JP2006018937A - Optical pickup device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a compact, thin and low-cost optical pickup device having good environmental change resistance characteristics such as a temperature change even in using a short wavelength laser including a blue laser. <P>SOLUTION: This device is provided with an optical path conversion means arranged in a photodetection optical system to convert a light advancing direction for each of at least four areas divided by a line for dividing the inner and outer sides of a reflected light from an optical recording medium around an optical axis and a straight line including the optical axis, and a photodetecting means arranged in the photodetection optical system and provided with at least four photodetection parts arranged along a straight line parallel to the straight line including the optical axis for dividing the optical path conversion means. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an optical pickup device used for recording / reproduction on a high-density recording disk such as a DVD or an optical disk such as a compact disk.

Conventionally, laser diodes that emit long-wavelength lasers such as infrared lasers and red lasers have been used in optical disk devices, but recently, blue lasers have been used for higher density recording than when using the above lasers. Has come to do. Techniques relating to such high-density recording are disclosed in the following patent documents.
JP 11-224436 A JP 2000-123394 A JP-A-10-334494

  However, a relatively thin and small optical disk drive device incorporated in an electronic device such as a notebook personal computer is required to have particularly high performance environment resistance against temperature changes and the like, and an optical device for recording and reproducing at high density. Since the system has a short wavelength and a large NA, the spherical aberration is larger than that of the conventional optical disc recording / reproducing optical system. Therefore, a means for suppressing it is required separately, which is a big problem in miniaturization.

  The present invention solves the above-described problems, and provides a low-cost optical pickup device that is compact and thin, has good resistance to environmental changes such as temperature changes, and is inexpensive even when using a short wavelength laser including a blue laser. The purpose is to do.

  The present invention has been made to solve the above-described problems, and is a light having a condensing optical system for condensing a light beam onto an optical recording medium and a light detection optical system for detecting reflected light from the optical recording medium. A pickup device, which is arranged in the optical detection optical system, and has at least four regions divided by a line dividing the inner side and the outer side of the reflected light from the optical recording medium around the optical axis, and a straight line including the optical axis Each of the four light receiving units arranged along a straight line parallel to a straight line including an optical axis that divides the optical path changing unit is arranged in the photodetecting optical system. An optical pickup device having a light receiving means having a section.

  According to the present invention, it is easy to integrate a detection optical system including spherical aberration detection, and it is possible to realize an inexpensive, small, and thin optical pickup device that is excellent in environmental resistance against temperature change and the like.

  In addition, by adjusting the rotation of the light receiving element, it is possible to easily adjust the defocus without adjusting the position of the light receiving element or the light emitting point in the optical axis direction. Therefore, high density recording with high NA and short wavelength can be realized. Furthermore, focus and spherical aberration control can be performed stably even with respect to wavelength fluctuations. Accordingly, it is possible to provide an optical pickup device that is small in size and inexpensive and that can stably ensure performance even when the usage environment changes.

  A first invention of the present application is an optical pickup device having a condensing optical system for condensing a light beam onto an optical recording medium and a light detection optical system for detecting reflected light from the optical recording medium, wherein the light detection An optical path arranged in the optical system for converting the light traveling direction for each of at least four areas divided by a line dividing the inner side and the outer side of the reflected light from the optical recording medium around the optical axis and a straight line including the optical axis. A light-receiving unit having four light-receiving units arranged along a straight line parallel to a straight line including an optical axis that divides the optical path changing unit, the light-receiving optical system having a conversion unit; An optical pickup device characterized in that the focus control signal and the spherical aberration control signal that are resistant to disturbance can be detected independently of the reflected light from the optical recording medium inside and outside the optical axis. Small, thin and high reliability It is possible to provide a gender of the optical pickup device.

  According to a second aspect of the present invention, the light receiving unit of the light receiving unit includes two light receiving elements each divided by a dividing line parallel to a straight dividing line including the optical axis of the optical path changing unit, and the light receiving unit includes: Since the optical pickup apparatus includes at least eight light receiving elements, and a composite element that can be easily assembled and adjusted can be realized, a small and inexpensive optical pickup apparatus can be provided.

  According to a third invention of the present application, the light path changing means is configured such that the light in one area inside the reflected light from the optical recording medium is the light receiving part of the first light receiving part which is the end light receiving part of the light receiving means. The light in the same region outside the reflected light from the optical recording medium is condensed on the dividing line, and is condensed on the dividing line of the second light receiving unit which is the light receiving unit adjacent to the first light receiving unit. The light in the other region inside the reflected light from the medium is condensed on the dividing line of the third light receiving unit which is the light receiving unit adjacent to the second light receiving unit, and the other light outside the reflected light from the optical recording medium is collected. An optical pickup device that changes an optical path so that light is condensed on a dividing line of a fourth light receiving unit that is a light receiving unit adjacent to the third light receiving unit. Since this can be realized, a small and inexpensive optical pickup device can be provided.

  According to a fourth invention of the present application, in the light receiving means, a signal output of a light receiving element on one side of the first light receiving unit which is the end light receiving unit, and a second light receiving unit adjacent to the first light receiving unit. The signal output of the light receiving element on the same one side of the light receiving unit, the signal output of the light receiving element on the other side of the third light receiving unit which is the light receiving unit adjacent to the second light receiving unit, and the next to the third light receiving unit A signal output obtained by adding the signal outputs of the same light receiving elements on the other side of the fourth light receiving part, and a signal output of the light receiving elements on the other side of the first light receiving part, which is the outermost light receiving part. , A signal output on the same other side of the second light receiving unit as the light receiving unit adjacent to the first light receiving unit, and a light receiving element on one side of the third light receiving unit as the light receiving unit adjacent to the second light receiving unit And the signal output of the light receiving element on the same one side of the fourth light receiving unit which is the light receiving unit adjacent to the third light receiving unit, respectively. An optical pickup device having a differential signal output as a focus control signal for the light beam, and a stable focus control signal can be obtained. Therefore, the optical pickup device is small, thin and highly reliable. Can be provided.

  According to a fifth aspect of the present invention, in the light receiving means, there are a signal output of a light receiving element on one side of the first and fourth light receiving units which are two outer light receiving units, and two inner light receiving units. A signal output obtained by adding the signal outputs of the light receiving elements on the other side of the second light receiving unit and the third light receiving unit, and light reception on the other side of the first light receiving unit and the fourth light receiving unit, which are the two outer light receiving units. The spherical aberration control signal is determined by the difference between the signal output of the element and the signal output obtained by adding together the signal outputs of the light receiving elements on one side of the second light receiving part and the third light receiving part as the inner two light receiving parts. Since a stable spherical aberration control signal can be obtained, a small, thin and highly reliable optical pickup device can be provided.

According to a sixth aspect of the present invention, as the condensing optical system, a light source, parallel light converting means for converting light emitted from the light source into parallel light, and parallel light emitted from the parallel light converting means to the optical recording medium. An optical pickup device provided with a condensing means for condensing a light beam, and can be made into a condensing optical system with high light use efficiency during recording, so it is small, thin and highly reliable. An optical pickup device can be provided.

