JP2010218668A - Apparatus for inspecting optical pickup, and apparatus for assembling and adjusting optical pickup - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide: an inspection apparatus and an inspection method, which measure optical pickup aberration of an optical pickup with a simple optical system accurately in a short time period; and an adjustment method and an adjustment apparatus, which adjust objective lens inclination of the optical pickup accurately. <P>SOLUTION: A third-order coma aberration is corrected by subtracting a value of a constant times of a tilt component in wavefront aberration of the optical pickup from a value of third-order coma aberration in the wavefront aberration of the optical pickup detected by a wavefront aberration detecting means. For instance, this allows the wavefront aberration of the third-order coma aberration of emitted light from the optical pickup to be measured accurately even if there is a position deviation in the horizontal direction of the optical pickup. Furthermore, since correction of the position deviation can be eliminated or simplified, aberration measurement can be performed in a short period of time. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an optical pickup used for recording or reproducing information with respect to an optical information medium represented by an optical disc, and more particularly to an aberration inspection apparatus and an optical pickup adjustment apparatus for an optical pickup.

  In recent years, optical disk devices have been actively developed as means for recording and reproducing large amounts of data, and approaches for achieving higher recording density have been made.

  In addition to conventional CDs (compact discs) and DVDs (digital multipurpose discs), recently, as the recording capacity of optical information media has further increased, the wavelength of the light source has been shortened, and the NA of the focusing optical system has been increased (NA: aperture). For example, a Blu-ray Disc that can record or reproduce about 25 GB of digital information on a single layer on one side and about 50 GB on two layers on one side has already been put into practical use.

  As the capacity of the optical disk apparatus increases, an optical pickup that is a main component of the optical disk apparatus is required to have extremely high performance. Among them, the aberration performance that determines the condensing performance of the condensing optical system is close to the diffraction limit, which is the theoretical limit in wave optics, as the wavelength used is shortened and the NA of the objective lens is increased. Performance is required.

  In order to realize the performance, it is necessary to increase the processing accuracy of the optical component which is a component of the optical pickup. Also, higher accuracy is required for the accuracy of assembly adjustment when the optical component is assembled to the optical base of the optical pickup and the aberration measurement accuracy for inspecting the aberration performance of the optical pickup that has been assembled. Yes.

  In this optical pickup adjustment process, the optical axis of the laser beam, which is ideally the light source, and the optical axis of the objective lens are arranged so as to coincide with each other, and the light is emitted with respect to the optical axis of the laser light emitted from the objective lens. Adjustment is performed so that the optical disk, which is an information medium, has a vertical posture.

  However, since coma aberration is usually generated in the light emitted from the objective lens due to assembly errors of the optical components that are constituent elements and coma aberration of the optical components alone, the objective lens is attached to the laser. An adjustment method is generally used in which the coma aberration is canceled by inclining with respect to the optical axis of light.

  The adjustment of the objective lens tilt of the optical pickup and the inspection of the aberration performance are performed based on the observation results obtained by observing the emitted light of the optical pickup with an observation device. Based on this result, it is an adjustment device when adjusting the tilt of the objective lens and the like, and when it is not adjusted, it can be used as an inspection device. A conventional example will be described.

  As a conventional optical pickup inspection apparatus, there is an apparatus using a spot analyzer as disclosed in Patent Document 1.

  This spot analyzer uses a collimator lens to pick up light emitted from an objective lens of an optical pickup, forms an image on a CCD camera, and detects the magnitude and direction of coma from the spot image of the CCD camera. is there. Specifically, the amount of coma aberration is obtained by visual or image analysis based on the roundness of the zero-order light image of the spot image projected on the monitor and the uniformity of the ring-shaped image by the first-order diffracted light. It is.

  The adjustment device using the spot analyzer has an advantage that the configuration is simple, but the aberration of the device itself may affect the measurement result. Therefore, the aberration of the device must be eliminated as much as possible. Since crosstalk between components cannot be completely removed, there is a problem that it is difficult to measure each aberration component independently with high accuracy, and the performance is high for adjustment and inspection of recent optical pickups for high-density recording. That's not enough. Therefore, recently, a method of detecting aberrations with high accuracy using an adjustment device using an interferometer is also used.

  Patent Document 2 discloses an aberration inspection apparatus using a Mach-Zehnder interferometer, in which light emitted from an optical pickup is incident on a Mach-Zehnder interferometer, and a phase is applied to an interference wavefront obtained from the Mach-Zehnder interferometer. By applying the modulation, the wavefront aberration of the light emitted from the optical pickup is obtained.

  The adjustment device using this Mach-Zehnder interferometer has the advantage of being able to accurately inspect the optical pickup because it can measure the wavefront aberration with high accuracy, but it can interfere with the optical pickup with very high accuracy to obtain reference light. The optical axis position of the system must be adjusted (several microns or less), the coherence of the light to be measured must be high, the influence of interference is very strong, and the measurement accuracy when noise light is superimposed on the interference wavefront However, it is difficult to use as a practical manufacturing apparatus because the optical system is complicated and the apparatus itself is very expensive.

  Furthermore, Patent Document 3 discloses an optical pickup wavefront measuring apparatus using the Shack-Hartmann method, and as a method capable of eliminating the drawbacks of the wavefront measuring apparatus using the interferometer, In recent years, it has attracted attention.

