JP2006244580A - Optical pickup and optical information processor using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To form a successful spot in any of a plurality of kinds of optical recording media with one objective lens to more compactly arrange elements. <P>SOLUTION: In a blue/CD compatible optical pickup, an optical recording medium (CD system) 107a or an optical recording medium (blue system) 107b is set. At the time of recording, reproduction of the CD system optical recording medium, radiation light of a semiconductor laser 101a for CD opposite to the objective lens 105 via a dichroic prism 103 is made incident on the objective lens 105 through the dichroic prism 103 which performs dead zone transmission of a hologram element 102 for CD, transmits infrared wavelength light and reflects blue wavelength light and a quarter wavelength plate 104 with aperture restriction and condensed by the optical recording medium 107a. Reflected light of the optical recording medium 107a diffracts only a light beam of a backward path rotated in the perpendicular direction of a forward path on a hologram formation surface of the hologram element 102 for CD and is received by a light receiving element 101c for CD. High light use efficiency is secured both on the forward and backward paths by the hologram formation surface. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an optical pickup having compatibility in three-generation optical recording media such as blue, DVD, and CD, and an optical information processing apparatus using the same.

  In recent years, optical recording media such as a CD having a recording capacity of 0.65 GB and a DVD having a recording capacity of 4.7 GB are becoming widespread as means for storing video information, audio information, or data on a computer. Further, there is 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 that writes or calls information on the optical recording medium, the numerical aperture of the objective lens (hereinafter referred to as NA) is increased, or the light source By shortening the wavelength, it is effective to reduce the diameter of the beam spot condensed by the objective lens and formed on the optical recording medium. 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 785 nm, whereas the recording density is higher than that of the “CD optical recording medium”. In the “DVD optical recording medium” made, 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 further larger than 0.65, or the wavelength of the light source is increased. It is desired to make it shorter than 660 nm.

As such a new standard, the following two standards using a blue light source are known.
HD-DVD standard “NA: 0.65, wavelength λ: 405 nm, optical recording medium substrate thickness: 0.6 mm”
Blu-ray standard “NA: 0.85, wavelength λ: 405 nm, optical recording medium substrate thickness: 0.1 mm”
In recent years, new standards with higher NA or shorter wavelengths have been proposed. On the hand of users, there are CDs and DVDs that are conventional optical recording media. It is desirable that both these optical recording media and the new standard optical recording media can be handled by the same optical information processing apparatus. As the simplest method, there is a method of mounting two optical pickups, a conventional optical pickup and a new standard optical pickup. However, with this method, it is difficult to achieve downsizing and cost reduction.

  Therefore, it is desirable to have a configuration including each light source of blue, DVD, and CD and one objective lens for condensing the emitted light from each light source on a predetermined optical recording medium. By the way, there is an aberration problem in order to focus light onto optical recording media of different standards such as blue, DVD, and CD with one objective lens. Infinite system incidence (the incident light to the objective lens is parallel) to a blue optical recording medium of “wavelength: λ1 = 405 nm, numerical aperture: NA (λ1) = 0.65, substrate thickness: t1 = 0.6 mm” In this case, a single objective lens that minimizes wavefront aberration is used, and “wavelength: λ2 = 660 nm, numerical aperture: NA (λ2) = 0.65, substrate thickness: t2 = When a spot is formed on a 0.6-mm DVD optical recording medium with infinite incidence, spherical aberration due to the difference in wavelength occurs as shown in FIG.

  Here, the horizontal axis of FIG.23 (b) has shown the height from an optical axis. The vertical axis represents wavefront aberration. Similarly, when spot formation is performed on a CD-type optical recording medium of “wavelength: λ3 = 785 nm, numerical aperture: NA (λ3) = 0.50, t2 = 1.2 mm” by infinite system incidence, FIG. As shown in FIG. 4, spherical aberration is caused by the difference in wavelength and substrate thickness.

  As a method of suppressing such spherical aberration, a method of making an incident light beam incident on an objective lens as described in Patent Document 1 incident in a finite system is known. In general, changing the divergence state of the light beam incident on the objective lens is equivalent to changing the spherical aberration. Therefore, a divergence state that can reduce the spherical aberration may be selected. For example, when the object distance (corresponding to the distance between the light source and the objective lens) of a CD optical system constituted by a finite system is changed, spherical aberration is suppressed. FIG. 24B is a diagram showing a case where the object distance is changed in the CD optical system, and according to this, the wavefront deterioration is reduced in the vicinity of the object distance of 50 mm.

  FIG. 25B is a diagram showing wavefront aberration after correction due to incidence of a finite system. FIG. 24B illustrates the case where there is no part between the objective lens and the light source, but in reality, a wave plate, a prism, a lens, and the like are arranged between the objective lens and the light source. In particular, in an optical pickup corresponding to three media of blue, DVD, and CD, the number of parts is large, and the above 50 mm is small, which becomes a constraint condition of the parts layout.

  The following is a configuration example of an optical system of a conventional DVD / CD compatible pickup, such as FIG. 1 of Non-Patent Document 1, FIG. 2 of Non-Patent Document 2, and FIG. 2 of Non-Patent Document 3.

As can be seen from these examples, the optical system generally has a structure in which a light source, a light receiving element, and a synthesizing unit between two wavelengths are developed in a plane parallel to the optical recording medium, and finally, the deflecting unit is set up in the direction of the objective lens. ing. However, in such a configuration, when the CD optical system with the short object distance and the blue or DVD optical system are arranged, for example, as shown in FIG. Will become very large.
Japanese Patent No. 3240846 JP 2003-338070 A JP 2000-67453 A Daisuke Ogata et al., “Matsushita Technical Journal”, Vol. 45, No. 6, p. 32-37 (Dec. 1999) Mineharu Uchiyama, Keiji Shinozuka, “Toshiba Review”, Vol.57, No.7, p.32-33 (2002) Shinichi Nagahara et al., “PIONEER R & D”, Vol.13, No.1, p.41-54

  In order to realize a two-wavelength or three-wavelength compatible optical pickup, a method in which the CD optical system is a finite system is known. However, there is a layout problem due to the short object distance.

  The present invention has been made in view of the problems as described above, and is intended to enable favorable spot formation in any of a plurality of types of optical recording media with one objective lens. An object of the present invention is to provide an optical pickup and an optical information processing apparatus using the optical pickup which realize a more compact element arrangement by using a CD optical system with a short object distance as a finite system in blue, DVD and CD optical recording media. To do.

  In order to achieve the above object, an optical pickup according to claim 1 of the present invention includes two light sources having wavelengths λ1 and λ2 (λ1 <λ2) and an infinite system for light having a wavelength λ1. An optical pickup including an objective lens used for incident light of a wavelength λ2 with a finite incidence and a dichroic prism that reflects light of wavelength λ1 and transmits light of wavelength λ2 passes through the dichroic prism. With the configuration in which the lens and the light source having the wavelength λ2 are arranged to face each other, for example, in the case of an optical pickup compatible with blue and CD, the optical path of the CD optical system with a short object distance can be laid out.

