JPH0935319A - Optical information recorder, optical device and aberration adjusting method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a means detecting aberration caused by slopes of an optical disk and an objective lens and correcting it. SOLUTION: Aberration generation parts 8, 9 are set up on the way of an optical path from a semiconductor laser 2 to the optical disk 3, e.g. in a light convergent or divergent part. The aberration generation parts 8, 9 are constituted of transparent parallel planes, and are constituted so as to be inclinable around prescribed axes facing in the direction nearly vertical to each other. Then, the aberration caused by the slopes of the optical disk 3 or the objective lens 12 are canceled by the aberration caused by properly inclining the parallel planes 8, 9. Thus, information is recorded/reproduced stably even when the optical disk 3 or the objective lens 12 is sloped.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical information recording device for optically recording and reproducing information, an optical device for irradiating an object with light, and an optical information recording device and an aberration adjusting method for the optical device. is there.

[0002]

2. Description of the Related Art In an optical disk such as a CD, the central optical axis of the objective lens of the optical pickup is generally perpendicular to the optical disk, and the light beam is made to enter the optical disk substantially perpendicularly. . However, when the objective lens or the optical disc is tilted, aberration occurs, which hinders the recording and reproduction of information. In particular, when an objective lens having a high NA (NA is the numerical aperture of the lens) is used for high density recording, the generated aberration becomes large and the margin for the tilt becomes small.

In order to solve such a drawback, it has been proposed to detect the tilt of the objective lens or the optical disk and correct the tilt based on the detection result (for example,
The 42nd Japan Society of Applied Physics, Spring 1995, "Proceedings of Lectures" No. 3, pages 1062 to 1063, JP-A-3-273534, JP-A-3-137831, and JP-A-4-103042. Issue Bulletin).

[0004]

However, in the above-mentioned conventional technique, when the tilt detection method has an offset, the aberration cannot be corrected well. That is,
It is the aberration that should be directly corrected in constructing the device, and if the aberration can be effectively corrected, it is not necessary to correct the tilt. However, in the conventional technology, for example, a structure that corrects the tilt of the objective lens is used. Therefore, there is a drawback that the structure around the objective lens becomes very complicated.

In order to increase the tilt margin, an optical disc having a thin substrate has been proposed.
There is a drawback that compatibility cannot be guaranteed if the thicknesses of the substrates are different.

An object of the present invention is to detect aberrations caused by the tilt of an objective lens or an optical disk, thereby making it possible to correct aberrations without complicating the structure around the objective lens too much, and to obtain various substrate thicknesses. SUMMARY OF THE INVENTION It is an object of the present invention to propose an optical information recording apparatus capable of recording / reproducing information on / from the optical disc and an aberration adjusting method in the optical information recording apparatus.

Another object of the present invention is to make it possible to realize aberration correction in an optical device without complicating the structure around the objective lens so much as in the optical information recording device.

[0008]

In order to achieve the above object, the present invention provides an information recording medium capable of reproducing information or recording and reproducing information by optical means, a light source, and light emitted from the light source. A lens element for condensing and irradiating the information recording medium, an information detecting means for reproducing information recorded on the information recording medium from reflected light, transmitted light or scattered light of the light emitted by the lens element, and a lens Position detecting means for detecting the position of the focal point of the lens element on the information recording medium from the reflected light, transmitted light or scattered light of the light emitted by the element, moving means for moving the lens element, and position In an optical information recording device including: a control unit that drives the moving unit based on the output from the detection unit to control the position of the focal point on the information recording medium, A parallel plate that generates aberration is provided in the middle of the optical path from the light source to the information recording medium, and the aberration that occurs in the lens element and the substrate portion of the information recording medium is canceled by the aberration that occurs in the parallel plate. It is a thing.

In place of the parallel plate described above, a hologram element in which the aberration of diffracted light changes depending on the tilt or the position where the light hits is provided, and the aberration generated in the lens element and the substrate portion of the information recording medium is generated in the hologram element. It can also be configured so as to be canceled by the aberration that occurs.

Further, instead of the parallel plate described above, an electro-optic crystal that produces an aberration by applying an electric charge, a current, a voltage or an electric field is provided, and the aberration produced in the lens element and the substrate portion of the information recording medium is electro-optic. It can also be configured so as to be canceled by the aberration generated in the crystal.

More specifically, according to the present invention, an information recording medium capable of reproducing or recording / reproducing information by an optical means, a light source, and an information recording medium by collecting light emitted from the light source. Of the light emitted by the lens element, and the information detection means for reproducing the information recorded on the information recording medium from the reflected light, the transmitted light or the scattered light of the light emitted by the lens element. Based on the output from the position detecting means for detecting the position of the focal point of the lens element on the information recording medium from the reflected light, the transmitted light or the scattered light, the moving means for moving the lens element, and the position detecting means. In the optical information recording device, the optical information recording device is provided with a control unit that drives the moving unit to control the position of the focal point on the information recording medium, and is provided in the optical path from the light source to the information recording medium. From the reflected light, the transmitted light or the scattered light of the light irradiated onto the information recording medium by the lens element, It is characterized in that it comprises an aberration detecting means for detecting an aberration generated on the information recording medium, and an actuator control means for controlling the drive of the actuator so that the aberration detected by the aberration detecting means is minimized. .
Incidentally, it is convenient to install, for example, a split photodiode as the aberration detecting means.

Instead of the parallel plate described above, a hologram element in which the aberration of the diffracted light changes depending on the tilt or the position where the light hits is provided, and the tilt or the light of the hologram element is minimized so that the aberration generated on the information recording medium is minimized. A configuration in which the contact position is changed may be adopted.

Further, instead of the above parallel plate, an electro-optic crystal which produces an aberration upon application of electric charge, current, voltage or electric field is provided, and the electro-optic crystal is made to minimize the aberration produced on the information recording medium. It may be configured to adjust the applied charge, current, voltage or electric field.

The present invention can also be applied to general optical devices. That is, in an optical device having an optical system that irradiates a predetermined object with light emitted from a light source, one of the above-mentioned parallel plate, hologram element, and electro-optic crystal is provided in the optical path from the light source to the predetermined object. Set up. And
The parallel plate, the hologram element, or the electro-optic crystal has a configuration in which the aberration of the light emitted to a predetermined object is set to a predetermined value or the aberration generated in the optical system can be canceled.

According to the aberration adjusting method of the present invention, when adjusting the aberration in the optical path system for converging the light emitted from the light source and irradiating it onto the optical disk, a parallel plate that causes the aberration due to the inclination with respect to the irradiation light from the light source. Is installed in the middle of the optical path system, a transparent disc is installed in the place where the optical disc is attached, and then the light source is turned on to measure the aberration of the light transmitted through the transparent disc, and the aberration is a predetermined value. It is to adjust the inclination of the parallel plate so that. The light source may be turned on to measure the focal spot of the light transmitted through the transparent disc, and the inclination of the parallel plate may be adjusted so that the focal spot is minimized.

A hologram element is provided in place of the parallel plate, and the aberration of the light transmitted through the transparent disc becomes a predetermined value, or the focal spot of the light transmitted through the transparent disc is minimized. You may adjust the inclination or the position where the light hits.

Further, an electro-optic crystal is provided in place of the parallel plate so that the aberration of the light transmitted through the transparent disc becomes a predetermined value or the focal spot of the light transmitted through the transparent disc is minimized. Charge applied to the optical crystal,
The current, voltage or electric field may be adjusted.

The aberration adjusting method of the present invention can also be applied to a general optical device. That is, in an optical device having an optical system that irradiates a predetermined object with light emitted from a light source, one of the above-mentioned parallel plate, hologram element, and electro-optic crystal is provided in the optical path from the light source to the predetermined object. Set up. Then, the inclination of the parallel plate, the inclination of the hologram element, or the optical axis of the light is adjusted so that the aberration of the light emitted to a predetermined object becomes a predetermined value or the focal spot of the light emitted from the optical system is minimized. The contact position or the electric charge, current, voltage or electric field applied to the electro-optic crystal is adjusted.

[0019]

[Operation] If a parallel plate is inserted in the convergent or divergent light,
Generally, spherical aberration occurs, and coma and astigmatism occur when the parallel plate is tilted with respect to the optical axis. The optical disc has a structure in which light is focused on a recording film through a transparent parallel plate. Therefore, aberration occurs in the transparent parallel plate portion, but spherical aberration can be corrected by the objective lens. When the optical disc is tilted with respect to the optical axis, coma and astigmatism occur. Here, the coma aberration is a first-order amount with respect to the tilt of the disc, and the astigmatism is a second-order amount. Therefore, astigmatism can be ignored when the tilt of the optical disc is small.

In the present invention, a transparent parallel plate is inserted in the middle of the optical path from the light source to the objective (optical disk) for the information recording medium, for example, at the portion where the light converges or diverges. Also in this case, when the parallel plate is tilted with respect to the optical axis, coma aberration occurs, and this aberration can cancel the coma aberration caused by the tilt of the optical disk. Also,
In the present invention, it is possible to cancel not only the aberration caused by the tilt of the optical disk but also the aberration caused by the mounting error of the objective lens and other optical parts. Similar effects can be obtained by inserting an optical component that generates aberrations in the middle of the optical path other than the transparent parallel plates.

Even if a hologram element is provided instead of the parallel plate, the same effect can be obtained. In this case, the coma aberration generated by the tilt of the optical disc can be canceled by adjusting the tilt of the hologram element or the position on which the light hits.

Further, even if an electro-optic crystal is provided instead of the parallel plate, the same effect can be obtained. In this case, by adjusting the electric charge, current, voltage or electric field applied to the electro-optic crystal, the coma aberration generated by the tilt of the optical disc can be canceled.

