JPS623441A - Optical recording and reproducing device - Google Patents

Abstract

PURPOSE:To obtain always the suitable number of the aperture by providing the aperture number variable means to lie between the optical system and the recording media and change the number of the aperture, and the shifting means to shift the aperture number variable means along the light path. CONSTITUTION:When recording is executed by making a fine hole on an optical disk 5 by melting and vaporizing with a laser beam, an energy much larger than the energy of the laser beam at the time of reproduction is necessary, and therefore, the number of the aperture of the optical system is made large, the spot diameter of the laser beam collected on the optical disk 5 is made small and the density of the laser beam is made large. Namely, by shifting an aperture number variable lens 8 in the light path direction of the laser beam with an aperture number variable lens shifting actuator 9 to input an aperture number variable lens 8, an interval l between a movable lens 4 and the aperture number variable lens 8 is made small, the focus distance is made small, the number of the aperture is made large, and thereby, the spot diameter is made small. Thus, the optimum number of the aperture can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention 1] The present invention relates to an optical recording and reproducing apparatus that records and reproduces information by focusing, for example, a laser beam onto an optical disk using an optical system.

[Technical Background of the Invention W4] In recent years, so-called optical recording systems for recording and reproducing information by optical means are being developed for reasons such as high-density recording and high-speed processing.

Generally, the recording format in such an optical recording method is, for example, by focusing a laser beam onto an optical disk using an optical system and melting it onto an optical disk made of a low melting point material.
There are some that cause evaporation and are recorded as minute holes.

The reading mode is similar to that of the holes formed on the optical disk by converging laser light onto the optical disk.
There are devices that detect and read the level displacement of the reflected light caused by the absence of i.

Conventionally, the method of converging laser light onto an optical disk during recording and reading as described above is that the diverging laser light output from a light emitting diode is converted into parallel light through a collimator lens, and then collimated onto a movable mirror. It is incident and reflected in a direction approximately perpendicular to the direction of incidence. The parallel laser beam reflected from the movable mirror is focused on a predetermined point on the optical disk via a movable lens and a fixed lens.

At that time, the focus servo, which accurately focuses the laser beam on the optical disk in response to changes in the focal position due to surface wobbling of the optical disk, controls the focus servo to accurately focus the laser beam on the optical disk in response to changes in the focal point position due to surface wobbling of the optical disk, etc. is input and the actuator moves the movable lens in the direction of the optical path of the laser beam according to the signal, thereby changing the focal position.

[Problems with the Background Art] However, in the above-mentioned focus servo, when changing the focal position, the focal length is always kept constant, that is, the numerical aperture is kept constant, so when the surface runout of the optical disk is very large, Collisions between closely spaced fixed lenses and optical discs have often occurred.

Further, when the acceleration of surface photography of the optical disk is very large, the movement of the movable lens may not be able to follow the movement because the numerical aperture is constant.

Furthermore, when not only playback but also recording is performed using this optical system, in order to make minute holes on the optical disk by melting and evaporation using the laser beam as in the example mentioned above during recording, it is necessary to use the laser during regeneration. Although much larger energy is required compared to the energy of light,
Since the numerical aperture is constant and the spot diameter of the laser beam focused on the optical disk is constant, the optical system can be adjusted by reducing the spot diameter of the laser beam focused on the optical disk. Since it is not possible to increase the density of this laser light,3 and recording is performed by increasing the output of the light emitting diode, a large amount of electric power is required for the recording section.

[Objective of the Invention 1] The present invention has been made in response to the above-mentioned circumstances, and it is possible to change the numerical aperture of an optical system that focuses light onto a recording medium, so that the numerical aperture is always optimal. The purpose of the present invention is to provide an optical recording/reproducing device with the following features.

[Summary of the Invention 1 That is, the optical recording and reproducing apparatus of the present invention is an optical recording and reproducing apparatus that uses an optical system to focus light onto a recording medium to reproduce information, in which the optical system and the recording medium are connected to each other. An optical system that focuses light onto a recording medium by comprising a numerical aperture variable means interposed between the numerical aperture variable means and a moving means that moves the numerical aperture variable means along the optical path of the light. This allows the numerical aperture of the system to be varied, ensuring that the optimum numerical aperture is always achieved.

[Embodiments of the Invention] Hereinafter, details of embodiments of the present invention will be explained based on the drawings.

FIG. 1 is a diagram for explaining one embodiment of the present invention, and FIGS. 2, 3, and 4 show a variable numerical aperture gi21 of this embodiment.
This is a diagram for explaining.

In Figure 1, 1 is a light emitting diode that emits a diverging laser beam, 2 is a collimator lens that converts the diverging laser beam into parallel light, and 3 is a collimator lens that directs the optical path of the parallel laser beam in a direction almost perpendicular to the direction of incidence. a movable mirror that performs tracking servo by reflecting and rotating minutely; a movable lens 4 that is movably supported along the optical path of the sea 1F light and focuses the laser beam at a predetermined position on the optical disk 5; 6 is an actuator that supports the movable lens 4 so as to be movable along the optical path of the laser beam, and 7 is a variable numerical aperture device.

As shown in FIGS. 2 and 3, the variable numerical aperture device 7 is supported movably along the optical path of the laser beam, focuses the laser beam on a predetermined position on the optical disk 5, and adjusts the aperture. It consists of a variable numerical aperture lens 8 that changes the numerical aperture, and a variable aperture lens moving actuator 9 that holds the variable numerical aperture lens 8 and moves it along the optical path of the laser beam by inputting a variable numerical aperture signal. .

