JP2007128570A - Optical pickup device - Google Patents

Abstract

To provide an optical pickup device that does not require complicated components, has a small number of components, and can be configured in a small size and at low cost.
First and second beam splitter surfaces 7 and 8 for branching light beams 31 and 32 having first and second wavelengths modulated by a recording medium are provided on an optical path 40 in parallel with each other. The distance t between them is set so as to eliminate the deviation of the optical axes 41 and 42. The first light receiving element 10 detects in common the high-frequency signal component and the tracking signal component of the branched light beams 31b and 32b. The hologram element 5 diffracts the returned light beams 31 and 32 so as to eliminate the deviation of the optical axes 41 and 42, respectively. The second light receiving element 2 detects the focus error signal component of each diffracted light beam 31c, 32c in common.
[Selection] Figure 1A

Description

  The present invention relates to an optical pickup device, and more specifically, includes a plurality of light sources having different wavelengths according to the type of recording density standard of the recording medium, and irradiates the recording medium with a light beam from the light source. The present invention relates to an optical pickup device that detects reflected light of a light beam with a light receiving element.

CD (compact disc), DVD (digital universal disc), and the like are widely used as optical discs that optically read signals using a light beam such as a laser beam. In order to perform recording and signal reading of a plurality of types of optical disks having different recording density standards, an optical pickup device as shown in FIGS. 9A and 9B is known (FIG. 9A is viewed from above, FIG. 9B shows a side view.) This optical pickup apparatus includes a plurality of laser diodes 103 and 104 having different wavelengths according to the types of DVD and CD recording density standards. Then, the optical beam (DVD or CD) 114 is irradiated substantially vertically through the laser diode 103 or 104 through the beam splitter 109, the collimating lens 111, the rising mirror 112, and the objective lens 113 in this order. The reflected light modulated by the optical disk 114 passes through the objective lens 113, the rising mirror 112, and the collimator lens 111 in the reverse direction, and then is branched from the optical path 140 by the beam splitter 109. Next, each branched light beam is passed through the coaxial element 106 to eliminate the deviation of the optical axes 141 and 142 according to the distance C between the light emitting point of the laser diode 103 and the light emitting point of the laser diode 104. , And is detected by the light receiving element 10.
JP 2003-091856 A JP-A-10-143908

  However, in the above-described conventional optical pickup device, the coaxial element 6 is specifically a diffractive element having a complicated step-like diffraction grating formed on one side. Further, it is necessary to devise the pattern shape of the light receiving surface of the light receiving element 10. For this reason, the optical pickup device of the above-described conventional example is difficult to realize and has a problem of high cost as a whole.

  SUMMARY OF THE INVENTION An object of the present invention is to provide an optical pickup device that does not require complicated components, has a small number of components, and can be configured at a low cost.

In order to solve the above problems, an optical pickup device of the present invention is
A light source group that emits light beams with different wavelengths to the optical path is provided, and the recording medium is irradiated with a light beam from one of the light sources selected according to the recording density of the recording medium, and the reflection modulated by the recording medium An optical pickup device for reading a signal by branching light from the optical path,
The light source group includes a first light source and a second light source that are arranged in a direction substantially perpendicular to the optical path and emit light beams having a first wavelength and a second wavelength, respectively.
A first beam splitter surface for branching the light beam of the first wavelength modulated by the recording medium and a second beam splitter surface for branching the light beam of the second wavelength modulated by the recording medium on the optical path. In parallel with each other, and the first beam splitter surface and the second beam so as to eliminate the deviation of the optical axis of each branched light beam caused by the distance between the first light source and the second light source. The distance to the splitter surface is set,
A first light receiving element for commonly detecting a high-frequency signal component and a tracking signal component of each of the light beams branched on the first or second beam splitter surface;
The light beams of the first wavelength and the second wavelength transmitted through the first and second beam splitter surfaces and returned on the optical path between the light source group and the group formed by the first and second beam splitter surfaces. Including a hologram element that diffracts so as to eliminate the deviation of the optical axis due to the distance between the first light source and the second light source,
A second light receiving element for commonly detecting a focus error signal component of each of the light beams diffracted by the hologram element is provided.

  Here, the “distance between the first light source and the second light source” means the distance between the light emitting point of the first light source and the light emitting point of the second light source.

  In the optical pickup device of the present invention, the first beam splitter surface and the second light beam are arranged so as to eliminate the deviation of the optical axis of each branched light beam caused by the distance between the first light source and the second light source. A distance from the beam splitter surface is set. Therefore, it is not necessary to use complicated components such as the coaxial element in the conventional example. The first light receiving element substantially converts the high-frequency signal component and tracking signal component of each light beam branched by the first or second beam splitter surface on the light receiving surface with respect to each light beam. Can be detected in common at the same point. Further, the first and second wavelength light beams that have passed through the first and second beam splitter surfaces are returned to the optical axis due to the distance between the first light source and the second light source. The second light receiving element shares the focus error signal component of each light beam diffracted by the hologram element at substantially the same point on the light receiving surface. (This is desirable because it enables focus error detection by the knife edge method). Thus, this optical pickup device does not require complicated components and the number of components can be reduced. Therefore, it is small and configured at low cost.

  In the optical pickup device of one embodiment, the first beam splitter surface and the second beam splitter surface are integrally included in the same optical component.

  In the optical pickup device of this embodiment, the first beam splitter surface and the second beam splitter surface are integrally included in the same optical component. Therefore, the number of parts can be further reduced.

  In an optical pickup device according to an embodiment, the first and second beam splitter surfaces and the hologram element are integrally fixed.

