JPH1196582A - Objective lens adjusting method and adjusting device for optical head - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an adjusting method and an adjusting device capable of easily adjusting the inclination of the optical axis of the objective lens of an optical head for an optical disk and the position of the lens being on the optical axis and also capable of being constituted at a low cost. SOLUTION: A light beam from the semiconductor laser 204 of a adjusting device 200 is projected from an optical axis direction to the objective lens 101 of an optical head 100 and lights reflected at the surface of the lens 101 are received by a quadripartite photosensor 203 and the displacement of the reflected lights is detected and calculated from received light quantities of respective light receiving elements. Moreover, divergent lights reflected at the surface of the lens 101 are received by one pair of bisected photosensors 206, 207 and divergent states of the lights are detected and calculated from received light quantities of respective light receiving elements. The inclination of the optical axis of the objective lens 101 is detected from the calculated result of the sensor 203 and the position of the lens 101 on the optical axis is detected from the calculated result of the sensors 206, 207 and an adjustment making the inclination of the optical axis of the lens 101 zero is performed and, at the same time, the adjusting of the position of the lens 101 on the optical axis is performed by these detection results.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a phase change optical disk,
An optical head used to write and read information to and from an optical disk such as a magneto-optical disk, and more particularly to an adjustment method and adjustment for adjusting the tilt of the optical axis and the optical axis position of an objective lens provided in this type of optical head Related to the device.

[0002]

2. Description of the Related Art In an optical head for a recording disk, in order to read and write accurate and high-density information on the optical disk, the optical axis of an objective lens for converging light on the recording disk is required. It needs to be oriented perpendicular to the plane. Further, it is necessary to position the optical axis distance between the optical disk and the objective lens with high precision in accordance with the focal length of the objective lens. Therefore, conventionally, the objective lens is adjusted using an objective lens actuator adjustment device. FIG. 6 is a schematic configuration diagram showing one example. In the figure, an objective lens 101 of an optical head 100 has an objective lens 101 fixedly supported with its optical axis directed vertically upward in the figure so as to face a recording surface of an optical disk (not shown). A 45 ° mirror 106 is disposed on the lower optical axis of the objective lens 101. Collimated light from a light source (not shown) of the optical head 100 is deflected by 90 ° by the 45 ° mirror 106, The light enters the objective lens 101. The objective lens actuator 102 is mounted on a mounting table 103, and is supported by screws 104 via spring washers 105 in screw holes provided in at least two places. Therefore, by adjusting the screw 104, the objective lens actuator 102 can be tilted with respect to the mounting table 103, and the tilt angle of the optical axis of the objective lens 101 can be adjusted.

On the other hand, an adjusting device 400 for adjusting the inclination of the optical axis of the objective lens 101 has a numerical aperture larger than the numerical aperture of the objective lens, in this example, the numerical aperture of the objective lens 101 (= 0). .6) for the numerical aperture (= 0.
The objective lens for adjustment 9) is provided, and the objective lens for adjustment is disposed on the optical axis of the objective lens 101 with the cover glass 402 interposed therebetween. Also, the optical axis is set to 18 on the optical axis on the opposite side of the adjustment objective lens 401.
Two 45 ° mirrors 403, 404 to deflect 0 °
And a CCD sensor 406 disposed at a light focusing position of a focusing lens 405 for focusing the deflected light again. Then, the spot of light emitted from the objective lens 101 and to be imaged on the recording surface is once imaged by the adjustment objective lens 401 after passing through the cover glass 402, and the imaged light is further The light is received by the CCD sensor 406 by the focusing lens 405. At this time, the point image of the focal position of the adjustment objective lens 401 is magnified 1000 times by receiving the optical axis of the adjustment objective lens 401, and light is received by the CCD sensor 406. That is, the focused beam diameter of the adjustment objective lens 401 is 1 μm.
When m, the light is enlarged to 1 mm in diameter on the CCD sensor 406 and received. In addition, an inverse filter 407 having a filter characteristic opposite to that of the Gaussian distribution is disposed in front of the light receiving surface of the CCD sensor 406 in consideration of the fact that the point image of the focused beam substantially has a Gaussian distribution.
The point spread function obtained from the CCD sensor 406 corrects the characteristics of the inverse filter 407 by calculation.

