JP2005134736A - Optical element, optical pickup, and optical disk drive - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical element, an optical pickup, and an optical disk drive whose functions are not deteriorated, even when wavelength variation is caused. <P>SOLUTION: In the optical element arranged in an optical path between a semiconductor laser 1 and a coupling lens 4 for making emitted light outgoing from the semiconductor laser nearly parallel rays of light, and constituted of an anamorphic lens 3 having different focal distances in directions parallel/vertical to the active layer of the semiconductor laser 1, the anamorphic lens 3 is constituted of a plurality of materials 3-1 and 3-2. Then, the anamorphic lens 3 is integrally constituted of the plurality of materials, further, the joining surface of the anamorphic lens is constituted of a cylindrical surface. Then, in addition to a beam shaping function, an achromatic work can be given, and wave front deterioration can be reduced against the wavelength variation due to an ambient temperature change etc. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention is used in an optical pickup optical system of an optical disk drive, a laser scanning optical system of an image forming apparatus such as a digital copying machine, a laser printer, a laser plotter, and a laser facsimile, etc. The present invention relates to an optical element that performs beam shaping, an optical pickup including the optical element, and an optical disc drive apparatus including the optical pickup.

  Parallel to the active layer of a semiconductor laser as an optical element used for an optical pickup of an optical disk drive, a laser scanning optical system of an image forming apparatus such as a digital copying machine, a laser printer, etc. An optical element composed of an anamorphic lens (also referred to as an anamorphic lens) having a beam shaping function having different focal lengths in a normal direction and a vertical direction is known. An example of an optical system using the optical element is shown in FIG.

  The optical system shown in FIG. 8 shows an example of an optical pickup of an optical disk drive. In this optical pickup, light emitted from the semiconductor laser 101 becomes a parallel beam by the coupling lens 102, passes through the beam splitter 103, The light is condensed by the objective lens 104 to form a minute light spot on a disk-shaped optical recording medium (referred to as an optical disk) 105. Then, the light reflected from the optical disk 105 passes through the objective lens 104 again to become substantially parallel light, the optical path is bent by the beam splitter 103, and enters the light receiving element (not shown). From the output of the light receiving element, the focus control signal of the objective lens 104, the track control signal, and the information signal of the optical disk 105 are detected.

The semiconductor laser 101 has a non-uniform light distribution, and as shown in FIG. 9, the intensity in the direction (θ //) parallel to the bonding surface (active layer) of the semiconductor laser and the direction perpendicular to this (θ⊥). Distribution is different. Typical values for the far-field image are θ // − 10 ° and θ⊥−30 °.
When such an anisotropic light beam is made substantially parallel light by the coupling lens 102 and condensed by the objective lens 104 as it is, the light spot formed becomes an ellipse.
As shown in FIG. 10, when the major axis direction of the elliptical spot 106 is irradiated in a state where it is orthogonal to the track 107 of the optical disk, light is irradiated to a plurality of tracks 107, so that leakage of information signals from adjacent tracks Troubles such as writing (crosstalk) and writing to adjacent tracks occur. As shown in FIG. 11, when the elliptical spot 106 is irradiated in a state where the major axis direction thereof is parallel to the track 107 of the optical disk, the resolution in the data recording direction is lowered, and good reproduction signal detection and information writing are performed. Can not be.

In view of this, attempts have been made to obtain a substantially circular light spot by using a beam shaping optical element and expanding the beam in a direction parallel to the active layer incident on the objective lens. As a beam shaping optical element, there is one in which a beam shaping optical system is configured only by an optical element composed of a single anamorphic lens, and the optical system is simplified (see, for example, Patent Document 1).
FIG. 12 is a diagram showing an example of a beam shaping optical system using a conventional anamorphic lens (for example, a cylindrical lens) 120, in which (a) is an XZ sectional view of the beam shaping optical system, and (b) is a beam shaping. It is YZ sectional drawing of an optical system. The XZ cross section includes a direction (θ //) parallel to the semiconductor laser bonding surface (active layer), and the YZ cross section includes a direction (θ⊥) perpendicular to the semiconductor laser bonding surface (active layer). It is. In this anamorphic lens 120, the focal length fy in the direction parallel to the active layer of the semiconductor laser is different from the focal length fy in the direction perpendicular to it, and fy> fx.