Further, when the return light from the optical disc is focused by a lens, a small spot is obtained when there is no aberration, but the spot spreads when there is aberration. In particular, when there is coma, the spot spreads in such a way that a tail is drawn in the direction in which the aberration occurs. Therefore, the return light from the optical disk is narrowed down by a lens so that it is condensed on the dividing line of the divided photodiode, for example.
Then, by comparing the outputs of the divided photodiodes, the direction and amount of the aberration can be easily known.

[0024]

Embodiments of the present invention will now be described in detail with reference to the drawings. (First Embodiment) First, a first embodiment of the present invention will be described with reference to FIGS. FIG. 1 is an explanatory diagram of an optical system of an optical disc device, FIG. 2 is an explanatory diagram of an operation principle, FIG. 3 is an explanatory diagram of an aberration caused by the tilt of an optical disc, FIG. 4 is an enlarged diagram of an aberration detection unit, and FIGS. Is a plan view of a split photodiode as an aberration detection unit, FIGS. 7 and 8 are plan views of a position detection element as an aberration detection unit, FIG. 9 is an explanatory diagram of the aberration detection unit, and FIG. 10 is an enlarged view of the aberration generation unit. 11, FIG. 11 is an explanatory diagram of the operation of the aberration generating unit, FIG. 12 is an enlarged view of the aberration generating unit, FIG. 13 is an explanatory diagram of the operation of the aberration generating unit, FIG. 14 is an explanatory diagram of the operation of the raising mirror, and FIG. Principle diagram showing the principle of aberration cancellation, FIG.
6 and 17 are principle diagrams of the aberration generating hologram, FIGS. 18 and 19 are enlarged views of the actuator for moving the hologram element, and FIG. 20 is an explanatory diagram of the aberration generating unit using the electro-optic crystal.

In FIG. 1, when a command for recording or reproducing information is inputted to the system controller 1 from the outside of the apparatus, the system controller 1 supplies a current to a spindle motor (not shown) so that the optical disk 3 is read. Rotate around the rotating shaft 4. Further, the system controller 1 also supplies a current to the semiconductor laser 2 to turn on the semiconductor laser 2.

The light emitted from the semiconductor laser 2 when the semiconductor laser 2 is turned on is collimated by the collimator lens 5, passes through the beam splitter 6, is condensed by the lens 7, and passes through the aberration generating portions 8 and 9. After that, it becomes parallel light again by the lens 10 and is reflected by the rising mirror 11.
The reflected light is condensed by the objective lens 12 and condensed on the recording film 13 on the optical disc 3. This light is recorded on the recording film 1
After being reflected by 3 and collimated by the objective lens 12, it is reflected again by the rising mirror 11 and passes through the lens 10, the aberration generating portions 9 and 8 and the lens 7, and enters the beam splitter 6. Then, a part of this light is reflected by the beam splitter 6, a further part of the reflected light is transmitted through the beam splitter 14, is reflected by the mirror 15, and is incident on the optical pickup 16.

The optical pickup 16 has a function of detecting information recorded on the optical disk 3, a function of detecting a focus error indicating a focus blur of the focus formed by the objective lens 12 on the recording film 13, and an optical disk 3. It has a function of detecting a track error, which is a row of recording pits provided concentrically or spirally on the upper side, and indicates a deviation of the focus from the recording track.

The system controller 1 drives the objective lens actuator 19 according to the focus error signal detected by the optical pickup 16 to control the focus so that defocusing does not occur. The objective lens actuator 19 has a function of moving the objective lens 12 in parallel with the vertical direction of the optical disc 3 (ie, the x-axis direction in the drawing) and the radial direction of the optical disc 3 (ie, the z-axis direction in the drawing). Other degrees of freedom are restricted. Further, the objective lens actuator 19 and the coarse movement actuator 20 are driven by a command from the outside of the apparatus and a track error signal to make the focus follow a predetermined recording track. The coarse movement actuator 20 has a function of translating the carriage 21 on which the raising mirror 11 and the objective lens actuator 19 are mounted in parallel in the radial direction of the optical disc 3, and restrains other degrees of freedom.

When the command from the outside of the device is the recording of information, the system controller 1 modulates the current supplied to the semiconductor laser 2 according to the information inputted from the outside, and the system controller 1 causes the recording film 13 of the optical disc 3 to be recorded. Record information. Here, since the configuration of the recording film 13 is not directly related to the essence of the present invention, it is assumed that the information recording is a phase change type optical disc in which information is recorded by changing the phase of the recording film 13. When the command is reproduction of information, the system controller 1 outputs the signal detected by the optical pickup 16 to the outside of the device.

The semiconductor laser 2, the collimating lens 5, the beam splitters 6, 14, the mirror 15, the lens 17, the photodetector 18, and the optical pickup 16 are fixed to the optical system base 23, and a spindle motor (not shown), The coarse movement actuator 20, the system controller 1, the lenses 7 and 10, and the aberration generators 8 and 9 are fixed to the base 22.

The normal optical disc 3 is, as shown in FIG.
The structure is such that the recording film 13 is provided on the transparent substrate 31, and light is condensed on the recording film 13 through the transparent substrate 31. Generally, spherical aberration occurs when light is condensed through a transparent parallel plate, but the thickness and refractive index of the transparent parallel plate are specified by standards, etc., and if known, correct with the objective lens 12. You can Further, the optical disc 3 is usually installed so as to be perpendicular to the optical axis of the objective lens 12. However, due to the deflection of the disc and the mounting error of the disc, an inclination as shown in FIG. 2 occurs, which causes aberration. If the disc mounting error is peculiar to the apparatus, it can be removed by adjustment, but if the optical disc 3 is used while being replaced, the tilt caused by the disc cannot be removed by adjustment. The present invention is characterized in that this is detected and corrected.

Consider a case where the thickness of the transparent substrate 31 is t and the refractive index is n, and the substrate 31 is inclined by θ with respect to the optical axis of the objective lens 12 as shown in FIG. Here, it is assumed that the tilt occurs around the tangential direction of the optical disc 3 (the same is true when the tilt occurs around the radial direction).

For convenience of explanation of the following embodiments, an unusual definition of aberration will be given. In FIG. 2, a principal plane of a lens used in an optical system, such as the principal plane 33 of the objective lens 12 on the optical disk 3 side is considered, and one point P is set on this principal plane. Next, for example, paraxial focusing point 3
Take the paraxial focus of the light passing through the lens, such as 4. FIG.
When the light passes through a transparent object and is condensed like
Consider a paraxial focusing point when there is no transparent object. Main plane 3
The paraxial ray passing through 3 passes through the substrate 31 and is condensed at the paraxial condensing point 32. However, for the definition of aberration, the paraxial condensing point 34 when the optical disc 3 is not present will be considered. Now consider a wavefront passing through a point P, such as the wavefront 35 in the figure.
Furthermore, a spherical surface 3 passing through the point P and centered on the paraxial focusing point 34
Consider a sphere such as 6 passing through the point P and centered on the paraxial focal point. Then, the intersection 37 of the wavefront 35 and the beam center
Then, considering the intersection of the beam center, the wavefront, and the sphere like the intersection 38 of the spherical surface 36 and the beam center, the optical path length ΔL of both is called the aberration at the point P. The aberration is defined as positive when the intersection of the wavefront and the beam center is farther than the intersection of the spherical surface and the beam center when viewed from the optical disc 3, as shown in FIG. If the paraxial focal point is at infinity, a plane that passes through the point of interest and is perpendicular to the beam propagation direction is used instead of the spherical surface.

First, the conditions for converging light on the recording film 13 of the optical disk inclined as shown in FIG. 2 are obtained. Therefore, an ideal point light source is placed at the paraxial focusing point 32, and a wavefront 35 passing through one point P on the main plane 33 among the wavefronts of the light emitted from the paraxial focusing point 32 is considered. When viewed from the outside of the optical disk, paraxial rays appear to be emitted from the paraxial condensing point 34. Therefore, consider a spherical surface 36 passing through the point P with the paraxial condensing point 34 as the center. Due to the optical path length between the intersection 37 between the wavefront 35 and the beam center and the intersection 38 between the spherical surface 36 and the beam center, the principal plane 3 of the light emitted from the paraxial focusing point 32
The aberration on 3 is required.

A coordinate system (x ₄ , y ₄ ) is set on the main plane 33. It is assumed that the origin of the coordinate system (x ₄ , y ₄ ) is the intersection of the main plane 33 and the center of the beam, the coordinate axis x ₄ is in the radial direction of the optical disc 3, and the coordinate axis y ₄ is in the tangential direction. If the coordinates of the point P are (x ₄ , y ₄ ), the focal length of the objective lens 12 is f, and θ is small, and a second or higher order amount of θ is ignored, the coma aberration ΔL (P) at the point P is It becomes like (Equation 1).

[0036]

[Equation 1]

Here, the focal length f of the objective lens 12 is defined as the distance between the paraxial focal point 34 and the main plane 33 when the optical disc 3 is not present. The same applies to the focal lengths of other lenses described below. Further, the astigmatism is a quadratic quantity with respect to θ and will be ignored. Since the propagation of light is reversible, the principal plane 33 of the light emitted from the semiconductor laser 2 of FIG.
By setting the above aberration to the value given by the above (Equation 1), the coma aberration generated by the tilt of the optical disc 3 can be canceled.

Next, the detection of the aberration caused by the tilt of the optical disc 3 will be described with reference to FIGS. It is assumed that the aberrations are not generated in the aberration generators 8 and 9 and that the light incident on the objective lens 12 from the semiconductor laser 2 side has no aberration.
Due to the tilt of the optical disc 3, the position of the paraxial focusing point 32 deviates from the optical axis of the objective lens 12. Due to this shift, the angle changes when the reflected light enters the objective lens 12 and causes aberration. The aberration due to this angle change is a second-order amount of the inclination θ and is ignored. Then, the coma aberration ΔL of the reflected light from the tilted optical disk 3 becomes as shown in (Equation 2) on the main plane 33.

