JP5099196B2 - Coupling lens and optical pickup device - Google Patents

Description

The present invention relates to a coupling lens and an optical pickup device.

  (Prior Art 1) The molded lens includes a first surface having a first optical surface and a second surface having a second optical surface, and is one or substantially parallel to a plane including the optical axis of the molded lens. There is known a lens having two flat portions and the outer peripheral shape of the first optical surface and the second optical surface is not circular.

  (Prior Art 2) As a molded lens mold, one or two of a first surface having a first optical surface and a second surface having a second optical surface, which are substantially parallel to a plane including the optical axis, are provided. A molded lens mold for molding a molded lens having a flat portion is known.

  (Prior Art 3) As a method for manufacturing a molded lens, a first surface having a first optical surface and a second surface having a second optical surface are provided, and further, substantially parallel to a plane including the optical axis of the molded lens. A method of manufacturing a molded lens having one or two flat portions is known.

  (Prior Art 4) In an optical pickup device including a semiconductor laser, a coupling lens, a mirror, and an objective lens in order from the light source side, a coupling lens including a collimator lens that makes diverging light substantially parallel light is from the light source side. An optical pickup device having a first surface having a first optical surface and a second surface having a second optical surface, having no flat portion substantially parallel to the plane including the optical axis and having a circular outer surface is known. It has been.

  However, as a problem of (Prior Art 1), for example, when applied as a coupling lens of an optical pickup device, the accuracy of astigmatism is required to be 0.02 (or 0.03) λrms or less in terms of transmitted wavefront aberration. The However, λ is the wavelength of the semiconductor laser as the light source. For example, λ = 650 nm when the optical information recording medium is DVD, and λ = 780 nm when the optical information recording medium is CD. If flat portions are provided on the optical surfaces of the first surface and the second surface of the molded lens, there is a problem in that internal distortion or the like at the time of molding processing occurs and it is difficult to satisfy the required accuracy.

An object of the first invention is to provide a coupling lens that is small in the direction perpendicular to the optical axis, has good optical accuracy, and has particularly low astigmatism.

  The problem of (Prior Art 4) is that the coupling lens for a light source used in the optical pickup device has a high height in the direction orthogonal to the optical information recording medium, and the overall height of the optical pickup device also increases.

It is an object of the second invention to provide an optical pickup device having a coupling lens with a low height in the direction orthogonal to the optical information recording medium and a high accuracy.

  The object of the first invention can be achieved by any of the following means.

A coupling lens used in an optical pickup device for converting a divergence angle of light emitted from a semiconductor laser of the optical pickup device, wherein the coupling lens includes a first surface having a first optical surface, and the first surface. A second flat surface having a second optical surface on the opposite side of the surface, a first flat portion substantially parallel to a plane including the optical axis of the coupling lens, and a position symmetrical to the first flat portion with respect to the plane And the outer peripheral shape of the first optical surface has two straight lines substantially parallel to the first flat portion and the second flat portion, respectively, when viewed in the optical axis direction, The outer peripheral shape of the second optical surface has two straight lines substantially parallel to each of the first flat portion and the second flat portion, and at least other than the straight line of the first optical surface and the straight line of the second optical surface. Each of the first and second optical surfaces has outer peripheral surfaces at the outer peripheral portions, Coupling lens characterized by having a gate opening on the sides of a plane outer peripheral surface of the first flat portion connecting said second flat portion.

  The object of the second invention can be achieved by any of the following means.

In order from the light source side, a semiconductor laser, a coupling lens, an optical pickup apparatus having an optical system of a mirror and the objective lens, the coupling lens in the coupling lens according to any one of 4 from the claim 1 And the first flat portion substantially parallel to the plane including the optical axis of the coupling lens is substantially parallel to the imaging surface of the optical information recording medium at the position where the optical system forms an image. Pickup device.

  Since it comprised as mentioned above, there exist the following effects.

According to the coupling lens of the present invention, the lens is small and highly accurate in the direction orthogonal to the optical axis.

