JP2008217881A - Optical pickup and information processor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To suppress harmful stray lights caused in an optical beam transmission adjusting means for adjusting the light power of a light beam without causing enlargement of mechanism. <P>SOLUTION: A holder holding a first transmitting element and a second transmitting element of an optical beam transmission adjusting means has constitution, where when an angle between a first reference plane and the first transmitting element is denoted as θ1 and an angle between the first reference plane and a second reference plane is denoted as θ2, θ1 and θ2 are calculated by using expression 1 and expression 2 from a second transmitting element angle θ3 at which harmful stray light is not produced by reflection of the second transmitting element when the light beam is, at a first position where the light beam is transmitted through the first transmitting element and from a first transmitting element angle θ4, at which effective luminous flux is not shielded by the first transmitting element, when the light beam is at a second position where the light beam transmits the second transmitting element. Expression 1 is θ1=(θ3+θ4)/2, and expression 2 is θ2=(180°+θ3-θ4)/2. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

 The present invention relates to an optical pickup and an information processing apparatus. More specifically, the present invention relates to an optical pickup and an information processing apparatus that emit a short-wavelength semiconductor laser such as a blue-emitting semiconductor laser using a GaN-based semiconductor. About.

A DVD is known as an information recording medium (optical disc) capable of recording digital data at a recording density about six times that of a CD and capable of writing large-capacity digital data such as movies and music. In recent years, since the amount of information that is symmetric with respect to recording has increased, an information recording medium having a larger capacity has been demanded.

 In order to increase the capacity of the information recording medium of the optical disc, it is necessary to increase the information recording density. This is generally realized by reducing the spot diameter of the laser beam emitted to the optical disc at the time of data writing and reading. In order to reduce the spot diameter of the light, the wavelength of the laser light can be shortened and the numerical aperture (NA) of the objective lens can be increased. Furthermore, for example, by using a blue laser beam having a wavelength of 405 nm and an objective lens having an NA of 0.85, information can be recorded at a recording density five times that of the current DVD.

 In addition to shortening the wavelength of laser light using a blue laser or the like, development of a technique for providing a plurality of recording layers on one optical disk has been advanced in order to further increase the recording density. For example, if it becomes possible to obtain an optical disc having two recording layers, the recording density is a DVD having one recording layer in combination with the above-described shortening of the laser beam wavelength and the use of an objective lens having a large NA. About 10 times.

However, in an optical disk apparatus using a blue laser as a light source, the margin of optical power for reproduction in the blue laser is extremely small, so that quantum noise of the light source becomes a problem.
For example, the conventional optical disc apparatus shown in Patent Document 1 discloses an optical pickup provided with a light beam transmission adjusting means (intensity filter) so that it can be taken in and out substantially perpendicularly to a laser beam path. In this optical disk apparatus, an intensity filter is inserted into the laser beam path during reproduction, and the intensity filter is moved away from the path of emitted light during recording. Thereby, for example, the quantum noise of the semiconductor laser can be kept low, and high quality reproduction is possible.

However, since this optical disk apparatus is provided with an intensity filter that can be taken in and out linearly with respect to the laser beam path, a space for moving the intensity filter is required. As a result, the optical pickup apparatus is large-sized. There has been a problem that it has become.
In order to solve such a problem, another optical pickup device provided with an intensity filter that moves on the optical axis by rotation instead of the intensity filter that moves linearly on the optical axis can be considered. Hereinafter, this optical pickup will be described with reference to FIGS.

 FIG. 3 shows a configuration of a conventional optical pickup device. When the GaN-based first semiconductor laser light source 30 emitting blue light emits a blue first light beam 44, the first light beam 44 enters the light beam transmission adjusting means 31. The light beam transmission adjusting means 31 is rotated to a predetermined position according to whether data is read from the optical disk 32 or data is written to the optical disk 32, and the position of the intensity filter is adjusted. The first light beam 44 transmitted through the light beam transmission adjusting unit 31 is reflected by the beam splitter 33, converted into parallel light by the collimating lens 34, reflected by the mirror 35, and transmitted through the first objective lens 36. It is condensed on the optical disk 32.