  An optical pickup according to claim 2 is the optical pickup according to claim 1, wherein a light receiving element for detecting reflected light from a light source having a wavelength λ2 and an optical recording medium having a wavelength λ2 is housed in the same container. A compact optical system can be realized by the configuration including the light emitting / receiving unit and the hologram element that deflects the optical path to the light receiving element between the dichroic prism and the light emitting / receiving unit.

  The optical pickup according to any one of claims 3 to 5 is the optical pickup according to claims 1 and 2, wherein an emission angle of light emitted from the light source having the wavelength λ2 is set between the dichroic prism and the light source having the wavelength λ2. A hologram element for changing, a hologram element for adding astigmatism to light emitted from the light source of wavelength λ2 between the dichroic prism and the light source of wavelength λ2, and a dichroic prism having a wavelength of λ1 For example, in the case of an optical pickup compatible with blue and CD, an optical system is formed with an optical path shorter than the optimum object distance of the CD optical system. A CD optical system with higher light utilization efficiency can be realized, and a plate type can be used as a dichroic prism. In addition, a good blue spot can be formed by thinning the blue optical path by the wedge-shaped beam shaping prism.

  The optical pickup described in claim 6 is an infinite system for light of wavelengths λ1, λ2, and λ3 (λ1 <λ2 <λ3) and light of wavelength λ1, and light of wavelengths λ2 and λ3. On the other hand, in an optical pickup equipped with an objective lens that is used in a finite system and a trichroic prism that reflects light of wavelengths λ1 and λ2 and transmits light of wavelength λ3, With the configuration in which the light sources having the wavelength λ3 are arranged to face each other, for example, in the case of an optical pickup compatible with blue, DVD, and CD, the optical path of the CD optical system with a short object distance can be laid out.

  An optical pickup according to a seventh aspect is the optical pickup according to the sixth aspect, in which a light receiving element for detecting reflected light from a light source having a wavelength λ3 and an optical recording medium having a wavelength λ3 is housed in the same container. A compact optical system can be realized by the configuration including the light emitting / receiving unit and the hologram element that deflects the optical path to the light receiving element between the trichromatic prism and the light emitting / receiving unit.

  The optical pickup according to any one of claims 8 to 10 is the optical pickup according to any one of claims 6 and 7, wherein the emission angle of the emitted light from the light source having the wavelength λ3 is between the trichroic prism and the light source having the wavelength λ3. And a hologram element for adding astigmatism to the light emitted from the light source having the wavelength λ3 between the trichromatic prism and the light source having the wavelength λ3. By using a wedge-shaped beam shaping prism that reflects the light emitted from the light sources with wavelengths λ1 and λ2 on the back surface, for example, in the case of an optical pickup compatible with blue and DVD and CD, the optical path is shorter than the optimum object distance of the CD optical system. By forming an optical system, a CD optical system with higher light utilization efficiency can be realized, and a plate type can be used as a trichromatic prism. Enables strike. In addition blue by the wedge-shaped beam shaping prism, the DVD light path thinned to form a good blue, DVD spot.

  The optical pickups according to claims 11 and 12 are the optical pickups according to claims 1 to 5, comprising an actuator mounted with an objective lens and tilting in a radial direction of the optical recording medium, and the objective lens and the wavelength. Adjusting the amount of tilting of the actuator according to the amount of optical axis deviation between the light sources of λ2, a liquid crystal element for adding coma aberration to the incident light beam of the objective lens, and the amount of optical axis deviation between the objective lens and the light source of wavelength λ2 According to the configuration in which the coma aberration amount of the liquid crystal element is adjusted according to the above, a good spot without coma aberration can be obtained in the optical path of the CD optical system with a short object distance even if the objective lens position is shifted.

  The optical pickups according to claims 13 and 14 are the optical pickups according to claims 6 to 10, comprising an actuator mounted with an objective lens and tilting in a radial direction of the optical recording medium, and the objective lens and the wavelength. Adjusting the amount of tilting of the actuator according to the amount of optical axis deviation between the light sources of λ3, a liquid crystal element for adding coma aberration to the incident light beam of the objective lens, and the amount of optical axis deviation between the objective lens and the light source of wavelength λ3 According to the configuration in which the coma aberration amount of the liquid crystal element is adjusted according to the above, a good spot without coma aberration can be obtained in the optical path of the CD optical system with a short object distance even if the objective lens position is shifted.

  The optical pickup according to claim 15 is the optical pickup according to claims 2 to 4, 7 to 9, and a more compact optical system is realized by integrally forming the hologram element with the light receiving and emitting unit. it can.

  The optical information processing apparatus according to claim 16 uses at least one light source of wavelengths λ1, λ2, and λ3 (λ1 <λ2 <λ3) to record, reproduce, or erase information on an optical recording medium. 15. An optical information processing apparatus that performs one or more of the above, and by using the optical pickup according to any one of claims 1 to 14, the optical path of a short object distance optical system that is compatible with two wavelengths or three wavelengths. An optical information processing apparatus having a compact optical system that can be laid out can be obtained.

  According to the present invention, a two-wavelength or three-wavelength compatible optical pickup and an optical information processing apparatus using the same are realized, and an optical system of a short object distance optical system can be laid out. There is an effect that it can be configured.

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

  As Embodiment 1 of the present invention, “a blue-based optical recording medium having a light irradiation side substrate thickness of 0.6 mm at a use wavelength of 405 nm and NA of 0.65” and “light irradiation side substrate thickness at a use wavelength of 785 nm and NA of 0.50. An optical pickup capable of recording, reproducing, and erasing a “1.2 mm CD-based optical recording medium” will be described.

  1A and 1B show a schematic configuration of a blue / CD compatible optical pickup in Example 1 of the first embodiment, wherein FIG. 1A is a side view and FIG. 1B is a top view. As shown in FIGS. 1A and 1B, the main parts of the optical pickup are a CD light receiving / emitting unit 101, a CD hologram element 102, a dichroic prism 103, an aperture-limited quarter-wave plate 104, and an objective lens 105. A CD optical system through which a light beam with a wavelength of 785 nm passes, a blue semiconductor laser 108 with a wavelength of 405 nm, a collimating lens 109, a polarizing beam splitter 110, a dichroic prism 103, a quarter-wave plate 104 with aperture restriction, an objective The lens 105, the condenser lens 111, the light beam splitting element 112, and the light receiving element 113 are configured by a blue optical system through which a light beam having a wavelength of 405 nm passes.

  That is, the dichroic prism 103, the aperture-limited quarter-wave plate 104, and the objective lens 105 are common components of the two optical systems. Here, the objective lens 105 is designed so that the wavefront aberration is minimized in an infinite system with respect to “a blue optical recording medium having a used wavelength of 405 nm and NA of 0.65 and a light irradiation side substrate thickness of 0.6 mm”. ing. In general, since the objective lens has a tighter tolerance as the NA is higher and the wavelength is shorter, it is more difficult to obtain desirable characteristics in the blue system than in the CD system.

  In addition, the objective lens 105 and the aperture-limited quarter-wave plate 104 are held by the actuator unit 106, can be moved in the focus direction or the track direction, and are set to an optimum position by servo control.

