JP2004311026A - Optical head device and method for manufacturing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical head device which has a large numerical aperture objective lens and yet is easily manufactured and assembled and in which performance deterioration caused by disk tilting can be corrected. <P>SOLUTION: The optical head device used for recording information or reproducing recorded information by converging the point image of a light beam emitted from a light source on the information recording surface of an optical disk is provided with the light source, an objective lens for converging the light beam emitted from the light source on the information recording surface, a detection means for detecting an amount of tilt of the optical disk with respect to the optical axis of the light beam emitted from the light source or an amount of third-order coma aberration generated by the tilting of the optical disk, and an actuator driven to tilt the entire objective lens with respect to the optical axis of the beam emitted from the light source based on the detection result of the detection means. The objective lens satisfies DC/LC>-0.9 wherein DC (mλ, code is negative) is third-order coma aberration generated when the optical disk is tilted by 0.5°, and LC (mλ, code is positive) is third-order coma aberration generated when the objective lens is tilted by 0.5°. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an optical head device that focuses a light beam from a light source on an information recording surface of an optical disk such as a digital video disk, a digital audio disk, and an optical memory disk for a computer, and a method of manufacturing the same.

  Generally, in an optical head device for an optical disk, an objective lens for recording information or reproducing the recorded information by condensing a diffraction-limited point image on an information recording surface of the optical disk has an aspherical surface. Single lenses using are often used.

  Hereinafter, a conventional optical head device will be described with reference to the drawings.

  FIG. 7 is a schematic configuration diagram showing a conventional optical head device. As shown in FIG. 7, the light flux emitted from the semiconductor laser 151 is changed in direction of the optical path by the beam splitter 152, and becomes substantially parallel light by the collimator lens 153. The direction of the optical path of the laser light is further changed by the bending mirror 154, and the laser light is focused on the information recording surface 157 of the optical disk 156 by the objective lens 155. Here, the objective lens 155 is driven by the actuator 160. The laser light focused on the information recording surface 157 of the optical disc 156 is diffracted by the unevenness formed on the information recording surface 157. The laser light reflected and diffracted by the information recording surface 157 of the optical disc 156 passes through the objective lens 155, the direction of the optical path is changed by the bending mirror 154, and the collimating lens 153, the beam splitter 152, and the cylindrical lens 158 The light is transmitted and collected on the photodetector 159. Then, a change in the amount of light modulated on the information recording surface 157 of the optical disc 156 is detected by an electric signal of the photodetector 159, and data on the information recording surface 157 is read.

  Here, a wavefront aberration occurs in the objective lens 155 due to a manufacturing error during manufacturing. This wavefront aberration can be considered separately for each of the third-order spherical aberration, third-order coma aberration, third-order astigmatism, and higher-order aberration components.

  Of these aberration components, the third-order coma can be prevented from occurring in design by making the lens surface of the objective lens 155 a rotationally symmetric aspheric surface. However, in actuality, a decenter (a vertical direction to the optical axis) between the first surface 161 which is a surface on the parallel light flux side of the objective lens 155 and the second surface 162 which is a surface on the light condensing side, which occurs during manufacturing. The third order coma occurs due to the dominant factors of the shift amount) and the tilt (inclination with respect to the plane perpendicular to the optical axis) of the first surface 161 and / or the second surface 162 of the objective lens 155. I do. Among these two factors, the third-order coma aberration caused by the tilt is proportional to approximately the third power of the NA (numerical aperture) of the objective lens 155.

  Generally, when the lens is inclined with respect to the optical axis, third-order coma aberration occurs. Therefore, by adjusting the tilt angle, the third-order coma caused by the manufacturing error can be canceled by the third-order coma generated at that time. For this reason, the objective lens 155 of the optical head device is inclined so as to reduce the third-order coma aberration in the process of assembling the optical head device. Such an operation is called “tilt adjustment”, and the tilt angle at this time is called “tilt adjustment angle”.

  2. Description of the Related Art In recent years, recording densities have been increasing, as in DVDs (digital video discs) and DVD-RAMs. In order to achieve high density, it is important to form a small spot on the optical disk, but it is known that the spot diameter can be reduced by increasing the numerical aperture of the lens. Therefore, the numerical aperture of the lens is gradually increased for higher density, and is 0.6 for DVD. For further densification, the numerical aperture needs to be 0.6 or more. Conventionally, in the lens design, aberrations are large even if decentering of the first and second surfaces of the lens occurs in consideration of a manufacturing error when manufacturing the lens or an assembly error when assembling the optical head. The design was made so that the aberration would not increase even if light was incident from off-axis. Despite the high demand for high numerical aperture lenses, one of the reasons that have not yet been commercialized is that it is easy to reduce axial aberrations in lens design, but it is important to consider manufacturing and assembly tolerances. If the design is performed while the lens is designed, it is very difficult to design a single lens having a sufficient tolerance.

