JP2008198253A - Optical pickup head and information recording/reproducing device equipped with the same, and information recording/reproducing method, program - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To quickly and highly accurately discriminate a recording layer on which the converged beam of an optical pickup head is focused in recording/reproducing of a multilayer optical disk. <P>SOLUTION: A diffraction optical element 3 divides a light from a light source 1 to generate optical beams corresponding to at least the number of information recording layers of an optical disk 7 so that the interval of optical beams in an optical axis direction is the same as the information recording layer interval of the optical disk 7, and light receiving components 12a and 12b individually receive the return lights of optical beams. Then, based on received light levels detected by the light receiving components 9, 12a and 12b, the information recording layer on which a main beam is focused is discriminated. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a pickup head for an optical disc recording / reproducing apparatus, an optical disc recording / reproducing apparatus, and an optical disc recording / reproducing method, which record and reproduce information using a minute light beam, and particularly records and reproduces information on a multilayer optical disc. The present invention relates to a pickup head for an optical disc recording / reproducing apparatus, an optical disc recording / reproducing apparatus, and an optical disc recording / reproducing method which are necessary when executing the above.

  It has become possible to easily receive high-quality video even in ordinary households, such as digital high-definition broadcasting and video distribution through broadband communication. Accordingly, there is an increasing demand for high-capacity optical disks capable of recording high-quality video data without impairing the image quality.

  Therefore, an information recording / reproducing apparatus for next-generation optical discs that uses a blue semiconductor laser with a short wavelength and an objective lens with a large numerical aperture to record / reproduce information on a large-capacity optical disc such as a Blu-ray disc or HDDVD is used. ing. On the other hand, optical discs having two information recording layers to increase the storage capacity are also used, and the information recording layers of these optical discs are expected to be multilayered.

  In a recording / reproducing apparatus for a multilayer optical disk, the optical pickup head is focused for the purpose of confirming the coincidence between the target layer and the layer actually pulled in by the focus servo, or realizing a fast and reliable interlayer jump. It is necessary to determine how many recording layers the beam is focusing on.

  Conventionally, for a two-layer disc, the layer is determined based on the presence or absence of lead-in information recorded only on the first layer. In this conventional method, the presence or absence of lead-in information is read by moving the focused beam to a region where lead-in information may exist while the focus servo is applied.

  Another discrimination method is disclosed in Patent Document 1. In the method disclosed in Patent Document 1, a spherical aberration signal is detected from the converging position shift between the central portion and the peripheral portion of a reflected light beam from an optical disc, and the spherical aberration is compared with a value stored in a memory in advance. Thus, the layer on which the focused beam is focused was determined.

JP 2004-171635 A

  However, in the conventional method of reading the presence / absence of the lead-in information on the optical disk, every time an interlayer jump is performed, the focused beam moves to an area where the lead-in information is supposed to exist, Since reading and then removing the track servo and returning to the recording / reproducing area to start recording / reproducing, there is a disadvantage that it takes time to start recording / reproducing. Further, since read-in information is read in a state where spherical aberration or the like is not optimized, there is a possibility of an information reading error.

  Further, in the method disclosed in Patent Document 1, the spherical aberration includes not only the difference in the layer on which the focused beam is focused, but also the change in the cover layer thickness of the optical disc, the positional deviation of the optical element of the optical pickup head, etc. When this occurs due to another factor, there is an inconvenience that the layer is erroneously identified.

  Therefore, the present invention improves the above-mentioned disadvantages of the prior art, and in recording and reproduction of a multilayer optical disc, the number of recording layers on which the focused beam of the optical pickup head is focused can be determined quickly, and It is an object of the present invention to provide an information recording / reproducing apparatus that discriminates with high accuracy, an optical pickup head for the information recording / reproducing apparatus, an information recording / reproducing method, and an information recording / reproducing program.

  In order to achieve the above object, an optical pickup head of the present invention includes a light source and an objective lens that collects light from the light source and irradiates an optical information recording medium having a plurality of information recording layers. Beam dividing means for dividing light from the light source to generate at least the same number of light beams as the information recording layer of the optical information recording medium and outputting it as one main beam and a plurality of sub beams, and each reflected by the optical information recording medium A plurality of light receiving units for individually receiving the return light of the light beam, and the beam splitting means includes a plurality of light beams so that an interval in the optical axis direction by the focal point coincides with an information recording layer interval of the optical information recording medium. It is characterized by generating a beam.

  According to such an optical pickup head, a plurality of light beams are generated so that the interval in the optical axis direction by the condensing point coincides with the information recording layer interval of the optical information recording medium, and the respective light beams are condensed. Since the return light is individually detected by irradiating the optical information recording medium, a plurality of return lights can be detected simultaneously, and various signals can be quickly obtained from the detection results. In addition, since the distance in the optical axis direction by the focal point coincides with the information recording layer distance, by indicating which light beam is focused on the information recording layer, the distance between the optical information recording medium and the objective lens The positional relationship can be shown.

  Further, in the optical pickup head described above, each of the light receiving units described above may be disposed at a position conjugate with a focusing point of the corresponding beam light by the objective lens. In this way, it is possible to accurately receive the return lights of a plurality of light beams in which the distance in the optical axis direction due to the focal point coincides with the information recording layer distance.

  In the optical pickup head described above, the beam splitting means described above splits the light from the light source into 0th order light and ± nth order diffracted light (n is a natural number), the 0th order light is the main beam, and the ± nth order diffracted light is the subbeam. The diffractive optical element may be output as In this way, a plurality of light beams can be generated from the light from the light source.

  In the optical pickup head described above, the diffractive optical element serving as the beam splitting unit may have a shape corresponding to a part of a region off the center of the Fresnel lens. In this way, parallel light can be split into parallel light, divergent light, and convergent light, and these lights have different focal points in the optical axis direction depending on the degree of divergence and convergence. By adjusting the shape, the distance in the optical axis direction by the focal point and the information recording layer distance can be matched.

  The information recording / reproducing apparatus of the present invention is based on the above-described optical pickup head and the number of information recording layers at which the condensing point of the main beam is located based on the light receiving level at each light receiving portion of the optical pickup head. And a layer discriminating unit for discriminating between them.

  According to such an information recording / reproducing apparatus, the focus position of the main beam can be determined depending on which sub-beam focus is positioned on the recording layer, and when the main beam focus is positioned on the recording layer, It is possible to determine the number of information recording layers where the light spot is located. Furthermore, since the return light of the main beam and the sub beam is received simultaneously, the main beam is focused on the recording layer for recording and reproduction of information, and at the same time, the information recording layer at which the focus position of the main beam is located. Since it can be determined, the time until recording or reproduction of information can be shortened.

  In the information recording / reproducing apparatus, the layer discriminating unit described above individually determines whether or not the light receiving level in the light receiving unit is greater than a preset threshold value, and based on the determination result, the condensing point of the main beam May be determined in which information recording layer. In this way, since the light reception level is determined to be “high” or “low” based on whether or not the light reception level in the light receiving unit is greater than a preset threshold value, layer determination can be performed digitally.

  In the information recording / reproducing apparatus, the beam splitting unit described above generates two sub-beams, and the layer discriminating unit calculates a difference in received light levels in the respective light-receiving units corresponding to the two sub-beams. Based on the value, the number of information recording layers in which the condensing point of the main beam is located may be determined.

  In this way, a noise component common to each light receiving level can be removed, and more accurate layer discrimination becomes possible.

  In the information recording / reproducing apparatus, the beam splitting unit described above outputs ± n-order diffracted light (n is a natural number) as a sub-beam, and the layer discriminating unit in each light-receiving unit corresponding to the sub-beam of + n-order diffracted light. Calculate the difference between the sum of all received light levels and the sum of received light levels at each light receiving unit corresponding to the sub-beams of the −nth order diffracted light, and based on the calculated value, the number of layers in which the focal point of the main beam is recorded You may make it discriminate | determine whether it is located in the layer.

  In this way, a noise component common to each light receiving level can be removed, and more accurate layer discrimination becomes possible.

