in distance H.
The drive circuit 21 drives and controls the voice coil 7 so that the distance H falls within the depth of focus.

FIG. 2 shows the erasing state in the above device.

Now, as shown in the figure, signals 23 and 23' are recorded by the output of the electrical input signal applied to terminal A.

Reference numerals 24, 25, and 26 respectively indicate beam spots during erasing, and indicate variations in the irradiation position under tracking control.

Furthermore, since the same focus control as during recording is performed, the data is erased using the same minute spot as during recording.

Therefore, if there is a long signal such as the recording signal of No. 23, it is necessary to repeatedly irradiate the erase beam continuously and quickly, and there is a high possibility that unerased portions will be left behind.

The present invention compensates for the above drawback by irradiating a light spot with a diameter larger than the minute spot during recording and slightly larger than the recording track width during erasing, and this will be explained below.

FIG. 3 shows the main part of an embodiment of the present invention.

In the apparatus shown in FIG. 1, instead of the projection lens 40, a lens switching device 27 having projection lenses 4°4' with different focal lengths is provided at that position, and during recording and reproduction, the projection lens 4 is changed to the erasing lens. In such cases, the lenses are switched such as the projection lens 4'.

The projection lens 4 has a small focal length f1 and is used for recording and reproduction, and the projection lens 4' has a focal length f2 and is used for erasing.

That is, it is assumed that the relationship fl<f2 holds true.

FIG. 4 shows the optical path of the original beam passing through the projection lenses 4, 4', passing through the voice coil 70 and the objective lens 30, and irradiating the recording disk 2.

Since the light beam a' passing through the projection lens 4 having the focal length f1 has a small focal length, it enters the objective lens of the voice coil 7 as a nearly parallel light, creating a minute spot on the recording disk.

Since the erasure projection lens 4' has a focal length f2, the light beam is focused just before it enters the voice coil 70 and the objective lens 30, and then passes through the objective lens 30 and is recorded as parallel light as shown in the figure. Irradiate the disk □.

As shown in Fig. 4, the erasing beam becomes parallel light and irradiates the recording disk, but as shown in Fig. 5, the erasing beam spot 28 is slightly larger than the track width 29. This is what we do.

In this case, since the erasing beam is slightly wider than the track width, a problem arises as to whether or not adjacent recording signals will be erased.

However, although not shown in the drawings, as described in the focus control method above, two photodetecting elements 16 and 17 are used to detect the light transmitted through the recording disk, and the inclination of the total reflection mirror 5 is Tracking can be performed by changing the amount corresponding to the difference in the amount of light received by the detection elements 16° and 170.

As mentioned in the focus control method, the two photodetecting elements are
When the beam spot 28 is at the center of the track, the beam spot 28 is installed so that the transmitted light enters the two detection elements with equal output.

Since the tracking control is performed as described above, even if the erasing beam spot 28 is slightly larger than the track width 29, it is possible to erase adjacent recording signals.

There is no payment.

Further, since the erasing beam spot 28 is slightly wider than the track width, it is not necessary to repeatedly irradiate the erasing beam spot as quickly as described above, and it is possible to prevent unerased areas.

Further, as shown in FIG. 4, since the parallel light is used for erasing, there is no need to perform focus control.

Although it has been described above that erasing is performed using two projection lenses with different focal lengths, the focal lengths of the projection lenses do not have to be the same when erasing.

Also, whether the parallel light is circular or elliptical, -
It is something that cannot be avoided.

Note that even if the beam is not parallelized, the same effect can be obtained if erasing can be performed with a beam spot diameter larger than the beam spot diameter during recording and reproduction.

As is clear from the above embodiments, the present invention switches the lenses placed in the optical path of the original beam irradiated onto the recording disk, so that appropriate light beams are irradiated respectively during recording and erasing. In particular, it has the feature of reliably preventing uneven erasing, which has been a drawback of conventional devices.

[Brief explanation of drawings]

FIG. 1 is a configuration diagram of an optical recording/reproducing apparatus, FIG. 2 is a diagram showing the irradiation state of the erasing beam spot, FIG. 3 is a perspective view of the main parts of an optical recording/reproducing apparatus according to an embodiment of the present invention, and FIG. FIG. 4 is a diagram showing the optical path of the light beam, and FIG. 5 is a diagram showing the irradiation state of the erasing beam spot according to the embodiment of the present invention. 1...Light source, 4,4'...Projection lens, 8...Recording material, 9...Rotating base material,
27...Lens switching device.

Claims (1)

[Claims] 1. In a recording/reproducing device that records, reproduces, and erases information by irradiating a light beam from a light source onto a recording medium through an objective lens, there is a focal distance between the light source and the objective lens, and The first and second projection lenses, which have different values, are configured to be selectively inserted and inserted during recording/reproduction and erasing, and by switching between the first and second projection lenses, the recording medium is irradiated with light during recording. 1. An optical recording/reproducing apparatus characterized in that the diameter of a light spot irradiated onto the recording medium during erasing is set to be smaller than the diameter of a light spot.