JPH01191330A - Optical information processor - Google Patents

Abstract

PURPOSE:To always attain recording, reproducing and erasing in an optimum condition by detecting the temperature or temperature change of a recording medium and controlling the relative moving speed of an optical beam projected to the recording medium to the recording medium in correspondence to a detected result. CONSTITUTION:When information are recorded, a laser beam to be emitted from a semiconductor laser 6 is projected while a bias magnetic field is impressed from a bias magnet 21 to a revolving magneto-optical disk 11. At such a time, the semiconductor laser 6 is driven according to the recording information and the laser beam to receive intensity modulation is emitted. The revolving speed of the medium at such a time is controlled by a CPU24 so as to give optimum recording energy to the medium in the medium temperature to be detected by a temperature sensor 23. Thus, even when the temperature of the medium is widely changed, the information can be recorded, reproduced or erased always with optimum light intensity.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field] The present invention relates to an optical information processing device that records, reproduces, or erases information by irradiating a recording medium with a light beam.

[Prior art]

In recent years, there has been active development of optical information processing devices that record or reproduce information at high density by irradiating an optical recording medium with a light beam. As such an optical recording medium, there is a write-once (write-once,
(hereinafter referred to as WO) type recording media and erasable type recording media using magneto-optical or phase change technology are known. Recording and reproduction of information will be described below using a magneto-optical disk as an example.

A magneto-optical disk is formed by forming a magnetic thin film having an axis of easy magnetization perpendicular to the film surface on a substrate, and records information by changing the magnetization direction of this magnetic thin film. During recording, the magnetization direction of the magnetic thin film is first aligned in one direction, and a laser beam digitally modulated in accordance with an information signal is irradiated while applying a bias magnetic field in the opposite direction to the magnetization direction. Then, the temperature of the area irradiated by the laser beam rises to near the Curie point, the coercive force decreases, and the area is magnetized in the opposite direction to the surrounding area due to the influence of the bias magnetic field, forming a magnetization pattern according to the information.

Information recorded in this manner can be optically read out using the well-known magneto-optic effect by irradiating the medium with a low-power unmodulated beam. Furthermore, recorded information can also be erased by applying a magnetic field in the opposite direction to the bias magnetic field during recording.

The optimal laser power for recording, reproducing, and erasing is different, and is set to, for example, 6 mW for erasing power, 4 mW for recording power, and 1 mW for reproducing power.

However, since such information is recorded by heating the recording medium by irradiating it with a laser beam, the recording state may change depending on the temperature of the medium. That is, even if the recording power is set to the optimum value at a certain temperature, if the temperature of the medium changes, the recording power will become too low or too high. If the recording power is too low, the size of the recorded pits will become small and the C/N will decrease.
The ratio goes down. Furthermore, if the recording power is too high, the pits will become too large, and the C/N ratio will decrease. If the C/N ratio decreases, the quality of the reproduced image will decrease in analog recording, for example, when recording images, and in the case of digital recording, the error rate will increase and the reliability of the information will decrease. .

Furthermore, when regenerating or erasing information, a similar problem occurs when the optimum power changes due to temperature changes. For example, if the reproducing power is too low, the C/N ratio will decrease, and if the reproducing power is too high, recorded information may be lost. Furthermore, if the erasing power is too low, there is a risk of leaving unerased data, and if the erasing power is too high, there is a possibility that the medium itself may be destroyed. Furthermore, such problems are not limited to optical energy recording media, but also exist in other erasable type or WO type recording media.

On the other hand, an optical information processing device that prevents the above-mentioned reduction in the C/N ratio is disclosed in Japanese Patent Laid-Open No. 140647/1983. This device detects the environmental temperature of the recording medium and changes the output of a light source that emits a light beam according to the detection result, thereby always obtaining the optimum recording power.

However, in the above-mentioned apparatus, the range of change in the output of the light source is small, and it may not be possible to adequately cope with large temperature changes. In particular, when using a semiconductor laser as a light source, there were problems such as increasing the output too much would shorten the life of the laser, and decreasing the output too much would make the laser oscillation unstable, making it difficult to vary the output over a wide range. .