In such an adjusting device, the CCD
An example of a point image obtained by the sensor 406 is shown in FIG. FIG. 7A shows a point image when the optical axis of the objective lens 101 is adjusted to a normal angle, the tangential direction (x-axis) of the beam at that time, and the radial direction (y-axis) of the optical disk.
Each of the light quantity distributions (axis) is shown by a solid line and a broken line, respectively.
The reason why the x-axis section and the y-axis section do not have the same shape is that the asbestos ratio of the emission beam of the semiconductor laser is not 1: 1. Generally, the asbestos ratio of the emitted light of a 680 nm laser is 1: 2. FIG. 7B shows a point image of the focused beam and its light amount distribution when the optical axis of the objective lens 101 is inclined in the tangential direction (x-axis) of the optical disk. This focused beam has so-called coma aberration, and a wavy fringe F is generated from the center of the focused beam toward the optical disk tangential method. Regarding the distribution of the focused beam, fringes are generated in one direction of the x-axis direction (solid line), but are not generated in the y-axis direction (dashed line). FIG. 7C shows a point image of the focused beam and its light amount distribution when the optical axis of the objective lens 101 is inclined in the radial direction (y-axis) of the optical disk. This focused beam has so-called coma aberration, and a wavy fringe F is generated from the center of the focused beam toward the optical disk tangential method. In the light intensity distribution of the focused beam, fringes are generated in one direction of the y-axis direction (broken line), but are not generated in the X-axis direction (solid line).

As described above, in the conventional adjusting device, the point image changes due to the inclination of the optical axis of the objective lens, and the inclination of the optical axis of the objective lens 101 can be detected not only from the pattern of the point image but also from the light amount distribution. . Therefore, FIGS. 7B and 7C
The direction of the objective lens actuator 102 is adjusted by adjusting the screw 104 shown in FIG. 6 so that the pattern and the light amount distribution are as shown in FIG. realizable. The optical system of the adjusting device is referred to as a pickup checker in this manner, and is described by Shinichi Katsura: “Optical Pickup Checker” Optics,
Vol. 3, No. 2 pp. 104-105 (1994-02).

[0006]

With such a conventional adjusting device, it is possible to adjust the inclination of the optical axis of the objective lens of the optical head, but it is not possible to adjust the optical axis position of the objective lens. I do not have. For this reason, it is necessary to adjust the optical axis position of the objective lens by another means, it is necessary to provide an independent adjusting device for that purpose, and the structure of the adjusting device becomes complicated, and the inclination of the optical axis of the objective lens and The position of the optical axis cannot be adjusted at the same time, and when one is adjusted first and then the other is adjusted, there arises a problem that the previous adjustment is out of order. In addition, the above-mentioned conventional adjusting device requires an expensive adjusting objective lens having a large numerical aperture, and there is a problem that the adjusting device becomes expensive.

SUMMARY OF THE INVENTION An object of the present invention is to provide a method and an apparatus for adjusting an objective lens of an optical head, wherein the inclination of the optical axis and the position of the optical axis of the objective lens can be adjusted simultaneously without using an expensive adjusting objective lens. Is to provide.

[0008]

According to the present invention, there is provided a method of adjusting an objective lens, comprising projecting a light beam from an optical axis direction to an objective lens of an optical head, wherein light reflected on the surface of the objective lens is directed to the optical axis. Detecting the state of deviation, detecting the inclination of the optical axis of the objective lens, detecting the divergence angle of divergent light generated by reflection on the surface of the objective lens, and determining the position of the objective lens on the optical axis. Detecting, and adjusting a tilt of an optical axis and an optical axis position of the objective lens based on each detection result.

Further, the objective lens adjusting device according to the present invention includes a means for projecting a light beam from an optical axis direction to an objective lens of an optical head, and a device for receiving light reflected on the surface of the objective lens on the optical axis. And a first light receiving means for detecting a deviation of the reflected light with respect to the optical axis, and a second light receiving means for detecting a diverging state of divergent light reflected on the surface of the objective lens. I do. Here, the first light receiving means is constituted by a four-division optical sensor divided into a x-direction and a y-direction on a plane perpendicular to the optical axis with the optical axis of the objective lens as a center. The difference in the amount of light received by the four elements is calculated to calculate the inclination of the optical axis of the objective lens. Further, the second light receiving means is a two-division optical sensor which is disposed at a position off the optical axis of the objective lens and has light receiving elements on the optical axis side and outside thereof along the radial direction with respect to the optical axis. And calculating the difference in the amount of light received by the two elements to calculate the position of the objective lens on the optical axis. Or,
The second light receiving means is constituted by a light position detecting element for detecting a luminous flux width of the divergent light reflected by the objective lens, and is provided on the optical axis of the objective lens by triangulation from the luminous flux width of the divergent light. Calculate the position.