  Here, the disadvantages of the conventional anamorphic lens are described below. The refractive index of the material constituting the lens (glass, resin, etc.) is determined by the wavelength of light. The wavelength of the semiconductor laser changes depending on the temperature of the laser chip (change in ambient temperature and output change during recording / reproduction). Therefore, when an anamorphic lens is used with a semiconductor laser as a light source, a change in the refractive index of the anamorphic lens is inevitable. In particular, when the wavelength of the semiconductor laser is as short as 405 nm, the change in refractive index becomes significant. As discussed above, the anamorphic lens has a different focal length fx in the direction parallel to the active layer of the semiconductor laser and a focal length fy in the vertical direction. A difference is generated between the focal length changes Δfx and Δfy, and astigmatism occurs. For example, when an optical pickup of an optical disk drive device is configured using an anamorphic lens, an astigmatic difference occurs in the light spot on the disk surface due to wavelength fluctuation, and good signal reproduction / recording cannot be performed.

Therefore, an optical element as shown in FIG. 13 has been proposed as a configuration in which the performance of the anamorphic lens does not deteriorate even if the wavelength variation of the semiconductor laser occurs (see Patent Document 2).
FIG. 13 is a diagram showing an example of a configuration in which the performance of the anamorphic lens does not deteriorate even when the wavelength of the semiconductor laser fluctuates, where (a) is an XZ sectional view of the beam shaping optical system, and (b) is a beam. It is YZ sectional drawing of a shaping optical system. The anamorphic lens 111 in FIG. 13 is an anamorphic lens that converts the emitted light of the semiconductor laser 110 into a substantially parallel light at the same time as beam shaping. Furthermore, the anamorphic lens 111 is composed of two different glass materials (glass type 1 and glass type 2) 112 and 113 so that there is no difference between the focal length changes Δfx and Δfy in the respective directions even if the wavelength fluctuates. ing.

Japanese Utility Model Publication No. 63-118714 JP 2001-154153 A

Here, the disadvantages of the anamorphic lens described in Patent Document 2 will be described.
In the anamorphic lens 111 of FIG. 13, when the lens thickness or the curvature shape of the anamorphic surface is slightly shifted, astigmatism occurs due to a difference between fx and fy. For this reason, in order to suppress astigmatism, it is necessary to process the lens thickness and the curvature shape of the anamorphic surface with high accuracy. Until now, such anamorphic lenses have been used as optical systems for optical discs. It has not been put into practical use in optical systems that require strict management of wavefront aberrations.

The present invention has been made in view of the above circumstances, and a first object thereof is to provide an optical element having a configuration in which the performance of an anamorphic lens does not deteriorate even when wavelength fluctuation occurs.
Further, a second object of the present invention is to provide an optical system using an anamorphic lens by correcting even if there is a deviation in the lens thickness and the curvature shape of the anamorphic surface by external adjustment. It is an object of the present invention to provide an optical pickup having a configuration in which the performance of the apparatus is not lowered.
Furthermore, a third object of the present invention is to use an optical pickup using an optical element configured such that the performance of an anamorphic lens does not deteriorate even when wavelength variation occurs, and at the time of switching between reproduction and recording, or at an environmental temperature. An object of the present invention is to provide an optical disc drive apparatus capable of performing recording / reproduction with stable performance without deterioration of spot performance due to wavelength fluctuation due to change or the like.

As means for achieving the above object, the present invention adopts the following configuration.
According to a first aspect of the present invention, there is provided an optical element disposed in an optical path between a semiconductor laser and a coupling lens that converts the emitted light emitted from the semiconductor laser into substantially parallel light. In an optical element composed of anamorphic lenses having different focal lengths in a direction perpendicular to the direction parallel to the layer, the anamorphic lens is composed of a plurality of materials (claim 1).
According to a second configuration, in the optical element according to the first configuration, the anamorphic lens is integrally formed of a plurality of materials (claim 2).
Furthermore, the third configuration is characterized in that, in the optical element of the second configuration, the cemented surface of the anamorphic lens is a cylindrical surface.