  A seventh invention of the present application is the optical pickup device according to claim 6, wherein a semiconductor laser is used as the light source. Since the optical pickup device can be an inexpensive and high-performance light source, the optical pickup device is inexpensive. Can be provided.

  An eighth invention of the present application is the optical pickup device according to claim 6, wherein a lens is used as the parallel light converting means, and can be used as an inexpensive and high-performance parallel light converting means. An optical pickup device can be provided.

  A ninth invention of the present application is an optical pickup device characterized by using a lens as the condensing means, and can provide an inexpensive and high-performance condensing means, and therefore provides an inexpensive optical pickup device. be able to.

  According to a tenth aspect of the present invention, as the detection optical system, an optical phase conversion unit that converts light from linearly polarized light to circularly polarized light, a polarization separation unit that separates light according to a polarization direction, an optical path conversion unit, and a light receiving unit The optical pickup device is characterized in that it can be a condensing optical system with high light utilization efficiency during recording, and thus a small, thin and highly reliable optical pickup device can be provided. .

  An eleventh invention of the present application is an optical pickup device characterized by using a diffractive optical element as the optical path changing means, and can be used as an inexpensive optical path changing means, and therefore provides an inexpensive optical pickup apparatus. can do.

  A twelfth aspect of the present invention is an optical pickup device using a polarizing diffractive optical element as the optical path changing means, and is a condensing optical system having high light use efficiency during recording. Therefore, a small, thin and highly reliable optical pickup device can be provided.

  A thirteenth invention of the present application is an optical pickup device using a photodiode as the light receiving means, and can provide an inexpensive and high-performance light receiving means, and therefore provides an inexpensive optical pickup device. Can do.

  A fourteenth invention of the present application is an optical pickup device characterized in that a quarter-wave plate is used as the optical phase converting means, and can be used as an inexpensive optical phase converting means. An apparatus can be provided.

  A fifteenth invention of the present application is an optical pickup device using a polarization separation film as the polarization separation means, and can provide an inexpensive polarization separation means, and therefore provides an inexpensive optical pickup device. be able to.

  A sixteenth aspect of the present invention is an optical pickup device characterized in that the polarization separation means and the optical path conversion means are the same optical integrated member, and the polarization separation means and the optical path conversion means are each configured as a single unit. Therefore, even if a disturbance such as a temperature change occurs, the amount of change in the positional relationship is small, so that a small, thin and highly reliable optical pickup device can be provided.

A seventeenth invention of the present application is an optical pickup device characterized in that the light source, the light receiving means and the optical integrated member are the same composite element, and each other even if a disturbance such as a temperature change occurs. Since the amount of change in the positional relationship is small, a small, thin and highly reliable optical pickup device can be provided.

  Hereinafter, an optical pickup device according to Embodiment 1 of the present invention will be described with reference to the drawings.

(Embodiment 1)
FIG. 1 is a perspective view of a main part of an optical pickup device according to Embodiment 1 of the present invention. First, reference numeral 10 denotes an optical disk. The optical disk 10 is irradiated with light so that at least one of information reproduction and information recording can be performed. Specifically, the optical disc 10 is a CD-ROM disc, a DVD-ROM disc or the like that can only reproduce information, and a CD-R disc or a DVD-R disc that can record information in addition to the reproduction of information. In addition, CD-RW discs, DVD-RW discs, DVD-RAM discs and the like capable of recording / erasing information are preferably used. The optical disc 10 includes a recording layer capable of recording or reproducing information with substantially red light, a recording layer capable of recording or reproducing information with substantially infrared light, and substantially blue to approximately. Those having a recording layer capable of recording or reproducing information with blue-violet light can be used.

  Further, as the size of the optical disc 10, disc-shaped ones having various diameters can be used, but a disc-like one having a diameter of 3 cm to 12 cm is preferably used. Further, a multi-layer disc having a plurality of recording layers may be used to increase the recording procedure. As shown in the figure, the radial direction (hereinafter abbreviated as “R direction”) from the center of the optical disc 10 toward the outer peripheral side, and the tangential direction of the optical disc 10 (hereinafter abbreviated as “T direction”). And define the direction.

  Reference numeral 1 denotes an optical pickup for recording information on the optical disk 10 and reading information from the optical disk 10 by irradiating the optical disk 10 with light. Hereinafter, main components of the optical pickup 1 will be described.

  Reference numeral 30 denotes a composite element that incorporates a laser, a light receiving element, a prism, and the like. Although not shown, the forward light 24a emitted from the composite element 30 is converted into parallel light by the collimator lens 12 and then raised to the objective lens 15 by the raising mirror 14 to be a λ / 4 wavelength plate. And is condensed on the optical disk 10 by the objective lens 15. The return light 24b reflected by the optical disk 10 and having recorded information on the disk passes through the objective lens 15 and is converted back to parallel light, passes through the λ / 4 wavelength plate, and rises toward the composite element 30 by the rising mirror 14. Thus, the composite element 30 is returned. As a result, the composite element 30 detects the return light 24b, thereby irradiating the disc information and the spot of the forward light 24a by the objective lens 15 on the recording surface of the optical disk 10 even if disturbance such as vibration occurs. Servo information for controlling the signal is extracted and converted into electrical signals, so that the recorded information recorded in advance on the optical disc 10 can be electrically reproduced. The composite element 30, the collimator lens 12, the raising mirror 14, and the actuator 18 are mounted on the pickup base 19.

  Next, the composite element 30 will be described. FIG. 2 is a perspective view showing the entire composite element. In FIG. 2, the composite element 30 includes a light source 11, an integrated optical member 40, a light receiving element 50, and a coupling member 33. These components will be described in order.

First, the light source 11 is obtained by fixing a general-purpose semiconductor laser 31 to a base member 32. Since a very general general-purpose semiconductor laser 31 can be used, a low-cost pickup device can be provided.

  The integrated optical member 40 is disposed on the laser light emission window of the semiconductor laser 31, the coupling member 33 is disposed on the flat surface of the semiconductor laser 31, and the light receiving element 50 is disposed on the side surface of the coupling member 33. The power supply to the semiconductor laser 31, the power supply to the light receiving element 50, and the acquisition of the electric signal are performed by connecting to the outside with the flexible cable 35.

  Next, the integrated optical member 40 will be described with reference to FIG. FIG. 3 is a cross-sectional view showing the positional relationship between the integrated optical member 40, the light source 11, and the light receiving element 50. The vertical direction on the paper surface is the T direction and the horizontal direction on the paper surface is the R direction. The integrated optical member 40 is basically formed by cutting a glass material into a quadrangular shape, and has a structure having a polarization separation film 41 and a reflection hologram 42 therein. The polarization separation film 41 is a film that controls reflection and transmission according to the direction of polarization of incident light, and the reflection hologram 42 has an optical element having a function of changing the path of reflected light of incident light in a certain direction. It is. First, the forward light 24 a emitted from the light source 11 enters the integrated optical member 40 and enters the polarization separation film 41 inside thereof. High utilization efficiency can be obtained by arranging the light source 11 with respect to the integrated optical member 40 so that the transmittance is approximately 100%.

