JP2006092606A - Optical pickup device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical pickup device in which tracking adjustment is easily conducted by a tracking signal whose offset voltage is eliminated, even though the position of a lens 6 is moved with respect to an optical recording medium 8. <P>SOLUTION: The optical pickup device conducts tracking control and has: a semiconductor laser 1; a condenser lens 6; a composite diffraction element 10 which has a plurality of diffraction divided surfaces that receive reflected light beams 13 being reflected from an optical recording medium 8, diffracted and generated and diffract and divide the beams 13 into a plurality of light beams; an optical detector 11 which receives the plurality of diffracted and divided light beams so as to convert the beams into electric signals; and a push-pull circuit 14 which receives electric signals from the optical detector 11 and outputs a tracking signal. The composite diffraction element 10 having the plurality of diffraction divided surfaces, divides the portion where the zero-order light beams and the ±first-order light beams among the reflected light beams 13 generated from the optical recording medium 8 are overlapped, into two, and emits the one to the optical detector 11 and the other to the outside of the optical detector 11, and also emits only the portion of all zero-order light beams of the reflected light beams 13 generated from the optical recording medium 8 to the optical detector 11. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an optical pickup device for recording and reproducing an image and information on an optical disk as an optical recording medium, and an operation method thereof.

FIG. 8 shows an outline of a conventional optical pickup device and will be described.
This optical pickup device includes a laser 1 composed of a semiconductor laser element that generates a light beam 12, a lens 2 that converts the light beam 12 into parallel light, a light beam 12 from the direction of the laser 1, and a light beam from the opposite direction. Operates the reflecting prism 3, the total reflection mirror 4 that changes the optical path of the light beam, the λ / 4 plate 5 that circularly polarizes the laser light, the lens 6 that condenses the light beam 13, and the lens 6. Moving coil 7 to be combined, optical disk 8 used as an optical recording medium for recording images and information, lens 9 for condensing reflected light 13, diffractive element 10 ′ for receiving and diffracting reflected light 13, and diffracted reflected light 13 And a push-pull circuit 14 that receives an electrical signal output from the photodetector 11 and outputs a tracking signal. .

  First, the light beam 12 emitted from the laser 1 is made into parallel light by the lens 2, passed through the polarizing prism 3, reflected by the total reflection mirror 4 in the direction of the optical disk 8, and then the λ / 4 plate. The light is circularly polarized by 5 and condensed on the recording surface of the optical disk 8 by the lens 6. The lens 6 is moved by the moving coil 7 and aligns the position of the light beam with the track (guide groove) of the optical disk 8.

On the recording surface of the optical disc 8, a guide groove called a groove is provided on the optical disc 8 so that the condensing spot of the light beam 12 collected by the lens 6 can always follow a predetermined radial position. Yes.
The light beam 12 reflected by this guide groove becomes reflected light 13 composed of 0th-order diffracted light, −1st-order diffracted light, and + 1st-order diffracted light, and passes through the lens 6, λ / 4 plate 5, and total reflection mirror 4. The reflected light 13 totally reflected by the polarizing prism 3 is collected by the lens 9, diffracted by the diffraction element 10 ′, and received by the photodetector 11.

The photodetector 11 includes four photodetectors A, B, C, and D, converts the reflected light of the received light beam into two electrical signals and outputs them.
These two electrical signals are sent to the push-pull circuit 14 as an addition signal from the photodetecting units C and D and from the push-pull circuit 14, and output a tracking signal TE from the push-pull circuit 14. If this tracking signal TE is reflected at the center of the guide groove of the optical disc 8, TE = 0.

If the reflected light deviates from the center of the guide groove, a differential voltage is generated in the tracking signal TE. The generated voltage is sent to the moving coil 7 as a control signal to move the lens 6 and move it to the center of the guide groove. Make tracking adjustments.
In this way, the center of the focused spot focused by the lens 6 is always aligned with the center of the groove.

The size of the zero-order diffracted light in the photodetector 11 is set so as to detect almost 100%. That is, the photodetector is set to the dimension of the photodetector width W0 laterally with respect to the 0th-order diffracted light diameter D0 and the photodetector length L0 longitudinally, but D0 <W0, L0 in order to sufficiently receive the reflected light. And
As a specific example, the size of the photodetector 11 is 6000λ (λ: wavelength of light, for example, set to 650 nm) in both the vertical and horizontal directions.

