JP2010020855A - Reflection type diffraction grating for a plurality of wavelengths and optical pickup device including the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain a low-cost reflection type diffraction grating for a plurality of wavelengths which allows a desired diffraction efficiency and diffraction direction to be set for each wavelength and matches three or more multiple wavelengths. <P>SOLUTION: The reflection type diffraction grating for the plurality of wavelengths is formed by layering a first reflection type diffracting grating 10, a second reflection type diffraction grating 20 and a third reflection type diffraction grating 30 in this order on a substrate 3. The first reflection type diffraction grating 10 has first reflection diffracting layers 12 reflecting and diffracting a first light beam of first to third light beams having wavelengths different from each other and transmitting other light beams and first phase adjusting layers 13 adjusting a phase of a wavefront of at least the second light beam of the transmitted second and third light beams. The second reflection type diffraction grating 20 has second reflection diffracting layers 22 reflecting and diffracting the second light beam and transmitting the third light beam and second phase adjusting layers 23 adjusting a phase of a wavefront of the transmitted third light beam. The third reflection type diffraction grating 30 has third reflection diffracting layers 32 reflecting and diffracting the third light beam. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention provides a reflection diffraction for multiple wavelengths arranged to reflect and diffract each light beam in a predetermined direction on an optical path where a plurality of light beams belonging to different wavelength bands are selectively output. The present invention relates to a grating and an optical pickup device including the same.

Conventionally, in an optical pickup device for recording and / or reproducing data on an optical recording medium such as a CD or a DVD, a diffraction grating is used for tracking control, power control of output light, and the like.
As such a diffraction grating, there is known a two-wavelength compatible type shared by two light beams belonging to different wavelength bands such as for CD and DVD (see Patent Documents 1 to 4 below).

  The diffraction gratings described in the following Patent Documents 1 and 2 are obtained by forming different diffraction gratings on both surfaces of a transparent substrate (hereinafter referred to as “double-sided type”), and diffraction formed on one surface of the substrate. The grating is configured to diffract only one of the two light beams, and the diffraction grating formed on the other surface of the substrate is configured to diffract only the other of the two light beams.

  The diffraction grating described in the following Patent Document 3 is obtained by dividing a single-sided region of a transparent substrate into two groups and forming different diffraction gratings in each grouped region (hereinafter referred to as “single-sided type”). A diffraction grating formed in one of the group regions diffracts only one of the two light beams, and a diffraction grating formed in the other group of the two light beams Only the other of them is diffracted.

  The diffraction grating described in the following Patent Document 4 is formed using a birefringent material so that the diffractive action differs depending on the wavelength and polarization state of the light beam.

JP 2003-6891 A JP 2007-334975 A JP 2004-327005 A International Publication WO2004 / 097819

  The double-sided diffraction grating described above has a large wavelength dependency of diffraction efficiency, and it is difficult to obtain a desired diffraction efficiency for each wavelength. In recent years, Blu-ray Discs (BD) using a light beam in the blue light range have been put into practical use, and along with this, the practical application of a three-wavelength compatible diffraction grating is desired. It is difficult to realize this.

Further, although the above-mentioned single-sided diffraction grating has been proposed for three wavelengths, unnecessary diffracted light is likely to be generated, and it is difficult to set a desired diffraction direction for each wavelength.
Moreover, since the diffraction grating using a birefringent material is expensive, there exists a problem that manufacturing cost increases.

  The present invention has been made in view of the above circumstances, and it is possible to set a desired diffraction efficiency and diffraction direction for each wavelength, and it can be used for a plurality of wavelengths at a low cost capable of dealing with multiple wavelengths of three or more wavelengths. It is an object of the present invention to provide a reflective diffraction grating and an optical pickup device including the same.

The multi-wavelength reflective diffraction grating according to the present invention includes first to Nth light beams belonging to first to Nth (N is an integer of 2 or more) different wavelength bands, respectively. Is a reflective diffraction grating for a plurality of wavelengths disposed on a selectively output optical path,
N reflective diffraction gratings from 1 to N are stacked in this order from the incident side of the N light beams,
The jth reflection type diffraction grating (j is an arbitrary integer from 1 to N-1) is the jth light beam out of the jth light beam to the Nth light beam incident on the jth reflection type diffraction grating. A j-th reflection diffractive layer for reflecting and diffracting other light beams;
The Nth reflection type diffraction grating has an Nth reflection diffraction layer for reflecting and diffracting the Nth light beam incident on the Nth reflection type diffraction grating,
The jth reflection type diffraction grating adjusts the phase of the wavefront of at least the (j + 1) th light beam from the (j + 1) th light beam to the Nth light beam transmitted through the jth reflection type diffraction grating. It has a phase adjustment layer.

