JP2007026615A - Optical pickup and optical information processor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To record and reproduce information satisfactorily with the same RIM strength and without any loss of light quantity in the case of either of two optical recording media with different numerical apertures and different substrate thickness. <P>SOLUTION: An expander optical system 114 of a magnification converting means is composed of two lenses being lenses 114a and 114b and changes an interval between the lenses as to whether to record and reproduce an optical recording medium (BD) or an optical recording medium (HD). A liquid crystal aperture limiting element performs switching as to whether to perform aperture limitation or blind transmission in accordance with a medium. Although NA0. 85 and NA0. 65 are switched by switching incident luminous flux diameters ϕ1 and ϕ2 to an objective lens 109, the expander optical system 114 having same luminous flux diameters ϕ3 and ϕ4 (ϕ3=ϕ4) at incidence of the expander optical system 114 between the two media of luminous fluxes passing through ϕ1 and ϕ2 is adopted. The expander optical system 114 is used to make light utilization efficiency and RIM strength equal in the case of the optical recording medium (BD) and the optical recording medium (HD). <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention is an optical pickup for recording and reproducing two optical recording media having different numerical apertures and substrate thicknesses. There is no loss of light amount in any of the two media, and the RIM intensity (relative to the optical intensity at the center of the lens) The present invention relates to an optical pickup and an optical information processing apparatus in which the ratio of the light intensity at the lens outer edge is the same and information can be recorded and reproduced satisfactorily.

  As means for storing video information, audio information, or data on a computer, optical recording media such as a CD with a recording capacity of 0.65 GB and a DVD with a recording capacity of 4.7 GB are becoming widespread. In recent years, there has been an increasing demand for further improvement in recording density and increase in capacity.

  As means for increasing the recording density of such an optical recording medium, in an optical pickup for writing or reading information on the optical recording medium, the numerical aperture (hereinafter referred to as NA) of the objective lens is increased, or the light source It is effective to reduce the diameter of the beam spot that is collected by the objective lens and formed on the optical recording medium by shortening the wavelength.

  Therefore, for example, in the “CD optical recording medium”, the NA of the objective lens is 0.50 and the wavelength of the light source is 780 nm, whereas the recording density is higher than that of the “CD optical recording medium”. In the “DVD optical recording medium”, the NA of the objective lens is 0.65 and the wavelength of the light source is 660 nm. As described above, the optical recording medium is desired to further improve the recording density and increase the capacity. For this purpose, the NA of the objective lens is set to be larger than 0.65 or the wavelength of the light source is increased. It is desired to make it shorter than 660 nm.

  Two standards have been proposed for such a large-capacity optical recording medium and optical information processing apparatus. One is a standard of “Blu-ray Disc” that satisfies the capacity securing of 22 GB by using a light source in a blue wavelength region and an objective lens of NA 0.85 as described in Non-Patent Document 1. Hereinafter referred to as BD). The other is the “HD-DVD” standard which has the same blue wavelength as described in Non-Patent Document 2, but satisfies a capacity of 20 GB using an objective lens of NA 0.65. (Hereinafter referred to as HD).

The former increases the capacity by shortening the wavelength and increasing the NA, compared to the DVD system, and the latter allows the linear recording density to be improved by improving signal processing instead of increasing the NA. To increase the capacity by narrowing the track pitch.
Japanese Patent Laid-Open No. 10-020623 Japanese Patent No. 3036314 Manju Oku, 8 other people, “What Blu-ray Disc aims”, Nikkei Electronics, No. 2003.03.31, p.135-150 Naoshi Yamada, 4 others, “Next generation specification“ HD DVD ”born from DVD”, Nikkei Electronics, 2003.10.13, p.125-134

  Thus, the two standards using a light source in the blue wavelength band have been proposed. However, as a user, it is desirable that these two standards of optical recording media can be handled by the same optical information processing apparatus without distinction.

  As the simplest method, there is a method of mounting a plurality of optical pickups. However, with this method, it is difficult to achieve downsizing and cost reduction. Therefore, an optical pickup that can perform recording or reproduction with a common light source and a common objective lens for two blue standards having different substrate thicknesses and NAs is desired.

  For example, FIG. 17 is a diagram showing a schematic configuration of an optical pickup that performs recording or reproduction on two types of optical recording media having different light sources and substrate thicknesses with one light source and one objective lens. The light beam emitted from the semiconductor laser 101 is converted into parallel light by the collimator lens 102, and reaches the liquid crystal aberration correction element 106 through the polarization beam splitter 103 and the deflection prism 105. Here, the spherical aberration caused by the difference in substrate thickness is corrected. Further, the liquid crystal shutter 107 continues, and the NA is switched here. That is, when the numerical aperture used is NA 0.85, the entire surface is transmitted, and when it is NA 0.65, the peripheral portion is shielded and only the light flux of the central portion of NA 0.65 is transmitted.

  The light beam that has passed through the liquid crystal aberration correction element 106 and the liquid crystal shutter 107 enters the objective lens 109 and is condensed as a minute spot on the optical recording medium (BD) 110a and the optical recording medium (HD) 110b. Information is reproduced, recorded or erased by this spot. The light reflected from the optical recording medium (BD) 110 a and the optical recording medium (HD) 110 b is reflected by the polarization beam splitter 103, converged by the detection lens 111, and reaches the light receiving element 112. An information signal and a servo signal are detected from the light receiving element 112. However, the following two problems exist in such a configuration.

・ Problem 1. Light utilization efficiency loss at NA 0.65 In the case of NA 0.65, most of the light is shielded by the liquid crystal shutter, resulting in a loss of light amount. In order to compensate for this loss of light quantity, it is necessary to increase the output of the light source, leading to higher costs.

・ Problem 2. Decrease in RIM intensity at NA 0.85 In case of NA 0.85, RIM intensity decreases. The light beam incident on the aperture stop (aperture) of the objective lens is generally a so-called Gaussian beam whose cross-sectional light intensity exhibits a Gaussian distribution, but its RIM range is generally defined to be around 50%. If the RIM intensity is deviated, the focused spot on the optical recording medium changes, which may make it difficult to record and reproduce the information recording signal. For this reason, when an RIM intensity of about 50% is ensured with an NA 0.65 optical recording medium, the RIM intensity is insufficient with respect to an NA 0.85 optical recording medium. If an attempt is made to secure the required RIM intensity for an optical recording medium with NA 0.85, the RIM intensity will be excessive for an optical recording medium with NA 0.65, and the coupling efficiency will be reduced as in the above-mentioned problem 1. Incurs a decline.

  The present invention is directed to solving the problems of the prior art, and even if spherical aberration is corrected by passing a light beam incident on the objective lens through an expander optical system in advance, the aperture of the objective lens Light for recording / reproducing on two optical recording media having different NA and substrate thickness so that the amount of light incident on the aperture (aperture) is always kept constant and the “rim intensity (RI)” is not changed. An object of the present invention is to provide an optical pickup and an optical information processing apparatus that can perform recording and reproduction of information satisfactorily with no loss of light amount and the same RIM intensity in any of the two media.

