JPH04170734A - Exposing device for original plate of optical disk - Google Patents

Abstract

PURPOSE:To control a focus stably and at high speed by a method wherein the following are formed in a light path toward an object lens for a laser beam for optical-bit formation use: a polarizing element; a plurality of relay lenses whose focal distances are different; and a distance sensor used to measure a change in a focal distance. CONSTITUTION:A laser beam radiated form a laser light source 1 is passed through a mirror 2, a deflector 3, a mirror 4, a central relay lens 5b out of relay lenses 5a to 5c and a mirror 6 sequentially and is condensed on an optical- disk original plate 8 via an object lens 7; an information bit is formed. A change in the distance between the object lens 7 and the original plate 8 is detected by using a distance sensor 9; the amount of the change is transmitted to the deflector 3. The deflector 3 selects one out of the lenses 5a to 5c on the basis of the amount of the change; the laser beam is radiated toward the lens.

Description

[Detailed description of the invention] Industrial applications The present invention relates to an optical disc master exposure apparatus.

Conventional technology In conventional optical disk master exposure devices, when laser light emitted from a laser light source is focused by an objective lens and irradiated onto the optical disk master, the diameter of the focused light spot is always kept constant. Focus servo is used to maintain this.

This focus servo moves the objective lens in the optical axis direction using an objective lens actuator based on the detected focus error signal, and corrects the varying distance between the optical disk master, which is the imaging surface, and the objective lens. A constant, focused light spot is always irradiated onto the optical disc master.

Problems to be Solved by the Invention When performing this focus servo, if the diameter of the optical spot is made smaller in order to achieve higher density, the shape of the objective lens becomes larger, and as a result, the focus servo must be performed at an even higher speed. If an attempt is made to do so, the circuit fabrication becomes extremely complicated and difficult, and vibrations are transmitted throughout the apparatus, adversely affecting the exposure quality.

Means for Solving the Problem Therefore, in order to solve such problems, claim 1
In the invention described above, in an optical disk master exposure device that forms information bits by focusing laser light emitted from a laser light source using an objective lens and exposing the light onto an optical disk master, the laser light emitted from the laser light source is A deflection element for deflecting the optical path of the laser beam is disposed on the optical path while the laser beam heads toward the objective lens, and the incident angle of the laser beam to the objective lens changes on the optical path deflected by the deflection element. A plurality of relay lenses having mutually different focal lengths are arranged, and a distance sensor is provided to measure the focal length variation distance between the objective lens and the optical disc master.

In the invention set forth in claim 2, in the invention set forth in claim 1, the relay lens is located at a position where a focal position determined by the relay lens and the objective lens falls within a range in which the depths of focus of the relay lenses overlap each other little by little. It was placed in

In the invention according to claim 3, in the optical disc master exposure apparatus that forms information bits by condensing the laser light emitted from the laser light source with an objective lens and exposing the light onto the optical disc master, the laser light emitted from the laser light source is A deflection element for deflecting the optical path of the laser beam is disposed on the optical path of the laser beam heading toward the objective lens, and the incident angle of the laser beam to the objective lens is set on the optical path deflected by the deflection element. A single relay lens having a plurality of variable focal lengths was disposed, and a distance sensor was provided for measuring a focal length variation distance between the objective lens and the optical disk master.

In the invention as set forth in claim 4, in the optical disk master exposure apparatus that forms information bits by condensing the laser light emitted from the laser light source with an objective lens and exposing the light onto the optical disk master, the laser light emitted from the laser light source is A deflection element for deflecting the optical path of the laser beam is disposed on the optical path of the laser beam heading toward the objective lens, and the incident angle of the laser beam to the objective lens is set on the optical path deflected by the deflection element. A single relay lens whose focal length changes continuously by changing the incident position thereof is provided, and a distance sensor is provided that measures the focal length variation distance between the objective lens and the optical disc master. Ta.

The invention as claimed in claim 1 is a method that enables a laser beam to be selectively incident on a relay lens using a deflection element such that a distance change obtained by a distance sensor falls within a depth of focus including a focal position, thereby achieving a change in the distance as compared to the conventional one. It is possible to eliminate problems such as resonance and oscillation phenomena that are unique to objective lens actuators that have moving parts.This makes it possible to realize a much simpler objective lens actuator that does not have moving parts, and provides stable and high-speed focusing at all times. It becomes possible to perform control.

In the invention as claimed in claim 2, the relay lenses are configured with focal lengths whose depths of focus overlap with each other, so that the lens selected from the relay lenses is within the overlap range of focal depths for a focal length variation distance. Since lenses in either region can be used, it is possible to suppress fluctuations in the optical spot diameter when switching between relay lenses.

The invention according to claim 3 can obtain the same effect as the invention according to claims 1 and 2 by using a single relay lens having a plurality of focal lengths instead of a plurality of relay lenses. becomes.