  Next, the information recording / reproducing method of the present invention is an information recording / reproducing method for performing information recording / reproducing on the optical information recording medium by condensing and irradiating an information recording layer of the optical information recording medium with a light beam. A beam splitting step of splitting light from the light source to generate at least the same number of light beams as the information recording layer of the optical information recording medium and outputting it as one main beam and a plurality of sub beams, and the plurality of light beams by an objective lens A beam condensing step for drawing the condensing point into the optical information recording medium, a return light detecting step for individually receiving the return light of each light beam reflected by the optical information recording medium, and reception of the return light of each light beam And a layer discriminating step for discriminating on which information recording layer the main beam condensing point is located based on the level. In the beam splitting step, the condensing point of each light beam is provided. Interval in the optical axis direction due to and generating a plurality of light beams to coincide with the information recording layer interval of the optical information recording medium.

  In the information recording / reproducing method described above, in the layer determining step described above, it is individually determined whether or not the received light level of the return light of each sub beam is greater than a preset threshold value, and the main beam is determined based on each determination result. The number of the information recording layers may be determined.

  In the information recording / reproducing method described above, in the beam splitting step described above, two sub-beams are generated, and in the layer discrimination step, the difference between the received light levels of the return light of the two sub-beams is calculated, and based on the calculated value. You may make it discriminate | determine how many information recording layers the condensing point of a main beam is located.

  In the above information recording / reproducing method, in the beam splitting step described above, the diffractive optical element splits the light from the light source into 0th-order light and ± nth-order diffracted light (n is a natural number) and converts the 0th-order light into the main beam, ± n-order diffracted light is output as a sub-beam, and in the layer discrimination step, the difference between the sum of the light-receiving levels of the sub-beams of the + n-order diffracted light and the sum of the light-receiving levels of the sub-beams of the −n-order diffracted light is calculated Then, based on the calculated value, the number of information recording layers where the condensing point of the main beam is located may be determined.

  According to such an information recording / reproducing method, as in the information recording / reproducing apparatus described above, the focus position of the main beam can be determined depending on which sub-beam focus is located on the recording layer. , It is possible to determine the number of information recording layers where the condensing point is located. Furthermore, since the return light of the main beam and the sub beam is received simultaneously, the main beam is focused on the recording layer for recording and reproduction of information, and at the same time, the information recording layer at which the focus position of the main beam is located. Since it can be determined, the time until recording or reproduction of information can be shortened.

  Next, an information recording / reproducing program according to the present invention divides light from a light source, an objective lens that condenses light from the light source onto an optical information recording medium having a plurality of information recording layers, and light from the light source. Beam splitting means for generating at least the same number of light beams as the information recording layer of the optical information recording medium and outputting it as one main beam and a plurality of sub beams, and the return light of each light beam reflected by the optical information recording medium individually An information recording / reproducing apparatus having an optical pickup head having a plurality of light receiving parts for receiving light, wherein a light receiving level input process for inputting a light receiving level value of return light of each sub beam in the light receiving part, and each light receiving level value And a layer discriminating process for discriminating on which information recording layer the main beam condensing point is located.

  Further, in the information recording / reproducing program, the above-described layer determination process individually determines whether each light reception level value input by the light reception level input process is larger than a preset threshold value, and based on this determination result. Thus, the content may be specified so as to determine the number of information recording layers at which the condensing point of the main beam is located.

  Further, in the above information recording / reproducing program, when the beam splitting unit described above generates two sub beams, the layer discriminating process performs the light receiving level value of the return light of the two sub beams input by the light receiving level input process. The content may be specified so as to determine the number of information recording layers in which the condensing point of the main beam is located based on the calculated value.

  In the information recording / reproducing program, the beam splitting unit described above splits the light from the light source into 0th order light and ± nth order diffracted light (n is a natural number), and the 0th order light is the main beam, ± nth order diffracted light. In the case of a diffractive optical element that outputs a sub-beam as a sub-beam, the layer discriminating process performs a difference between the sum of the light-receiving level values of the return light of the sub-beam of + n-order diffracted light and the sum of the light-receiving level values of the return light of the sub-beam of -n-order diffracted light May be specified, and based on the calculated value, the number of information recording layers where the condensing point of the main beam is located may be specified.

  According to such an information recording / reproducing program, as in the information recording / reproducing apparatus described above, the focus position of the main beam can be determined depending on which sub-beam focus is located on the recording layer, and the main beam focus is recorded. In the case of being located in a layer, it is possible to determine the number of information recording layers in which the condensing point is located. Furthermore, since the return light of the main beam and the sub beam is received simultaneously, the main beam is focused on the recording layer for recording and reproduction of information, and at the same time, the information recording layer at which the focus position of the main beam is located. Since it can be determined, the time until recording or reproduction of information can be shortened.

  Since the present invention is configured and functions as described above, it is possible to quickly and accurately determine the number of the recording layer focused by the focused beam of the optical pickup head in the recording / reproducing of the multilayer optical disc. In addition, it is possible to determine the layer with high accuracy without being influenced by the spherical aberration caused by the error of the cover layer thickness.

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings. The information recording / reproducing method of the present invention will be described by showing each step.

  FIG. 1 is a diagram showing a configuration of an optical system of an optical pickup head 100 according to the first embodiment of the present invention.

  The optical system of the optical pickup head 100 according to the first embodiment includes a light source 1, a collimator lens 2 that collimates light emitted from the light source 1, and beam splitting that splits the parallel light to generate a plurality of light beams. A diffractive optical element 3 as a means, a polarizing beam splitter 4 for splitting a light beam, a quarter-wave plate 5, and an objective for condensing each light beam generated by the diffractive optical element 3 and irradiating the optical disk 7. Lens 6, half mirrors 11a and 11b that divide the light beam in two directions, re-condensing lenses 8a, 8b, and 8c that collect the return light of each light beam from optical disk 7, and astigmatism in the light beam A parallel plate 10 for generating astigmatism, an error signal / reproduction signal detecting light receiving component 9 and a layer discrimination signal detecting light receiving component 12a, 12b for receiving the return light of each condensed light beam. Have .

  Here, it is assumed that the objective lens 6 is mounted on a lens driving actuator (not shown). The optical disc 7 has three recording layers.

  The emitted light from the light source 1 is collimated by the collimator lens 2 and is divided into three light beams of 0th order light and ± 1st order diffracted light by the diffractive optical element 3 <Beam Splitting Step>. These light beams are incident on the polarization beam splitter 4 as P-polarized light, and almost 100% are transmitted. The light beams are transmitted through the quarter-wave plate 5 and converted from linearly polarized light to circularly polarized light. Focused <beam focusing step>.

  The reflected light from the optical disk 7 is transmitted in the reverse direction through the objective lens 6, is transmitted through the quarter-wave plate 5, is converted from circularly polarized light to linearly polarized light whose outgoing path and polarization direction are orthogonal, and is transmitted to the polarizing beam splitter 4 by S. Nearly 100% is incident as polarized light and reflected in the direction of the half mirror 11a.

  FIG. 2 is a diagram showing the shape of the diffractive optical element 3 in the first embodiment. As shown in FIG. 2, the diffractive optical element 3 has a shape obtained by cutting a part of a Fresnel lens (phase type Fresnel zone plate). A fine arc-shaped pitch is engraved on the diffractive optical element 3, and the pitch width gradually increases toward the center of the arc. Each pitch has a peak portion and a valley portion, and the ratio of the width of the peak portion is equal to the ratio of the width of the valley portion. Here, the tangential direction shown in the figure is a direction parallel to the track of the portion of the optical disc 7 where light is collected, and the radial direction is a direction perpendicular to the track of the optical disc 7. .

  FIG. 3 is a diagram showing light diffraction by the diffractive optical element 3 in the first embodiment. According to a known diffraction theory, light incident on the Fresnel lens is divided into a divergence + 1st order diffracted light, a converged −1st order diffracted light, and a 0th order light that is not affected by diffraction. Further, by cutting out a part of this Fresnel lens and applying an eccentricity as shown in FIG. 2, coma aberration is added to the diffracted light, and the divergent + 1st order diffracted light converges in the left direction of FIG. The next diffracted light propagates in the right direction of FIG.

  As a result, as shown in FIG. 3, the light incident on the diffractive optical element 3 propagates in parallel without being affected by the diffraction, the sub beam 23a of the + 1st order diffracted light that diverges, and the sub beam 23b of the -1st order diffracted light that converges. Is divided into a main beam 22 of zero-order light.