  In order to achieve the above object, an optical pickup according to a first aspect of the present invention includes a first optical recording medium having a wavelength λ1, a substrate thickness t1, a used numerical aperture NA1, a wavelength λ1, a substrate thickness t2 ( > T1) In an optical pickup that records and / or reproduces information with respect to a second optical recording medium having a numerical aperture NA2 (<NA1), a light source and a light beam emitted from the light source are collected on the optical recording medium The degree of convergence or divergence of the incident light beam to the objective lens is switched according to the objective lens and the medium type to minimize the spherical aberration of the light beam condensed on the first and second optical recording media. The numerical aperture and the substrate thickness are different depending on the configuration in which the outermost peripheral light beam diameters of the light beams acting on the first and second optical recording media are congruent when entering the magnification conversion means. Each of the two optical recording media On the other hand, an optical pickup that can collect light with the best RIM intensity without loss of light utilization efficiency has a simple configuration of one light source and one objective lens, and an optical pickup with stable aberration characteristics can be realized.

  The optical pickup according to claim 2 includes a first optical recording medium having a wavelength λ1, a substrate thickness t1, a used numerical aperture NA1, a wavelength λ1, a substrate thickness t2 (> t1), a used numerical aperture NA2 (<NA1 In the optical pickup for recording and / or reproducing information on the second optical recording medium, the light source, the objective lens for condensing the emitted light beam from the light source on the optical recording medium, and the type of the medium And a magnification conversion means for switching the degree of convergence or divergence of the incident light beam to the objective lens and minimizing the spherical aberration of the light beam condensed on each of the first and second optical recording media. In the expander optical system, the outermost peripheral light beam diameter of each light beam acting on the first and second optical recording mediums is the same when the expander optical system is incident. Two with different thickness For each of the above optical recording media, an optical pickup capable of condensing with the best RIM intensity without loss of light utilization efficiency has a simple configuration of one light source and one objective lens, and is further extracted as a magnification conversion means. By using a panda optical system, a small optical pickup with stable aberration characteristics can be realized.

  The optical pickup described in claim 3 includes a first optical recording medium having a wavelength λ1, a substrate thickness t1, a used numerical aperture NA1, a wavelength λ1, a substrate thickness t2 (> t1), a used numerical aperture NA2 (<NA1 In the optical pickup for recording and / or reproducing information on the second optical recording medium, the light source, the objective lens for condensing the emitted light beam from the light source on the optical recording medium, and the type of the medium The polarization plane switching element that selectively switches the polarization direction of the luminous flux and the degree of convergence or divergence of the incident luminous flux to the objective lens according to the switching of the polarization plane switching element, and the first and second light Magnification conversion means for minimizing the spherical aberration of the light beam condensed on each recording medium, and the magnification conversion means is a diffractive optical element and acts on light collection on the first and second optical recording media. The outermost luminous flux diameter of each luminous flux is Since the magnification conversion means is a passive optical element, the optical pickup having a degree of freedom in arrangement position can be realized because the magnification conversion means is a passive optical element due to the coincident configuration when the diffraction element is incident.

  The optical pickup described in claim 4 includes a first optical recording medium having a wavelength λ1, a substrate thickness t1, a used numerical aperture NA1, a wavelength λ1, a substrate thickness t2 (> t1), a used numerical aperture NA2 (<NA1 In the optical pickup for recording and / or reproducing information on the second optical recording medium, the light source, the objective lens for condensing the emitted light beam from the light source on the optical recording medium, and the type of the medium The magnification conversion means for switching the degree of convergence or divergence of the incident light beam on the objective lens and minimizing the spherical aberration of the light beam condensed on each of the first and second optical recording media. The liquid crystal element has a configuration in which the outermost peripheral light beam diameters of the light beams acting on the light condensing on the first and second optical recording media coincide with each other when the liquid crystal element is incident. Small and thin by using An optical pickup that can be molded can be realized.

  An optical pickup according to a fifth aspect is the optical pickup according to any one of the first to fourth aspects, wherein the numerical aperture NA1 of the first optical recording medium is 0.85 and the numerical aperture of the second optical recording medium. When NA2 is 0.65 and the recording speed of the first optical recording medium is α, the required light source emission amount is A, and when the recording speed of the second optical recording medium is β, the required light source emission amount is When B, the following (Equation 1)

の関係を満足するように、選択した光記録媒体および記録速度に応じて光源発光量を切り換える構成によって、各媒体における使用開口数ＮＡ０.６５とＮＡ０.８５の差異に伴う、必要な光量補正がなされた光ピックアップを実現できる。

In order to satisfy the above relationship, the light source emission amount is switched according to the selected optical recording medium and the recording speed, so that the necessary light amount correction associated with the difference between the used numerical apertures NA 0.65 and NA 0.85 can be achieved. The optical pickup made can be realized.

  An optical information processing apparatus according to claim 6 is an optical information processing apparatus that performs at least one of recording, reproduction, and erasing of information on an optical recording medium. According to the configuration using the optical pickup described in item 1, information can be recorded, reproduced, and erased from one optical pickup medium with different information recording layers.

  According to the present invention, the magnification conversion means for correcting spherical aberration is provided in order to ensure compatibility between two recording media having different numerical apertures and substrate thicknesses. The strength is also the same, and there is an effect that information can be recorded and reproduced on the recording medium satisfactorily.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In this embodiment, the first optical recording medium is a “blue-based optical recording medium having a working wavelength of 405 nm, NA of 0.85, and a light irradiation side substrate thickness of 0.1 mm (hereinafter referred to as an optical recording medium (BD))”. And the second optical recording medium “blue optical recording medium (hereinafter referred to as optical recording medium (HD)) having a working wavelength of 405 nm, NA of 0.65, and a light irradiation side substrate thickness of 0.6 mm” can be recorded or reproduced. The optical pickup will be described.

  FIG. 1 is a diagram showing a schematic configuration of an optical pickup according to Embodiment 1 of the present invention. Here, components having substantially the same functions corresponding to the components described in FIG. 17 showing the conventional example are given the same reference numerals, and the same applies to the following drawings.

  1 includes a semiconductor laser 101 having a wavelength of 405 nm, a collimating lens 102, a polarizing beam splitter 103, an expander optical system 114, a deflecting prism 105, a liquid crystal aperture limiting element 116, a quarter wavelength plate 117, An objective lens 109, a detection lens 111, and a light receiving element 112 are included.

  Further, as described above, the optical recording medium (BD) 110a and the optical recording medium (HD) 110b have different substrate thicknesses as described above, and only one of the optical recording media is not shown during recording or reproduction. Set to high speed.