Here, the j-th reflection diffraction layer has a characteristic of reflecting light in the j-th wavelength band and transmitting light in other wavelength bands from light in the j-th wavelength band to light in the N-th wavelength band. j dichroic film is arranged in a periodic uneven shape,
The Nth reflection diffractive layer is formed by periodically disposing an Nth dichroic film or a total reflection film having a characteristic of reflecting light in the Nth wavelength band. it can.

  Further, the position of the axis of the 0th-order diffracted light beam of the (j + 1) th light beam reflected and diffracted by the (j + 1) th reflection diffraction layer between the jth reflection type diffraction grating and the (j + 1) th reflection type diffraction grating. Is provided with a j-th axis position adjustment layer that matches the position of the 0th-order diffracted light axis of the j-th light beam reflected and diffracted by the j-th reflection diffraction layer.

Further, the reflective diffraction grating for multiple wavelengths according to the present invention, particularly as a three-wavelength compatible type, includes a first light beam belonging to the first wavelength band and a second wavelength band belonging to a second wavelength band different from the first wavelength band. A reflection type for multiple wavelengths in which two light beams and a third light beam belonging to a third wavelength band different from the first wavelength band and the second wavelength band are selectively output. A diffraction grating,
A first reflective diffraction grating, a second reflective diffraction grating, and a third reflective diffraction grating are stacked in this order from the incident side of the first light beam, the second light beam, and the third light beam,
The first reflection type diffraction grating reflects and diffracts the first light beam among the first light beam to the third light beam incident on the first reflection type diffraction grating and transmits the other light beam. A reflection diffraction layer, and a first phase adjustment layer for adjusting a phase of a wave front of at least the second light beam of the transmitted second light beam and the third light beam,
The second reflection type diffraction grating reflects and diffracts the second light beam of the second light beam and the third light beam incident on the second reflection type diffraction grating and transmits the third light beam. A second reflection diffraction layer and a second phase adjustment layer for adjusting the phase of the wavefront of the transmitted third light beam,
The third reflective diffraction grating has a third reflective diffraction layer that reflects and diffracts the third light beam incident on the third reflective diffraction grating,
The first reflective diffractive layer has a periodic concavo-convex shape on a first dichroic film having a characteristic of reflecting light in the first wavelength band and transmitting light in the second wavelength band and light in the third wavelength band. It is arranged in the
The second reflection diffraction layer is formed by arranging a second dichroic film having a characteristic of reflecting the light of the second wavelength band and transmitting the light of the third wavelength band in a periodic uneven shape. Yes,
The third reflective diffractive layer is formed by arranging a third dichroic film or a total reflection film having a characteristic of reflecting the light in the third wavelength band in a periodic uneven shape. Is.

Here, the position of the axis of the 0th-order diffracted light of the second light beam reflected and diffracted by the second reflective diffraction layer between the first reflective diffraction grating and the second reflective diffraction grating, A first axis position adjusting layer is provided to match the position of the axis of the 0th-order diffracted light of the first light beam reflected and diffracted by the first reflective diffraction layer;
The position of the axis of the 0th-order diffracted light beam of the third light beam reflected and diffracted by the third reflective diffraction layer between the second reflective diffraction grating and the third reflective diffraction grating is defined as the second reflective diffraction grating. It can be assumed that a second axis position adjusting layer is provided that matches the position of the axis of the 0th-order diffracted light of the second light beam reflected and diffracted by the reflection diffraction layer.

  An optical pickup device according to the present invention includes the above-described reflection diffraction grating for multiple wavelengths according to the present invention.

  The multi-wavelength reflection diffraction grating according to the present invention is formed by stacking N reflection diffraction gratings corresponding to N light beams having different wavelength bands, and each light beam includes: The other reflection type diffraction gratings are reflected and diffracted by a corresponding predetermined reflection type diffraction grating, and are disposed at a position closer to the incident side than the reflection type diffraction grating. In addition, at least the (j + 1) th light beam from the (j + 1) th light beam to the Nth light beam transmitted through the jth reflection type diffraction grating is wavefronted by the jth phase adjustment layer of the jth reflection type diffraction grating. Are adjusted to be incident on the next (j + 1) th reflective diffraction grating.

  As described above, according to the reflection diffraction grating for a plurality of wavelengths according to the present invention in which N reflection diffraction gratings are stacked and each of the reflection diffraction gratings is provided with a reflection diffraction layer and a phase adjustment layer, By appropriately forming the reflection diffraction layer and the phase adjustment layer in the reflection type diffraction grating, the diffraction efficiency and the diffraction direction for each light beam can be set to desired values.