  According to the optical pickup device of the present invention, the optical pickup device has a light source coupling lens having a low optical height and a high optical accuracy in the direction orthogonal to the optical information recording medium.

It is a perspective view which shows the external appearance of the molded lens of this invention. It is a figure which shows each surface and principal part cross section of the molded lens shown in FIG. It is explanatory drawing of the 1st, 2nd optical surface of a shaping | molding lens. It is a perspective view which shows the external appearance of the other molded lens of this invention. It is a perspective view which shows the external appearance of the other molded lens of this invention. It is a perspective view which shows the external appearance of the other molded lens of this invention. It is a perspective view which shows the external appearance of the other molded lens of this invention. It is a perspective view which shows schematic structure of the optical pick-up apparatus of this invention.

  The molded lens, molded lens mold, molded lens manufacturing method and optical pickup apparatus of the present invention will be described with reference to the drawings.

  In each drawing, X indicates the optical axis direction of the molded lens, Y indicates the direction orthogonal to the optical axis, and Z indicates the direction in which the X direction and the Y direction are orthogonal to each other.

(First embodiment)
The molded lens according to the embodiment will be described. FIG. 1 is a perspective view showing an appearance of a molded lens, FIG. 2 is a diagram showing a cross section of each surface and main parts of the molded lens shown in FIG. -B sectional view (b), front view (c) of molded lens, bottom view (d) of molded lens, and AA sectional view (e) of molded lens are shown. FIG. 3 is an explanatory diagram of the first and second optical surfaces of the molded lens.

  As shown in FIGS. 1 and 2, the molded lens 1 </ b> A is a positive lens suitable for a semiconductor laser coupling lens. This molded lens 1A has a first surface 1a having a first optical surface and a second surface 1b having a second optical surface on the opposite side to the first surface.

  The first surface 1a includes a first optical surface 11a and an outer peripheral surface 12a that is the outer periphery of the first optical surface, and the outer peripheral shape of the first optical surface 11a is circular. Further, the first optical surface 11a corrects optical errors at the time of molding, errors in the mold, and the like. The second surface 1b includes a second optical surface 11b and an outer peripheral surface 12b that is an outer periphery of the second optical surface.

  Further, the molded lens 1A has a first flat portion 1c substantially parallel to a plane including the optical axis 2 (Z direction), and a second flat portion 1d at a position symmetrical to the first flat portion 1c with respect to this plane. ing. In FIG. 1, the height H1 indicates the distance between the optical axis 2 and the first flat portion 1c, and the height H2 indicates the distance between the optical axis 2 and the second flat portion 1d. The molded lens 1A is provided with a gate port 1g for molding at the intersection of the plane including the optical axis 2 (Z direction) and the side wall of the molded lens 1A.

  Here, the first optical surface 11a and the second optical surface 11b will be described with reference to FIG. 3 as an example. The first optical surface 11a is optically designed so that the outer peripheral shape is circular.

  In the Y direction of the molded lens 1A, as shown in FIG. 3A, the light beam emitted from the semiconductor laser enters the coupling lens, which is a molded lens, at the maximum opening angle θ1. On the other hand, in the Z direction of the molded lens 1A, as shown in FIG. 3B, the light beam emitted from the semiconductor laser enters the coupling lens at the maximum opening angle θ2. As will be described in detail later, the angle θ2 is larger than the angle θ1 so that the luminous flux due to the adjustment of the diaphragm (26 in FIG. 8) can cope with the change.

  With the above configuration, the molded lens is a lens suitable for a coupling lens mainly for a semiconductor laser. Specifically, the first optical surface 11a has a circular shape so that it is easy to correct an optical error, a mold error, and the like at the time of molding, and has high accuracy. Further, the height in the direction perpendicular to the optical information recording medium can be reduced by the first flat portion 1c. Further, the second flat portion 1d makes it easy to secure a design space for other mechanisms. In the Z direction, the aperture is adjusted so as to prevent the light beam from being cast by the molded lens 1A.