  FIG. 9 shows an example of the distribution of the 0th-order light, the −1st-order light, and the + 1st-order light by the reflected light 13 reflected by the optical disk 8 irradiated on the photodetector 11. On the photodetector 11, as shown in FIG. 10 (1), A1, A2, C1, and C2 are portions of only the 0th order light, B1 and B2 are portions where the 0th order light and the −1st order light are superimposed, D1 , D2 are portions where the 0th-order light and the + 1st-order light are superimposed. As shown in FIG. 10B, the −1st-order light is the E portion and the + 1st-order light is the F portion.

  Then, when the outputs of the photodetectors 11 divided into four photodetectors are combined into two on the left and right and input to the push-pull circuit 14 to detect the tracking signal TE, the light incident on the track on the optical disk 8 And -1st order light and + 1st order light are AC components that do not include an offset component, whereas light incident on the optical disc 8 is directly reflected light. The zero-order light is mainly offset. This offset changes with the inclination between the lens 6 and the optical disk 8.

  If the zero-order light part is divided into left and right parts, the positions are optimally adjusted by half, but if there is an inclination between the lens 6 and the optical disk 8, the offset is different between the inner and outer peripheral sides of the optical disk. Come.

  For this reason, as shown in FIG. 10 (3), D = D1 + D2 on the right side is the 0th order light and is a portion superimposed on the + 1st order light F, B = B1 + B2 on the left side is the 0th order light, and the −1st order light E Since the offset due to the right half 0th order light (D) and the left half 0th order light (B) is different, it is incident on the photodetector 11 and pushed by the push-pull circuit 14. When converted into an electrical signal and the difference is taken to make the tracking signal TE = (E + B) − (F + D), as shown in FIG. 10 (4), the offset of the tracking signal TE does not become 0, and as a result, malfunction occurs when adjusting the track position. Is produced.

It is described in FIG. 5 and FIG. 10 of Patent Document 1 that the offset voltage varies as described above.
As for the diffractive element, as described in Patent Document 1, a diffractive portion is provided on only one surface. Therefore, in order to adjust the offset, it is necessary to add lenses having various shapes as described in Patent Document 1.
JP 2003-123279 A

  However, as described above, the reflected light 13 obtained by reflecting the light beam 12 from the optical disk 8 with the conventional standard-shaped photodetector 11 shown in FIG. When the next light is generated and passed through the diffractive element 10 ′ and received by the photodetector 11 to obtain the tracking signal in addition to the push-pull circuit 14 shown in FIG. 8, it can be seen from the graph of FIG. As described above, when the lens 6 and the optical disk 8 are tilted, the offset voltage (DC component) included in the tracking signal increases as the position of the lens 6 with respect to the optical disk 8 moves, so that tracking adjustment becomes difficult. there were.

  Accordingly, the present invention has been made to solve the above-described problems, and an object thereof is to provide an optical pickup device capable of performing easy tracking adjustment without being affected by an offset voltage, and an operation method thereof. To do.