[0039]

[Equation 2]

As shown in FIG. 3, a coordinate system (x ₃ , y ₃ ) is set on the light source side main plane 41 of the objective lens 12. The direction of the coordinate axis x ₃ is the same as the coordinate axis x _4, and the direction of the coordinate axis y ₃ is the same as the coordinate axis y _4, and the origin of the coordinate system (x ₃ , y ₃ ) is the beam center, and the coordinate system (x ₄ , y ₄ ) is The coordinate system (x ₃ , y ₃ ) has the same length. Then, the coma aberration ΔL of the reflected light from the optical disc 3 becomes as shown in (Equation 3) on the main plane 41.

[0041]

(Equation 3)

As shown in FIG. 4, the coordinate system (x ₉ , y ₉ ) is set on the main plane 43 of the lens 17 on the optical disk 3 side.
The direction of the coordinate axis x _{9 is the same as} the direction of the coordinate axis x ₃ projected by the mirror 11 and the direction of the coordinate axis y ₉ is the same as the coordinate axis y _3, and the origin of the coordinate system (x ₉ , y ₉ ) is the beam center, and the coordinate is The system (x ₃ , y ₃ ) and the coordinate system (x ₉ , y ₉ ) have the same length as a unit. Then, the coma aberration ΔL of the reflected light from the optical disc 3 becomes as shown in (Equation 4) on the main plane 43.

[0043]

(Equation 4)

As shown in FIG. 4, the photodetector 18 is composed of a hermetically sealed package 24 having a transparent glass window 26 and a split photodiode 25 incorporated therein. Further, as shown in FIG. 5, the divided photodiode 25 has four light receiving regions 44, 45, 46, 47, and independently detects the light incident on each of them. The detected light is converted into an electric current and output from the terminals 48, 49, 50 and 51. As shown in FIG. 5, the photodetector 18 is installed such that the center of the split photodiode 25 is located at the focal point 52 of the lens 17.

When the light incident on the lens 17 has no aberration, the focused spot on the split photodiode 25 becomes like the focal point 52 in FIG. 5, but the aberration as shown in (Equation 4) is generated. When the included light is incident on the lens 17, the focal spot has a shape like the focal spot 53 in FIG. In this case, the photocurrent obtained from the light receiving section 46 becomes large. When the tilt of the optical disk 3 occurs on the side opposite to that in FIG. 3, the photocurrent obtained from the light receiving section 44 becomes large, and when the tilt does not occur, the photocurrent obtained from the light receiving section 44 and the photocurrent obtained from the light receiving section 46. The photocurrents are equal. Therefore, the light receiving unit 44 and the light receiving unit 4
By taking the difference of the photocurrent obtained from 6,
It is possible to obtain the coma aberration caused by the inclination of the optical disc 3 around the tangential direction. Similarly, by taking the difference between the photocurrents obtained from the light receiving unit 45 and the light receiving unit 47, the coma aberration caused by the tilt of the optical disc 3 around the radial direction can be detected. When the aberration is detected by this method, it is difficult to separate the influence of the diffracted light by the groove and the influence of the aberration in the optical disc having the groove. In this case, the aberration may be detected by a grooveless mirror portion provided at several places during one rotation of the disk, and the aberration may be canceled by the sample servo.

The same thing can be done by using a position detecting element 27 as shown in FIG. 7 instead of the divided photodiode 25. This element has a function of detecting the position of the focal point 52. When the focus 52 is at the center of the position detecting element 27 as shown in the figure, the four terminals 48, 49, 5
The currents obtained from 0 and 51 are equal. When it is deviated from the center, the position of the defocused focus 52 is (x, y) in the coordinate system.
Then, the difference between the currents obtained from terminals 48 and 50 is proportional to x, and the difference between the currents obtained from terminals 49 and 51 is proportional to y. As shown in FIG. 7, the position detection element 27 is installed so that the focus 52 is located at the center of the position detection element 27 when light having no aberration is incident on the lens 17. In this case, the currents obtained from the four terminals 48, 49, 50, 51 are equal.

When the optical disk 3 is tilted in the direction shown in FIG.
The focal spot becomes like the focal spot 53 as shown in FIG. 8, and the center of the focal spot moves in the minus direction of x in the coordinate system of FIG. 8 and is obtained from the terminal 50 as in the case of using the split photodiode 25. The resulting current is greater than the current available at terminal 48. When the optical disk 3 is tilted in the direction opposite to that shown in FIG. 3, the current obtained from the terminal 48 becomes larger than the current obtained from the terminal 50, and the current obtained from the terminal 48 is the same as when the split photodiode 25 is used. By calculating the difference between the currents obtained from the terminal 50 and the terminal 50, the coma aberration caused by the inclination of the optical disc 3 around the tangential direction can be detected. Similarly, by taking the difference between the current obtained from the terminal 49 and the current obtained from the terminal 51, the coma aberration caused by the tilt of the optical disc 3 around the radial direction can be detected.

The aberration can be detected by installing an optical system as shown in FIG. 9 at the positions of the lens 17 and the photodetector 18. The light incident on the prism 58 is reflected by the reflecting surface 7.
It is divided by 5 and 76 and reflected. The respective reflected lights are condensed by the lenses 54 and 56, and the photodiodes 55 and 5
7 is detected. The incident angle when incident on the reflecting surfaces 75 and 76 is set equal to the critical angle of total reflection. Prism 58
When the light incident on the lens has no aberration, the reflectances of the reflecting surfaces 75 and 76 are equal, and the photodiodes 55 and 5 have the same reflectance.
The outputs of 7 are equal.

When the optical disk 3 is tilted in the direction of FIG. 3 and the light incident on the prism 58 has the coma aberration as shown in FIG. 9, the propagation direction of the beam corresponds to the wavefront distortion outside the beam as shown in FIG. It changes in the direction of the diagonal arrow inside. Then, with respect to the reflecting surface 75, the incident angle becomes small and total reflection does not occur, so that the reflectance is lowered and the photodiode 5
The output of 5 becomes small. Although the incident angle becomes large with respect to the reflecting surface 76, the incident angle becomes larger than the critical angle of total reflection, so the reflectance does not change and the output of the photodiode 57 does not change. When the optical disc 3 is tilted in the direction opposite to that shown in FIG. 3, the output of the photodiode 57 becomes small. Therefore, by taking the difference between the outputs of the photodiode 55 and the photodiode 57, the coma aberration caused by the tilt of the optical disc 3 around the tangential direction can be detected. This optical system cannot detect the coma aberration caused by the tilt of the optical disc 3 in the radial direction. By combining two optical systems as shown in FIG. 9, the coma aberration caused by the tilt in the radial direction is also detected. It becomes possible to detect.

Next, correction of aberration will be described with reference to FIGS. The optical disc 3 is rotated around the tangential direction in FIG.
It is assumed that an inclination due to the inclination is detected and an aberration due to the inclination is detected. FIG. 10 is an enlarged view of the aberration generator 8 of FIG. The aberration generator 8 includes a frame 77 and a rotation shaft 63 fixed to the frame 77.
And a glass plate 64 which is a transparent parallel flat plate rotatable around the rotation axis 63, and a coil 6 fixed to the glass plate 64.
1, 62 and magnetic circuits 59, 60 fixed to the frame 77. When current is applied to the coils 61 and 62,
Due to the interaction between the magnetic circuits 59 and 60, a force acts in a tangential direction with respect to the rotating shaft 63. The force acting on the coil 61 and the force acting on the coil 62 are wound such that their directions are opposite to each other.
Rotate around 3. The rotating shaft 63 is parallel to the x axis in FIG. 1, and the frame 77 is fixed to the base 22 in FIG. When the optical disk is tilted only around the tangential direction, the glass plate 64 is perpendicular to the optical axis as shown in FIG. Then, no coma aberration occurs at the glass plate 64 portion. In this case, spherical aberration occurs in the glass plate 64, but the spherical aberration generated in the glass plate 64 is corrected by the lens 7 and removed.

FIG. 12 is an enlarged view of the aberration correction unit 9. The aberration generator 9 includes a frame 65 and a rotating shaft 7 fixed to the frame 65.
0, a glass plate 71 which is a transparent parallel flat plate rotatable around a rotation axis 70, and a coil 6 fixed to the glass plate 71.
8 and 69, and magnetic circuits 66 and 67 fixed to the frame 65. When current is applied to the coils 68 and 69,
Due to the interaction of the magnetic circuits 66 and 67, a force acts in a tangential direction with respect to the rotating shaft 70. The force acting on the coil 68 and the force acting on the coil 69 are wound such that their directions are opposite to each other.
Rotate around 0. The rotating shaft 70 is parallel to the y-axis in FIG.

The glass plate 71 is rotated by θ _{2 in} the direction of FIG. 13 in accordance with the inclination of the optical disk 3. Lens 10
The coordinate system (x ₁ , y ₁ ) is set on the light source side main plane 72 of. Orientation of coordinate axis x ₁ raises coordinate axis x ₃ Mirror 1
The direction projected in 1 and the direction of the coordinate axis y ₁ coincide with the coordinate axis y _3, and the origin of the coordinate system (x ₁ , y ₁ ) is the beam center,
The coordinate system (x ₃ , y ₃ ) and the coordinate system (x ₁ , y ₁ ) have the same length as a unit. The focal length of the lens 10 is f ₂ , the glass plate 7
Assuming that the thickness of 1 is t ₂ and the refractive index is n ₂ , the coma aberration ΔL of the light passing through the glass plate 71 is as shown in (Equation 5) on the main plane 72.

[0053]

(Equation 5)

The coordinate system (x ₂ , y ₂ ) is set on the disk-side main plane 73 of the lens 10. The direction of the coordinate axis x ₂ is the same as the coordinate axis x _1, and the direction of the coordinate axis y ₁ is the same as the coordinate axis y ₂ .
The origin of the coordinate system (x ₂ , y ₂ ) is the beam center, and the coordinate system (x ₂ , y ₂ ) and the coordinate system (x ₁ , y ₁ ) have the same length as a unit. The coma aberration ΔL of the light passing through the glass plate 71 is as shown in (Equation 6) on the main plane 73.