(Second Embodiment)
Another molded lens of the embodiment will be described. FIG. 4 is a perspective view showing the appearance of another molded lens of the present invention.

  As shown in FIG. 4, the molded lens 1B is a lens having only the first flat portion 1c of the molded lens 1A described above. The same parts are denoted by the same reference numerals and a part of the description is omitted.

  The molded lens 1B is a positive lens, and is a lens suitable mainly as a coupling lens for a semiconductor laser. The molded lens 1B includes a first surface 1a having a first optical surface, and a second surface 1b having a second optical surface on the opposite side to the first surface.

  The first surface 1a includes a first optical surface 11a and an outer peripheral surface 12a that is an outer periphery of the first optical surface. The outer peripheral shape of the first optical surface 11a is circular. Further, the first optical surface 11a corrects optical errors during molding, mold errors, and the like.

  With the above configuration, the molded lens 1B is a lens suitable for a coupling lens mainly for a semiconductor laser. Specifically, the outer peripheral shape of the first optical surface 11a is circular so that it is easy to correct optical errors, mold errors, etc. during the molding process, and has high accuracy. Further, the height in the direction perpendicular to the optical information recording medium can be reduced by the first flat portion 1c. In the Z direction, the aperture is adjusted so that the light beam is not blocked by the molded lens 1B.

(Third embodiment)
Another molded lens of the embodiment will be described. FIG. 5 is a perspective view showing the appearance of another molded lens of the present invention.

  As shown in FIG. 5, the molded lens 1 </ b> C is a lens in which the outer shape of the molded lens 1 </ b> A is rectangular. The same parts are denoted by the same reference numerals and a part of the description is omitted.

  The molded lens 1C is a positive lens, and is a lens suitable mainly for a coupling lens for a semiconductor laser. The molded lens 1C includes a first surface 1a having a first optical surface and a second surface 1b having a second optical surface on the opposite side to the first surface.

  The first surface 1a includes a first optical surface 11a and an outer peripheral surface 12a that is an outer periphery of the first optical surface. The outer peripheral shape of the first optical surface 11a is circular. Further, the first optical surface 11a corrects optical errors at the time of molding, errors in the mold, and the like.

  The second surface 1b includes a second optical surface 11b and an outer peripheral surface 12b that is the outer periphery of the first optical surface.

  Further, the molded lens 1C includes a first flat portion 1c and a second flat portion 1d, and further includes flat portions 1e and 1f in the Z direction.

  With the above configuration, the molded lens is a lens suitable for a coupling lens mainly for a semiconductor laser. Specifically, the outer peripheral shape of the first optical surface 11a is circular, so that correction of optical errors, mold errors, etc. during molding is facilitated and made highly accurate. Further, the height in the direction perpendicular to the optical information recording medium can be reduced by the first flat portion 1c. Further, the second flat portion 1d makes it easy to secure a design space for other mechanisms. In the Z direction, the aperture is adjusted so as to prevent the light beam from being cast by the molded lens 1A.

(Fourth embodiment)
Another molded lens of the embodiment will be described. FIG. 6 is a perspective view showing the appearance of another molded lens of the present invention.

  As shown in FIG. 6, the molded lens 1D is a positive lens, and is a lens suitable mainly for a coupling lens for a semiconductor laser.

  The molded lens 1D includes a first surface 1a having a first optical surface and a second surface 1b having a second optical surface on the opposite side of the first surface 1a. The first surface 1a includes a first optical surface 11a and an outer peripheral surface 12a that is an outer periphery of the first optical surface. With the first optical surface 11a, optical errors during molding, mold errors, and the like are corrected. Yes. The second surface 1b is the surface opposite to the first surface 1a, and has only the second optical surface and no outer peripheral surface. The molded lens 1D has a first flat portion 1c and a second flat portion 1d.

