JPS5998335A - Information recording and reproducing device - Google Patents

Abstract

PURPOSE:To execute recording and reproducing to and from every optical recording medium different in characteristic by detecting a reflected light of a light projected to an optical recording medium, rotating a polarizing plane rotating element by its output, and making the transmission light quantity optimum in accordance with recording mediums whose recording sensitivity is different from each other. CONSTITUTION:A reflected light of a light projected to an optical recording medium 2 is photodetected by a photodetector 4, its output is compared with reference voltage by a comparator 24, and a signal corresponding to its magnitude is inputted to a decoder 25. On the other hand, when recording or reproducing is selected by an operating button, a switch 22 is turned on, and a signal corresponding to it is inputted to the decoder 25 from an NAND gate 23. As for an output from the decoder 25, there are four kinds of signals with respect to recording or reproducing of the optical recording medium whose erasion is possible or impossible, but in accordance with each of them, a polarizing plane of a Faraday rotator 21 is rotated through a controlling circuit 26, it is controlled so that a passing light quantity from a light source 13 attains optimum, and recording and reproducing are executed.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improvement in an information recording and reproducing apparatus that records and reproduces information using an optical recording medium that can record information using optical energy. In the present invention, recording and reproduction means recording only, reproduction only, or both recording and reproduction. Conventionally, applications of optical recording methods include microfilms, video discs, digital audio discs, and DRAW systems. etc. are known. In recent years, a draw system using an optical recording medium in which bits (holes) are formed by depositing a totally refractive thin film such as I3i has attracted particular attention.

A feature of the draw system is that it allows the user to record and even add additional recording (ADD/ON). Furthermore, although the information recorded on the optical recording medium by forming bits cannot be erased and cannot be repeatedly recorded, it is resistant to changes over time and is most suitable for long-term storage.

On the other hand, recently, low oxidation Te, Mn B i , Gd
TbFe.

GdC0, GdFeC0, GdDyFe, GdTbF
Research and development of erasable optical recording media, such as magneto-optical materials such as eC0, have been announced one after another. However, although erasable optical recording media have the advantage of being able to be repeatedly recorded, they still have the disadvantage of being unstable in recorded information when stored for a long period of time, that is, they are susceptible to changes over time.

Therefore, it takes advantage of the advantages of both optical recording media; non-erasable optical recording media can be used as information files for long-term storage, and erasable recording media can be used for short-term or temporary information files. Examples of applications for long-term storage information files are those in fields where conventional microfilm was used, and applications for short-term or temporary information files include buffer memories for printers, etc. It is.

However, since these optical recording media generally have different recording sensitivities, there is no example in which optical recording media with different characteristics can be recorded and played back using the same device. Information files could not be created on the same device.

An object of the present invention is to solve the above-mentioned problems and provide an information recording and reproducing apparatus that can record and reproduce information on any optical recording medium with different characteristics.

In order to achieve this object, the present invention includes a light projecting means for projecting light onto the surface of an optical recording medium, and detects the level of light reflected from the optical recording medium by the light projecting means, and adjusts the recording sensitivity based on the detection level. a discriminating means for discriminating between different optical recording media; a polarization plane rotation element disposed in the optical path from the light source to the optical recording medium; and a polarizing plate disposed on the optical path on the output side of the polarization plane rotation element. , and a polarization plane control means for controlling the rotation angle of the polarization plane of the polarization plane rotation element according to the determination by the discrimination means, so that the amount of light passing through the polarizing plate can be adjusted differently for optical recording media having different recording sensitivities. It is characterized by being set to the optimum value.

Hereinafter, the present invention will be explained in detail based on illustrated embodiments.

Figures 1 to 3 show an embodiment of the present invention.
The figure is an overall schematic diagram. Reference numeral 1 denotes a cover, and setting of the optical recording medium 2 is performed, for example, by opening and closing the cover 1.