 At the time of reading data, the condensed first light beam 44 is reflected by the recording layer of the optical disc 32, reaches the beam splitter 33 through the reverse path, passes through the beam splitter 33, passes through the multi lens 37, and is a photodiode. 38 is incident. The photodiode 38 is a so-called photodetector, and outputs an electrical signal based on the position and intensity of incident light. Data is reproduced based on the electrical signal.

 On the other hand, when writing data, a light spot is formed on the information layer by the condensed first light beam 44. As a result, the state (for example, crystal state) of the recording layer in the portion where the light spot is formed changes according to the data to be written. As a result, data is written on the optical disc 32 as a change in the state of the recording layer.

 The second light beam 45 emitted from the second semiconductor laser light source 40 that is emitted in the wavelength region from green to ultraviolet rays is omitted in detail, but passes through an optical system 41 similar to that of the first light beam. The light passes through the objective lens 39 and is condensed on the optical disk 32. Since the return optical system of the second beam reflected by the optical disc 32 is the same as the first beam, a description thereof will be omitted.

4 and 5 show examples of conventional light beam transmission adjusting means.
4A is a perspective view of a rotation drive switching mechanism 12 that is a conventional light beam transmission adjusting means, and FIG. 4B is an exploded view of the rotation drive switching mechanism 12. 5A is a front view showing a first position where the first light beam of the rotation drive switching mechanism 12 is transmitted through the first transmission element 1, and FIG. 5B is a diagram showing the first light beam. FIG. 6 is a front view showing a second position that is transmitted through the second transmissive element 2. The configuration of the rotation drive switching mechanism will be described below with reference to FIGS. 4A and 4B and FIGS. 5A and 5B as appropriate.

 As shown in FIG. 4B, the rotation drive switching mechanism 12 includes a base 3, coils 4, 5, iron cores 6, 7, a holder 8, permanent magnets 9, 10, and first and second transmissions. It is comprised by the elements 1 and 2. The base 3 integrally includes a coil holding portion 14 for mounting the coils 4 and 5, a shaft 11 for rotating and holding the holder 8, and a regulating surface 16. The coil 4 and the coil 5 are connected in series, the iron core 6 is inserted into the coil 4, the iron core 7 is inserted into the coil 5, and the direction of the generated magnetic poles when the coils 4 and 5 are energized is equal to the coil holding portion 14 of the base 3. It is bonded and fixed so that The base 3 is bonded and fixed to an optical pickup base (not shown) so that the coils 4 and 5 are parallel to the optical axis of the first light beam. The restricting surface 16 is formed in parallel with the end surfaces of the coils 4 and 5 and is perpendicular to the optical axis of the first light beam when fixed to the optical pickup base.

The holder 8 is formed with a first mounting surface 18 and a second mounting surface 19 that are orthogonal to each other. The first mounting surface 18 has the first transmission element 1, and the second mounting surface 19 has the second mounting surface 19. The second transmissive elements 2 are bonded and fixed to each other.
The first transmission element 1 is coated with an optical filter 1a having a transmittance of 50 to 65%, and attenuates the optical power of the transmitted first light beam. On the other hand, the second transmission element 2 is not coated with an optical filter, and transmits the light beam while maintaining the optical power of the first light beam substantially. The first and second transmission elements 1 and 2 are made of parallel flat glass having a thickness of about 0.2 mm. As will be described later, the optical axis shift due to the relative angle error of the transmissive element at the time of switching is minimized by reducing the thickness. The holder 8 is formed with two small projection sets 20a, 20b, 20c and 21a, 21b, 21c each having a spherical shape at the tip, as shown in FIG. 5 (a) or (b). As shown, the first reference surface 20 formed by the tips of the three small protrusion sets 20a, 20b, 20c is parallel to the first mounting surface 18, and the tips of the three small protrusion sets 21a, 21b, 21c are Small protrusion sets 20a, 20b, 20c and 21a, 21b, 21c are formed so that the second reference surface 21 to be formed is parallel to the second mounting surface 19, respectively.
The holder 8 has two permanent magnets 9 and 10, each of which has a magnetization direction orthogonal to the first reference plane, the permanent magnet 10 is orthogonal to the second reference plane, and has a polarity. The a part of the permanent magnet 9 on the first reference surface side and the b part of the permanent magnet 10 on the second reference surface side are bonded and fixed so as to have opposite polarities. That is, as shown to Fig.5 (a), if the a part of the permanent magnet 9 is set to N pole, the b part of the permanent magnet 10 will be arrange | positioned to S pole.