[0055]

(Equation 6)

Spherical aberration is generated when passing through the glass plate 71, but the spherical aberration generated by the glass plate 71 is caused by the lens 10.
It has been corrected by and removed. FIG. 14 shows the shape of the wavefront before and after the rising mirror 11, and shows that the aberration on the main plane 73 and the aberration on the main plane 41 are equal.

FIG. 15 shows the wavefronts of the light passing through the aberration generators 8 and 9 near the principal planes 33 and 41. The coma aberration of the light passing through the aberration generators 8 and 9 on the principal plane 41 is as shown in (Equation 7).

[0058]

(Equation 7)

Further, the coma aberration of the light passing through the aberration generators 8 and 9 on the principal plane 33 is as shown in (Equation 8).

[0060]

(Equation 8)

Here, by comparing (Equation 1) and (Equation 8),
By performing the following (Equation 9), the optical disc 3
It is possible to cancel out the aberration generated due to the inclination of, and focus the light at the paraxial light focusing point 32.

[0062]

[Equation 9]

When the optical disc 3 is tilted by α around the radial direction, the glass plate 64 has a thickness t ₁ and a refractive index n ₁ , and the rotation angle of the glass plate 64 around the rotation axis 63 satisfies the following equation. The aberration can be canceled by inclining by θ ₁ .

[0064]

(Equation 10)

In particular, when the thickness and the refractive index of the glass plates 64 and 71 and the substrate 31 are made to coincide with each other, the glass plate 71 is tilted by the same angle as the tilt angle of the optical disc 3 about the tangential direction, and the optical disc 3 is rotated about the radial direction. The aberration can be canceled by inclining the glass plate 64 by the same angle as the inclination angle. In this case, the lenses 7 and 10 can be the same lenses as the objective lens 12. If the glass plates 64 and 71 are transparent parallel plates, the same operation can be performed with plastic plates. When a transparent parallel plate is used, the glass plates 64 and 71 do not rotate ideally in the aberration generators 8 and 9, and even if the glass plates 64 and 71 are moved in parallel due to manufacturing errors or the like, the operation is completely affected. Absent. This is one of the major characteristics of using a transparent parallel plate.

The system controller 1 performs feedback control from the output of the photodetector 18 so as to reduce the aberration on the optical disc 3, and the optical disc 3 is operated during the operation of the apparatus.
It is possible to stably record and reproduce the information even if the inclination of the.
When the apparatus does not have a command to record or reproduce information from the outside, the information on the optical disk 3 is reproduced on a trial basis while changing the gain and offset of feedback control.
By finding the optimum gain and offset values and resetting the gain and offset values of the feedback control to the optimum values during the operation of the apparatus, more stable recording and reproduction of information becomes possible.

Even if the aberration generators 8 and 9 are replaced with an aberration generator using a hologram element, the aberrations caused by the tilt of the optical disc 3 can be canceled. For example, the aberration generating unit 8 is the same as the aberration generating unit 82 shown in FIG.
Is replaced with the aberration generating unit 83 shown in FIG. here,
Aberration correction using a hologram will be described with reference to FIGS. 16 to 19. First, the principle of aberration generation using a hologram will be described. As shown in FIG. 16, the hologram element 81 is provided with the following diffraction grating.
Consider the curved surface given by the following equation in the coordinate system of FIG.

[0068]

[Equation 11]

Letting the wavelength of the light emitted from the semiconductor laser 2 be λ, consider the lines of intersection of this curved surface and the plane given by the following equation, and diffract these lines of intersection along the line projected on the surface of the hologram element 81. A grid is provided.

[0070]

(Equation 12)

As shown in FIG. 17, the hologram element 81
When light of wavelength λ enters perpendicularly to, the wavefront shape of the first-order diffracted light becomes the shape of the curved surface given by (Equation 11). here,
The beam diameter is D, and the position of the beam center is x = x ₀ . Then, in the vicinity of x = x ₀ , the wavefront shape is given by the following equation.

[0072]

(Equation 13)

If x ₀ is small, (Equation 13) can be approximated as follows.

[0074]

[Equation 14]

That is, the hologram element 8 for the beam
By moving the position 1 in the x-axis direction in FIG. 17, the coma aberration of the diffracted light in the x-axis direction changes. As shown in FIG. 18, the aberration generating section 82 is composed of a frame 84, piezoelectric elements 85 and 86, and a hologram element 81. Further, the hologram element 81 is the piezoelectric element 8
It is fixed to the frame 84 via 5,86. In the hologram element 81, the wave vector of the diffraction grating is parallel to the y-axis of FIG. 18, and the piezoelectric elements 85 and 86 move in parallel in the y-axis direction of FIG. 18 to change the coma of the first-order diffracted light. .

As shown in FIG. 19, the aberration generating portion 83 is composed of a frame 87, piezoelectric elements 88 and 89, and a hologram element 81. Also, the hologram element 81
Are fixed to the frame 87 via piezoelectric elements 88 and 89. In the hologram element 81, the wave vector of the diffraction grating is parallel to the x-axis of FIG. 19, and the piezoelectric elements 88 and 89 move the translation parallel to the x-axis direction of FIG.
The coma of the second-order diffracted light changes.

The aberration generators 82, so that the coordinate axes of the coordinate system xyz of FIGS. 18 and 19 and the coordinate system xyz of FIG.
83 is fixed to the base 22 instead of the aberration generating units 8 and 9, the aberration generating unit 83 is operated with respect to the tilt of the optical disc 3 around the tangential direction, and the aberration generating unit 82 is operated with respect to the tilt around the radial direction. The aberration caused by the tilt can be canceled by operating the.

Aberrations can be canceled even with the configuration shown in FIG. Electro-optic crystals 90 and 91 such as LiNbO ₃ , BaTiO ₃ , and ZnO are arranged between the lenses 7 and 10 in FIG. The electro-optic crystals 90 and 91 have the same thickness and refractive index, and are inclined in the opposite directions with respect to the optical axis by an angle α. The electro-optic crystal 91 is further provided with transparent electrodes 92 and 93 so that the refractive index changes when an electric field is applied from the system controller 1. When no electric field is applied to the electro-optic crystal 91, the aberration generated in the electro-optic crystal 90 and the aberration generated in the electro-optic crystal 91 cancel each other out, and the coma aberration of the light transmitted through the electro-optic crystals 90, 91 is canceled. Is 0. Assuming that the refractive index of the electro-optic crystal when no electric field is applied is n _e , the refractive index when an electric field is applied is n _e ′, and the thickness is t _e , the coma aberration ΔL on the main plane 72 is , The following (Equation 1
5).

[0079]

(Equation 15)

The spherical aberrations generated in the electro-optic crystals 90 and 91 are corrected and removed by the lenses 7 and 9. With the configuration shown in FIG. 20, the coma aberration that occurs when the optical disc 3 tilts around the tangential direction can be canceled, but the coma aberration that occurs when tilting around the radial direction cannot cancel. In FIG. 20, the electro-optic crystals 90 and 91 are tilted around the y-axis in the figure, but another set of similar electro-optic crystals is prepared and this is tilted in the same manner around the x-axis in the figure. It is also possible to cancel coma aberration that occurs when tilted in the radial direction. When two electro-optic crystals are used in combination as shown in FIG. 20, the influence of a change in the refractive index due to a change in temperature and the like cancels each other out, and stable operation becomes possible. Further, instead of the electro-optic crystal, a crystal having a piezoelectric effect is used, and in addition to the change in the refractive index,
The same can be done by using a change in the crystal thickness.
The same thing can be achieved by electrically changing the refractive index of the liquid crystal instead of the electro-optic crystal.

In FIG. 20, the transparent electrodes 92, 93 are provided only on the electro-optic crystal 91 side to apply an electric field, but in reality, the transparent electrodes 92, 93 are also provided on the electro-optic crystal 90 side. 93 is provided and configured to apply an electric field.

(Second Embodiment) Next, a second embodiment of the present invention will be described with reference to FIGS. 21 to 29. This embodiment relates to a method of assembling an optical disk device. 21 is an explanatory view of the optical system of the optical disk device, and FIG.
2 is an enlarged view of FIG. 2, FIG. 23 is an enlarged view of the aberration generating unit 103, and FIG.
4 is an explanatory view of another assembling method, FIGS. 25 and 26 are enlarged views for explaining the operation of the aberration generating unit 101, and FIGS. 27, 28 and 29 are explanatory views showing the principle of aberration cancellation.

When a command for recording or reproducing information is input to the optical disc device from the outside of the system controller 1 of FIG. 21, the system controller 1 supplies a current to the spindle motor 105 and the optical disc fixed to the clamp 106. Rotate 107. Further, the system controller 1 also supplies a current to the semiconductor laser 2 to turn on the semiconductor laser 2.

The light emitted from the semiconductor laser 2 passes through the aberration generators 101, 102 and 103, becomes parallel light by the collimator lens 104, and is reflected by the rising mirror 11. The reflected light is condensed by the objective lens 12 and condensed on the recording film 109 of the optical disc 107. This light is reflected by the recording film 109, becomes parallel light by the objective lens 12, is reflected again by the rising mirror 11, and enters the beam splitter 6. A part of this light is reflected by the beam splitter 6, further reflected by the mirror 15, and enters the optical pickup 16.

The optical pickup 16 is the optical disc 107.
It has a function of detecting the information recorded above, a function of detecting a focus error indicating a focus defocus of the objective lens 12 in the recording film 109, and a concentric or spiral shape provided on the optical disc 4. It has a function of detecting a track error, which is a row of recording pits and indicates a deviation of the focus from the recording track.