  FIG. 4 is a diagram showing the positions of the condensing points of the main beam 22 and the sub beams 23a and 23b in the first embodiment.

  Since the sub beam 23a diverges and enters the objective lens 6, the sub beam 23a is condensed at a position far from the objective lens 6 with respect to the condensing point position of the main beam 22. On the other hand, since the sub beam 23 b converges and enters the objective lens 6, the sub beam 23 b is condensed at a position close to the objective lens 6 with respect to the condensing point position of the main beam 22.

  Therefore, as shown in FIG. 4, the grating pattern of the diffractive optical element 3 is set so that the distance in the optical axis direction by the condensing points of the sub beams 23a and 23b and the main beam 22 coincides with the information recording layer distance of the optical disc 7. To do. That is, the amount of deviation in the optical axis direction between the condensing point positions of the sub beams 23a and 23b and the condensing point position of the main beam 22 is set to be the distance d. As a result, for example, when the main beam 22 is focused on the second layer 14 of the optical disc 7, the sub beam 23 a is focused on the third layer 15, and the sub beam 23 b is focused on the first layer 13.

  The return light from the optical disk 7 passes through the objective lens 6 and is guided by the polarization beam splitter 4 and the quarter wavelength plate 5 toward the error signal / reproduced signal detecting light receiving component 9. This return light is divided into two by the half mirror 11a.

  FIG. 5 is a diagram showing the configuration of the error signal / reproduction signal detecting light receiving component 9 in the first embodiment. The error signal / reproduced signal detecting light receiving component 9 includes light receiving portions 38a to 38d so as to divide the light receiving portion into four parts.

  Since the minimum confusion circle position of the main beam 22 by the re-condensing lens 8c and the astigmatism generating parallel plate 10 is shifted from the minimum confusion circle position of the sub beams 23a and 23b in the in-plane direction perpendicular to the optical axis direction. The light receiving portions 38a to 38d are disposed at the minimum confusion circle positions of the main beam 22 by the re-condensing lens 8c and the astigmatism generating parallel plate 10, and the combined size of the light receiving portions 38a to 38d is the minimum confusion of the main beam 22. It should be the same size as the beam spot size at the circle position. As a result, only the main beam 22 enters the light receiving portions 38a to 38d and is received <return light detection step>.

  Since the main beam 22 incident on the light receiving portions 38a to 38d is given astigmatism by the astigmatism generating parallel plate 10, the beam spot size is changed by the position fluctuation in the optical axis direction of the optical disc 7 as shown in FIG. Is distorted in the X1 or X2 direction. Assuming that the levels of electrical signals obtained by photoelectrically receiving and receiving light by the light receiving portions 38a to 38d are V38a to V38d, the focus error signal is detected by {(V38a + V38c) − (V38b + V38d)} by a known astigmatism method. The track error signal is detected by {(V38a + V38b) − (V38c + V38d)} by a known push-pull method. The focus error signal and the track error signal are output to a subsequent servo circuit (not shown), and an actuator equipped with the objective lens 6 drives and controls the objective lens 6 in the focus and track directions. The reproduction signal is detected by (V38a + V38b + V38c + V38d).

  On the other hand, the light beam reflected by the half mirror 11a is further divided into two by the half mirror 11b, partly in the direction of the layer discrimination signal detecting light receiving component 12a and the rest of the layer discrimination signal detecting light receiving component 12b. Each direction is led.

  The layer discrimination signal detecting light receiving component 12a includes a light receiving portion 26a, and the layer determination signal detecting light receiving component 12b includes a light receiving portion 26b. The light receiving portion 26a of the layer discrimination signal detecting light receiving component 12a is disposed close to Δf to the re-condensing lens 8a with respect to the condensing point position when the main beam 22 which is parallel light enters the re-condensing lens 8a. Then, the light receiving part 26b of the layer discrimination signal detecting light receiving component 12b is moved away from the re-condensing lens 8b by Δf with respect to the condensing point position when the main beam 22 which is parallel light enters the re-condensing lens 8b. Arrange.

  Δf is expressed as follows, where fc is the focal length of the re-condensing lenses 8a and 8b, fo is the focal length of the objective lens 6, d is the distance between the information recording layers of the optical disc 7, and n is the refractive index between the recording layers of the optical disc 7. Set to the value indicated by.

  For example, in the case of a two-layer Blu-ray disc or HDDVD, the recording layer spacing is about 20 μm, the refractive index between the recording layers is 2.0, the focal length of the objective lens is 3 mm, and the focal length of the re-condensing lens is 30 mm. Then, from [Equation 1], Δf = 1.0 mm.

  Further, the condensing point position of the main beam 22 by the re-condensing lenses 8a and 8b and the condensing point positions of the sub beams 23a and 23b by the re-condensing lenses 8a and 8b are in an in-plane direction perpendicular to the optical axis direction. It is out of place. Therefore, the light receiving part 26a is arranged in accordance with the condensing point position of the sub beam 23a by the recondensing lens 8a, and the light receiving part 26b is arranged in alignment with the condensing point position of the sub beam 23b by the recondensing lens 8b. The size of 26a is set to be approximately the same as the beam spot size at the condensing point of the sub beam 23a by the re-condensing lens 8a, and the size of the light receiving unit 26b is set to the beam spot size at the condensing point of the sub beam 23b by the re-condensing lens 8b. To the same level.

  By doing in this way, the light receiving parts 26a and 26b are respectively arranged at positions conjugate to the condensing points of the sub beam 23a and the sub beam 23b by the objective lens 6. Then, only the sub-beam 23a is incident on the light-receiving unit 26a and only the sub-beam 23b is incident on the light-receiving unit 26b and is received <return light detection step>.

  FIG. 6 is a diagram showing a configuration of the information reproducing / recording apparatus of the first embodiment.

  As shown in FIG. 6, the information reproducing / recording apparatus according to the first embodiment has the light receiving levels in the optical pickup head 100, the amplifier circuits 51a and 51b, and the light receiving units 26a and 26b of the optical pickup head 100 shown in FIG. A layer discriminating unit 19 for discriminating on which information recording layer the main beam condensing point is located.

  The sub-beams 23a and 23b are received by the light-receiving portions 26a and 26b provided in the light-receiving components 12a and 12b for detecting the layer discrimination signal of the optical pickup head 100 shown in FIG. 1, and are photoelectrically converted and amplified by the amplifier circuits 51a and 51b. The signal levels are V26a and V26b, respectively. V26a and V26b are sent to the layer discriminating unit 19, and the layer discriminating unit 19 executes a layer discriminating process <layer discriminating step>.

  The processing operation of the layer determination unit 19 in the first embodiment will be described with reference to the drawings.

  FIG. 7 is a diagram showing the positional relationship of the focal points when the focus servo is drawn into the first layer 13 of the optical disc 7 in the first embodiment. As shown in FIG. 7, the main beam 22 is condensed and reflected by the first layer 13, and the sub beam 23 a is condensed and reflected by the second layer 14.

  FIG. 8 is a diagram showing the positional relationship of the condensing points when the focus servo is drawn into the second layer 14 of the optical disc 7 in the first embodiment. As shown in FIG. 8, the main beam 22 is condensed and reflected by the second layer 14, and the sub beam 23 b is condensed and reflected by the first layer 13. Further, the sub beam 23a collects and reflects the third layer 15.

  FIG. 9 is a diagram showing the positional relationship of the focal points when the focus servo is drawn into the third layer 15 of the optical disc 7 in the first embodiment. As shown in FIG. 9, the main beam 22 is condensed and reflected by the third layer 15, and the sub beam 23 b is condensed and reflected by the second layer 14.

  FIG. 10 is a diagram illustrating a focus error signal and changes in V26a and V26b when the objective lens 6 is moved in the optical axis direction in the first embodiment.

  When the condensing point of the main beam 22 is on the first layer 13, as shown in FIG. 7, the condensing point of the sub beam 23a is on the second layer 14, and the light receiving unit 26a is connected to the second layer 14 of the sub beam 23a. Since the reflected light is condensed, V26a increases. On the other hand, since the reflected light of the sub beam 23b is not condensed on the light receiving portion 26b, V26b is low.