  The optical pickup device according to this embodiment is further reduced in size. Also, once assembled, the relative position between the first and second beam splitter surfaces and the hologram element does not fluctuate, so that reliability is improved and performance is enhanced.

  Furthermore, if the light source group and the first and second light receiving elements are integrated into a unit with respect to the first and second beam splitter surfaces and the hologram element, further miniaturization and higher reliability can be achieved. And improved performance.

  In the optical pickup device according to the embodiment, the second light receiving element may cause the focus error signal component of each light beam diffracted by the hologram element to be substantially the same on the light receiving surface with respect to each light beam. It is characterized by detecting.

  In the optical pickup device of this embodiment, it is possible to detect a focus error by the knife edge method. As a result, when reading a DVD-RAM (Digital Versatile Disk Random Access Memory; DVD that can be read and written / erased) or the like, leakage of the track cross signal into the focus error signal can be minimized. Therefore, the performance is further improved.

  In the optical pickup device of one embodiment, the second light receiving element is located outside the first light source and the second light source in the direction substantially perpendicular to the optical path, and has the first wavelength and the first wavelength. It is arranged on the side of a light source that emits a light beam having a shorter wavelength of the two wavelengths.

In general, a hologram element has a pitch of hologram formed on the element surface as d, and a wavelength of light incident perpendicularly to the element surface as λ,
sinθ = λ / d
The light is diffracted at an angle θ represented by Here, in the optical pickup device according to the one embodiment, the second light receiving element is outside the first light source and the second light source in a direction substantially perpendicular to the optical path, and the first light source. It arrange | positions at the side of the light source which radiate | emits the light beam of short wavelength among 1 wavelength and 2nd wavelength. Therefore, when the hologram element diffracts the light beams having the first wavelength and the second wavelength that have passed through the first and second beam splitter surfaces and returned, the hologram element is interposed between the first light source and the second light source. The diffraction can be performed so as to eliminate the optical axis shift caused by the distance.

In the optical pickup device of one embodiment,
The first and second beam splitter surfaces and the first light receiving element are abolished,
The second light receiving element detects in common a high frequency signal component and a tracking signal component in addition to the focus error signal component of each light beam diffracted by the hologram element.

  In the optical pickup device of this embodiment, the number of parts can be further reduced. Therefore, it is further reduced in size and cost.

  In the optical pickup device of one embodiment, the second light receiving element is configured so that the focus error signal component, the high frequency signal component, and the tracking signal component of each light beam are substantially the same on the light receiving surface with respect to each beam. It is characterized by detecting.

  In the optical pickup device according to this embodiment, further downsizing and high performance can be achieved.

  In the optical pickup device of one embodiment, the second light receiving element is located outside the first light source and the second light source in the direction substantially perpendicular to the optical path, and has the first wavelength and the first wavelength. It is arranged on the side of a light source that emits a light beam having a shorter wavelength of the two wavelengths.

  In the optical pickup device according to this embodiment, the hologram element diffracts the light beams of the first wavelength and the second wavelength transmitted through the first and second beam splitter surfaces and returns the first light source. Can be diffracted so as to eliminate the deviation of the optical axis due to the distance between the light source and the second light source.

  In the optical pickup device of one embodiment, the hologram element is divided into three or more regions corresponding to the focus error signal component, the high frequency signal component, and the tracking signal component of each light beam. Pickup device.

  In the optical pickup device of this embodiment, the hologram element is configured to generate the focus error signal when diffracting the light beams of the first wavelength and the second wavelength that have passed through the first and second beam splitter surfaces and returned. Each of the component, the high-frequency signal component, and the tracking signal component can be diffracted so as to eliminate the deviation of the optical axis due to the distance between the first light source and the second light source.

  In one embodiment, the second light receiving element has a pair of light receiving regions so as to generate the focus error signal by a single knife edge method.

  In the optical pickup device of this embodiment, adjustment when generating the focus error signal is facilitated, and high reliability can be achieved.

  In one embodiment, the second light receiving element has two pairs of light receiving regions so as to generate the focus error signal by a double knife edge method.

  In the optical pickup device of this embodiment, the S / N ratio (signal-to-noise ratio) of the focus error signal is increased, and high reliability can be achieved.

  An optical pickup device according to an embodiment is characterized in that a hologram for diffracting each light beam of the hologram element is produced at a substantially intermediate wavelength between the first wavelength and the second wavelength.

  In the optical pickup device of this embodiment, the second light receiving element can accurately detect the focus error signal component of each light beam diffracted by the hologram element at the same point on the light receiving surface.

In the optical pickup device of one embodiment,
The light source group includes a third light source arranged side by side with the first light source and the second light source in a direction substantially perpendicular to the optical path, and emitting a light beam having a third wavelength,
A third beam splitter surface for branching the light beam of the third wavelength modulated by the recording medium in parallel with the first and second beam splitter surfaces on the optical path; The distance between each beam splitter surface is set so as to eliminate the deviation of the optical axis of each branched light beam caused by the above,
The first light receiving element commonly detects a high-frequency signal component and a tracking signal component of each of the light beams branched by the first, second, or third beam splitter surface;
The hologram element is provided on an optical path between the light source group and a group formed by the first, second, and third beam splitter surfaces, and the light of each wavelength transmitted through the beam splitter surfaces and returned. The beam is diffracted so as to eliminate the deviation of the optical axis due to the distance between the light sources,
The second light receiving element detects a focus error signal component of each of the light beams diffracted by the hologram element in common.

  In the optical pickup device of this embodiment, recording and signal reading of three types of recording media having different recording density standards, such as CD, DVD, and BD (Blu-ray disc), are possible. In addition, this optical pickup device does not require complicated components and requires a small number of components. Therefore, it is small and configured at low cost.