(Summary of the Invention) An object of the present invention is to solve the problems of the prior art described above, to be able to record, reproduce, or erase information at the optimum light intensity even when the temperature of the medium changes significantly, and to achieve a high C. An object of the present invention is to provide an optical information embedding device that can obtain a /N ratio.

The above object of the present invention is to detect the temperature or temperature change of a recording medium in an optical information processing apparatus that records, reproduces or erases information by irradiating a recording medium with a light beam that moves relative to the medium. This is achieved by providing means for detecting and means for controlling the relative moving speed of the light beam with respect to the recording medium according to the detection result.

That is, the apparatus of the present invention changes the relative speed of the light beam to the recording medium depending on the temperature of the recording medium. The energy given to the medium by irradiation with a light beam is determined by the laser power and the irradiation time. The present invention changes the irradiation time by controlling the speed of the light beam, thereby compensating for changes in the optimum laser power due to changes in the temperature of the medium.

〔Example〕

Embodiments of the present invention will be described in detail below with reference to the drawings.

FIG. 1 is a schematic sectional view showing an embodiment of the optical information processing device of the present invention. In this embodiment, a case is shown in which a magneto-optical disk is used as the recording medium.

In FIG. 1, a laser beam emitted from a semiconductor laser 6 is collimated by a collimator lens 7, passes through a beam shaping prism 8 and a polarizing beam splitter 9, and is focused as a minute spot on a magneto-optical disk 11 by an objective lens 10. imaged.

The light reflected by the magneto-optical disk 11 passes through the objective lens 10 again, is reflected by the polarizing beam splitter 9, and is separated from the light incident on the medium. This reflected light further passes through a sensor lens 13, is split into two parts by a beam splitter 14, and is focused on a signal sensor 16 and a servo sensor 17, respectively. A polarizing plate 15 is provided in front of the signal sensor 16, and converts changes in the polarization state due to the magneto-optic effect into intensity modulation. The servo sensor 17 detects focusing signals and tracking signals using a well-known method such as an astigmatism method or a push-pull method. These detected servo signals are fed back to the lens actuator 12,
By driving the objective lens 10, autofocusing and autotracking are performed.

The magneto-optical disk 11 is protected by a disk cartridge 2.
It is stored in 2. This disk 11 is then clamped to a turntable 19 by a clamper 20 and rotated by a spindle motor 18. On the side of the magneto-optical disk 11 opposite to the side on which the light beam is irradiated,
A bias magnet 21 is provided to apply a bias magnetic field to the disk 11 during recording and erasing. The temperature sensor 23 is held by the same member (not shown) as the bias magnet 21, and after the disk 11 is clamped, the temperature sensor 23 is held by the same member (not shown) as the bias magnet 21.
, and the position is as shown in the figure. Here, a small hole 26 for measurement is provided in the disk cartridge 22, and the temperature sensor 23 can detect the temperature of the disk 11 through this small hole 26. The temperature detected by the temperature sensor 23 is sent to the central processing unit (Ce
central processing unit, hereafter C
The rotational speed of the spindle motor 18 is changed via the spindle motor drive circuit 27 according to the detection result.

Furthermore, the output from the CPU 24 is sent to the laser drive circuit 2f to control the recording frequency of the semiconductor laser 6. This is to prevent the distance between the pits of bits recorded on the disk from being affected by the rotation speed of the disk by changing the recording frequency by the change in the rotation speed of the disk 11. For example, if the recording frequency when the disk rotation speed is 180 Or, p, m is 4 MHz, when the medium temperature rises and the rotation speed becomes 270 Or, p, m, the recording frequency becomes 6 MHz.
Becomes MH2.