  With the above configuration, the molded lens 1D is a lens that is suitable mainly for a coupling lens for a semiconductor laser. Further, the height in the direction perpendicular to the optical information recording medium can be reduced by the first flat portion 1c. Further, the second flat portion 1d makes it easy to secure a design space for other mechanisms. In the Z direction, the aperture is adjusted so as to prevent the light beam from being cast by the molded lens 1D. The outer peripheral shape of the first optical surface 11a is circular, so that it is easy to correct optical errors at the time of molding, errors in the mold, etc., so that the accuracy is high.

(Fifth embodiment)
Another molded lens of the embodiment will be described. FIG. 7 is a perspective view showing the appearance of another molded lens of the present invention.

  As shown in FIG. 7, the molded lens 1E is a positive lens having a rectangular outer shape, and is a lens mainly suitable for a coupling lens for a semiconductor laser.

  The molded lens 1E includes a first surface 1a having a first optical surface and a second surface 1b having a second optical surface on the opposite side to the first surface. The first surface 1a includes a first optical surface 11a and an outer peripheral surface 12a that is an outer periphery of the first optical surface. With the first optical surface 11a, optical errors during molding, mold errors, and the like are corrected. Yes. The second surface 1b is a surface opposite to the first surface 1a, and includes an outer peripheral surface 12b that is an outer periphery of the second optical surface 11b and the second optical surface. The molded lens 1E includes a first flat portion 1c and a second flat portion 1d, and further includes flat portions 1e and 1f in the Z direction.

  With the above configuration, the molded lens 1E is a lens suitable for a coupling lens mainly for a semiconductor laser. Further, the height in the direction perpendicular to the optical information recording medium can be reduced by the first flat portion 1c. Further, the second flat portion 1d makes it easy to secure a design space for other mechanisms. In the Z direction, the aperture is adjusted so as to prevent the light beam from being cast by the molded lens 1E.

  Here, the molded lens mold of the present invention includes a fixed mold and a movable mold. The molded lens mold is a mold for molding the molded lens of the present invention described in the first to fifth embodiments. The molded lens mold is a surface portion of the core that molds the first optical surface of the molded lens, and corrects optical errors such as astigmatism during molding of the molded lens. Further, although the core of the molded lens mold can be fixed by changing the phase with respect to the optical axis, the outer peripheral shape of the first optical surface of the molded lens 1E is not circular, so the phase of the core is not adjusted. Further, the surface shape of the core portion of the molded lens mold for molding the first optical surface is such that the first curve of the portion that intersects the plane including the optical axis of the molded lens and the portion that intersects the surface orthogonal to the plane. The second curve is different from the second curve.

  In the method for producing a molded lens of the present invention, a plastic material is molded by the above-described molded lens mold, and the molded lens described in the first to fifth embodiments is manufactured.

(Sixth embodiment)
The optical pickup device of the embodiment will be described. FIG. 8 is a perspective view showing a schematic configuration of the optical pickup device.

  As shown in FIG. 8, the optical pickup device 20 is a device that reproduces the optical information recording medium 50. The optical pickup device 20 includes an optical pickup unit 20A, a device driving unit 22, and the like.

  The optical pickup unit 20A includes an optical system such as a semiconductor laser 24, a branching prism 28, a coupling lens, a mirror 25, a diaphragm 26, and an objective lens 27. The semiconductor laser 24 irradiates in the X direction. The branching prism 28 has a 45 ° translucent part, allows light from the semiconductor laser to pass through, bends the reflected light from the optical information recording medium 50 by 45 °, and guides it to the light receiving part 29. The coupling lens that is the molded lens 1A is the lens described in the first embodiment, and has a first surface and a second surface in order from the semiconductor laser 24 side, and further includes a first flat portion 1c and a second flat portion 1d. have. The mirror 25 reflects the light beam in the X direction in the Y direction. The diaphragm 26 and the objective lens 27 are adjusted in the Z direction by the adjusting mechanism 23. The objective lens 27 forms an image of the light flux on the optical information recording medium 50. The device driving unit 22 drives the optical pickup unit 20A in the Z direction. The optical information recording medium 50 has a track T and is rotated by a rotating means (not shown).