  Optical recording media 107a and 107b shown in FIGS. 1 (a) and 1 (b) are optical recording media having different substrate thicknesses or different working wavelengths, respectively. The optical recording medium 107a is a CD optical recording medium having a substrate thickness of 1.2 mm. The optical recording medium 107b is a blue optical recording medium having a substrate thickness of 0.6 mm. At the time of recording or reproducing, only one of the optical recording media is set in a rotating mechanism (not shown) and rotated at a high speed.

  First, a case where “a CD optical recording medium having a used wavelength of 785 nm and NA of 0.50 and a light irradiation side substrate thickness of 1.2 mm” is recorded, reproduced or erased will be described. FIG. 2 is a detailed view showing a CD light emitting / receiving unit, in which a concave portion having a 45 ° etched mirror 101b is formed on a Si substrate by etching, and a CD semiconductor laser 101a is mounted therein. Further, a CD light receiving element 101c for detecting reflected light from the optical recording medium is formed. As shown in FIG. 2, it is not necessary to increase the thickness of the optical pickup by pulling out the terminal 101d in a direction parallel to the optical recording medium.

  FIG. 3 is an optical path diagram of only the CD system shown in FIG. In FIG. 3, a 785 nm light beam emitted from the CD semiconductor laser 101a of the CD light receiving and emitting unit 101 is transmitted through the CD hologram element 102, the infrared wavelength band light beam is transmitted, and the blue wavelength band is transmitted. The light beam passes through the dichroic prism 103 to be reflected, passes through the quarter-wave plate 104 with aperture restriction, and becomes circularly polarized light. In addition, the outside light beam is reflected by the aperture limiting function of the wavelength selective coat, and only the light beam corresponding to NA 0.50 is incident on the objective lens 105 and condensed as a minute spot on the optical recording medium 107a. Information is reproduced, recorded or erased by this spot.

  The light reflected from the optical recording medium 107 a becomes circularly polarized light opposite to the outward path, and the CD light receiving element in the same container (can) of the CD light receiving and emitting unit 101 by the hologram forming surface 102 a of the CD hologram element 102. The light is diffracted in the direction 101c and received by the light receiving element 101c for CD. Here, the hologram element is preferably a polarization selective hologram element. That is, the forward light beam is transmitted through the dead zone, and high light utilization efficiency can be ensured in both the forward and backward paths by diffracting only the backward light beam rotated in the direction orthogonal to the forward path. An information signal and a servo signal are detected from the CD light receiving element 101c.

  Next, a case where “a blue optical recording medium having a used wavelength of 405 nm and NA of 0.65 and a light irradiation side substrate thickness of 0.6 mm” is recorded or reproduced will be described. As shown in FIG. 1B, the linearly polarized divergent light emitted from the blue semiconductor laser 108 having a wavelength of 405 nm is made substantially parallel light by the collimator lens 109, reflected by the polarization beam splitter 110, and passed through the dichroic prism 103. The light is reflected, passes through the aperture-limited quarter-wave plate 104, becomes circularly polarized light, enters the objective lens 105, and is condensed as a minute spot on the optical recording medium 107 b. The aperture limiting function has a coating configuration that transmits the dead band in the blue wavelength band.

  The light reflected from the optical recording medium 107b becomes circularly polarized light in the direction opposite to the outward path, becomes again substantially parallel light, passes through the quarter wave plate 104 with aperture restriction, and becomes linearly polarized light orthogonal to the forward path, and is polarized. The light passes through the beam splitter 110, is converged by the condenser lens 111, is deflected and divided into a plurality of optical paths by the light beam splitter 112, and reaches the light receiver 113. An information signal and a servo signal are detected from the light receiving element 113.

  FIG. 4 is a diagram showing a schematic configuration of a blue / CD compatible optical pickup in Example 2 of the first embodiment. As shown in FIG. 4, the CD light receiving / emitting unit 101, the CD hologram element 202, and the dichroic prism 103 may be integrated. In that case, it becomes shorter than the optimum object distance of the CD optical system in the objective lens 105. If it is used as it is, the spherical aberration increases and a good spot cannot be obtained. Therefore, the second embodiment includes the CD hologram element 202 on which a hologram pattern for changing the radiation angle of the light emitted from the light source is formed.

  Such a lens function may be formed by forming a concentric holographic pattern on the surface of the substrate and a sawtooth or pseudo-sawtooth hologram pattern in a cross section by etching or the like. In addition, by arranging such a lens function near the light source, a larger amount of light emitted from the light source can be taken in (coupled), so that higher light utilization efficiency can be realized compared to the first embodiment, and the speed can be increased. It is valid. The blue optical system is the same as that in the first embodiment.

  Here, only the optical path of the CD optical system will be described. FIG. 5 is an optical path diagram of only the CD optical system shown in FIG. In FIG. 5, the radiation angle of the 785 nm light beam emitted from the CD semiconductor laser 101 a of the CD light receiving and emitting unit 101 is changed on the lens function hologram forming surface 202 a of the CD hologram element 202. The lens can be produced with either positive or negative power, but here, a hologram pattern for focusing on the light source side is formed.

  The light beam that has passed through the deflection separation hologram forming surface 202b on the 0th order is transmitted through the dichroic prism 103 that transmits the light beam in the infrared wavelength band and reflects the light beam in the blue wavelength band. The light passes through the wave plate 104 and is substantially circularly polarized. Further, the outside light is reflected by the aperture limiting function on which the wavelength selective coat is deposited, and only the light beam corresponding to NA 0.50 is incident on the objective lens 105 and is condensed as a minute spot on the optical recording medium 107a. The Information is reproduced, recorded or erased by this spot.

  The light beam reflected from the optical recording medium 107 a becomes circularly polarized light in the direction opposite to the outward path, and the light receiving for CD in the same can of the CD light receiving and emitting unit 101 by the deflection separation hologram forming surface 202 b of the CD hologram element 202. The light is diffracted in the direction of the element 101c and received by the CD light receiving element 101c. An information signal and a servo signal are detected from the CD light receiving element 101c.

  FIG. 6 is a diagram showing a schematic configuration of a blue / CD compatible optical pickup in Example 3 of the first embodiment. As shown in FIG. 6, the dichroic prism is not limited to the cube type, and may be a plate type. It is generally known that astigmatism occurs when a plate substrate is incident obliquely into a diverging light path. Therefore, the third embodiment includes a hologram element on which a hologram pattern for generating astigmatism having a polarity opposite to this astigmatism is formed. The blue optical system is the same as in Examples 1 and 2.

  Here, only the optical path of the CD optical system will be described. FIG. 7 is an optical path diagram of only the CD optical system shown in FIG. In FIG. 7, the 785 nm light beam emitted from the CD semiconductor laser 101a of the CD light receiving and emitting unit 101 is given a predetermined aberration on the astigmatism correction function hologram forming surface 302a of the CD hologram element 302. .