Furthermore, the lens moving actuator 9 includes a movable barrel 9a that supports the variable numerical aperture lens 8, a circular spring 9b that supports the movable VJ barrel 9a so as to be movable in the optical path direction of the Lede light, and a movable barrel 9a that supports the variable numerical aperture lens 8. A coil 9 is wound around the outer periphery of the coil 9 and receives a variable numerical aperture signal and outputs magnetic flux according to the signal.
C, a yoke 9e fixed to the outer frame 9d close to the outer periphery of the coil 9C to increase the density of this magnetic flux, and a magnet 9 fixed to the outer frame 9d to attract and repel the magnetic flux of the coil 9C.
f, and l? which is fixed to the outer frame 9d and guides the movable cylinder 9a.
! Consists of 9g of ribs.

The coil 9C to which the variable numerical aperture signal is input generates magnetic flux in accordance with the signal, and this magnetic flux is attracted to and repelled by the coil 9C in accordance with the magnetic flux density by the magnet 9f via the yoke 9C. At this time, the movable tube 9a movably supported by the circular spring 9b around which the coil 9C is wound is moved guided by the sliding bush 9g, and the variable numerical aperture lens 8 supported by the movable tube 9a emits the laser beam. is moved in the direction of the optical path.

An optical recording/reproducing apparatus equipped with such a variable numerical aperture device 7 operates as follows.

That is, the diverging laser light emitted from the light emitting diode 1 is made into parallel light via the collimator lens 2, and is roughly divided by the movable mirror 3 and reflected in a direction substantially perpendicular to the direction of incidence. The parallel laser beam reflected from the movable mirror 3 is focused on a predetermined point on the optical disk 5 via the movable lens 4 and the variable numerical aperture lens 8.

At that time, a focus servo (actuator 6) is activated to accurately focus the laser beam onto the optical disc 5 in response to changes in the focal position due to surface wobbling of the optical disc 5, etc.
The focus position is changed by inputting a focus servo signal output from a servo circuit (not shown) and moving the movable lens 4 in the optical path direction of the laser beam in accordance with the signal.

In addition, when recording by making minute holes on the academic disc 5 by melting and evaporating the laser beam, much greater energy is required compared to the energy of the laser beam during reproduction. This is done by increasing the numerical aperture of the optical system, decreasing the diameter of the slot 1 for the laser beam focused on the optical disk 51, and increasing the density of the laser beam.

In other words, as shown in FIG. 4, the variable numerical aperture lens 8 is moved in the direction of the optical path of the laser beam by the variable numerical aperture lens 8 with the input variable numerical aperture means number. This is done by changing the distance between the lens 4 and the variable numerical aperture lens 8 to change the numerical aperture.

In other words, if the focal length of the variable numerical aperture lens 8 is fo and the focal length of the movable lens is fl, the focal length of the light that has passed through these two lenses @f is f = fO+
fl −rOfl, so f = fofl fO−)−fl −℃.

Here, if the change in the distance β between the movable lens 4 and the variable numerical aperture lens 8 is 6°C, then the change Δ[ in the focal length 111f of the light that has passed through these two lenses is Δf x
rofl fo ten f1-6℃.

Therefore, during recording, the spot diameter is reduced by reducing the distance between the movable lens 4 and the variable numerical aperture lens 8 to reduce the focal length and increasing the numerical aperture (Fig. 4-a).

In addition, since the surface runout of the optical disc 5 is very large, the variable numerical aperture lens 8 and the optical disc 5 are arranged close to each other.
When there is a collision between the two lenses, or when the vibration acceleration of the optical disc 5 is so large that the movement of the variable fj lens 4 cannot follow the movement, the distance between the variable numerical aperture lens 8 and the variable numerical aperture lens 4 may be (Increase the focal length by increasing
Such a problem can be eliminated by reducing the numerical aperture (FIG. 4-b).

The optical recording/reproducing system of the present invention can also be used in an optical disc with a multilayer recording film in which information is recorded in a plurality of layers.

[Effects of the Invention] As explained above, according to the optical recording and reproducing apparatus of the present invention, the aperture of the optical system that focuses light on the recording medium is adjusted by including the numerical aperture variable means that changes the numerical aperture. It is possible to provide an optical recording/reproducing device that can always obtain the optimum numerical aperture by changing the numerical aperture.

[Brief explanation of drawings]

FIG. 1 is a diagram for explaining one embodiment of the present invention, and FIGS. 2, 3, 13, and 4 are diagrams for explaining the variable numerical aperture equipment of this embodiment. 1......Light emitting diode 2...
・・・・・・・・・Colitar lens 3・・・・・・・
・・・・・・Movable mirror 4・・・・・・・・・Movable lens 5・・・・・・・・・Optical disc 6・
・・・・・・・・・Actuator 7・・・・・・
...... Numerical aperture variable device (numerical aperture variable means) 8...... Numerical aperture variable lens 9...
・・・・・・・・・Variable Numerical Aperture Lens Movement Actuator Applicant Toshiba Corporation Patent Attorney Satoshi Suyama - (b) Figure 4

Claims (1)

[Claims] (1) In an optical recording/reproducing device that reproduces information by focusing light onto a recording medium using an optical system, variable numerical aperture is provided between the optical system and the recording medium to change the numerical aperture. 1. An optical recording/reproducing apparatus comprising: means for changing the numerical aperture; and moving means for moving the numerical aperture variable means along the optical path of the light.