JPH05298732A - Optical pickup - Google Patents

Abstract

PURPOSE:To increase a cooling effect by providing an objective lens, driving coil and optical element in a sealed case and by sealing a gas having a specific thermal conductivity at ordinary temperature and normal pressure as lower limit in the sealed case. CONSTITUTION:An objective lens 1, elastic body 4, and cover glass 8 arranged in a carriage 3 are arranged in a case 9 completely sealed by the carriage 3. A gas such as hydrogen gas (1815X10<-4>Wm<-1>K<-1>) or helium gas (1499X10<-4>Wm<-1>K<-1>) being higher in thermal conductivity than the air (265X10<-4>Wm-1K<-1>) and having a thermal conductivity of 260X10<-4>Wm<-1>K-1 as lower limit is sealed in this case 9. The thermal conductivity of the gas sealed in the case 9 is as high as about 7 times that of air in the case of hydrogen gas and 6 time that of air in the case of helium gas. Therefore, the heat of a driving coil 5 is quickly transmitted to the gas within the case 9 and the heat of the gas is transmitted to the case 9. Because the case 9 has a surface area much larger than that of the driving coil 5, it can quickly dissipate the heat to the outside.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical pickup used in optical video discs, compact discs, magneto-optical discs, etc., with improved heat dissipation characteristics.

[0002]

2. Description of the Related Art In recent years, an optical recording / reproducing apparatus has been widely used for consumer use for reproducing video discs and compact discs, and for commercial use, it has become widespread for recording / reproducing large-capacity data.

A conventional optical pickup will be described below with reference to the drawings. FIG. 3 shows the configuration of a conventional optical pickup. As shown in the figure, the objective lens 41 is supported by an elastic body 44 mounted on a carriage 43 that is movable in the tracking direction of the disk 42. A drive coil 45 is attached to the objective lens 41. When the drive coil 45 is energized, a Lorentz force is generated in the magnetic field generated by the magnet 46 arranged on the carriage 43 to drive the objective lens 41. Carriage 4
A reflection mirror 47 is arranged in the inside of the unit 3. The objective lens 41, the elastic body 44, the cover glass 48 disposed on the carriage 43, and the carriage 43 form a sealed case structure, and the inside 49 is sealed so that dust does not enter.

The fixed optical unit 50 contains a laser, a sensor, an optical element, etc., and is sealed by a cover glass 51 so as to prevent dust from entering the inside. Carriage 43
The fixed optical unit 50 is supported by the base 52.
The laser light 53 emitted from the fixed optical unit 50 passes through the cover glasses 51 and 48 and the reflection mirror 47 and the objective lens 4
After passing 1, the light is focused on the disk 42. Disc 42
The more reflected laser light returns through the same optical path, is converted into an electric signal by the fixed optical unit 50, and is output as a position error signal and an output signal.

The position of the objective lens 41 must be controlled so that the laser beam 53 is always focused on the signal track on the disk 42. Therefore, the current flowing through the drive coil 45 is controlled based on the position error signal output from the fixed optical unit 50.

[0006]

In recent years, there is a great demand for high-speed recording / reproduction and access in the optical disk device.
Higher speed of optical pickup is required. In order to control the position of the optical pickup at high speed, it is necessary to increase the driving force. In order to increase the driving force, it is necessary to flow a larger current through the driving coil. However, the heat generated in the drive coil increases in proportion to the square of the flowing current. Therefore, when the driving force increases, the temperature of the optical pickup rises, and the optical performance deteriorates due to thermal deformation of the drive coil and expansion deformation of the constituent members.

Generally, in order to suppress the temperature rise, it is effective to perform forced air cooling with a fan. However, forced air cooling causes dust in the air to adhere to the optical components of the optical pickup, deteriorating the optical performance. In the conventional optical pickup, a dust filter is installed and forced air cooling is performed. However, even if a filter is used, dust in the air cannot be completely removed, which is not sufficient as a dustproof measure. Therefore, forced air cooling is abolished, and a dustproof cover is used as shown in FIG. 3 to prevent dust from adhering to the optical element. If sealed in this way, the temperature rise due to heat generation of the drive coil cannot be sufficiently suppressed, and it is difficult to increase the driving force and speed up the optical pickup.

The present invention solves such a problem, and provides an optical pickup which improves the cooling capacity of a hermetically-sealed pickup so that the driving coil does not burn even when the driving force is increased and high-speed access is possible. The purpose is to do.

[0009]

In order to solve this problem, the present invention has a movable optical element part as a sealed structure to prevent dust from entering and to enclose a gas having a high thermal conductivity in which a drive coil is arranged. It is installed to enhance the cooling capacity and drive power.

[0010]

By sealing the drive coil and the optical element with a gas having a high thermal conductivity, it is possible to speed up the optical pickup while taking measures against dust.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An optical pickup according to an embodiment of the present invention will be described below with reference to the drawings.

(Embodiment 1) FIG. 1 shows the configuration of an optical pickup according to a first embodiment of the present invention. As shown in the figure, the objective lens 1 is supported by an elastic body 4 mounted on a carriage 3 which is movable in the tracking direction of the optical disc 2. At least a part of the carriage 3 is made of a metal having a high thermal conductivity such as aluminum. A drive coil 5 is attached to the objective lens 1. When the drive coil 5 is energized, the magnet 6 disposed on the carriage 3
The Lorentz force is generated in the magnetic field generated by, and the objective lens 1 is driven. A reflection mirror 7 is arranged in the carriage 3.

The objective lens 1, the elastic body 4, and the cover glass 8 arranged on the carriage 3 and the carriage 3 constitute a case which is completely sealed so that dust cannot enter the inside 9 of the case.