As means for achieving the above object, the present invention provides a semiconductor laser for emitting a light beam to be applied to an optical recording medium, and a light spot emitted from the semiconductor laser to generate a condensed spot. A condenser lens that irradiates the optical recording medium; a diffraction element that diffracts the reflected light reflected from the optical recording medium; and a plurality of divided regions that receive the diffracted light diffracted by the diffraction element. An optical pickup device having a photodetector for photoelectric conversion and a push-pull circuit for obtaining a tracking signal from an electrical signal photoelectrically converted by the photodetector, wherein the diffractive element reflects reflected light from the optical recording medium. A first diffractive refractive surface that diffracts and refracts the reflected light and divides the reflected light into zero-order light and ± first-order light, and the zero-order light branched by the first diffractive refracting surface; ± primary light is incident The other surface is a light shielding region at the center, and the region excluding the light shielding portion in the diameter direction is divided by a first straight line and two parallel lines parallel to the straight line across the light shielding portion, and the light shielding portion A region in the diametrical direction between the outer peripheral portion and excluding the light-shielding portion is divided by a second straight line orthogonal to the first straight line, and the first to first directions seen from the clockwise direction around the second straight line. And the first, fourth, fifth, and eighth diffractive refractive regions are irradiated with zero-order light branched in the first diffractive refractive region, and the photodetector includes: A first light-receiving region that receives one of the zero-order light and the ± first-order light branched in the second diffractive-refractive region, and the zero-order light and the ± first-order light branched in the third diffractive-refractive region. Either a second light receiving region that receives one of the light, a zero-order light or a ± first-order light branched in the sixth diffractive refractive region And a fourth light receiving region for receiving either the 0th order light or the ± first order light branched in the seventh diffractive refractive region, and the first, fourth, There is provided an optical pickup device characterized in that zero-order light emitted from the fifth and eighth diffraction regions is received by the first to fourth light receiving regions.
The second invention irradiates an optical recording medium with a light beam emitted from a semiconductor laser, condenses the light beam to generate a condensing spot, irradiates the optical recording medium with a condensing lens, The reflected light reflected from the optical recording medium is diffracted by a diffractive element to generate diffracted light, and then has a plurality of divided regions, receives the diffracted light and photoelectrically converts it by a photodetector. The method of operating an optical pickup device that obtains a tracking signal from an electrical signal photoelectrically converted by the diffractive element, wherein the diffraction element diffracts the reflected light and refracts the one surface on which the reflected light from the optical recording medium is incident. A first diffractive surface splitting into 0th order light and ± 1st order light, and the other surface on which the 0th order light and ± 1st order light split by the first diffractive refractive surface is incident is shielded at the center. The first straight line is the area and the area excluding the light shielding portion in the diameter direction. And a region which is divided by two parallel lines sandwiching the light shielding portion and parallel to the straight line, and which is in a diametrical direction between the light shielding portion and the outer peripheral portion and excluding the light shielding portion is orthogonal to the first straight line. The first, fourth, fifth, and eighth diffractive refractive regions are divided by two straight lines and viewed in the clockwise direction around the second straight line. The first-order light branched in the first diffractive refractive region is irradiated, and the photodetector receives either the zero-order light or ± first-order light branched in the second diffractive refractive region. A light-receiving region, a second light-receiving region that receives one of the zero-order light and the ± first-order light branched in the third diffractive-refractive region, and the zero-order light that is branched in the sixth diffractive-refractive region and ± A third light-receiving region that receives one of the primary lights, a zero-order light and a ± first-order light branched by the seventh diffractive refractive region. A fourth light receiving region that receives one of the shifts, and the first to fourth light receiving regions receive zero-order light emitted from the first, fourth, fifth, and eighth diffraction regions. An operation method of the optical pickup device is provided, wherein the tracking signal is obtained by calculating zero order light and ± first order light received in the first to fourth light receiving regions.

  According to the present invention, the diffractive element has a first diffractive refraction in which one surface on which the reflected light from the optical recording medium is incident diffracts and refracts the reflected light and branches into 0th order light and ± first order light. The other surface on which the 0th-order light and the ± 1st-order light branched by the first diffractive refracting surface are incident is a light-shielding region in the center, and the region excluding the light-shielding portion is in the diameter direction. A straight line and two parallel lines that are parallel to the straight line with the light-shielding part interposed therebetween, and a region that is in the diametrical direction between the light-shielding part and the outer peripheral part and that excludes the light-shielding part is orthogonal to the first straight line The first, fourth, fifth, and eighth diffractive refractive regions are divided by the second straight line, and viewed in the clockwise direction around the second straight line. Are irradiated with 0th-order light branched in the first diffractive refraction region, and the photodetector detects the second diffractive refraction region. A first light-receiving region that receives one of the zero-order light and the ± first-order light branched in the region, and one of the zero-order light and the ± first-order light branched in the third diffractive refractive region A second light-receiving region, a third light-receiving region that receives one of the zeroth-order light and the ± first-order light branched in the sixth diffractive-refractive region, and the zeroth-order branched in the seventh diffractive-refractive region. And a fourth light-receiving region that receives either one of the light and the ± first-order light, and the 0th-order light emitted from the first, fourth, fifth, and eighth diffraction regions Since it is configured to receive light in the four light receiving regions, it is not affected by the offset voltage, so that easy tracking adjustment can be performed.

