JPH04324143A - Evaluation device of optical magnetic recording medium - Google Patents

Abstract

PURPOSE:To make the only temperature of the optical magnetic recording medium rise so that its upper and lower surfaces may be made uniform without making the temperature of the optical pickup rise. CONSTITUTION:A first and a second fun heaters 10, 12 are installed to the upper and lower part of a housing 1 to make the temperature of an optical magnetic disk 2 provided within the housing 1 rise. These first and second fun heaters 10, 12 are electrically connected with a controller 18 via power sources for the first and second heaters 14, 16. A first and a second temperature transducers 6, 8 to detect the temperatures of the upper and back surfaces of the optical magnetic disk 2 are electrically connected with a controller 18. By this controller 18, the first and second fun heaters 10, 12 and the power sources for the first and second heaters 14, 16 are controlled.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magneto-optical recording medium evaluation apparatus for evaluating the characteristics of a magneto-optical recording medium.

0002

[Prior Art and its Problems] Generally, in an evaluation device for a magneto-optical recording medium, such as a magneto-optical disk, the temperature of the magneto-optical disk is increased, and the change in birefringence caused by the temperature increase of the substrate of the disk is mainly observed. Characteristics such as the deterioration of the CN ratio of the reproduced signal, which is the cause of this, are evaluated. When evaluating such characteristics, if a temperature difference occurs between the upper and lower surfaces of the disk when the temperature of the magneto-optical disk is increased, there is a possibility that the disk will warp. In addition, in the case of a magneto-optical disk in which two disks are bonded together so that both sides can be used, if the temperature difference occurs, thermal distortion occurs in the bonded portion, which causes a change in the birefringence of the disk substrate. becomes large and the reproduced signal deteriorates. Therefore,
If the temperature difference mentioned above occurs, the disc may warp or
Since it may become impossible to evaluate pure characteristics due to the temperature rise of the disk, it is extremely important to make the top and bottom surfaces of the disk the same in order to increase the disk temperature uniformly on the top and bottom surfaces. It's coming.

On the other hand, as a conventional magneto-optical disk evaluation device, a drive including an optical pickup and the disk are placed in a constant temperature bath, and the constant temperature bath is kept at a high temperature to keep the disk at a high temperature and evaluate its characteristics. It has been known. In this device, the entire drive is heated to a high temperature, which changes the characteristics of the optical pickup, making it impossible to evaluate the pure characteristics of the disk due only to the temperature increase, so the temperature of the optical pickup is raised. It is very important to raise only the temperature of the disk without causing any damage.

Furthermore, in the drive, if the voice coil motor, which is part of the actuator for moving the optical spot of the optical pickup, is located on the lower surface side of the disk, the temperature of the lower surface may be higher than that of the upper surface. Therefore, in this case, in order to raise the temperature of the disk uniformly on the upper and lower surfaces, it is necessary to set the upper and lower surfaces of the disk to arbitrary temperatures.

As a technique for uniformly increasing the temperature of a disk on its upper and lower surfaces, there is known a technique described in a method for forming a disk substrate disclosed in Japanese Patent Publication No. 52704/1983. In this technique, the temperature of the substrate is increased while the substrate is being rotated at high speed. However, since this technique is a method for forming a disk substrate, no consideration is given to the optical pickup that is essential to the evaluation device.

[0006] As an evaluation device that increases only the temperature of the disk without increasing the temperature of the optical pickup, there is known an evaluation device disclosed in Japanese Patent Laid-Open No. 2-304754. In this device, warm air is blown into a housing that covers a magneto-optical disk to raise the temperature of the disk, and its characteristics are evaluated using an optical pickup placed outside the housing.

However, in this device, if the disk is not installed at the center of the housing in the height direction and there is a difference between the space on the top side of the disk and the space on the bottom side, there will be a temperature difference between the top and bottom surfaces. It is difficult to set the hot air blowing position to eliminate this temperature difference. Since the optical pickup is installed outside the housing, it may be difficult to install the disk at the center of the housing in the height direction. Further, even if the temperature difference between the upper and lower surfaces is set so as not to occur at a certain rotation speed of the disk, it may occur at other rotation speeds.