  The light beam that has been transmitted through the deflection separation hologram forming surface 302b in the 0th order is transmitted through the dichroic prism 303 that transmits the light beam in the infrared wavelength band and reflects the light beam in the blue wavelength band. The light passes through the wave plate 104 and is substantially circularly polarized. Further, the outer light beam is reflected by the aperture limiting function on which the wavelength selective coat is deposited, and only the light beam corresponding to NA 0.50 is incident on the objective lens 105 and is condensed as a minute spot on the optical recording medium 107a. Is done.

  In general, astigmatism is generated in a finite light beam traveling in an obliquely arranged plate substrate, but in this embodiment, astigmatism with reverse polarity is added in advance in the CD hologram element 302. As a result, the astigmatism of the incident light of the objective lens 105 is canceled. Information is reproduced, recorded, or erased by the spot condensed by the objective lens 105.

  The light reflected from the optical recording medium 107 a becomes circularly polarized light in the direction opposite to the outward path, and the CD light receiving element in the same can of the CD light receiving and emitting unit 101 by the deflection separation hologram forming surface 302 b of the CD hologram element 302. The light is diffracted in the 101c direction and received by the light receiving element for CD 101c. An information signal and a servo signal are detected from the CD light receiving element 101c.

  FIG. 8 is a diagram showing a schematic configuration of a blue / CD compatible optical pickup in Example 4 of the first embodiment. As shown in FIG. 8, the dichroic prism is not limited to the cube type, and may be a wedge-shaped prism. The wedge-shaped dichroic prism 403 shown in FIG. 8 transmits a light beam in the blue wavelength band incident from the horizontal direction through the surface of the prism on the optical recording medium side and reflects it on the dichroic-coated CD light source side dichroic mirror surface 103a. Then, the light is again emitted from the surface on the optical recording medium side and is incident on the objective lens 105.

  A method of converting an elliptical beam intensity distribution shape into a circle by following such an optical path is generally known. A light beam converted into a circular intensity distribution is condensed by the objective lens 105 to obtain a small-diameter beam spot. Also, by turning the optical path of the blue optical system before entering the wedge-shaped dichroic prism 403 in an elliptical shape, each optical component of the blue optical system can be thinned in the thickness direction, resulting in a thin blue optical system. Can be

  As for the optical path of the CD optical system, astigmatism occurs when a finite system light beam passes through the wedge-shaped dichroic prism. Therefore, there is a hologram pattern that generates astigmatism having the opposite polarity to this astigmatism. The CD hologram element 402 is formed.

  Here, only the optical path of the CD optical system will be described. FIG. 9 is an optical path diagram of only the CD optical system shown in FIG. In FIG. 9, the 785 nm light beam emitted from the CD semiconductor laser 101a of the CD light receiving and emitting unit 101 is given a predetermined aberration at the astigmatism correction function hologram forming surface 402a of the CD hologram element 402. .

  The light beam that has been transmitted through the deflection separation hologram forming surface 402b with zero order passes through the wedge-shaped dichroic prism 403 that transmits the light beam in the infrared wavelength band and reflects the light beam in the blue wavelength band. The light passes through the quarter-wave plate 104 with aperture limitation and is substantially circularly polarized. Further, the outside light is reflected by the aperture limiting function on which the wavelength selective coat is deposited, and only the light beam corresponding to NA 0.50 is incident on the objective lens 105 and is condensed as a minute spot on the optical recording medium 107a. The

  In general, astigmatism is generated in a finite light beam traveling in the wedge-shaped substrate, but in the fourth embodiment, astigmatism with reverse polarity is added in advance by the CD hologram element 402. For this reason, the astigmatism of the light beam incident on the objective lens 105 is canceled. Information is reproduced, recorded, or erased by the spot condensed by the objective lens 105.

  The light reflected from the optical recording medium 107a becomes circularly polarized light opposite to the outward path, and the CD light receiving element in the same can of the CD light receiving and emitting unit 101 by the deflection separation hologram forming surface 402b of the CD hologram element 402. The light is diffracted in the 101c direction and received by the light receiving element for CD 101c. An information signal and a servo signal are detected from the CD light receiving element 101c.

  In Examples 1 to 4 of the first embodiment described above, the case where the blue system (corresponding to the HD-DVD standard) of NA 0.65 and the CD system are compatible has been described. Not limited to this, NA 0.65 blue system and DVD system compatibility, DVD system and CD system compatibility, or NA 0.65 blue system instead of NA 0.65 blue system (equivalent to Blu-ray standard) ) May be compatible with the optical pickup.

  Next, as a second embodiment of the present invention, “a blue optical recording medium having a light irradiation side substrate thickness of 0.6 mm at a working wavelength of 405 nm and NA of 0.65” and “light irradiation at a working wavelength of 660 nm and NA of 0.65”. Optical pickup capable of recording, reproducing, and erasing both a DVD optical recording medium having a side substrate thickness of 0.6 mm and a CD optical recording medium having a light irradiation side substrate thickness of 1.2 mm at a working wavelength of 785 nm and NA of 0.50 explain.

  FIG. 10A is a side view and FIG. 10B is a top view showing a schematic configuration of a blue / DVD / CD compatible optical pickup in Example 5 of the second embodiment. As shown in FIGS. 10A and 10B, the main part of the optical pickup is, first, a CD optical system through which a light beam having a wavelength of 785 nm passes, a CD light emitting / receiving unit 101, a CD hologram element 502, a trichromatic. It comprises a prism 123, a quarter-wave plate 104 with aperture restriction, and an objective lens 105.

  Further, as a DVD optical system through which a light beam with a wavelength of 660 nm passes, a semiconductor laser 118 for DVD with a wavelength of 660 nm, a coupling lens 119, a composite prism 121 formed with a dichroic mirror surface 103a and a polarizing beam splitter surface 110b, a trichromatic A prism 123, an aperture-limited quarter-wave plate 104, an objective lens 105, a condenser lens 111, a light beam splitting element 112, and a light receiving element 113 are included.

  Further, as a blue optical system through which a light beam with a wavelength of 405 nm passes, a blue semiconductor laser 108 with a wavelength of 405 nm, a collimating lens 109, a composite prism 121, a trichromatic prism 123, an aperture-limited quarter-wave plate 104, an objective lens 105 , A condensing lens 111, a light beam splitting element 112, and a light receiving element 113.

  In other words, the trichroic prism 123, the aperture-limited quarter-wave plate 104, and the objective lens 105 are common components of the three optical systems. Here, the objective lens 105 is designed so that the wavefront aberration is minimized in an infinite system with respect to “a blue optical recording medium having a used wavelength of 405 nm and NA of 0.65 and a light irradiation side substrate thickness of 0.6 mm”. ing. In general, since the objective lens has a tighter tolerance as the NA is higher and the wavelength is shorter, it is more difficult to obtain desirable characteristics in the blue system than in the CD system and the DVD system.

  In addition, the objective lens 105 and the aperture-limited quarter-wave plate 104 are held by the actuator unit 106, can be moved in the focus direction or the track direction, and are set to an optimum position by servo control.