  First, the case where the optical recording medium (BD) 110a is recorded or reproduced in the optical pickup shown in FIG. 1 will be described. The linearly polarized divergent light emitted from the semiconductor laser 101 having a wavelength of 405 nm is converted into substantially parallel light by the collimator lens 102, transmitted through the polarization beam splitter 103, converted into predetermined convergent light by the expander optical system 114, and deflected. The optical path is deflected by 90 degrees by the prism 105, passes through the liquid crystal aperture limiting element 116 insensitively, passes through the quarter-wave plate 117, becomes circularly polarized light, enters the objective lens 109, and enters the optical recording medium (BD) 110a. It is condensed as a minute spot. Information is reproduced, recorded or erased by this spot.

  The objective lens 109 is installed on an actuator 108a having a movable function such as focus and tracking, and is limited to NA 0.85 by an opening 108b provided in the actuator 108a. The light reflected from the optical recording medium (BD) 110a passes through the quarter-wave plate 117 and becomes circularly polarized light in the opposite direction to the forward path. After passing through the expander optical system 114, the light is converted into substantially parallel light again. The light becomes orthogonal linearly polarized light, is reflected by the polarization beam splitter 103, is converged by the detection lens 111, and reaches the light receiving element 112. An information signal and a servo signal are detected from the light receiving element 112.

  Next, a case where the optical recording medium (HD) 110b is recorded or reproduced will be described. The linearly polarized divergent light emitted from the semiconductor laser 101 having a wavelength of 405 nm is converted into substantially parallel light by the collimator lens 102, transmitted through the polarization beam splitter 103, converted into predetermined convergent light by the expander optical system 114, and deflected. The optical path is deflected by 90 degrees by the prism 105, restricted to NA 0.65 by the liquid crystal aperture limiting element 116, passes through the quarter-wave plate 117, becomes circularly polarized light, enters the objective lens 109, and is an optical recording medium (HD) It is condensed as a minute spot on 110b. Information is reproduced, recorded or erased by this spot.

  The light reflected from the optical recording medium (HD) 110b passes through the quarter-wave plate 117 and becomes circularly polarized light in the direction opposite to the forward path, and after passing through the expander optical system 114, is again made substantially parallel light. The light becomes orthogonal linearly polarized light, is reflected by the polarization beam splitter 103, is converged by the detection lens 111, and reaches the light receiving element 112. An information signal and a servo signal are detected from the light receiving element 112.

  The expander optical system 114, which is a magnification conversion means, is composed of two lenses 114a and 114b, and the lens depends on which of the optical recording medium (BD) and optical recording medium (HD) is recorded and reproduced. The interval is changed. The liquid crystal aperture limiting element 116 also switches between aperture limitation and insensitive transmission according to the medium.

  FIG. 2 is a graph showing the relationship between the substrate thickness and the divergence of a general objective lens. The horizontal axis represents the thickness of the substrate, and the vertical axis represents the magnification of the objective lens in use as a function of the divergence of the light beam incident on the objective lens. Since the light beam emitted from the objective lens toward the substrate is always convergent light, the sign when the convergent light is incident on the objective lens is “+”, and the sign when the divergent light is incident is “−”. When this magnification is “0”, parallel light enters the objective lens. The curves in FIG. 2 are obtained by connecting magnifications that minimize wavefront aberration to each substrate thickness. For example, when the parallel light incidence is best at the substrate thickness B, “−”, that is, divergent light increases as the substrate thickness increases. It is generally known that as the thickness becomes thinner, “+”, that is, when the convergent light is incident, the aberration becomes smaller, and FIGS. 3A and 3B are examples. In the case of the optical recording medium (BD) 110a shown in FIGS. 3A and 3B, convergent light is incident, and in the case of the optical recording medium (HD) 110b, the light converges more slowly than in the case of the optical recording medium (BD) 110a. An objective lens shape that gives the best aberration when incident is obtained. Such switching of the degree of convergence is performed according to the determination of the type of optical recording medium.

  As a method for discriminating the recording medium, at the stage of setting the optical recording medium, a thickness detecting optical system comprising an LED and a light receiving element is provided, and discriminating is based on the output. Further, a focus error signal is detected, and a determination is made based on whether or not a track error signal is detected in the vicinity of the focus. Also, the cartridge shape of the optical recording medium is set to be different, and the determination is made based on the difference. Further, the medium type is printed on a barcode described on the label of the optical recording medium, and the information is determined by reading the information with a barcode reader. Further, the determination is made based on the movable amount of the objective lens actuator up to the in-focus position. There are several methods mentioned above.

  Next, the configuration of the expander optical system 114 will be described. As shown in FIGS. 3A and 3B, the expander optical system 114 has a two-group configuration of two lenses. When the light source side is the lens 114a and the optical recording medium side is the lens 114b, the lens 114a is positive. The lens 114b is a lens having a negative refractive power, and both are single lenses. Both lenses are arranged on the optical axis of the emitted light beam emitted from the light source toward the optical recording medium. The lens of the expander optical system 114 is installed in movable actuator means (not shown).

  As the actuator means, a generally known voice coil type actuator, piezoelectric actuator, or the like may be used. Further, as a method of switching the magnification, that is, a method of driving the lens, a method in which a stopper is provided in the movable range of the driving lens and switching in two steps may be performed, and a means for detecting the position of the driving lens is provided. Thus, the lens best position for each medium may be stored in advance in a memory, and the lens position may be moved according to the medium discrimination. Alternatively, the driving lens position may be searched and fed back so that the RF signal or the track error (TE) signal is maximized. The driving lens may be one lens or both lenses. May be.

  As the liquid crystal aperture limiting element 116 shown in FIG. 1, the optical recording medium (BD) 110a and the optical recording medium (HD) 110b have different numerical apertures from NA 0.85 and NA 0.65, respectively, and the optical recording medium (BD) 110a. When the light is condensed, the aperture 108b of the actuator 108a is limited to NA 0.85, and when the optical recording medium (HD) 110b is condensed, it is limited to NA 0.65 by the liquid crystal aperture limiting element 116.

  The liquid crystal aperture limiting element 116 may be a liquid crystal element that functions as a selective annular light shielding filter as shown in FIG. That is, it is composed of a liquid crystal shutter having an annular pattern, and transmits or shields the outer periphery of the light beam incident on the objective lens 109. As shown in FIGS. 4B and 4C, when no voltage is applied, that is, when the liquid crystal is off, the entire surface is transmitted, and when a voltage is applied, that is, when the liquid crystal is on, it is partially transmitted. An element that transmits light may be used.

  Here, specific numerical examples regarding the shapes of the objective lens 109 and the expander optical system 114 as shown in FIGS.

  The aspherical shape of the lens surface includes: optical axis direction coordinate: X, optical axis orthogonal direction coordinate: Y, paraxial radius of curvature: R, conic constant: K, higher order coefficients: A, B, C, D, Using E, F,..., The well-known aspherical expression is (Expression 2)

で表される。

It is represented by

  The configuration of the optical system according to the first embodiment will be described with reference to FIGS. 3 (a), 3 (b), and 5. FIG. As shown in FIG. 5, the objective lens 109 has a working wavelength: 405 nm, NA: 0.85, f: 1.765 mm, nd: 1.694, and νd: 53.2. Symbols in FIG. It is as follows. “OBJ” means an object point (semiconductor laser as a light source), but the incident light beam to the expander optical system 114 is “infinite system”, and “INFINITY (infinity) with a radius of curvature: RDY and a thickness: THI. ) "Means that the light source is at infinity. Unless otherwise specified, the unit of the quantity having the dimension of length is “mm”.

