JP2006040432A - Optical pickup apparatus and information processing apparatus including such an optical pickup apparatus - Google Patents

Abstract

Displacement of an optical axis caused by a light beam transmission adjusting means for adjusting the optical power of a light beam emitted from a light source is suppressed to be small.
An optical pickup device includes a light source, a light beam transmission adjusting unit, and a condensing unit. The light beam transmission adjusting means includes a first transmission element having a first transmittance, a second transmission element having a second transmittance higher than the first transmittance, and parallel to the first and second transmission elements. Support means for rotatably supporting each transmissive element around a rotation axis, and rotation drive means for rotating and driving each transmissive element around the rotation axis. The optical pickup device rotates and rotates the rotation driving means to switch between a first position where the light beam is transmitted through the first transmission element and a second position where the light beam is transmitted through the second transmission element. A light beam having a smaller first optical power and a light beam having a second optical power that is larger than the first optical power and equal to or lower than the optical power at the time of emission are selectively output.
[Selection] Figure 2

Description

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

  A digital versatile disc (DVD) is an information recording medium that can record digital data at a recording density about six times that of a compact disc (CD) and can write large-capacity digital data such as movies and music. It is known as (optical disc).

  In recent years, since the amount of information to be recorded 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. In DVD, a light source with a wavelength of 660 nm and an objective lens with NA of 0.6 are used. 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, a conventional optical disk device disclosed in Patent Document 1 discloses an optical pickup device provided with a light beam transmission adjusting means (intensity filter) that 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 vertically and linearly with respect to the laser beam path, a space for moving the intensity filter is essential. As a result, there has been a problem that the optical pickup device is increased in size.

  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, the optical pickup device will be described with reference to FIGS.

  FIG. 4 shows a configuration of a conventional optical pickup device. When the GaN-based semiconductor laser light source 41 emitting blue light emits a blue light beam, the light beam enters the light beam transmission adjusting means 200. The light beam transmission adjusting means 200 is rotated to a predetermined position depending on whether data is read from the optical disc 50 or data is written to the optical disc 50, and the position of the intensity filter is adjusted. The light beam that has passed through the light beam transmission adjusting unit 200 is reflected by the beam splitter 42, converted into parallel light by the collimator lens 43, reflected by the mirror 44, transmitted through the objective lens 45, and condensed on the optical disk 6. The

  At the time of reading data, the condensed light beam is reflected by the recording layer of the optical disk 6, reaches the beam splitter 42 through the reverse path, passes through the beam splitter 42, and enters the photodiode 48 through the multilens 47. . The photodiode 48 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 light beam. 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 6 as a change in the state of the recording layer.

  FIG. 5A is a perspective view when the light beam passes through the optical filter of the light beam transmission adjusting unit 200, and corresponds to the arrangement at the time of data reading. The light beam transmission adjusting unit 200 includes a transmission element 201. The transmissive element 201 has a first set of parallel planes composed of two parallel planes and a second set of parallel planes composed of two parallel planes. An optical filter 201a that attenuates the optical power of the transmitted light beam is applied to at least one plane of the first set of parallel planes. The light beam transmission adjusting unit 200 includes a support unit 104 that instructs the transmission element 201 and a rotation driving unit 105 that rotates the transmission element 201 around the rotation axis 103. The support means 104 supports the transmissive element 201 so that the transmissive element 201 can rotate around the rotation axis 103 parallel to the four planes constituting the first parallel plane set and the second parallel plane set. . The rotation driving unit 105 rotates the transmission element 201 around the rotation axis 103.

FIG. 5B is a perspective view when the light beam does not pass through the optical filter of the light beam transmission adjusting unit 200, and corresponds to the arrangement at the time of data writing. The light beam transmission adjusting unit 200 switches the position where the light beam passes through the first set of parallel planes of the transmission element 201 and the position where the light beam passes through the set of second parallel planes by rotating around the rotation axis 103. Thus, it is possible to switch between the case where the light beam is transmitted through the optical filter 201a and the case where the light beam is not transmitted. When the light beam passes through the optical filter 201a, the optical power can be suppressed lower than when the light beam does not pass.
JP 2000-195086 A

  However, the configuration in which the transmissive element 201 of the light beam transmission adjusting unit 200 is rotated enables a reduction in size, while improving the component accuracy and the assembly accuracy of the light beam transmission adjusting unit 200, so that it can be mounted and operated. Another problem arises that the angular deviation in time must be reduced.