The invention according to claim 4 is achieved by using a single relay lens whose focal length changes continuously by changing the incident position instead of a plurality of relay lenses.
It becomes possible to obtain the same effects as the described invention.

Example An embodiment of the present invention will be described based on the drawings.

FIG. 1 shows the overall configuration of this device. On the optical path of the laser beam emitted from the laser light source 1 via the mirror 2, a deflector 3 is disposed as a deflection element that deflects the optical path of the laser beam. Three relay lenses 5a, 5b, and 5c having mutually different focal lengths are arranged on each optical path (here, three optical paths) deflected by this deflector 3 via a mirror 4. There is. Furthermore, an objective lens 7 is disposed on the optical path of the light that has passed through these relay lenses 5a, 5b, and 5c via a mirror 6, and an optical disc master 8 is disposed close to the objective lens 7. ing. Note that the angle of incidence of the laser beams that have passed through the relay lenses 5a, 5b, and 5c on the objective lens 7 changes. Furthermore, a distance sensor 9 is provided at a position close to the objective lens 7 to measure the focal length variation distance between the objective lens 7 and the optical disk master 8.

Moreover, in this case, the three relay lenses 5a.

5b, 5c, the focal position determined by the relay lenses 5a, 5b, 5C and the objective lens 7 is the relay lens 5.
The focal depths of a, 5b, and 5c are arranged within a range where they overlap each other little by little.

In such a configuration, the deflector 3 and the relay lens 5a,
A method of performing focus servo using 5b and 5c will be described. The laser beam emitted from the laser light source 1 passes through a mirror 2, a deflector 3, a mirror 4, a relay lens 5b located at the center, and a mirror 6 in order, and then is condensed by an objective lens 7 to form an optical disc master 8. Light spots can be connected on top, thereby forming information bits.

Assume that the distance between the objective lens 7 and the optical disc master 8 changes. At this time, the distance sensor 9 detects the amount of change in distance (focus change distance) and sends the amount of change to the deflector 3. The deflector 3 selects one of the relay lenses 5a, 5b, and 5c based on the amount of variation, and emits a laser beam toward that lens.

Now, for example, as shown in FIG.
Assuming that the amount of variation is within B within the focus position B and the depth of focus due to the relay lens 5b, focus servo is performed by the relay lens 5b. However, when the objective lens 7 approaches the optical disc master 8 and deviates from the focal depth of the central relay lens 5b, the deflector 3 swings the laser beam so that the laser beam enters the relay lens 5a. control is carried out. As a result, the focal position of the objective lens 7 changes from the focal position to the focal position a, as shown in FIG. The diameter of the light spot becomes substantially constant, which makes it possible to perform focus servo.

In addition, on the contrary, the objective lens 7 is the optical disc master 8.
If the beam moves away from the beam, the deflector 3 causes the beam to enter the relay lens 5C side, and as shown in FIG. This makes it possible to perform focus servo.

As described above, the laser beam is selectively incident on one of the relay lenses 5a, 5b, and 5c by the deflector 3 such that the distance variation obtained by the distance sensor 9 falls within a predetermined depth of focus including the focal position. By doing so, it is possible to eliminate problems such as resonance and oscillation phenomena that are unique to conventional objective lens actuators that have moving parts.This makes it possible to realize a much simpler objective lens actuator that does not have moving parts. At the same time, stable and high-speed focus control can be performed at all times.

In addition, by making the relay lenses 5a, 5b, and 5c have focal lengths such that their focal depths overlap with each other, the relay lenses 5a, 5b, and 5c are designed to have focal lengths that overlap each other.
The lens selected from 5c can be used in either range within the overlap range of focal depth.
It is possible to suppress fluctuations in the optical spot diameter when switching between relay lenses 5a, 5b, and 5c.

In addition, in the above-mentioned embodiment, a plurality of relay lenses (3
However, the invention is not limited to this, and in addition, for example, a single multifocal lens having a plurality of focal lengths so that the incident angle of the laser beam to the objective lens 7 changes, and furthermore, Even if a single continuous focus lens whose focal length changes continuously by changing the incident position so that the incident angle of the laser beam to the objective lens 7 changes respectively, a plurality of relay lenses 5a, The same effect as in the case of 5b and 5c can be obtained.

In addition, although the light deflected by the deflector 3 is selectively made to enter the relay lenses 5a, 5b, and 5C arranged in a straight line in FIG. A polygonal reflecting member (not shown) is arranged, a deflector 3 is arranged at the top of the member, and a plurality of relay lenses 5a, 5b,
This can also be realized by providing 5c.