  A wavefront measuring apparatus using the Shack-Hartmann method makes light to be measured incident on a lens array, and the light to be measured is determined by a difference between a focal position of each lens constituting the lens array and a spot position on which the light to be measured is condensed. Hereinafter, the principle of the Shack-Hartmann method will be briefly described with reference to FIG.

  (A) in FIG. 3 is a phase wavefront distribution of the light to be measured. Region 1, region 2, region 3, region 4,. . . . In the microlenses L1, L2, L3, L4,. . . Respectively incident on. Each microlens has a focal length f.

  In general, when collimated light is incident on a lens, the displacement Δx of the spot position is proportional to fθ if the wavefront of the incident light has a tilt of θ.

  Therefore, the local wavefront slope of each region is obtained from the amount of deviation of the spot position of each microlens from the focal position (Δx1, Δx2, Δx3, Δx4,... The phase wavefront of the light to be measured is synthesized (FIG. 3b).

  Since this Shack-Hartmann method is not a wavefront detection method by interference, it is difficult to be affected by the coherence of the light to be measured and interference by noise light, and the reference light can be configured at low cost due to its simple structure. There is an advantage that an optical system for generating the light source is unnecessary and the optical system can be simplified.

  Hereinafter, the configuration of a conventional optical pickup wavefront measuring apparatus using the Shack-Hartmann method will be described with reference to FIG.

  In FIG. 6, the light emitted from the optical pickup 16 is converted into parallel light by the collimator lens 1 and then incident on the lens array 7 through the third beam splitter 33. The convergent light from the lens array 7 is CCD A plurality of spots are formed on the camera 8.

  The condensing position information of the plurality of spots received by the CCD camera 8 is sent to the image processing device 13, and the information processing device 15 calculates the phase wavefront by the Shack-Hartmann method.

  The information processing device 15 detects the magnitude and direction of various aberration components from the phase wavefront, and displays each information on the screen.

  By the way, in the initial state in which the optical pickup is disposed, the position of the objective lens 5 is usually largely deviated. Therefore, the parallel light from the collimator lens 1 is observed by the autocollimator 6, and the position of the optical pickup 16 is observed. Is adjusted to move the position of the objective lens 5 to a predetermined position range.

  Specifically, the position of the objective lens 5 in the horizontal direction is adjusted according to the position of the spot image displayed on the autocollimator 6, and the position of the objective lens 5 in the focus direction is adjusted according to the size of the spot image. I do.

  Further, the collimated light from the collimator lens 1 partially taken out by the first beam splitter 2 is condensed on the first light receiving element 12 by the cylindrical lens 11 and generally used for an optical pickup or the like. A focus error signal is generated by the focus / tracking error generator 14 using the astigmatism method.

  Further, the parallel light from the collimator lens 1 partially taken out by the second beam splitter 3 is condensed on the second light receiving element 10 by the lens 9, and the light condensing on the light receiving surface of the light receiving element 10. From the spot position, a tracking error signal is generated by the focus / tracking error generator 14.

Based on the focus error signal and the tracking error signal, the objective lens actuator 20 is driven in the focus direction and the tracking direction, respectively, and the position of the objective lens 5 is controlled.
Japanese Patent No. 3792218 JP 2004-271365 A JP 2005-353262 A

  A conventional optical pickup aberration inspection apparatus has a problem that it is easily influenced by off-axis characteristics of a collimator lens that is a component of a measurement optical system.

  The above problem will be described below with reference to FIG. 4 shows a part of the optical system of FIG. 6. In FIG. 4, reference numeral 23 denotes an objective lens of an optical pickup, 24 denotes a divergent light from the objective lens 23, which is converted into parallel light, and is obtained by the Shack-Hartmann method. It is a collimator lens for detecting wavefront aberration and guiding it to a lens array (not shown). The center line of each lens indicates the optical axis of the lens.

  FIG. 4A shows a state in which the respective lenses are ideally arranged in a state where the optical axes of the objective lens 23 and the collimator lens 24 coincide with each other.

  However, when the optical axes of the objective lens 23 and the collimator lens 24 are shifted as shown in FIG. 4B, the light passing through the collimator lens 24 is inclined and emitted.

  When light is emitted with an inclination from the optical axis in this way, an aberration commonly called off-axis aberration is generated in the collimator lens, and in particular, an optical pickup for high-density recording with a short wavelength and a large NA is measured. Appears prominently.

  As a result, an off-axis aberration of several mλ is generated for a positional shift of about 1 micron, and an error is generated in the aberration measurement result.

  In the current optical pickup for high-density recording, the aberration inspection specification may be about 15 mλ or less in order to obtain a sufficient condensing spot, and the influence of the measurement error is large, and the objective lens 23 and the collimator It is necessary to suppress the optical axis shift of the lens 24. In order to perform this optical axis deviation with high accuracy, it is necessary to provide a complicated dedicated position detection means. For example, an autocollimator is used as the position detection means.

  However, the position detection means usually has a trade-off relationship between the detection range and the detection resolution. Therefore, unlike conventional optical pickups for DVDs and CDs, and assembling telescopes, etc. where the Shack-Hartmann method has been often used in the past, high-precision position adjustment like the optical pickups for high-density recording. Is required, the position detection means having a wide detection sensitivity and the detection resolution being coarse, and the two steps of coarse adjustment by the position detection means and the detection range is narrow but the detection resolution is high and the position detection means is finely adjusted by the position detection means. Position adjustment must be performed, and there is a problem that adjustment tact increases.