  When the condensing point of the main beam 22 is on the second layer 14, as shown in FIG. 8, the condensing point of the sub beam 23a is on the third layer 15, and the condensing point of the sub beam 23b is on the first layer 13. Therefore, the reflected light from the third layer 15 of the sub beam 23a is condensed on the light receiving portion 26a, and the reflected light from the first layer 13 of the sub beam 23b is condensed on the light receiving portion 26b, so that V26a and V26b are Both are expensive.

  Further, when the condensing point of the main beam 22 is on the third layer 15, as shown in FIG. 9, since the reflected light from the second layer 14 of the sub beam 26b is condensed on the light receiving portion 26b, V26b becomes high. . On the other hand, since the reflected light of the sub beam 23a is not condensed on the light receiving part 26a, V23a is low.

  Table 1 shows the relationship between the recording layer where the main beam 22 is focused and the levels of V26a and V26b. It shows that H is a high level and L is a low level.

  In the layer discriminating unit 19 in the first embodiment, as shown in FIG. 10, by setting a certain threshold value and determining whether or not the levels of V26a and V26b exceed the threshold value, H ”and“ L ”are determined, and based on [Table 1], discrimination processing of the recording layer focused by the main beam 22 is executed.

  Here, the information recording apparatus of the first embodiment can discriminate the recording layer that is focused on the optical disc 7 having three recording layers. Discrimination is also possible for an optical disc 7 having a recording layer. Table 2 shows the relationship between the layer where the main beam 22 is focused and the levels of V26a and V26b in the case of a two-layer disc.

  The layer discriminating unit 19 determines “H” and “L” of V26a and V26b based on the threshold value, and executes the discriminating process of the recording layer focused by the main beam 22 based on [Table 2].

  Here, the layer discriminating unit 19 described above may be configured such that the function content is programmed and executed by a computer.

  As described above, according to the first embodiment, since the focused recording layer is discriminated while irradiating the focused beam of the optical pickup head on the recording / reproducing area of the optical disc 7, it is possible to discriminate the recording layer at high speed. In addition, the recording / reproducing start time after the interlayer jump can be shortened. Further, since the layer determination is performed without being affected by the spherical aberration caused by the variation in the cover layer thickness, the layer determination can be performed with high accuracy.

  Next, an information recording / reproducing apparatus according to a second embodiment of the present invention will be described with reference to the drawings.

  FIG. 11 is a diagram showing the configuration of the information recording / reproducing apparatus of the second embodiment. In FIG. 11, the same components as those of the first embodiment shown in FIG.

  As shown in FIG. 11, the information recording / reproducing apparatus of the second embodiment includes a layer discriminating unit 28 instead of the layer discriminating unit 19 in the information recording / reproducing apparatus of the first embodiment shown in FIG. A signal calculation unit 44 is provided.

  The levels of the electrical signals that are received by the light-receiving portions 26a and 26b and received by the sub-beams 23a and 23b and photoelectrically converted and amplified by the amplifier circuits 51a and 51b are V26a and V26b. V26a and V26b are sent to the difference signal calculation unit 44, and (V26a-V26b) is calculated. This (V26a-V26b) is set to V44. V44 output from the difference signal calculation unit 44 is sent to the layer discrimination unit 28, and the layer discrimination unit 28 executes layer discrimination <layer discrimination step>.

  The operation of the layer determination unit 28 in the second embodiment will be described with reference to the drawings. Here, in the second embodiment, when the focus servo is drawn into each layer of the optical disc 7, the positional relationship between the condensing points of the main beam 22 and the sub beams 23a and 23b is the same as in the first embodiment described above. is there.

  FIG. 12 is a diagram showing changes in the focus error signal and the output V44 from the V26a, V26b, and difference signal calculation unit 44 when the objective lens 6 is moved in the optical axis direction in the second embodiment.

  As shown in FIG. 12, when the focal point of the main beam 22 is on the first layer 13, V26a is high and V26b is low, as in the first embodiment described above. Therefore, the difference V44 becomes positive. When the condensing point of the main beam 22 is on the second layer 14, both V26a and V26b are high as in the first embodiment described above. Therefore, the difference V44 becomes zero.

  Furthermore, when the condensing point of the main beam 22 is in the third layer 15, V26a is low and V26b is high, as in the first embodiment. Therefore, the difference V44 becomes negative.

  Here, as in the first embodiment described above, the optical disc 7 may be a two-layer disc. FIG. 13 is a diagram showing changes in the focus error signal and V26a, V26b, and V44 when the objective lens 6 is moved in the optical axis direction in the case of the dual-layer disc in the second embodiment.

  When the optical disc 7 is a double-layer disc, as shown in FIG. 13, when the condensing point of the main beam 22 is on the first layer 13, V26a is high and V26b is low, as in the first embodiment. Therefore, the difference V44 becomes positive. Moreover, when the condensing point of the main beam 22 exists in the 2nd layer 14, V26a is low and V26b is high similarly to 1st Embodiment. Therefore, the difference V44 becomes negative.

  In the layer discriminating unit 28 in the second embodiment, as shown in FIG. 12 or FIG. 13, the output range of V44 corresponding to each layer is set, and the range is compared with V44, whereby the main beam 22 is compared. Performs discrimination of the layer that is focusing.

  Here, the layer discriminating unit 28 described above may be configured such that the function content is programmed and executed by a computer.

  According to the second embodiment as described above, since the layer discrimination is performed while irradiating the focused beam of the optical pickup head on the recording / reproducing area of the optical disc 7, the high-speed layer discrimination and the post-interlayer jump are performed. The time required to start recording / reproduction can be shortened. Further, since the layer is discriminated without being affected by the spherical aberration caused by the variation of the cover layer thickness, the layer can be discriminated with high accuracy. Furthermore, since V44 obtained by subtracting V26b from V26a is used as the layer discrimination signal, the influence of noise components common to V26a and V26b can be removed, and more accurate layer discrimination is possible.

  Next, an information recording / reproducing apparatus according to a third embodiment of the present invention will be described with reference to the drawings. The information recording / reproducing apparatus of the third embodiment is an apparatus that can discriminate the focusing layer even when the number of recording layers of the optical disc is five.

  FIG. 14 is a diagram showing the configuration of the optical system of the optical pickup head 200 in the third embodiment. In FIG. 14, the same components as those in the first embodiment shown in FIG.

  The optical system of the optical pickup head 200 in the third embodiment includes a diffractive optical element 40 instead of the diffractive optical element 3 in the optical system of the optical pickup head 100 in the first or second embodiment shown in FIG. Further, the configuration includes half mirrors 11c and 11d, re-condensing lenses 8c and 8d, and light receiving parts 12c and 12d for detecting a layer discrimination signal.

  The optical disc 18 has five recording layers. The light beam lead from the light source 1 to the optical disc 18 and the return light lead from the optical disc 18 to the error signal / reproduction signal detecting light receiving component 9 are described above. This is the same as in the first embodiment.

  FIG. 15 is a diagram showing the shape of the diffractive optical element 40 in the third embodiment. As shown in FIG. 15, the diffractive optical element 40 has a shape in which a part of a Fresnel lens is cut off. Further, as shown in FIG. 15, the shape of the diffractive optical element 40 is such that a fine pitch of a structure in which a wide mountain and a narrow valley, and a narrow mountain and a wide valley are alternately repeated has an arc shape. It is the shape carved in. Here, in the third embodiment, the ratio of the width between the wide peak or valley and the narrow peak or valley in the diffractive optical element 40 is 1: 0.406. By doing so, the diffraction efficiencies of the + 2nd order diffracted light and the −2nd order diffracted light are equal to the diffraction efficiencies of the + 1st order diffracted light and the −1st order diffracted light.

  FIG. 16 is a diagram showing light diffraction by the diffractive optical element 40 in the third embodiment. The incident parallel light is divided into the main beam 41 and the sub beams 42a to 42d by the diffractive optical element 40 having the shape shown in FIG.