The system controller 1 drives the objective lens actuator 19 according to the focus error signal detected by the optical pickup 16 and controls the focus so that defocusing does not occur. The objective lens actuator 19 has a function of translating the objective lens 12 in the vertical direction of the optical disc 107 (that is, the x-axis direction in the drawing) and in the radial direction of the optical disc 107 (that is, the z-axis direction in the drawing). Restrains the degree of freedom of. Further, the objective lens actuator 19 and the coarse movement actuator 20 are driven by a command from the outside of the apparatus and a track error signal to make the focus follow a predetermined recording track. The coarse movement actuator 20 has a function of translating the carriage 21 on which the raising mirror 11 and the objective lens actuator 19 are mounted in parallel in the radial direction of the optical disc 107, and further restricts other degrees of freedom.

When the command from the outside of the apparatus is the recording of information, the system controller 1 modulates the current supplied to the semiconductor laser 2 according to the information input from the outside, and records the information on the optical disc 107. To do. here,
Since the structure of the recording film 109 is not directly related to the essence of the present invention, it is assumed that the information recording is a phase change type optical disc in which information is recorded by changing the phase of the recording film 109. When the command is reproduction of information, the system controller 1 outputs the signal detected by the optical pickup 16 to the outside of the device.

Semiconductor laser 2 and collimating lens 10
4, the beam splitter 6, the mirror 15, the optical pickup 16, and the aberration generators 101, 102 and 103 are fixed to the optical system base 114, and the spindle motor 1
05, actuator 20, system controller 1,
The optical system base 114 is fixed to the base 115.

The optical disc 107 has a structure in which a recording film 109 is provided on a transparent substrate 110, and light is emitted from the substrate 1
It is focused on the recording film 109 through 10. Then, spherical aberration occurs when passing through the substrate 110. Since the thickness and the refractive index of the substrate of the optical disc 107 are usually defined by the standard or the like, this spherical aberration is caused by the objective lens 12.
It can be corrected and removed with. However, when optical discs with substrates having different thicknesses and refractive indexes are mounted, the aberration cannot be canceled out, and it becomes difficult to record / reproduce information. In this embodiment, the aberration generator 101, which will be described in detail later,
As a result, this spherical aberration is canceled out, and information can be recorded / reproduced even when optical disks of substrates having different thicknesses and refractive indexes are mounted. The optical disk device shown in FIG. 21 has the functions as described above, but this embodiment relates to a method for assembling this optical disk device.

If the light applied to the optical disk 107 has an aberration, the focal spot spreads, making it difficult to record and reproduce information. Therefore, it is necessary to adjust the optical system so that the aberration does not occur. In particular, the optical axis of the objective lens 12 needs to match the optical axis of the light reflected by the rising mirror 11. For this reason, the conventional optical disk device has an adjusting mechanism for adjusting the inclination of the objective lens. In this embodiment, the adjustment is performed as follows.

First, a dummy disk having the same thickness and refractive index as the substrate 110 and having no recording film is fixed to the clamp 106. At this time, the aberration generating unit 101 generates an aberration so that the substrate can be read.
Then, the semiconductor laser 2 is turned on. Then, the light passes through the dummy disk fixed to the clamp 106. This light is made incident on the focal spot measuring device 108,
Measure the focal spot. The aberration generators 102 and 103 are adjusted so that the size of the focal spot is minimized.
As shown in FIG. 21, when the objective lens 12 is tilted by θ, astigmatism and coma occur as aberrations that pose a problem in the optical disc device. Since the astigmatism is a quadratic amount with respect to the inclination θ, it can be ignored when the mounting error is small. The coma aberration is adjusted by the aberration generator 102,
At 103. The configurations of the aberration generators 102 and 103 will be described later.

By thus mounting the adjusting mechanism on the fixed part instead of mounting it on the movable part, the movable part can be made lighter in weight, so that a predetermined recording track can be accessed at high speed. Further, the structure around the actuator 19 can be simplified. This adjustment can correct not only the tilt of the objective lens 12 but also the aberration caused by the tilt of the optical disk 107 due to the mounting error of other optical components, the mounting error of the spindle motor 105, and the like.

A wavefront analyzer is used instead of the focal spot measuring device 108 to measure the wavefront of the light transmitted through the dummy disk, and the aberration generator 102, so that the aberration of the transmitted light becomes a minimum or a predetermined value. Adjustment of 103 may be performed. When the wavefront analyzer is used, it is possible to remove the dummy disk and adjust the aberration by estimating the aberration generated in the dummy disk in advance.

Further, instead of the dummy disc, a disc on which predetermined information is recorded is mounted, the semiconductor laser 2 is turned on, and the optical pickup 16 reads out a record from the disc or detects a focus error signal or a track error signal. I do. In this state, the read signal, the focus error signal, or the track error signal is measured, and the aberration generating unit 10 is set so that these signals become the best.
Adjustment of 2, 103 may be performed.

FIG. 22 is an enlarged view of the aberration generating section 102, and xyz in FIG. 21 and the coordinate system xyz in FIG. 22 are oriented in the same direction. The aberration generating unit 102 is the optical system base 1
14, a protrusion 111, a knife edge 112,
The glass plate 113 is a transparent parallel plate. The glass plate 113 is placed on the knife edge 112, and the angle around the y axis in the figure can be adjusted. Aberration is adjusted by adjusting the angle around the y-axis. By adjusting the aberration generator 102, the objective lens 12
It is possible to adjust the coma aberration that occurs when is tilted around the y-axis in FIG. Adjust the angle of the glass plate 113,
When the adjustment is completed, the glass plate 113 and the protrusion 111 are fixed with an adhesive.

The coordinate system (x ₅ , y ₅ ) is set on the principal plane of the collimator lens 104 on the light source side. The direction of the x ₅ axis is aligned with the x axis direction of FIG. 21, and the direction of the y ₅ axis is the y axis of FIG.
The axis should be aligned with the center of the beam at the origin.
Then, the focal length of the collimating lens 104 is f ₁ , the thickness of the glass plate 113 is t ₁ , the refractive index is n ₁ , and the glass plate 11 is
Assuming that the inclination of 3 with respect to the optical axis is θ ₁ , the aberration generating unit 102
The aberration .DELTA.L generated in (1) is as shown in (Equation 16) on the light source side main plane of the collimator lens 104.

[0097]

(Equation 16)

When the same coma aberration is generated, for example, t
_{If 1} is small, θ ₁ will be large. That is, the angle adjustment need only be rough and the adjustment becomes easy. Also, adjust
Even if a displacement occurs due to some reason after the bonding is completed, the influence can be reduced. The same thing occurs when the value is close to n ₁ or f ₁ is large. Since the glass plate 113 is a parallel plate, parallel movement other than tilt does not affect aberrations, and adjustment is easy in this respect as well.

FIG. 23 is an enlarged view of the aberration generator 103, and xyz in FIG. 21 and the coordinate system xyz in FIG. 23 have the same direction. The aberration generating unit 103 is the optical system base 1
14 is provided with a knife edge 116 and a glass plate 117 which is a transparent parallel plate. The glass plate 117 is placed on the knife edge 116, and the angle around the x axis in the drawing can be adjusted. Aberration is adjusted by adjusting the angle around the x-axis. By adjusting the aberration generating unit 103, it is possible to adjust the coma aberration that occurs when the objective lens 12 is tilted around the x axis in FIG. The angle of the glass plate 117 is adjusted, and when the adjustment is completed, the glass plate 117 and the optical system base 114 are fixed with an adhesive.

As in the case of the aberration generating section 102, the angle is adjusted by reducing the thickness of the glass plate, making the refractive index closer to 1, or increasing the focal length of the collimating lens 104. Will be coarse and easy to adjust. In addition, even if a misalignment occurs for some reason after the adjustment and the bonding are completed, the influence can be reduced. The glass plates 113, 1
The spherical aberration generated at 17 will be described later.

21 to 23, the aberration generators 102, 10 are provided between the semiconductor laser 2 and the collimator lens 104.
3 was provided, but as shown in FIG.
The light emitted from the collimator lens 104 is collimated and collimated by the lens 118, and the aberration generator 102,
If the lens 119 collimates again after passing through 103, the degree of freedom in lens design and optical system design can be increased. Also, the aberration generator 102,
The same can be achieved by using 103 as the aberration generating unit using the hologram described with reference to FIGS. 16 to 19 and the aberration generating unit using the electro-optic crystal described with reference to FIG.

Next, the spherical aberration generated by the aberration generating sections 102 and 103, and the aberration generating section 1 capable of recording / reproducing information on / from the optical disc having the substrate having different thickness and refractive index.
01 will be described. First, the aberration when the converging light or the diverging light passes through a transparent parallel plate is calculated. FIG.
In the same way as we thought about coma using
A condition for canceling the spherical aberration generated in 10 will be obtained. FIG.
As shown in FIG. 5, consider a case where paraxial rays that have passed through the objective lens 12 are condensed on the recording film 120. Furthermore, consider the paraxial focusing point 121 when the optical disk 107 is not present. Thus, an ideal point light source is placed at the paraxial focusing point 120, and the aberration ΔL of the light emitted from this point on the disk-side main plane 122 of the objective lens 12 is obtained.

As shown in FIG. 25, the coordinate system (x ₈ , y ₈ ) is set on the main plane 122. The direction of the x ₈ axis is made to coincide with the direction projected by the rising mirror 11 on the x ₅ axis, the direction of the y ₈ axis is made to coincide with the y ₅ axis, and the center of the beam is taken as the origin. Further, the coordinate systems (x ₈ , y ₈ ) and (x ₅ , y ₅ ) have the same length as a unit. Then, ΔL is given by the following (Equation 17), where n is the refractive index of the substrate, t is the thickness, and f is the focal length of the objective lens 12.