 As shown in FIG. 4B, a hole 24 is formed in the center of the holder 8 in a direction parallel to both the first mounting surface 18 and the second mounting surface 19. As shown in FIG. 5A, the distance L from the center of the hole 24 to the first reference surface 20 and the center of the hole 24 to the second reference surface 21 is equal, and the restriction surface 16 of the base 3 and the shaft 11 It is formed so that it may become equal to the distance. As shown in FIG. 4B, a pair of resin springs 25 with the toes outward are integrally formed at the tip of the shaft 11 of the base 3, and when the holder 8 is inserted, the holes 24 are formed by elastic deformation. After insertion, the toes are opened to the original state and the holder 8 is held so as not to fall off. After the insertion, the holder 8 is set to have a clearance of about 0.1 mm in the axial direction of the shaft 11, and the diameter of the holding shaft 11 is formed to be about 10% smaller than the diameter of the hole 24 of the holder 8. In this way, by setting the fitting state with a large backlash in both the axial direction and the hole radial direction, when the holder 8 rotates the shaft 11, the holder 8 can rotate smoothly with almost no sliding resistance.

Next, the switching operation of the first and second transmissive elements will be described.
When the holder 8 is rotated in any direction, for example, counterclockwise, an attractive force is generated between the permanent magnet 9 and the iron core 6, and the small protrusion sets 20 a, 20 b, and 20 c are formed on the restriction surface 16 of the base 3. Abut. FIG. 5A shows a state where the small protrusion sets 20a, 20b, and 20c are in contact with the regulating surface 16, that is, a first position where the first light beam is transmitted through the first transmission element.

 As described above, since the distance from the regulating surface 16 to the shaft 11 and the distance from the first reference surface 20 of the holder 8 to the hole 24 are set to be equal to each other, the hole 24 and the shaft 11 are in this first position. Since there is a gap in the optical axis direction and the gap can move freely in the direction perpendicular to the optical axis, the small protrusion sets 20a, 20b and 20c can be controlled by the attractive force of the permanent magnet 9 and the iron core 6 at all three points. The first reference surface 20 that is in contact with the surface 16 and formed by the small protrusion sets 20 a, 20 b, and 20 c is flush with the regulation surface 16. Therefore, the first transmission element 1 parallel to the first reference surface 20 is also parallel to the regulation surface 16, that is, perpendicular to the optical axis of the first light beam.

Next, a mechanism for rotating from the first position to the second position will be described.
Now, when in the first position shown in FIG. 5A, a pulse current is supplied to the coil 4 in a direction to generate a magnetic field of N pole so as to repel the polarity of a of the permanent magnet 9, here N pole. . When the current value at this time is set so that a repulsive force exceeding the attractive force between the permanent magnet 9 and the iron core 6 is generated, the holder 8 is given a clockwise rotational driving force as a result of applying the pulse current and starts rotating. The pulse current application time is set to be about 10 msec longer than the time when the holder 8 starts to rotate and moves to the second position. As a result, when the holder exceeds the middle between the first position and the second position, in addition to the rotational force due to inertia, this time the polarity of the b part of the permanent magnet 10, here the S pole, and the N pole generated in the coil 5 Therefore, the holder 8 continues to rotate until the other small protrusion set 21 a, 21 b, 21 c abuts against the regulation surface 16.