An object of the present invention is to provide an evaluation apparatus for a magneto-optical recording medium that can uniformly increase the temperature of the magneto-optical recording medium without increasing the temperature of the optical pickup.

[0009]

[Means for Solving the Problems] Therefore, in the evaluation device for a magneto-optical recording medium according to the present invention, there is provided a housing that covers the magneto-optical recording medium, an optical pickup installed outside the housing, and a magneto-optical recording medium inside the housing. A heating means for heating the recording medium, a temperature sensor for detecting the temperature of the upper and lower surfaces of the magneto-optical recording medium heated by the heating means, and a temperature sensor for detecting the temperature of the upper surface of the magneto-optical recording medium according to the output of the temperature sensor. It is characterized by comprising a control means for controlling the heating means so that the temperature of the lower surface and the temperature of the lower surface are the same.

[0010] Furthermore, in the evaluation apparatus for a magneto-optical recording medium of another invention, a housing that covers the magneto-optical recording medium, an optical pickup installed outside the housing, and a magneto-optical recording medium inside the housing are heated. In a magneto-optical medium evaluation apparatus comprising a heating means and a temperature sensor for detecting the temperature of the upper and lower surfaces of the magneto-optical recording medium heated by the heating means, the magneto-optical recording medium is heated according to the output of the temperature sensor. It is characterized by comprising a control means for controlling the heating means so that the upper surface and the lower surface of the medium are respectively at desired temperatures.

[0011]

[Operation] In the present invention, the control means controls the heating means to make the temperature of the upper surface of the magneto-optical recording medium equal to the temperature of the lower surface according to the temperatures of the upper and lower surfaces of the magneto-optical recording medium detected by the temperature sensor. control.

In another invention, the control means controls the heating means to bring the upper and lower surfaces of the magneto-optical recording medium to desired temperatures, respectively, in accordance with the temperatures of the upper and lower surfaces of the magneto-optical recording medium detected by the temperature sensor. Control.

[0013]

Embodiment Next, an evaluation apparatus according to a first embodiment of the present invention will be described with reference to FIGS. 1 to 3.

In FIG. 1, reference numeral 1 indicates a housing. This housing 1 includes a cover 1a and a cover 1a.
and a bottom wall 1b to which is removably attached. The housing 1 is made of a transparent material such as plastic or glass so that the inside can be seen from the outside. Inside this housing 1, a magneto-optical disk 2 is removably attached to a support portion 3a. This support portion 3a is connected to a shaft 3 inserted into the housing 1 through a first hole 1c formed in the bottom wall 1b.
It is fixed to the tip of b. This shaft 3b is rotated by a spindle motor 3 installed outside the housing 1, specifically below the bottom wall 1b. Thus, the magneto-optical disk 2 is rotated by the spindle motor 3.

In the figure, on the right side of the spindle motor 3 is an optical pickup 4 that irradiates a light spot onto the lower surface of the magneto-optical disk 2 through a second hole 1d formed in the bottom wall 1b.
is installed. This optical pickup 4 is installed so as to be movable in the radial direction of the magneto-optical disk 2 and in a direction orthogonal to this radial direction. A bias magnet 5 is mounted inside the housing 1, facing the optical pickup 4 with the magneto-optical disk 2 in between, and moving together with the optical pickup 4.

On the other hand, in the figure, on the left side of the support part 3a of the spindle motor 3, there are a first temperature transducer 6 for detecting the temperature of the upper surface of the magneto-optical disk 2, and a second temperature transducer for detecting the temperature of the lower surface. 8 is fixed to the inside of the housing 1. Above the first temperature transducer 6 is a first temperature transducer for blowing hot air into the housing 1.
A fan heater 10 is fixed to the upper wall of the cover 1a of the housing 1. Below the second temperature transducer 8 is a second fan heater 10 with a similar function to the first fan heater 10.
A fan heater 12 is fixed to the bottom wall 1b of the housing 1. These first and second fan heaters 10,
12 is installed at a position such that the first and second temperature transducers 6, 8 are not directly affected by these hot air.