  “S1” to “S4” represent lens surfaces of the expander optical system 114, “S1” represents the light source side surface of the lens 114a of the expander optical system 114, and “S2” represents the objective lens side surface. The thickness of “S1” of 2.00 mm means the thickness of the lens 114a. The thickness of “S2” of 1.9 mm / 4.1 mm represents the distance between the lenses of the expander optical system 114, 1.9 mm is for the optical recording medium (BD) 110a, and 4.1 mm is This is the case of the optical recording medium (HD) 110b. “S6” means the light source side surface of the objective lens 109 of the optical pickup, and “S7” means the side surface of the optical recording medium.

  The thickness of the objective lens 109 in the first embodiment is 2.90 mm, and the thickness of 0.51 mm / 0.12 mm described on the right side of the radius of curvature in the column “S8” is the optical recording medium (BD), “Working distance: WD” of each optical recording medium (HD) is shown. “S8” is a light source side surface of the light irradiation side substrate of the optical recording medium (BD) and the optical recording medium (HD), and “S9” is a surface matching the recording surface. These surfaces “S8” and “S9” , That is, the substrate thickness is 0.1 mm for the optical recording medium (BD) 110a, 0.6 mm for the optical recording medium (HD) 110b, nd: 1.551610, and νd: 64.1. “WL: Wavelength” represents a used wavelength (405 nm).

  The on-axis wavefront aberration of the system combining the obtained objective lens 109 and the expander optical system 114 is 0.0026 λrms for the system for recording / reproducing the optical recording medium (BD) 110a, and the optical recording medium (HD) 110b is recorded. The reproducing system is 0.0007 λrms, which is suppressed to the Marshall limit of 0.07 λrms or less.

  In FIGS. 3A and 3B, NA 0.85 and NA 0.65 are switched by switching the incident light beam diameters φ1 and φ2, but in the first embodiment, they pass φ1 and φ2. An expander optical system 114 is used in which the expander optical system 114 has incident light beam diameters φ3 and φ4 of the same diameter (φ3 = φ4) between the two mediums. By using such an expander optical system 114, the light use efficiency and the RIM intensity can be made the same in the case of the optical recording medium (BD) and the optical recording medium (HD).

  In the first embodiment described above, the expander optical system 114 uses the lens 114a having a positive refractive power on the light source side and corrects the aberration by using the lens 114b having a negative refractive power on the optical recording medium side. However, depending on the configuration of the optical system, the reverse may be used. Specifically, the optical pickup as a whole can be downsized. As described above, the expander optical system 114 is preferably a galley type expander composed of two lenses having different powers. The Kepler type expander in which two positive lenses are arranged with their focal lengths overlapped with each other requires an optical path length and does not meet the requirements of an optical pickup for which a downsized optical system is desired. It is generally known that if an attempt is made to design a small Kepler type expander, the total focal length has to be shortened too much because the optical path length is shortened, and good aberration cannot be obtained.

  The expander optical system 114 may also serve as a collimating lens. In this case, the number of parts can be reduced, and the labor and cost of manufacturing the optical pickup can be reduced.

  Furthermore, in Embodiment 1 described above, a single lens is used as the objective lens 109, but a bonded lens or the like may be used, or a lens composed of two or more groups of lenses may be used. Good. In the description of the first embodiment, an optical system having a light source wavelength of 405 nm is exemplified, but the wavelength used is not limited to this, and the effect is not changed at other wavelengths.

  FIG. 6 is a diagram showing a schematic configuration of the optical pickup according to Embodiment 2 of the present invention. The second embodiment is different from the first embodiment in that a diffractive magnification conversion element is used as a magnification conversion unit instead of the expander optical system of the first embodiment.

  The main parts of the optical pickup shown in FIG. 6 are a semiconductor laser 101 having a wavelength of 405 nm, a collimator lens 102, a polarization plane switching element 104, a half mirror 103a, a deflection prism 105, a diffractive magnification conversion element 115, and a polarization selective aperture limiting element 116a. , Objective lens 109, detection lens 111, and light receiving element 112.

  First, the case where the optical recording medium (BD) 110a is recorded or reproduced in the optical pickup shown in FIG. 6 will be described. The linearly polarized divergent light emitted from the semiconductor laser 101 having a wavelength of 405 nm is converted into substantially parallel light by the collimator lens 102, the polarization direction is rotated by 90 ° in the plane perpendicular to the paper surface by the polarization plane switching element 104, and transmitted through the half mirror 103a. The deflecting prism 105 deflects the optical path by 90 degrees, and the diffractive magnification conversion element 115 generates a predetermined convergent light. The polarization selective aperture limiting element 116a passes through the dead zone, enters the objective lens 109, and the optical recording medium ( BD) is condensed as a minute spot on 110a. Information is reproduced, recorded or erased by this spot. The objective lens 109 is installed on an actuator 108a having a movable function such as focusing and tracking, and is limited to NA 0.85 by an opening 108b provided in the actuator 108a. The light beam reflected from the optical recording medium (BD) 110 a is converted into substantially parallel light again by the diffractive magnification conversion element 115, reflected by the half mirror 103 a, converged by the detection lens 111, and reaches the light receiving element 112. An information signal and a servo signal are detected from the light receiving element 112.

  Next, a case where the optical recording medium (HD) 110b is recorded or reproduced will be described. The linearly polarized divergent light emitted from the semiconductor laser 101 having a wavelength of 405 nm is converted into substantially parallel light by the collimator lens 102, is transmitted as it is without being rotated in the polarization direction by the polarization plane switching element 104, and is transmitted through the half mirror 103a. The optical path is deflected by 90 degrees by the deflecting prism 105, the light is converted into a predetermined convergent light by the diffractive magnification conversion element 115, is restricted to NA 0.65 by the polarization selective aperture limiting element 116a, and enters the objective lens 109. Focused as a minute spot on (HD) 110b. Information is reproduced, recorded or erased by this spot. The light reflected from the optical recording medium (HD) 110 b is converted into substantially parallel light again by the diffractive magnification conversion element 115, reflected by the half mirror 103 a, converged by the detection lens 111, and reaches the light receiving element 112. An information signal and a servo signal are detected from the light receiving element 112.

  This diffractive magnification conversion element 115 is formed of a polarization-selective diffraction grating and a polarization-independent diffraction grating. Whether the optical recording medium (BD) or the optical recording medium (HD) performs recording or reproduction. The polarization plane is switched, and the degree of diffraction is switched according to the polarization direction of the transmitted light of the polarization plane switching element 104. The polarization selective aperture limiting element 116a can also switch between aperture limiting and insensitive transmission depending on the recording medium, depending on the polarization direction of the incident light.