  Hereinafter, an optical pickup device according to an embodiment of the present invention will be described with reference to FIGS. FIG. 1 is a diagram showing an outline of an optical pickup device according to an embodiment of the present invention. FIG. 2 is a diagram showing a diffraction-divided light pattern on each diffraction surface in the composite diffraction element 10 and on the surface of the photodetector 11. FIG. 3 is a diagram showing a diffraction division state of the optical path of the diffraction division light with respect to the incident light of the composite diffraction element 10. FIG. 4 is a diagram showing outline dimensions of the composite diffraction element 10 and the photodetector 11. FIG. 5 is a diagram showing the dimensions and details of the diffraction-divided light pattern on the second diffraction surface of the composite diffraction element 10 and the surface of the photodetector 11. FIG. 6 shows the amount of light on the photodetector 11 when the optical disk 8 is tilted. FIG. 7 is a diagram showing an example of a tracking signal and a combined signal of each part of the diffraction-divided light pattern shown in FIG.

  As shown in FIG. 1, an optical pickup device according to an embodiment of the present invention collects a semiconductor laser 1 for emitting a light beam 12 for irradiating an optical recording medium 8 and a light beam 12 emitted from the semiconductor laser 1. A condensing lens 6 that generates light and generates a condensing spot and irradiates the optical recording medium 8, and a plurality of diffractions that receive the reflected light 13 that is reflected and diffracted from the optical recording medium 8 and diffracts and divides it into a plurality of lights A composite diffractive element 10 having a split surface, a photodetector 11 that receives a plurality of diffracted split beams and converts them into an electrical signal, and a push-pull circuit 14 that receives an electrical signal from the photodetector 11 and outputs a tracking signal. And a composite diffractive element 10 having a plurality of diffraction division surfaces is reflected and diffracted from the optical recording medium 8. The portion where the 0th order light and the ± 1st order light overlap in the generated reflected light 13 is divided into two, one is emitted to the photodetector 11 and the other is emitted outside the photodetector 11, All of the portion of the reflected light 13 reflected and diffracted from the optical recording medium 8 and only the zero-order light is emitted to the photodetector 11.

  Next, the outline of the optical pickup device will be described and explained in detail with reference to FIG. This optical pickup device includes a laser 1 composed of a semiconductor laser element that generates a light beam 12, a lens 2 that converts the light beam 12 into parallel light, a light beam 12 from the direction of the laser 1, and a light beam from the opposite direction. Operates the reflecting prism 3, the total reflection mirror 4 that changes the optical path of the light beam, the λ / 4 plate 5 that circularly polarizes the laser light, the lens 6 that condenses the light beam 13, and the lens 6. A moving coil 7 to be combined, an optical disk 8 used as an optical recording medium for recording images and information, a lens 9 for condensing the reflected light 13, and a composite diffractive element 10 for receiving the reflected light 13 and diffracting it into a plurality of diffracted light beams. , Comprising a photodetector 11 and a push-pull circuit 14 that receive the reflected light 13 diffracted and divided into a plurality of diffracted light beams and convert it into an electrical signal.

  Then, the light beam 12 emitted from the laser 1 is collimated by the lens 2 and passed through the polarizing prism 3, and then reflected by the total reflection mirror 4 in the direction of the optical disk 8, then λ / It is circularly polarized by the four plates 5 and condensed on the recording surface of the optical disk 8 by the lens 6. The lens 6 is moved by the moving coil 7 and aligns the position of the light beam with the track (guide groove) of the optical disk 8.

  Next, on the recording surface of the optical disc 8, a guide groove called a groove is provided on the optical disc 8 so that the condensing spot of the light beam 12 collected by the lens 6 can always follow a predetermined radial position. Is provided. The light beam 12 reflected by this guide groove becomes reflected light 13 composed of 0th-order diffracted light, −1st-order diffracted light, and + 1st-order diffracted light, and passes through the lens 6, λ / 4 plate 5, and total reflection mirror 4. The reflected light 13 totally reflected by the polarizing prism 3 is collected by the lens 9, further divided into a plurality of diffracted lights by the composite diffraction element 10, and received by the photodetector 11.

  As shown in FIG. 1, the reflected light 13 is condensed by the lens 9, converted into a predetermined diffraction division light pattern by the composite diffraction element 10, and projected onto the photodetector 11. The photodetector 11 includes four photodetectors A, B, C, and D, converts a plurality of received diffraction split lights into two electrical signals, and outputs the signals. For example, a model name CXA2674EM (manufactured by SONY) is commercially available for the photodetector 11 under the name of PDIC, and these two electric signals are obtained by adding the addition signal of the photodetectors C and D and the addition signal of the photodetectors A and B, respectively. The signal is sent to the push-pull circuit 14 in the photodetector 11 and the tracking signal TE is output from the push-pull circuit 14. If this tracking signal TE is reflected at the center of the guide groove of the optical disc 8, TE = 0.