Inside the case 9, hydrogen gas (1815
× 10^-FourWm^-1K^-1) Or helium gas (1499
× 10^-FourWm^-1K^-1) Air (265 × 10^-FourWm
^-1K ^-1) Is filled with a gas having a higher thermal conductivity.

Reference numeral 10 designates a fixed optical section containing a laser, a sensor, an optical element, etc., and a cover glass 11 is attached to the laser beam emission port to prevent dust from entering the inside. The carriage 13 and the fixed optical unit 10 are supported by the base 12. The laser light 13 emitted from the fixed optical unit 10 passes through the two cover glasses 11 and 8 and the reflection mirror 7 and the objective lens 1 to be condensed on the disk 2. The laser light 13 reflected by the disc 2 is
The fixed optical unit 10 returns along the same optical path, is converted into an electric signal, and is output as a position error signal and an output signal.

The position of the objective lens 1 must be controlled so that the laser light 13 is always focused on the disk 2.
Therefore, the current flowing through the drive coil 5 is controlled based on the position error signal output from the fixed optical unit 10.

The thermal conductivity of the gas sealed in the sealed case is about 7 times that of air for hydrogen gas and 6 times that of air for helium gas.
Since it is twice as large, the heat of the drive coil is quickly transferred to the gas in the sealed case, and the heat of the gas is transferred to the sealed case. Since the hermetically sealed case has a surface area much larger than that of the drive coil, heat can be quickly diffused to the outside. In this way, the heat of the drive coil is quickly removed, so that the temperature rise of the optical pickup can be suppressed even if a large current is passed through the coil for high speed driving.
Therefore, it is possible to prevent the optical performance from being deteriorated due to the thermal deformation of the drive coil and the expansion deformation of each part, and to increase the access speed of the optical pickup.

Further, since the structure is hermetically sealed, it is possible to prevent dust from entering the inside of the optical pickup and prevent the optical system from becoming dirty and deteriorating the optical performance.

(Embodiment 2) FIG. 2 shows the configuration of an optical pickup according to a second embodiment of the present invention. As shown in the figure, the carriage 2 is movable in the tracking direction of the disk 22.
It is supported by an elastic body 24 attached to the sheet 3. A drive coil 25 is attached to the objective lens 21. When the drive coil 25 is energized, it generates a Lorentz force in the magnetic field generated by the magnet 26 arranged in the carriage 23, and drives the objective lens 21. Carriage 23
A reflection mirror 27 is arranged inside. Fixed optics 2
8 has a laser, a sensor, an optical element, etc. built-in. The carriage 23 and the fixed optical unit 28 are supported by a base 29, and a cover glass 30 is attached to the upper surface of the base 29. The base 29 and the cover glass 30 constitute a case having a hermetically sealed structure.

The laser light 31 emitted from the fixed optical section 28 passes through the reflection mirror 27 and the objective lens 21, passes through the cover glass 30, and is focused on the disk 22. The laser light reflected by the disk 22 returns through the same optical path and is converted into an electric signal by the fixed optical unit 28 to output a position error signal and an output signal.

The position of the objective lens 21 must be controlled so that the laser light 31 is always focused on the disk 22. Therefore, the current flowing through the drive coil 25 is controlled based on the position error signal output from the fixed optical unit 28.

A gas having a high thermal conductivity such as hydrogen or helium is sealed in the sealed case interior 32. The heat conductivity of the enclosed gas is about 7 times that of air for hydrogen gas and 6 times that of air for helium gas, so the heat of the drive coil is quickly transferred to the gas in the sealed case, and the heat of gas is It is transmitted to the sealed case. Since the hermetically sealed case has a surface area much larger than that of the drive coil, heat can be quickly diffused to the outside. In this way, the heat of the drive coil is quickly removed, so that the temperature rise of the optical pickup can be suppressed even if a large current is passed for high speed driving. Therefore, the access speed of the optical pickup can be increased without deteriorating the optical performance due to the thermal deformation of the drive coil and the expansion deformation of each part.

Further, since the sealed structure prevents dust from entering the inside, it is possible to prevent the optical system from being deteriorated due to the dust contaminating the optical system.

[0024]

As is apparent from the above description of the embodiments of the present invention, according to the present invention, the movable part of the optical pickup is housed in the hermetically sealed case, and hydrogen gas or helium gas having a large thermal conductivity is sealed. The heat dissipation characteristics of the drive coil are increased, and the cooling effect is increased. Therefore, a large current can be passed through the drive coil, and the access speed of the optical pickup is increased. Further, since the optical system is hermetically sealed, it is possible to prevent the performance from being deteriorated due to the contamination of the optical system.

[Brief description of drawings]

FIG. 1 is a partially cutaway sectional view showing a configuration of an optical pickup according to a first embodiment of the present invention.

FIG. 2 is a partially cutaway sectional view showing a configuration of an optical pickup according to the second embodiment.

FIG. 3 is a partially cutaway sectional view showing a configuration of a conventional optical pickup.

[Explanation of symbols]

 1 Objective Lens 2 Optical Disc 3 Carriage 4 Elastic Body 5 Drive Coil 7 Reflecting Mirror 8 Cover Glass 9 Inside Sealed Case 13 Laser Light

Claims (1)

[Claims] 1. An objective lens, a drive coil for driving the objective lens, and an optical element for guiding a laser beam to the objective lens are housed in a sealed case, and the sealed case is heated at room temperature and atmospheric pressure. An optical pickup in which a gas having a lower limit of conductivity of 260 × 10 ^-4 Wm ^-1 K ^-1 is enclosed.