  More specifically, the transmissive element 201 is an integral element having a transmissive surface having the optical filter 201a and a transmissive surface not having the optical filter 201a, and the optical power is adjusted by switching the transmissive surface by rotation. Therefore, when the light beam passes through the transmission surface having the optical filter 201a, the transmission distance of the light beam is equal to the length L of the surface not having the optical filter 201a. On the other hand, when the light beam passes through the transmission surface that does not have the optical filter 201a, the transmission distance of the light beam is equal to the length L of the surface that has the optical filter 201a.

  When the surface of the transmissive element 201 is not perpendicular to the optical axis (when an incident angle shift occurs), the light is refracted on the surface of the transmissive element 201, so that the optical axis when the light beam is incident on the transmissive element 201 and The optical axis shifts. FIG. 6A shows a state where there is no deviation of the incident angle of the light beam to the transmissive element 201 of the light beam transmission adjusting means 200. On the other hand, FIG. 6B shows a state of deviation of the optical axis when there is a deviation of the incident angle of the light beam to the transmissive element 201. According to FIG. 6B, the transmission distance of the light beam is equal to the length L of one side of the transmission surface. Therefore, when the incident angle deviation h of the light beam occurs, the transmission distance becomes longer in proportion to the length L of one side of the transmission surface, so that the optical axis deviation D occurs.

  Note that the length L of one side of the transmissive surface of the transmissive element 201 must be greater than or equal to a certain length in order to ensure the size (effective diameter) necessary for reliably transmitting the light beam. That is, it can be said that the transmission distance depends on the length. As described above, when the transmission distance is increased, the optical axis deviation D after transmission caused by refraction when the incident angle deviation of the light beam occurs increases in proportion to the transmission distance, so that the accuracy of parts and assembly can be improved. It is necessary to reduce the angle deviation.

  An object of the present invention is to suppress the deviation of the optical axis caused by the light beam transmission adjusting means for adjusting the optical power of the light beam emitted from the light source.

  An optical pickup device according to the present invention includes a light source that emits a light beam having a predetermined optical power, a light beam transmission adjustment unit that adjusts a transmission amount of the light beam, and the light beam that has passed through the light beam transmission adjustment unit. Condensing means for condensing light on the information recording medium. The light beam transmission adjusting means includes a first transmission element having a first transmittance, a second transmission element having a second transmittance higher than the first transmittance, the first transmission element, Support means for rotatably supporting the first transmissive element and the second transmissive element around a rotation axis parallel to the second transmissive element; and the first transmissive element and the second transmissive element. Rotation drive means for rotating around the rotation axis. The optical pickup device rotates and rotates the rotation driving means to switch between a first position where the light beam is transmitted through the first transmissive element and a second position where the light beam is transmitted through the second transmissive element. A light beam having a first light power smaller than the predetermined light power and a light beam having a second light power larger than the first light power and less than or equal to the predetermined light power are selectively output.

  The transmission distance when the light beam passes through the first transmission element is shorter than the length of each side constituting the surface of the second transmission element, and the light beam passes through the second transmission element. The transmission distance may be shorter than the length of each side constituting the surface of the first transmission element.

  The transmission distance when the light beam passes through the first transmission element or the second transmission element may be shorter than the length of the side constituting the incident surface of any of the transmission elements.

  The light source may be a semiconductor laser that emits light in a wavelength region from green to ultraviolet.

  The light source may be a semiconductor laser that emits light in a blue wavelength region.

  The information processing apparatus according to the present invention includes the optical pickup device further including a photodetector that detects reflected light from the information recording medium, and at least one of a reproduction signal and a servo signal based on the detected reflected light. There may be provided a signal processing circuit for generating.

  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 an information recording medium having one recording layer is loaded, the information processing apparatus switches to the first position by rotationally driving the rotation driving unit, and the first recording layer is switched to the first recording layer. When an information recording medium having a plurality of recording layers emitting a light beam having optical power is loaded, the rotation driving means is rotated to switch to the second position, and the recording layer 1 A light beam having the second optical power may be emitted to one of the two.