[0104]

[Equation 17]

From the reversibility of light propagation, by setting the aberration on the principal plane 122 to the value given by (Equation 17),
The aberration generated on the substrate 110 can be canceled.
For convenience of explanation, consider a case where information is recorded / reproduced on / from two types of optical disks having the same substrate refractive index and different thicknesses. The principle is exactly the same when the refractive index is different, when both the refractive index and the thickness are different, and when information is recorded and reproduced on three or more types of optical disks. It is assumed that the thicknesses of the two types of substrates are t and T, respectively, and T> t. The objective lens 12 imparts spherical aberration to the light so that when the aberration-free light enters the objective lens 12 from the rising mirror 11, the light is properly focused on the recording film of the optical disc of the substrate having the thickness T. It is like this. That is, when aberration-free light enters the objective lens 12 from the rising mirror 11, the aberration on the principal plane 122 has a value given by (Equation 17).

FIG. 26 is an enlarged view of the aberration generating portion 101, showing a state when information is recorded / reproduced on / from an optical disc having a substrate thickness T. Also, the coordinate system xyz in the figure
The axes coincide with the xyz axes of the coordinate system in FIG. The aberration generator 101 includes a glass substrate 123, coils 124 and 125 attached to the glass substrate 123, and magnetic circuits 126 and 12.
7 is comprised. When a current is passed through the coils 124 and 125, a force is exerted by the interaction with the magnetic circuits 126 and 127 to move the glass plate 123 in the y-axis direction in FIG. The state of FIG. 26 is a state in which the light has moved in the positive direction of the y-axis, and the light does not pass through the glass plate 123 and the aberration generating unit 102
It passes through 103 and enters the collimating lens 104. The collimator lens 104 has a function of correcting spherical aberration generated in the glass plates 113 and 117 to make parallel light without aberration. Of course, if the light emitted from the semiconductor laser 2 has spherical aberration, this is also corrected. The spherical aberration generated in the glass plates 113 and 117 and the spherical aberration of the collimator lens 104 for correcting the spherical aberration are not related to the recording / reproducing of information on the optical discs of a plurality of types of substrates, and will be ignored hereinafter.

When the light does not pass through the glass plate 123 of the aberration corrector 101, the light collimated by the collimator lens 104 has no aberration. Therefore, in this case, information can be recorded / reproduced on / from the optical disc having the substrate thickness T. FIG. 27 schematically shows the state of aberration in this case. In this figure, the light source side main plane 130 of the collimator lens 104, the disc side main plane 128, the light source side main plane 129 of the objective lens 12, and the disc side main plane 122.
The state of the aberration above is shown. Glass plate 113,1
The spherical aberration generated at 17 and the spherical aberration of the collimator lens 104 for correcting the spherical aberration are excluded. Then
The light has no aberration on the main planes 130, 128, and 129, and the aberration on the main plane 122 has a value given by (Equation 17), and recording / reproduction of information from / to an optical disc having a substrate of thickness T is performed. Is possible.

FIG. 28 is an enlarged view of the aberration generating section 101, showing a state in which information is recorded / reproduced on / from an optical disc having a substrate thickness t. Also, the coordinate system xyz in the figure
The axes coincide with the xyz axes of the coordinate system in FIG. The state of FIG. 28 is a state in which the light has moved in the negative direction of the y-axis, and the light passes through the glass plate 123, further passes through the aberration generators 102 and 103, and enters the collimator lens 104. Glass plate 12
The refractive index of ₃ is n ₃ , the thickness is t ₃ , and the collimating lens 104
Assuming that the focal length of f is f ₁ , the aberration ΔL of this light on the principal plane 130 is as in the following (Equation 18).

[0109]

(Equation 18)

The coordinate system (x ₇ , y ₇ ) is set on the main plane 129. Coordinate axis x ₇ and coordinate axis x ₈ , coordinate axis y ₇ and coordinate axis y ₈
Have the same direction, and the coordinate systems (x ₇ , y ₇ ) and (x ₈ ,
y ₈ ) has the same length as a unit. The coordinate origin of the coordinate system (x ₇ , y ₇ ) is the center of the beam. Then, the aberration on the main plane 129 becomes as shown in (Formula 19) below.

[0111]

[Equation 19]

Then, the spherical aberration of the objective lens is added to the aberration on the principal plane 122, and the aberration is as shown in the following (Equation 20).

[0113]

(Equation 20)

From (Equation 20), by selecting n ₃ , t ₃ and f ₃ so as to satisfy the following equation, it becomes possible to read information from the optical disc having the substrate pressure t.

[0115]

(Equation 21)

The aberration generating unit 101 is the same as the aberration generating unit using the hologram described with reference to FIGS. 16 to 19 and FIG.
The same thing can be done as an aberration generating section using the electro-optic crystal described using.

Although the so-called optical information recording apparatus using the optical disk has been described in the above-mentioned first and second embodiments, the present invention is not limited to aberrations in general optical apparatuses such as telescopes and microscopes. Of course, it can also be applied to reduce

[0118]

As described above, according to the present invention,
Aberrations caused by the tilt of the objective lens or the optical disc can be directly detected, and the aberrations can be corrected without complicating the structure around the objective lens. In particular, it becomes possible to reduce aberrations when using a high NA objective lens.

Further, since it is not necessary to adjust the optical parts with high precision, the assembly of the optical device can be facilitated. Further, it is possible to realize an optical disk device capable of recording and reproducing information on optical disks having various substrate thicknesses.

[Brief description of drawings]

FIG. 1 is an explanatory diagram of an optical system of an optical disc device.

FIG. 2 is an explanatory diagram of an operation principle.

FIG. 3 is an explanatory diagram of an aberration generation principle.

FIG. 4 is an enlarged view of an aberration detector.

FIG. 5 is a plan view of a photodetector.

FIG. 6 is a plan view of a photodetector.

FIG. 7 is a plan view of a position detection element.

FIG. 8 is a plan view of a position detection element.

FIG. 9 is an explanatory diagram of an aberration detection method.

FIG. 10 is an enlarged view of an aberration generating unit.

FIG. 11 is an explanatory diagram of an aberration generating unit.

FIG. 12 is an enlarged view of an aberration generating unit.

FIG. 13 is an operation of the aberration generating unit.

FIG. 14 is an enlarged view of a rising mirror.

FIG. 15 is an explanatory diagram of aberration cancellation.

FIG. 16 is an explanatory diagram of a hologram.

FIG. 17 is an explanatory diagram of wavefront conversion.

FIG. 18 is an enlarged view of an aberration generating section.

FIG. 19 is an enlarged view of an aberration generating section.

FIG. 20 is an explanatory diagram of an aberration generating unit that uses an electro-optic crystal.

FIG. 21 is an explanatory diagram of an optical system of an optical disc device.

FIG. 22 is an enlarged view of an aberration generating section.

FIG. 23 is an enlarged view of an aberration generating section.

FIG. 24 is an explanatory diagram of an aberration generating unit.

FIG. 25 is an explanatory diagram of an operation principle.

FIG. 26 is an enlarged view of an aberration generating section.

FIG. 27 is an explanatory diagram of an operation principle.

FIG. 28 is an enlarged view of an aberration generating section.

FIG. 29 is an explanatory diagram of an operation principle.

[Explanation of symbols]

 1 System Controller 2 Semiconductor Laser 3 Optical Disc 4 Rotation Axis 5 Collimating Lens 6 Beam Splitter 7,10,17 Lens 8,9 Aberration Generation Part 11 Start-up Mirror 12 Objective Lens 13 Recording Film 14 Beam Splitter 15 Mirror 16 Optical Pickup 18 Optical Detection 19 Objective Lens Actuator 20 Coarse Movement Actuator 21 Carriage 22 Base 23 Optical System Base 24 Sealed Package 25 Split Photodiode 26 Glass Window 27 Position Detection Element 31 Substrate 32 Paraxial Focus Point 33 Main Plane of Optical Disc 3 Side of Objective Lens 12 34 Paraxial point 35 Wavefront passing through point P 36 Spherical point passing through point P and centering on paraxial point 34 37 Intersection between wavefront 35 and beam center 38 Intersection between spherical surface 36 and beam 41 41 Light source of objective lens 12 Side principal plane 3 Optical disc 3 side main plane of lens 17 Main plane 44, 45, 46, 47 Light receiving area 48, 49, 50, 51 Terminal 52 Lens 17 focus 53 Focus spot 54 Lens 55 Photodiode 56 Lens 57 Photodiode 58 Prism 59, 60, 66, 67 Magnetic circuit 61, 62, 68, 69 Coil 63, 70 Rotating shaft 64, 71 Glass plate 65, 77 Frame 72 Main surface of light source side of lens 73 Main disk side surface of lens 10 75, 76 Reflective surface Reference Signs List 81 hologram element 82, 83 aberration generating section 84, 87 frame 85, 86, 88, 89 piezo piezoelectric element 90, 91 electro-optic crystal 92, 93 transparent electrode 101, 102, 103 aberration generating section 104 collimator lens 105 spindle motor 106 clamp 107 optical disk 108 focus Spot measuring device 109 Recording film 110 Substrate 111 Protrusion 112,116 Knife edge 113,117 Glass plate 114 Optical system base 115 Base 118,119 Lens 120 Paraxial focusing point 121 Paraxial focusing point 122 Disk side of the objective lens 12 Main Plane 123 Glass substrate 124,125 Coil 126,127 Magnetic circuit 128 Disc-side main plane of collimating lens 104 129 Light source-side main plane of objective lens 130 Light source-side main plane of collimating lens 104

Claims (38)