  Also, when the numerical aperture is increased, the third-order coma generated by the tilt of the disk increases. At present, there is a possibility that a tilt of about 0.5 degree is generated due to the warpage of the disk or the like. When a tilt of this magnitude is generated, the third-order coma aberration has a numerical aperture of 0.6 and a focal length of 3.0 mm. In the optical system described above, about 70 mλ is generated. For the spot to be sufficiently small and to be a reproducible spot in a DVD system, the third-order coma is required to be 70 mλ or less. Therefore, in consideration of the above-mentioned tertiary coma caused by the tilt of the disk and the tertiary coma caused by a manufacturing error, an assembly error and the like, data cannot be recorded / reproduced by this system.

  When a lens having a numerical aperture larger than 0.6 is designed by the above-described design technique, satisfactory design cannot be performed because aberrations due to decenter and aberrations due to off-axis light are generally in inverse proportion. That is, the lens is very difficult to manufacture or assemble. Also, if there is a tilt due to the warpage of the disc, a large amount of third-order coma aberration occurs, and the system cannot be recorded and reproduced.

  The present invention has been made to solve the above-mentioned problems in the prior art, and it is easy to manufacture and assemble while providing an objective lens with a high numerical aperture, and it is possible to correct performance degradation caused by tilt of a disk. It is an object to provide a possible optical head device. Another object of the present invention is to provide a manufacturing method for assembling the optical head device.

  To achieve the above object, the present invention has the following configuration.

  An optical head device according to the present invention is used for recording information or reproducing the recorded information by converging a light beam emitted from a light source onto a point image on an information recording surface of an optical disc. A light source, an objective lens for condensing a light beam emitted from the light source on the information recording surface, and a tertiary frame generated by the amount of inclination of the optical disk with respect to the optical axis of the light beam emitted from the light source or the inclination of the optical disk. Detecting means for detecting any of the aberration amounts, and an actuator driven to tilt the entire objective lens with respect to the optical axis of the light beam emitted from the light source based on a result detected by the detecting means; The lens converts the third-order coma aberration generated when the optical disc is tilted by 0.5 degrees into DC (mλ, the sign is negative), and the third-order coma aberration generated when the objective lens is tilted by 0.5 degrees. The LC (m [lambda, sign is positive) when the satisfy the DC / LC> -0.9.

  According to such an optical head device, the tertiary coma caused by the tilt of the optical disk can be corrected by slightly tilting the objective lens. Further, since the amount of tilt of the objective lens for correction is small, the amount of astigmatism generated according to the amount of tilt of the objective lens can be small. Therefore, the residual aberration after the correction is good. In addition, since the objective lens is mounted on the actuator and tilted according to the tilt amount of the optical disc, even if the optical disc has a warp or the like, it is possible to suppress the occurrence of aberration caused by the warp or the like. Therefore, good recording and / or reproduction can be performed.

  In the above optical head device, it is particularly preferable that DC / LC> -0.8 is satisfied.

  In the above optical head device, the numerical aperture is preferably 0.62 or more. According to such a configuration, the spot diameter of the light beam on the optical disk can be reduced, so that high-density recording of the optical disk can be realized.

  Further, in the above optical head device, it is preferable that DC + LC is 10 mλ or more and 40 mλ or less. By setting DC + LC to 10 mλ or more, tertiary coma caused by the tilt of the optical disk can be corrected by only slightly tilting the objective lens. Further, since the amount of tilt of the objective lens for correction is small, the amount of astigmatism generated according to the amount of tilt of the objective lens can be small. Therefore, the residual aberration after the correction is good. Further, by setting DC + LC to 40 mλ or less, it is possible to suppress the deterioration of the aberration characteristics when the objective lens is unexpectedly tilted due to vibration or the like. As described above, good recording and / or reproduction can be performed.

In the above optical head device, the astigmatism remaining after the tilt angle of the optical disk is X (degree) and the third-order coma aberration generated when the optical disk is tilted by X (degree) is canceled by tilting the objective lens. Is Y (mλ), and the coefficient a when the relationship between X and Y is approximated by Y = aX ² + bX + c is preferably 30 or more and 35 or less.