  According to the present invention, it is possible to obtain light beam transmission adjusting means for switching the light power of a light beam by rotationally driving two transmission elements having different transmittances. Since the thickness of the transmission element of the light beam transmission adjusting unit 100 is not limited to the effective diameter of the light beam, even if the component accuracy and the assembly accuracy are the same as the conventional one, the light beam transmission adjusting unit can shift the incident angle of the light beam. The deviation of the optical axis after transmission caused by refraction when it occurs can be kept small. In addition, it is possible to improve device reliability and reduce manufacturing costs.

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

  FIG. 1 shows a functional block configuration of an optical disc apparatus 10 according to the present embodiment. The optical disc device 10 includes an optical pickup device 11, a signal processing circuit 12, and a servo control circuit 13. Although FIG. 1 shows an optical disk 14, this is for convenience of explanation and is not a component of the optical disk device 10.

  First, an outline of the operation of the optical disc apparatus 10 will be described. The optical pickup device 11 emits a light beam to the optical disc 14 to detect the reflected light from the optical disc 14 and outputs a light amount signal corresponding to the detection position and the detected light amount of the reflected light. The signal processing circuit 12 responds to a light amount signal output from the optical pickup device 11, a focus error (FE) signal indicating a focused state of the light beam on the optical disk 14, a focus position of the light beam, and a track of the optical disk 14. A tracking error (TE) signal or the like indicating the positional relationship is generated and output. The FE signal and the TE signal are collectively referred to as a servo signal. The servo control circuit 13 generates and outputs a drive signal based on these signals. The drive signal is input to an actuator coil 6 of the optical pickup device 11 described later, and the position of the objective lens 5 is adjusted. Thus, the focal point of the light beam emitted to the optical disc 14 is controlled so as not to deviate from the recording layer.

  In a state where the focal point of the light beam is controlled so as not to deviate from the recording layer, the signal processing circuit 12 outputs a reproduction signal based on the light amount signal. The reproduction signal indicates data written on the optical disk 14. Thereby, reading of data from the optical disk 14 is realized. Further, by making the optical power of the light beam larger than that during reproduction, data can be written on the optical disk 14.

  Hereinafter, the configuration of the optical pickup device 11 will be described. One of the main features of the optical pickup device 11 according to the present embodiment is that the light beam transmission adjusting means 100 is composed of two transmission elements having different light transmittances. The light beam transmission adjusting means 100 can adjust the optical power of the light beam by switching these transmission elements by rotational driving.

  The optical pickup device 11 includes a light source 1, a light beam transmission adjusting unit 100, a beam splitter 2, a collimator lens 3, a mirror 4, an objective lens 5, an actuator coil 6, a multilens 7, and a photodiode 8. With.

  The light source 1 is a GaN-based semiconductor laser that emits blue light. The light source 1 also emits coherent light for reading and writing data to the recording layer of the optical disc 14.

  The light beam transmission adjusting means 100 is an optical element that changes the light power by changing the light transmittance and keeping the quantum noise of the light beam emitted from the light source 1 low. Here, a detailed configuration of the light beam transmission adjusting unit 100 will be described with reference to FIGS.

  2A is a perspective view when the light beam 20 is transmitted through the optical filter of the light beam transmission adjusting unit 100, and FIG. 2B is a perspective view of the optical filter of the light beam transmission adjusting unit 100. It is a perspective view when not transmitting. The light beam 20 travels in the direction indicated by the arrow.

  The light beam transmission adjustment unit 100 includes a first transmission element 101, a second transmission element 102, a rotation shaft 103, a support unit 104, and a rotation driving unit 105. The first transmission element 101 is coated with an optical filter 101a having a transmittance of 50%, and attenuates the optical power of the transmitted light beam. On the other hand, the second transmission element 102 is not coated with an optical filter, and transmits the light beam 20 with the optical power of the light beam substantially maintained. The support means 104 rotatably supports the first transmissive element 101 and the second transmissive element 102 around the rotation shaft 103. The rotation shaft 103 is parallel to the first transmissive element 101 and the second transmissive element 102. The rotation driving unit 105 rotates the first transmission element 101 and the second transmission element 102 around the rotation axis 103.