  The sub beam 42 a is + second order diffracted light of the diffractive optical element 40, and the sub beam 42 b is + first order diffracted light of the diffractive optical element 40. The sub beam 42 c is the −1st order diffracted light of the diffractive optical element 40, and the sub beam 42 d is the −2nd order diffracted light of the diffractive optical element 40. The sub beams 42a and 42b are divergent light, and the degree of the divergence is larger in the sub beam 42a. The sub-beams 42c and 42d are convergent light, and the degree of convergence is greater in the sub-beam 42d. The 0th-order light of the diffractive optical element 40 is the main beam 41, which is parallel light.

  FIG. 17 is a diagram illustrating the positions of the condensing points of the main beam 41 and the sub beams 42a to 42d in the third embodiment.

  Since the sub beams 42 a and 42 diverge and enter the objective lens 6, the sub beams 42 a and 42 are condensed at a position far from the objective lens 6 with respect to the focal point position of the main beam 41. Since the degree of divergence is larger in the sub beam 42a than in the sub beam 42b, the sub beam 42a is condensed at a position farther from the condensing point position of the main beam 41 than the sub beam 42b.

  On the other hand, since the sub beams 42c and 42d converge and enter the objective lens 6, the sub beams 42c and 42d are condensed at a position close to the objective lens 6 with respect to the focal point position of the main beam 41. Since the degree of convergence is greater in the sub beam 42d than in the sub beam 42c, the sub beam 42d is condensed at a position farther from the focal point position of the main beam 41 than the sub beam 42c.

  Therefore, the grating pattern of the diffractive optical element 40 is set so that the interval in the optical axis direction of the condensing points of the main beam 41 and the sub beams 42a to 42d coincides with the information recording layer interval of the optical disc 18, as shown in FIG. To do. That is, the difference in the optical axis direction between the condensing point position of the sub beam 42b and the sub beam 42c and the condensing point position of the main beam 41 becomes the distance d of the information recording layer of the optical disc 18 and the sub beam 42a and the sub beam 42d. The difference in the optical axis direction between the condensing point position and the condensing point position of the main beam 41 is set to be twice the distance d between the information recording layers of the optical disc 18. As a result, for example, when the main beam 41 is focused on the third layer 15 of the optical disc 18, the sub beam 42a is on the fifth layer 17, the sub beam 42b is on the fourth layer 16, the sub beam 42c is on the second layer 14, and the sub beam. 42d condenses on the first layer 13, respectively.

  Here, the error signal / reproduction signal detecting light receiving component 9 and the error signal / reproduction signal detection operation in the third embodiment are the same as those in the first embodiment.

  Further, the light beam reflected by the half mirror 11a is divided into four by the half mirrors 11b to 11d and guided to the direction of the light receiving components 12a to 12d for detecting the layer discrimination signal. The light receiving part 26a for the layer discrimination signal detecting light receiving part 12a, the light receiving part 26b for the light receiving part 12b for detecting the layer discrimination signal, and the light receiving part 26c for the light receiving part 12c for detecting the layer discrimination signal, for detecting the layer discrimination signal. A light receiving part 26d is installed in each of the light receiving parts 12d.

  The light receiving unit 26a is disposed 2Δf closer to the re-condensing lens 8a side with respect to the condensing point position when the main beam 22 which is parallel light is incident on the re-condensing lens 8a, and the light receiving unit 26b is arranged in parallel light. Is placed closer to the re-condensing lens 8b side by Δf with respect to the condensing point position when the light enters the re-condensing lens 8b, and the light receiving portion 26c is collected when parallel light enters the re-condensing lens 8c. It arrange | positions from the light condensing lens 8c away from (DELTA) f. The light receiving unit 26d is disposed at a distance of 2Δf from the re-condensing lens 8d with respect to the condensing point position when the parallel light enters the re-condensing lens 8d.

  Δf is expressed as follows, where fc is the focal length of the re-condensing lenses 8a to 8d, fo is the focal length of the objective lens 6, d is the distance between the information recording layers of the optical disc 18, and n is the refractive index between the layers of the optical disc 18. Set to the value shown in.

  For example, in the case of a two-layer Blu-ray disc or HDDVD, the distance between the information recording layers of the disc is 20 μm, the refractive index between the layers of the optical disc 18 is 2.0, the focal length of the objective lens 6 is 3 mm, and the re-condensing lens 8 If the focal length of the lens is 30 mm, Δf = 1.0 mm.

  Furthermore, the condensing point position of the main beam 41 by the re-condensing lenses 8a to 8d and the condensing point position of the sub-beams 42a to 42d by the re-condensing lenses 8a to 8d are in the in-plane direction perpendicular to the optical axis direction. It's off. Therefore, the light receiving unit 26a is arranged at the condensing point position of the sub-beam 42a by the re-condensing lens 8a, the light receiving unit 26b is arranged at the condensing point position of the sub-beam 42b by the re-condensing lens 8b, and the light receiving unit 26c is arranged at the sub beam 42c. Are arranged at the condensing point position by the re-condensing lens 8c, the light receiving unit 26d is arranged at the condensing point position by the re-condensing lens 8d of the sub beam 42d, and the size of the light receiving unit 26a is set to the re condensing lens 8a of the sub beam 42a. The beam spot size at the condensing point of the sub-beam 42b is set to the same size as the beam spot size at the condensing point by the re-condensing lens 8b of the sub beam 42b, and the size of the light receiving unit 26a is set to the sub beam 42c. The size of the light receiving portion 26d is set to be approximately the same as the beam spot size at the condensing point by the re-condensing lens 8c. To the same extent as the beam spot size at the focal point by the optical lens 8d.

  By doing in this way, light-receiving part 26a-26d is each arrange | positioned in the conjugate position with the condensing point by the objective lens 6 of subbeam 42a-42d. Then, the sub-beam 42a is incident on the light-receiving portion 26a, the sub-beam 42b is incident on the light-receiving portion 26b, the sub-beam 42c is incident on the light-receiving portion 26c, and only the sub-beam 42d is incident on the light-receiving portion 26d.

  FIG. 18 is a diagram showing the configuration of the information recording / reproducing apparatus of the third embodiment. As shown in FIG. 18, the information reproducing / recording apparatus according to the third embodiment includes the optical pickup head 200, amplifier circuits 51a, 51b, 51c, and 51d shown in FIG. .

  The sub beams 42a to 42d are received and photoelectrically converted by the light receiving portions 26a to 26d provided in the light receiving components 12a to 12d for detecting the layer discrimination signals of the optical pickup head 200 shown in FIG. 18, and are amplified by the amplification circuits 51a to 51d. The signal levels are V26a to V26d, respectively. V26a to V26d are sent to the layer discrimination unit 29, and the layer discrimination unit 29 executes a layer discrimination process <layer discrimination step>.

  Next, the processing operation of the layer determining unit 29 in the third embodiment will be described with reference to the drawings.

  FIG. 19 is a diagram showing the positional relationship of the focal points when the focus servo is drawn into the first layer 13 in the third embodiment. As shown in FIG. 19, the main beam 41 is condensed and reflected by the first layer 13. Further, the sub beam 42 b is condensed and reflected by the second layer 14, and the sub beam 42 a is condensed and reflected by the third layer 15.

  FIG. 20 is a diagram showing the positional relationship of the focal points when the focus servo is drawn into the second layer 14 in the third embodiment. As shown in FIG. 20, the main beam 41 is condensed and reflected by the second layer 14. Further, the sub beam 42 c is condensed and reflected by the first layer 13, and the sub beam 42 b is condensed and reflected by the third layer 15. Further, the sub beam 42 a is condensed and reflected by the fourth layer 16.

  FIG. 21 is a diagram showing the positional relationship of the condensing points when the focus servo is drawn into the third layer 15 in the third embodiment. As shown in FIG. 21, the main beam 41 is condensed and reflected by the third layer 15. Further, the sub beam 42d is condensed and reflected by the first layer 13, and the sub beam 42c is condensed and reflected by the second layer 14. Further, the sub beam 42 b is condensed and reflected by the fourth layer 16, and the sub beam 42 a is condensed and reflected by the fifth layer 17.

  FIG. 22 is a diagram showing the positional relationship of the condensing points when the focus servo is drawn into the fourth layer 16 in the third embodiment. As shown in FIG. 22, the main beam 41 is condensed and reflected by the fourth layer 16. Further, the sub beam 42 d is condensed and reflected by the second layer 13, and the sub beam 42 c is condensed and reflected by the third layer 15. Further, the sub beam 42 b is condensed and reflected by the fifth layer 16.