[Claims] 1. An information recording medium capable of reproducing or recording / reproducing information by optical means, a light source, and a lens element for condensing light emitted from the light source to irradiate the information recording medium. Information detecting means for reproducing information recorded on the information recording medium from reflected light, transmitted light or scattered light of the light irradiated by the lens element, and reflected light of the light irradiated by the lens element, transmitted Based on light or scattered light, position detecting means for detecting the position of the condensing point of the lens element on the information recording medium, moving means for moving the lens element, and output from the position detecting means. An optical information recording apparatus comprising: a control unit that drives the moving unit to control the position of a focal point on the information recording medium. A parallel plate that generates a difference is provided in the middle of the optical path from the light source to the information recording medium, and the aberration that occurs in the lens element and the substrate portion of the information recording medium is canceled by the aberration that occurs in the parallel plate. An optical information recording device characterized by: 2. An information recording medium capable of reproducing or recording / reproducing information by optical means, a light source, and a lens element for condensing light emitted from the light source and irradiating the information recording medium. Information detecting means for reproducing information recorded on the information recording medium from reflected light, transmitted light or scattered light of the light irradiated by the lens element, and reflected light of the light irradiated by the lens element, transmitted Based on light or scattered light, position detecting means for detecting the position of the condensing point of the lens element on the information recording medium, moving means for moving the lens element, and output from the position detecting means. In an optical information recording device comprising: a control unit that drives the moving unit to control the position of a focal point on the information recording medium; A hologram element whose aberration is changed is provided in the optical path from the light source to the information recording medium, and the aberration generated in the lens element and the substrate portion of the information recording medium is canceled by the aberration generated in the hologram element. An optical information recording device characterized by: 3. An information recording medium capable of reproducing or recording and reproducing information by optical means, a light source, and a lens element for condensing light emitted from the light source and irradiating the information recording medium. Information detecting means for reproducing information recorded on the information recording medium from reflected light, transmitted light or scattered light of the light irradiated by the lens element, and reflected light of the light irradiated by the lens element, transmitted Based on light or scattered light, position detecting means for detecting the position of the condensing point of the lens element on the information recording medium, moving means for moving the lens element, and output from the position detecting means. In the optical information recording apparatus, which comprises a control unit that drives the moving unit to control the position of the condensing point on the information recording medium, a charge, current, voltage or electric field is applied. Electro-optical crystal for generating an aberration, a piezoelectric crystal or a liquid crystal element, provided in the middle of the optical path to the information recording medium from said light source,
An optical information recording device, characterized in that aberrations generated in the lens element and the substrate portion of the information recording medium are canceled by aberrations generated in the electro-optic crystal, piezoelectric crystal or liquid crystal element. 4. An information recording medium capable of reproducing or recording / reproducing information by optical means, a light source, and a lens element for condensing light emitted from the light source and irradiating the information recording medium. Information detecting means for reproducing information recorded on the information recording medium from reflected light, transmitted light or scattered light of the light irradiated by the lens element, and reflected light of the light irradiated by the lens element, transmitted Based on light or scattered light, position detecting means for detecting the position of the condensing point of the lens element on the information recording medium, moving means for moving the lens element, and output from the position detecting means. An optical information recording apparatus comprising: a control unit that drives the moving unit to control a position of a condensing point on the information recording medium, in an optical path from the light source to the information recording medium. A parallel plate that is provided inside and generates an aberration due to an inclination with respect to the irradiation light from a light source, an actuator that changes the inclination of the parallel plate, and a reflected light of the light irradiated on the information recording medium by the lens element, and a transmission. Aberration detecting means for detecting the aberration generated on the lens element and the information recording medium from light or scattered light, and controlling the drive of the actuator so that the aberration detected by the aberration detecting means is minimized. An optical information recording apparatus comprising: an actuator control unit. 5. An information recording medium capable of reproducing or recording / reproducing information by optical means, a light source, and a lens element for condensing light emitted from the light source and irradiating the information recording medium. Information detecting means for reproducing information recorded on the information recording medium from reflected light, transmitted light or scattered light of the light irradiated by the lens element, and reflected light of the light irradiated by the lens element, transmitted Based on light or scattered light, position detecting means for detecting the position of the condensing point of the lens element on the information recording medium, moving means for moving the lens element, and output from the position detecting means. An optical information recording apparatus comprising: a control unit that drives the moving unit to control a position of a condensing point on the information recording medium, in an optical path from the light source to the information recording medium. A hologram element that is provided inside, in which the aberration of the diffracted light changes depending on the tilt or the position where the light strikes, an actuator that changes the tilt or the position of the hologram element, and the light irradiated onto the information recording medium by the lens element Aberration detecting means for detecting the aberration generated on the lens element and the information recording medium from the reflected light, the transmitted light or the scattered light, and the actuator for minimizing the aberration detected by the aberration detecting means. An optical information recording apparatus, comprising: an actuator control unit that controls driving. 6. An information recording medium capable of reproducing or recording / reproducing information by optical means, a light source, and a lens element for collecting light emitted from the light source and irradiating the information recording medium. Information detecting means for reproducing information recorded on the information recording medium from reflected light, transmitted light or scattered light of the light irradiated by the lens element, and reflected light of the light irradiated by the lens element, transmitted Based on light or scattered light, position detecting means for detecting the position of the condensing point of the lens element on the information recording medium, moving means for moving the lens element, and output from the position detecting means. An optical information recording apparatus comprising: a control unit that drives the moving unit to control a position of a condensing point on the information recording medium, in an optical path from the light source to the information recording medium. An electro-optical crystal, a piezoelectric crystal, or a liquid crystal element, which is provided inside and generates an aberration upon application of electric charge, current, voltage, or electric field, and reflected light, transmitted light, or reflected light of the light irradiated on the information recording medium by the lens element. Aberration detecting means for detecting the aberration generated on the lens element and the information recording medium from scattered light, and the electro-optic crystal, piezoelectric crystal or liquid crystal so that the aberration detected by the aberration detecting means is minimized. An optical information recording apparatus comprising: an adjusting unit that adjusts a charge, a current, a voltage, or an electric field applied to an element. 7. The optical information recording device according to claim 1 or 4, wherein the parallel plates are transparent, and two parallel plates are provided in the middle of the optical path, and the two parallel plates are oriented substantially at right angles to each other. An optical information recording device, which is tiltable around a predetermined axis. 8. The optical information recording device according to claim 1, wherein the parallel plate is transparent and one plate is provided in the middle of the optical path, and the parallel plate is tiltable in any direction. A characteristic optical information recording device. 9. The optical information recording device according to claim 1, wherein the thickness and the refractive index of the parallel plate are substantially the same as the thickness and the refractive index of the substrate portion of the information recording medium. Optical recording device. 10. The optical information recording device according to claim 1, wherein the numerical aperture of convergent or divergent light on the parallel plate is
An optical information recording device having the same numerical aperture as that of light when condensed by the lens element. 11. The optical information recording device according to claim 1, wherein the parallel plate is arranged in an optical path where the light from the light source converges or diverges. A characteristic optical information recording device. 12. The optical information recording device according to claim 4, 5 or 6, wherein the aberration detecting unit is a reflection light from the information recording medium,
Detecting with the plurality of light-receiving surfaces, the light-collecting means collects transmitted light or scattered light, and a photodetector provided at the focal plane of the light-collecting means and having a plurality of light-receiving surfaces. An optical information recording device characterized by detecting an aberration from a differential signal of the generated light. 13. The optical information recording device according to claim 4, 5 or 6, wherein the aberration detecting unit is a reflection light from the information recording medium,
The photodetector is provided with a condensing means for condensing transmitted light or scattered light, and a photodetector provided at a position of a focal plane of the condensing means and having a function of detecting a position irradiated with light. An optical information recording device characterized by detecting an aberration from the output of the optical information recording device. 14. The optical information recording apparatus according to claim 4, 5 or 6, wherein the aberration detecting means is a reflection light from the information recording medium,
The transmitted light or scattered light is deflected in different directions on different wavefronts to split the light, and the intensity of the deflected light changes depending on the direction of the wavefront, and the split light is detected independently. An optical information recording apparatus, comprising: a photodetector for detecting aberrations from the output of the photodetector. 15. The optical information recording apparatus according to claim 4, 5 or 6, wherein said aberration detecting means includes said lens element and said information recording when there is no command to record or reproduce information from outside the apparatus. An optical information recording device characterized by detecting an aberration generated on a medium. 16. An information recording medium having a transparent substrate having a substantially parallel plate shape, capable of reproducing or recording / reproducing information by optical means, and further removable from an apparatus, and a light source. Recording on the information recording medium from a lens element that collects light emitted from the light source and irradiates the information recording medium, and reflected light, transmitted light, or scattered light of the light emitted by the lens element A position for detecting the position of the focal point of the lens element on the information recording medium from the information retrieval means for reproducing the recorded information and the reflected light, the transmitted light or the scattered light of the light emitted by the lens element. A detection means, a movement means for moving the lens element, and a control means for driving the movement means based on the output from the position detection means to control the position of the focal point on the information recording medium, In an optical information recording device including: an optical path from the light source to the information recording medium, which corresponds to a difference in the thickness or the refractive index of the substrate of the information recording medium mounted in the optical information recording device. An optical information recording device, characterized in that a transparent parallel plate is inserted into and removed from the lens, and the aberration generated in the lens element and the substrate is canceled by the aberration generated in the parallel plate. 17. An information recording medium having a transparent substrate having a substantially parallel plate shape, capable of reproducing or recording / reproducing information by optical means, and further attachable / detachable to / from the device, and a light source. Recording on the information recording medium from a lens element that collects light emitted from the light source and irradiates the information recording medium, and reflected light, transmitted light, or scattered light of the light emitted by the lens element A position for detecting the position of the focal point of the lens element on the information recording medium from the information retrieval means for reproducing the recorded information and the reflected light, the transmitted light or the scattered light of the light emitted by the lens element. A detection means, a movement means for moving the lens element, and a control means for driving the movement means based on the output from the position detection means to control the position of the focal point on the information recording medium, In an optical information recording device including, in the middle of the optical path from the light source to the information recording medium, an electro-optical crystal, a piezoelectric crystal or a liquid crystal element that generates aberration by application of electric charge, current, voltage or electric field is provided, and Corresponding to the difference in the thickness or the refractive index of the substrate of the information recording medium mounted in the information recording device,