According to a fourth configuration, in the optical element of the second or third configuration, the anamorphic lens includes two lenses made of different materials, and has a curvature in a plane parallel to the active layer of the semiconductor laser. The first surface and the final surface are negative when viewed from the semiconductor laser side (claim 4).
According to a fifth configuration, in the optical element of the fourth configuration, the anamorphic lens has a first surface having a curvature in a plane perpendicular to the active layer of the semiconductor laser as viewed from the semiconductor laser side. And the final surface is negative (claim 5).
Further, the sixth configuration is the optical element of the fourth or fifth configuration, wherein the Abbe number of the material on the side on which the emitted light emitted from the semiconductor laser is incident is ν ₁ , and on the side on which the emitted light from the semiconductor laser is emitted. When the Abbe number of the material is ν ₂ , ν ₁ <ν ₂ (claim 6).

The seventh configuration includes a semiconductor laser, a coupling lens that makes the emitted light emitted from the semiconductor laser substantially parallel light, an objective lens that focuses light on the optical recording medium, and light that travels toward the optical recording medium. In an optical pickup provided with a detection separation means for separating the signal light reflected by the optical recording medium and a light receiving element for converting the signal light into an electric signal, between the semiconductor laser and the coupling lens, An optical element having any one of the first to sixth configurations is provided (claim 7).
Further, an eighth configuration is characterized in that, in the optical pickup of the seventh configuration, the optical element includes an adjustment mechanism capable of moving in the light traveling direction between the semiconductor laser and the coupling lens. (Claim 8).
Further, the ninth configuration is characterized in that, in the optical pickup of the seventh configuration, the semiconductor laser and the optical element are provided with an adjustment mechanism capable of moving by integrating in a plane perpendicular to the light traveling direction. (Claim 9).

  In the tenth configuration, light from a semiconductor laser is shaped into a substantially circular beam by an optical element, converted into substantially parallel light by a coupling lens, and then condensed on a disk-shaped optical recording medium by an objective lens. In an optical disc drive apparatus that includes a pickup and performs recording, reproduction, or erasing of the optical recording medium, the optical pickup includes an optical pickup having any one of the seventh to ninth configurations. 10).

  In the first to sixth configurations of the present invention, there is provided an optical element disposed in a radiation light path between a semiconductor laser and a coupling lens that makes the radiation emitted from the semiconductor laser substantially parallel. In an optical element composed of an anamorphic lens having a beam shaping function having different focal lengths in a direction perpendicular to a direction parallel to the active layer of the anamorphic lens, the anamorphic lens is integrally formed of lenses made of a plurality of materials, An optical element that has an achromatizing function in addition to the beam shaping function due to the cemented surface of the anamorphic lens, and that has little wavefront degradation against wavelength fluctuations due to environmental temperature changes ( Beam shaping element) can be realized.

  Further, in the seventh configuration of the present invention, an optical pickup for shaping light from a semiconductor laser with an optical element, making the light substantially parallel with a coupling lens, and then condensing the light onto an optical recording medium with an objective lens In this case, as an optical element, beam shaping is performed using the optical element having any one of the first to sixth configurations, and further, an optical element having an achromatic action is used, so that at the time of switching between reproduction and recording, the environmental temperature It is possible to realize an optical pickup in which wavefront deterioration is small with respect to wavelength fluctuations due to changes and the like and spot performance is not deteriorated.

Furthermore, in the eighth configuration of the present invention, the astigmatism of the optical pickup can be suppressed by adjusting the position of the anamorphic lens in the optical axis direction between the semiconductor laser and the coupling lens. The processing accuracy of the anamorphic lens can be relaxed and the manufacture thereof can be simplified.
In the ninth configuration of the present invention, the positional relationship between the light emitting point and the anamorphic lens is adjusted, and the unit in which the light emitting point and the anamorphic lens are integrated is adjusted with respect to the coupling lens. Wavefront aberration can be sufficiently suppressed.