 FIG. 5B shows a second position where the small protrusion sets 21 a, 21 b, and 21 c are in contact with the regulating surface 16 and the first light beam is transmitted through the second transmissive element 2. The pulse current disappears about 10 msec after the holder 8 rotates and stops at the second position, but the second position is maintained by adsorbing the permanent magnet 10 and the iron core 7 even after the disappearance. . In this state, since the second reference surface 21 is in the same plane as the restriction surface 16 as in the first position shown in FIG. 5A, the second transmissive element 2 is parallel to the restriction surface 16, It becomes perpendicular to the optical axis of one light beam.

 When switching from the second position to the first position again is applied to the coils 4 and 5 in the direction opposite to the pulse current that flows when switching from the first position to the second position, the regulation surface 16 side A magnetic field opposite to the previous one is generated on the end face of the coil 5 and repels the permanent magnet 10, and this time the holder rotates counterclockwise and switches to the first position. As an example, the applied voltage and pulse current are applied to the coil when the inner diameter of the coil (= iron core diameter) is 1.3 mm, the outer diameter of the coil is 2.3 mm, the coil length is 3.2 mm, and the coil alignment is φ0.08 mm. The coil resistance is 7.2Ω, the applied voltage is 5 V, the pulse current is 700 mA, and the application time is about 40 msec.

Next, the influence of the switching angle error between the first transmissive element and the second transmissive element will be described with reference to FIG.
6A shows the relationship between the transmissive element and the optical axis at the first position, and FIG. 6B shows the relationship between the transmissive element and the optical axis at the second position. If the first transmission element 1 is perpendicular to the optical axis as shown in FIG. 6 (a), the optical axis does not change even if the light beam passes through the transmission element 1, but as shown in FIG. 6 (b). In addition, when the second transmissive element 2 has an angle error n when switched to the second position, if the light beam is transmitted through the second transmissive element 2, refraction occurs due to Snell's law and the optical axis shifts d. Occurs. When a deviation occurs in the optical axis, a deviation occurs in the position of the spot collected and reflected on the optical disk and returned to the photodetector. If the spot position shift is large, it will protrude from the photodetector, resulting in signal degradation. The optical axis deviation due to the angle error occurs when the light beam transmitted through the transmission element is divergent light as in this configuration example, and when parallel light is transmitted there is no optical axis deviation. The optical axis deviation d increases as the angle error n increases and the thickness t of the transmissive element increases. For this reason, the transmissive element thickness t is reduced to about 0.2 mm. As an example, when the transmissive element thickness t is 0.2 mm, the allowable angle error n is about ± 1 °. Further, since the photodetector is adjusted and assembled so as to be optimal at either the first or second position, the allowable angle error is not an absolute angle with respect to the optical axis, but the first transmission element 1 and the second transmission. It is determined by the relative angle error of element 2.

The switching angle error in the rotation drive switching mechanism 12 of the conventional example is based on the above description, the flatness of the restriction surface 16 of the base 3, the parallelism of the first reference surface 20 and the first mounting surface 18, and the second This is determined only by the parallelism between the reference surface 21 and the second mounting surface 19, but achieving a switching angle error of ± 1 ° with the base 3 and the holder 8, which are resin molded parts, is a problem in terms of molding accuracy. Never become.
JP 2000-195086 A

 However, the conventional rotational drive switching mechanism can reduce the angular deviation due to the switching operation with a simple configuration and realize downsizing of the apparatus, while the first position shown in FIG. In this state, a part of the light beam in the blue wavelength region, which is divergent light, is reflected by the second transmission element 2 to become stray light 26, which is incident on the second objective lens 39 (not shown), and the second objective lens. When 39 is made of resin, since the resin material has low weather resistance with respect to the light beam in the blue wavelength region, the material deteriorates and the optical performance of the lens deteriorates.