  Hereinafter, an optical pickup device of the present invention will be described in detail with reference to embodiments shown in the drawings.

(First embodiment)
FIG. 1A shows a configuration of an optical pickup device according to an embodiment as viewed from above. This optical pickup device generally includes a semiconductor laser unit 50 having a substantially L-shaped frame 15, a collimating lens 11, a rising mirror 12, and an objective lens 13 (see FIG. 2B) along an optical path 40. In order. FIG. 2B also shows an optical disk (CD, DVD, etc.) 14 as a recording medium.

  A semiconductor laser unit 50 shown in FIG. 1A includes a first semiconductor laser chip 4 as a first light source that emits a laser beam 31 having a first wavelength (780 nm in this example) to an optical path 40, and a second wavelength (in this example). A second semiconductor laser chip 3 as a second light source that emits a laser beam 32 of 650 nm) to the optical path 40, a first photodiode chip 10 as a first light receiving element, and a second photodiode chip as a second light receiving element. 2, a hologram element 5, and a beam splitter component 9.

  The first semiconductor laser chip 4, the second semiconductor laser chip 3, the first photodiode chip 10, the second photodiode chip 2, and the hologram element 5 are integrally attached to the frame 15. Further, the beam splitter component 9 is integrally fixed to the hologram element 5. Thereby, the semiconductor laser unit 50 is integrated.

  A laser beam 31 having a wavelength of 780 nm emitted from the first semiconductor laser chip 4 is used for recording and signal reading on a CD having a normal recording density, and has a wavelength of 650 nm emitted from the second semiconductor laser chip 3. The laser beam 32 is used to perform recording and signal reading on a DVD having a high recording density. The first semiconductor laser chip 4 or the second semiconductor laser chip 3 is selected according to the recording density standard of the recording medium 14 by a control means (not shown) provided outside the optical pickup device.

  FIG. 2A shows a mode in which the second semiconductor laser chip 3 is selected in FIG. 1A and a laser beam 32 (shown by a solid line) is emitted only from the second semiconductor laser chip 3. FIG. 2B schematically shows the side of FIG. 2A viewed from the side. 2B, the laser beam 32 emitted from the second semiconductor laser chip 3 passes through the hologram element 5, the beam splitter component 9, the collimating lens 11, the rising mirror 12, and the objective lens 13 in this order, and the optical disk 14 Is irradiated. The laser beam (reflected light) 32 modulated by the optical disk 14 passes through the objective lens 13, the raising mirror 12, and the collimator lens 11, and then is branched from the optical path 40 by the beam splitter component 9 as shown in FIG. 2A. (The branched laser beam is indicated by reference numeral 32b) and enters the first photodiode chip 10. Further, the laser beam 32 that has passed through the beam splitter component 9 is diffracted by the hologram element 5 (the diffracted laser beam is indicated by reference numeral 32 c) and is incident on the second photodiode chip 2.

  FIG. 3A schematically shows a mode in which the first semiconductor laser chip 4 is selected in FIG. 1A and a laser beam 31 (shown by a broken line) is emitted only from the first semiconductor laser chip 4. FIG. 3B schematically shows the side of FIG. 3A viewed from the side. 3B, the laser beam 31 emitted from the first semiconductor laser chip 4 passes through the hologram element 5, the beam splitter component 9, the collimator lens 11, the rising mirror 12, and the objective lens 13 in this order, and the optical disk 14 Is irradiated. The laser beam (reflected light) 31 modulated by the optical disk 14 passes through the objective lens 13, the rising mirror 12, and the collimating lens 11, and then is branched from the optical path 40 by the beam splitter component 9 as shown in FIG. 3A. (The branched laser beam is indicated by reference numeral 31b) and enters the first photodiode chip 10. Further, the laser beam 31 transmitted through the beam splitter component 9 is diffracted by the hologram element 5 (the diffracted laser beam is indicated by reference numeral 31c) and enters the second photodiode chip 2.

  The beam splitter component 9 is an optical component including a first beam splitter surface 7 and a second beam splitter surface 8 that are parallel to each other. In this example, the first beam splitter surface 7 is composed of a dichroic filter, and is a half mirror that half-reflects and transmits half the laser beam having the first wavelength of 780 nm (note that the wavelength is substantially different from the first wavelength). The laser beam is almost completely transmitted.) The second beam splitter surface 8 is formed of a dichroic filter, and is a half mirror that half-reflects and transmits half the laser beam having the second wavelength of 650 nm (note that a laser beam having a wavelength substantially different from the second wavelength is Almost all is transmitted.) Such a beam splitter component 9 is produced, for example, by sandwiching a flat plate with dichroic filters formed on both sides between two other flat plates and cutting them parallel to the plate surface at an angle of 45 °. The In this way, by including the two beam splitter surfaces 7 and 8 in the beam splitter component 9, the number of components can be reduced.

  The first beam splitter surface 7 and the second beam splitter surface 8 are arranged in parallel to each other at an angle of 45 ° with respect to the optical axes 41 and 42 of the first and second semiconductor laser chips 4 and 3. The reflected lights 31 and 32 modulated by the recording medium 14 are branched toward the first photodiode chip 10 at the first beam splitter surface 7 and the second beam splitter surface 8, respectively.

Here, the distance t between the first beam splitter surface 7 and the second beam splitter surface 8 is the distance C between the light emitting point of the first semiconductor laser chip 4 and the light emitting point of the second semiconductor laser chip 3. It is set so as to eliminate the deviation of the optical axes 41b and 42b of the branched laser beams 31b and 32b. That is,
C = 2 ^1/2 t
The relationship is satisfied. As a result, the optical axes 41 b and 42 b of the branched laser beams 31 b and 32 b coincide with each other, and these laser beams 31 b and 32 b are incident substantially perpendicular to the light receiving surface of the first photodiode chip 10. Therefore, it is not necessary to use complicated components such as the coaxial element in the conventional example.