  Furthermore, in the 10th structure of this invention, in addition to the beam shaping function which mounts the optical element of any one of 1st-6th in the optical pick-up mounted in an optical disk drive device, the optical element which has an achromatic effect An optical disc drive that can perform stable recording and playback without deterioration of spot performance due to wavelength fluctuations caused by changes in playback and recording, or changes in environmental temperature, etc. An apparatus can be realized.

  Hereinafter, the best mode for carrying out the present invention will be described in detail based on the embodiments shown in the drawings.

(Example 1)
First, embodiments of the first, second, third, fourth and sixth configurations will be described.
FIG. 1 is a diagram showing an embodiment of a beam shaping optical system using an anamorphic lens 3 of the present invention, in which (a) is parallel to the bonding surface (active layer) of a semiconductor laser chip of the beam shaping optical system. Cross-sectional views (XZ cross-section) and (b) are cross-sectional views (YZ cross-section) orthogonal to the bonding surface (active layer) of the semiconductor laser chip of the beam shaping optical system. The light emitted from the semiconductor laser 1 is elliptical radiation light whose radiation angle in the direction parallel to the active layer (XZ cross section) is narrower than the radiation angle in the direction perpendicular to the active layer (YZ cross section). The emitted light passes through the glass substrate 2 (for example, a substrate such as a hologram element described later), passes through the anamorphic lens 3, and is a direction perpendicular to the active layer and a radiation angle in a direction parallel to the active layer (XZ cross section). The beam is shaped into circular radiation light having a substantially equal radiation angle (YZ cross section). This radiated light is transmitted through a coupling lens 4 (a coupling lens composed of a plurality of lenses and an aperture in the illustrated example) 4 composed of one or more lenses or the like, and is converted into parallel light.

  In this embodiment, the anamorphic lens 3 uses two types of glass materials 3-1 and 3-2 and is bonded together. Here, the anamorphic lens 120 made of the conventional anamorphic lens 120 shown in FIG. 12 and the two glass materials 3-1 and 3-2 of this embodiment shown in FIG. The wavefront aberration with respect to the wavelength variation 3 is shown in FIG. The horizontal axis of FIG. 2 shows the wavelength variation from the design center wavelength, and the vertical axis shows the wavefront aberration at that time. As can be seen from FIG. 2, by forming an anamorphic lens with a plurality of glass materials, it is possible to provide an achromatic action and suppress deterioration of wavefront aberration due to wavelength fluctuation. Such a beam shaping lens can be realized by satisfying the following conditional expressions 1 and 2.

Here, f _1x , f _1y , and ν ₁ indicate the x-direction focal length, y-direction focal length, and dispersion of the lens portion of the glass material 3-1, and f _2x , f _2y , and ν ₂ indicate the lens portion of the glass material 3-2. The x-direction focal length, y-direction focal length, and dispersion are shown, and f _CL and ν _CL show the focal length and dispersion of the coupling lens 4.
Conditional expression 1 is a condition for imparting an achromatic action, and the occurrence of astigmatism due to wavelength fluctuation is suppressed by matching the left side and the middle side of the formula, and the wavelength fluctuation is caused by bringing each side closer to 0. It becomes possible to suppress the deterioration of the wavefront aberration due to.
Conditional expression 2 is a condition that defines the shaping magnification M of the beam shaping.
In this embodiment, since f _{1y ≈f 2y ≈∞} , it is possible to simply replace the following conditional expressions 3 and 4 with conditional expressions 3 and 4.

Table 1 below shows an example of specific lens data of the anamorphic lens 3 made of the two types of glass materials of the present embodiment. Here, AAS in the table indicates an anamorphic surface having the surface shape of the anamorphic lens, and is represented by the following formula. Moreover, E described in the table represents “power of × 10”, and for example, E-04 is “× 10 ⁻⁰⁴ ”. Also, surface number 0 in the table is an object surface at infinity (INFINITY), and surface numbers 1 to 13 are the order of the surfaces viewed from the exit surface side of the coupling lens 4 in FIG. Corresponds to the surfaces s1 to s13 shown in FIG. Here, s1 is an aperture surface such as an aperture, s2 to s6 are lens surfaces of the coupling lens 4, s8 to s10 are anamorphic surfaces of the anamorphic lens 3, s11 and s12 are surfaces of the glass substrate 2, and s13 is a semiconductor. This is an emission surface of the laser 1.