In the present invention, the inclination of the optical axis of the objective lens is detected by the first light receiving means, the position of the objective lens on the optical axis is detected by the second light receiving means, and the detection result of the objective lens is detected based on these detection results. It is possible to adjust the position of the objective lens on the optical axis at the same time as performing the adjustment with the inclination of the optical axis set to 0.

[0011]

Next, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a schematic configuration diagram of a first embodiment of the objective lens adjusting device of the present invention. FIG. 2 is a schematic perspective view showing the configuration of the main part. The objective lens 101 to be adjusted is the optical head 1 as before.
00 is fixedly supported by an objective lens actuator 102, and a light beam from a light source (not shown) is
The light is reflected and deflected at 6, and is condensed by the objective lens 101 on the recording surface of the optical disk (not shown). The objective lens actuator 102 is supported on a mounting table 103 by screws 104 and spring washers 105.
By adjusting 4, the direction and the height position of the objective lens actuator 102 with respect to the mounting table 103 are changed, and accordingly, the inclination of the optical axis and the optical axis position of the objective lens 101 are adjusted. ing.

On the other hand, the adjusting device 200 comprises a quarter-wave plate 201 arranged along the optical axis of the objective lens 101,
Polarizing beam splitter 202 and quadrant optical sensor 2
03, a semiconductor laser 204 and a collimating lens 205 which are disposed opposite to the polarizing beam splitter 202 in a direction perpendicular to the optical axis, and the 波長 wavelength plate 20.
1 and a pair of split optical sensors 206 and 207 arranged on both sides of the quarter-wave plate 201. The laser beam emitted from the semiconductor laser 204 is made into a collimated beam larger than the diameter of the objective lens 101 by the collimating lens 205, and is incident on the polarization beam splitter 202 as an S-wave and reflected downward in the figure. Circularly polarized through the quarter-wave plate 201,
Incident on This light is reflected by the spherical or aspherical surface of the objective lens 101, and this reflected light is again reflected by the quarter wavelength slope 20.
1 through which the polarization beam splitter 202
, And travels straight, and is received by the four-divided optical sensor 203. Further, the light that has been diffused by being reflected on the surface of the objective lens 101 has
Light is received by the pair of split optical sensors 206 and 207.

FIG. 3 shows the four-division optical sensor 203, a pair of two-division optical sensors 206 and 207, and the objective lens 1.
FIG. 4 is a perspective view schematically showing a positional relationship with respect to 01, and FIG.
The divided light sensor 203 has a light receiving portion divided into four cells in a grid shape. When each element is A, B, C, and D, the light receiving amount of the light beam LB in each element is VA, V, respectively.
B, VC, and VD, the x-direction of these received light amounts,
By taking the respective differences in the y direction, the inclination of the optical axis of the objective lens with respect to the y direction, ie, the radial direction of the optical disk, and the x direction, ie, the tangential direction of the optical disk, can be calculated as follows:
R and ΔT can be detected. That is, ΘR, Θ
T is obtained from the following equation. ΘR = (VA + VD) − (VB + VC) ΘT = (VC + VD) − (VA + VB)

FIG. 3A shows a state where the inclination of the optical axis is 0, FIG. 3B shows a state where the optical axis is inclined in the x direction, and FIG. 3C shows a state where the optical axis is inclined in the y direction. The light receiving state of the four-division optical sensor in each of the inclined states is shown. This calculation can be obtained from the differential outputs of the respective elements A to D connected to a differential amplifier. Alternatively, digital operation can be performed via an A / D converter. Therefore, ΘR and ΘT are each “0”.
By adjusting the screw 104 shown in FIG. 1, the inclination of the objective lens actuator 102 with respect to the mounting table 103 is adjusted so that the optical axis of the objective lens 101 becomes x.
It is possible to adjust the optical axis to a state where the optical axis does not tilt in any of the direction and the y direction.