  The first photodiode chip 10 is attached to the frame 15 such that the light receiving surface faces the optical axes 41b and 42b of the laser beams 31b and 32b perpendicularly.

  In this example, the first photodiode chip 10 has a known pattern layout as shown in FIG. 1C. That is, the light receiving surface has four divided light receiving areas 10a, 10b, 10c, 10d at the center of the light receiving surface, and two divided light receiving areas 10e, 10e; 10f, 10f on both sides thereof. The laser beams 31b and 32b are three beams MB in a direction perpendicular to the paper surface of FIG. 1A by a diffraction grating (not shown) (for example, provided on the first and second semiconductor laser chips 4 and 3 side surfaces of the hologram element 5). It is divided into SB + and SB−. A radio frequency (RF) signal component and a main beam push-pull signal MPP are detected by the four-divided light receiving regions 10a, 10b, 10c, and 10d that receive the central main beam (0th order beam) MB. Further, the sub beam push-pull signal SPP is detected by the two divided light receiving areas 10e, 10e; 10f, 10f receiving the sub beams (± primary beams) SB +, SB− on both sides. The tracking error signal TES is detected by a known DPP method (Differential Push-Pull Method) using the main beam push-pull signal MPP and the sub-beam push-pull signal SPP. In this way, the first photodiode chip 10 commonly detects the high-frequency signal component and the tracking signal component of each of the laser beams 31b and 32b branched by the first beam splitter surface 7 or the second beam splitter surface 8. . Thus, the first photodiode chip 10 can commonly detect the high-frequency signal component and the tracking signal component of the laser beams 31b and 32b at substantially the same point on the light receiving surface with respect to the laser beams 31b and 32b, respectively.

  The first photodiode chip 10 has a focus error detection function of the astigmatism method and the differential astigmatism method in which leakage of the track cross signal into the focus by a disk such as a DVD-RAM becomes a problem. It is not installed.

  As shown in FIG. 1A, the hologram element 5 has a diffraction grating 1 made of a hologram on the surface on the beam splitter component 9 side. The hologram element 5 uses the diffraction grating 1 to convert the laser beam 31 having the first wavelength of 780 nm and the laser beam 32 having the second wavelength of 650 nm, which have passed through the beam splitter component 9, to the light emitting point of the first semiconductor laser chip 4 and (2) Diffraction is performed so as to eliminate the deviation of the optical axes 41c and 42c caused by the distance C between the light emitting point of the semiconductor laser chip 3 Next, this point will be specifically described.

In general, in a hologram element, when the pitch of the diffraction grating formed on the element surface is d and the wavelength of light incident perpendicularly to the element surface is λ,
sinθ = λ / d
The light is diffracted at an angle θ represented by Therefore, as shown in FIG. 1B, the angle R at which the laser beam 31 having a long wavelength is diffracted is larger than the angle Q at which the laser beam 32 having a short wavelength is diffracted. Here, in this optical pickup device, the second photodiode chip 2 has the first semiconductor laser chip 4 and the second semiconductor laser chip 3 in the direction substantially vertical to the optical path 40 (the vertical direction in FIG. 1B). And on the side of the second semiconductor laser chip 3 that emits a laser beam 32 having a shorter wavelength (650 nm) of the first wavelength and the second wavelength (lower side in FIG. 1B). More specifically, in this example, the distance in the direction along the optical axes 41 and 42 between the diffraction grating 1 and the second photodiode chip 2 is L, and the first semiconductor laser chip 4 and the second photodiode chip. 2 is the distance in the direction perpendicular to the optical axes 41 and 42 between the second semiconductor laser chip 3 and the second photodiode chip 2 is the distance in the direction perpendicular to the optical axes 41 and 42 B ( = AC)
LsinR = A
LsinQ = B
The relationship is satisfied at the same time. Accordingly, when the hologram element 5 diffracts the returned first and second wavelength laser beams 31 and 32 that have passed through the beam splitter component 9, the light emitting point of the first semiconductor laser chip 4 and the second semiconductor laser chip 3 are diffracted. The light can be diffracted so as to eliminate the deviation of the optical axes 41c and 42c due to the distance C from the light emitting point.

  In FIG. 1A, the distance between the centers of the optical axes 41 and 42 and the light receiving region of the second photodiode chip 2 is represented by D.

  The laser beams 31 c and 32 c diffracted by the hologram element 5 enter the light receiving surface of the second photodiode chip 2. A focus error signal is detected by a known hologram Foucault method using the second photodiode chip 2.

  Specifically, as shown in FIG. 1D, the pattern of the diffraction grating 1 of the hologram element 5 has two semicircular regions 1a and 1b. In these regions 1a and 1b, the extending directions of the gratings are slightly different from each other, whereby the laser beams 31c and 32c are bifurcated and diffracted. When a focus error signal is detected by the hologram Foucault method, as shown in FIG. 1D, two sets of laser beams 31c and 32c diffracted by the regions 1a and 1b of the diffraction grating 1 are formed on the second photodiode chip 2. Each of the two light receiving areas 2e, 2f; 2g, 2h may be detected by the double knife edge method, or may be diffracted by the areas 1a, 1b of the diffraction grating 1, as shown in FIG. 1E. The laser beams 31c and 32c may be detected by a single knife edge method in a set of two negatively divided light receiving areas 2e and 2f on the second photodiode chip 2. According to the double knife edge method, the signal output is doubled and the S / N ratio is improved, but accuracy is required for adjustment. On the other hand, according to the single knife edge method, the S / N ratio is not improved, but the adjustment becomes simple. Whether the double knife edge method or the single knife edge method is used can be selected by a system using the optical pickup device.