[0017] The first fan heater 10 has a heating wire 10a.
and a fan 10b. The heating wire 10a is connected to a variable current type first heater power source 14 that supplies current to the heating wire 10a. This first heater power supply 14
is electrically connected to the controller 18. This controller 18 is electrically connected to the first temperature transducer 6, and transmits information via the first heater power source 14 according to the temperature of the upper surface of the magneto-optical disk 2 detected by the first temperature transducer 6. to control the current supplied to the heating wire 10a of the first fan heater 10. Hereinafter, the first temperature transducer 6, the first fan heater 10, and the first heater power source 14 will be collectively referred to as a first sensor system.

The second fan heater 12 composed of the heating wire 12a and the fan 12b is also similar to the first fan heater 1.
0 is connected to the controller 18 in a similar manner. That is, the heating wire 12a is connected to a second heater power source 16 that performs the same function as the first fan heater 14. This second heater power source 16 is connected to the controller 1
8. This controller 18 is electrically connected to the second temperature transducer 8, and according to the temperature of the lower surface of the magneto-optical disk 2 detected by the second temperature transducer 8, the controller 18 generates a signal via the second heater power source 16. to control the current supplied to the heating wire 12a of the second fan heater 12. Hereinafter, the second temperature transducer 8, second fan heater 12, and second heater power source 16 will be collectively referred to as a second sensor system. In addition,
The controller 18 is configured to control the first sensor system and the second sensor system in the same manner and independently. This control method will be explained in detail later. The operation of the magneto-optical recording medium evaluation apparatus of the first embodiment configured in this manner will be described below.

First, current is supplied from the heater power supplies 14 and 16 to the heating wires 10a and 12a. This current generates heat in the heating wires 10a and 12a, and this heat is transferred to the fans 10b and 12a.
12b blows hot air into the housing 1. Then, the temperature inside the housing 1 becomes higher than the temperature outside the housing 1. The temperatures of the upper and lower surfaces of the magneto-optical disk 2 are detected by first and second temperature transducers 6 and 8 and sent to the controller 18. The controller 18 detects the temperatures of the upper and lower surfaces of the magneto-optical disk 2, and turns on the first and second heaters via the first and second heater power supplies 14, 16 so that the temperatures reach the desired temperatures. Controls fan heaters 10 and 12. Then, the characteristics of the magneto-optical disk 2 at a desired temperature are evaluated using the optical pickup 4 and the bias magnet 5. This evaluation uses a known technique, so the explanation will be omitted.

The controller 18 is configured to independently control the first sensor system and the second sensor system using the same method, so that the temperatures of the upper and lower surfaces of the magneto-optical disk 2 are kept the same. You can also make them different. If the target temperatures are the same, the target temperatures for the top and bottom surfaces of the magneto-optical disk 2 should be the same, and if they are set to arbitrary temperatures,
It is only necessary to make these target temperatures different. The control method for the first sensor system will be explained in detail below using FIGS. 2 and 3.

In FIG. 2, the initial current supplied to the heating wire 10a is I0, and when this current I0 is passed, the first
Let T0 be the temperature of the upper surface of the magneto-optical disk 2 detected by the temperature transducer 6 (ST1). As the current I0 continues to flow, the temperature of the upper surface of the magneto-optical disk 2 increases and reaches T' after Δt seconds. Here, Δ
The difference between the temperature T' after t seconds and the initial temperature T0 (=T) is Δ
T1, and the difference between T' and the target temperature Tf is set as ΔT2 (ST2). Letting ΔI be the current to be added to the target temperature Tf, ΔI is a function of ΔT1 and ΔT2 (ST3
). A determination table for ΔI according to the two temperature differences, ie, ΔT1 and ΔT2, is prepared in advance, and ΔI is determined using this determination table. An example of this decision table is shown in FIG. After determining ΔI, ΔI is added to the initial current I0 (=I) and is caused to flow (ST4). By repeating this operation, the amount of current to be passed to reach the target temperature Tf is determined.