(Anamorphic surface)
Z = [{(1 / RX) · x ² + (1 / RY) y ² } / {1 + √ {1- (1 + KX) · (1 / RX) ² · x ^2- (1 + KY)・ (1 / RY) ²・ y ² }}]
+ AR {(1-AP) x 2 + (1 + AP) y 2} 2 + BR {(1-BP) x 2 + (1 + BP) y 2} 3
+ CR {(1-CP) x 2 + (1 + CP) y 2} 4 + DR {(1-DP) x 2 + (1 + DP) y 2} 5
Z: Sag of a plane parallel to the Z axis.
RX, RY: Radius of curvature in the X and Y directions.
KX, KY: Conic coefficients in the X and Y directions.
AR, BR, CR, DR: Represents 4th, 6th, 8th, and 10th order rotationally symmetric parts from the cone.
AP, BP, CP, DP: Represents non-rotation symmetric parts deformed from 4th, 6th, 8th, 10th order from the cone.

As is clear from the constituent glass material, lens surface shape, and lens data of the anamorphic lens 3 of the present invention, the anamorphic lens 3 of this embodiment is composed of two lenses 3-1 and 3-2 made of different materials. It is constructed, and its bonding surface is a cylinder surface. By making the bonding surface a cylinder surface, astigmatism due to wavelength fluctuations can be more effectively suppressed. The anamorphic lens 3 has a negative curvature in the direction parallel to the active layer on the first surface and the final surface when viewed from the semiconductor laser 1 side. As a result, the beam is expanded in a direction parallel to the active layer. However, since Table 1 is viewed from the coupling lens 4 side, the radius of curvature RX in the direction parallel to the active layer is marked as positive.
In the anamorphic lens 3 of this embodiment, the Abbe number ν ₁ of the material (glass material) on the side on which the light from the semiconductor laser 1 is incident is ν ₁ = 44.7, and the light from the semiconductor laser 1 is emitted. The Abbe number ν ₂ of the side material (glass material) is ν ₂ = 53.3, so ν ₁ <ν ₂ .

(Example 2)
Next, an example of the fifth configuration will be described.
FIG. 3 is a diagram showing an embodiment of a beam shaping optical system using the anamorphic lens 3 of the present invention, in which (a) is parallel to the bonding surface (active layer) of the semiconductor laser chip of the beam shaping optical system. Cross-sectional views (XZ cross-section) and (b) are cross-sectional views (YZ cross-section) orthogonal to the bonding surface (active layer) of the semiconductor laser chip of the beam shaping optical system.
The light emitted from the semiconductor laser 1 is elliptical radiation light whose radiation angle in the direction parallel to the active layer (XZ cross section) is narrower than the radiation angle in the direction perpendicular to the active layer (YZ cross section). The emitted light passes through the glass substrate 2, passes through the anamorphic lens 3, and the radiation angle in the direction parallel to the active layer (XZ section) and the radiation angle in the direction perpendicular to the active layer (YZ section) are substantially equal. Beam-shaped into circular radiation. This radiated light passes through the coupling lens 4 and is converted into parallel light.