  Optical recording media 107a, 107b, and 107c shown in FIGS. 10A and 10B are optical recording media having different substrate thicknesses or different operating wavelengths. The optical recording medium 107a is a CD-based light having a substrate thickness of 1.2 mm. The recording medium and optical recording medium 107b are blue optical recording media having a substrate thickness of 0.6 mm, and the optical recording medium 107c is a DVD optical recording medium having a substrate thickness of 0.6 mm. At the time of recording or reproducing, only one of the optical recording media is set in a rotating mechanism (not shown) and rotated at a high speed.

    First, a case where “a CD optical recording medium having a used wavelength of 785 nm and NA of 0.50 and a light irradiation side substrate thickness of 1.2 mm” is recorded, reproduced or erased will be described. FIG. 11 is an optical path diagram of only the CD system of FIG. In FIG. 11, a 785 nm light beam emitted from the CD semiconductor laser 101a of the CD light receiving and emitting unit 101 is transmitted through the CD hologram element 502, an infrared wavelength band light beam is transmitted, a red wavelength band, The light beam in the blue wavelength band is transmitted through the reflecting trichroic prism 123, passes through the aperture-limited quarter-wave plate 104, and becomes circularly polarized light. In addition, the outside light beam is reflected by the aperture limiting function of the wavelength selective coat, and only the light beam corresponding to NA 0.50 is incident on the objective lens 105 and condensed as a minute spot on the optical recording medium 107a. Information is reproduced, recorded or erased by this spot.

  The light reflected from the optical recording medium 107 a becomes circularly polarized light opposite to the outward path, and the CD light receiving element in the same container (can) of the CD light receiving and emitting unit 101 by the hologram forming surface 502 a of the CD hologram element 502. The light is diffracted in the 101c direction and received by the light receiving element for CD 101c. Here, the hologram element is preferably a polarization selective hologram element. That is, the forward light beam is transmitted through the dead zone, and high light utilization efficiency can be ensured in both the forward and backward paths by diffracting only the backward light beam rotated in the direction orthogonal to the forward path. An information signal and a servo signal are detected from the CD light receiving element 101c.

  Next, a case where “DVD-based optical recording medium having a working wavelength of 660 nm and NA of 0.65 and a light irradiation side substrate thickness of 0.6 mm” is recorded or reproduced will be described. As shown in FIG. 10B, the linearly polarized divergent light emitted from the DVD semiconductor laser 118 having a wavelength of 660 nm is converted into a light beam having a predetermined magnification by the coupling lens 119, and is reflected by the dichroic mirror surface 103 a of the composite prism 121. Reflected and reflected by the polarization beam splitter surface 110 b of the composite prism 121. Further, the light is reflected from the trichroic prism 123, passes through the aperture-limited quarter-wave plate 104, and is circularly polarized. Further, the outside light beam is reflected by the aperture limiting function of the wavelength selective coat, and only the light beam corresponding to NA 0.65 enters the objective lens 105 and is condensed as a minute spot on the optical recording medium 107c. The light reflected from the optical recording medium 107c becomes circularly polarized light opposite to the outward path, passes through the aperture-limited quarter-wave plate 104 and becomes linearly polarized light orthogonal to the outward path, and the polarization beam splitter surface of the composite prism 121 110 b passes through and is converged by the condenser lens 111, deflected and divided into a plurality of optical paths by the light beam splitting element 112, and reaches the light receiving element 113. An information signal and a servo signal are detected from the light receiving element 113.

  Next, a case where “a blue optical recording medium having a used wavelength of 405 nm and NA of 0.65 and a light irradiation side substrate thickness of 0.6 mm” is recorded or reproduced will be described. As shown in FIG. 10B, the linearly polarized divergent light emitted from the blue semiconductor laser 108 having a wavelength of 405 nm is made substantially parallel light by the collimator lens 109, passes through the dichroic mirror surface 103a of the composite prism 121, and The light is reflected by the polarization beam splitter surface 110 b of the composite prism 121. The light is reflected from the trichromatic prism 123, passes through the aperture-limited quarter-wave plate 104, becomes circularly polarized light, enters the objective lens 105, and is condensed as a minute spot on the optical recording medium 107b. The aperture limiting function has a coating configuration that transmits the dead band in the blue wavelength band. The light reflected from the optical recording medium 107b becomes circularly polarized light in the opposite direction to the outward path, again becomes substantially parallel light, passes through the quarter-wave plate 104 with aperture restriction, and becomes linearly polarized light orthogonal to the forward path, resulting in a composite The light passes through the polarization beam splitter surface 110 b of the prism 121, is converged by the condenser lens 111, is deflected and divided into a plurality of optical paths by the light beam splitter 112, and reaches the light receiver 113. An information signal and a servo signal are detected from the light receiving element 113.

  FIG. 12 is a diagram for explaining the opening restriction function. The NA 0.50 region on the center side transmits through the dead band for all three wavelengths, and the region of NA 0.50 to NA 0.65 reflects the light beam in the infrared wavelength band. Further, in the region of NA 0.65 to NA 0.85, a coat for reflecting a red light beam in the infrared wavelength band is deposited.

  FIG. 13 is a diagram showing a schematic configuration of a blue / DVD / CD compatible optical pickup in Example 6 of the second embodiment. As shown in FIG. 13, the CD light emitting / receiving unit 101, the CD hologram element 602, and the trichromatic prism 123 may be integrated. In that case, it becomes shorter than the optimum object distance of the CD optical system in the objective lens 105. If it is used as it is, the spherical aberration increases and a good spot cannot be obtained. Therefore, the sixth embodiment includes a CD hologram element 602 on which a hologram pattern for changing the radiation angle of light emitted from the light source is formed.

  Such a lens function may be formed by forming a concentric holographic pattern on the surface of the substrate and a sawtooth or pseudo-sawtooth hologram pattern in a cross section by etching or the like. In addition, by arranging such a lens function near the light source, a larger amount of light emitted from the light source can be taken in (coupled), so that it is possible to realize higher light utilization efficiency than in the fifth embodiment, speeding up, etc. It is effective for. The blue optical system and the red optical system are the same as those in the fifth embodiment.

  Here, only the optical path of the CD optical system will be described. FIG. 14 is an optical path diagram of only the CD system shown in FIG. In FIG. 14, the radiation angle of the 785 nm light beam emitted from the CD semiconductor laser 101 a of the CD light receiving and emitting unit 101 is changed on the lens function hologram forming surface 602 a of the CD hologram element 602. The lens can be produced with either positive or negative power, but here, a hologram pattern for focusing on the light source side is formed.

  The light beam that has been zero-order transmitted through the hologram forming surface 602b for deflection and separation is transmitted through the trichroic prism 123 that transmits the light beam in the infrared wavelength band and reflects the light beam in the red and blue wavelength bands. The light passes through the quarter-wave plate 104 and is substantially circularly polarized. Further, the outside light is reflected by the aperture limiting function on which the wavelength selective coat is deposited, and only the light beam corresponding to NA 0.50 is incident on the objective lens 105 and is condensed as a minute spot on the optical recording medium 107a. The Information is reproduced, recorded or erased by this spot.