  Here, the polarization plane switching element 104 that switches the polarization direction of the light beam emitted from the light source according to the recording medium, and the reflection, diffraction, and absorption according to the polarization direction, provided in the optical pickup of the second embodiment. The polarization selective aperture limiting element 116a that switches the beam diameter using any one of the optical characteristics will be described as an example of performing aperture limitation by transmission / reflection.

  As the polarization plane switching element 104, a TN (twisted nematic) type liquid crystal may be used. A TN type liquid crystal is generally known to rotate the polarization direction of a liquid crystal when a voltage is applied, and to transmit insensitively when no voltage is applied.

  As the polarization selective aperture limiting element 116a, for example, a means for switching the beam diameter by transmission / reflection as shown in FIGS. 7A and 7B may be used according to the polarization direction. The polarization selective aperture limiting element 116a has a structure shown in FIG. That is, the polarizing film 24a is sandwiched between the transparent glasses 24b and transmits a light beam polarized in a specific direction. The transparent glass 24b may be a highly transparent resin. That is, the polarization selective aperture limiting element 116a transmits only the light beam polarized in a specific direction by the polarizing film 24a at the outer peripheral portion.

  In the case of an optical recording medium (BD), as shown in FIG. 9A, no voltage is applied to the polarization plane switching element 104 which is a TN type liquid crystal. As a result, the light beam polarized in the direction parallel to the paper surface exiting from the collimating lens 102 is polarized in a direction perpendicular to the paper surface by changing the polarization direction by 90 degrees by the polarization surface switching element 104 composed of a TN type liquid crystal. The polarization selective aperture limiting element 116a transmits the light without being shielded, proceeds in the direction of the objective lens 109, and is limited to NA 0.85 by the opening 108b formed in the actuator 108a.

  In the case of an optical recording medium (HD), a voltage is applied to the TN liquid crystal. As a result, the light beam polarized in the direction parallel to the paper surface exiting from the collimating lens 102 is transmitted without changing the polarization direction by the TN liquid crystal (polarization plane switching element 104), and is surrounded by the polarization selective aperture limiting element 116a. Only the light beam that has been shielded from light and transmitted through the inner periphery enters the objective lens 109.

  In the second embodiment, the polarization plane switching element 104 is between the collimating lens 102 and the half mirror 103a, but may be between the half mirror 103a and the diffractive magnification conversion element 115. In FIG. 8B, a circular through hole is formed on the inner peripheral side, but it is not always necessary to have a circular shape, and an elliptical shape may be used.

  Next, the operation of the diffractive magnification conversion element 115 arranged in front of the polarization selective aperture limiting element 116a will be described with reference to FIGS. 10 (a), (b), and (c). FIGS. 10A and 10B illustrate only the objective lens 109 and the diffractive magnification conversion element 115 in order to explain the diffractive magnification conversion element 115, but in reality, a polarization selective aperture is interposed therebetween. A limiting element 116a and an opening 108b are present.

  The diffractive magnification conversion element 115 is formed with a diffraction grating 25a independent of polarization and polarization-selective diffraction gratings 25c and 25e. In the case of the optical recording medium (BD) 110a, diffraction independent of polarization is used. The light is converged by the grating 25a, and the polarization-selective diffraction gratings 25c and 25e are transmitted through the dead zone and enter the objective lens 109 (see FIG. 10A). On the other hand, in the case of the optical recording medium (HD) 110b, a light beam having a polarization direction orthogonal to that of the optical recording medium (BD) 110a enters, and is first converged and diffracted by the diffraction grating 25a that does not depend on the polarization, and then selected for polarization selection. The diffraction grating 25c is further diffracted by the first surface, and the second surface of the diffraction grating 25e is diffracted in the direction of decreasing the convergence power (see FIG. 10B). Each of the diffraction gratings 25a, 25c, and 25e is a concentric pattern as shown in FIG. However, the period (pitch) varies depending on the required diffraction angle. The larger the diffraction angle, the narrower the pitch.

  In addition, the diffractive magnification conversion element 115 has surfaces of diffraction gratings 25c and 25e, which are birefringent media, so as to sandwich the isotropic medium 25d, and a glass substrate 25b and a glass substrate disposed so as to sandwich the outside thereof. 25f. The birefringent medium is formed in a sawtooth shape so that a large number of concentric circles are formed from the center to the circumference. The isotropic medium has a complementary shape to the birefringent medium, and is in close contact with the surface of the birefringent medium formed in a sawtooth shape. The cross-sectional shape is not limited to this, and may be a surface whose height changes stepwise.

  The birefringent medium has refractive indices of no_405 and ne_405 according to the polarization direction of the incident light beam. Here, no represents the refractive index (normal refractive index) for ordinary light, and ne represents the refractive index (abnormal light refractive index) for extraordinary light. Here, a case where a diffractive optical element is manufactured by selecting an isotropic medium and a birefringent medium so that the refractive indexes n1_405 and ne_405 of the isotropic medium are equal to each other will be considered.

  For the optical recording medium (BD), the polarization direction of the light beam is made equal to the polarization direction of the extraordinary ray and incident. Then, since the refractive index is the same between the isotropic medium and the birefringent medium, the light beam having a wavelength of 405 nm is transmitted without any influence. On the other hand, the optical recording medium (HD) is a light beam polarized in a direction perpendicular to the optical recording medium (BD) (ordinary ray polarization direction). When the light beam is incident, the refractive index becomes different between the isotropic medium and the birefringent medium. Therefore, diffraction occurs due to the shape of the boundary surface between the isotropic medium and the birefringent medium of the diffractive optical element, and the traveling path is changed. At this time, if the depth of the diffraction grating is appropriately adjusted, the diffraction efficiency of the light beam at the time of recording / reproducing of the optical recording medium (BD) can be maximized. In other words, the problem of light loss can be solved.

The birefringent material may be formed of optical crystals such as calcite, LiNbO ₃ , LiTaO ₃ . Alternatively, it may be formed of a polymer liquid crystal obtained by polymerizing and curing a liquid crystal, or a polymer material such as polycarbonate that exhibits birefringence by uniaxial stretching.

  In FIGS. 10A and 10B, NA 0.85 and NA 0.65 are switched by switching the incident light beam diameters φ1 and φ2. In the second embodiment, the light beams passing through φ1 and φ2 are used. The diffractive magnification conversion element 115 in which the light flux diameters φ3 and φ4 when incident on the diffractive magnification conversion element 115 between the two media has the same diameter (φ3 = φ4) is employed. If such a diffractive magnification conversion element 115 is used as a diffraction grating for switching the degree of divergence of the incident light beam of the objective lens 109 according to the polarization direction of the polarization plane switching element 104, an optical recording medium (BD), an optical recording medium ( In the case of HD), the light use efficiency and the RIM intensity can be made the same.

  FIG. 11 is a diagram showing a schematic configuration of an optical pickup according to Embodiment 3 of the present invention. The difference between the third embodiment and the first and second embodiments is that a liquid crystal magnification conversion element is used as the magnification conversion means.