In this embodiment, the basic configuration of the beam shaping optical system is the same as that of the first embodiment, but by dispersing the curvature on the spherical surface of the coupling lens 4 in the anamorphic lens 3, The number of lenses is reduced. Therefore, the focal lengths f _1y and f _{2y in} the Y direction of the anamorphic lens 3 take a finite value, and the curvature in the direction perpendicular to the active layer of the anamorphic lens 3 is also negative on the first surface and the final surface. It has become.
Such a beam shaping lens can also be realized by satisfying conditional expression 1 and conditional expression 2 described above. Table 2 below shows an example of specific lens data of an anamorphic lens made of two kinds of glass materials of the present embodiment. Here, as in Example 1, AAS in the table represents the anamorphic surface of the surface shape of the anamorphic lens, and is represented by the above formula. In addition, E described in the table also represents “power of × 10” as described above. Further, surface number 0 in the table is an object surface at infinity (INFINITY), and surface numbers 1 to 10 are the order of the surfaces viewed from the exit surface side of the coupling lens 4 in FIG. Corresponds to the surfaces s1 to s10 shown in FIG. In addition, s1 is an aperture surface such as an aperture, s2 to s4 are lens surfaces of the coupling lens 4, s5 to s7 are anamorphic surfaces of the anamorphic lens 3, s8 and s9 are surfaces of the glass substrate 2, and s10 is a semiconductor. This is an emission surface of the laser 1.

(Example 3)
Next, examples of the seventh to ninth configurations will be described.
An example in which the anamorphic lens 3 having the first to sixth configurations of the present invention is mounted on an optical pickup is shown in FIG. 4A is a cross-sectional view of the optical pickup in the direction parallel to the active layer of the semiconductor laser, and FIG. 4B is a cross-sectional view of the optical pickup in the direction perpendicular to the active layer of the semiconductor laser. This optical pickup includes a semiconductor laser 1, a hologram element 2, a beam shaping lens 3, a coupling lens 4, a deflection mirror 5, an objective lens 6, and a signal detecting light receiving element 7. These components are not shown in the drawing. It is mounted on the system housing. Although not shown, the objective lens 6 is supported by an actuator for tracking and focusing, and is moved by the actuator in the optical axis direction and in a direction orthogonal to the optical axis and the track of the optical disc 8. Tracking and focusing control are performed. The beam shaping lens 3 shown in FIG. 4 has the same configuration as the anamorphic lens shown in any of the first to sixth configurations. For example, as shown in FIG. 1 (or FIG. 3), The morphic lens 3 has a configuration in which two types of glass materials 3-1 and 3-2 are used and are integrally bonded.

  In the optical pickup having the configuration shown in FIG. 4, the radiated light emitted from the semiconductor laser 1 passes through the hologram element 2, is shaped by the anamorphic lens 3, is converted into parallel light by the coupling lens 4, and is deflected by the deflecting prism 5. The light is reflected and condensed as a minute spot on the recording surface of the optical disk 8 by the objective lens 6. The light reflected from the optical disk 8 is collimated again by the objective lens 6, converged by the coupling lens 4, diffracted by the hologram element 2 through the anamorphic lens 3, and a light receiving element for signal detection. 7 is incident. Then, an information signal and a servo signal (focus control signal, track control signal) are generated from the output signal of the light receiving element 7 for signal detection.

The anamorphic lens 3 has a deviation in the lens thickness, the radius of curvature in the direction parallel to the active layer of the semiconductor laser 1 (X direction in FIG. 1), and the radius of curvature in the perpendicular direction (Y direction in FIG. 1). As a result, a difference occurs between the focal length fx in the direction parallel to the active layer of the semiconductor laser 1 and the focal length fx in the direction perpendicular to the focal length fx, resulting in astigmatism.
Therefore, in such a case, as a configuration for adjusting astigmatism, as shown in FIG. 5, the anamorphic lens 3 is placed between the semiconductor laser 1 and the coupling lens 4 in the optical axis direction (in the drawing). Astigmatism can be corrected by moving in the direction of arrow Z).

  FIG. 6 shows how the wavefront aberration is improved when the position is adjusted in the optical axis direction when there is a thickness shift in the anamorphic lens 3. In the conventional anamorphic lens 111 shown in FIG. 13, even if the lens is moved in the optical axis direction, the wavefront aberration does not change. However, the anamorphic lens 3 of this embodiment has the optical axis direction as shown in FIG. By moving the anamorphic lens 3 in the direction of arrow Z in the figure, the wavefront aberration is sufficiently reduced.