  Note that FIG. 2C shows that, when the double knife edge method is used corresponding to FIG. 1D, the laser beam 32c having the second wavelength (650 nm) diffracted by each region 1a, 1b of the diffraction grating 1 is the second photodiode chip. 2 shows a state in which the light is incident on two sets of light receiving areas 2e, 2f; 2g, 2h. Further, FIG. 3C shows that when the double knife edge method is used corresponding to FIG. 1D, the laser beam 31c having the first wavelength (780 nm) diffracted by each region 1a, 1b of the diffraction grating 1 is the second photodiode chip. 2 shows a state in which the light is incident on two sets of light receiving areas 2e, 2f; 2g, 2h.

  Thus, by detecting the focus error signal by the knife edge method, the leakage of the track cross signal into the focus error signal can be minimized when reading a DVD-RAM or the like. Therefore, the performance of the optical pickup device is improved.

  As can be seen from FIG. 1D and FIG. 1E, the second photodiode chip 2 has the focus error signal components of the laser beams 31c and 32c diffracted by the hologram element 5 on the light receiving surface with respect to the laser beams 31c and 32c, respectively. It can be detected at substantially the same point.

  Thus, this optical pickup device does not require complicated components and the number of components can be reduced. Therefore, it is small and configured at low cost. In particular, since the semiconductor laser unit 50 including the beam splitter component 9 and the hologram element 5 is integrated, the optical pickup device is further reduced in size. Further, once assembled, the relative position between the first and second beam splitter surfaces 7 and 8 and the hologram element 5 does not fluctuate, so that the reliability is increased and the performance is improved.

  In this embodiment, the first beam splitter surface 7 and the second beam splitter surface 8 are half mirrors made of dichroic filters. However, the present invention is not limited to this, and the P wave (parallel to the normal line of the reflecting surface) is used. (Polarization component) and S wave (polarization component perpendicular to the normal line of the reflecting surface) may be selected and transmitted and reflected by PBS (Polarizing Beam Splitter).

(Second Embodiment)
FIG. 4A shows a configuration of an optical pickup device according to another embodiment as viewed from above. This optical pickup device includes a semiconductor laser unit 51 having a roughly rectangular parallelepiped frame 15A, a collimating lens 11, a rising mirror 12, and an objective lens 13 (see FIG. 2B) along an optical path 40. In order. In addition, the same code | symbol is attached | subjected to the same component as the component in FIG. 1A, and each description is abbreviate | omitted.

  This optical pickup device is largely different from that shown in FIG. 1A in that the beam splitter component 9 and the first photodiode chip 10 are eliminated.

  As shown in FIG. 4C, the diffraction grating 1A of the hologram element 5A is divided into a semicircular area 1a and quarter-shaped areas 1c and 1d. In these regions 1a, 1c, and 1d, the extending directions of the gratings are slightly different from each other, whereby the laser beams 31 and 32 are diffracted by being branched into three. In FIG. 4C, the laser beams diffracted in the regions 1a, 1c, and 1d are represented by reference numerals 31c1, 31c2, and 31c3; 32c1, 32c2, and 32c3, respectively.

As can be seen from FIG. 4A, the second photodiode chip 2A is similar to the example of FIG. 1A with respect to the first semiconductor laser chip 4, with respect to a direction substantially perpendicular to the optical path 40 (longitudinal direction in FIG. 4B). Outside the array of the second semiconductor laser chips 3 and on the side of the second semiconductor laser chip 3 that emits a laser beam 32 having a shorter wavelength (650 nm) of the first wavelength and the second wavelength (lower side in FIG. 4B). Has been placed. More specifically, as shown in FIG. 4B, the distance in the direction along the optical axes 41 and 42 between the diffraction grating 1A and the second photodiode chip 2 is L, and the first semiconductor laser chip 4 and the second semiconductor laser chip 4 are The distance in the direction perpendicular to the optical axes 41 and 42 between the photodiode chip 2 is A, and the distance in the direction perpendicular to the optical axes 41 and 42 between the second semiconductor laser chip 3 and the second photodiode chip 2. Is B (= A−C),
LsinR = A
LsinQ = B
The relationship is satisfied at the same time. Accordingly, when the hologram element 5A diffracts the laser beams 31 and 32 having the first wavelength and the second wavelength, the distance C between the light emitting point of the first semiconductor laser chip 4 and the light emitting point of the second semiconductor laser chip 3 is determined. Can be diffracted so as to eliminate the deviation of the optical axes 41c and 42c due to the above.

  As shown in FIG. 4C, the pattern of the second photodiode chip 2A is configured to correspond to the three regions 1a, 1c, and 1d of the diffraction grating 1A of the hologram element 5A. That is, the second photodiode chip 2A has a pair of two divided regions 2a and 2b that commonly receive the laser beams 31c1 and 32c1 diffracted by the region 1a of the diffraction grating 1A at the center, and on both sides thereof. The region 2c commonly receives the laser beams 31c2 and 32c2 diffracted by the region 1c of the diffraction grating 1A, and the region 2d commonly receives the laser beams 31c3 and 32c3 diffracted by the region 1d of the folded grating 1A.