  The forward light 24a that has passed through the polarization separation film 41 passes through the integrated optical member 40 as it is and travels toward the collimator lens. The return light 24b reflected from the disk passes through the optical system described above and reaches the integrated optical member 40 again. The return path light 24b is reflected by the polarization separation film 41 in the integrated optical element by approximately 100% because the polarization direction of the return path light 24b is rotated by 90 degrees with respect to the forward path light. The return light 24 b reflected here is then changed in the direction toward the light receiving pattern of the light receiving element 50 by the reflection hologram 42 and finally reaches the light receiving element 50.

  Next, a method for acquiring a focus control signal using the reflection hologram 42 will be described.

  FIG. 4 is a perspective view showing the relationship between the hologram pattern of the reflection hologram 42 and the light receiving pattern of the light receiving element 50. As described above, the return path light 24 b reflected by the disk is incident on the integrated optical member 40, reflected by the polarization separation film 41, and subjected to a path changing action by the reflection hologram 42. As shown in the drawing, the reflection hologram 42 is divided into regions 42a and 42b by dividing lines parallel to the R direction, and the holograms are formed so that the directions after the course change are different. In this case, the hologram is formed so that the light incident on the region 42a of the reflective hologram 42 is condensed on the light receiving pattern 51a and the light incident on the region 42b is condensed on the light receiving pattern 51b.

FIG. 5 is a diagram showing a simple equivalent optical system for easier understanding. The spot 21 on the disk irradiated onto the optical disk 10 is reflected by the optical disk 10 to become return light 24b, is converted into parallel light through the objective lens 15, and is then converted into convergent light by the collimator lens 12. The converged light is converted in its path by the reflection hologram 42 and condensed on the light receiving patterns 51 a and 51 b on the light receiving element 50. The reflection hologram 42 is originally a reflection type, but is illustrated as an equivalent transmission hologram for easy understanding. The light receiving patterns 51a and 51b are separated by a dividing line parallel to the R direction, and light reaching the light receiving regions 51aA, 51aB, 51bA, and 51bB is converted into electric signals V51aA, V51aB, V51bA, and V51bB by the light receiving element 50, respectively. Detected. As shown in the figure, since the spots 22a and 22b collected on the light receiving pattern are collected on the dividing line of the light receiving pattern, the amounts of light entering the light receiving areas 51aA and 51aB are equal, and the light receiving areas 51bA and 51bB. The amount of light entering is equal. That is, Formula (1), Formula (2)
A = V51aA + V51bA Formula (1)
B = V51aB + V51bB Formula (2)
By defining A and B, the focus error signal (FE) is
FE = A−B Formula (3)
Then,
FE = 0 Formula (4)
It becomes.

Here, a case where the optical disk 10 is separated from the objective lens 15 is considered. FIG. 6 is a diagram illustrating a change in the return path light 24b when the optical disk 10 is separated from the objective lens 15. In FIG. The spot 21 on the disk on the optical disk 10 generates a mirror image 21p by the optical disk 10 because the optical disk 10 is separated. When viewed from the objective lens 15, it appears as if the spot 21 on the disk has moved upwards on the paper surface, so that the spot on the light receiving pattern also moves to 22bp and 22ap above the paper surface. As a result, as illustrated, the amount of light entering the light receiving areas 51bB and 51aB increases, and the amount of light entering the light receiving areas 51bA and 51aA decreases. That is, since B increases and A decreases, FE <0 Equation (5)
It becomes.

Similarly, consider the case where the optical disk 10 approaches the objective lens 15. FIG. 7 is a diagram illustrating a change in the return light 24b when the optical disk 10 approaches the objective lens 15. In FIG. The spot 21 on the disk on the optical disk 10 generates a mirror image 21m by the optical disk 10 because the optical disk 10 has approached. When viewed from the objective lens, it appears as if the spot 21 on the disc has moved downward on the paper surface, so the spot on the light receiving pattern also moves to 22bm and 22am below the paper surface. As a result, as illustrated, the amount of light entering the light receiving areas 51bB and 51aB decreases and the amount of light entering the light receiving areas 51bA and 51aA increases. That is, B decreases and A increases,
FE> 0 Formula (6)
It becomes.

In summary, when the optical disk 10 is moved away from the objective lens 15,
FE <0 Formula (5)
When the optical disk 10 approaches the objective lens 15,
FE> 0 Formula (6)
Therefore, the FE signal can be used as a focus control signal.

  Next, advantages of this focus signal method will be described. FIG. 8A is a view showing an equivalent optical system of the integrated optical member 40 including the polarization separation film 41. The forward light 24 a emitted from the light source 11 passes through the polarization separation film 41 and is converted into parallel light by the collimator lens 12. The return light 24b reflected by the disk returns to the collimator lens 12 with parallel light when there is no change in the position of the disk, that is, when there is no defocus, and is reflected by the polarization separation film 41 and converted into a light receiving pattern by the reflection hologram 42 Led. The reflection hologram 42 is formed so as to focus on the light receiving pattern when the parallel light returns to the collimator lens 12, that is, when there is no defocus. However, when the light source 11 has an attachment error in the optical axis direction and becomes the position 11c as shown in FIG. 8B, the forward light 24a emitted from the light source 11c after this positional deviation is transmitted to the collimator lens 12. Since the positional relationship is not appropriate, the state is shifted from the parallel light. In the case of FIG. 8B, since the distance between the light source 11 and the collimator lens 12 is away from the collimator lens 12, the collimator lens 12 is emitted as weakly convergent light. In this case, the reflected light 24b from the disk is not parallel light when returning to the collimator lens 12 even when no defocusing occurs, so that the light emitted from the reflection hologram 42 is also emitted in a defocused state. The upper spot is also displaced in the direction of the optical axis and becomes the position 22c.

  Accordingly, when the positional deviation of the light source 11 in the optical axis direction occurs, defocusing occurs on the light receiving element 50, and it is necessary to adjust this defocusing by some method. As one method, it is possible to cancel the defocus by adjusting the position of the light source 11 or the light receiving element 50 in the optical axis direction until the defocus becomes 0. However, as in the present embodiment, the integrated optics is used. Taking the form of the element, it is extremely difficult to adjust the position of the light source 11 and the light receiving element 50 in the optical axis direction, and some other defocus adjustment method is required.

  FIG. 9 is a diagram for explaining a defocus adjustment method according to the present embodiment. When defocusing occurs on the light receiving element 50, the spot on the light receiving pattern becomes semicircular as shown in FIG. 9A, and defocusing occurs due to the increase of A or B described above (see FIG. 9). In this case, A increases). Here, as shown in FIG. 9B, when the entire light receiving element is rotated with the intermediate point between the light receiving pattern 51b and the light receiving pattern 51a as the light receiving element rotation center 53 and the optical axis direction (perpendicular to the paper surface) as the rotation axis, The spot on each light receiving pattern relatively moves to the right or left. In the case of this figure, by rotating the light receiving element counterclockwise around the rotation center 53, the spot on the light receiving pattern 51b is moved to the right relatively, and it is biased to the light receiving area 51bA before rotation. Light is positioned between 51bA and 51bB. Similarly, the spot on the light receiving pattern 51a moves relatively to the left, and the light deviated to the light receiving area 51aA before rotation is positioned between 51aA and 51aB.