By changing the electric charge, current, voltage or electric field applied to the electro-optical crystal, piezoelectric crystal or liquid crystal element, the aberration generated in the lens element and the substrate portion is generated in the electro-optical crystal, piezoelectric crystal or liquid crystal element. An optical information recording device characterized by canceling out by an aberration. 18. An optical device having a light source and an optical system for irradiating a predetermined object with the light emitted from the light source, wherein the parallel plate that generates an aberration due to an inclination with respect to the irradiation light from the light source is the light source. An optical device, which is provided in the middle of an optical path from a predetermined object to the predetermined object, and cancels an aberration generated in the optical system with an aberration generated in the parallel plate. 19. An optical device having a light source and an optical system for irradiating a predetermined object with light emitted from the light source, wherein the parallel plate that produces an aberration due to an inclination with respect to the irradiation light from the light source is the light source. An optical device, which is provided in the middle of an optical path from a predetermined object to the predetermined object, and adjusts the inclination of the parallel plate so that the aberration of the light emitted to the predetermined object is set to a predetermined value. 20. An optical device having a light source and an optical system for irradiating a predetermined object with light emitted from the light source, wherein a hologram element in which an aberration of diffracted light changes depending on a tilt or a position on which the light strikes is provided. An optical device, which is provided in the optical path from a light source to the predetermined object, and cancels the aberration generated in the optical system with the aberration generated in the hologram element. 21. An optical device having a light source and an optical system for irradiating a predetermined object with light emitted from the light source, wherein a hologram element in which an aberration of diffracted light changes depending on a tilt or a position on which the light strikes is provided. It is provided in the middle of an optical path from a light source to the predetermined object, and the aberration of the light irradiated to the predetermined object is set to a predetermined value by adjusting the inclination of the hologram element or the position on which the light hits. Optical device. 22. An optical device having a light source and an optical system for irradiating light emitted from the light source onto a predetermined object, wherein an electro-optic crystal or a piezoelectric element that produces aberration by application of electric charge, current, voltage or electric field. A crystal or liquid crystal element is provided on the way of the optical path from the light source to the predetermined object, and the aberration generated in the optical system is canceled by the aberration generated in the electro-optical crystal, the piezoelectric crystal, or the liquid crystal element. Optical device. 23. An optical device having a light source and an optical system for irradiating a predetermined object with light emitted from the light source, wherein an electro-optic crystal or a piezoelectric element that produces aberrations by application of electric charge, current, voltage or electric field. By providing a crystal or liquid crystal element in the optical path from the light source to the predetermined object, and adjusting the electric charge, current, voltage or electric field applied to the electro-optical crystal, piezoelectric crystal or liquid crystal element,
An optical device, wherein an aberration of light radiated on the predetermined object is set to a predetermined value. 24. When adjusting the aberration in the optical path system for collecting the light emitted from the light source and irradiating it on the optical disk,
A parallel plate that generates an aberration due to an inclination with respect to the irradiation light from the light source is provided in the middle of the optical path system, and a transparent disc is installed at a place where the optical disc is attached. A method of adjusting an aberration of an optical information recording apparatus, which measures the aberration of light transmitted through a disc and adjusts the inclination of the parallel plate so that the aberration has a predetermined value. 25. When adjusting the aberration in the optical path system for converging the light emitted from the light source and irradiating the optical disc,
A parallel plate that generates an aberration due to an inclination with respect to the irradiation light from the light source is provided in the middle of the optical path system, and a transparent disc is installed at a place where the optical disc is attached. A method of adjusting an aberration of an optical information recording apparatus, which measures a focal spot of light transmitted through a disc and adjusts the inclination of the parallel plate so that the focal spot is minimized. 26. When adjusting the aberration in the optical path system for converging the light emitted from the light source and irradiating the optical disc,
A hologram element in which the aberration of the diffracted light changes depending on the tilt or the position where the light hits is provided in the middle of the optical path system, and a transparent disc is installed at the place where the optical disc is attached. An aberration adjusting method for an optical information recording apparatus, which measures an aberration of light transmitted through a transparent disk and adjusts a tilt of the hologram element or a position on which the light hits so that the aberration has a predetermined value. 27. When adjusting the aberration in the optical path system for converging the light emitted from the light source and irradiating the optical disc,
A hologram element in which the aberration of the diffracted light changes depending on the tilt or the position where the light hits is provided in the middle of the optical path system, and a transparent disc is installed at the place where the optical disc is attached. An aberration adjusting method for an optical information recording apparatus, which measures a focal spot of light transmitted through a transparent disk and adjusts an inclination of the hologram element or a position on which the light hits so as to minimize the focal spot. 28. When adjusting the aberration in the optical path system for collecting the light emitted from the light source and irradiating the light onto the optical disc,
An electro-optic crystal, a piezoelectric crystal or a liquid crystal element that generates aberrations by the application of electric charge, current, voltage or electric field is provided in the middle of the optical path system, and a transparent disc is installed at a place where the optical disc is attached. The light source is turned on to measure the aberration of the light transmitted through the transparent disc, and the electric charge, current, voltage or the like applied to the electro-optical crystal, the piezoelectric crystal or the liquid crystal element is adjusted so that the aberration has a predetermined value. Aberration adjusting method for an optical information recording apparatus for adjusting an electric field. 29. When adjusting the aberration in the optical path system for converging the light emitted from the light source and irradiating the optical disc,
An electro-optic crystal, a piezoelectric crystal or a liquid crystal element that generates aberrations by the application of electric charge, current, voltage or electric field is provided in the middle of the optical path system, and a transparent disc is installed at a place where the optical disc is attached. The light source is turned on to measure the focal spot of the light transmitted through the transparent disk, and the electric charge, current, voltage, or voltage applied to the electro-optic crystal, the piezoelectric crystal, or the liquid crystal element is adjusted so that the focal spot is minimized. Aberration adjusting method for an optical information recording apparatus for adjusting an electric field. 30. When adjusting the aberration in the optical path system for converging the light emitted from the light source and irradiating the optical disc,
A parallel plate that generates an aberration due to an inclination with respect to the irradiation light from the light source is provided in the middle of the optical path system, and an optical disc on which predetermined information is recorded is installed at a place where the optical disc is attached, and then the light source is turned on. A method of adjusting the aberration of the optical information recording apparatus, which measures a read signal or a servo signal from the optical disc and adjusts the inclination of the parallel plate so that the signal is the best. 31. When adjusting the aberration in the optical path system for converging the light emitted from the light source and irradiating the optical disc,
A hologram element in which the aberration of diffracted light changes depending on the tilt or the position where the light hits is provided in the middle of the optical path system, and an optical disc on which predetermined information is recorded is installed at a place where the optical disc is attached, and then a light source is turned on. Then, the read signal or the servo signal from the optical disk is measured, and the inclination of the hologram element or the position where the light hits is adjusted so that the signal is best adjusted. 32. When adjusting the aberration in the optical path system for converging the light emitted from the light source and irradiating the optical disc,
An electro-optic crystal, a piezoelectric crystal, or a liquid crystal element that generates an aberration by applying an electric charge, current, voltage, or electric field is provided in the middle of the optical path system, and an optical disc on which predetermined information is recorded is installed at a place where the optical disc is attached. Next, the light source is turned on to measure the read signal or the servo signal from the optical disk, and the electric charge, current, or voltage applied to the electro-optical crystal, the piezoelectric crystal, or the liquid crystal element so that the signal becomes the best. Alternatively, an aberration adjusting method for an optical information recording device that adjusts an electric field. 33. When adjusting an aberration in an optical path system that irradiates a predetermined object with light emitted from a light source, a parallel plate that causes an aberration due to an inclination with respect to the irradiation light from the light source is provided in the middle of the optical path system. An aberration adjusting method for an optical device, which is provided, measures an aberration of light emitted from the optical system, and adjusts an inclination of the parallel plate so that the aberration has a predetermined value. 34. When adjusting the aberration in the optical path system for irradiating a predetermined object with the light emitted from the light source, a parallel plate that generates aberration due to the inclination with respect to the irradiation light from the light source is provided in the middle of the optical path system. An aberration adjusting method for an optical device, which is provided, measures a condensed spot of light emitted from the optical system, and adjusts an inclination of the parallel plate so that a focal spot thereof is minimized. 35. When adjusting the aberration in the optical path system for irradiating a predetermined object with the light emitted from the light source, a hologram element in which the aberration of the diffracted light changes depending on the tilt or the position on which the light hits is provided in the middle of the optical path system. And an aberration adjusting method for an optical device, which measures the aberration of the light emitted from the optical system and adjusts the tilt of the hologram element or the position where the light hits so that the aberration has a predetermined value. 36. When adjusting an aberration in an optical path system for irradiating a predetermined object with light emitted from a light source, a hologram element whose aberration of diffracted light changes depending on a tilt or a position where the light hits is provided in the middle of the optical path system. And a method for adjusting the aberration of an optical device, which measures the focused spot of the light emitted from the optical system and adjusts the tilt of the hologram element or the position where the light hits so as to minimize the focal spot. 37. An electro-optic crystal, a piezoelectric crystal or a liquid crystal that generates an aberration by applying an electric charge, a current, a voltage or an electric field when adjusting an aberration in an optical path system for irradiating a predetermined object with light emitted from a light source. An element is provided in the middle of the optical path system to measure the aberration of the light emitted from the optical system, and the aberration has a predetermined value, the electro-optical crystal, the piezoelectric crystal or a charge applied to the liquid crystal element, An aberration adjustment method for an optical device that adjusts a current, a voltage, or an electric field. 38. An electro-optical crystal, a piezoelectric crystal or a liquid crystal that generates aberration by applying a charge, current, voltage or electric field when adjusting the aberration in an optical path system for irradiating a predetermined object with light emitted from a light source. A charge is applied to the electro-optic crystal, piezoelectric crystal, or liquid crystal element so that the element is provided in the middle of the optical path system, the focused spot of the light emitted from the optical system is measured, and the focal spot is minimized. , An aberration adjusting method of an optical device for adjusting a current, a voltage or an electric field.