  11 includes a semiconductor laser 101 having a wavelength of 405 nm, a collimating lens 102, a polarizing beam splitter 103, a deflecting prism 105, a liquid crystal magnification conversion element 115a, a liquid crystal aperture limiting element 116, a quarter wavelength plate 117, An objective lens 109, a detection lens 111, and a light receiving element 112 are included.

  First, the case where the optical recording medium (BD) 110a is recorded or reproduced in the optical pickup shown in FIG. 11 will be described. The linearly polarized divergent light emitted from the semiconductor laser 101 having a wavelength of 405 nm is converted into substantially parallel light by the collimator lens 102, passes through the polarization beam splitter 103, is deflected by 90 degrees in the optical path by the deflecting prism 105, and is converted into a liquid crystal magnification conversion element 115a. , The light is transmitted through the liquid crystal aperture limiting element 116 through the dead band, passes through the quarter-wave plate 117 and is circularly polarized, enters the objective lens 109, and is a minute spot on the optical recording medium (BD) 110a. It is condensed as. Information is reproduced, recorded or erased by this spot. The objective lens 109 is installed on an actuator 108a having a movable function such as focusing and tracking, and is limited to NA 0.85 by an opening 108b provided in the actuator 108a. The light beam reflected from the optical recording medium (BD) 110a passes through the quarter-wave plate 117 and becomes circularly polarized light in the opposite direction to the forward path, and is converted into substantially parallel light again in the liquid crystal magnification conversion element 115a, and is orthogonal to the forward path. It becomes linearly polarized light, reflected by the polarization beam splitter 103, converged light by the detection lens 111, and reaches the light receiving element 112. An information signal and a servo signal are detected from the light receiving element 112.

  Next, a case where the optical recording medium (HD) 110b is recorded or reproduced will be described. The linearly polarized divergent light emitted from the semiconductor laser 101 having a wavelength of 405 nm is converted into substantially parallel light by the collimator lens 102, passes through the polarization beam splitter 103, is deflected by 90 degrees in the optical path by the deflecting prism 105, and is converted into a liquid crystal magnification conversion element 115a. , And is limited to NA 0.65 by the liquid crystal aperture limiting element 116, passes through the quarter-wave plate 117, becomes circularly polarized light, enters the objective lens 109, and enters the optical recording medium (HD) 110 b. Is condensed as a minute spot. Information is reproduced, recorded or erased by this spot. The light beam reflected from the optical recording medium (HD) 110b passes through the quarter-wave plate 117 and becomes circularly polarized light in the direction opposite to the forward path, and is converted into substantially parallel light again in the liquid crystal magnification conversion element 115a, and is orthogonal to the forward path. It becomes linearly polarized light, reflected by the polarization beam splitter 103, converged light by the detection lens 111, and reaches the light receiving element 112. An information signal and a servo signal are detected from the light receiving element 112.

  FIG. 12 is a cross-sectional view showing a schematic configuration of the liquid crystal magnification conversion element, and its operation will be described with reference to FIG. The liquid crystal magnification conversion element 115a includes a diffraction grating 26 that does not depend on voltage application of the liquid crystal, and a liquid crystal diffraction grating that includes a liquid crystal 34 and diffraction gratings 27 and 28 that can be switched between diffraction and non-diffraction by voltage application. In the case of an optical recording medium (BD), the light is converged by the diffraction grating 26, and the liquid crystal diffraction grating passes through the dead zone as the liquid crystal is turned off and enters the objective lens. On the other hand, in the case of an optical recording medium (HD), it is first converged and diffracted by the diffraction grating 26, and then diffracted by the liquid crystal diffraction grating which is liquid crystal on. The liquid crystal diffraction grating has two diffraction gratings 27 and 28, which are sequentially diffracted and diffracted in the direction of decreasing the convergent power. The planes of the diffraction gratings 26, 27, and 28 are all the same concentric pattern as the plan view of FIG. However, the period (pitch) varies depending on the required diffraction angle. The larger the diffraction angle, the narrower the pitch.

  Next, the configuration of the liquid crystal magnification conversion element 115a will be described with reference to FIG. Glass substrates 31 and 32 are bonded by a conductive spacer 33 to form a liquid crystal cell. On the inner surface of the glass substrate 31, the electrode 35, the insulating film 37, and the alignment film 38 are arranged in this order from the inner surface. On the inner surface of the glass substrate 32, the electrode 36, the insulating film 37, and the alignment film 38 are arranged in this order from the inner surface. It is coated. The electrode 35 is wired in a pattern so that it can be connected to the control circuit by a connecting line at the electrode lead-out portion 39. The electrode 36 is electrically connected to the electrode 36 formed on the glass substrate 32 by the conductive spacer 33. Therefore, the electrode 36 can be connected to the control circuit (not shown) of the liquid crystal magnification conversion element 115a by the connection line at the electrode lead-out portion 39. Liquid crystal 34 is filled in the liquid crystal cell.

  The alignment direction of the liquid crystal is substantially parallel to the transparent substrate when no electric field is applied, and the alignment direction is substantially perpendicular to the transparent substrate when an electric field is applied. Is selected to be approximately equal to the refractive index of the transparent substrate. Therefore, when the ordinary refractive index of the liquid crystal is approximately equal to the refractive index of the transparent substrate, it does not function as a Fresnel lens hologram for light polarized in the direction of the ordinary refractive index of the liquid crystal, and the direction of the abnormal refractive index of the liquid crystal It functions as a Fresnel lens hologram for polarized light. If the extraordinary refractive index of the liquid crystal is approximately equal to the refractive index of the transparent substrate, it functions as a Fresnel lens hologram for light polarized in the direction of the ordinary refractive index of the liquid crystal, and the direction of the extraordinary refractive index of the liquid crystal It does not function as a Fresnel lens hologram for polarized light. Therefore, a Fresnel lens hologram having polarization selectivity is configured.

  As described above, also in the third embodiment, as in FIGS. 10A and 10B, the liquid crystal magnification at which the effective light beam condensed by the objective lens 109 has the same diameter when incident on the liquid crystal element. The conversion element 115a is employed. By using such a liquid crystal magnification conversion element 115a that switches the degree of divergence of the incident light beam to the objective lens 109 by applying a voltage to a liquid crystal element having a concentric blazed shape formed on a transparent substrate, an optical recording medium (BD) In the case of an optical recording medium (HD), the light use efficiency and the RIM intensity can be made the same.

  FIG. 13 is a schematic diagram showing an information recording surface of an optical recording medium used for an optical pickup in Embodiment 4 of the present invention. In the optical recording medium 110e, as shown in FIG. 13, the information recording surface is formed with a p layer (p ≧ 2) in the thickness direction, and the (pq) layer on the near side near the objective lens has a high recording density. In the layer 41, the q layer on the far side may be an optical recording medium including the information recording layer 44 having a low recording density. In that case, as an optical pickup, the NA light beam can be condensed on the (pq) layer having a high information recording density, and the inner q layer can condense a light beam having a numerical aperture NA2 smaller than NA1. That's fine. By using the magnification conversion means described in the first to third embodiments, a good recording / reproducing operation can be performed without reducing the light utilization efficiency and the RIM intensity for any of the p layers.