 As a first method for preventing generation of harmful stray light with respect to the resin lens that is reflected by the second transmissive element 2, the angle of the light beam of the second transmissive element 2 with respect to the optical axis at the first position is set. It is conceivable to tilt the second objective lens 39 so that it does not enter the second objective lens 39. As an example, the tilt angle needs to be about 15 degrees clockwise. FIG. 7 shows the first method. As shown in FIG. 7, when the first mounting surface 18 and the first reference surface 20 and the second mounting surface 19 and the second reference surface 21 are configured in parallel, the first reference surface 20 and the second reference surface 20 are formed. The angle θ2 ′ with the mounting surface 19 needs to be about 105 °. However, if θ2 ′ is to be increased, the holder 8 becomes larger due to design limitations. FIG. 7 shows the original shape as a comparison with a two-dot chain line. As shown in the figure, as the holder becomes larger, the weight increases compared to the original shape, and the moment of inertia increases by about 70%. When the weight and the moment of inertia increase, the minimum driving voltage increases, which causes a problem that low voltage driving becomes difficult. In order to avoid enlarging the holder, as a second method of preventing stray light, the angle θ2 between the first reference surface and the second reference surface remains 90 °, and the first mounting surface and the first mounting surface A method of providing an angle θ1 (= 15 °) between the reference surface and the second mounting surface and the second reference surface is also conceivable. FIG. 8A shows the first position of the second method, and FIG. 8B shows the second position of the second method. As shown in FIG. 8A, in the first position, the second transmission element 2 prevents stray light with an angle θ1 inclined with respect to the optical axis. At this time, since the first transmission element 1 is also inclined by the angle θ1 from the perpendicular to the optical axis, the optical axis is shifted, and the spot position reflected on the recording medium and returned to the light receiving element is shifted. There is no problem because the quantity on the element is several tens of microns and can be absorbed sufficiently by adjustment during assembly of the light receiving element.

 However, in the case of this second method, as shown in FIG. 8B, the angle θ4 with respect to the optical axis of the first transmissive element 1 is equal to the angle θ1 at the second position. If the angle exceeds 60 °, the first transmission element 1 shields a part 43 (shaded portion) of the effective luminous flux 42 of the light beam transmitted through the second transmission element 2. Since the angle at which shielding starts is smaller than the angle necessary for preventing stray light, the second method has a problem in that stray light prevention and effective light beam shielding avoidance are not compatible.

 An optical pickup according to the present invention includes a first light source that emits a first light beam having a predetermined optical power, a light beam transmission adjusting unit that adjusts a transmission amount of the first light beam, and the light beam transmission adjustment. A first condensing means for condensing the first light beam transmitted through the means onto an information recording medium, a second light source for emitting a second light beam having a predetermined optical power, and the second light. And a second condensing unit that condenses the beam on the information recording medium.

 The light beam transmission adjusting means includes a first transmissive element having a first transmittance and a second transmissive element having a second transmittance higher than the first transmittance. Rotation drive switching for switching between a first position where the first light beam is transmitted through the first transmission element and a second position where the first light beam is transmitted through the second transmission element around a rotation axis parallel to the second transmission element. The rotation drive switching mechanism is configured to hold the first transmission element and the second transmission element, and to provide a holding body provided with a rotation hole parallel to the first transmission element and the second transmission element; A permanent magnet that generates an attracting force for maintaining the first position and the second position to be mounted on the holding body, and a rotation hole of the holding body are fitted into the first light beam. The first position in which the shaft on the center line is integrally formed And a base for holding the holding body in the second position, a first iron core for adsorbing one magnetic pole of the permanent magnet respectively mounted on the base, and the first iron core are concentric with the permanent magnet. A first coil for applying a repulsive force to the one magnetic pole of the magnet, a second iron core for adsorbing the other magnetic pole of the permanent magnet, and the other coil of the permanent magnet concentric with the second iron core. A first reference surface that is in contact with the base at the first position that forms an angle of θ1 with the first transmission element on the holding body. And the second reference surface that contacts the base at the second position that forms an angle θ1 as in the second transmission element, and the angle θ2 between the first reference surface and the second reference surface is approximately 90 degrees. And the base includes the first reference surface of the holding body and the first base. The reference surface is regulating surface abutting is formed.