  The present invention solves the above-described problems. An optical pickup aberration inspection apparatus and inspection method for measuring an optical pickup with a simple optical system with high accuracy in a short time, and an objective lens tilt of the optical pickup with high accuracy. An adjustment method and apparatus for adjustment are provided.

In order to solve the above problems and achieve the object, the invention according to claim 1 of the present invention provides:
A laser light source;
An objective lens for condensing laser light generated from the laser light source onto an optical information medium;
In order to measure the wavefront aberration of the light emitted from the optical pickup including the objective lens actuator that drives the objective lens in the focus direction and the tracking direction,
A collimator lens that converts light emitted from the objective lens of the optical pickup into parallel light;
Wavefront aberration detection means for detecting wavefront aberration of light emitted from the optical pickup that has passed through the collimator lens;
In a wavefront aberration inspection apparatus having
The third-order coma aberration is corrected by subtracting a value obtained by multiplying the tilt component in the wavefront aberration of the optical pickup by a constant from the value of the third-order coma aberration in the wavefront aberration of the optical pickup detected by the wavefront aberration detector. This is a wavefront aberration inspection apparatus.

  As a result, for example, even if there is a horizontal displacement of the optical pickup, it is possible to measure the wavefront aberration of the third-order coma aberration of the light emitted from the optical pickup with high accuracy, and further, the correction of the displacement is omitted. Or since it can simplify, an aberration measurement can be implement | achieved in a short time.

The invention according to claim 2 of the present invention provides
A laser light source;
An objective lens for condensing laser light generated from the laser light source onto an optical information medium;
In order to measure the wavefront aberration of the light emitted from the optical pickup including the objective lens actuator that drives the objective lens in the focus direction and the tracking direction,
A collimator lens that converts light emitted from the objective lens of the optical pickup into parallel light;
Wavefront aberration detection means for detecting wavefront aberration of light emitted from the optical pickup that has passed through the collimator lens;
In a wavefront aberration inspection apparatus having
The fifth-order coma aberration is corrected by subtracting a value obtained by multiplying the tilt component in the wavefront aberration of the optical pickup by a constant from the value of the fifth-order coma aberration in the wavefront aberration of the optical pickup detected by the wavefront aberration detector. This is a wavefront aberration inspection apparatus.

  As a result, for example, even if there is a horizontal displacement of the optical pickup, the wavefront aberration of the fifth-order coma aberration of the light emitted from the optical pickup can be measured with high accuracy, and correction of the displacement is omitted. Or since it can simplify, an aberration measurement can be implement | achieved in a short time.

The invention according to claim 3 of the present invention is
A laser light source;
An objective lens for condensing laser light generated from the laser light source onto an optical information medium;
In order to measure the wavefront aberration of the light emitted from the optical pickup including the objective lens actuator that drives the objective lens in the focus direction and the tracking direction,
A collimator lens that converts light emitted from the objective lens of the optical pickup into parallel light;
Wavefront aberration detection means for detecting wavefront aberration of light emitted from the optical pickup that has passed through the collimator lens;
In a wavefront aberration inspection apparatus having
Correction of third-order coma aberration is performed by subtracting a value obtained by multiplying a tilt component in the wavefront aberration of the optical pickup by a constant from the value of third-order coma aberration in the wavefront aberration of the optical pickup detected by the wavefront aberration detection means. ,further,
The fifth-order coma aberration is corrected by subtracting a value obtained by multiplying the tilt component in the wavefront aberration of the optical pickup by a constant from the value of the fifth-order coma aberration in the wavefront aberration of the optical pickup detected by the wavefront aberration detector. This is a wavefront aberration inspection apparatus.

  Thereby, for example, even if there is a horizontal displacement of the optical pickup, the wavefront aberration of the third-order coma aberration and the fifth-order coma aberration of the emitted light from the optical pickup can be measured with high accuracy. Since correction of deviation can be omitted or simplified, aberration measurement can be realized in a short time.

The invention according to claim 4 of the present invention is
The third-order coma aberration value in the wavefront aberration of the optical pickup detected by the wavefront aberration detection means is CM30 [mλ], the tilt component in the wavefront aberration of the optical pickup is Tilt [mλ], and the third-order coma aberration is corrected. The third-order coma aberration CM3 [mλ] satisfies the following (Equation 1), where k1 is a constant by which the tilt component is multiplied to perform the above.

  Thereby, for example, even if there is a horizontal displacement of the optical pickup, it is possible to perform the wavefront aberration measurement of the third-order coma aberration of the light emitted from the optical pickup with higher accuracy.

The invention according to claim 5 of the present invention is
The value of the fifth-order coma aberration in the wavefront aberration of the optical pickup detected by the wavefront aberration detection means is CM50 [mλ], the tilt component in the wavefront aberration of the optical pickup is Tilt [mλ], and the correction of the fifth-order coma aberration is performed. The fifth-order coma aberration CM5 [mλ] is the wavefront aberration inspection device according to claims 2 and 3, wherein k1 is a constant by which the tilt component is multiplied to perform the above.