  According to this configuration, tertiary coma caused by the tilt of the optical disk can be corrected by only slightly tilting the objective lens. Further, since the amount of tilt of the objective lens for correction is small, the amount of astigmatism generated according to the amount of tilt of the objective lens can be small. Therefore, the residual aberration after the correction is good. Also, since the objective lens is mounted on the actuator and tilted according to the amount of tilt of the optical disk, it constitutes an optical system that can suppress the occurrence of aberration caused by the optical disk even if it has warpage. it can. In addition, it is possible to suppress deterioration of aberration characteristics when the objective lens is unexpectedly tilted due to vibration or the like. As described above, good recording and / or reproduction can be performed.

  In the first optical head device, it is preferable that the objective lens is adjusted so as to reduce third-order coma aberration. According to such a configuration, since the third-order coma aberration due to an error in manufacturing the lens or in assembling the optical head device can be reduced by the tilt adjustment, an allowable range of the manufacturing error and the assembling error is reduced, and an inexpensive optical head device is obtained. be able to.

  Next, the method for manufacturing an optical head device according to the present invention records information or reproduces recorded information by converging a light beam emitted from a light source onto a point image on an information recording surface of an optical disc. A light source, an objective lens for condensing a light beam emitted from the light source on the information recording surface, and a third order generated by the amount of inclination of the optical disk with respect to the optical axis of the light beam emitted from the light source or the inclination of the optical disk. A light comprising: detecting means for detecting any of the coma aberration amounts; and an actuator driven to tilt the entire objective lens with respect to the optical axis of the light beam emitted from the light source based on the result detected by the detecting means. In a method of manufacturing a head device, the objective lens is configured to reduce the third-order coma aberration generated when the optical disc is tilted by 0.5 degree to DC (mλ, the sign is negative) and to set the objective lens to 0.5. Assuming that the third-order coma generated when tilted is LC (mλ, the sign is positive), DC / LC> −0.9 is satisfied, and after determining the light flux incident on the objective lens, The actuator is fixed at an initial position by performing a tilt adjustment so that the coma of the wavefront of the light beam emitted from the objective lens is reduced.

  According to this configuration, since the objective lens is installed after the tilt adjustment, the third-order coma aberration due to an error in manufacturing the lens or assembling the optical head device can be reduced. Therefore, the allowable range of manufacturing errors and assembly errors is reduced, and an inexpensive optical head device can be obtained.

  According to the present invention, an optical head device that is inexpensive and capable of good recording and / or reproduction can be obtained.

  Hereinafter, the present invention will be described more specifically with reference to embodiments.

(Embodiment 1)
FIG. 1 is a diagram showing a state of focusing by an objective lens according to an embodiment of the present invention. As shown in FIG. 1, the parallel light beam 6 enters the objective lens 1 from the first surface 3 that is the light source side surface, and exits from the second surface 4 that is the disk side surface. The light is condensed on the information recording surface 5 by passing through.

  Specific numerical examples of the present invention are shown below. Note that the first surface of the objective lens is the surface on the light source side, and the second surface is the surface on the disk side (condensing side). The optical disk is a parallel flat plate. Further, the design wavelength is 655 nm, and the refractive index of the optical disk substrate is 1.56. Various symbols are defined as follows.

f: focal length of the objective lens (mm)
R1: radius of curvature of the first surface of the objective lens (mm)
R2: radius of curvature of the second surface of the objective lens (mm)
d: thickness of objective lens (mm)
n: Refractive index of objective lens t: Thickness (mm) of substrate of optical disk
NA: numerical aperture of the objective lens when focusing through an optical disk

  The aspherical shape of the optical disc objective lens 1 is given by the following equation (1).

here,
h: height from the optical axis (h = (x ² + y ² ) ^1/2 )
cj: curvature of the vertex of the lens surface of the j-th surface (cj = 1 / Rj, Rj is the radius of curvature)
kj: Conical constant of the j-th surface Aj, i: i-th aspherical coefficient of the j-th surface.

  Further, parameters representing each performance of the objective lens are defined as follows.