  Then, the tracking signal TE is applied to the moving coil 7 and the lens 6 is operated to move the position of the light beam 12 to a position where the tracking signal TE indicating the optimum position of the groove groove of the optical disk 8 is zero. The coil 7 is operated to move.

  That is, if the reflected light deviates from the center of the guide groove, a differential voltage is generated in the tracking signal TE. The generated voltage is sent to the moving coil 7 as a control signal, and the lens 6 is moved and moved to the center of the guide groove. Make tracking adjustments. In this way, the center of the focused spot focused by the lens 6 is always aligned with the center of the groove.

  Next, as shown in FIG. 2 (1), the diffracted light by the reflected light from the optical disc is incident light obtained by superimposing only the 0th-order light, the 0th-order light, and the first-order light. 2 is irradiated with a first diffraction surface as shown in FIG. 2 (2), and then divided into a plurality of diffraction surfaces as shown in FIG. 2 (3). Further, a plurality of diffracted light beams that are diffracted and diffracted by the photodetector 11 in a predetermined diffraction divided pattern are irradiated.

FIG. 3 shows an optical path of each pattern portion that is diffracted and divided by the second diffraction surface shown in FIG. The central portions S11, S12 and S21, S22 are divided into two so as to intersect left and right, one of the divided portions is irradiated to the photodetector 11, and the other one is irradiated to the outside of the photodetector 11. .
The front and rear portions S13, S14 and S23, S24 are divided into two parts, but all are irradiated to the photodetector 11.

  At this time, the patterns S11 and S12 in the central portion are irradiated on the light detection portions A and B of the left photodetector 11 which are the same as the front and rear portions S23 and S24, and the patterns S21 and S22 in the other central portion are the front and rear portions. Are irradiated on the light detection units C and D of the right-side photodetector 11 as in S13 and S14.

  The diffraction grating spacings P0 and P1 between the first diffraction surface and the second diffraction surface of the composite diffraction element 10 shown in FIG. 2 (1) are approximately 1 μm to 3 μm, and the groove depth t0 is approximately 1 μm to 3 μm. As shown in FIG. 4, the thickness D0 of the composite diffraction element 10 is about 20 μm to 100 μm, and the distance between the composite diffraction element 10 and the photodetector 11 is set to a range of about 100 μm to 300 μm.

  Then, according to the dimensional configuration of each diffraction surface of the composite element 10 shown in FIG. 4, the incident light A and the incident light B projected onto the composite diffraction element 10 are divided by half into the photodetector 11 by the first and second diffraction surfaces, respectively. And projected. FIG. 5 shows the dimensions of the patterns on the second diffraction surface and the dimensions of the photodetector 11.

The movement of each pattern will be described in more detail. As shown in FIG. 5 (A), the diffraction-divided light pattern on the second diffractive surface is diffracted and divided by the second diffractive surface for each portion. As shown in FIG.
For example, S11 in which 0th-order light and primary light are superimposed is diffracted and divided to the left and right, and is irradiated as S11 to the position of the light detection unit A of the light detector 11. Irradiated. Similarly, S12, S21, and S22 in which the 0th-order light and the 1st-order light are superimposed are also diffracted and divided on the left and right sides, and irradiated to the photodetector 11 as shown in FIG. 5B.
On the other hand, S13, S14, S23, and S24 of only the 0th order light are diffracted and divided in the front and rear directions, and the light diffracted and divided into these two is all irradiated to the light detection portions of the different photodetectors 11, respectively. In the case of only the 0th-order light, it may be used as it is without being divided by diffraction.

  The dimensions of the diffraction division pattern on the second diffraction surface are the areas S11, S12, S21, where the zero-order light and the ± first-order light from the guide groove of the optical disc 8 overlap with the spot light diameter 6000λ of the reflected light 13. S22 is approximately width 2000λ × height 2000λ, and regions S13, S14, S23, and S24 outside the zero-order light only by the guide groove of the optical disk 8 are approximately width 3000λ × height 1000λ (λ: wavelength of laser light to be used) ). The photodetector 11 is 130 μm wide × 130 μm high.

  Next, as shown in FIG. 7, the light of each part of the pattern on the second diffractive surface is incident on the photodetector 11 and converted into an electrical signal, and the level of each pattern converted into this electrical signal is tracked. A case where the signal TE is used will be described.