3 is a light projector such as a light emitting diode, and 4 is a light receiver for receiving reflected light, which is attached to the back side of the cover 1 together with the projector 3. A motor 5 rotates the optical recording medium 2 at a predetermined number of rotations. 6. A lens 7 for connecting a minute spot on two surfaces of the optical recording medium, a light source/astigmatism optical system described later, and 4.
This is a head portion in which a split photodetector and the like are arranged, and is moved along a guide holder 8 by a motor 9 and a pulley mechanism 10.

Reference numeral 11 is a manual operation button that allows switching between recording and playback.

FIG. 2 shows the optical system inside the head section 6. As shown in FIG. This actuator is equipped with a mechanism that moves the lens 7 in the optical axis direction to perform automatic focus control, and a mechanism that moves the lens 7 back and forth and left and right to perform tracking and time axis correction. Reference numeral 13 denotes a light source such as a semiconductor laser that generates a polarized beam.The beam is formed into a desired luminous flux distribution by a collimation lens 14, passes through a beam sinter 15, and is reflected and deflected by a total reflection mirror 16. 17 is a beam splitter 15
The polarizing plate 18 through which the light beam divided by passes passes is an astigmatism optical system consisting of, for example, a spherical lens and a cylindrical lens, and the reference numeral 19 is a four-part photodetector.

FIG. 3 is a block diagram showing the signal processing system.

20 is a polarizing plate, and 21 is a Faraday rotator, whose role is to rotate the plane of polarization of the light beam, and in combination with the polarizing plate 20, control the light energy irradiated onto the optical recording medium 2. 22 is a switch linked to the operation button 11, which is turned on by selecting recording, for example;
It is turned off by selecting playback. 23 is a Nant gate that outputs a high-level signal when the switch 22 is turned on; 24 is a comparator that compares a preset reference voltage with the level from the photoreceptor 4; 25 is a decoder; When a high-level signal is input, the recording medium is non-erasable, and when a low-level signal is input, the recording medium is erased. By recording, by inputting a low-level signal, by reproducing, it is processed as a signal. 26 is a Faraday rotator 21 according to the signal from the decoder 25.
A control circuit 27 is a waveform control circuit which modulates the current flowing to the light source 13 when the output from the Nantes gate 23 is at a high level (recording).
If the level is low (reproduction), the current flowing to the light source 13 is kept constant.

The embodiments shown in FIGS. 1 to 3 are for recording and reproducing whether the optical recording medium 2 is an optical disk or a magneto-optical disk. Before explaining its operation, the recording and reproducing principle of optical disks and magneto-optical disks will be explained with reference to FIG. 2a is an optical disk, 2b is a magneto-optical disk, 28 is an optical disk 2
The bit formed on the a-plane, ±08, is the Kerr rotation angle.

(a) Recording on the optical disc 2a shown in the figure is performed by melting a thin metal film or the like on the surface of the optical disc 2a by photothermal energy from a light source 13 to form bits 28 or convex portions. Such optical discs 2a are resistant to slight changes over time and can withstand long-term storage, but on the other hand, they have the disadvantage that they cannot be erased. Moreover, the principle of reproduction from this optical disc 2a is that the optical disc 2a (r)
This is done by utilizing the interference of the reflected light from the surface around the bit 28 and the bit 28. Even if the polarized light transmission axis of the polarizing plate 17 is set to the position shown by the dotted line in Figure b1, there is a component of this reflected light that passes through the polarizing plate 17, although there is a disadvantage that the amount of light passing through the polarizing plate 17 is reduced. If the wavelength of the reflected light is λ, then when the depth of the bit 28 is λ/4, the interference phenomenon between the two emitted lights is strongest, and the contrast of the reproduced signal is improved.

GdTbFe, GdC0-GdDyCOOMnl3
For recording on the magneto-optical disk 2b such as i, a unidirectional magnetic field is applied from the outside to the magneto-optical disk 2b in advance to align the magnetization direction, as shown in the tC1 diagram, and photothermal energy (however, when recording on the optical disk 2a, This is done by locally causing magnetization reversal by applying photothermal energy (which allows recording with photothermal energy weaker than photothermal energy) and changing the direction of magnetization (upward and downward directions as shown in figure (C)). Furthermore, when a light flux with a uniform polarization plane is applied to the magneto-optical disk 2b recorded in this manner, a 1-degree reflected light is obtained with the polarization plane around due to the magneto-optical effect. This phenomenon is the well-known Kerr effect,
Further, the rotation angle of the polarization plane of light is called the Kerr rotation angle θ. The rotation angle of the plane of polarization is reversed depending on the direction of magnetization,
From the plane of polarization at the time of incidence, the Kerr rotation angle is −θ, and the Kerr rotation angle is 〇.