  In addition, the reflection diffraction layer and the phase adjustment layer in each reflection type diffraction grating can be formed using a general-purpose film material having general versatility, so this is compared with a diffraction grating using a birefringent material. The reflective diffraction grating for multiple wavelengths according to the invention can be manufactured at low cost.

  In addition, according to the optical pickup device of the present invention, when recording and reproducing data on an optical recording medium corresponding to each light beam using light beams of a plurality of (especially three or more) wavelength bands different from each other. Tracking control and the like can be performed with high accuracy using the reflection diffraction grating for multiple wavelengths according to the present invention.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is a sectional view showing a schematic configuration of a reflection diffraction grating for multiple wavelengths according to a first embodiment of the present invention.

  A multi-wavelength reflective diffraction grating 1 of the first embodiment shown in FIG. 1 includes a first light beam (for example, a wavelength of 405 nm) belonging to a first wavelength band (for example, a blue light band) and a second wavelength band (for example, a blue wavelength band). A second light beam (for example, wavelength 655 nm) belonging to the green light band) and a third light beam (for example, wavelength 785 nm) belonging to the third wavelength band (for example, red light band or near infrared light band). The first reflection type diffraction grating 10 and the second reflection type diffraction are provided on a transparent substrate 3 formed of an optical glass material, etc. The grating 20 and the third reflection type diffraction grating 30 are laminated in this order from the light incident side (substrate 3 side).

The first reflective diffraction grating 10 is formed through a first base layer 11 (specifically, for example, a single layer of SiO _{2 having} a thickness of about 50 to 100 nm) formed on the substrate 3. The first reflection diffraction layer 12 is provided so as to form periodic irregularities in the middle and right and left directions, and the first phase adjustment layer 13 is formed on the first reflection diffraction layer 12. In addition, the 1st base layer 11, the 1st reflection diffraction layer 12, and the 1st phase adjustment layer 13 have a periodic structure in the left-right direction in a figure, and the number is attached | subjected only to those parts. .

The first reflection diffraction layer 12 is formed so that the first light beam is reflected and diffracted in a predetermined direction and the other light beams are transmitted through the respective light beams incident on the first reflection type diffraction grating 10. Specifically, it is composed of a first dichroic film composed of alternating layers of TiO ₂ and SiO ₂ .

The first phase adjustment layer 13 includes at least a second light beam and a third light beam transmitted through the first reflective diffraction grating 10 among the light beams incident on the first reflective diffraction grating 10. The phase of the wavefront of the light beam is adjusted (the phase of the wavefront of the second light beam at the time of incidence on the second reflective diffraction grating 20 is aligned) (the phase of the wavefront of the third light beam is also the same). Although adjusted, the phase of the wave front is not aligned at the time of incidence on the second reflective diffraction grating 20). Specifically, it is composed of a single layer of SiO ₂ . In FIG. 1, the first phase adjustment layer 13 is provided only on the stepped portion (recessed portion) of the first reflective diffraction layer 12, but not only the stepped portion but the first reflective diffraction grating 10 and You may make it provide the 1st phase adjustment layer 13 over the whole between the 2nd reflective diffraction gratings 20. FIG.

  The second reflective diffraction grating 20 is arranged in a horizontal direction in the figure through a second base layer 21 (configured in the same manner as the first base layer 11) formed on the first reflective diffraction grating 10. A second reflection diffraction layer 22 provided so as to form periodic irregularities, and a second phase adjustment layer 23 formed on the second reflection diffraction layer 22. In addition, the 2nd base layer 21, the 2nd reflection diffraction layer 22, and the 2nd phase adjustment layer 23 have a periodic structure in the left-right direction in a figure, and the number is attached | subjected only to those parts. .

The second reflection diffraction layer 22 is formed so that the second light beam of the second light beam and the third light beam incident on the second reflection type diffraction grating 20 is reflected and diffracted and the third light beam is transmitted. It is those which are, in particular and a second dichroic film made of alternating layers of Nb ₂ O _5, SiO _2.

The second phase adjustment layer 23 includes a phase of a wavefront of a third light beam transmitted through the second reflective diffraction grating 20 out of the two light beams and the third light beam incident on the second reflective diffraction grating 20. (The phase of the wavefront of the third light beam at the time of incidence on the third reflective diffraction grating 30 is made uniform), specifically, it is composed of a single layer of SiO ₂ . . In FIG. 1, the second phase adjustment layer 23 is provided only on the stepped portion (recessed portion) of the second reflective diffraction layer 12, but not only the stepped portion but also the second reflective diffraction grating 20. You may make it provide the 2nd phase adjustment layer 23 over the whole between the 3rd reflective diffraction gratings 30. FIG.