  The light beam transmission adjusting means 100 uses the rotation driving means 105 to rotate around the rotation axis 103, so that the light beam 20 is transmitted through the first transmission element 101 (FIG. 2A). Whether the light passes through the second transmissive element 102 (FIG. 2B) can be switched. That is, it is possible to switch whether the light beam 20 passes through the optical filter 101a or not. The light power when the light beam 20 is transmitted through the optical filter 101a is 50% of the light power when it is not transmitted.

  Refer to FIG. 1 again. The beam splitter 2 separates the light beam emitted from the light source 1. The collimating lens 3 converts the light beam emitted from the light source 1 into parallel light. The mirror 4 reflects the incident light beam and directs the reflected light beam to the optical disk 14. The objective lens 5 focuses the light beam on the recording layer of the optical disk 14. The actuator coil 6 changes the position of the objective lens 6 in a direction perpendicular to the optical disc 14 or a direction parallel to the optical disc 14 in accordance with the level of the applied drive signal. The multi lens 7 focuses the light beam on the photodiode 8. The photodiode 8 receives the light beam reflected by the recording layer of the optical disc 50 and converts it into an electric signal (light amount signal) according to the light amount. Note that the photodiode 8 may include a plurality of light receiving elements. The signal processing circuit 12 that receives the light amount signal generates an FE signal and a TE signal using information on which light receiving element the light amount signal is output from.

  Next, an operation when the optical disc apparatus 10 reads and writes data will be described. As a premise, when the optical disc 14 has two recording layers, it is assumed that the transmittance of the layer near the objective lens 5 is set to about 50%. For this reason, the magnitude of the optical power required for recording / reproducing with respect to the optical disc having two recording layers is about twice that required for the optical disc having one recording layer. The optical pickup device 11 according to the present embodiment will be described as having a function of switching the magnitude of the optical power depending on whether the recording layer of the optical disc 14 is one layer or two layers.

  First, the light source 1 emits a light beam having a predetermined optical power. At this time, it is assumed that the light beam transmission adjusting unit 100 is arranged so that the light beam passes through the optical filter 101a. The light beam emitted from the light beam transmission adjusting unit 100 is reflected by the beam splitter 2, converted into parallel light by the collimator lens 3, and reflected by the mirror 4. Thereafter, the objective lens 5 focuses the light beam on the recording layer of the optical disk 14. Reflected light from the recording layer passes through the optical pickup device 11 and enters the photodiode 8. The signal processing circuit 12 determines the number of recording layers of the optical disc 14 from the signal amplitude of the light quantity signal. Various other determination processes can be considered. For example, discrimination information for specifying the number of layers at the time of manufacture may be recorded on the inner periphery of the optical disc 14, and the discrimination information may be read as a reproduction signal to specify the number of layers. Alternatively, since the intensity of the reflected light varies depending on the type of recording medium when the laser beam is irradiated, the intensity may be detected and determined by the signal processing circuit 12. Alternatively, when the optical disk 14 is loaded in a state of being stored in the cartridge, the determination may be made according to the shape of the cartridge, which differs depending on the type of the optical disk 14. Either can be detected using the optical and / or physical properties of the loaded optical disc.

  When it is determined that the optical disc 14 has one recording layer, the light beam transmission adjusting unit 100 rotates the first transmissive element 101 and the second transmissive element 102 so that the first transmissive element 101 is light-transmitted. The second transmission element 102 is set at a position perpendicular to the axis and out of the optical path. The optical filter 101a attenuates the optical power of the incident light beam to about 50% and transmits it.

  On the other hand, when it is determined that the optical disc 14 has two recording layers, the light beam transmission adjusting unit 100 rotates the first transmission element 101 and the second transmission element 102 to perform the second transmission. The position is set such that the element 102 is perpendicular to the optical axis and the first transmission element 101 is out of the optical path. As a result, the second transmission element 102 transmits the optical power of the light beam without substantially attenuating.

  At the time of data writing, the state of the recording layer in the portion where the light spot is formed changes according to the content of the data. On the other hand, at the time of reading data, the light beam is reflected with a reflectance corresponding to the state of the recording layer of the optical disk 14. The light beam reflected by the recording layer is again transmitted through the objective lens 5, reflected by the mirror 4, transmitted through the collimator lens 3, transmitted through the multi-lens 7, and collected on the photodiode 8. As a result, the photodiode 8 generates and outputs a light amount signal. Based on the light amount signal, the signal processing circuit 12 generates a reproduction signal indicating the contents of the written data, a focus error signal, a tracking error signal, and the like.