  The first flat portion 1c substantially parallel to the plane including the optical axis of the molded lens 1A is substantially parallel to the imaging surface of the optical information recording medium 50 at the position where the optical system forms an image. The first flat portion 1c reduces the dimension between the optical axis and the first flat portion 1c. Therefore, the height H3 between the optical information recording medium 50 and the bottom surface of the optical pickup device can be reduced, and the optical pickup device can be made thin and compact.

  Here, main playback operations will be described. Laser light is emitted from the semiconductor laser 24 in the X direction, passes through the branching prism 28, is condensed by the coupling lens, is reflected by the mirror 25 in the Y direction, is further passed through the diaphragm 26, and is passed through the objective lens 27. To form an image on the optical information recording medium 50 and read the information on the track T. The diaphragm 26 and the objective lens 27 are finely adjusted in the Z direction by the adjusting mechanism 23. However, since the molded lens 1A has a speed of light that can correspond to the movement of the adjusting mechanism 23 in the Z direction, there is no loss of light.

  The optical pickup unit 20A is moved in the Z direction by the device driving unit 22 to read the information on the track T of the optical information recording medium 50, and the light receiving unit 29 performs photoelectric conversion to reproduce the information.

  In the embodiment, the molded lens 1A is used. However, when the upper space of the coupling lens is unnecessary, the molded lens 1B (see FIG. 4) may be used. In the embodiment, playback has been described. However, playback recording or only recording may be performed.

  With the above configuration, the optical pickup device 20 can reduce the height H3 in the Y direction orthogonal to the optical information recording medium 50, and a high-precision coupling lens provides a good optical system.

1A, 1B, 1C, 1D, 1E Molded lens 1a First surface 1b Second surface 11a First optical surface 11b Second optical surface 1c First flat portion 1d Second flat portion 1g Gate port 2 Optical axis 20 Optical pickup device H3 height

Claims (6)

A coupling lens that is used in an optical pickup device and converts a divergence angle of emitted light of a semiconductor laser of the optical pickup device,
The coupling lens includes a first surface having a first optical surface, and a second surface having a second optical surface on the side opposite to the first surface,
A first flat portion substantially parallel to a plane including the optical axis of the coupling lens, and a second flat portion at a position symmetrical to the first flat portion with respect to the plane,
When viewed in the optical axis direction, the outer peripheral shape of the first optical surface has two straight lines substantially parallel to the first flat portion and the second flat portion, respectively, and the outer peripheral shape of the second optical surface is the first There are two straight lines substantially parallel to each of the flat portion and the second flat portion,
At least the outer peripheral surface of each of the first and second optical surfaces other than the straight line of the first optical surface and the straight line of the second optical surface,
A coupling lens comprising a gate port on a side surface of the outer peripheral surface, which is a surface connecting the first flat portion and the second flat portion . Wherein the first flat portion second surface connecting the flat portion, the coupling lens according to claim 1, wherein the first substantially perpendicular to said second flat portion and the flat portion. Said gate opening, the coupling lens according to claim 1 or claim 2, characterized in that it is arranged substantially equidistant from said first planar portion and the second flat portion. Regarding the outer shape, the length parallel to the surface of the first flat portion or the second flat portion and passing through the optical axis is longer than the length passing through the optical axis from the first flat portion to the second flat portion. The coupling lens according to claim 1, wherein: In order from the light source side, in an optical pickup device equipped with an optical system of a semiconductor laser, a coupling lens, a mirror and an objective lens,
The coupling lens is the coupling lens described in any one of 4 from the claim 1, wherein the optical system is a plane and the first flat portions parallel substantially including the optical axis of the coupling lens is imaged An optical pickup device characterized by being substantially parallel to an imaging surface of an optical information recording medium at a position where the optical information is recorded. 6. The optical pickup device according to claim 5 , wherein the optical pickup device moves perpendicular to a track formed on the optical information recording medium.

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