  The third reflective diffraction grating 30 includes a third base layer 31 (configured in the same manner as the first base layer 11 and the second base layer 21) formed on the second reflective diffraction grating 20. Accordingly, a third reflective diffraction layer 32 is provided so as to form periodic irregularities in the left-right direction in the figure. The third base layer 31 and the third reflective diffraction layer 32 have a periodic configuration in the left-right direction in the figure, and numbers are given to only a part of them.

The third reflective diffractive layer 32 is for the third light beam incident on the third reflecting type diffraction grating 30 is formed so as allowed to reflectively diffracted in a predetermined direction, particularly TiO ₂ and SiO ₂ The third dichroic film is composed of alternating layers.

  Note that each of the first dichroic film, the second dichroic film, and the third dichroic film described above is a multilayer film of about 10 to 20 layers (thickness 1000 to 2000 nm).

  Here, the reflection characteristics of the first dichroic film, the second dichroic film, and the third dichroic film will be described with reference to FIGS. 3 is a diagram showing the reflection characteristics of the first dichroic film, FIG. 4 is a diagram showing the reflection characteristics of the second dichroic film, and FIG. 5 is a diagram showing the reflection characteristics of the third dichroic film. In addition, the reflection characteristic of each figure is a case where an incident angle is 23 degree | times, the characteristic with respect to S polarized light is shown as the continuous line, and the characteristic with respect to P polarized light is shown with the dashed-dotted line.

  As shown in FIG. 3, the first dichroic film has a characteristic of reflecting the light of the first wavelength band and transmitting the light of the second wavelength band and the light of the third wavelength band. The reflectivity for one light beam is a high reflectivity close to 100% for both S-polarized light and P-polarized light.

  On the other hand, as shown in FIG. 4, the second dichroic film has a characteristic of reflecting the light of the second wavelength band and transmitting the light of the third wavelength band, and has a reflectivity with respect to the second light beam. Is approximately 100% for both S-polarized light and P-polarized light.

  Further, as shown in FIG. 5, the third dichroic film has a characteristic of reflecting the light in the third wavelength band, and the reflectance for the third light beam is approximately 100% for both S-polarized light and P-polarized light. It has become.

  The multi-wavelength reflective diffraction grating 1 configured in this way can be manufactured at low cost, and has a desired diffraction efficiency and diffraction for each of the first light beam, the second light beam, and the third light beam. It is possible to set the direction.

  Next, a reflection diffraction grating for multiple wavelengths according to a second embodiment of the present invention will be described. FIG. 2 is a sectional view showing a schematic configuration of a reflection diffraction grating for multiple wavelengths according to a second embodiment of the present invention.

  The multiple-wavelength reflective diffraction grating 2 of the second embodiment shown in FIG. 2 is disposed on an optical path through which the first light beam, the second light beam, and the third light beam are selectively output. A wavelength-corresponding type, on a transparent substrate 3A formed of an optical glass material or the like, a first reflective diffraction grating 10A, a first axis position adjusting layer 5, a second reflective diffraction grating 20A, a second axis position The adjustment layer 7 and the third reflective diffraction grating 30A are laminated in this order from the light incident side (substrate 3A side). As in FIG. 1, some of the numbers are omitted for those having a periodic configuration.

  The first reflective diffraction grating 10A has periodic irregularities in the horizontal direction in the figure via a first base layer 11A (configured in the same manner as the first base layer 11) formed on the substrate 3A. And a first phase adjustment layer 13A formed on the first reflection diffraction layer 12A. In FIG. 2, the first phase adjustment layer 13A is provided only on the stepped portion (the recessed portion) of the first reflective diffraction layer 12A, but not only the stepped portion and the first reflective diffraction grating 10A. The first phase adjustment layer 13 </ b> A may be provided over the entire area between the first axis position adjustment layer 5 described later.

The first reflective diffraction layer 12A is formed so that the first light beam is reflected and diffracted in a predetermined direction and the other light beams are transmitted through the respective light beams incident on the first reflective diffraction grating 10A. Specifically, the first dichroic film is composed of alternating layers of TiO ₂ and SiO ₂ .

The first phase adjustment layer 13A adjusts the phase of the wavefront of the second light beam that passes through the first reflective diffraction grating 10A among the light beams incident on the first reflective diffraction grating 10A (first axis). The phase of the wavefront of the second light beam at the time of entering the position adjusting layer 5 is made uniform, and specifically, it is composed of a single layer of SiO ₂ .

  The second reflective diffraction grating 20A is arranged in the left-right direction in the figure via a second base layer 21A (configured in the same manner as the second base layer 21) formed on the first reflective diffraction grating 10. A second reflection diffraction layer 22A provided so as to form periodic unevenness and a second phase adjustment layer 23A formed on the second reflection diffraction layer 22A are provided. In FIG. 2, the second phase adjustment layer 23A is provided only on the stepped portion (recessed portion) of the second reflective diffraction layer 22A, but not only the stepped portion but the second reflective diffraction grating 20A. You may make it provide the 2nd phase adjustment layer 23A over the whole between the 2nd axis position adjustment layers 7 mentioned later.