  According to the light beam transmission adjusting unit 100 according to the present embodiment, even when the optical axis of the light beam and the incident surface of the light beam transmission adjusting unit 100 are not perpendicular (when an incident angle shift occurs), the optical axis at the time of incidence is And the optical axis at the time of emission can be kept small. Hereinafter, the reason will be described with reference to FIGS. 3 (a) and 3 (b).

  FIG. 3A shows a state where there is no deviation of the incident angle of the light beam to the first transmission element 101 of the light beam transmission adjusting means 100. The transmission distance when the light beam passes through the first transmission element 101 is equal to the thickness T of the first transmission element 101. This distance is independent of the length L of one side of the transmission surface. On the other hand, FIG. 3B shows a state of deviation of the optical axis when the incident angle deviation h of the light beam to the transmissive element 101 exists. If there is an incident angle deviation h of the light beam, an optical axis deviation d is generated in proportion to the thickness T of the transmissive element. The transmission distance of the light beam at this time is equal to or greater than the thickness T, but is sufficiently smaller than the length L of one side of the transmission surface.

  Since the light beam transmission adjusting unit 100 according to the present embodiment is separate from the transmission element 101 and the transmission element 102 having different transmittances, the length L of one side of the transmission surface of the transmission element, the thickness T of the transmission element, and the like. Can be set independently. That is, only the length L of the transmission surface is limited to the effective diameter of the light beam, and the thickness T of the transmission element can be reduced without being limited by the effective diameter of the light beam. This has the advantage that the deviation of the optical axis can be remarkably reduced as compared with the conventional light beam transmission adjusting means in which the transmissive element 101 and the transmissive element 102 are integrally formed.

  As described above, according to the optical disk apparatus 10 of the present embodiment, the light beam transmission adjusting unit can reduce the thickness of the transmission element, and therefore transmission caused by refraction when the incident angle deviation of the light beam occurs. The deviation of the optical axis afterwards can be reduced. As a result, it is possible to improve device reliability and reduce manufacturing costs.

  In this embodiment, the optical 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, two transmissive elements with different light transmittances are switched. Thus, the optical power of the light beam may be switched. In the light beam transmission adjusting means, the light power of the light beam is switched by switching two transmission elements having different light transmittances. However, a plurality of transmission elements having different light transmittances are arranged in parallel to the rotation axis. Thus, the optical power of the light beam may be switched. Thereby, it is possible to switch to a multi-stage optical power according to the number of transmissive elements.

  In the present embodiment, the light beam is a semiconductor laser that emits blue light. However, it may be a semiconductor laser that emits light in the wavelength region from green to ultraviolet.

  In this embodiment, the light beam transmission adjusting unit switches the light power of the light beam between the case where the information recording medium has one recording layer and the case where the information recording medium has two recording layers. If the optical disc apparatus 10 can write and / or read data on an information recording medium having multiple recording layers, the optical power of the light beam may be switched according to the number of recording layers of the optical disc. In this embodiment, the light beam transmission adjusting means switches the light power of the light beam between the case where the information recording medium has one recording layer and the case where the information recording medium has two recording layers. However, the optical power of the light beam may be switched between reading data and writing data.

  The collimating lens 3 and the objective lens 5 of the optical disc apparatus 10 are an example of a condensing unit. Further, the signal processing circuit 12 and the servo control circuit 13 of the optical disk apparatus 10 can be realized as an optical disk controller separate from the optical pickup apparatus 11 in the form of a single circuit or chip. Alternatively, the signal processing circuit 12 and the servo control circuit 13 may be provided in the optical pickup device 11. At that time, the signal processing circuit 12 and the servo control circuit 13 are components of the optical head.

  The optical disk 14 is an example of an information recording medium, and may be a card or the like that can optically read and write data.

  According to the present invention, there is provided an optical pickup device that can suppress the deviation of the optical axis caused by the light beam transmission adjusting means to be small and can realize improvement in device reliability, reduction in manufacturing cost, and the like, and such an optical pickup device. An information processing apparatus can be obtained.