  Further, generally, when the angle (field angle) of light incident on the objective lens 6 is shifted, the wavefront aberration is deteriorated. For this reason, in most optical pickups, the angle of the light beam incident on the objective lens is adjusted by minutely moving the positional relationship between the light emitting point of the semiconductor laser and the center of the coupling lens in a plane perpendicular to the optical axis. . In the case of the conventional example shown in FIG. 13, when such adjustment is performed, coma aberration occurs in the anamorphic lens, and the spot on the disk surface is distorted to one side. On the other hand, in the configuration of the anamorphic lens 3 according to the present invention, the surface configuration of the beam shaping lens portion and the beam collimating lens portion is divided so that the coma aberration is minimized. By adjusting and fixing the positional relationship between the anamorphic lens 3 and the anamorphic lens 3 in a plane perpendicular to the optical axis, and adjusting the fixed unit in the plane perpendicular to the optical axis with respect to the coupling lens 4, The angle of view of the light beam incident on the lens 6 can be adjusted.

Example 4
Next, an example of the tenth configuration will be described.
FIG. 7 is a block diagram showing a configuration example of a control system of the optical disc drive apparatus according to the present invention. In the figure, reference numeral 8 denotes an optical disk, 10 denotes an optical pickup having the seventh to ninth configurations of the present invention (for example, the configurations shown in FIGS. 4 and 5), 11 denotes a signal arithmetic circuit, 12 denotes an actuator controller, 13 denotes an actuator driver, Reference numeral 14 denotes a laser controller, 15 denotes a laser driver, 16 denotes a spindle controller, 17 denotes a spindle driver, and 18 denotes a spindle motor that rotates the optical disk.
The optical disk drive apparatus having the configuration shown in FIG. 7 includes the optical pickup 10 having the seventh to ninth configurations (for example, the configurations shown in FIGS. 4 and 5) of the present invention, and the signal detecting light-receiving element 7 of the optical pickup 10. Is received by the signal calculation circuit 26 to generate an information signal and a servo signal. The servo signal is fed back to the actuator controller 12 and the actuator driver 13 to drive the actuator of the objective lens, and focusing control and tracking control are performed. Done.

  In the optical disk drive device of the present embodiment, the anamorphic lens having the configuration shown in Embodiment 1 or Embodiment 2 is used as the beam shaping lens of the optical pickup 10, thereby suppressing wavefront deterioration due to wavelength fluctuation. Therefore, it is possible to prevent the spot performance from being deteriorated. Therefore, even when switching between playback and recording with an optical disk drive, or even when the wavelength of the semiconductor laser fluctuates due to environmental temperature changes, spot performance does not deteriorate, and stable recording and playback operations can be ensured. Furthermore, it becomes possible to provide an optical disc drive apparatus suitable for manufacturing.

  In the optical element of the present invention, the anamorphic lens is formed integrally with a lens made of a plurality of materials, and the cemented surface of the anamorphic lens is formed of a cylindrical surface. Since the function can be provided, it is possible to realize an optical element (beam shaping element) having a small wavefront deterioration with respect to wavelength fluctuation due to environmental temperature change or the like. Therefore, as described in the third and fourth embodiments, the optical element of the present invention can be suitably used for an optical pickup of an optical disk drive device. The optical element of the present invention can also be suitably used in a writing laser scanning optical system of an image forming apparatus such as a digital copying machine, a laser printer, a laser plotter, or a laser facsimile. In a laser scanning optical system, when used as a beam shaping collimating lens that makes light from a semiconductor laser substantially parallel, deterioration due to wavelength fluctuations of the light spot that scans the image carrier can be suppressed. Thus, image writing with stable spot performance can be performed, and an image forming apparatus with good image quality can be realized.