The second reflective diffraction layer 22A is formed so that the second light beam of the second light beam and the third light beam incident on the second reflective diffraction grating 20A is reflected and diffracted and the third light beam is transmitted. It is those which are, specifically, is configured from the second dichroic film made of alternating layers of Nb ₂ O _5, SiO _2.

The second phase adjusting layer 23A has a wavefront of a third light beam transmitted through the second reflective diffraction grating 20A out of the second light beam and the third light beam incident on the second reflective diffraction grating 20A. It is formed so as to adjust the phase (align the phase of the wavefront of the third light beam at the time of incidence on the second axis position adjusting layer 7), and is specifically composed of a single layer of SiO ₂ Yes.

  Further, as a feature of the second embodiment, the multi-wavelength reflection type diffraction grating 2 includes a first axial position adjustment layer 5 between the first reflection type diffraction grating 10A and the second reflection type diffraction grating 20A. A second axis position adjusting layer 7 is provided between the two-reflection diffraction grating 20A and the third reflection-type diffraction grating 30A.

  The first axis position adjustment layer 5 and the second axis position adjustment layer 7 are formed when the first light beam, the second light beam, and the third light beam are selectively incident on the reflection diffraction grating 2 for multiple wavelengths. This is useful when the positions of the axes are different (incident angles coincide with each other), and has the following functions.

  That is, the first axis position adjusting layer 5 causes the first reflection diffraction layer 12A to reflect and diffract the axis position when the second-order light beam reflected and diffracted by the second reflection diffraction layer 22A is emitted. The second axis position adjusting layer 7 is made to coincide with the position of the axis of the zeroth-order diffracted light of the first light beam, and the axis of the zeroth-order diffracted light of the third light beam reflected and diffracted by the third reflection diffraction layer 32A Each has a function of making the position coincide with the position of the axis of the 0th-order diffracted light of the second light beam reflected and diffracted by the second reflective diffraction layer 22A.

  Thereby, in the reflective diffraction grating 2 for multiple wavelengths according to the second embodiment, the positions of the axes at the time of incidence of the first light beam, the second light beam, and the third light beam that are selectively incident are different from each other. Even in this case, it is possible to make the positions of the axes of the 0th-order diffracted light beams of the respective light beams coincide with each other at the time of reflection diffraction.

The first axis position adjusting layer 5 and the second axis position adjusting layer 7 described above can be formed of a thin plate having a thickness of about 0.1 mm made of an optical glass material similar to the substrate 3A (3). These can also be constituted by a single layer of SiO ₂ . In the case of a single layer of SiO ₂ , the first axial position adjusting layer 5 is configured integrally with the first phase adjusting layer 13A, and the second axial position adjusting layer 7 is integrated with the second phase adjusting layer 23A. It is also possible to configure.

  Next, an embodiment of an optical pickup device according to the present invention will be described. FIG. 7 is a schematic configuration diagram of an optical pickup device according to an embodiment of the present invention.

The optical pickup device 50 shown in FIG. 7 includes an optical recording medium D ₁ (BD) for the first light beam, an optical recording medium D ₂ (DVD) for the second light beam, and light for the third light beam. Data reproduction of the recording medium D ₃ (CD) is performed, and by using the above-described reflection diffraction grating 2 for plural wavelengths, signal reading and tracking control are performed by the three-beam method corresponding to each light beam. It is configured as follows.

  The optical pickup device 50 includes a three-wavelength laser light source 51, a first prism 52 disposed on the optical path of each light beam from the three-wavelength laser light source 51, and a second prism joined to the first prism 52. 53, a pickup lens system 55 including a collimator 55a and an objective lens 55b, a three-wavelength hologram element 56, a three-wavelength light receiving device 57 for signal reading and tracking control, and outputs from the three-wavelength laser light source 51. And an APC light-receiving device 58 for control.

  The three-wavelength laser light source 51 is configured to selectively output the above-described first light beam, second light beam, and third light beam upward in the drawing. Although the axes of the light beams output from the three-wavelength laser light source 51 are parallel to each other, the positions of the light emission points of the light beams are different from each other. It is shifted little by little (for example, about 0.1 mm).

  A beam splitter film (hereinafter abbreviated as “BS film”) is provided on the joint surface 54 between the first prism 52 and the second prism 53. Further, the above-described reflection diffraction grating 2 for a plurality of wavelengths is installed on the second surface 52b of the first prism 52 arranged in parallel with the joint surface. The second surface 52b of the first prism 52 has an incident angle of each light beam selectively output from the three-wavelength laser light source 51 to the second surface 52b (the reflection diffraction grating 2 for multiple wavelengths). Is set to be a predetermined angle (for example, 23 °).