2 is a diagram showing a functional block configuration of an optical disc device 10. FIG. (A) is a perspective view when the light beam 20 passes through the optical filter of the light beam transmission adjusting unit 100, and (b) is a view when the light beam 20 does not pass through the optical filter of the light beam transmission adjusting unit 100. It is a perspective view. (A) is a figure which shows a state when the incident angle shift | offset | difference of the light beam to the 1st transmission element 101 of the light beam permeation | transmission adjustment means 100 does not exist, (b) is incident of the light beam to the transmission element 101. It is a figure which shows the state of the shift | offset | difference of an optical axis when the angle shift | offset | difference exists. It is a figure which shows the structure of the conventional optical pick-up apparatus. (A) is a perspective view when the light beam passes through the optical filter of the light beam transmission adjusting unit 200, and (b) is a perspective view when the light beam does not pass through the optical filter of the light beam transmission adjusting unit 200. It is. (A) is a figure which shows a state when there is no deviation of the incident angle of the light beam to the transmissive element 201 of the light beam transmission adjusting means 200, and (b) is a deviation of the incident angle of the light beam to the transmissive element 201. It is a figure which shows the state of the shift | offset | difference of an optical axis when there exists.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Light source 2 Beam splitter 3 Collimating lens 4 Mirror 5 Objective lens 6 Actuator coil 7 Multi lens 8 Photodiode 10 Optical disk apparatus 11 Optical pick-up apparatus 12 Signal processing circuit 13 Servo control circuit 14 Optical disk 100 Optical beam transmission adjustment means 101 1st transmission Element 101a Optical filter 102 Second transmission element 103 Rotating shaft 104 Support means 105 Rotation driving means

Claims (7)

A light source that emits a light beam having a predetermined optical power;
A light beam transmission adjusting means for adjusting a transmission amount of the light beam;
A light pickup device having a light collecting means for condensing the light beam transmitted through the light beam transmission adjusting means on an information recording medium,
The light beam transmission adjusting means includes:
A first transmissive element having a first transmittance;
A second transmissive element having a second transmittance higher than the first transmittance;
Support means for rotatably supporting the first transmissive element and the second transmissive element around a rotation axis parallel to the first transmissive element and the second transmissive element;
A rotation driving means for rotating the first transmission element and the second transmission element around the rotation axis;
By rotating the rotation driving means to switch between a first position where the light beam is transmitted through the first transmission element and a second position where the light beam is transmitted through the second transmission element, the predetermined optical power is changed. An optical pickup device that selectively outputs a light beam having a smaller first optical power and a light beam having a second optical power that is larger than the first optical power and less than or equal to the predetermined optical power.   The transmission distance when the light beam passes through the first transmission element is shorter than the length of each side constituting the surface of the second transmission element, and the light beam passes through the second transmission element. The optical pickup device according to claim 1, wherein a transmission distance is shorter than a length of each side constituting a surface of the first transmission element.   2. The light according to claim 1, wherein a transmission distance when the light beam passes through the first transmissive element or the second transmissive element is shorter than a length of a side constituting an incident surface of one of the transmissive elements. Pickup device.   4. The optical pickup device according to claim 1, wherein the light source is a semiconductor laser that emits light in a wavelength region from green to ultraviolet. 5.   4. The optical pickup device according to claim 1, wherein the light source is a semiconductor laser that emits light in a blue wavelength region. 5. The optical pickup device according to claim 1, further comprising a photodetector that detects reflected light from the information recording medium, and
An information processing apparatus comprising a signal processing circuit that generates at least one of a reproduction signal and a servo signal based on the detected reflected light. A plurality of types of information recording media having different numbers of recording layers can be loaded, and a light beam having a light power corresponding to the number of the recording layers is radiated to the loaded information recording medium. An information processing apparatus for reading and / or writing data,
When an information recording medium having one recording layer is loaded, a light beam having the first optical power with respect to the recording layer is switched to the first position by rotating the rotation driving means. Radiate
When an information recording medium having a plurality of recording layers is loaded, the rotational driving means is rotated to switch to the second position, and the second optical power is applied to one of the recording layers. The information processing apparatus according to claim 6, which emits a light beam.