  Therefore, A and B become equal amounts, and as a result, defocus can be canceled. In other words, the focus signal system of the present embodiment adjusts the light receiving element around the intermediate point between the two light receiving patterns 51a and 51b with the optical axis direction as the rotation axis, thereby adjusting the light receiving element or the light emitting point to the optical axis. The defocus adjustment is possible without adjusting the position in the direction, and this is a particularly advantageous method when taking the form of an integrated optical member.

  Next, spherical aberration correction will be described. The optical disc 10 has a transparent cover layer having a specific thickness. Since the objective lens 15 is designed so that the outward light is well imaged through the cover layer, when the thickness of the cover layer deviates from a specific thickness, generally, spherical aberration occurs and the spot on the optical disk 10 is spotted. Deteriorate quality. Since the spherical aberration due to the thickness error of the cover layer increases in proportion to the fourth power of NA and the reciprocal of the wavelength, this spherical aberration cannot be ignored as the NA increases and the wavelength decreases for high density recording. Therefore, some spherical aberration correcting means is required to cope with a high density recording disk. Further, since the cover layer thickness error varies depending on the location of the optical disc 10, this spherical aberration correction requires real-time control, and it is necessary to detect spherical aberration due to the cover layer thickness error and feed it back to the spherical aberration correction means. .

  First, an example of spherical aberration correction means will be described. FIG. 10A shows a state in which there is no cover layer thickness error of the optical disc 10. The forward light 24 a emitted from the light source 11 is converted into parallel light by the collimator lens 12, and a spot 21 on the disk is formed on the recording surface of the optical disk 10 by the objective lens 15. As described above, the objective lens 15 is designed to form the spot 21 on the disk on the recording surface well when the cover layer of the optical disk 10 has a predetermined thickness, so that there is no error in the thickness of the cover layer. No problem with spot quality.

Here, when the collimator lens 12 is displaced in the optical axis direction as shown in FIG. 10B, the outgoing light 24a after being emitted from the collimator lens 12 is shifted from the parallel light and becomes divergent light or convergent light. In the case of the figure, since the collimator lens 12 is in the direction approaching the light source 11, it becomes divergent light after being emitted from the collimator. When this light enters the objective lens 15 and passes through the optical disk 10, spherical aberration is generated along with defocusing. Since defocus is subjected to focus servo control, it can be removed by moving the objective lens 15 in the optical axis direction by the actuator 18, but the spherical aberration remains. That is, there are two causes for the occurrence of spherical aberration, when the cover layer thickness of the optical disc 10 changes and when the collimator lens 12 moves in the optical axis direction. The generated spherical aberration can be canceled by moving the collimator lens 12 in the direction of the optical axis and generating spherical aberration of the opposite sign. Accordingly, it is possible to provide spherical aberration correction means by mounting the actuator 18 for controlling the position of the collimator lens 12 in the optical axis direction on the pickup.

  Next, the spherical aberration detection means will be described. FIG. 11 is a diagram for explaining the phase distribution of aberration. The forward light 24a emitted from the objective lens 15 forms a spot 21 on the disk on the recording surface of the optical disk 10, but temporarily passes through the optical disk 10 as it is to the reference spherical surface 25 centered on the spot 21 on the disk on the disk recording surface. Suppose that it has reached. As shown, this figure defines the phase of light from the emission point at the point on the reference sphere in the radial direction R around the intersection of the optical axis and the reference sphere as Φ (R). Yes. When there is no aberration in the optical system, Φ is 0 for all R, but when there is aberration, Φ has a distribution with respect to R.

  FIG. 12 shows the distribution of Φ (R) when spherical aberration occurs. If the region is divided into the inside and the outside of the two peaks indicated by dotted lines in the figure, it can be approximated to two parabolas having different signs. Since Φ (R) becomes a parabola when it is defocused, the distribution of Φ (R) due to spherical aberration is roughly two different defocused aberrations when divided into the inside and outside of the peak. Therefore, the hologram can be divided into areas on the inner side and outer side of the light diameter, the focus signal is taken independently, and the differential signal is used as a spherical aberration detection signal.

  Next, the spherical aberration detector in the present embodiment will be described. FIG. 13 shows spherical aberration detection means in a state where no spherical aberration occurs in the optical system and there is no defocus on the optical disk recording surface. The return light 24b reflected by the optical disk 10 passes through the objective lens 15 and is converted into parallel light, and then converted into convergent light by the collimator lens 12. The converged light is converted in its path by the reflection hologram 42 and condensed on the light receiving patterns 51 a, 51 b, 51 c and 51 d on the light receiving element 50. The reflection hologram 42 is divided into regions by a dividing line parallel to the R direction, and the region is divided into a total of four by a circle that divides the inner side and the outer side of the return light 24b around the optical axis. As shown in the figure, these hologram regions 42a and 42b corresponding to the outside of the beam are condensed on the light receiving patterns 51a and 51b, 42c and 42d corresponding to the inside of the beam are condensed on the light receiving patterns 51c and 51d, It is formed so as to be spots 22a, 22b, 22c and 22d on the light receiving element.

The light receiving patterns 51a, 51b, 51c and 51d are separated by a dividing line parallel to the R direction, and the light reaching the light receiving regions 51aA, 51aB, 51bA, 51bB, 51cA, 51cB, 51dA, 51dB is received by the light receiving element 50. The electric signals V51aA, V51aB, V51bA, V51bB, V51cA, V51cB, V51dA, and V51dB are detected after being converted. As shown in the figure, since 22a, 22b, 22c and 22d collected on the light receiving pattern are collected on the dividing line of the light receiving pattern, the light receiving regions 51aA and 51aB, the light receiving regions 51bA and 51bB, and the light receiving region 51cA are collected. And 51cB and the light amounts entering the light receiving areas 51dA and 51dB are equal. Here, Formula (7), Formula (8),
Ain = V51cA + V51dA Formula (7)
Bin = V51cB + V51dB (8)
By defining Ain and Bin, the focus error signal (FEin) is
FEin = Ain−Bin (9)
Then,
FEin = 0 Formula (10)
It becomes. This FEin corresponds to the defocus amount in the inner region of the return path light 24b. Similarly, Formula (11), Formula (12),
Aout = V51aA + V51bA Formula (11)
Bout = V51aB + V51bB (12)
By defining Aout and Bout, the focus error signal (FEout)
FEout = Aout−Bout (13)
Then,
FEout = 0 Formula (14)
It becomes. This FEout corresponds to the defocus amount in the outer region of the return path light 24b. As described above, the spherical aberration detection signal may be obtained by taking the differential between the inner and outer focus signals of the return path light 24b.
SAE = FEin−FEout (15)
SAE can be used as a spherical aberration detection signal. in this case,
SAE = 0 (16)
It is. The normal focus error signal is
FE = FEin + FEout (17)
Should be defined.