  Furthermore, as the multilayer optical recording medium, for example, as shown in FIG. 14, a recording medium having two formats corresponding to the optical recording medium (BD) and the optical recording medium (HD) of the first embodiment may be used. Good. That is, in FIG. 14, the information recording surface 45 is a layer of “optimal NA 0.85, light irradiation side substrate thickness 0.1 mm”, and the information recording surface 46 is “NA 0.65, light irradiation side substrate thickness 0.6 mm”. Layer.

  FIG. 15 is a diagram showing the relationship between the light emission amount required for recording on the recording-system optical recording medium and the recording speed, and shows the cases of NA 0.65 and NA 0.85. It is known that the recording speed is approximately related to the root rule. That is, it is known that when the recording speed is doubled, the required light amount is doubled (root). Further, in NA 0.65 and NA 0.85, the spot condensing density acts in inverse proportion to the area (the square of NA), and therefore a difference due to NA as shown in FIG. 15 occurs.

  For this reason, when the light source emission amount required at the recording speed α is A and the light source emission amount required at the recording speed β is B, (Equation 3)

の関係を満足するように、媒体および選択記録速度に応じて光源の発光量を切り換えれば、各媒体の集光スポット径の差異に伴うパワー補償が行える。また、光量は光ピックアップに一般に搭載されているレーザ光量モニタ手段を使用することによりフィードバック制御が可能である。

If the light emission amount of the light source is switched in accordance with the medium and the selected recording speed so as to satisfy the above relationship, power compensation associated with the difference in the condensed spot diameter of each medium can be performed. The amount of light can be feedback-controlled by using a laser light amount monitoring means generally mounted on the optical pickup.

  FIG. 16 is a block diagram showing a schematic configuration of the optical information processing apparatus according to Embodiment 5 of the present invention. The optical information processing apparatus of the fifth embodiment shows one form thereof, and records information signals on the optical pickups of the first to third embodiments and the optical recording medium of the fourth embodiment. And an apparatus for performing reproduction, and includes an optical pickup 51 corresponding to the optical pickup described above. In addition, the arrow which connects between each block shown in FIG. 16 shows the main flow of a signal, and does not limit the function between each block.

  The optical information processing apparatus shown in FIG. 16 moves the spindle motor 58 for rotating the optical recording medium 110 and the optical pickup 51 used for recording and reproducing information signals to the inner and outer circumferences of the optical recording medium 110. , A modulation / demodulation circuit 54 that performs predetermined modulation and demodulation processing, a servo control circuit 53 that performs servo control of the optical pickup 51, and a system controller 56 that controls the entire optical information processing apparatus. ing.

  The spindle motor 58 shown in FIG. 16 is driven and controlled by the servo control circuit 53 and is driven to rotate at a predetermined rotational speed. That is, the optical recording medium 110 to be recorded and reproduced is chucked on the drive shaft of the spindle motor 58 and driven and controlled by the servo control circuit 53. By this spindle motor 58, the optical recording medium 110 is rotationally driven at a predetermined rotational speed.

  When recording and reproducing information signals to and from the optical recording medium 110, the optical pickup 51 irradiates the optical recording medium 110 that is rotationally driven with laser light and detects the return light flux as described above. This optical pickup 51 is connected to a modem circuit 54. When recording the information signal, a signal input from the external circuit 55 and subjected to a predetermined modulation process by the modulation / demodulation circuit 54 is supplied to the optical pickup 51. Based on the signal supplied from the modulation / demodulation circuit 54, the optical pickup 51 irradiates the optical recording medium 110 with laser light that has undergone light intensity modulation. When reproducing the information signal, the optical pickup 51 irradiates the rotationally driven optical recording medium 110 with a laser beam having a constant output, and a reproduction signal is generated from the return light. The reproduction signal is supplied to the modem circuit 54.

  The optical pickup 51 is also connected to a servo control circuit 53. Then, as described above, the focus servo signal and the tracking servo signal are generated from the return light beam reflected and returned by the rotationally driven optical recording medium 110 at the time of recording and reproducing the information signal. It is supplied to the servo control circuit 53.

  The modem circuit 54 is connected to the system controller 56 and the external circuit 55. The modulation / demodulation circuit 54 receives a signal to be recorded on the optical recording medium 110 from the external circuit 55 under the control of the system controller 56 when the information signal is recorded on the optical recording medium 110, and performs a predetermined process on the signal. The modulation process is performed. The signal modulated by the modem circuit 54 is supplied to the optical pickup 51.

  Further, the modem circuit 54 receives a reproduction signal reproduced from the optical recording medium 110 from the optical pickup 51 under the control of the system controller 56 when reproducing the information signal from the optical recording medium 110, and performs this reproduction. A predetermined demodulation process is performed on the signal. Then, the signal demodulated by the modem circuit 54 is output from the modem circuit 54 to the external circuit 55.

  The feed motor 52 is for moving the optical pickup 51 to a predetermined position in the radial direction of the optical recording medium 110 when recording and reproducing the information signal, and based on a control signal from the servo control circuit 53. Driven. That is, the feed motor 52 is connected to the servo control circuit 53 and is controlled by the servo control circuit 53.

  The servo control circuit 53 controls the feed motor 52 so that the optical pickup 51 is moved to a predetermined position facing the optical recording medium 110 under the control of the system controller 56. The servo control circuit 53 is also connected to the spindle motor 58 and controls the operation of the spindle motor 58 under the control of the system controller 56. That is, the servo control circuit 53 controls the spindle motor 58 so that the optical recording medium 110 is rotationally driven at a predetermined rotational speed when information signals are recorded and reproduced on the optical recording medium 110.

  Further, the servo control circuit 53 is also connected to the optical pickup 51. When recording and reproducing information signals, the servo control circuit 53 receives a reproduction signal and a servo signal from the optical pickup 51, and is mounted on the optical pickup 51 based on the servo signal. The focus servo and tracking servo are controlled by the two-axis actuator (not shown), and in the case of the first embodiment, the one-axis actuator is controlled so that the distance between the lenses in the expander optical system is set. By adjusting, in the case of the third embodiment, the liquid crystal magnification conversion element is switched.

  Thereby, it is possible to obtain a miniaturized optical information processing apparatus capable of recording, reproducing or erasing information with a single optical pickup for a plurality of types or multilayer optical recording media.

  An optical pickup and an optical information processing apparatus according to the present invention include magnification conversion means for correcting spherical aberration so that two recording media having different numerical apertures (NA) and substrate thicknesses are compatible. However, there is no light loss and the RIM intensity is the same, information can be recorded / reproduced on the recording medium satisfactorily, and it is useful for an apparatus for processing information on the optical recording medium.