It is a structure explanatory view showing one example of a beam shaping optical system using the optical element of the present invention. It is a figure which shows the value of the wavefront aberration with respect to the wavelength fluctuation | variation of the anamorphic lens which consists of two types of materials of this invention, and the anamorphic lens which consists of one type of conventional materials. It is a structure explanatory view showing another example of the beam shaping optical system using the optical element of the present invention. It is a configuration explanatory view showing an embodiment of an optical pickup using the optical element of the present invention. FIG. 5 is a configuration explanatory view showing an embodiment when adjusting astigmatism in the optical pickup shown in FIG. 4. In the optical pickup shown in FIG. 5, when the present invention and the conventional anamorphic lens are used and the anamorphic lens has a thickness deviation, the effect of improving the wavefront aberration when the position is adjusted in the optical axis direction. FIG. It is a block diagram which shows the structural example of the control system of the optical disk drive device which concerns on this invention. It is a figure which shows an example of the optical pick-up optical system of the conventional optical disk drive. It is a figure which shows the light emission distribution (relational angle and intensity | strength relationship) of a semiconductor laser. It is a figure which shows the state in which the major axis direction of the elliptical spot condensed on the optical disk orthogonally crossed the track. It is a figure which shows the state in which the major axis direction of the elliptical spot condensed on the optical disk is parallel to a track | truck. It is a figure which shows an example of the conventional beam shaping optical system. It is a figure which shows another example of the conventional beam shaping optical system.

Explanation of symbols

1: Semiconductor laser 2: Glass substrate (hologram element)
3: Anamorphic lens 4: Coupling lens 5: Deflection mirror 6: Objective lens 7: Light receiving element for signal detection 8: Optical disc (optical recording medium)
10: Optical pickup 11: Signal calculation circuit 12: Actuator controller 13: Actuator driver 14: Laser controller 15: Laser driver 16: Spindle controller 17: Spindle driver 18: Spindle motor

Claims (10)

An optical element disposed in an optical path between a semiconductor laser and a coupling lens that makes emitted light emitted from the semiconductor laser substantially parallel light, the direction being perpendicular to the direction parallel to the active layer of the semiconductor laser In optical elements consisting of anamorphic lenses with different focal lengths,
The optical element, wherein the anamorphic lens is composed of a plurality of materials. The optical element according to claim 1, wherein
The optical element, wherein the anamorphic lens is integrally formed of a plurality of materials. The optical element according to claim 2, wherein
An optical element, wherein a cemented surface of the anamorphic lens is a cylindrical surface. The optical element according to claim 2 or 3,
The anamorphic lens is composed of two lenses made of different materials, and the curvature in a plane parallel to the active layer of the semiconductor laser is negative on the first surface and the final surface when viewed from the semiconductor laser side. An optical element. The optical element according to claim 4, wherein
The optical element according to claim 1, wherein the first surface and the final surface of the anamorphic lens have a negative curvature in a plane perpendicular to the active layer of the semiconductor laser when viewed from the semiconductor laser side. The optical element according to claim 4 or 5,
When the Abbe number of the material on the side where the emitted light emitted from the semiconductor laser is incident is ν ₁ , and the Abbe number of the material on the side where the emitted light of the semiconductor laser is emitted is ν ₂ , ν ₁ <ν ₂ An optical element characterized by the above. A semiconductor laser, a coupling lens for making the emitted light emitted from the semiconductor laser substantially parallel light, an objective lens for condensing the light on the optical recording medium, and the light directed to the optical recording medium and reflected by the optical recording medium In an optical pickup comprising a detection and separation means for separating the signal light and a light receiving element for converting the signal light into an electrical signal,
An optical pickup comprising the optical element according to any one of claims 1 to 6 between the semiconductor laser and the coupling lens. The optical pickup according to claim 7, wherein
An optical pickup comprising an adjustment mechanism capable of moving the optical element in a light traveling direction between the semiconductor laser and the coupling lens. The optical pickup according to claim 7, wherein
An optical pickup comprising an adjusting mechanism capable of moving the semiconductor laser and the optical element by integrating them in a plane perpendicular to the light traveling direction. An optical pickup is provided for shaping the light from the semiconductor laser into a substantially circular shape by an optical element, making the light substantially parallel by a coupling lens, and then condensing the light onto a disk-shaped optical recording medium by an objective lens. In an optical disc drive apparatus for recording, reproducing or erasing a recording medium,
An optical disc drive apparatus comprising the optical pickup according to any one of claims 7 to 9 as the optical pickup.

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