Hereinafter, the state of a spherical aberration detection signal when spherical aberration actually occurs will be described with reference to FIG. FIG. 14A is a diagram showing how the return light 24b reaches the light receiving element 50 when a certain amount of spherical aberration occurs. When there is spherical aberration in the optical system, different defocuses occur on the inner side and the outer side of the outward light in the optical disc 10. Therefore, a mirror image 21ip of the spot on the disk is generated in the inner area of the mirror image by the optical disc 10, and a mirror image 21op of the spot on the disk is generated in the outer area. When viewed from the objective lens, it appears as if the inner area has moved upward from the disk surface and the outer area has moved downward from the paper surface, so that the spot on the light receiving pattern is also moved to the 22 dsap and 22csap above the paper surface. The outer area moves to 22 asap and 22 bsap below the page. As a result, as shown in the figure, the light receiving areas 51dB and 51cB, the light receiving areas 51bA and 51aA are increased, and the light receiving areas 51dA and 51cA and the light receiving areas 51bB and 51aB are decreased. That is, since Bin and Aout described above increase and Ain and Bout decrease,
FEin <0 Formula (18)
FEout> 0 Formula (19)
And
SAE <0 Formula (20)
It becomes.

Similarly, consider the case where spherical aberration occurs with the opposite sign. FIG. 14B is a diagram showing how the return path light 24b reaches the light receiving element 50 when spherical aberration having the opposite sign to that in FIG. 14A occurs. Since spherical aberration opposite to that in FIG. 14 (a) occurs, it is as if viewed from the objective lens as if it moved from the disk recording surface to the lower area on the inner side and to the upper side on the outer side. In the spot on the light receiving pattern, the inner region moves to 22 dsam and 22 csam below the paper surface, and the outer region moves to 22 asam and 22 bsam above the paper surface. As a result, as shown in the figure, the light receiving areas 51dB and 51cB, the light receiving areas 51bA and 51aA are decreased, and the light receiving areas 51dA and 51cA and the light receiving areas 51bB and 51aB are increased. That is, since Bin and Aout are decreased and Ain and Bout are increased, FEin> 0 (Equation 21)
FEout <0 Formula (22)
And
SAE> 0 Formula (23)
It becomes.

In summary, if the optical system has a certain amount of spherical aberration,
SAE <0 Formula (20)
And having a spherical aberration with the opposite sign,
SAE> 0 Formula (23)
Therefore, this SAE signal can be used as a spherical aberration detection signal.

  FIG. 15 is a diagram for explaining a defocus adjustment method according to the present embodiment which also has a spherical aberration detection function. When defocusing occurs on the light receiving element 50, as shown in FIG. 15A, the spot on the light receiving pattern becomes a semicircular shape or an arc shape, and the aforementioned Ain, Aout, Bin, Bout increases. Causes defocus (in the figure, Ain and Aout increase). Here, as shown in FIG. 15 (b), the light receiving element rotation center 53 is the intermediate point between the light receiving pattern 51d and the light receiving pattern 51a (also the intermediate point between the light receiving pattern 51b and the light receiving pattern c). When the entire light receiving element is rotated about the vertical axis), the spot on each light receiving pattern relatively moves to the right or left. In the case of this figure, by rotating the light receiving element counterclockwise around the rotation center 53, the spot on the light receiving pattern 51b is relatively moved to the right, and is deviated to the light receiving region 51bA before rotation. The light that has fallen is positioned between 51bA and 51bB. Similarly, spots on the light receiving pattern 51d move relatively to the left, and spots on the light receiving pattern 51a and the light receiving pattern 51c move relatively to the left. Before the rotation, the light receiving area 51dA, the light receiving area 51aA, and the light receiving area, respectively. The light deviated from the area 51cA is positioned on the dividing line of each light receiving pattern. Therefore, A and B become equal amounts, and as a result, defocus can be canceled.

  Next, the merit of the arrangement of the light receiving elements of this embodiment will be described. FIG. 15C is a diagram showing defocus adjustment by rotating the light receiving element when the positions of the light receiving patterns 51c and 51a are switched. That is, the light receiving pattern for receiving the outer region of the return path light 24b and the light receiving pattern for receiving the inner region are arranged on the outer side and the inner side, respectively, with respect to the light receiving element rotation center 53 that is an intermediate point. When the light receiving element is rotated and defocused in this state, the light receiving patterns 51b and 51a are adjusted by rotating and adjusting the light receiving patterns 51d and 51c so that the spot is positioned on the dividing line as shown in FIG. The spot cannot be positioned at an appropriate position through the dividing line. In other words, since the defocus amount in the inner region and the defocus amount in the outer region of the return path light with respect to a certain light receiving element rotation angle are different, it can be said that defocus adjustment to make both are zero is extremely difficult. If the light receiving pattern for receiving the inner region of the return light and the light receiving pattern for receiving the outer light are alternately arranged as in this embodiment, the amount of movement of the spot on the light receiving element due to a certain light receiving element rotation angle is surely reduced. Since the two light receiving regions that receive the inner side and the two light receiving regions that receive the outer side of the return path light are different, the light receiving pattern in the inner region and the light receiving pattern in the outer region are positioned in contrast to the rotation center 53. At least the defocus amounts of the inner area and the outer area coincide with each other, and the defocus adjustment that sets both to zero becomes easy.

Next, the arrangement intervals of the light receiving patterns 51a to 51d will be described. As shown in FIG. 15B, when the arrangement intervals of the four light receiving patterns are all the same, the defocus amount in the inner region and the defocus amount in the outer region of the return light with respect to a certain light receiving element rotation angle are the same as described above. Therefore, it is possible to easily adjust the defocus so that both are zero. However, it is assumed that the interval between the light receiving patterns 51b and 51a and the interval between the light receiving patterns 51d and 51c, that is, the interval between the light receiving pattern and the outer region in the inner area of the return light. If the light receiving pattern intervals are different, the defocus amount in the inner region and the defocus amount in the outer region of the return path light with respect to a certain light receiving element rotation angle are not the same. Accordingly, it is actually necessary to make the interval between the light receiving patterns in the inner region of the return path light substantially equal to the interval between the light receiving patterns in the outer region.

  FIG. 16 shows a change in the position of the spot on each light receiving pattern when the wavelength varies. Since the paths of the spots 22a, 22b, 22c, and 22d on the light receiving pattern are changed by the hologram, when the wavelength of light changes, the amount of change of the path changes and the position is shifted as indicated by the arrow on the light receiving pattern. Since the direction of the misalignment coincides with the direction of the course change, it is necessary to make the direction of the course change by the hologram substantially coincide with the direction of each light receiving pattern. That is, since the return light before entering the hologram travels along the optical axis, it is necessary to define a straight line connecting the optical axis and each light receiving pattern and to match the dividing direction of each light receiving pattern with the straight line. Further, in order to facilitate the defocus adjustment by rotation, it is desirable to arrange all the light receiving patterns on the straight line. Then, even if the wavelength of the light fluctuates, there is no influence because the spot is only displaced on the dividing line of the light receiving pattern.