 When the rotational drive switching mechanism is in the first position, the clockwise angle θ3 of the transmission surface of the second transmission element with respect to the optical axis of the first light beam is transmitted through the first transmission element. An angle is set such that a part of the first light beam is reflected by the second transmission element and becomes stray light and does not enter the second light collecting means.

 When the rotation drive switching mechanism is in the second position, the clockwise angle θ4 with respect to the optical axis of the first light beam of the transmission surface of the first transmission element is transmitted through the second transmission element. The angle is set such that the effective light beam of the first light beam is not shielded by the first transmission element.

 Further, the angle θ1 of the holding body is set to a value calculated by the mathematical formula 1 from the angle θ3 and the angle θ4.

Further, the angle θ2 of the holding body is set to a value calculated by the mathematical formula 2 from the angle θ3 and the angle θ4.
The first light source may be a semiconductor laser that emits light in a blue wavelength region.
The second light source may be a semiconductor laser that emits light in a wavelength region from green to ultraviolet.

 An information processing apparatus according to the present invention generates an at least one of a reproduction signal and a servo signal based on an optical pickup that further includes a photodetector that detects reflected light from the information recording medium, and the detected reflected light A signal processing circuit may be provided.

 The information processing apparatus can be loaded with a plurality of types of information recording media having different numbers of recording layers, and the amount of optical power corresponding to the number of recording layers can be set on the loaded information recording medium. A light beam is emitted to read and / or write data.

 When the information recording medium having one recording layer is loaded, the information processing apparatus switches to the first position by the rotational drive switching mechanism and applies a first optical power to the recording layer. When an information recording medium having a plurality of recording layers is loaded, the rotational drive switching mechanism switches to the second position, and a second is applied to one of the recording layers. A light beam having optical power may be emitted.

 According to the present invention, the light beam transmission adjusting means for switching the light power of the light beam by rotationally driving two transmission elements having different transmittances does not increase the mechanism volume, and the light is transmitted at one switching position. Preventing generation of harmful stray light due to reflection of the transmissive element that does not transmit the beam, and the transmissive element that does not transmit the light beam at the other switching position shields the effective light beam of the light beam. Therefore, it is possible to provide a small optical pickup with low power consumption.

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

 FIG. 1 is a perspective view of a rotary drive switching mechanism 12 which is a light beam transmission adjusting means according to the present invention. Since the present invention relates to the angular configuration of the first and second transmission elements of the holder and the first and second reference planes, the configuration itself of the rotational drive switching mechanism is exactly the same as the conventional one, and the description thereof is omitted.

 2A and 2B are diagrams showing the angular configuration of the holder 8. FIG. 2A shows a first position where the first light beam passes through the first transmission element 1, and FIG. 2B shows a second position where the first light beam passes through the second transmission element 2. Each position is shown.

As shown in FIG. 2A, the angle θ3 formed by the second transmissive element 2 at the first position and the optical axis of the first light beam is such that the first light beam is reflected by the second transmissive element 2. And formed at the tips of the small protrusion sets 20a, 20b, and 20c of the holder 8 so that the minimum necessary angle at which the light does not enter the second objective lens 39 (not shown), for example, 15 degrees, is formed. The angle θ2 ′ of the second mounting surface 18 with respect to one reference surface 20 is formed to be 105 degrees.
Further, as shown in FIG. 2B, the angle θ4 formed by the first transmission element 1 at the second position with the optical axis of the first light beam is the first light beam transmitted through the second transmission element 2. The first mounting on the second reference surface 21 formed at the tip of the small protrusion sets 21a, 21b, 21c of the holder 8 so as to be the maximum necessary angle that does not block the effective light beam 42, for example, 5 degrees as an example. The surface 18 angle θ5 is formed to be an angle of 85 degrees.