  The light beam reflected from the optical recording medium 107a becomes circularly polarized light in the direction opposite to the outward path, and the light reception for CD in the same can of the CD light receiving and emitting unit 101 is performed by the deflection separation hologram forming surface 602b of the CD hologram element 602. The light is diffracted in the direction of the element 101c and received by the CD light receiving element 101c. Here, the hologram element is preferably a polarization selective hologram element. That is, the forward light beam passes through the dead zone, and only the return light beam whose polarization direction is reversed is diffracted, thereby ensuring high light utilization efficiency in both reciprocations. An information signal and a servo signal are detected from the CD light receiving element 101c.

  FIG. 15 is a diagram showing a schematic configuration of a blue / DVD / CD compatible optical pickup in Example 7 of the second embodiment. As shown in FIG. 15, the trichroic prism is not limited to the cube type, and may be a plate type. It is generally known that astigmatism occurs when a plate substrate is incident obliquely into a diverging light path. Therefore, the seventh embodiment includes a hologram element on which a hologram pattern for generating astigmatism having a polarity opposite to this astigmatism is formed. The blue optical system and red optical system are the same as those in Examples 5 and 6.

  Here, only the optical path of the CD optical system will be described. FIG. 16 is an optical path diagram of only the CD optical system shown in FIG. In FIG. 16, a 785 nm light beam emitted from the CD semiconductor laser 101a of the CD light receiving and emitting unit 101 is given a predetermined aberration at the astigmatism correction function hologram forming surface 702a of the CD hologram element 702. .

  The light that has passed through the deflection separation hologram forming surface 702b in the zero order passes through the beam, the light beam in the infrared wavelength band, and the light beam in the red and blue wavelength bands passes through the trichroic prism 323 for reflection. The light passes through the quarter-wave plate 104 with aperture limitation and is substantially circularly polarized. Further, the outer light beam is reflected by the aperture limiting function on which the wavelength selective coat is deposited, and only the light beam corresponding to NA 0.50 is incident on the objective lens 105 and is condensed as a minute spot on the optical recording medium 107a. Is done.

  Note that astigmatism generally occurs in a finite light beam traveling in an obliquely arranged plate substrate, but in the seventh embodiment, astigmatism with reverse polarity is added to the CD hologram element 702 in advance. As a result, the astigmatism of the incident light of the objective lens 105 is canceled. Information is reproduced, recorded, or erased by the spot condensed by the objective lens 105.

  The light reflected from the optical recording medium 107 a becomes circularly polarized light in the opposite direction to the outward path, and the CD light receiving element in the same can of the CD light receiving and emitting unit 101 by the deflection separation hologram forming surface 702 b of the CD hologram element 702. The light is diffracted in the 101c direction and received by the light receiving element for CD 101c. An information signal and a servo signal are detected from the CD light receiving element 101c.

  FIG. 17 is a diagram showing a schematic configuration of a blue / DVD / CD compatible optical pickup in Example 8 of the second embodiment. As shown in FIG. 17, the trichroic prism is not limited to a cube type, and may be a wedge-shaped prism.

  The wedge-shaped trichromatic prism 423 shown in FIG. 17 transmits a light beam in the red and blue wavelength bands incident from the horizontal direction through the surface of the prism on the optical recording medium side, and is on the trichromatic-coated CD light source side. The light is reflected by the mirror surface 123a, is emitted again from the surface on the optical recording medium side, and enters the objective lens 105.

  A method of converting an elliptical beam intensity distribution shape into a circle by following such an optical path is generally known. A light beam converted into a circular intensity distribution is condensed by the objective lens 105 to obtain a small-diameter beam spot. In addition, by turning the optical path of the blue optical system before entering the wedge-shaped trichromatic prism 423 in an elliptical shape, each optical component of the blue optical system can be thinned in the thickness direction. Thinner.

  As for the optical path of the CD optical system, astigmatism is generated when a finite system light beam passes through the wedge-shaped trichromatic prism 423, and therefore a hologram that generates astigmatism having the opposite polarity to this astigmatism. A CD hologram element 802 on which a pattern is formed is provided.

  Here, the optical path of the CD optical system will be described. FIG. 18 is an optical path diagram of only the CD optical system shown in FIG. In FIG. 17, the 785 nm light beam emitted from the CD semiconductor laser 101a of the CD light receiving and emitting unit 101 is given a predetermined aberration at the astigmatism correction function hologram forming surface 802a of the CD hologram element 802. .

  The light beam that has passed through the deflection separation hologram forming surface 802b with zero order transmits the light beam in the infrared wavelength band, and transmits the light beam in the red and blue wavelength bands through the wedge-shaped trichroic prism 423. The light passes through the quarter-wave plate 104 with aperture limitation and is substantially circularly polarized. Further, the outside light beam is reflected by the aperture limiting function on which the wavelength selective coat is deposited, and only the light beam corresponding to NA 0.50 is incident on the objective lens 105 and is condensed as a minute spot on the optical recording medium 107a. Is done.

  In general, astigmatism is generated in a finite system light beam traveling in a wedge substrate arranged obliquely. In the eighth embodiment, however, astigmatism having a reverse polarity is preliminarily generated in the CD hologram element 802. As a result, the astigmatism of the light beam incident on the objective lens 105 is canceled. Information is reproduced, recorded, or erased by the spot condensed by the objective lens 105.

  The light beam reflected from the optical recording medium 107a becomes circularly polarized light in the direction opposite to the outward path, and the light receiving for CD in the same can of the CD light receiving / emitting unit 101 by the deflection separating hologram forming surface 802b of the CD hologram element 802. The light is diffracted in the direction of the element 101c and received by the CD light receiving element 101c. An information signal and a servo signal are detected from the CD light receiving element 101c.

  Note that astigmatism also occurs in the optical path of the DVD optical system when it passes through the wedge-shaped trichromatic prism 423, but the influence is small due to the low magnification. Further, as in the case of the CD optical system, the astigmatism correction hologram element may be arranged before the incidence of the composite prism 121.

  Further, in Examples 5 to 8 of the second embodiment described above, the case where the NA 0.65 blue system (equivalent to the HD-DVD standard) is compatible with the DVD system and the CD system has been described. 2 is not limited to this, and an optical pickup compatible with a blue system of NA 0.85 (equivalent to the Blu-ray standard) may be used instead of the blue system of NA 0.65.

  In the optical pickup according to the third embodiment of the present invention, coma occurs in the finite system due to the objective lens shift that occurs in the tracking operation and the seek operation. And canceling means.

  19A and 19B are diagrams showing the relationship between the objective lens shift and coma aberration, where (a) is a DVD optical system and (b) is a CD optical system. 19 (a) and 19 (b), it can be seen that the coma aberration deteriorates in the CD system with a short object distance.

  As a means for canceling coma aberration, there is a method of tilting the objective lens according to the lens shift amount. That is, it is generally known that coma aberration occurs when the objective lens is tilted, and an actuator that tilts the objective lens in accordance with the tilt of the optical disk is often used. It is also possible to remove coma aberration due to the lens shift amount with such a tilt actuator.