First, the amount of zero-order light irradiated on each pattern in FIG. 5A is set as shown in FIG. 7A. → A1: S23, A2: S24, B1: S21, B2: S22, C1: S13, C2: S14, D1: S11, D2: From S12, A = A1 + A2, B = B1 + B2, C = C1 + C2, D = D1 + D2. . Moreover, when the light quantity ratio of the 0th-order light of each pattern was measured, they were A = B / 2 and C = D / 2.
As shown in FIG. 7B, the −1st order light is E: S21 + S22, and the + 1st order light is F: S11 + S12.

  As shown in FIG. 6, when the optical disk 8 is tilted, the zero-order light as reflected light of the optical disk that reaches the photodetector 11 has a difference in light quantity depending on the positions of the inner half and the outer half. That is, as shown in FIG. 6, when the inner half is closer to the photodetector 11, the amount of light on the inner half is larger.

  As shown in the graph of FIG. 7 (3), the light amount of the portion where the 0th-order light and the + 1st-order light are superimposed is F + D, and the light amount of the portion where the 0th-order light and the −1st-order light is superimposed is E + B. When irradiated to the vessel 11, the graph shown in FIG. 7 (3) is obtained. At this time, as shown in FIG. 5B on the second diffractive surface, the overlapped portion of the 0th-order light and the −1st-order light, the 0th-order light and the − + 1st-order light is divided into half and irradiated to the photodetector 11. Then, as shown in FIG. 7 (4), each becomes a graph of half light quantity. Then, as shown in FIG. 7 (1), a graph of the amount of light when the 0th-order light is A and C is shown in FIG. 7 (4).

  When the 0th-order light and the 0th-order light and the 0th-order light and the 0th-order light are irradiated to the light detection unit of the photodetector 11 according to each pattern configuration of FIG. (F + D) / 2 by the next-order light and + 1st-order light and A of only the 0th-order light are added, and (E + B) / 2 by the 0th-order light and -1st-order light and C of only the 0th-order light are added. This is shown in the graph of FIG.

  In this way, assuming that the amount of 0th-order light is A = B / 2 and C = D / 2 as shown in FIG. 7A, (F + D) / 2 + A = F / 2 + A + C, (E + B) / 2 + C = E / 2 + A + C, and the amount of each zero-order light becomes equal. If this is converted into an electrical signal by the photodetector 11 and converted into a differential signal by the push-pull circuit 14, A + C for the 0th-order light is deleted.

  This is because if there is an inclination between the lens 6 and the optical disc 8, a difference in the amount of light occurs between the inner periphery and the outer periphery of the optical disc, so that the amount of offset differs. As a result, the amounts of light of A and C in the 0th order light differ. However, the light quantity of the 0th order light irradiated to the left and right light detection units of the photodetector 11 becomes equal by switching the 0th order light components B and D in the central part to the left and right in this way. If the difference is taken, the offset generated by the 0th order light is deleted as shown in FIG.

  As described above, the light detection unit 11 receives a predetermined pattern by halving a portion where the 0th-order light and the 1st-order light overlap each other among the plurality of diffraction-divided light beams that are diffracted into the front, back, left, and right by the composite diffraction element 10. By doing so, it is possible to easily obtain a tracking signal from which the offset (DC component) has been deleted.

It is a figure which shows the outline | summary of the optical pick-up apparatus which concerns on embodiment of this invention. FIG. 3 is a diagram showing a diffraction-divided light pattern on each diffraction surface in the composite diffraction element 10 and on the surface of the photodetector 11. 3 is a diagram showing a diffraction division state of an optical path of diffraction division light with respect to incident light of the composite diffraction element 10. FIG. FIG. 3 is a diagram showing dimensions of a composite diffraction element 10 and a photodetector 11. FIG. 3 is a diagram showing dimensions and details of a diffraction-divided light pattern on the second diffraction surface of the composite diffraction element 10 and the surface of the photodetector 11. The amount of light on the photodetector 11 when the optical disk 8 is tilted is shown. It is a figure which shows the tracking signal and synthetic | combination signal example of each part of the diffraction division | segmentation light pattern shown in FIG. It is a figure which shows the outline | summary of the conventional optical pick-up apparatus. It is a figure which shows distribution of the diffracted light on a photodetector. It is a figure which shows the tracking signal and synthetic | combination signal example of each part of the conventional diffraction division | segmentation light pattern.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Laser (semiconductor laser), 2 ... Lens, 3 ... Polarizing prism, 4 ... Total reflection mirror, 5 ... λ / 4 plate, 6 ... Lens (movable part), DESCRIPTION OF SYMBOLS 7 ... Moving coil, 8 ... Optical disk, 9 ... Lens, 10 ... Compound diffraction element, 10 '... Diffraction element, 11 ... Photodetector, 12 ... Light beam, 13 ... reflected light, 14 ... push-pull circuit