The figure which showed schematic structure of the optical pick-up in Embodiment 1 of this invention A graph showing the relationship between the substrate thickness of the objective lens and the magnification depending on the divergence (A) of the objective lens and the expander optical system in the first embodiment is a diagram showing a light condensing state of the optical recording medium (BD) and (b) is an optical recording medium (HD). (A) in the first embodiment is a front view of the liquid crystal aperture limiting element, (b) is a diagram showing transmitted polarized light in a liquid crystal off state, and (c) is a diagram showing transmitted polarized light in a liquid crystal on state. The figure which shows each lens data in this Embodiment 1. The figure which showed schematic structure of the optical pick-up in Embodiment 2 of this invention (A) in Embodiment 2 of this invention is an optical recording medium (BD), (b) is a figure which shows the condensing state of the polarization-selective aperture limiting element of an optical recording medium (HD). (A) which shows the polarization-selective aperture limiting element in Embodiment 2 of this invention is a side view, (b) is a top view (A) of the polarization plane switching element according to the second embodiment is a diagram showing transmitted polarized light in a liquid crystal off state, and (b) is a diagram showing transmitted polarized light in a liquid crystal on state. (A) of the diffractive magnification conversion element according to the second embodiment is an optical recording medium (BD), (b) is a diagram showing a light condensing state of the optical recording medium (HD), and (c) is a plan view of the diffraction grating. The figure which showed schematic structure of the optical pick-up in Embodiment 3 of this invention Sectional drawing which shows schematic structure of the liquid-crystal magnification conversion element in this Embodiment 3. Schematic diagram showing an information recording surface of an optical recording medium used for an optical pickup in Embodiment 4 of the present invention Schematic diagram showing an information recording surface of another optical recording medium used for the optical pickup in the fourth embodiment. A diagram showing the relationship between the amount of light emission required for recording on a recording optical recording medium and the recording speed FIG. 5 is a block diagram showing a schematic configuration of an optical information processing apparatus in Embodiment 5 of the present invention. The figure which showed schematic structure of the conventional optical pick-up

Explanation of symbols

24a Polarizing film 24b Transparent glass 25a, 26, 27, 28 Diffraction gratings 25b, 25f, 31, 32 Glass substrates 25c, 25e Polarization selective diffraction grating 25d Isotropic medium 33 Conductive spacer 34 Liquid crystal 35, 36 Electrode 37 Insulating film 38 Alignment film 39 Lead portions 41, 42, 43, 44, 45, 46 Information recording layer 51 Optical pickup 52 Feed motor 53 Servo control circuit 54 Modulation / demodulation circuit 55 External circuit 56 System controller 58 Spindle motor 101 Semiconductor laser 102 Collimating lens 103 Polarization Beam splitter 103a Half mirror 104 Polarization plane switching element 105 Deflection prism 106 Liquid crystal aberration correction element 107 Liquid crystal shutter 108a Actuator 108b Opening 109 Objective lens 110 Optical recording medium 110a Optical recording medium (BD)
110b Optical recording medium (HD)
110e, 110f Multi-layer optical recording medium 111 Detection lens 112 Light receiving element 114 Expander optical system 114a, 114b Lens 115 Diffractive magnification conversion element 115a Liquid crystal magnification conversion element 116 Liquid crystal aperture limiting element 116a Polarization selective aperture limiting element 117 1/4 wavelength Board

Claims (6)

Information for a first optical recording medium having a wavelength λ1, a substrate thickness t1, a used numerical aperture NA1, and a second optical recording medium having a wavelength λ1, a substrate thickness t2 (> t1) and a used numerical aperture NA2 (<NA1) In an optical pickup for recording and / or reproducing
A light source, an objective lens for condensing the light flux emitted from the light source on an optical recording medium, and a degree of convergence or divergence of the light flux incident on the objective lens are switched according to the type of the medium. Magnification conversion means for minimizing the spherical aberration of the light beam condensed on each of the two optical recording media, and the outermost peripheral light beam diameter of each light beam acting on the light condensing on the first and second optical recording media, An optical pickup characterized by matching when the magnification conversion means is incident. Information for a first optical recording medium having a wavelength λ1, a substrate thickness t1, a used numerical aperture NA1, and a second optical recording medium having a wavelength λ1, a substrate thickness t2 (> t1) and a used numerical aperture NA2 (<NA1) In an optical pickup for recording and / or reproducing
A light source, an objective lens for condensing the light flux emitted from the light source on an optical recording medium, and a degree of convergence or divergence of the light flux incident on the objective lens are switched according to the type of the medium. Magnification conversion means for minimizing the spherical aberration of the light beam condensed on each of the two optical recording media, wherein the magnification conversion means is an expander optical system, and is applied to the first and second optical recording media. An optical pickup characterized in that the outermost peripheral light beam diameter of each light beam acting on condensing is the same when entering the expander optical system. Information for a first optical recording medium having a wavelength λ1, a substrate thickness t1, a used numerical aperture NA1, and a second optical recording medium having a wavelength λ1, a substrate thickness t2 (> t1) and a used numerical aperture NA2 (<NA1) In an optical pickup for recording and / or reproducing
A light source, an objective lens for condensing the light beam emitted from the light source on an optical recording medium, a polarization plane switching element that selectively switches the polarization direction of the light beam according to the medium type, and switching between the polarization plane switching elements And a magnification conversion means for switching the degree of convergence or divergence of the incident light beam to the objective lens and minimizing the spherical aberration of the light beam condensed on each of the first and second optical recording media, The magnification conversion means is a diffractive optical element, and the outermost peripheral light beam diameter of each light beam acting on the first and second optical recording media is the same when the diffractive element is incident. Features an optical pickup. Information for a first optical recording medium having a wavelength λ1, a substrate thickness t1, a used numerical aperture NA1, and a second optical recording medium having a wavelength λ1, a substrate thickness t2 (> t1) and a used numerical aperture NA2 (<NA1) In an optical pickup for recording and / or reproducing
A light source, an objective lens for condensing the light flux emitted from the light source on an optical recording medium, and a degree of convergence or divergence of the light flux incident on the objective lens are switched according to the type of the medium. Magnification conversion means for minimizing the spherical aberration of the light beam condensed on each of the two optical recording media, wherein the magnification conversion means is a liquid crystal element, and is concentrated on the first and second optical recording media. An optical pickup characterized in that the outermost peripheral light flux diameter of each light flux acting on light coincides when the liquid crystal element is incident. The used numerical aperture NA1 of the first optical recording medium is 0.85 and the used numerical aperture NA2 of the second optical recording medium is 0.65, and the recording speed of the first optical recording medium is α. When the required light source emission amount is A, and when the recording speed in the second optical recording medium is β, the required light source emission amount is B, the following (Equation 1)

5. The optical pickup according to claim 1, wherein the light emission amount of the light source is switched in accordance with the selected optical recording medium and the recording speed so as to satisfy the relationship.   An optical information processing apparatus that performs at least one recording, reproduction, and erasing of information on an optical recording medium, wherein the optical pickup according to any one of claims 1 to 5 is used. An optical information processing apparatus.

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