Effects of the Invention The invention according to claim 1 provides an optical disc master exposure apparatus that forms information pits by condensing laser light emitted from a laser light source with an objective lens and exposing the optical disc master, in which the laser light source A deflection element that deflects the optical path of the laser beam emitted from the laser beam toward the objective lens is disposed on the optical path of the laser beam, and a deflection element that deflects the optical path of the laser beam directed to the objective lens is provided on the optical path deflected by the deflection element. A plurality of relay lenses each having a different focal length so that the incident angle changes, and a distance sensor for measuring the focal length variation distance between the objective lens and the optical disk master are provided, so that the distance sensor By selectively injecting the laser beam into the relay lens using a deflection element such that the distance fluctuation obtained by the above falls within the depth of focus including the focal position, resonance and resonance peculiar to conventional objective lens actuators having movable parts can be avoided. Problems such as oscillation phenomena can be eliminated, and as a result, it is possible to realize a much simpler objective lens actuator that does not have a movable part, and it is possible to always perform stable and high-speed focus control.

The invention according to claim 2 is the invention according to claim 1,
The relay lens is arranged at a position where the focal position determined by the relay lens and the objective lens falls within a range in which the depths of focus of the relay lenses overlap each other little by little. Since the lenses selected from the above can be used in either region within the overlapping range of focal depths, fluctuations in the optical spot diameter when switching relay lenses can be suppressed to a small level.

The invention according to claim 3 provides an optical disc master exposure apparatus that forms information bits by condensing laser light emitted from a laser light source using an objective lens and exposing the light onto an optical disc master, in which the laser light emitted from the laser light source is A deflection element for deflecting the optical path of the laser beam is disposed on the optical path of the laser beam heading toward the objective lens, and the incident angle of the laser beam to the objective lens is set on the optical path deflected by the deflection element. A single relay lens having a plurality of focal lengths, each of which varies, is provided, and a distance sensor for measuring the focal length variation distance between the objective lens and the optical disc master is provided. By using a single relay lens having a plurality of focal lengths instead of the relay lens, it is possible to obtain effects similar to those of the invention described in claims 1 and 2.

The invention according to claim 4 provides an optical disk master exposure apparatus that forms information bits by condensing a laser beam emitted from a laser light source by an objective lens and exposing the laser beam onto an optical disk master. A deflection element for deflecting the optical path of the laser beam is disposed on the optical path of the laser beam heading toward the objective lens, and the incident angle of the laser beam to the objective lens is set on the optical path deflected by the deflection element. A single relay lens whose focal length changes continuously by changing the incident position thereof is provided, and a distance sensor is provided that measures the focal length variation distance between the objective lens and the optical disc master. Therefore, by using a single relay lens whose focal length changes continuously by changing the incident position instead of a plurality of relay lenses, the invention similar to the inventions described in claims 1 and 2 can be achieved. It is something that can be effective.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention, and FIG. 2 is an explanatory diagram showing the relationship between focal length and depth of focus of the relay lens. DESCRIPTION OF SYMBOLS 1... Laser light source, 3... Deflection element, 5a-5c.
... Relay lens, 7... Objective lens, 8... Optical disc master, 9... Distance sensor

Claims (1)

[Claims] 1. In an optical disc master exposure device that forms information bits by condensing laser light emitted from a laser light source using an objective lens and exposing the light onto an optical disc master, the laser light emitted from the laser light source A deflection element for deflecting the optical path of the laser beam is disposed on the optical path of the laser beam heading toward the objective lens, and the incident angle of the laser beam to the objective lens is set on the optical path deflected by the deflection element. An optical disc master, characterized in that a plurality of relay lenses each having a different focal length so as to vary, and a distance sensor for measuring a focal length variation distance between the objective lens and the optical disc master are provided. Exposure equipment. 2. The relay lens is disposed at a position where the focal position determined by the relay lens and the objective lens falls within a range in which the depths of focus of the relay lenses overlap each other little by little. optical disc master exposure equipment. 3. In an optical disk master exposure device that forms information bits by condensing laser light emitted from a laser light source with an objective lens and exposing it onto an optical disk master, the laser light emitted from the laser light source is focused on the objective lens. A deflection element for deflecting the optical path of the laser beam is disposed on the optical path toward the lens, and a plurality of deflection elements are arranged on the optical path deflected by the deflection element so that the incident angle of the laser beam to the objective lens changes. What is claimed is: 1. An optical disk master exposure apparatus, characterized in that a single relay lens having a focal length of 1 is disposed, and a distance sensor is provided for measuring a focal length variation distance between the objective lens and the optical disk master. 4. In an optical disk master exposure device that forms information bits by condensing a laser beam emitted from a laser light source by an objective lens and exposing it onto an optical disk master, the laser beam emitted from the laser light source is focused on the objective lens. A deflection element for deflecting the optical path of the laser beam is disposed on the optical path toward the lens, and the laser beam is incident on the optical path deflected by the deflection element so that the incident angle of the laser beam to the objective lens changes. A single relay lens whose focal length changes continuously by changing its position is provided, and a distance sensor is provided to measure the focal length variation distance between the objective lens and the optical disc master. Optical disc master exposure equipment.