On the other hand, the pair of split optical sensors 206,
Reference numeral 207 indicates that the respective elements E and F and G and H are opposed to each other at positions symmetrical with respect to the optical axis. For these two-divided optical sensors 206 and 207, the objective lens 10
Since the divergence angle of the laser light reflected at 1 is constant, as shown in FIG. 4, each of the elements E to H is changed according to a change in the optical axis distance between the objective lens 101 and the two-divided optical sensors 206 and 207. The state of receiving the reflected light with respect to is changed.
That is, if the optical axis distance between the two-divided optical sensors 206 and 207 and the objective lens 101 is large, the diameter of the reflected light becomes large. Increase. Therefore, the value L indicating the height of the objective lens 101, ie, the position on the optical axis
Is obtained from the following equation. Each element E, F,
The amounts of light received at G and H are VE, VF, VG and VH, respectively. L = (VF + VG)-(VE + VH) Therefore, if the correlation between the value of L and the actual height of the optical axis of the objective lens is obtained in advance by actual measurement, the objective lens 101 can be controlled by controlling the value of L to obtain the desired light. It can be adjusted to the axial position. Also in this case, the screw 104 shown in FIG.
The adjustment can be realized by adjusting.

As described above, in the adjusting device of this embodiment, the operation value obtained by the detection by the four-division optical sensor 203 and the operation value obtained by the detection by the two-division optical sensors 206 and 207 are simultaneously observed. By performing the adjustment with the screw 104, the inclination of the optical axis and the position of the optical axis of the objective lens 101 can be simultaneously adjusted. Therefore, it is possible to adjust the objective lens 101 to a preferable state with one adjusting device, and it is possible to reduce the cost of the adjusting device and to easily perform the adjusting operation.

FIG. 5 is a diagram showing a schematic configuration of an adjusting device according to a second embodiment of the present invention, and portions equivalent to those of the first embodiment are denoted by the same reference numerals. In the configuration of this embodiment, the above-described two-divided optical sensor is not provided, but a beam position detection sensor (PSD: Positioning Sequential Sensor) is used instead.
nsor Device) 300 is used. That is, a second polarizing beam splitter 208 is disposed adjacent to the polarizing beam splitter 202 in the optical axis direction, and the light reflected by the second polarizing beam splitter 208 is transmitted to the PSD3.
It is configured to receive light at 00. In particular, this PD
In S300, the maximum point of the amount of light of the beam to be received is recognized as the optical axis position, and the divergence state of the beam is detected from the light receiving limit point in a region directed to one side from the optical axis position.

In the adjusting device according to the second embodiment, the collimated light from the semiconductor laser 204 is made to enter the polarizing beam splitter 202 as an S wave, is converted into circularly polarized light through the quarter-wave plate 201, and is transmitted to the objective lens 101. Make it incident. The surface reflected light from the objective lens 101 is
The light is slightly diverged by the one spherical surface or the aspherical surface, passes through the quarter-wave plate 201 again, and then goes straight through the polarizing beam splitter 202. Then, in the polarization beam splitter 202, a part is transmitted and received by the four-division optical sensor 203. The other part is reflected by the second polarization beam splitter 208 and received by the PSD 300. Therefore, the adjustment of the inclination of the optical axis of the objective lens 101 can be performed by detecting light reception by the four-division optical sensor 203 as in the first embodiment.

On the other hand, in adjusting the optical axis position of the objective lens,
The detection in the PSD 300 is used. This PSD
300 can be used as it is (Keyence). Here, a method to which triangulation is applied is used, and a point having the highest light receiving intensity on the PSD 300 and a point having a required light receiving level at a position apart from this point are detected. The point having the high light receiving intensity is the optical axis point, and the latter having the required light receiving level is the maximum deflection point when the light is reflected in the divergent state on the surface of the objective lens. Therefore, the distance between the optical axis point and the deflecting point in the PSD 300 increases when, for example, the objective lens 101 is positioned below in the figure due to a change in the optical axis position of the objective lens 101. , The distance decreases.
Therefore, the distance between the optical axis point and the deflecting point is defined as PSD300.
The optical axis position of the objective lens having a correlation with the calculated value can be detected by performing the calculation based on the measured value in the above. As a document of this technique, there is JP-A-1-74405.

Therefore, also in the second embodiment, the adjustment with the screw 104 is performed while simultaneously observing the operation value obtained by the detection by the four-split optical sensor 203 and the operation value obtained by the detection by the PSD 300. By doing
The inclination of the optical axis of the objective lens 101 and the position of the optical axis can be adjusted simultaneously. Therefore, it is possible to adjust the objective lens to a preferable state with one adjusting device, and it is possible to reduce the cost of the adjusting device and to easily perform the adjusting operation.