  FIG. 23 is a diagram illustrating the positional relationship of the focal points when the focus servo is drawn into the fifth layer 17 in the third embodiment. As shown in FIG. 23, the main beam 41 is condensed and reflected by the fifth layer 17. Further, the sub beam 42 d is condensed and reflected by the third layer 13, and the sub beam 42 c is condensed and reflected by the fourth layer 15.

  FIG. 24 is a diagram illustrating a focus error signal and changes in V26a to V26d when the objective lens 6 is moved in the optical axis direction in the third embodiment.

  When the main beam 41 is on the first layer 13, the reflected light from the third layer 15 of the sub beam 42a is condensed on the light receiving portion 26a, and V26a becomes high. In addition, the reflected light from the second layer 14 of the sub beam 42b is collected on the light receiving portion 26b, and V26b is increased. V26c and V26d are low because no light is collected on the light receiving portions 26c and 26d.

  When the main beam 41 is in the second layer 14, the reflected light from the fourth layer 16 of the sub beam 42a is condensed on the light receiving portion 26a, and V26a becomes high. In addition, the reflected light from the third layer 15 of the sub beam 42b is collected on the light receiving unit 26b, and V26b is increased. In addition, the reflected light from the first layer 13 of the sub beam 42c is collected on the light receiving unit 26c, and V26c becomes high. V26d is low because no light is collected on the light receiving portion 26d.

  When the main beam 41 is in the third layer 15, the reflected light from the fifth layer 17 of the sub beam 42a is condensed on the light receiving portion 26a, and V26a becomes high. In addition, the reflected light from the fourth layer 16 of the sub beam 42b is collected on the light receiving unit 26b, and V26b is increased. Further, the reflected light from the second layer 14 of the sub beam 42c is condensed on the light receiving unit 26c, and V26c becomes high. Furthermore, the reflected light from the first layer 13 of the sub-beam 42d is collected on the light receiving unit 26d, and V26d is increased.

  When the main beam 41 is on the fourth layer 16, the reflected light from the fifth layer 17 of the sub beam 42b is condensed on the light receiving unit 26b, and V26b becomes high. In addition, the reflected light from the third layer 15 of the sub beam 42c is collected on the light receiving unit 26c, and V26c is increased. Further, the reflected light from the second layer 14 of the sub beam 42d is collected on the light receiving unit 26d, and V26d becomes high. Since no light is collected on the light receiving portion 26a, V26a is low.

  When the main beam 41 is on the fifth layer 17, the reflected light from the fourth layer 16 of the sub beam 42c is condensed on the light receiving unit 26c, and V26c becomes high. In addition, the reflected light from the third layer 15 of the sub beam 42d is collected on the light receiving unit 26d, and V26d is increased. V26a and V26b are low because no light is collected on the light receiving portions 26a and 26b.

  Table 3 shows the relationship between the recording layer where the main beam 41 is focused and the levels of V26a to V26d. H indicates a high level and L indicates a low level.

  Here, in the third embodiment, the optical disk 18 has five layers, but a disk having four layers or less may be used. [Table 4] shows the relationship between the layer with the main beam 41 and the levels of V26a to V26d in the case of a four-layer disc.

  [Table 5] shows the relationship between the layer with the main beam 41 and the levels of V26a to V26d in the case of a three-layer disc.

  [Table 6] shows the relationship between the layer with the main beam 41 and the levels of V26a to V26d in the case of a two-layer disc.

  In the layer discriminating unit 29 in the third embodiment, “H” and “L” of V26a to 26d are determined by setting a certain threshold value and determining whether or not the level of V26a to 26d exceeds the threshold value. Then, based on [Table 1] to [Table 6], the recording layer discrimination process in which the main beam 22 is focused is executed.

  Here, the layer discriminating unit 29 described above may be configured such that the function content is programmed and executed by a computer.

  As described above, according to the third embodiment, since the focused recording layer is discriminated while irradiating the focused beam of the optical pickup head on the recording / reproducing area of the optical disc 7, the high-speed layer discrimination is performed. In addition, the recording / reproducing start time after the interlayer jump can be shortened. Further, since the layer determination is performed without being affected by the spherical aberration caused by the variation in the cover layer thickness, the layer determination can be performed with high accuracy.

  Next, an information recording / reproducing apparatus according to a fourth embodiment of the present invention will be described with reference to the drawings.

  FIG. 25 is a diagram showing the configuration of the information recording / reproducing apparatus of the fourth embodiment. 25, the same code | symbol is attached | subjected to the component similar to 3rd Embodiment shown in FIG.

  The information recording / reproducing apparatus of the fourth embodiment includes a layer discriminating unit 39 instead of the layer discriminating unit 29 of the information recording / reproducing apparatus of the third embodiment shown in FIG. 18, and further includes sum signal calculation units 45a and 45b, And a difference signal calculation unit 46.

  The sub-beams 42a to 42d are received by the light receiving portions 26a to 26d and subjected to photoelectric conversion, and the levels of electric signals amplified by the amplifier circuits 51a to 51d are set to V26a to V26d. Among these, V26a and V26b are sent to the sum signal calculator 45a, (V26a + V26b) is calculated, V26c and V26d are sent to the sum signal calculator 45b, and (V26c + V26d) is calculated. The sum signal calculated in this way is sent to the difference signal calculation unit 46, and {(V26a + V26b) − (V26c + V26d)} is calculated. This difference signal is sent to the layer discriminating unit 39, and the layer discriminating unit 39 executes layer discrimination <layer discrimination step>.

  Next, the processing operation of the layer determination unit 39 in the fourth embodiment will be described with reference to the drawings.

  In the fourth embodiment, the positional relationship between the main beam 41 and the sub beams 42a to 42d when the focus servo is drawn into each layer of the optical disc 18 is the same as in the third embodiment.

  FIG. 26 shows focus error signals and outputs V45a and V45b from the sum signal calculation units 45a to 45b and the difference signal calculation unit 46 when the objective lens 6 is moved in the optical axis direction in the fourth embodiment. It is a figure which shows the change of the output V46.

  When the main beam 41 is in the first layer 13, V26a and V26b are high and V26c and V26d are low, as in the third embodiment. Therefore, V45a is high and V45b is low. The difference V46 is a positive value having a large absolute value.

  When the main beam 41 is on the second layer 14, V26a, V26b, and V26c are high and V26d is low, as in the third embodiment. Therefore, V45a is high and V45b is slightly high. The difference V46 is a positive value having a small absolute value.

  Further, when the main beam 41 is in the third layer 15, V26a, V26b, V26c, and V26d are high as in the third embodiment. Therefore, V45a is high and V45b is also high. The difference V46 is zero.

  When the main beam 41 is on the fourth layer 16, V26a is low and V26b, V26c, and V26d are high, as in the third embodiment. Therefore, V45a is slightly high and V45b is high. The difference V46 is a negative value having a small absolute value.

  When the main beam 41 is on the fifth layer 17, V26a and V26b are low and V26c and V26d are high, as in the third embodiment. Therefore, V45a is low and V45b is high. The difference V46 is a negative value having a large absolute value.

  Here, as in the third embodiment, the optical disc 18 may be a disc having four layers or less. FIG. 27 shows focus error signals and outputs V45a to V45b from the sum signal calculation units 45a to 45b when the objective lens 6 is moved in the optical axis direction in the case of a four-layer disc in the fourth embodiment. FIG. 8 is a diagram showing a change in an output V46 from the difference signal calculation unit 46.

  FIG. 28 shows focus error signals and outputs from the sum signal calculation units 45a to 45b when the objective lens 6 is moved in the optical axis direction in the case of a three-layer disc in the fourth embodiment. It is a figure which shows the change of the output V46 from V45a-V45b and the difference signal calculating part 46. FIG.

  FIG. 29 shows the focus error signal and the output from the sum signal calculation units 45a to 45b when the objective lens 6 is moved in the optical axis direction in the case of the dual-layer disc in the fourth embodiment. It is a figure which shows the change of the output V46 from V45a-V45b and the difference signal calculating part 46. FIG.