  Thereby, for example, even when there is a horizontal displacement of the optical pickup, it is possible to perform the wavefront aberration measurement of the fifth-order coma aberration of the light emitted from the optical pickup with higher accuracy.

  According to a sixth aspect of the present invention, the wavefront aberration detecting means includes a lens array and a light receiving camera, and detects the wavefront aberration by the Shack-Hartmann method. This is a wavefront aberration inspection apparatus.

  Thereby, for example, the detection of the wavefront aberration can be measured with high accuracy.

  The invention according to claim 7 of the present invention is the wavefront aberration inspection apparatus according to any one of claims 1 to 5, wherein the wavefront aberration detecting means is a Mach-Zehnder interferometer.

  Thereby, for example, the detection of the wavefront aberration can be measured with high accuracy.

The invention according to claim 8 of the present invention provides
An optical pickup body having a laser light source;
An objective lens for condensing laser light generated from the laser light source onto an optical information medium;
To assemble and adjust an optical pickup including an objective lens actuator that drives the objective lens in a focus direction and a tracking direction,
A collimator lens for converting light emitted from the objective lens into parallel light of the optical pickup;
Wavefront aberration detection means for detecting wavefront aberration of light emitted from the optical pickup that has passed through the collimator lens;
In an optical pickup assembly adjusting device having an objective lens actuator adjusting means for holding the objective lens actuator and adjusting the position,
Correction of third-order coma aberration is performed by subtracting a value obtained by multiplying a tilt component in the wavefront aberration of the optical pickup by a constant from the value of third-order coma aberration in the wavefront aberration of the optical pickup detected by the wavefront aberration detection means. ,
In the optical pickup assembly adjusting device, the inclination of the objective lens actuator is adjusted in a direction in which the third-order coma aberration obtained by the correction decreases.

  Thereby, for example, even if there is a horizontal position shift of the optical pickup, it becomes possible to measure the wavefront aberration of the third-order coma aberration of the light picked up from the optical pickup with high accuracy. Tilt adjustment of the objective lens can be performed with high accuracy.

  In addition, the objective lens actuator or the objective lens may be displaced due to the tilt adjustment or vibration during tilt adjustment. In this case, the third order can be corrected without correcting the misalignment. Since coma can be detected accurately, the tilt adjustment can be performed in a short time.

  According to the ninth aspect of the present invention, the value of the third-order coma aberration in the wavefront aberration of the optical pickup detected by the wavefront aberration detecting means is CM30 [mλ], and the tilt in the wavefront aberration of the optical pickup is detected. The third-order coma aberration CM3 [mλ] satisfies (Equation 3), where the component is Tilt [mλ] and the constant multiplied by the tilt component is k3 in order to correct the third-order coma aberration. This is an optical pickup assembly adjustment apparatus.

  Accordingly, for example, even if there is a horizontal position shift of the optical pickup, it is possible to measure the wavefront aberration of the third-order coma aberration of the emitted light from the optical pickup with higher accuracy. The tilt adjustment of the objective lens can be performed with higher accuracy.

  In addition, the objective lens actuator or the objective lens may be displaced due to the tilt adjustment or vibration during tilt adjustment. In this case, the third order can be corrected without correcting the misalignment. Since coma aberration can be detected more accurately, the tilt adjustment can be performed in a shorter time.

  The invention according to claim 10 of the present invention is the optical pickup assembling / adjusting apparatus according to claims 8 to 9, wherein the wavefront aberration detecting means is a Mach-Zehnder interferometer.

  Thereby, for example, the detection of the wavefront aberration can be measured with high accuracy.

  According to an eleventh aspect of the present invention, the wavefront aberration detecting means includes a lens array and a light receiving camera, and detects the wavefront aberration by the Shack-Hartmann method. This is an optical pickup assembly adjustment apparatus.

  Thereby, for example, the detection of the wavefront aberration can be measured with high accuracy.

The invention according to claim 12 of the present invention provides
An optical pickup assembled and adjusted by the optical pickup assembling / adjusting apparatus according to claim 8.

  Thereby, for example, a high-performance optical pickup that can be recorded on or reproduced from each optical information medium of Blu-ray disc, DVD, and CD can be configured.

The invention according to claim 13 of the present invention provides
An optical disk drive using the optical pickup according to claim 12.

  Thereby, for example, a high-performance optical disk drive can be configured.

The invention according to claim 14 of the present invention provides
14. An optical information recording / reproducing apparatus using the optical disk drive according to claim 13.

  Thereby, for example, a high-performance optical information processing system can be configured.

  As described above, according to the wavefront aberration inspection apparatus and the optical pickup assembling / adjusting apparatus according to the present invention, an optical pickup measuring apparatus capable of measuring or adjusting with high accuracy and in a short time with a simple configuration. An optical pickup adjusting device is provided.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

(Embodiment 1)
FIG. 1 is a configuration diagram showing an example of a wavefront aberration inspection device for light emitted from an optical pickup according to Embodiment 1 of the present invention.

  In FIG. 1, the light emitted from the optical pickup 16 is converted into parallel light by the collimator lens 1 and then incident on the lens array 7 via the reflection mirror 4. The convergent light from the lens array 7 is reflected on the CCD camera 8. A plurality of spots are formed.

  Here, a cover glass (not shown) having a thickness optically equivalent to a protective layer of an optical information medium on which the optical pickup 16 performs recording or reproduction is disposed on the incident surface side of the collimator lens. The cover glass is switched according to the corresponding optical information medium.