In the apparatus of this embodiment, information is recorded by irradiating the rotating magneto-optical disk 11 with a laser beam emitted from the semiconductor laser 6 while applying a bias magnetic field from the bias magnet 21 . At this time, the semiconductor laser 6 is driven according to the recorded information and emits an intensity-modulated laser beam. Further, the rotational speed of the medium at this time is set at C such that the optimum recording energy is given to the medium at the medium temperature detected by the temperature sensor 23.
It is controlled by the PU24. Therefore, even if the temperature of the recording medium changes due to changes in the room temperature or the temperature within the apparatus, information can always be recorded with a high C/N ratio.

When reproducing the information recorded as described above, the semiconductor laser 6 irradiates the magneto-optical disk 11 with a low-power, unmodulated laser beam, and the signal sensor 16 detects the reflected light. In addition, when erasing recorded information, a bias magnet 2 is attached to the magneto-optical disk 11.
1, by applying a bias magnetic field in the opposite direction to that during recording and irradiating a high-output, unmodulated laser beam.

When reproducing or erasing such information, the aforementioned temperature sensor 23 is used to control the rotation of the disk 11 so that the energy given to the medium by the irradiation of the light beam is the optimum energy according to the medium temperature. The speed may also be controlled.

However, when reproducing information, the output of the temperature sensor 23 is not sent to the laser drive circuit, but is input to a reproducing circuit (not shown) connected to the signal sensor 16, and reproduced according to the rotational speed of the disk. Change the clock frequency.

The rotation speed of the disk is set, for example, as follows. FIGS. 2(a) and 2(b) are diagrams showing the C/N ratio of a reproduced signal when recording is performed on the magneto-optical disk 11 described above while changing the recording power. Figure 2 (
a) and FIG. 2(b) are data near the innermost circumference and the outermost circumference of the disk, respectively. Since bits are recorded more densely on the innermost periphery, C at high recording power
The decrease in ZN ratio is significant. Moreover, each curve shows the medium temperature T
The data with parameters are shown. From this figure, the optimum recording power depending on the medium temperature can be determined. For example, when the medium temperature T is 25 DEG C., as indicated by the solid line, the optimum recording power is 3 to 4 mW.

Such optimum recording power is shown in FIG.

In FIG. 3, the horizontal axis represents the medium temperature, and the vertical axis represents the optimum recording power at that temperature.

On the other hand, FIG. 4 shows the relationship between the number of rotations of the disk and the recording power. FIG. 4 shows the case where the temperature of the disk is constant (25° C.), the horizontal axis shows the rotational speed of the disk, and the vertical axis shows the optimum recording power at that rotational speed. As can be seen from Figures 3 and 4, when the optimum recording power changes depending on the temperature of the disk, the temperature change is compensated for by changing the rotational speed of the disk instead of changing the laser output. I can do it. For example, if the disk temperature is 10℃
If the optimum recording power decreases by 0.5 mW due to the increase in power, the number of rotations of the disk will be increased to 50 Or, p, m while the laser output remains the same.

Just increase it. In the examples shown in Figures 3 and 4, the disk rotates at 180 Or, p, m, and its temperature is 25°C.
If the laser output is set to the optimum recording power of 4 mW in the case of
Good recording can be achieved by changing the value within this range.

As the above-mentioned temperature sensor 23, any sensor may be used as long as it can detect the temperature of the medium.
A pyroelectric infrared sensor that can measure temperature without contacting the medium is particularly suitable. FIGS. 5 and 6 are a schematic sectional view and an equivalent circuit diagram, respectively, showing an example of such a pyroelectric infrared sensor. In these figures, 31 is a silicon window;
2 is a ground electrode, 33 is a film frame, 34 is a polyvinylidene fluoride (PVF) film, 35 is a ring electrode, 36 is a spring, 37 is a reflection plate, 39 is a ceramic ring, 40 is a field effect transistor (FET)
, 41 indicate resistance.

Such a pyroelectric infrared sensor has characteristics as shown in Table 1, for example.