W0: Least square error of on-axis wavefront aberration (unit is mλ (mλ is a unit of 1/1000 of wavelength λ))
DC: Third-order coma aberration generated when the optical disk is tilted by 0.5 degrees (mλ, sign is negative)
LC: third-order coma aberration generated when the objective lens is tilted by 0.5 degrees (mλ, sign is positive)
TH: tilt angle (degree) of the objective lens that can cancel third-order coma aberration generated when the optical disk is tilted by 0.5 degrees

  The following are specific numerical examples.

f = 3.05
R1 = 2.00300
R2 = -15.333015
d = 1.692
n = 1.60297
t = 0.6
NA = 0.65
k1 = −6.76563 × 10 ⁻¹
A1,4 = 2.527642 × 10 ^-3
A1,6 = 1.525075 × 10 ^-4
A1,8 = −2.502308 × 10 ⁻⁵
A1,10 = −6.699123 × 10 ⁻⁶
k2 = −6.707921 × 10 ⁺¹
A2,4 = 5.385577 × 10 ^-3
A2,6 = -1.818641 × 10 ^-3
A2,8 = 2.990897 × 10 ⁻⁴
A2,10 = −2.064762 × 10 ⁻⁵
W0 = 3.4
DC = -66.8
LC = 85.7
TH = 0.39

  FIGS. 2 and 3 show aberration diagrams of the objective lens.

  FIG. 2 shows the lateral aberration of the objective lens when the angle of view ratio is changed. A field angle ratio of 1.0 corresponds to a state where 0.5-degree off-axis light is incident, and a field angle ratio of 0 corresponds to a state where on-axis light is incident. In the figure, DY indicates lateral aberration in the Y-axis direction, and DX indicates lateral aberration in the X-axis direction.

  In FIG. 3, SA indicates spherical aberration, and OSC indicates a sine condition. AS indicates astigmatism, T indicates a tangential direction, and S indicates a sagittal direction. DIST indicates distortion (field curvature).

  In the objective lens of this numerical example, the on-axis wavefront aberration W0 is suppressed to a low value of 3.4 mλ. Therefore, deterioration near the center of the spot is small. As a result, when detecting a signal recorded on the information medium surface of the optical disk, crosstalk from an adjacent signal can be reduced.

  The third-order coma aberration DC generated when the optical disk is tilted by 0.5 degrees is -66.8 mλ, and the third-order coma LC generated when the objective lens is tilted by 0.5 degrees is 85.7 mλ. Therefore, the relationship of DC / LC = −0.78> −0.8 is established. Accordingly, the tilt angle TH of the objective lens required to cancel the third-order coma aberration generated when the optical disk is tilted by 0.5 degrees can be reduced to 0.39 degrees. That is, even if the tertiary coma caused by the tilt of the optical disk is corrected by tilting the objective lens, the tilt amount of the objective lens at that time can be suppressed to a small value. On the other hand, astigmatism occurs approximately in proportion to the square of the tilt of the objective lens, so that astigmatism that occurs when correcting the third-order coma aberration can be suppressed to a small value. Therefore, good recording and / or reproduction can be performed even at the time of correcting the third-order coma aberration.

  The numerical aperture NA of the objective lens is 0.65. When the numerical aperture NA is 0.62 or more, it is preferable because recording can be performed at higher density.

  DC + LC is 18.9 (mλ). Therefore, when the optical axis of the objective lens is arranged parallel to the normal direction of the optical disk surface, if a light beam inclined to the objective lens by 0.5 degrees with respect to the optical axis enters the objective lens, third-order coma aberration is reduced. appear. When DC + LC is equal to or more than 10 mλ, the amount of tilt of the lens when the objective lens is tilted to cancel the tertiary coma generated when the optical disk is tilted is preferably small. Further, it is preferable that DC + LC is 40 mλ or less, because the amount of deterioration (the amount of aberration) when the objective lens is tilted with respect to the optical axis due to vibration of an actuator or the like can be reduced.

In the above numerical examples, the horizontal axis represents the tilt angle X (degrees) of the optical disc, and the third-order coma aberration that occurs when the optical disc tilts by X (degrees) remains after canceling by tilting the objective lens. If the vertical axis indicates the astigmatism Y (mλ), the curve shown in FIG. 4 is obtained. When this curve is fitted with a quadratic curve represented by Y = aX ² + bX + c, the coefficients are a = 31.197, b = 1.4089, c = −0.1304 (least square error = 0 .999). When the second order coefficient a is 30 or more, the tolerance for the swing of the objective lens becomes loose (that is, the amount of astigmatism generated when the objective lens is tilted due to vibration or the like can be reduced). This is preferable because the tolerance of the mechanism design of the holding system is increased. Further, it is preferable that the coefficient a is 35 or less, because the effect of correcting the third-order coma generated by the tilt of the optical disc is exhibited.