For example, if the polarized light transmission axis of the polarizing plate 17 is set to the position indicated by the dotted line in the figure fd), the components of the light flux passing through the polarizing plate 17 will be The light flux is different, and the difference becomes a change in the light amount, which can be read out by the four-split photodetector 19 as a reproduction signal.

In this way, when recording and reproducing on two types of optical recording media 2 (optical disk and magneto-optical disk), photothermal energy records information on each optical recording medium 2 or
It can be seen that this can be done by increasing or decreasing the irradiation energy intensity so that the energy can reproduce information from the source.

These two typical types of optical recording media 2 usually have different reflectances. Therefore, by measuring the difference in the reflectance of each type, the type can be determined, and the irradiation energy intensity can be controlled so that the amount of light is suitable for each type. Even if they have the same reflectance, if the optical recording medium 20 substrate is transparent, by coating the surface of the optical recording medium 2 with a dielectric film, etc., it is possible to directly distinguish the optical recording medium 20 from the difference in reflectance. If the optical recording medium 20 substrate is opaque, it can be identified by pasting labels or the like with different reflectances depending on the type on the back side of the optical recording medium 20 substrate (the side opposite to the medium surface).

Next, the operation will be explained. Open the cover 1, set the optical recording medium 2, and close it. Next, manually select recording or playback using the operation button 11. Thereby, light is projected from the light projector 3 onto the optical recording medium 2 by a circuit not shown, and the reflected light is received by the light receiver 4. The output from the photoreceiver 4 is input to a comparator 24 and compared with a reference voltage of the comparator 24. For example, when the light receiver 4 receives reflected light from the non-erasable optical recording medium 2, the output from the comparator 24 becomes high level.
input to the decoder 25. Further, when recording is selected by the operation button 11, the switch 22 is turned on in conjunction with the operation button 11.
A high level signal from the Nant gate 23 is sent to the decoder 25
Output to. As a result, in the decoder 25, since the comparator 24 also receives a high level signal, it is treated as a non-erasable recording medium, and the Nant gate 22 also receives a high level signal, so it is processed as an rC record and sent to the control circuit 25.
Operate 6.

Note that the output from the decoder 25 is as follows: (1) Recording - non-erasable recording medium (II) Recording - erasable recording medium (III) Playback - non-erasable recording medium
Although there may be four sides of the reproducible and erasable recording medium, the control circuit 26 changes the magnitude of the magnetic field applied to the Faraday Rocheetah 21 depending on the side (I) to rotate the polarization plane of the light beam. In addition, in the waveform control circuit 27, the Nant gate 23 also modulates the light emission of the light source 13 when a high level (recording) signal is input, and causes the light source 13 to emit light continuously when a low level (reproduction) signal is input. . The rotation angles of the Faraday Rocheetah 21 in these four cases are preset by the control circuit 26 to predetermined angles at which the amount of light passing through the polarizing plate 2o becomes an optimum value. The Faraday Rocheetah 21 uses a special glass doped with yttrium iron garnet (YIG) and rare earth elements.The axis of easy magnetization is placed parallel to the optical axis, and the plane of polarization of the light is changed by applying a magnetic field. can be rotated (Faraday effect). Polarizing plate 20
When the angle formed between the transmission axis of and the polarization plane of light is θ, the intensity of transmitted light is proportional to cos20. Furthermore, the rotation angle of the plane of polarization of light due to the 7 Allardy effect is proportional to the strength of the magnetic field.

Therefore, the intensity of the irradiation energy is controlled by the Faraday Rocheetah 21 and the polarizing plate 2o.
The optimum amount of light is provided according to the moisture level.