  Next, the condensing position information of the plurality of spots received by the CCD camera 8 is sent to the image processing device 13, and the information processing device 15 calculates the phase wavefront by the Shack-Hartmann method.

  The information processing device 15 calculates the magnitude and direction of various aberration components from the phase wavefront and displays each information on the screen.

  As the procedure for deriving the magnitude and direction of each aberration component, a method is usually used in which the phase wavefront is expanded in Zernike polynomials in polar coordinates and obtained from the value of each Zernike expansion coefficient. The details are omitted here.

  Among the aberration components, components often used as analysis targets of the optical pickup are third-order coma aberration, third-order astigmatism, tilt, power, third-order spherical aberration, fifth-order coma aberration, and fifth-order astigmatism. 5th order spherical aberration, etc., coma, astigmatism, and tilt have directionality and are treated as vector values.

  Now, in the initial state where the optical pickup is disposed, the position of the objective lens 5 is usually deviated from the optimum position for measurement, and the phase wavefront includes off-axis aberrations caused by 1 in the collimator lens. Yes.

  Of the phase wavefront, the tilt component is generated in proportion to the amount of deviation from the optimum position for the measurement. Therefore, in the conventional method, the optical pickup 16 is aligned in the horizontal direction so that the tilt component is zero, so that the optical axis direction of the light emitted from the collimator lens 1 is changed to that of the collimator lens 1. The off-axis aberration generated from 1 in the collimator lens is reduced by matching with the optical axis direction.

  However, since the alignment accuracy is severe on the order of submicron, there is a problem that the control time for alignment becomes long, and an error occurs in the aberration measurement result due to a minute position shift due to vibration or the like.

  Incidentally, the coma component of the off-axis aberration generated from 1 in the collimator lens is generated in proportion to the amount of deviation from the optimum position for measurement. Therefore, the off-axis coma aberration generated by 1 in the collimator lens can be removed from the phase wavefront by subtracting the value obtained by multiplying the tilt component by a proportional coefficient from the coma aberration including the off-axis aberration. it can.

  By optimally selecting the proportional coefficient, the coma aberration obtained by subtracting the value obtained by multiplying the tilt component by the proportional coefficient from the coma aberration including the off-axis aberration is an optical pickup that does not include the off-axis aberration. This shows the coma aberration.

  Here, how to determine the proportionality coefficient will be described with reference to FIG.

  In FIG. 7, when the position of the optical pickup is shifted by Δx [mm] in the horizontal direction, the angle of the outgoing optical axis of the collimator lens is inclined by θ [deg]. At this time, the following equation is established between Δx and θ.

  Here, f [mm] represents the focal length of the collimator lens. At this time, the tilt pv value Tilt (pv) of the generated measurement wavefront is

It becomes. Here, R [mm] represents the radius of the emitted light beam of the collimating lens. When handling aberrations, rms values are often used. The tilt rms value Tilt (rms) of the measurement wavefront is

It becomes. Here, the coma component of the collimator lens off-axis aberration generated per field angle of 1 ° is (∂CM / ∂θ) [mλrms / deg], the wavelength of the light emitted from the optical pickup is λ [μm], and the numerical aperture Is NA, the amount of coma generated ΔCM [mλrms] when the optical pickup is displaced Δx [mm] in the horizontal direction and the angle of the output optical axis of the collimator lens is tilted θ [deg] is the tilt of the measurement wavefront When the unit of the actual measurement value Tilt is changed to mλrms and the relationship of R = NA · f is used,

It becomes. The coma aberration CM [mλrms] of the optical pickup not including the off-axis aberration is obtained by subtracting the coma aberration generation amount ΔCM [mλrms] generated by the collimator lens from the actual measurement value CM ₀ [mλrms] of the measurement wavefront. ] So that

The proportionality coefficient is expressed as follows.

  As described above, coma aberration that does not include the off-axis aberration can be obtained even when the optical pickup is deviated from the optimum position for measurement. As a result, the operation of correcting the position of the deviation from the optimum position for measurement can be omitted, and the adjustment tact can be reduced.

  In addition, since the position correction function for correcting the position deviation can be omitted or simplified, the facility cost can be reduced.

  As a specific example, for example, in order to measure an objective lens having a numerical aperture of 0.85 used in an optical pickup for a Blu-ray disc, the numerical aperture of the collimating lens is the numerical aperture of 0.85. A collimating lens with a numerical aperture of 0.9 is usually used.

  In this case, the collimating lens is designed such that, for example, when the relative deviation from the objective lens of the optical pickup is 1 micron, the coma aberration changes by 0.005λ.

  Therefore, since the coma aberration of the optical pickup is normally adjusted to 0.02λ or less, if the positional deviation is 1 micron, a measurement error as large as 0.005λ, that is, 25%, is generated.

  In order to reduce this error only by alignment, submicron alignment accuracy is required. For example, when it is desired to reduce the measurement error to 0.001λ or less, alignment must be performed at 0.2 micron. The resolution of the alignment mechanism must be as high as 0.1 micron or less, and high-speed position control must be performed.