  In the above numerical example, the thickness t of the substrate of the optical disk is 0.6 mm. If the substrate thickness is about 0.6 mm (particularly 0.59 to 0.61 mm), it is preferable because recording and / or reproduction of DVD are easy.

(Embodiment 2)
FIG. 5 is a configuration diagram showing an optical head device according to Embodiment 2 using an objective single lens for an optical disk.

  As shown in FIG. 5, the direction of the optical path of the laser light emitted from the semiconductor laser 51 is changed by the beam splitter 52, and the laser light becomes substantially parallel light by the collimator lens 53. The direction of the optical path of the laser light is further changed by the bending mirror 54, and the laser light is focused on the information recording surface 57 of the optical disk 56 by the optical disk objective single lens 55 of the present invention described in the first embodiment. Here, the objective lens 55 is driven by the actuator 60. The laser light focused on the information recording surface 57 of the optical disk 56 is diffracted by the irregularities formed on the information recording surface 57. The laser light reflected and diffracted by the information recording surface 57 of the optical disk 56 passes through the objective lens 55, and the direction of the optical path is changed by the bending mirror 54, and the collimating lens 53, the beam splitter 52, and the cylindrical lens 58 The light is transmitted and collected on the photodetector 59. Then, a change in the amount of light modulated on the information recording surface 57 of the optical disk 56 is detected by the electric signal of the photodetector 59, and the data on the information recording surface 57 is read.

  As a manufacturing procedure of such an optical head device, a light source (semiconductor laser 51), a collimating lens 53, and, if necessary, a beam splitter 52 and a bending mirror 54 are fixed, and then the tilt adjustment (tilt) of the objective lens 55 is performed. (Adjustment). The tilt adjustment is performed, for example, by observing the light condensing state after the light from the semiconductor laser 51 passes through the objective lens 55 so that the third-order coma aberration is minimized, or the state in which the light spot disturbance is minimized. This is performed by tilting and fixing the objective lens 55 or the actuator 60 holding the objective lens 55 with respect to the optical head base (not shown). In order to tilt the objective lens 55 or the actuator 60, for example, an adjustment screw can be used. By following this manufacturing procedure, no off-axis light is incident on the objective lens 55. Therefore, only off-axis tilt aberration of the lens becomes a problem in lens performance, and the yield is improved in the assembly process of the optical head device. .

  Third-order coma aberration occurs due to the warp or tilt of the optical disk 56. This is corrected by tilting the objective lens 55 according to the amount of tilt of the optical disk 56 or the amount of tertiary coma generated based on the amount of tilt of the optical disk 56 by the actuator 60 having the objective lens 55 mounted thereon. The specific configuration for detecting the amount of tilt of the optical disk 56 or the amount of third-order coma generated thereby is not particularly limited, and may be a known configuration.

  FIG. 6 shows a configuration example of an actuator 60 for tilting the objective lens 55. 6A and 6B, reference numeral 55 denotes an objective lens, 610 denotes a lens holder that holds the objective lens 55, 612a and 612b denote through holes provided in the lens holder 610, and 615a and 615b denote through holes, respectively. A substantially ring-shaped coil provided on the lens holder 610 so as to surround the 612a and 612b, and 620a and 620b are a pair of permanent magnets that freely pass through the through holes 612a and 612b. The pair of permanent magnets 620a and 620b have polarities in the same direction and are installed on the optical head base. The lens holder 610 is held on the optical head base via an elastic member (not shown). The actuator 60 is also used as an actuator for focusing and tracking of the objective lens 55. Focus adjustment is performed by flowing current in the same direction through the pair of coils 615a and 615b to move the objective lens 55 in the vertical direction on the paper as shown in FIG. On the other hand, if currents in opposite directions are applied to the pair of coils 615a and 615b (or if current is applied to only one of the pair of coils 615a and 615b), as shown in FIG. Can be tilted. By using this principle and installing a pair of permanent magnets and coils in the tangential direction and the radial direction of the optical disk, the objective lens 55 can be inclined in any direction with respect to the optical disk. Note that harmful third-order coma aberration due to the tilt of the optical disk is often caused by the tilt of the optical disk in the tangential direction. Most of the next coma can be corrected. It is needless to say that the configuration of the actuator 60 for imparting an inclination to the objective lens 55 is not limited to that shown in FIG.