  A focus error signal is detected using the light receiving regions 2a and 2b of the second photodiode chip 2A by the single knife edge method using the semicircular region 1a of the diffraction grating 1A shown in FIG. 4C. According to the single knife edge method, when a DVD-RAM or the like is read, the track cross signal does not leak into the focus error. Therefore, a good focus error signal can be obtained. Further, by receiving light in the light receiving regions 2c and 2d corresponding to the other regions 1c and 1d of the diffraction grating 1A, a high frequency signal component and a tracking error signal component are detected. As in the previous example, the tracking error signal TES detects not only the main beam push-pull signal MPP but also the sub-beam push-pull signal SPP using the pattern of the light receiving region of the second photodiode chip 2A. It is obtained by applying a DPP method (Differential Push-Pull Method).

  As described above, the second photodiode chip 2A commonly detects the focus error signal component, the high-frequency signal component, and the tracking signal component of each laser beam 31 and 32 at substantially the same point on the light receiving surface with respect to each beam. be able to.

  Further, in this optical pickup device, the number of components can be reduced because the beam splitter component 9 and the first photodiode chip 10 are eliminated as compared with the optical pickup device shown in FIG. 1A. Therefore, further downsizing and cost reduction are possible.

  Furthermore, by increasing the number of divisions of the diffraction grating 1A of the hologram element 5A, it is possible to improve the playability (reproduction capability) for various optical disks.

  Next, with reference to FIG. 5 and FIGS. 6A to 6D, a method of manufacturing a diffraction grating (represented by reference numeral 1B) made of a hologram suitable for the above-described hologram elements 5 and 5A will be described. As shown in FIG. 5, generally, the pattern of the hologram 93 includes a reference wave light source position 91 corresponding to the position of the light emitting point of the semiconductor laser chip and a recording light source position corresponding to the position of the light receiving spot on the light receiving element. 92 and the position of the substrate surface 90 on which the hologram 93 is formed.

  FIG. 6A shows a case where a hologram diffraction grating 1B is designed with a substantially intermediate wavelength λm between the first wavelength 780 nm and the second wavelength 650 nm, and reproduction is performed with the same wavelength (λm) as the designed wavelength λm. (Equivalent to the above-mentioned second photodiode chips 2 and 2A, represented here by reference numeral 2B) The pattern and position of the light receiving spot 35 incident thereon are schematically shown. In this case, the light receiving spot 39 is condensed with almost no aberration.

  FIG. 6B shows a case where the hologram diffraction grating 1B is designed with a substantially intermediate wavelength λm between the first wavelength 780 nm and the second wavelength 650 nm as in the above case, and a wavelength shorter than the design wavelength λm (in this example, the second wavelength). FIG. 6B schematically shows the pattern and position of the light receiving spot 36 incident on the light receiving element 2B when reproduction is performed at 650 nm (denoted by reference numeral λ2 in FIG. 6B). The spot 36 obtained in this case is slightly defocused with respect to the original non-aberration spot 35. The position of the spot 36 is slightly shifted from the original position of the aberration-free spot 35 to the side closer to the diffraction grating 1B.

  In FIG. 6C, similarly to the above case, the hologram diffraction grating 1B is designed with a wavelength λm substantially intermediate between the first wavelength 780 nm and the second wavelength 650 nm, and a wavelength longer than the design wavelength λm (in this example, the first wavelength 780 nm (represented by the symbol λ1 in FIG. 6C), the pattern and position of the light receiving spot 37 incident on the light receiving element 2B are schematically shown. The spot 37 obtained in this case is slightly defocused from the original non-aberration spot 35. The position of the spot 37 is slightly shifted from the position of the original non-aberration spot 35 to the side far from the diffraction grating 1B.

  Both spots 36 and 37 in FIG. 6B and FIG. 6C are of a practical level, and the design angle of the dividing line of the light receiving region on the light receiving element 2B can be optimally designed for both wavelengths λ1 and λ2. In this case, there is no problem in detection accuracy.

  FIG. 6D shows a light receiving spot obtained when the hologram diffraction grating 1B is designed with a substantially intermediate wavelength λm between the first wavelength 780 nm and the second wavelength 650 nm, and reproduction is performed with a wavelength λ2 shorter than the designed wavelength λm. The positions of the light emitting points in the above two cases are designed positions (in this example, diffraction) so that the position of 36A and the position of the light receiving spot 37A obtained when reproduction is performed at a wavelength λ1 longer than the design wavelength λm. The mode shifted from the center of the pattern of the grating 1B is shown. In this case, the light receiving spots 36A and 37A obtained in the above two cases are slightly defocused with respect to the original non-aberration spot 35, respectively. The positions of the spots 36A and 37A overlap each other. Both spots 36 and 37 are of a level that can withstand practical use, and there is no problem in detection accuracy. Moreover, by overlapping the positions of the spots 36A and 37A in this way, the area of the light receiving element 2B can be minimized.

  FIG. 6E shows the arrangement of the hologram diffraction grating 1B and the light receiving element 2B from the viewpoint corresponding to FIG. 1A.

  As is apparent from the above, this optical pickup device does not require such complicated components, and can be configured with a small number of components and a low cost.

(Third embodiment)
FIG. 7A shows a configuration of an optical pickup device of still another embodiment as viewed from above. This optical pickup device roughly includes a semiconductor laser unit 52 having a substantially L-shaped frame 15, a collimating lens 11, a rising mirror 12, and an objective lens 13 (see FIG. 2B) along an optical path 40. In order. In addition, the same code | symbol is attached | subjected to the same component as the component in FIG. 1A, and each description is abbreviate | omitted.

  In this optical pickup device, a third light source as a third light source that emits a laser beam 33 of a third wavelength (in this example, 405 nm) for performing recording and signal reading of a BD (Blu-ray disc) with respect to that of FIG. 1A. 3 is greatly different in that it includes a semiconductor laser chip 22. In this example, the third semiconductor laser chip 22 is arranged in place of the second semiconductor laser chip 3 in FIG. 1A. The second semiconductor laser chip 3 is disposed between the first semiconductor laser chip 4 and the third semiconductor laser chip 22.