  FIG. 20 is a diagram illustrating a schematic configuration of an actuator unit in Example 9 of the third embodiment. As shown in FIG. 20, the actuator unit 106 includes an objective lens 105 and an objective lens holder 115 that holds the objective lens 105. In addition, a base portion 116 that supports the objective lens holder 115 and elastic support mechanisms 117 a and 117 b interposed between the base portion 116 and the objective lens holder 115 are provided. The elastic support mechanisms 117a and 117b elastically support the objective lens holder 115 with respect to the base portion 116 so that the objective lens holder 115 can move in a total of three directions including a focus direction, a tracking direction, and a radial tilt direction. Here, the focus direction refers to the Z-axis direction (optical axis direction of the objective lens 105) shown in FIG. 20, and the tracking direction refers to the X-axis direction (radial direction of the optical recording medium 107) shown in FIG. .

  The radial tilt direction refers to the tilt direction around the Y axis shown in FIG. 20 (the tilt direction with respect to the radial direction of the optical recording medium 107). In addition, a driving unit (not shown in FIG. 20) is provided. The driving unit includes, for example, a permanent magnet provided on the objective lens holder 115 and a driving coil fixed relative to the base portion 116. It is comprised by what is called a voice coil motor.

  The driving means drives the objective lens holder 115 in the three directions according to the input current to the driving coil. Focus servo and tracking servo for controlling a current input to the drive coil of the drive means to follow a predetermined light beam spot on the recording track on the information recording surface of the optical recording medium 107, and tilt servo in accordance with the lens shift Is configured to do. The tilt servo may cancel the coma aberration generated by the disc tilt together.

  As for the lens shift amount of the objective lens 105, a position sensor for detecting the position of the objective lens 105 itself may be mounted on the actuator movable portion, or a decrease in the RF signal amplitude or the track error signal amplitude may be detected. .

  Next, as a means for canceling coma in Example 10 of Embodiment 3, a method of adding coma according to the lens shift amount may be used. A liquid crystal element is known as means for adding coma aberration itself. What is necessary is just to arrange | position this liquid crystal element in the middle of an optical path. In general, a quarter wave plate and an objective lens are desirable for polarization selectivity.

  FIG. 21 is a schematic configuration of the liquid crystal element in Example 10, (a) is a cross-sectional view, and (b) is a diagram showing an electrode pattern. The operation principle of the liquid crystal element will be described with reference to FIGS. 21 (a) and 21 (b). The liquid crystal element of Example 10 includes a liquid crystal element that imparts an astigmatism amount opposite in polarity to the astigmatism amount, and is disposed so as to generate coma aberration in the radial direction.

  Further, the liquid crystal element 50 of the tenth embodiment has a known configuration in Patent Documents 2 and 3 and the like. Glass substrates 51a and 51b are bonded by a conductive spacer 52 to form a liquid crystal cell. On the inner surface of the glass substrate 51a, the transparent electrode 54a, the insulating film 55 and the alignment film 56 are arranged in this order from the inner surface. On the inner surface of the glass substrate 51b, the transparent electrode 54b and the insulating film 55 are formed from the inner surface. The alignment film 56 is coated in this order. The electrode 54a is wired in a pattern so that it can be connected to the control circuit by a connection line at the electrode lead-out portion 57. The electrode 54b is electrically connected to the electrode 54a formed on the glass substrate 51a by the conductive spacer 52.

  Therefore, the electrode 54 b is connected to the control circuit of the liquid crystal element 50 by the connection line at the electrode lead portion 57. A liquid crystal 53 is filled inside the liquid crystal cell. The liquid crystal 53 has a so-called birefringence effect, and the refractive index is different between the optical axis direction of the liquid crystal molecules and the direction perpendicular thereto. Then, by changing the voltage applied between the electrode 54a and the electrode 54b, the direction of the liquid crystal molecules can be freely changed from the horizontal direction to the vertical direction. The voltage applied to the electrodes 54a and 54b is set by a control circuit (not shown), and the voltage applied to each divided region of the electrodes 54a and 54b is adjusted to be different for each region formed by each divided electrode. It gives a phase difference.

  FIG. 21B is an electrode pattern showing a state in which the electrode 54a of the liquid crystal element 50 is divided so as to cancel the coma aberration in the radial direction. As shown in FIG. 21B, the electrode 54a is divided into three pattern electrodes 60a, 60b, and 60c. Since the coma aberration is given by a wavefront aberration in the form of a cubic function, for example, the coma aberration can be generated by generating an inverted phase between the pattern electrode 60b and the pattern electrode 60c with the pattern electrode 60a as a zero reference.

  FIG. 22 is a transparent perspective view showing a schematic configuration of the optical information processing apparatus according to Embodiment 4 of the present invention. As shown in FIG. 22, the optical information processing apparatus 35 is an apparatus that performs one or more of recording, reproducing, and erasing of information with respect to the optical recording medium 107 using the optical pickup 30. In the fourth embodiment, the optical recording medium 107 has a disk shape and is stored in the protective case 32. The optical recording medium 107 is inserted and set together with the protective case 32 from the insertion port 34 into the optical information processing device 35 in the direction of the arrow “disc insertion”, rotated by the spindle motor 37, and recorded, reproduced, or erased by the optical pickup 30. Is done. The optical recording medium 107 does not need to be placed in the protective case 32 and may be in a naked state. In addition, as the optical pickup 30 in the fourth embodiment, the optical pickup described in the first to third embodiments can be used as appropriate.

  The optical pickup and the optical information processing apparatus according to the present invention realize two-wavelength or three-wavelength compatibility, can lay out the optical path of an optical system with a short object distance, and can form a compact compatible optical system. , It is useful as an optical pickup and an optical information processing apparatus having compatibility in an optical recording medium of a CD.

BRIEF DESCRIPTION OF THE DRAWINGS (a) which shows schematic structure of the optical pick-up compatible with blue / CD in Example 1 of Embodiment 1 of this invention is a side view, (b) is a top view Detailed view showing light emitting / receiving unit for CD Optical path diagram of CD system only shown in FIG. The figure which shows schematic structure of the blue / CD compatible optical pick-up in Example 2 of this Embodiment 1. FIG. Optical path diagram of only the CD optical system shown in FIG. The figure which shows schematic structure of the blue / CD compatible optical pick-up in Example 3 of this Embodiment 1. FIG. Optical path diagram of only the CD optical system shown in FIG. The figure which shows schematic structure of the blue / CD compatible optical pick-up in Example 4 of this Embodiment 1. FIG. Optical path diagram of only the CD optical system shown in FIG. (A) is a side view and (b) is a top view showing a schematic configuration of a blue / DVD / CD compatible optical pickup in Example 5 of Embodiment 2 of the present invention. Optical path diagram of CD system only in FIG. Diagram explaining opening restriction function The figure which shows schematic structure of the blue / DVD / CD compatible optical pick-up in Example 6 of this Embodiment 2. FIG. Optical path diagram of CD system only shown in FIG. The figure which shows schematic structure of the blue / DVD / CD compatible optical pick-up in Example 7 of this Embodiment 2. FIG. Optical path diagram of only the CD optical system shown in FIG. The figure which shows schematic structure of the blue / DVD / CD compatible optical pick-up in Example 8 of this Embodiment 2. FIG. Optical path diagram of only the CD optical system shown in FIG. (A) in the objective lens shift and coma aberration, (b) shows the relationship between the DVD optical system and (b) the CD optical system. The figure which shows schematic structure of the actuator part in Example 9 of this Embodiment 3. FIG. It is a schematic structure of the liquid crystal element in Example 10 of this Embodiment 3, (a) is sectional drawing, (b) is a figure which shows an electrode pattern A transparent perspective view showing a schematic configuration of an optical information processing apparatus in Embodiment 4 of the present invention (A) is blue, (b) is a DVD, and (c) is a diagram showing aberration characteristics of a CD generated at the time of condensing with a difference in wavelength. Wavefront aberration and object distance (a) shows the characteristics of the DVD optical system, and (b) shows the characteristics of the CD optical system. (A) after correction by incidence of a finite system, and (b) shows the wavefront aberration of a CD. The figure which shows the structure of the conventional optical pick-up compatible with blue / DVD / CD