  Next, an embodiment in which a focus error signal and a spherical aberration detection signal are detected independently will be described. In the embodiments described so far, the focus error signal and the spherical aberration detection signal are separated by the calculation of the received light signal using the common hologram area and the received light pattern for both the focus error signal and the spherical aberration detection signal. In this case, since the number of light receiving patterns can be reduced, a structurally simple light receiving element can be configured. However, on the other hand, it is impossible to optimize the light receiving patterns for the focus error signal and the spherical aberration detection signal. Become. Therefore, in some cases, it may be necessary to detect the focus error signal and the spherical aberration detection signal independently.

  FIG. 17 is a diagram showing an example when the focus error signal and the spherical aberration detection signal are detected independently. The return light 24b reflected by the optical disk 10 passes through the objective lens 15 and is converted into parallel light, and then converted into convergent light by the collimator lens 12. The converged light is converted in its path by the reflection hologram 42 and condensed on the light receiving patterns 51a, 51b, 51c, 51d, 51e, 51f on the light receiving element 50. The reflection hologram 42 is divided into regions by a dividing line parallel to the R direction, and the region is further divided into two circles that divide the return path light 24b inside and center, and the stop portion and outside with the optical axis as a center. It is divided into two. As shown in the figure, the hologram regions 42a and 42b corresponding to the outside of the beam are on the light receiving patterns 51a and 51b, and 42c and 42d corresponding to the inside of the beam are on the light receiving patterns 51c and 51d. 42e and 42f corresponding to the portions are condensed on the light receiving patterns 51e and 51f, and are formed so as to become the light receiving element top spots 22a, 22b, 22c, 22d, 22e and 22f. The light receiving patterns 51a, 51b, 51c and 51d are separated into two by a dividing line parallel to the R direction, and the light receiving patterns 51e and 51f are divided into four by a dividing line parallel to the R direction. The light reaching the light receiving areas 51aA, 51aB, 51bA, 51bB, 51cA, 51cB, 51dA, 51dB, 51eA, 51eA2, 51eB, 51eB2, 51fA, 51fA2, 51fB, 51fB2 is received by the light receiving element 50, respectively. , V51bB, V51cA, V51cB, V51dA, V51dB, V51eA, V51eA2, V51eB, V51eB2, V51fA, V51fA2, V51fB, and V51fB2.

As shown in the figure, since 22a, 22b, 22c, 22d, 22e, and 22f collected on the light receiving pattern are collected on the dividing line of the light receiving pattern, the light receiving areas 51aA and 51aB and the light receiving area 51bA The amounts of light entering 51bB, light receiving areas 51cA and 51cB, light receiving areas 51dA and 51dB, light receiving areas 51eA and 51eB, and light receiving areas 51fA and 51fB are equal. Here, Formula (24), Formula (25),
Ain = V51cA + V51dA Formula (24)
Bin = V51cB + V51dB Formula (25)
By defining Ain and Bin, the focus error signal (FEin) is
FEin = Ain−Bin Formula (26)
Then,
FEin = 0 Formula (27)
It becomes. This FEin corresponds to the defocus amount in the inner region of the return path light 24b. Similarly, Formula (28), Formula (29),
Aout = V51aA + V51bA Formula (28)
Bout = V51aB + V51bB Formula (29)
By defining Aout and Bout, the focus error signal (FEout)
FEout = Aout−Bout (30)
Then,
FEout = 0 Formula (31)
It becomes. This FEout corresponds to the defocus amount in the outer region of the return path light 24b. As described above, the spherical aberration detection signal may be obtained by taking the differential between the inner and outer focus signals of the return path light 24b.
SAE = FEin−FEout Expression (32)
SAE can be used as a spherical aberration detection signal. in this case,
SAE = 0 Formula (33)
It is.

  If the outer side and the inner side are separated with the central part of the beam sandwiched as in this example, the defocus difference between the outer side and the inner side due to spherical aberration tends to be larger than when the central part is not sandwiched. That is, it is possible to increase the sensitivity of detecting spherical aberration, and this method is effective when it is necessary to tune this sensitivity due to the characteristics of the spherical aberration correction function of the entire system.

Moreover, Formula (34), Formula (35),
Af = V51eA + V51eA2 + V51fA + V51fA2 Formula (34)
Bf = V51eB + V51eB2 + V51fB + V51fB2 Formula (35)
By defining Af and Bf, the focus error signal (FEf) is expressed as FEf = Af−Bf (36)
Then,
FEf = 0 ... Formula (37)
It becomes.

  In this way, by separating the light receiving patterns of the focus error signal and the spherical aberration detection signal, the amplifier gain and the like at the subsequent stage can be individually set, and an optimum design in terms of electric circuit is possible. Then, as shown in the figure, the light receiving areas 51eA2, 51eB2, 51fA2, and 51fB2 are arranged in the focus error signal light receiving patterns 51e and 51f outside the original light receiving area with the reverse sign in the focus error signal calculation. Yes. When defocusing occurs, the spots on these light receiving patterns become semicircular arc-shaped beams, and the beam increases in the direction perpendicular to the dividing line as defocusing occurs. If a light receiving area with an opposite sign is arranged outside the light receiving area, the focus error signal rapidly converges to 0 because the sign is reversed when the defocus is further increased and a beam enters the outer light receiving area. . That is, the focus error signal exists only in a very narrow defocus area, and it is effective when the reflected light from the next recording layer cannot be ignored when there is a next recording layer at a relatively short distance from the recording layer in a multilayer disc. .

As described above, the focus error signal and the spherical aberration detection signal can be optimized independently by increasing the number of divided areas of the hologram, the number of light receiving patterns, and the number of divided areas. However, since the configuration is complicated, there is a possibility that demerits such as ease of adjustment and product cost may occur. However, the optimal solution must be applied as a total from the balance with performance.

  Next, light receiving pattern arrangement options other than the present embodiment will be described. In an actual light receiving element arrangement, there is a possibility that it cannot be ideally arranged in a straight line due to restrictions on space or the like, and it is necessary to consider various arrangement options. FIG. 18A to FIG. 18D are diagrams showing a case where the respective light receiving patterns are arranged out of a straight line.

  FIG. 18A shows a case where the light receiving patterns 51b and 51a for receiving the inner area of the beam are offset on the right side of the paper and the light receiving patterns 51d and 51c for receiving the outer area of the beam are offset on the left side of the paper. Also in this case, the interval between the light receiving patterns 51b and 51a that receive the inside of the beam and the interval between the light receiving patterns 51d and 51c that receive the outside of the beam are equal, and the light receiving pattern that receives the inside of the beam and the light receiving pattern that receives the outside of the beam are alternated. Therefore, there is always a rotation center 53 in which the defocus sensitivities on the inside and outside of the beam by rotation adjustment are equal to each other. In addition, when wavelength variation occurs, the spot on each light receiving pattern moves along a line connecting each light receiving pattern with the intersection 54 between the optical axis and the light receiving element.

  Accordingly, since each light receiving pattern is not arranged on a straight line parallel to the dividing line of the light receiving pattern, the spot on each light receiving pattern is biased to the left or right light receiving region in the drawing. However, for example, when the spot is deviated in the light receiving area 51bB in the light receiving pattern 51b, the light receiving pattern 51a is deviated in the light receiving area 51aA, so that when the focus error signal is calculated, the focus error signal due to the wavelength variation, The influence of the spherical aberration detection signal is small.