  Accordingly, the beam splitter component 9C is composed of a dichroic filter in addition to the first beam splitter surface 7 and the second beam splitter surface 8, and is a half mirror that half-reflects and transmits half the laser beam having the third wavelength of 650 nm. (The laser beam having a wavelength substantially different from the third wavelength is transmitted almost entirely).

  Here, the distance t1 between the first beam splitter surface 7 and the second beam splitter surface 8 and the distance t2 between the second beam splitter surface 8 and the third beam splitter surface 21 are determined by each semiconductor laser chip 4, The optical axis 41b, 42b, 43b (see FIG. 7B) of each branched laser beam 31b, 32b, 33b caused by the distance between the light emitting points 3, 22 is set to eliminate the deviation.

More specifically, in FIG. 7B,
LsinR = A
LsinP = D
LsinQ = B
The relationship is satisfied at the same time.

  The first photodiode chip 10C commonly detects the high-frequency signal component and the tracking signal component of each of the laser beams 31b, 32b, and 33b branched by the first, second, or third beam splitter surfaces 7, 8, and 21. It has become.

  The hologram element 5C has the laser beams 31, 32, 32 b of each wavelength so as to eliminate the deviation of the optical axes 41 c, 42 c, 43 c (see FIG. 7B) according to the distance between the emission points of the laser beams 31 b, 32 b, 33 b. 33 is diffracted.

  Further, the second photodiode chip 2C is configured to commonly detect focus error signal components of the laser beams 31c, 32c, and 33c diffracted by the hologram element 5C.

  In this optical pickup device, recording and signal reading of three types of recording media having different recording density standards, that is, CD, DVD, and BD are possible. In addition, this optical pickup device does not require complicated components and requires a small number of components. Therefore, it is small and configured at low cost.

  Note that, as shown in FIGS. 8A and 8B, the beam splitter component 9C can be omitted as in the relationship of the second embodiment (FIG. 4A) with respect to the first embodiment (FIG. 1A). In that case, the pattern of the diffraction grating 1D and the second photodiode chip 2D of the hologram element 5D in FIGS. 8A and 8B is the pattern of the diffraction grating 1A and the second photodiode chip 2A of the hologram element 5A shown in FIG. 4C. It is transformed in the same way. Therefore, in the second photodiode chip 2D, in addition to the focus error signal components of the laser beams 31c, 32c, and 33c diffracted by the hologram element 5D, the high-frequency signal component and the tracking signal component are respectively converted into the laser beams 31c and 32c. , 33c can be detected at substantially the same point on the light receiving surface.

  In such an optical pickup device, the number of parts can be further reduced. Therefore, it is further reduced in size and cost.

It is a figure which shows the place which looked at the optical pick-up apparatus of one Embodiment of this invention from upper direction. It is a figure explaining operation | movement of the optical pick-up apparatus of FIG. 1A. It is a figure which shows the pattern layout of the 1st photodiode chip | tip of the optical pick-up apparatus of FIG. 1A. It is a figure which shows the aspect which detects a focus error signal by the double knife edge method. It is a figure which shows the aspect which detects a focus error signal by the single knife edge method. It is a figure which shows the aspect in which the laser beam is radiate | emitted only from the 2nd semiconductor laser chip with the optical pick-up apparatus of FIG. 1A. It is a figure which shows typically the place which looked at the thing of FIG. 2A from the side. It is a figure which shows the aspect which detects a focus error signal by the double knife edge method, when the laser beam is radiate | emitted only from the 2nd semiconductor laser chip with the optical pick-up apparatus of FIG. 1A. It is a figure which shows the aspect in which the laser beam is radiate | emitted only from the 1st semiconductor laser chip with the optical pick-up apparatus of FIG. 1A. It is a figure which shows typically the place which looked at the thing of FIG. 3A from the side. It is a figure which shows the aspect which detects a focus error signal by the double knife edge method, when the laser beam is radiate | emitted only from the 1st semiconductor laser chip with the optical pick-up apparatus of FIG. 1A. It is a figure which shows the place which looked at the optical pick-up apparatus of another embodiment of this invention from upper direction. It is a figure explaining operation | movement of the optical pick-up apparatus of FIG. 4A. It is a figure which shows the aspect which detects a signal with the optical pick-up apparatus of FIG. 4A. It is a figure explaining how to produce a general hologram. Light reception incident on the light receiving element when a hologram diffraction grating is designed with a wavelength λm substantially intermediate between the first wavelength 780 nm and the second wavelength 650 nm, and reproduction is performed at the same wavelength (λm) as the design wavelength λm. It is a figure which shows the pattern and position of a spot. A hologram diffraction grating is designed at a substantially intermediate wavelength λm between the first wavelength 780 nm and the second wavelength 650 nm, and reproduction is performed at a wavelength shorter than the design wavelength λm (second wavelength 650 nm) on the light receiving element. It is a figure which shows typically the pattern and position of the incident light-receiving spot. A hologram diffraction grating is designed with a substantially intermediate wavelength λm between the first wavelength 780 nm and the second wavelength 650 nm, and reproduction is performed with a wavelength longer than the design wavelength λm (first wavelength 780 nm) on the light receiving element. It is a figure which shows typically the pattern and position of the incident light-receiving spot. 6B is a diagram schematically showing the pattern and position of a light receiving spot incident on the light receiving element when the position of the light emitting point in FIGS. 6B and 6C is shifted from the center of the pattern of the diffraction grating. FIG. It is a figure which shows arrangement | positioning in the viewpoint corresponding to FIG. 1A of the hologram diffraction grating and light receiving element which are shown to FIG. 6A thru | or FIG. It is a figure which shows the place which looked at the optical pick-up apparatus of another embodiment of this invention from upper direction. It is a figure explaining operation | movement of the optical pick-up apparatus of FIG. 7A. It is a figure which shows the place which looked at the optical pick-up apparatus of another embodiment of this invention from upper direction. It is a figure explaining operation | movement of the optical pick-up apparatus of FIG. 8A. It is a figure which shows the place which looked at the conventional optical pick-up apparatus from upper direction. It is a figure which shows the place which looked at the optical pick-up apparatus of FIG. 9A from the side.