In order to make the temperature of the upper surface and the lower surface of the magneto-optical disk 2 the same, the target temperature of the first sensor system and the target temperature of the second sensor system are made the same, and the temperature of the upper surface and the lower surface can be set arbitrarily. In this case, the target temperatures may be different. If such a control method is used, even after the temperature has converged to the target value, if the temperature deviates due to some disturbance, it will automatically reconverge.

By configuring the evaluation apparatus as described above, it is possible to accurately evaluate changes in characteristics of a magneto-optical disk due to temperature changes. Furthermore, since the position at which hot air is blown into the housing can be easily set, it is possible to reduce the temperature difference even if the rotation speed of the disk changes.

Next, a modification of the first embodiment will be explained using FIG. 4. This modification clarifies the means for moving the optical pickup 4 and bias magnet 5 in the first embodiment. The optical pickup 4 is mounted on the first base 20
is fixed to. This first base 20 is attached to a Z-axis table 22 that is movable in a direction perpendicular to the radial direction of the magneto-optical disk 2 . An X-axis table 24 that is movable in the radial direction of the magneto-optical disk 2 is attached to the Z-axis table 22 . This X-axis table 24 is
It is provided on a second base 26, and this second base 2
6, a spindle motor 3 is fixedly attached.

A support portion 28 extending into the housing 1 through a third hole 1e formed in the cover 1a is attached to the first base 20. This support part 28
A bias magnet 5 is attached to the tip of the optical pickup 4 so as to face the optical pickup 4 . This optical pickup 4
An objective lens 4a is provided inside the tip portion of the lens, and an erecting mirror 4b is provided at the base portion thereof.

[0026] first and second temperature transducers 6;
8 is connected to the controller 18 via a digital voltmeter 30. This digital voltmeter 30
The temperature transducer is of a type having two or more input channels so that the voltages of the first and second temperature transducers 6 and 8 can be detected. The digital voltmeter 30 and the first and second heater power supplies 14 and 16 are connected to the controller 1 via a computer interface such as GP-IB, SCSI, or RS232C.
8 respectively. The other configurations are the same as in the first embodiment.

With the above configuration, the objective lens 4
Since there is a large distance between the mirror 4b and the mirror 4b, the optical components inside the optical pickup 4 other than the objective lens 4a can be kept at room temperature.

Next, a second embodiment of the magneto-optical recording medium evaluation apparatus according to the present invention will be described with reference to FIGS. 5 to 7. Note that the same members as in the first embodiment are indicated by the same reference numerals, and only the different parts will be explained.

The evaluation device of the second embodiment uses a fan heater (
The hot air from the fan heater 11 is divided into two by a solenoid valve 32, and the nozzle 3 is installed on the upper surface side and the lower surface side of the magneto-optical disk 2.
4 and 36 into the housing 1. The fan heater 11 has a heating wire 11a and a fan 11b. The solenoid valve 32 is connected to the controller 1
8, and the controller 18 adjusts the ratio of hot air blown into the upper surface side and the lower surface side. The control method will be explained below.

First, the electrothermal valve 32 is placed in the center so that the amount of hot air blown into the upper surface and the lower surface of the magneto-optical disk 2 is equal. In FIG. 6, the average value of the target temperature of the upper surface and the lower surface of the magneto-optical disk is Tf, and the difference between these target temperatures is TD. As in the first embodiment, the initial current supplied to the heating wire 11a is I0, the total amount of air blown into the housing 1 is W, and the amount of air blown from the top side of the magneto-optical disk 2 is WA. In W and WA,
Establish the following relational expression (ST1). That is, WA = kW (0≦k≦1) Needless to say, the air volume WB blown from the bottom side of the magneto-optical disk 2 is the amount obtained by subtracting WA from the entire air volume W.