  Here, the reflection characteristic of the BS film will be described with reference to FIG. FIG. 6 is a diagram showing the reflection characteristics of the BS film. The reflection characteristics in FIG. 6 are for an incident angle of 23 degrees, the characteristics for S-polarized light are indicated by a solid line, and the characteristics for P-polarized light are indicated by a one-dot chain line.

  As shown in FIG. 6, the BS film reflects most of the wavelengths of light corresponding to the first light beam, the second light beam, and the third light beam, respectively, and the remaining portion. It is comprised so that it may permeate | transmit.

Hereinafter, the operation of the optical pickup device 50 will be described with reference to FIG.
When reproducing the optical recording medium D ₁ , the first light beam is output from the three-wavelength laser light source 51. The output first light beam is incident on the first prism 52 from the first surface 52a of the first prism 52, and is incident on the reflection diffraction grating 2 for multiple wavelengths provided on the second surface 52b.

  The first light beam incident on the multi-wavelength reflective diffraction grating 2 passes through the substrate 3A and enters the first reflective diffraction grating 10A, and is reflected and diffracted by the first reflective diffraction layer 12A (see FIG. 2). The beam is branched into three beams of a main beam composed of 0th order diffracted light and two sub beams composed of ± 1st order diffracted light (illustration of 3 beams is omitted in FIG. 7). Emitted.

  The first light beam emitted from the reflective diffraction grating 2 for multiple wavelengths is incident on the bonding surface 54, most of the BS film is reflected upward in the figure, and the remaining part is transmitted through the BS film. Then, the light enters the second prism 53. The first light beam incident on the second prism 53 is totally reflected by the first surface 53a of the second prism 53, is emitted from the second surface 53b, and enters the APC light receiving device 58. The light amount of the incident first light beam is detected by the APC light receiving device 58, and the output of the first light beam from the three-wavelength laser light source 51 is automatically adjusted based on the detected light amount.

Meanwhile, the first light beam from the BS film bonding surface 54 is reflected upward in the drawing is emitted from the third surface 52c of the first prism 52, via a pickup lens system 55 of the data recording the optical recording medium D ₁ The surface is condensed and irradiated in a 3-beam state. The irradiated first light beam is reflected on the data recording surface of the optical recording medium D ₁ , and at this time, the data information is carried and substantially retraces the original optical path and enters the second prism 53 again.

  A part of the first light beam that has entered the second prism 53 again passes through the BS film on the bonding surface 54 and is emitted downward from the first surface 53a of the second prism 53 in the drawing. The emitted first light beam is reflected leftward in the drawing by the three-wavelength hologram element 56 and enters the three-wavelength light receiving device 57 in a three-beam state.

The three-wavelength light receiving device 57 includes a detection unit for main beam detection and two detection units for sub-beam detection. Based on the detection of the main beam, data reproduction of the optical recording medium D ₁ is performed. tracking control based optical recording medium D ₁ in the detection and the like are performed in.

On the other hand, when reproducing the optical recording medium D ₂ , the second light beam is output from the three-wavelength laser light source 51. The output second light beam enters the first prism 52 from the first surface 52a of the first prism 52, and enters the reflection diffraction grating 2 for multiple wavelengths provided on the second surface 52b.

The second light beam incident on the multi-wavelength reflective diffraction grating 2 is transmitted through the substrate 3A, the first reflective diffraction grating 10A, and the first axis position adjusting layer 5, and is incident on the second reflective diffraction grating 20A. Reflected and diffracted by the second reflective diffraction layer 22A (see FIG. 2), the multi-wavelength reflective diffraction grating is branched into three beams of a main beam composed of zero-order diffracted light and two sub beams composed of ± first-order diffracted light. 2 is emitted. Incidentally, 0 position of the axis of the diffracted light of the second light beam that is allowed reflected and diffracted at the second reflective diffractive layer 22A is in case of reproducing the above-described optical recording medium D _1, the first reflection type diffraction grating 10A The position of the axis of the 0th-order diffracted light of the first light beam reflected and diffracted by the first reflective diffraction layer 12A coincides.

When reproducing the optical recording medium D ₃ , the third light beam is output from the three-wavelength laser light source 51. The output third light beam enters the first prism 52 from the first surface 52a of the first prism 52, and enters the multiple-wavelength reflective diffraction grating 2 installed on the second surface 52b.