  FIG. 18B shows a case where all the light receiving patterns are arranged on an oblique straight line. As in the case of FIG. 18A, the interval between the light receiving patterns 51b and 51a that receive the inside of the beam is equal to the interval between the light receiving patterns 51d and 51c that receive the outside of the beam, and further, the light receiving pattern that receives the inside of the beam. Since the light receiving patterns for receiving the light beam outside and the beam outside are alternately arranged, there always exists a rotation center 53 in which the defocus sensitivities on the beam inner side and the beam outer side by rotation adjustment are equal to each other. In addition, when wavelength variation occurs, a spot on each light receiving pattern moves along a line connecting the intersection 54 of the optical axis and the light receiving element and each light receiving pattern, and the spot on each light receiving pattern is either left or right in the drawing. The light receiving area is biased. In this case, for example, when the spot is deviated in the light receiving area 51bB in the light receiving pattern 51b, the light receiving pattern 51a is deviated in the light receiving area 51aB, so that there is no effect of canceling the focus error signal, and an offset occurs in the focus error signal. . Since the spherical aberration signal is the difference between the defocus inside the beam and the defocus outside the beam, if the inner and outer defocus due to wavelength variation are equal, they will be canceled by calculation, but the intersection 54 between the optical axis and the light receiving element and each Since the angles formed by the lines connecting the light receiving patterns and the dividing lines dividing the light receiving patterns are different for each light receiving pattern, the inner and outer defocus due to wavelength fluctuations are not equal.

  FIG. 18C shows a case where the two light receiving patterns arranged on the outside are arranged on the right side of the drawing and the two light receiving patterns arranged on the inside are arranged on the left side of the drawing. Similarly to the case of FIG. 18A, the interval between the light receiving patterns 51b and 51a that receive the inside of the beam is equal to the interval between the light receiving patterns 51d and 51c that receive the outside of the beam, and further, the inside of the beam is received. Since the light receiving patterns and the light receiving patterns that receive the beam outside are alternately arranged, there always exists a rotation center 53 in which the defocus sensitivities on the inside and outside of the beam by rotation adjustment are equal to each other. In addition, when wavelength variation occurs, a spot on each light receiving pattern moves along a line connecting the intersection 54 of the optical axis and the light receiving element and each light receiving pattern, and the spot on each light receiving pattern is either left or right in the drawing. The light receiving area is biased.

  In this case, for example, when the spot is biased in the light receiving area 51bB in the light receiving pattern 51b, the light receiving pattern 51a is biased in the light receiving area 51aB as in the case of FIG. 18B described above, but in the light receiving pattern 51d, the light receiving area 51dA. In addition, the light receiving pattern 51c is biased toward the light receiving area 51cA. Therefore, the calculation of the focus error signal has a cancellation effect and the offset of the focus error signal is small. However, since the spherical aberration signal is a differential between the defocus inside the beam and the defocus outside the beam, there is no cancellation effect. Cause an offset.

  In FIG. 18 (d), the light receiving patterns 51b and 51a for receiving the inner area of the beam are offset to the right side of the paper, and the light receiving patterns 51d and 51c for receiving the outer area of the beam are offset to the left side of the paper. Show the case. This arrangement is equivalent to the arrangement of the light receiving patterns 51b and 51d and the light receiving patterns 51a and 51c arranged side by side in FIG. 18A. In this case, if the center point of the four light receiving patterns is the rotation center 53, defocus adjustment by rotation can be performed. In addition, when wavelength variation occurs, a spot on each light receiving pattern moves along a line connecting the intersection 54 of the optical axis and the light receiving element and each light receiving pattern, and the spot on each light receiving pattern is either left or right in the drawing. The light receiving area is biased. In this case, for example, when the spot is deviated in the light receiving area 51bB in the light receiving pattern 51b, the light receiving pattern 51a is deviated in the light receiving area 51aA, so the influence is small due to the effect of canceling both the focus error signal and the spherical aberration detection signal. However, as the defocusing of the optical disc 10 progresses, the spots on each light receiving pattern become a semicircular beam and expands in the horizontal direction in the figure, and finally reaches the horizontal light receiving pattern for a very large defocus. May disturb the signal.

  19 (a) to 19 (d) show the dividing line of the light receiving pattern between the optical axis and the light receiving element in order to solve the problem due to the wavelength variation described in FIGS. 18 (a) to (d). The case where it is made parallel to the line which connects the intersection 54 and a light reception pattern is shown in figure. In this case, even when the wavelength variation occurs, the spot on the light receiving pattern moves on the dividing line, so that the focus error signal and the spherical aberration detection signal are not offset at all. However, if the dividing line is slanted in this way, a very high light receiving element adjustment accuracy is required in the vertical direction in the figure, and this adjustment may be very difficult in consideration of variations in spot positions on the light receiving element. is expected.

  Even when a short wavelength laser including a blue laser is used, the present invention can be used as an optical pickup device that is small and thin, has good resistance to environmental change such as temperature change, and is low in cost.