Claims (2)

A semiconductor laser for emitting a light beam for irradiating the optical recording medium; a condensing lens for condensing the light beam emitted from the semiconductor laser to generate a condensed spot and irradiating the optical recording medium; and the light A diffractive element that diffracts reflected light reflected from a recording medium, a photodetector that has a plurality of divided regions, receives diffracted light diffracted by the diffractive element, and performs photoelectric conversion; and An optical pickup device having a push-pull circuit for obtaining a tracking signal from the converted electric signal,
The diffractive element has a first diffractive refracting surface on which one surface on which reflected light from the optical recording medium is incident diffracts and refracts the reflected light and branches into zero-order light and ± first-order light, The other surface on which the 0th-order light and ± 1st-order light branched by the first diffractive refracting surface is incident is a light shielding region in the center, and the region excluding the light shielding portion in the diameter direction is the first straight line and the light shielding portion. Is divided by two parallel lines that are parallel to the straight line, and is divided by a second straight line that is in the diametrical direction between the light-shielding part and the outer peripheral part and that excludes the light-shielding part. And first to eighth diffracting / refracting regions when viewed in the clockwise direction around the second straight line, and the first, fourth, fifth, and eighth diffracting / refracting regions include the first diffracting region. The zero order light branched in the refraction area is irradiated,
The photodetector includes a first light-receiving region that receives one of the zero-order light and the ± first-order light branched in the second diffractive refractive region, and the zero-order light branched in the third diffractive refractive region. And a second light receiving region that receives one of ± first-order light, a third light-receiving region that receives one of zero-order light and ± first-order light branched in the sixth diffractive refractive region, A fourth light receiving region that receives either the 0th order light or the ± first order light branched in the seventh diffractive refractive region, and is emitted from the first, fourth, fifth, and eighth diffraction regions. An optical pickup device having a configuration in which the 0th-order light is received by the first to fourth light receiving regions. An optical recording medium is irradiated with a light beam emitted from a semiconductor laser, the light beam is condensed to generate a condensing spot, and the optical recording medium is irradiated with a condensing lens and reflected from the optical recording medium. The reflected light is diffracted by a diffractive element to generate diffracted light, and then has a plurality of divided regions. The diffracted light is received, photoelectrically converted by a photodetector, and photoelectrically converted by the photodetector. An operation method of an optical pickup device for obtaining a tracking signal from a signal,
The diffractive element has a first diffractive refracting surface on which one surface on which reflected light from the optical recording medium is incident diffracts and refracts the reflected light and branches into zero-order light and ± first-order light, The other surface on which the 0th-order light and ± 1st-order light branched by the first diffractive refracting surface is incident is a light shielding region in the center, and the region excluding the light shielding portion in the diameter direction is the first straight line and the light shielding portion. Is divided by two parallel lines that are parallel to the straight line, and is divided by a second straight line that is in the diametrical direction between the light-shielding part and the outer peripheral part and that excludes the light-shielding part. And first to eighth diffracting / refracting regions when viewed in the clockwise direction around the second straight line, and the first, fourth, fifth, and eighth diffracting / refracting regions include the first diffracting region. Irradiate zero-order light branched in the refraction area,
The photodetector includes a first light-receiving region that receives one of the zero-order light and the ± first-order light branched in the second diffractive refractive region, and the zero-order light branched in the third diffractive refractive region. And a second light receiving region that receives one of ± first-order light, a third light-receiving region that receives one of zero-order light and ± first-order light branched in the sixth diffractive refractive region, A fourth light receiving region for receiving either the 0th-order light or the ± first-order light branched in the seventh diffractive refractive region, and is emitted from the first, fourth, fifth, and eighth diffraction regions. Received zero-order light in the first to fourth light receiving regions,
An operation method of an optical pickup device, wherein the tracking signal is obtained by calculating 0th order light and ± 1st order light received in the first to fourth light receiving regions.

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