The third light beam incident on the reflection diffraction grating for multiple wavelengths 2 is the substrate 3A, the first reflection diffraction grating 10A, the first axis position adjustment layer 5, the second reflection type diffraction grating 20A, and the second axis position adjustment layer. 7, enters the third reflective diffraction grating 30A, is reflected and diffracted by the third reflective diffraction layer 32A (see FIG. 2), and has two main beams consisting of a 0th-order diffracted light and a ± 1st-order diffracted light. Are emitted from the reflection diffraction grating 2 for multiple wavelengths. Incidentally, 0 position of the axis of the diffracted light of the third light beam that is allowed reflected and diffracted in the third reflective diffractive layer 32A is in case of reproducing the above-described optical recording medium D _2, the second reflection type diffraction grating 20A The position of the axis of the 0th-order diffracted light beam of the second light beam reflected and diffracted by the second reflective diffraction layer 22A coincides.

  The operations of the second light beam and the third light beam after being emitted from the multi-wavelength reflective diffraction grating 2 are the same as in the case of the first light beam. The three-wavelength light receiving device 57 includes a first light beam detector (for the main beam and two sub beams; the same applies hereinafter), a detector of the second light beam detector, and a third light beam. Are separately provided. The three-wavelength hologram element 56 is configured so that the reflection angle of each light beam can be adjusted so that each light beam directed to the three-wavelength light receiving device 57 is incident on each corresponding detection unit. Has been.

The optical pickup device 50 is configured such that the first to third light beams output from the wavelength laser light source 51 and incident on the first prism 52 via the multi-wavelength reflective diffraction grating 2 are S-polarized light. In addition, the first to third light beams that return from the optical recording media D ₁ , D ₂ , D ₃ to the second prism 53 via the pickup lens system 55 can be configured to be P-polarized light (for example, the first 2) A quarter-wave plate is disposed on the optical path between the prism 53 and the optical recording media D ₁ , D ₂ , D ₃ . In this case, as shown in FIG. 6, the BS film has a reflection characteristic that the S-polarized light is about 10% higher than the P-polarized light, so that P from the optical recording media D ₁ , D ₂ , D ₃ can be obtained. Since the return light composed of polarized light can be transmitted through the BS film more than in the case of composed of S-polarized light, it is possible to increase the utilization efficiency of light used for signal reading and tracking control.

  As mentioned above, although embodiment of this invention was described, this invention is not limited to the said embodiment, Aspects can be variously changed.

  For example, although the above-mentioned reflection diffraction gratings 1 and 2 for multiple wavelengths are for three wavelengths, the present invention can be configured for two wavelengths or for more than four wavelengths. is there.

  Further, it is possible to configure so as to correspond to each light beam other than the wavelength exemplified in the above embodiment, and it is possible to appropriately change the film configuration at that time.

  Moreover, in the said embodiment, although the 3rd reflection diffraction layers 22 and 22A are comprised from the 3rd dichroic film | membrane, this can also be comprised by a total reflection film.

  In the above embodiment, the optical pickup device 50 is used for data reproduction. However, the present invention can also be applied to an optical pickup device that performs data recording and both data recording and reproduction.

  Further, the reflection diffraction grating for multiple wavelengths according to the present invention can be applied to an optical apparatus other than the optical pickup device.

Sectional drawing which shows schematic structure of the reflection type diffraction grating for multiple wavelengths which concerns on 1st Embodiment Sectional drawing which shows schematic structure of the reflection type diffraction grating for multiple wavelengths which concerns on 2nd Embodiment The figure which shows the reflective characteristic of a 1st dichroic film | membrane The figure which shows the reflective characteristic of a 2nd dichroic film | membrane The figure which shows the reflective characteristic of a 3rd dichroic film | membrane The figure which shows the reflective characteristic of BS film 1 is a schematic configuration diagram of an optical pickup device according to an embodiment.

Explanation of symbols

1 Reflective diffraction grating for multiple wavelengths (first embodiment)
2 Reflective diffraction grating for multiple wavelengths (second embodiment)
3, 3A Substrate 5 First axis position adjustment layer 7 Second axis position adjustment layer 10, 10A First reflective diffraction grating 11, 11A First base layer 12, 12A First reflection diffraction layer 13, 13A First phase adjustment layer 20, 20A Second reflection type diffraction grating 21, 21A Second base layer 22, 22A Second reflection diffraction layer 23, 23A Second phase adjustment layer 30, 30A Third reflection type diffraction grating 31, 31A Third base layer 32, 32A Third reflective diffraction layer 51 Three-wavelength laser light source 52 First prism 52a First surface 52b (first prism) Second surface 52c (first prism) third surface 53 Second prism 53a First surface 53b (of the second prism) Second surface (of the second prism) 54 Joint surface 55 Pickup lens system 55a Collimator 55b Objective lens 56 Three-wavelength hologram Child 57 3-wavelength light-receiving unit 58 APC light-receiving device