The perspective view which shows the optical pick-up apparatus in one embodiment of this invention The perspective view which shows the composite element in one embodiment of this invention Sectional drawing which shows the composite element in one embodiment of this invention The perspective view which shows the relationship between the hologram pattern of the reflection type hologram in one embodiment of this invention, and the light reception pattern of a light receiving element The figure which shows the simple equivalent optical system of the optical pick-up apparatus in one embodiment of this invention The figure which shows the change of a return light when the optical disk of the optical pick-up apparatus in one embodiment of this invention leaves | separates from an objective lens. The figure which shows the change of return light when the optical disk of the optical pick-up apparatus in one embodiment of this invention approaches an objective lens The figure which shows the equivalent optical system of the integrated optical element also including the polarization separation film of the optical pick-up apparatus in one embodiment of this invention The figure which shows the defocus adjustment method of the optical pick-up apparatus in one embodiment of this invention The figure explaining an example of the spherical aberration correction means of the optical pick-up apparatus in one embodiment of this invention The figure explaining the phase distribution of the aberration of the optical pick-up apparatus in one embodiment of this invention The figure which shows distribution of (PHI) (R) when the spherical aberration of the optical pick-up apparatus in one embodiment of this invention generate | occur | produces The figure which shows the spherical aberration detection means in the state in which spherical aberration has not generate | occur | produced in the optical system of the optical pick-up apparatus in one embodiment of this invention, and there is no defocus on the optical disk recording surface The figure which shows the mode of the spherical aberration detection signal when spherical aberration actually generate | occur | produces in the optical pick-up apparatus in one embodiment of this invention The figure explaining the defocusing adjustment method also provided with the spherical aberration detection function of the optical pick-up apparatus in one embodiment of this invention The figure which shows the position change of the spot on each light reception pattern when the wavelength of the optical pick-up apparatus in one embodiment of this invention fluctuates The figure which shows an example at the time of detecting a focus error signal and a spherical aberration detection signal each independently The figure which shows the case where each light reception pattern has been arranged off the straight line The figure which shows the case where the division line of a light reception pattern is made parallel to the line which connects the intersection of an optical axis and a light receiving element, and a light reception pattern in order to solve the subject by wavelength variation.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Optical pick-up 10 Optical disk 11 Light source 12 Collimator lens 14 Raising mirror 15 Objective lens 18 Actuator 19 Pickup base 21 Spot on disk 21p Mirror image of spot on disk 21m Mirror image of spot on disk 21ip Mirror image of spot on disk 21im Spot of disk on disk Mirror image 21op Mirror image of spot on disk 21om Spot image on disk 22a Spot on light receiving element 22b Spot on light receiving element 22c Spot on light receiving element 22d Spot on light receiving element 22e Spot on light receiving element 22f Spot on light receiving element 22ap Spot on light receiving element 22am Light reception Spot on element 22 bp Spot on light receiving element 22 bm Spot on light receiving element 22 asap Spot on light receiving element 22 asam Spot on optical element 22 bsap Spot on light receiving element 22 bsam Spot on light receiving element 22 csap Spot on light receiving element 22 csam Spot on light receiving element 22 dsap Spot on light receiving element 22 dsam Spot on light receiving element 24 a Outbound light 24 b Return path light 24 bo Return path light 24 bo Return path light 24 bo Return path light 24 bo Composite element 31 Semiconductor laser 32 Base member 33 Coupling member 35 Flexible cable 40 Integrated optical member 41 Polarization separation film 42 Reflective hologram 42a Hologram area 42b Hologram area 42c Hologram area 42d Hologram area 42e Hologram area 42f Hologram area 50 Light receiving element 51a Light receiving pattern 51b Light reception pattern 51c Light reception pattern 51d Light reception pattern 51e Light reception pattern 51f Light reception Turn 51aA Light receiving area 51aB Light receiving area 51bA Light receiving area 51bB Light receiving area 51cA Light receiving area 51cB Light receiving area 51dA Light receiving area 51dB Light receiving area 51eA Light receiving area 51eB Light receiving area 51eA2 Light receiving area 51eB2 Light receiving area 51fA Light receiving area 51fA Light receiving area 51fA Electrical signal V51aB Electrical signal V51bA Electrical signal V51cB Electrical signal V51cA Electrical signal V51cB Electrical signal V51dA Electrical signal V51dB Electrical signal V51eA Electrical signal V51eB Electrical signal V51eA2 Electrical signal V51eB2 Electrical signal V51fA Electrical signal V51fB Electrical signal V51fB Electrical signal V51fB Electrical signal V51fB Center of rotation 54 Intersection of optical axis and light receiving element

Claims (17)

An optical pickup apparatus having a condensing optical system for condensing a light beam onto an optical recording medium and a light detection optical system for detecting reflected light from the optical recording medium, the light being disposed in the light detection optical system Optical path changing means for changing the light traveling direction for each of at least four regions divided by a line dividing the inner side and the outer side of the reflected light from the optical recording medium around the axis and a straight line including the optical axis. An optical pickup device comprising: a light receiving means provided with at least four light receiving portions arranged along a straight line parallel to a straight line including an optical axis that divides the optical path changing means disposed in the detection optical system. . The light receiving unit of the light receiving unit includes at least two light receiving elements each divided by a dividing line parallel to a straight dividing line including the optical axis of the optical path changing unit, and the light receiving unit includes at least eight light receiving elements. The optical pickup device according to claim 1, which is configured. The light path changing means condenses the light in one region inside the reflected light from the optical recording medium on the dividing line of the first light receiving part which is the light receiving part of the light receiving part of the light receiving means. The light in the same region outside the reflected light from the recording medium is collected on the dividing line of the second light receiving unit that is the light receiving unit adjacent to the first light receiving unit, and is reflected on the inner side of the reflected light from the optical recording medium. The light in the other region is condensed on the dividing line of the third light receiving unit which is the light receiving unit adjacent to the second light receiving unit, and the other light outside the reflected light from the optical recording medium is transmitted from the third light receiving unit. 3. The optical pickup device according to claim 2, wherein the optical path is changed so that the light is condensed on a dividing line of a fourth light receiving unit which is an adjacent light receiving unit. In the light receiving means, the signal output of the light receiving element on one side of the first light receiving unit which is the farthest light receiving unit, and the same one side of the second light receiving unit which is the light receiving unit adjacent to the first light receiving unit The signal output of the light receiving element, the signal output of the light receiving element on the other side of the third light receiving part, which is the light receiving part adjacent to the second light receiving part, and the fourth light receiving part, which is the light receiving part adjacent to the third light receiving part. A signal output obtained by adding the signal outputs of the light receiving elements on the other side of the same part,
The signal output of the light receiving element on the other side of the first light receiving unit which is the most light receiving unit, the signal output on the same other side of the second light receiving unit which is the light receiving unit adjacent to the first light receiving unit, The signal output of the light receiving element on one side of the third light receiving unit, which is the light receiving unit next to the second light receiving unit, and the light reception on the same side of the fourth light receiving unit, which is the light receiving unit next to the third light receiving unit. 4. The optical pickup device according to claim 3, wherein a difference between the signal outputs obtained by adding the signal outputs of the elements is used as the focus control signal for the light beam. In the light receiving means, the signal output of the light receiving element on one side of the first two light receiving units and the fourth light receiving unit on the outer side, the second light receiving unit and the third light receiving unit on the inner two light receiving units. A signal output obtained by adding the signal outputs of the light receiving elements on the other side of the unit,
The signal output of the light receiving element on the other side of the first light receiving unit and the fourth light receiving unit which are the two outer light receiving units, and one side of the second light receiving unit and the third light receiving unit which are the two inner light receiving units 4. The optical pickup device according to claim 3, wherein a spherical aberration control signal is obtained by a differential of the signal output obtained by adding the signal outputs of the light receiving elements. As the condensing optical system, a light source, parallel light converting means for converting light emitted from the light source into parallel light, and condensing light beams for condensing the parallel light emitted from the parallel light converting means onto an optical recording medium. 2. The optical pickup device according to claim 1, further comprising means. 7. The optical pickup device according to claim 6, wherein a semiconductor laser is used as the light source. 7. The optical pickup device according to claim 6, wherein a lens is used as the parallel light converting means. The optical pickup device according to claim 6, wherein a lens is used as the condensing unit. The detection optical system includes: an optical phase conversion unit that converts light from linearly polarized light into circularly polarized light; a polarization separation unit that separates light according to a polarization direction; an optical path conversion unit; and a light receiving unit. Item 5. The optical pickup device according to Item 1. 11. The optical pickup device according to claim 10, wherein a diffractive optical element is used as the optical path changing means. 11. The optical pickup device according to claim 10, wherein a polarizing diffractive optical element is used as the optical path changing means. 11. The optical pickup device according to claim 10, wherein a photodiode is used as the light receiving means. 11. The optical pickup device according to claim 10, wherein a quarter wave plate is used as the optical phase converting means. 11. The optical pickup device according to claim 10, wherein a polarization separation film is used as the polarization separation means. 11. The optical pickup device according to claim 10, wherein the polarized light separating means and the optical path changing means are the same optical integrated member. 17. The optical pickup device according to claim 16, wherein the light source, the light receiving means, and the optical integrated member are the same composite element.

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