  From the above, it is possible to determine the layer on which the main beam 41 is focused. In the layer discriminating unit 39, as shown in FIGS. 26 to 29, an output range corresponding to each layer is set and the range is compared with V46 to discriminate the focusing layer.

  Here, the layer discriminating unit 39 described above may be configured such that the function content is programmed and executed by a computer.

  According to the information recording / reproducing apparatus of the fourth embodiment as described above, the layer is discriminated while irradiating the focused beam of the optical pickup head to the area to be actually recorded / reproduced. It is possible to shorten the time until recording or playback after the interlayer jump is started. Further, since the layer is discriminated without being affected by the spherical aberration caused by the variation of the cover layer thickness, the layer can be discriminated with high accuracy.

  Further, since V46 obtained by subtracting V26c + V26d from V26a + V26b is used as the layer discrimination signal, the influence of the noise component common to (V26a + V26b) and (V26c + V26d) can be removed, and more accurate layer discrimination is possible.

  Here, in the first to fourth embodiments of the optical disc recording / reproducing apparatus of the present invention, the direction of the diffraction grating of the diffractive optical element is set in the direction as shown in FIGS. 2 and 15, but the tangential direction and radial direction are set. The direction may be reversed. Furthermore, the first to fourth embodiments can be applied to an optical disc having six or more layers by increasing the number of sub-beams if the diffraction efficiency of higher-order diffracted light is increased by changing the shape of the diffraction grating of the diffractive optical element. For an optical disc having a maximum of n information recording layers, the number of sub-beams is (n−1), and there are (n−1) light receiving parts for detecting a layer discrimination signal corresponding to the number of sub beams.

  In the first to fourth embodiments, the reflected light from the optical disk is divided by the half mirrors 11a to 11d, the main beam is received by the error signal / reproduction signal detecting light receiving component 9, and the sub beam is a layer corresponding to each. The light receiving parts 12a to 12d for detecting the discrimination signal are received, but not limited thereto, as shown in FIG. 30, the light receiving part 47 for detecting the error signal / reproduced signal / layer discrimination signal without dividing the reflected light from the optical disk. May be configured to receive light at a time. A case where this structure is applied to an optical disc having three recording layers will be described.

  As shown in FIG. 31, the light receiving part of the error signal / reproduction signal / layer discrimination signal detection light receiving part 47 is divided into an error signal / reproduction signal detection part 48 and layer discrimination signal detection parts 49a and 49b. The error signal / reproduction signal detection unit 48 and the layer discrimination signal detection unit 49b are respectively provided with condensing point position correction bodies 50a and 50b made of a transparent body having a refractive index of 1 or more. Due to the refracting action of the condensing point position correctors 50a and 50b, the minimum circle of confusion circle position of the light beam moves in the optical axis direction. Therefore, by adjusting the thickness and the refractive index of the condensing point position correction bodies 50a and 50b, correction is performed so that the minimum circle of confusion in the optical axis direction of each light beam becomes the same.

  Here, in the first to fourth embodiments of the optical disc recording / reproducing apparatus of the present invention, the astigmatism method is used as means for detecting the focus error signal, but another focus error signal such as a knife edge method is used. Detection means may be used.

It is a figure which shows the structure of the optical system of the optical pick-up head in the recording / reproducing apparatus of 1st Embodiment in this invention. It is a figure which shows the shape of the diffractive optical element in embodiment disclosed by FIG. It is a figure which shows the diffraction of the light in the diffractive optical element in embodiment disclosed by FIG. It is a figure which shows the condensing point of each diffracted light in embodiment disclosed by FIG. It is a figure which shows the structure of the light-receiving component for an error signal and reproduction | regeneration signal detection in embodiment disclosed by FIG. It is a figure which shows the structure of the recording / reproducing apparatus of embodiment disclosed by FIG. FIG. 2 is a diagram showing a positional relationship of converging points of diffracted lights when focus servo is drawn into the first layer of the optical disc in the recording / reproducing apparatus of the embodiment disclosed in FIG. 1. FIG. 2 is a diagram showing a positional relationship between converging points of diffracted lights when focus servo is drawn into the second layer of the optical disc in the recording / reproducing apparatus of the embodiment disclosed in FIG. 1. FIG. 4 is a diagram showing a positional relationship between converging points of diffracted lights when focus servo is drawn into the third layer of the optical disc in the recording / reproducing apparatus of the embodiment disclosed in FIG. 1. FIG. 2 is a diagram illustrating changes in a focus error signal and an output signal from a receiving unit when an objective lens is moved in the optical axis direction in the recording / reproducing apparatus according to the embodiment disclosed in FIG. 1. It is a figure which shows the structure of the information recording / reproducing apparatus of 2nd Embodiment in this invention. FIG. 11 is a diagram showing changes in the focus error signal, the output signal from the receiving unit, and the output signal from the difference signal calculating unit when the objective lens is moved in the optical axis direction in the information recording / reproducing apparatus of the embodiment disclosed in FIG. It is. In the information recording / reproducing apparatus of the embodiment disclosed in FIG. 11, when the objective lens is moved in the optical axis direction when the optical disk is a double-layer disk, the focus error signal, the output signal from the receiver, and the difference signal calculator It is a figure which shows the change of the output signal from. It is a figure which shows the structure of the optical system of the optical pick-up head in the recording / reproducing apparatus of 3rd Embodiment in this invention. It is a figure which shows the shape of the diffractive optical element in embodiment disclosed by FIG. It is a figure which shows the diffraction of the light in the diffractive optical element in embodiment disclosed by FIG. It is a figure which shows the condensing point of each diffracted light in embodiment disclosed by FIG. It is a figure which shows the structure of the information recording / reproducing apparatus of embodiment disclosed by FIG. FIG. 15 is a diagram showing a positional relationship between converging points of diffracted lights when the focus servo is drawn into the first layer of the optical disc in the information recording / reproducing apparatus of the embodiment disclosed in FIG. 14. FIG. 15 is a diagram illustrating a positional relationship between converging points of diffracted lights when a focus servo is drawn into the second layer of the optical disc in the information recording / reproducing apparatus according to the embodiment disclosed in FIG. 14. FIG. 15 is a diagram showing a positional relationship between condensing points of diffracted lights when focus servo is drawn into the third layer of the optical disc in the information recording / reproducing apparatus of the embodiment disclosed in FIG. 14. FIG. 15 is a diagram illustrating a positional relationship between converging points of diffracted lights when the focus servo is drawn into the fourth layer of the optical disc in the information recording / reproducing apparatus of the embodiment disclosed in FIG. 14. FIG. 15 is a diagram showing a positional relationship between converging points of diffracted lights when focus servo is drawn into the fifth layer of the optical disc in the information recording / reproducing apparatus of the embodiment disclosed in FIG. 14. FIG. 15 is a diagram illustrating changes in a focus error signal and an output signal from a receiving unit when the objective lens is moved in the optical axis direction in the information recording / reproducing apparatus of the embodiment disclosed in FIG. 14. It is a figure which shows the structure of the recording / reproducing apparatus of 4th Embodiment in this invention. FIG. 26 is a diagram illustrating changes in the focus error signal, the output signal from the sum signal calculation unit, and the output signal from the difference signal calculation unit when the objective lens is moved in the optical axis direction in the embodiment disclosed in FIG. 25. In the embodiment disclosed in FIG. 25, the focus error signal and the output signal from the sum signal calculation unit and the output signal from the difference signal calculation unit when the objective lens in the case of the four-layer disc is moved in the optical axis direction. It is a figure which shows a change. In the embodiment disclosed in FIG. 25, when the objective lens in the case of the three-layer disc is moved in the optical axis direction, the focus error signal, the output signal from the sum signal calculation unit, the output signal from the difference signal calculation unit It is a figure which shows the change of. In the embodiment disclosed in FIG. 25, when the objective lens in the case of the double-layer disc is moved in the optical axis direction, the focus error signal, the output signal from the sum signal calculation unit, and the output signal from the difference signal calculation unit It is a figure which shows the change of. It is a figure which shows another example of a structure of the optical system of the optical pick-up head in any one of the 1st thru | or 4th embodiment in this invention. FIG. 31 is a diagram illustrating a configuration of a light receiving component for detecting an error signal, a reproduction signal, and a layer discrimination signal in the embodiment disclosed in FIG. 30.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Light source 2 Collimator lens 3 Diffractive optical element 4 Polarization beam splitter 5 1/4 wavelength plate 6 Objective lens 7, 18 Optical disk 8a, 8b, 8c, 8d, 8e, 8f Re-condensing lens 9 Light reception for error signal / reproduction signal detection Component 10 Parallel plate for generating astigmatism 11a, 11b, 11c, 11d Half mirror 12a, 12b, 12c, 12d Light receiving component for detecting layer discrimination signal 13 1st layer 14 2nd layer 15 3rd layer 16 4th layer 17 4th layer 5 layers 19, 28, 29, 39 Layer discriminating unit 22 Main beam 23a, 23b Sub beam 26a, 26b, 26c, 26d Light receiving unit 38a, 38b, 38c, 38d Light receiving unit 40 Diffractive optical element 41 Main beam 42a, 42b, 42c, 42d Sub beam 44 Difference signal calculation unit 45a, 45b Sum signal calculation unit 46 Difference signal calculation unit 7 Light-receiving part for detecting error signal / reproduction signal / layer discrimination signal 48 Error signal / reproduction signal detection unit 49a, 49b Layer discrimination signal detection unit 50a, 50b Condensing point position corrector 51a, 51b, 51c, 51d Amplifying circuit 100, 200,300 Optical pickup head