The temperature of the upper surface of the magneto-optical disk 2 detected by the first temperature transducer 6 when the initial current I0 is applied is TA, and the temperature of the lower surface of the magneto-optical disk 2 detected by the second temperature transducer 8 is TA. Let be TB. As the current I0 continues to flow, the temperature of the magneto-optical disk 2 increases, and after Δt seconds, the temperature of the upper surface becomes T'A and the temperature of the lower surface becomes T'B. and,
The temperature change on the top surface for Δt seconds is ΔT1 (=T′A
-TA ), the difference between the temperature after Δt seconds on the top surface and the average value of the target temperature is ΔT2 (=Tf -T′A ), T′A
The relationship between T'B and the desired temperature difference TD is expressed as Δ
T3 (=T'A - T'B +TD) (ST
2). ΔI is a function of ΔT1 and ΔT2, and the first
As in the embodiment, a determination table for ΔI is created, and ΔI is determined according to this table (ST3). On the other hand, k is ΔT3
Similarly to the case of ΔI, a decision table is created in advance and decisions are made according to this (ST3
). Then, the current supplied to the heating wire 11a and the air volume on the upper surface side and the lower surface side are determined (ST4). According to this embodiment, since one heater and one power supply can be provided, the apparatus can be constructed at a lower cost than in the first embodiment.

In the above two embodiments and modifications, a temperature transducer is used to detect the temperature of the magneto-optical disk, but a thermocouple or a radiation thermometer may be used instead. The present invention is not limited to the above embodiments,
Numerous embodiments and variations are possible.

[0033]

According to the evaluation apparatus for a magneto-optical recording medium according to the present invention, only the temperature of the magneto-optical recording medium can be uniformly increased without increasing the temperature of the optical pickup.

[Brief explanation of drawings]

FIG. 1 is a sectional view showing an evaluation device according to a first embodiment of the present invention.

FIG. 2 is a flowchart illustrating control by the controller in FIG. 1;

FIG. 3 is a decision table for determining ΔI in FIG. 2;

FIG. 4 is a sectional view showing a modification of the evaluation device of the first embodiment.

FIG. 5 is a sectional view showing the evaluation device of the second embodiment.

FIG. 6 is a flowchart illustrating control by a controller in the evaluation device of the second embodiment.

FIG. 7 is a decision table for determining k in FIG. 6;

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1... Housing, 2... Magneto-optical disk, 4... Optical pickup, 6... First temperature transducer, 8... Second temperature transducer, 10... First fan heater, 12
...Second fan heater, 14...First heater power supply, 1
6...Second heater power supply, 18...Controller.

Claims (2)

[Claims] [Claim 1] A housing that covers a magneto-optical recording medium;
An optical pickup installed outside this housing,
a heating means for heating the magneto-optical recording medium in the housing; a temperature sensor for detecting the temperature of the upper and lower surfaces of the magneto-optical recording medium heated by the heating means; An evaluation apparatus for a magneto-optical recording medium, comprising a control means for controlling the heating means so that the temperature of the upper surface and the temperature of the lower surface of the recording medium are made the same. [Claim 2] A housing that covers a magneto-optical recording medium;
An optical pickup installed outside this housing,
In the magneto-optical medium evaluation apparatus, the magneto-optical medium evaluation apparatus includes a heating means for heating the magneto-optical recording medium in the housing, and a temperature sensor for detecting the temperature of the upper and lower surfaces of the magneto-optical recording medium heated by the heating means. An evaluation apparatus for a magneto-optical recording medium, comprising a control means for controlling the heating means so that an upper surface and a lower surface of the magneto-optical recording medium are brought to desired temperatures, respectively, in accordance with the output of a temperature sensor.