 Here, the reason why the angle θ3 is set to the necessary minimum value and the angle θ4 is set to the necessary maximum value is that the larger the angle θ3 is, and the smaller the angle θ4 is, the larger the holder 8 is and the minimum driving voltage is increased. In order to reduce the size of the drive switching mechanism 12, it is necessary to make the angle θ3 as small as possible and the angle θ4 as large as possible.

 Further, the angle θ1 of the first transmission element 1 with respect to the first reference plane 20 at the first position shown in FIG. 2A is relative to the second reference plane 21 at the second position shown in FIG. The angle θ1 ′ of the second transmission element 2 must be equal to the angle of the first transmission element 1 with respect to the optical axis of the first light beam and the second transmission element 2 as described with reference to FIG. This is because if the angle is shifted, the optical axis shift of the first light beam transmitted through the transmission element occurs when switching, and the spot position reflected on the storage medium and returning to the light receiving element is shifted.

 Further, it is desirable that the restriction surface 16 of the base 3 on which the first reference surface 20 and the second reference surface 21 abut is the same plane. This is because, if the restriction surface is divided and an angle is formed between the surface on which the first reference surface 20 abuts and the surface on which the second reference surface 21 abuts, the coils 4 and 5 are not parallel but are arranged at the same angle. This will increase the size of the base. Moreover, it is because it is more advantageous in terms of accuracy to obtain one plane accuracy than to obtain angle accuracy of two surfaces from the base molding die structure.

As a result of taking these conditions into consideration, the angle θ1 of the first mounting surface 18 with respect to the first reference surface and the angle θ1 ′ = θ1 of the second mounting surface 18 with respect to the second reference surface are set to the values obtained by the above Equation 1. do it.
In the above numerical example, θ1 (= θ1 ′) is 10 degrees.

In addition, the angle θ2 between the first reference surface and the second reference surface shown in FIG.
In the above numerical example, θ2 is 95 °.

 In this embodiment, the light power of the light beam is switched by switching between a transmissive element coated with an optical filter and a transmissive element coated with no optical filter. However, switching between two transmissive elements having different light transmittances is performed. The optical power of the light beam may be switched with.

 In the present embodiment, the light beam transmission adjusting means switches the light power of the first light beam between data reading and writing. However, the optical power of the first light beam may be switched between when the information recording medium has one recording layer and when the information recording medium has two recording layers.

 According to the present invention, it is possible to provide a light beam transmission adjusting unit that is small in size and low in power consumption without generating harmful stray light. Therefore, a small optical pickup with low power consumption, and an information processing apparatus having such an optical pickup. Can be obtained.

The perspective view of the rotational drive switching mechanism 12 which is a light beam transmission adjustment means by this invention. (A) is a figure which shows the state in which the holder 8 exists in the 1st position which the 1st light beam permeate | transmits the 1st permeation | transmission element 1, FIG. The figure which shows the state in the 2nd position which has permeate | transmitted the transmissive element 2 of The figure which shows the structure of the conventional optical pick-up apparatus. (A) is a perspective view of the conventional rotational drive switching mechanism 12, and (b) is an exploded view of the conventional rotational drive switching mechanism 12. (A) is a front view which shows the 1st position which the 1st light beam of the conventional rotational drive switching mechanism 12 has permeate | transmitted the 1st permeation | transmission element 1, (b) is a 2nd 1st light beam is 2nd. The front view which shows the 2nd position which has permeate | transmitted the transmissive element 2 (A) is a diagram showing the relationship between the transmissive element and the optical axis at the first position, (b) is a diagram showing the relationship between the transmissive element and the optical axis when a switching angle error occurs at the second position. The figure which shows the 1st method for preventing generation of harmful stray light (A) is a figure which shows the 1st position of the 2nd method which prevents generation | occurrence | production of harmful stray light, (b) is a figure which shows the 2nd position.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 1st permeation | transmission element 2 2nd permeation | transmission element 3 Base 4, 5 Coil 6, 7 Iron core 8 Holder 9, 10 Permanent magnet 11 Base holder holding shaft 12 Rotation drive switching mechanism 14 Base coil holding part 16 Base holder Restriction surface 18 First surface of holder 19 Second surface of holder 20a, 20b, 20c Small projection of holder 20 First reference surface of holder 21a, 21b, 21c Small projection of holder 21 Second reference surface of holder 24 holder hole 30 first semiconductor laser light source 31 light beam transmission adjusting means 32 optical disk 33 beam splitter 34 collimating lens 35 mirror 36 first objective lens 37 multilens 38 photodiode 39 second objective lens 40 second semiconductor Laser light source 41 Optical system 42 Effective light beam 43 Part of shielded effective light beam 44 1 of the light beam 45 a second light beam