  However, when the present invention is used, only a numerical calculation is performed, so that accurate aberration can be obtained regardless of the positional deviation. In this case, the amount of the positional deviation is not limited in principle, but the present invention is actually applied to a positional deviation of about 10 microns or less because it is limited by the aperture of the collimating lens and the displacement of the observation system. It is possible to apply.

  The coma aberration can be applied not only to the third-order coma aberration but also to the fifth-order or higher-order coma aberration.

  By the way, the optimum value of the proportionality coefficient has parameters such as the off-axis coma aberration of the collimating lens generated per 1 ° of the angle of view, the wavelength of the optical pickup outgoing light, the numerical aperture of the optical pickup outgoing light, and the focal length of the collimating lens It becomes the value of (Equation 1). Therefore, the measurement accuracy of the coma aberration measurement value can be further improved by using this value. In this case, coma aberration and tilt values are RMS (root mean square) values.

  In this embodiment, an example in which wavefront aberration is detected by the Shack-Hartmann method has been described. However, a phase shift method using a Mach-Zehnder interference system, a Michelson interference system, or the like can be applied as the aberration detection means. .

  Further, in this embodiment, an example of application to a wavefront aberration inspection apparatus for an optical pickup has been shown. However, in addition to this, the present invention can be applied to inspection apparatuses such as a combination lens, a telescope, and a microscope. Is possible.

(Embodiment 2)
In the first embodiment, the case where the present invention is applied to a wavefront aberration inspection device for light emitted from an optical pickup has been described. Here, as shown in FIG. 2, the objective lens actuator 20 is adjusted by the objective lens actuator position adjusting means 19 so that the third-order coma aberration component of each aberration component is minimized. It can be used as an optical pickup assembly adjusting device for adjusting the tilt of the objective lens of the optical pickup 16.

  In FIG. 2, the light emitted from the objective lens 5 is converted into parallel light by the collimator lens 1 and then incident on the lens array 7 via the reflection mirror 4. The convergent light from the lens array 7 is reflected on the CCD camera 8. A plurality of spots are formed.

  Here, a cover glass (not shown) having a thickness optically equivalent to a protective layer of an optical information medium on which the optical pickup 16 performs recording or reproduction is disposed on the incident surface side of the collimator lens. The cover glass is switched according to the corresponding optical information medium.

  The condensing position information of the plurality of spots received by the CCD camera 8 is sent to the image processing device 13, and the information processing device 15 calculates the phase wavefront by the Shack-Hartmann method.

  The information processing device 15 calculates the magnitude and direction of various aberration components from the phase wavefront and displays each information on the screen.

  Of the wavefront aberration component, the third-order coma aberration component changes in proportion to the inclination of the objective lens actuator. At this stage, the objective lens actuator 20 is not fixed to the optical pickup 16, and after the inclination of the objective lens actuator 20 is adjusted so that the third-order coma aberration component becomes zero, It will be fixed.

  Now, in the initial state in which the objective lens actuator 20 is disposed in the optical pickup 16, the position of the objective lens 5 included in the objective lens actuator 20 is usually shifted from the optimum position for measurement. Includes an off-axis aberration caused by 1 in the collimator lens.

  As described above, the tilt component of the phase wavefront is generated in proportion to the amount of deviation from the optimum position for the measurement.

  Therefore, in the conventional method, the objective lens actuator 20 is aligned in the horizontal direction so that the tilt component is zero, so that the optical axis direction of the light emitted from the collimator lens 1 is changed to the collimator lens 1. The off-axis aberration generated from 1 in the collimator lens is reduced, and then the inclination of the objective lens actuator 20 is adjusted so that the third-order coma aberration component becomes zero. It was.

  In this case, during the tilt adjustment work, force is applied to the objective lens actuator 20 and a positional shift of the order of microns or less occurs. Therefore, it is necessary to repeat the correction of the positional shift and the adjustment of the coma aberration. .

  Furthermore, since the alignment accuracy is as severe as the order of submicron, there is a problem that the control time for alignment becomes long, and an error occurs in the aberration measurement result due to a minute position shift due to vibration or the like.

  As in the first embodiment, the coma component of the off-axis aberration generated from 1 in the collimator lens is generated in proportion to the amount of deviation from the optimum position for measurement. Therefore, the off-axis coma aberration generated by 1 in the collimator lens can be removed from the phase wavefront by subtracting the value obtained by multiplying the tilt component by a proportional coefficient from the coma aberration including the off-axis aberration. it can.

  By optimally selecting the proportional coefficient, the coma aberration obtained by subtracting the value obtained by multiplying the tilt component by the proportional coefficient from the coma aberration including the off-axis aberration is an optical pickup that does not include the off-axis aberration. This shows the coma aberration.

  Therefore, even when the optical pickup is deviated from the optimum position for the measurement, it is possible to obtain coma aberration that does not include the off-axis aberration. As a result, the tilt adjustment of the objective lens actuator 20 can be continuously performed without performing the work of correcting the position of the deviation from the optimum position for measurement, thereby reducing the adjustment tact. Can do.

  In addition, since the position correction function for correcting the position deviation can be omitted or simplified, the facility cost can be reduced.

  The coma aberration can be applied not only to the third-order coma aberration but also to the fifth-order or higher-order coma aberration.

  In this embodiment, an example of use in an optical pickup assembly adjustment apparatus has been described. However, the present invention is also applied to an assembly adjustment apparatus for a combined lens and an assembly apparatus for an optical apparatus such as a telescope and a microscope. It is possible to apply

  Other contents are the same as those in the first embodiment.