Table 1 When the pyroelectric infrared sensor described above is used, temperature detection is performed, for example, by a control circuit whose basic configuration is shown in FIG. In FIG. 7, 42 is a condensing needle, 43 is a chopper,
44 is an infrared sensor, 45 is an amplifying section, 46 is a synchronous rectifying section, 47 is an adding section, 48 is a synchronous pulse generating section, and 49 is a temperature correcting section. In this embodiment, an electrostrictive element is used for the chopper 43, a thermistor is used for the temperature correction section 49,
A measurement range of 0°C to 60°C was obtained.

FIG. 8 is a schematic cross-sectional view showing another embodiment of the present invention.

In FIG. 8, the same members as in FIG. 1 are designated by the same reference numerals, and detailed explanations will be omitted. This embodiment differs from the embodiment shown in the first figure in that a temperature sensor 28 for detecting the temperature of the cartridge 22 is used instead of the temperature sensor 23.

The recording, reproducing and erasing operations in this embodiment are performed in exactly the same manner as described in the example of FIG. Here, it is preferable that the temperature sensor 28 is configured to contact the cartridge when the recording medium is installed in the apparatus, and to be separated from the cartridge when the recording medium is inserted into and ejected from the apparatus.

In this embodiment, the rotational speed of the disk is controlled according to the temperature of the cartridge. This cartridge and the disc stored in it are always treated as one unit, so
, these are considered to have equal temperatures. or,
Usually, the specific heat of both the cartridge and the disk is 0.25~
It is made of 0.4 cal/gK plastic (
In most cases, both are made of polycarbonate with a specific heat of 0.3 cal/gK), so the temperature changes are almost the same when the environmental temperature rises or falls.

Therefore, by detecting the temperature of the cartridge, it is possible to essentially know the temperature of the recording medium.

The present invention can be applied in various ways in addition to the embodiments described above. For example, any temperature sensing means may be used as long as it can substantially detect the temperature of the medium. Specifically, it is also possible to detect the ambient temperature near the medium using a thermocouple, thermistor, etc., and perform speed control using this as the medium temperature. Alternatively, instead of detecting the temperature of the medium itself, a change in temperature may be detected and the relative speed of the light beam relative to the medium may be increased or decreased by an amount corresponding to the change. Furthermore, the present invention is not limited to magneto-optical discs, but also applies to erasable recording media using phase change and W.
Application is also possible when using an O-type recording medium. The shape of the recording medium may be any shape such as a card shape or a tape shape. The present invention can be applied not only to a device in which recording, reproduction, and erasing are performed in the same device as in the embodiment, but also to a recording-only device and a reproduction-only device.

[Effects of the Invention] As explained above, the present invention provides a conventional optical information recording device that includes means for detecting the temperature or temperature change of a recording medium, and light irradiated onto the recording medium according to the detection result. Since a means for controlling the relative speed of the beam to the medium is provided, recording, playback, and erasing can always be performed in the optimal state even when the temperature of the medium changes, and this prevents loss of recorded information and destruction of the medium. This has the effect of eliminating fear and improving the reproduction C/N ratio.

[Brief explanation of the drawing]

FIG. 1 is a schematic sectional view showing one embodiment of the optical information processing device of the present invention, and FIGS. 2(a) and 2(b) show the relationship between recording power and reproduction C/N ratio, respectively. 3 is a diagram showing the relationship between medium temperature and optimal recording power, FIG. 4 is a diagram showing the relationship between disk rotation speed and optimal recording power, and FIG. 5 is a diagram showing the relationship between disk rotation speed and optimal recording power. 6 is an equivalent circuit diagram of the sensor shown in FIG. 5, and FIG. 7 is a block diagram showing the basic configuration of a temperature detection control circuit using the sensor shown in FIG. 5. , FIG. 8 is a schematic sectional view showing another embodiment of the present invention.

Claims (1)

[Claims] (1) In an optical information processing device that records, reproduces, or erases information by irradiating a recording medium with a light beam that moves relative to the medium, means for detecting the temperature or temperature change of the recording medium; , and means for controlling the relative moving speed of the light beam with respect to the recording medium according to the detection result.