  The NA required for an optical disk to be read or recorded depends on its recording density. In order to realize high-density recording, a high NA is generally used. The higher the NA, the tighter the manufacturing and mounting tolerances, so the current process limits the NA to about 0.6. When the objective lens of the first embodiment designed as described above is used as the objective lens 55, even after the NA of the objective lens 55 is increased to 0.62 or more, it is possible to suppress the aberration after the tilt adjustment to a low level. Therefore, tolerances in the manufacturing process of the optical head device are reduced, leading to an improvement in yield, and mass production becomes possible.

  The embodiments described above are all intended to clarify the technical contents of the present invention, and the present invention is not construed as being limited to only such specific examples. Various modifications may be made within the spirit of the invention and the scope of the appended claims, and the invention should be construed broadly.

FIG. 1 is an optical path diagram showing a focused state by an objective lens according to Embodiment 1 of the present invention. FIG. 2 is an aberration diagram of an objective lens in a numerical example according to the first embodiment of the present invention. FIG. 3 is an aberration diagram of an objective lens in a numerical example according to the first embodiment of the present invention. FIG. 4 is a diagram showing a relationship between the amount of tilt of the optical disk and the amount of residual astigmatism after the third-order coma aberration correction in a numerical example according to the first embodiment of the present invention. FIG. 5 is a configuration diagram of an optical head device according to Embodiment 2 of the present invention. FIGS. 6A and 6B are cross-sectional views illustrating an example of an operation of an actuator that imparts an inclination to an objective lens. FIG. 7 is a configuration diagram of a conventional optical head device.

Explanation of reference numerals

DESCRIPTION OF SYMBOLS 1 Objective lens 2 Optical disk 3 1st surface 4 2nd surface 5 Information recording surface 6 Parallel light flux 51 Semiconductor laser 52 Beam splitter 53 Collimating lens 54 Bending mirror 55 Objective lens 56 Optical disk 57 Information recording surface 58 Cylindrical lens 59 Photodetector 60 Actuator

Claims (6)

An optical head device used for recording information or reproducing the recorded information by condensing a point image on the information recording surface of an optical disc with a light beam emitted from a light source,
A light source,
An objective lens for condensing the light beam emitted from the light source on the information recording surface,
Detecting means for detecting either the amount of tilt of the optical disk with respect to the optical axis of the light beam emitted from the light source or the amount of tertiary coma caused by the tilt of the optical disk;
An actuator driven to tilt the entire objective lens with respect to an optical axis of a light beam emitted from the light source, based on a result detected by the detection unit,
The objective lens has a DC (mλ, sign is negative) third-order coma generated when the optical disc is tilted by 0.5 degrees, and a third-order coma generated when the objective lens is tilted by 0.5 degrees. An optical head device that satisfies DC / LC> −0.9, where coma is LC (mλ, sign is positive).   The optical head device according to claim 1, wherein the objective lens satisfies DC / LC> -0.8.   The optical head device according to claim 1, wherein a numerical aperture of the objective lens is 0.62 or more.   The objective lens for an optical disc according to claim 1, wherein DC + LC of the objective lens is 10 mλ or more and 40 mλ or less. The objective lens reduces the astigmatism remaining after canceling the tilt angle of the optical disc by X (degrees) and the third-order coma aberration generated when the optical disc is tilted by X (degrees) by tilting the objective lens by Y (mλ). An optical head device, wherein a coefficient a when the relationship between X and Y is approximated by Y = aX ² + bX + c is 30 or more and 35 or less. The light flux emitted from the light source is used to record information or reproduce the recorded information by converging a point image on the information recording surface of the optical disc,
A light source, an objective lens for condensing the light beam emitted from the light source on the information recording surface, and an inclination amount of the optical disk with respect to an optical axis of the light beam emitted from the light source or an inclination of the optical disk. Detecting means for detecting any of the following coma aberration amounts, and an actuator driven to tilt the entire objective lens with respect to an optical axis of a light beam emitted from the light source based on a result detected by the detecting means A method for manufacturing an optical head device comprising:
The objective lens has a DC (mλ, sign is negative) third-order coma generated when the optical disc is tilted by 0.5 degrees, and a third-order coma generated when the objective lens is tilted by 0.5 degrees. Assuming that coma is LC (mλ, sign is positive), DC / LC> −0.9 is satisfied,
An optical head device that, after determining the light beam incident on the objective lens, performs a tilt adjustment so that a coma of a wavefront of the light beam emitted from the objective lens is reduced, and fixes the actuator at an initial position. Manufacturing method.

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