Explanation of symbols

30 Optical Pickup 32 Protective Case 34 Insertion Port 35 Optical Information Processing Device 37 Spindle Motor 38 Carriage 50 Liquid Crystal Elements 51a and 51b Glass Substrate 52 Conductive Spacer 53 Liquid Crystal 54a and 54b Electrode 55 Insulating Film 56 Orientation Film 57 Electrode Leads 60a and 60b , 60c Pattern electrode 101 CD light receiving / emitting unit 101a CD semiconductor laser 101b 45 ° etched mirror 101c CD light receiving element 102, 202, 302, 402, 502, 602, 702, 802 CD hologram element 102a, 502a Hologram formation Surfaces 103 and 303 Dichroic prism 103a Dichroic mirror surface 104 1/4 wavelength plate 105 with aperture restriction Objective lens 106 Actuator unit 107 Optical recording medium (optical disk)
107a Optical recording medium (CD system)
107b Optical recording medium (blue)
107c Optical recording medium (DVD system)
108 Blue Semiconductor Laser 109 Collimating Lens 110 Polarizing Beam Splitter 111 Condensing Lens 112 Beam Splitting Element 113 Light Receiving Element 115 Objective Lens Holder 116 Base Part 117a, 117b Elastic Support Mechanism 118 DVD Semiconductor Laser 119 Coupling Lens 121 Compound Prism 123 , 323 Trichromatic prism 123a Trichromatic mirror surfaces 202a, 602a Lens function hologram forming surfaces 202b, 302b, 402b, 602b, 702b, 802b Deflection separating hologram forming surfaces 302a, 402a, 702a, 802a Astigmatism correction function hologram forming surfaces 403 Wedge-shaped dichroic prism 423 Wedge-shaped trichroic prism

Claims (16)

Two light sources having wavelengths λ1 and λ2 (λ1 <λ2), an infinite system for the light of wavelength λ1, an objective lens used for incidence of a finite system for the light of wavelength λ2, and the wavelength λ1 In an optical pickup provided with a dichroic prism that reflects light and transmits light having the wavelength λ2,
An optical pickup characterized in that the objective lens and the light source having the wavelength λ2 are arranged to face each other through the dichroic prism.   A light emitting / receiving unit in which a light receiving element for detecting reflected light from the light source having the wavelength λ2 and the optical recording medium having the wavelength λ2 is housed in the same container, and an optical path to the light receiving element between the dichroic prism and the light receiving / emitting unit The optical pickup according to claim 1, further comprising a hologram element that deflects the light beam.   3. The optical pickup according to claim 1, further comprising a hologram element that changes a radiation angle of light emitted from the light source having the wavelength λ2 between the dichroic prism and the light source having the wavelength λ2.   3. The optical pickup according to claim 1, further comprising a hologram element that adds astigmatism to light emitted from the light source having the wavelength λ2 between the dichroic prism and the light source having the wavelength λ2.   5. The optical pickup according to claim 1, wherein the dichroic prism is a wedge-shaped beam shaping prism that reflects back light emitted from a light source having a wavelength λ <b> 1. Three light sources with wavelengths λ1, λ2, and λ3 (λ1 <λ2 <λ3), and an objective that is used for incidence of an infinite system for the light of wavelength λ1 and a finite system for the light of wavelengths λ2 and λ3. In an optical pickup including a lens and a trichromatic prism that reflects the light of the wavelengths λ1 and λ2 and transmits the light of the wavelength λ3,
An optical pickup characterized in that the objective lens and the light source having the wavelength λ3 are arranged to face each other through the trichromatic prism.   The light receiving / emitting unit in which the light source having the wavelength λ3 and the light receiving element for detecting the reflected light from the optical recording medium having the wavelength λ3 are housed in the same container, and the light receiving element between the trichroic prism and the light receiving / emitting unit. The optical pickup according to claim 6, further comprising a hologram element that deflects an optical path.   8. The optical pickup according to claim 6, further comprising a hologram element that changes a radiation angle of light emitted from the light source having the wavelength λ3 between the trichromatic prism and the light source having the wavelength λ3.   8. The optical pickup according to claim 6, further comprising a hologram element for adding astigmatism to the light emitted from the light source having the wavelength λ3 between the trichroic prism and the light source having the wavelength λ3.   10. The optical pickup according to claim 6, wherein the trichroic prism is a wedge-shaped beam shaping prism that reflects light emitted from a light source having wavelengths λ <b> 1 and λ <b> 2 on the back surface.   An actuator mounted with an objective lens and tilting in the radial direction of the optical recording medium is provided, and the tilting amount of the actuator is adjusted according to the amount of optical axis deviation between the objective lens and the light source of wavelength λ2. The optical pickup according to claim 1.   A liquid crystal element for adding coma aberration to an incident light beam of an objective lens is provided, and the amount of coma aberration of the liquid crystal element is adjusted according to the amount of optical axis deviation between the objective lens and the light source having the wavelength λ2. Item 6. The optical pickup according to any one of Items 1 to 5.   An actuator mounted with an objective lens and tilting in the radial direction of the optical recording medium is provided, and the tilting amount of the actuator is adjusted according to the amount of optical axis deviation between the objective lens and the light source of wavelength λ3. The optical pickup according to claim 6.   A liquid crystal element for adding coma aberration to an incident light beam of the objective lens is provided, and the amount of coma aberration of the liquid crystal element is adjusted according to the amount of optical axis deviation between the objective lens and the light source having the wavelength λ3. Item 10. The optical pickup according to any one of Items 6 to 10.   10. The optical pickup according to claim 2, wherein the hologram element is formed integrally with a light receiving / emitting unit.   An optical information processing apparatus that performs at least one of recording, reproducing, and erasing of information on an optical recording medium using at least one light source having wavelengths λ1, λ2, and λ3 (λ1 <λ2 <λ3). An optical information processing apparatus using the optical pickup according to any one of 1 to 15.

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