(Embodiment 3)
FIG. 5 is a block diagram showing an example of an optical disc apparatus according to Embodiment 3 of the present invention.

  FIG. 5 is a diagram showing a configuration of an optical disc drive for explaining an application example of the optical pickup assembled by the assembly adjusting device according to the second embodiment of the present invention. An optical pickup unit 28, a pickup movement drive mechanism including a seek motor 30, a lead screw 29, a guide rail 27, and the like that moves the optical pickup unit 28 in the radial direction of the optical information medium 25, and a spindle that rotationally drives the optical information medium 25. The optical information medium 25 is constituted by a motor 26 and the like, and information is read from and recorded on the optical disk 14 by moving the optical information medium 25 in the radial direction.

  In FIG. 5, the present invention can be applied to a case where there are two light sources or two or more objective lenses. As a specific configuration example, for example, a blue laser with a wavelength of 405 nm is used as a first laser (not shown), a red laser is used as a second laser (not shown), and a Blu-ray disc is recorded by the first objective lens 31. Alternatively, reproduction is performed, and DVD or CD is recorded or reproduced by the second objective lens 32.

  As another combination, for example, a Blu-ray disc uses a first light source and a first objective lens 31 to perform recording or reproduction, and DVD and CD each have a common second objective lens 32. A configuration in which recording or reproduction is performed using a recording medium or a configuration in which recording or reproduction is performed using a common objective lens on a Blu-ray disc, DVD, or CD is conceivable.

  If the optical disk drive shown in FIG. 5 is applied to an optical information device, a compact and high-performance optical information device can be realized.

  Other contents are the same as those in the first embodiment and the second embodiment.

  A wavefront aberration inspection apparatus, an optical pickup assembly adjustment apparatus, etc. according to the present invention are an optical pickup assembly adjustment apparatus for an optical information recording / reproducing apparatus using an optical disk such as a magneto-optical recording apparatus or a CD, DVD, Blu-ray disk apparatus, or It is useful as an inspection device. Further, the present invention can also be applied as an optical pickup assembly adjusting device or an inspection device of a hologram recording device or a future ultra-high density recording / reproducing device.

The block diagram which shows an example of the optical pick-up wavefront aberration inspection apparatus in Embodiment 1 of this invention The block diagram which shows an example of the optical pick-up adjustment apparatus in Embodiment 2 of this invention Illustration explaining the principle of the Shack-Hartmann method The figure which shows the positional relationship of a collimator lens and an objective lens, and the relationship with each optical axis The block diagram which shows an example of the optical disk apparatus in Embodiment 3 of this invention The figure which shows the structure of the conventional optical pick-up wavefront aberration inspection apparatus The figure explaining the off-axis aberration of the collimator lens generated by the position shift of the optical pickup

DESCRIPTION OF SYMBOLS 1 Collimator lens 2 1st beam splitter 3 2nd beam splitter 4 Reflecting mirror 5 Objective lens 6 Autocollimator 7 Lens array 8 CCD camera 9 Lens 10 2nd light receiving element 11 Cylindrical lens 12 1st light receiving element 13 Image processing Device 14 Focus tracking signal generation device 15 Information processing device 16 Optical pickup 17 Position control interface 18 Optical pickup position adjusting means 19 Objective lens actuator position adjusting means 20 Objective lens actuator 21 Collimator lens position adjusting means 22 Lens array 23 Objective lens 24 Collimator Lens 25 Optical information medium 26 Spindle motor 27 Guide rail 28 Optical pickup 29 Lead screw 30 Seek motor 31 First objective lens 32 Second objective lens 33 Third beam splitter

Claims (14)

A laser light source;
An objective lens for condensing laser light generated from the laser light source onto an optical information medium;
In order to measure the wavefront aberration of the light emitted from the optical pickup including the objective lens actuator that drives the objective lens in the focus direction and the tracking direction,
A collimator lens that converts light emitted from the objective lens of the optical pickup into parallel light;
Wavefront aberration detection means for detecting wavefront aberration of light emitted from the optical pickup that has passed through the collimator lens;
In a wavefront aberration inspection apparatus having
The third-order coma aberration is corrected by subtracting a value obtained by multiplying the tilt component in the wavefront aberration of the optical pickup by a constant from the value of the third-order coma aberration in the wavefront aberration of the optical pickup detected by the wavefront aberration detector. A wavefront aberration inspection apparatus characterized by the above. A laser light source;
An objective lens for condensing laser light generated from the laser light source onto an optical information medium;
In order to measure the wavefront aberration of the light emitted from the optical pickup including the objective lens actuator that drives the objective lens in the focus direction and the tracking direction,
A collimator lens that converts light emitted from the objective lens of the optical pickup into parallel light;
Wavefront aberration detection means for detecting wavefront aberration of light emitted from the optical pickup that has passed through the collimator lens;
In a wavefront aberration inspection apparatus having
The fifth-order coma aberration is corrected by subtracting a value obtained by multiplying the tilt component in the wavefront aberration of the optical pickup by a constant from the value of the fifth-order coma aberration in the wavefront aberration of the optical pickup detected by the wavefront aberration detector. A wavefront aberration inspection apparatus characterized by the above. A laser light source;
An objective lens for condensing laser light generated from the laser light source onto an optical information medium;
In order to measure the wavefront aberration of the light emitted from the optical pickup including the objective lens actuator that drives the objective lens in the focus direction and the tracking direction,
A collimator lens that converts light emitted from the objective lens of the optical pickup into parallel light;
Wavefront aberration detection means for detecting wavefront aberration of light emitted from the optical pickup that has passed through the collimator lens;
In a wavefront aberration inspection apparatus having
Correction of third-order coma aberration is performed by subtracting a value obtained by multiplying a tilt component in the wavefront aberration of the optical pickup by a constant from the value of third-order coma aberration in the wavefront aberration of the optical pickup detected by the wavefront aberration detection means. ,further,
The fifth-order coma aberration is corrected by subtracting a value obtained by multiplying the tilt component in the wavefront aberration of the optical pickup by a constant from the value of the fifth-order coma aberration in the wavefront aberration of the optical pickup detected by the wavefront aberration detector. A wavefront aberration inspection apparatus characterized by the above. The value of the third-order coma aberration in the wavefront aberration of the optical pickup detected by the wavefront aberration detection means is CM3 ₀ [mλ], the tilt component in the wavefront aberration of the optical pickup is Tilt [mλ], and the third-order coma aberration is in order to correct, said the constant to be multiplied by the tilt component and k _1, 3-order coma CM3 [m [lambda] is the wave front aberration inspection apparatus according to claim 1 and 3, wherein satisfying the equation (1).