Claims (16)

A light source and an objective lens that condenses light from the light source and irradiates the optical information recording medium having a plurality of information recording layers,
Beam splitting means for splitting light from the light source to generate at least the same number of light beams as the information recording layer of the optical information recording medium and outputting it as one main beam and a plurality of sub beams, and reflecting by the optical information recording medium A plurality of light receiving units for individually receiving the return light of each of the light beams,
The beam splitting unit generates the plurality of light beams such that an interval in an optical axis direction by a condensing point thereof coincides with an information recording layer interval of the optical information recording medium. . The optical pickup head according to claim 1,
An optical pickup head, wherein each of the light receiving portions is arranged at a position conjugate with a condensing point of the corresponding beam light by the objective lens. In the optical pickup head according to claim 1 or 2,
The beam splitting means is a diffractive optical element that splits light from a light source into 0th order light and ± nth order diffracted light (n is a natural number) and outputs the 0th order light as a main beam and the ± nth order diffracted light as a subbeam. An optical pickup head characterized by that. In the optical pickup head according to claim 3,
An optical pickup head, wherein the diffractive optical element as the beam splitting means has a shape corresponding to a part of a region off the center of the Fresnel lens. In an information recording / reproducing apparatus including an optical pickup head that irradiates a focused beam to an information recording layer of the optical information recording medium and receives the return light in order to perform recording / reproducing of information with respect to the optical information recording medium,
As the optical pickup head, the optical pickup head according to any one of claims 1 to 4 is provided, and a condensing point of the main beam is determined based on a light reception level in each light receiving unit of the optical pickup head. An information recording / reproducing apparatus comprising: a layer discriminating unit for discriminating whether the layer is positioned on the information recording layer. The information recording / reproducing apparatus according to claim 5,
The layer discriminating unit individually determines whether or not the light receiving level in the light receiving unit is larger than a preset threshold value, and based on the determination result, what number of layers the information recording layer has the main beam condensing point An information recording / reproducing apparatus characterized by determining whether or not it is located at The information recording / reproducing apparatus according to claim 5,
The beam splitting means generates two sub-beams;
The layer discriminating unit calculates a difference between light receiving levels in the respective light receiving units corresponding to the two sub-beams, and based on the calculated value, a focusing point of the main beam is positioned in the information recording layer. An information recording / reproducing apparatus characterized by determining whether or not The information recording / reproducing apparatus according to claim 5,
The beam splitting means outputs ± n-order diffracted light (n is a natural number) as a sub-beam,
The layer discriminating unit calculates a difference between a sum of light receiving levels in each light receiving unit corresponding to the sub beam of the + nth order diffracted light and a sum of light receiving levels in each light receiving unit corresponding to the sub beam of the −n order diffracted light; An information recording / reproducing apparatus, characterized in that, based on the calculated value, the number of the information recording layers where the condensing point of the main beam is located is determined. In an information recording / reproducing method for recording / reproducing information on / from the optical information recording medium by condensing and irradiating the information recording layer of the optical information recording medium with a light beam,
A beam splitting step of splitting light from the light source to generate at least the same number of light beams as the information recording layer of the optical information recording medium and outputting it as one main beam and a plurality of sub beams;
A beam condensing step of drawing a condensing point of the plurality of light beams by the objective lens into the optical information recording medium;
A return light detection step for individually receiving return light of each light beam reflected by the optical information recording medium;
Providing a layer discrimination step for discriminating how many layers of the information recording layer the condensing point of the main beam is based on the received light level of the return light of each light beam;
In the beam splitting step, the plurality of light beams are generated such that an interval in an optical axis direction by a condensing point of each light beam coincides with an information recording layer interval of the optical information recording medium. Recording and playback method. The information recording / reproducing method according to claim 9,
In the layer discriminating step, it is individually determined whether or not the received light level of the return light of each sub beam is larger than a preset threshold value. Based on the determination result, the focusing point of the main beam is the number of layers. An information recording / reproducing method characterized by determining whether the information recording layer is located. The information recording / reproducing method according to claim 9,
In the beam splitting step, two sub beams are generated,
In the layer discriminating step, the difference between the received light levels of the return lights of the two sub-beams is calculated, and based on the calculated value, the number of the information recording layers where the condensing point of the main beam is located An information recording / reproducing method characterized in that The information recording / reproducing method according to claim 9,
In the beam splitting step, the diffractive optical element splits the light from the light source into 0th order light and ± nth order diffracted light (n is a natural number) and outputs the 0th order light as a main beam and the ± nth order diffracted light as a subbeam. And
In the layer discrimination step, a difference between the sum of the received light levels of the sub-beams of the + n-order diffracted light and the sum of the received light levels of the sub-beams of the −n-order diffracted light is calculated, and the difference is calculated based on the calculated value. An information recording / reproducing method characterized by determining in which information recording layer the focusing point of the main beam is located. A light source, an objective lens for condensing the light from the light source and irradiating the optical information recording medium having a plurality of information recording layers, and at least information recording on the optical information recording medium by dividing the light from the light source Beam splitting means for generating the same number of light beams as a layer and outputting them as one main beam and a plurality of sub beams, and a plurality of light receiving sections for individually receiving the return lights of the respective light beams reflected by the optical information recording medium An information recording / reproducing apparatus including an optical pickup head having
A light receiving level input process for inputting a light receiving level value of the return light of each sub beam in the light receiving unit, and a focusing point of the main beam is positioned in the information recording layer based on each light receiving level value. An information recording / reproducing program for causing a computer to execute a layer discrimination process for discriminating whether or not a layer is present. In the information recording and reproducing program according to claim 13,
In the layer determination process, it is individually determined whether or not each light reception level value input by the light reception level input process is larger than a preset threshold value. Based on the determination result, how many layers the condensing point of the main beam is An information recording / reproducing program characterized in that the content is determined so as to determine whether the eye is located in the information recording layer. In the information recording and reproducing program according to claim 13,
When the beam splitting means generates two sub-beams, the layer discrimination process calculates the difference between the received light level values of the return light of the two sub-beams input by the received light level input process, and based on the calculated value. An information recording / reproducing program characterized in that the content is determined so as to determine the number of information recording layers in which the condensing point of the main beam is located. In the information recording and reproducing program according to claim 13,
The beam splitting means is a diffractive optical element that splits light from a light source into 0th order light and ± nth order diffracted light (n is a natural number) and outputs the 0th order light as a main beam and the ± nth order diffracted light as a subbeam. If
The layer discrimination process calculates a difference between the sum of the light reception level values of the return light of the sub beam of the + n-order diffracted light and the sum of the light reception level values of the return light of the sub beam of the −n-order diffracted light, and based on the calculated value An information recording / reproducing program characterized in that it determines the number of information recording layers in which the main beam condensing point is located.

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