Claims (6)

1st to N-th N light beams (N is an integer of 2 or more), which belong to different wavelength bands, are arranged on the optical path where the 1st to N-th light beams are selectively output. A reflection diffraction grating for multiple wavelengths,
N reflective diffraction gratings from 1 to N are stacked in this order from the incident side of the N light beams,
The jth reflection type diffraction grating (j is an arbitrary integer from 1 to N-1) is the jth light beam out of the jth light beam to the Nth light beam incident on the jth reflection type diffraction grating. A j-th reflection diffractive layer for reflecting and diffracting other light beams;
The Nth reflection type diffraction grating has an Nth reflection diffraction layer for reflecting and diffracting the Nth light beam incident on the Nth reflection type diffraction grating,
The jth reflection type diffraction grating adjusts the phase of the wavefront of at least the (j + 1) th light beam from the (j + 1) th light beam to the Nth light beam transmitted through the jth reflection type diffraction grating. A reflective diffraction grating for multiple wavelengths, comprising a phase adjustment layer. The j-th reflection diffraction layer reflects the j-th wavelength band light from the j-th wavelength band light to the N-th wavelength band light and transmits the other wavelength band light through the j-th dichroic film. Are arranged in a periodic uneven shape,
The Nth reflective diffractive layer is formed by periodically disposing an Nth dichroic film or a total reflection film having a characteristic of reflecting light in the Nth wavelength band. The reflective diffraction grating for multiple wavelengths according to claim 1.   The position of the axis of the 0th-order diffracted light beam of the (j + 1) th light beam reflected and diffracted by the (j + 1) th reflective diffraction layer between the jth reflective diffraction grating and the (j + 1) th reflective diffraction grating, 3. The j-th axis position adjustment layer is provided to match the position of the 0th-order diffracted light axis of the j-th light beam reflected and diffracted by the j-th reflection diffraction layer. The reflective diffraction grating for multiple wavelengths as described. A first light beam belonging to the first wavelength band, a second light beam belonging to a second wavelength band different from the first wavelength band, and a third wavelength band different from the first wavelength band and the second wavelength band The third light beam belonging to is a reflection diffraction grating for a plurality of wavelengths disposed on an optical path selectively output,
A first reflective diffraction grating, a second reflective diffraction grating, and a third reflective diffraction grating are stacked in this order from the incident side of the first light beam, the second light beam, and the third light beam,
The first reflection type diffraction grating reflects and diffracts the first light beam among the first light beam to the third light beam incident on the first reflection type diffraction grating and transmits the other light beam. A reflection diffraction layer, and a first phase adjustment layer for adjusting a phase of a wave front of at least the second light beam of the transmitted second light beam and the third light beam,
The second reflection type diffraction grating reflects and diffracts the second light beam of the second light beam and the third light beam incident on the second reflection type diffraction grating and transmits the third light beam. A second reflection diffraction layer and a second phase adjustment layer for adjusting the phase of the wavefront of the transmitted third light beam,
The third reflective diffraction grating has a third reflective diffraction layer that reflects and diffracts the third light beam incident on the third reflective diffraction grating,
The first reflective diffractive layer has a periodic concavo-convex shape on a first dichroic film having a characteristic of reflecting light in the first wavelength band and transmitting light in the second wavelength band and light in the third wavelength band. It is arranged in the
The second reflection diffraction layer is formed by arranging a second dichroic film having a characteristic of reflecting the light of the second wavelength band and transmitting the light of the third wavelength band in a periodic uneven shape. Yes,
The third reflective diffractive layer is formed by arranging a third dichroic film or a total reflection film having a characteristic of reflecting the light in the third wavelength band in a periodic uneven shape. Reflective diffraction grating for multiple wavelengths. The position of the axis of the 0th-order diffracted light beam of the second light beam reflected and diffracted by the second reflective diffraction layer between the first reflective diffraction grating and the second reflective diffraction grating is defined as the first reflective diffraction grating. A first axis position adjusting layer is provided to match the position of the axis of the 0th-order diffracted light of the first light beam reflected and diffracted by the reflection diffraction layer;
The position of the axis of the 0th-order diffracted light beam of the third light beam reflected and diffracted by the third reflective diffraction layer between the second reflective diffraction grating and the third reflective diffraction grating is defined as the second reflective diffraction grating. 5. The multi-wavelength reflection layer according to claim 4, further comprising a second-axis position adjusting layer that matches an axis position of the zero-order diffracted light of the second light beam reflected and diffracted by the reflection diffraction layer. Type diffraction grating. An optical pickup device comprising the reflection diffraction grating for multiple wavelengths according to any one of claims 1 to 5.

Images