Claims (8)

 A first light source that emits a first light beam having a predetermined light power; a light beam transmission adjusting unit that adjusts a transmission amount of the first light beam; and the light beam transmitted through the light beam transmission adjusting unit. A first light collecting means for condensing the light beam on the information recording medium, a second light source for emitting a second light beam having a predetermined optical power, and a second light source for condensing the second light beam on the information recording medium. The light beam transmission adjusting means has a first transmission element having a first transmittance and a second transmittance higher than the first transmittance. A first position where the light beam passes through the first transmission element and a second transmission element around a rotation axis parallel to the first transmission element and the second transmission element. A rotary drive switching mechanism for switching between a second position and The rotation drive switching mechanism holds the first transmission element and the second transmission element, and has a holding body provided with a rotation hole parallel to the first transmission element and the second transmission element, and is attached to the holding body The first and second permanent magnets that generate an attracting force for maintaining the first position and the second position are engaged with the rotation hole of the holding body, and its axis is substantially the same as that of the light beam. A base for holding the holding body at the first position and the second position, which are integrally formed with an axis on the optical axis, and the first permanent magnet mounted on the base are attracted to each other. A first iron core that is concentric with the first iron core and that gives a repulsive force to the first permanent magnet, a second iron core for adsorbing the second permanent magnet, A second carp that is concentric with the second iron core and gives a repulsive force to the second permanent magnet The holding body includes a first reference surface that contacts the base at the first position that forms an angle θ1 with the first transmission element, and θ1 as with the second transmission element. A second reference surface that is in contact with the base at the second position that forms an angle such that the first reference surface and the second reference surface form an angle θ2 of approximately 90 degrees, and the base includes An optical pickup comprising a restriction surface on which the first reference surface and the second reference surface of the holder are in contact with each other.  When the rotational drive switching mechanism is in the first position, a clockwise angle θ3 of the transmission surface of the second transmission element with respect to the optical axis of the first light beam is transmitted through the first transmission element. An optical pickup characterized in that an angle is set such that a part of one light beam is reflected by the second transmission element and becomes stray light and does not enter the second light collecting means.  When the rotational drive switching mechanism is in the second position, a clockwise angle θ4 of the transmission surface of the first transmission element with respect to the optical axis of the first light beam is transmitted through the second transmission element. An optical pickup characterized by being set at an angle such that an effective light beam of the light beam is not shielded by the first transmission element. The optical pickup according to claim 1, wherein the angle θ1 of the holding body is set to a value calculated by the following formula 1 from the angle θ3 and the angle θ4.
(Equation 1)
θ1 = (θ3 + θ4) / 2 The optical pickup is characterized in that the angle θ2 of the holding body is set to a value calculated by the following mathematical formula 2 from the angle θ3 and the angle θ4.
(Equation 2)
θ2 = (180 ° + θ3-θ4) / 2  The optical pickup according to claim 1, wherein the first light source is a semiconductor laser that emits light in a blue wavelength region.  The optical pickup according to claim 1, wherein the second light source is a semiconductor laser that emits light in a wavelength region from green to ultraviolet.  The optical pickup according to any one of claims 1 to 7, further comprising a photodetector that detects reflected light from the information recording medium, and a reproduction signal and a servo signal based on the detected reflected light. An information processing apparatus comprising a signal processing circuit that generates at least one of the two.

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