A beam from a light source 13 such as a semiconductor laser is given a desired luminous flux distribution by a collimation lens 14, the irradiation energy is controlled by a Faraday Rocheetah 21 and a polarizing plate 20, passes through a beam brick 15, and is reflected by a total reflection mirror 16. After being deflected, the light is turned into a minute spot by the lens 7 and focused onto the optical recording medium 2 .

The reflected light from the optical recording medium 2 passes through the lens 7 and the total reflection mirror 16 again, and is split by the beam splitter 15. After passing through a polarizing plate 17, the divided light flux passes through an astigmatism optical system 18 and enters a four-split photodetector 19. The combination of the astigmatism optical system 18 and the 4-split photodetector 19 provides an error signal for automatic focus control of the actuator 12.
1tC is used, and its principle is already known.

It is also a known technique that with this combination, it is possible to detect tracking errors using the diffraction phenomenon of the track grooves of the optical recording medium 2. Although several systems have already been proposed for the actuator 12, one that utilizes a voice coil mechanism is generally used.

According to this embodiment, light is projected from the light projector 3 onto the optical recording medium 2, and the reflected light is received by the light receiver 4, and the decoder 25 receives the reflected light.
Since it is possible to distinguish between 20 types of optical recording media and automatically set the optimum light amount using the Faraday Rocheetah 21 and the polarizing plate 20, information can be recorded and reproduced on any of the optical recording media 2 with different characteristics. be able to.

In this embodiment, the light projector 3 corresponds to the light projecting means of the present invention, the comparator 24 and the decoder 25 correspond to the discriminating means, the Faraday Rocheater 21 corresponds to the polarization plane rotating element, and the control circuit 26 corresponds to the polarization plane rotating element. Corresponds to control means.

As explained above, according to the present invention, the light projecting means for projecting light onto the surface of an optical recording medium and the level of the light reflected from the optical recording medium by the light projecting means are detected, and the recording sensitivity is adjusted based on the detection level. a discriminating means for discriminating between different optical recording media; a polarization plane rotation element disposed in the optical path from the light source to the optical recording medium; and a polarizing plate disposed on the optical path on the output side of the polarization plane rotation element; and a polarization plane control means for controlling the rotation angle of the polarization plane of the polarization plane rotation element in accordance with the discrimination by the discrimination means, so that the sight passing through the polarizing plate is adjusted to the optimum for optical recording media having different recording sensitivities. Since this value is set to the same value, information can be recorded and reproduced on any optical recording medium with different characteristics.

[Brief explanation of the drawing]

FIG. 1 is an overall schematic diagram showing an information recording/reproducing apparatus according to an embodiment of the present invention, FIG. 2 is a layout diagram of an optical system in the head section in FIG. 1, and FIG. Block diagram showing the signal processing system, Figure 4 + al (b) ((
J (dl is a diagram showing recording and reproducing of the information recording and reproducing device. 2... Optical recording medium, 3... Emitter, 4... Light receiver, 6... Head section, 7... Lens , 11... Sweeping button, 13... Light source, 20... Polarizing plate, 21...
・Faraday Low 7--1, 22...Swiss f, 2
4...conno<lator, 25...decoder, 26.
...Control circuit, 27.--Waveform control circuit. Patent Applicant Canon Co., Ltd. Representative Minoru Nakamura Figure 1 Figure 2 Figure 3 Figure 4 (b) (d)

Claims (1)

[Claims] (2) In an information recording and reproducing apparatus equipped with a light source for recording and reproducing that generates a polarized beam to an optical recording medium, a light projecting means for projecting light onto the surface of the optical recording medium, and an optical recording medium by the light projecting means a discrimination means for detecting the level of reflected light from the light source and discriminating optical recording media having different recording sensitivities depending on the detection level; a polarization plane rotating element disposed in an optical path from the light source to the optical recording medium; A polarizing plate disposed on the optical path of the output fijll of the rotation element, and a polarization plane control means for controlling the rotation angle of the polarization plane of the polarization plane rotation element according to the determination by the determination means. Information recording and reproducing device.