Here, in order to perform the above-mentioned adjustment in the present invention, the beam diameter of the laser beam incident on the objective lens must be larger than the diameter of the objective lens, or at least half the diameter of the objective lens. Is preferred. When adjusting the position of the optical axis of the objective lens by PSD, a spot having a high light intensity is projected toward the objective lens, and the amount of deflection when the spot light is reflected by the surface of the objective lens is determined by PSD. The optical axis position of the objective lens may be detected by measuring. In the adjustment method and the adjustment device of the present invention, the laser wavelength 680 n
optical head using an objective lens with a numerical aperture of 0.8
Adjustment of the inclination of the optical axis of the objective lens of the optical head for recording / reproducing information on an optical disk capable of high-density recording with a bit length of 0.32 μm or less and high-precision adjustment of the lens optical axis position have been achieved.

[0022]

As described above, according to the present invention, a light beam is projected onto an objective lens of an optical head from the optical axis direction.
First light receiving means for receiving the light reflected on the surface of the objective lens on the optical axis and detecting the deviation of the reflected light with respect to the optical axis, and detecting the diverging state of the divergent light reflected on the surface of the objective lens. Since the second light receiving means is provided, the inclination of the optical axis of the objective lens is detected by the first light receiving means, and the position of the objective lens on the optical axis is detected by the second light receiving means. As a result, the adjustment of the tilt of the optical axis of the objective lens to zero can be performed, and at the same time, the position of the objective lens on the optical axis can be adjusted. Can be implemented.

[Brief description of the drawings]

FIG. 1 is a front configuration diagram showing a schematic configuration of a first embodiment of the present invention.

FIG. 2 is a schematic perspective view of a main part of the first embodiment.

FIG. 3 is a diagram for explaining the operation of the four-division optical sensor.

FIG. 4 is a diagram for explaining an operation in the two-segment optical sensor.

FIG. 5 is a front configuration diagram showing a schematic configuration of a second embodiment of the present invention.

FIG. 6 is a diagram showing a schematic configuration of an example of a conventional objective lens adjustment device.

FIG. 7 is a diagram for explaining an inclination adjustment operation of an optical axis in a conventional device.

[Explanation of symbols]

 REFERENCE SIGNS LIST 100 Optical head 101 Objective lens 102 Objective lens actuator 103 Mounting stand 104 Screw 200 Adjuster 210 Quarter-wave plate 202 Polarized beam splitter 203 Quadrant optical sensor 204 Semiconductor laser 205 Collimator lens 206, 207 Bipartite optical sensor 208 Second Polarizing beam splitter 300 PSD

Claims (6)

[Claims] 1. A light beam is projected onto an objective lens of an optical head from an optical axis direction, and a state in which reflected light on the surface of the objective lens is deviated with respect to the optical axis is detected. Detecting the inclination of the axis, detecting the divergence angle of the divergent light generated by the reflection on the surface of the objective lens, detecting the position of the objective lens on the optical axis, and detecting the position of the objective lens based on each detection result. A method for adjusting an objective lens of an optical head, comprising adjusting an inclination of an optical axis and an optical axis position. 2. A means for projecting a light beam from an optical axis direction to an objective lens of an optical head, receiving light reflected on a surface of the objective lens on an optical axis, and transmitting the reflected light with respect to the optical axis. A first light receiving means for detecting the deviation, and a second light detecting means for detecting a diverging state of the diverging light reflected on the surface of the objective lens
An objective lens adjusting device for an optical head, comprising: a light receiving unit. 3. The first light receiving means is constituted by a four-division optical sensor divided into an x-direction and a y-direction on a plane perpendicular to the optical axis with the optical axis of the objective lens as a center. 3. The objective lens adjusting device for an optical head according to claim 2, wherein a difference in the amount of light received by the four divided elements is calculated to calculate the inclination of the optical axis of the objective lens. 4. The two-divided light receiving means is disposed at a position off the optical axis of the objective lens, and has two light receiving elements on the optical axis side and outside thereof along the radial direction with respect to the optical axis. 4. The objective lens adjusting device for an optical head according to claim 2, wherein the objective lens adjusting device comprises an optical sensor, and calculates a difference in an amount of light received by the two elements to calculate a position on the optical axis of the objective lens. 5. The second light receiving means comprises a light position detecting element for detecting a luminous flux width of the divergent light reflected by the objective lens, and the objective lens is formed by triangulation from the luminous flux width of the divergent light. 4. The objective lens adjusting device for an optical head according to claim 2, wherein the position on the optical axis is calculated. 6. The objective lens according to claim 2, wherein the means for projecting the light beam projects a light beam having a light beam diameter greater than or equal to a diameter of the objective lens or at least a half of the diameter of the objective lens. 3. The objective lens adjusting device for an optical head according to claim 1.