(Where ∂CM3 / ∂θ [mλ] is the off-axis coma aberration of the collimating lens that occurs at an angle of view of 1 °, λ [μm] is the wavelength of the optical pickup outgoing light, and NA is the numerical aperture of the optical pickup outgoing light. NA, f [mm] is the collimating lens focal length of the wavefront aberration inspection apparatus) The wavefront detected by the aberration detecting means, the value of the fifth-order coma aberration in the wavefront aberration of the optical pickup _{CM5 0 [mλ], Tilt [} mλ] the tilt component in the wavefront aberration of the optical pickup, the fifth-order coma aberration in order to correct, said the constant to be multiplied by the tilt component and k _1, 5-order coma aberration CM5 [m [lambda] is the wave front aberration inspection apparatus according to claim 2 and 3, wherein satisfies the equation (2).

(Where ∂CM5 / ∂θ [mλ] is the off-axis coma aberration of the collimating lens that occurs at an angle of view of 1 °, λ [μm] is the wavelength of the optical pickup outgoing light, and NA is the numerical aperture of the optical pickup outgoing light. NA, f [mm] is the collimating lens focal length of the wavefront aberration inspection apparatus) 6. The wavefront aberration inspection apparatus according to claim 1, wherein the wavefront aberration detecting means is a Mach-Zehnder interferometer. The wavefront aberration inspection device according to claim 1, wherein the wavefront aberration detection unit includes a lens array and a light receiving camera, and detects wavefront aberration by a Shack-Hartmann method. A laser light source;
An objective lens for condensing laser light generated from the laser light source onto an optical information medium;
To assemble and adjust an optical pickup including an objective lens actuator that drives the objective lens in a focus direction and a tracking direction,
A collimator lens for converting light emitted from the objective lens into parallel light of the optical pickup;
Wavefront aberration detection means for detecting wavefront aberration of light emitted from the optical pickup that has passed through the collimator lens;
In an optical pickup assembly adjusting device having an objective lens actuator adjusting means for holding the objective lens actuator and adjusting the position,
Correction of third-order coma aberration is performed by subtracting a value obtained by multiplying a tilt component in the wavefront aberration of the optical pickup by a constant from the value of third-order coma aberration in the wavefront aberration of the optical pickup detected by the wavefront aberration detection means. ,
An optical pickup assembling and adjusting device that adjusts the inclination of the objective lens actuator in a direction in which the third-order coma aberration obtained by the correction decreases. The value of the third-order coma aberration in the wavefront aberration of the optical pickup detected by the wavefront aberration detection means is CM3 ₀ [mλ], the tilt component in the wavefront aberration of the optical pickup is Tilt [mλ], and the third-order coma aberration is 9. The optical pickup assembling / adjusting apparatus according to claim 8, wherein the third-order coma aberration CM3 [mλ] satisfies (Equation 3), where k ₃ is a constant by which the tilt component is multiplied for correction.

(Where ∂CM3 / ∂θ [mλ] is the off-axis coma aberration of the collimating lens that occurs at an angle of view of 1 °, λ [μm] is the wavelength of the optical pickup outgoing light, and NA is the numerical aperture of the optical pickup outgoing light. NA, f [mm] is the collimating lens focal length of the optical pickup assembly adjustment device) 10. The optical pickup assembling / adjusting apparatus according to claim 8, wherein the wavefront aberration detecting means is a Mach-Zehnder interferometer. 10. The optical pickup assembling / adjusting apparatus according to claim 8, wherein the wavefront aberration detecting means includes a lens array and a light receiving camera, and detects wavefront aberration by a Shack-Hartmann method. 12. An optical pickup assembled and adjusted by the optical pickup assembling / adjusting apparatus according to claim 8. An optical disk drive using the optical pickup according to claim 12. 14. An optical information recording / reproducing apparatus using the optical disc drive according to claim 13.

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