Explanation of symbols

1, 1A, 1B, 1C, 1D Hologram diffraction grating 2, 2B, 2C, 2D Second photodiode chip 3 Second semiconductor laser chip 4 First semiconductor laser chip 5, 5A, 5C, 5D Hologram element 7 First beam splitter 8 Second beam splitter 9, 9C Beam splitter component 10, 10C First photodiode chip 21 Third beam splitter surface 22 Third semiconductor laser chip

Claims (13)

A light source group that emits light beams with different wavelengths to the optical path is provided, and the recording medium is irradiated with a light beam from one of the light sources selected according to the recording density of the recording medium, and the reflection modulated by the recording medium An optical pickup device for reading a signal by branching light from the optical path,
The light source group includes a first light source and a second light source that are arranged in a direction substantially perpendicular to the optical path and emit light beams having a first wavelength and a second wavelength, respectively.
A first beam splitter surface for branching the light beam of the first wavelength modulated by the recording medium and a second beam splitter surface for branching the light beam of the second wavelength modulated by the recording medium on the optical path. In parallel with each other, and the first beam splitter surface and the second beam so as to eliminate the deviation of the optical axis of each branched light beam caused by the distance between the first light source and the second light source. The distance to the splitter surface is set,
A first light receiving element for commonly detecting a high-frequency signal component and a tracking signal component of each of the light beams branched on the first or second beam splitter surface;
The light beams of the first wavelength and the second wavelength transmitted through the first and second beam splitter surfaces and returned on the optical path between the light source group and the group formed by the first and second beam splitter surfaces. Including a hologram element that diffracts so as to eliminate the deviation of the optical axis due to the distance between the first light source and the second light source,
An optical pickup device comprising a second light receiving element for commonly detecting a focus error signal component of each of the light beams diffracted by the hologram element. The optical pickup device according to claim 1,
An optical pickup device, wherein the first beam splitter surface and the second beam splitter surface are integrally included in the same optical component. The optical pickup device according to claim 1,
An optical pickup device, wherein the first and second beam splitter surfaces and the hologram element are fixed together. The optical pickup device according to claim 1,
The second light receiving element detects the focus error signal component of each light beam diffracted by the hologram element at substantially the same point on the light receiving surface with respect to each light beam. apparatus. The optical pickup device according to claim 1,
The second light receiving element is a light beam having a shorter wavelength than the first light source and the second light source in a direction substantially perpendicular to the optical path and shorter than the first wavelength and the second wavelength. An optical pickup device disposed on the side of a light source that emits light. The optical pickup device according to claim 1,
The first and second beam splitter surfaces and the first light receiving element are abolished,
The optical pickup device, wherein the second light receiving element detects a high frequency signal component and a tracking signal component in addition to a focus error signal component of each light beam diffracted by the hologram element. The optical pickup device according to claim 6,
The second light receiving element detects a focus error signal component, a high frequency signal component, and a tracking signal component of each light beam at substantially the same point on the light receiving surface with respect to each beam. apparatus. The optical pickup device according to claim 6,
The second light receiving element is a light beam having a shorter wavelength than the first light source and the second light source in a direction substantially perpendicular to the optical path and shorter than the first wavelength and the second wavelength. An optical pickup device arranged on the side of a light source that emits light. The optical pickup device according to claim 6,
The optical pickup device, wherein the hologram element is divided into three or more regions corresponding to a focus error signal component, a high frequency signal component, and a tracking signal component of each light beam. The optical pickup device according to any one of claims 1 to 9,
The optical pickup device, wherein the second light receiving element has a pair of light receiving regions so as to generate the focus error signal by a single knife edge method. The optical pickup device according to any one of claims 1 to 5,
The optical pickup device, wherein the second light receiving element has two pairs of light receiving regions so as to generate the focus error signal by a double knife edge method. The optical pickup device according to any one of claims 1 to 11,
An optical pickup device, wherein a hologram for diffracting each light beam of the hologram element is formed at a substantially intermediate wavelength between the first wavelength and the second wavelength. The optical pickup device according to any one of claims 1 to 12,
The light source group includes a third light source arranged side by side with the first light source and the second light source in a direction substantially perpendicular to the optical path, and emitting a light beam having a third wavelength,
A third beam splitter surface for branching the light beam of the third wavelength modulated by the recording medium in parallel with the first and second beam splitter surfaces on the optical path; The distance between each beam splitter surface is set so as to eliminate the deviation of the optical axis of each branched light beam caused by the above,
The first light receiving element commonly detects a high-frequency signal component and a tracking signal component of each of the light beams branched by the first, second, or third beam splitter surface;
The hologram element is provided on an optical path between the light source group and a group formed by the first, second, and third beam splitter surfaces, and the light of each wavelength transmitted through the beam splitter surfaces and returned. The beam is diffracted so as to eliminate the deviation of the optical axis due to the distance between the light sources,
The optical pickup device, wherein the second light receiving element detects in common a focus error signal component of each of the light beams diffracted by the hologram element.

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