JP2001344771A - Hologram optical device, optical pickup device and optical recording medium driving device using the devices - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a hologram optical device and an optical pickup device, which are capable of correctly detecting a focus state in an optical recording medium even when a diffracting angle of a feedback luminous flux is changed by wavelength variations of a light source and to provide an optical recording medium driving device using them. SOLUTION: A hexapartite hologram surface 40 is parted into areas Ha, Hb, Hc, Hd, He, Hf by parting lines 4L, 4M, 4N. A quadripartite photodetecting part 60 is parted into four photodetecting parts A, B, C, D having an equal area by a dividing line LX nearly parallel to the radial direction of an optical disk 1 and a dividing line LY orthogonal to it. Main luminous flux diffracted by areas Ha, Hd of the hexapartite hologram surface 40 is condensed as light condensing spots Sa, Sd in respectively opposite side separate positions on the dividing line LX of the quadripartite photodetecting part 60, and a main luminous flux diffracted by areas Hb, Hc, He, Hf is condensed as light condensing spots Sb, Sc, Se, Sf in the center of the photodetecting parts A, D, C, B of the quadripartite photodetecting part 60.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hologram optical element, an optical pickup device using the same, and an optical recording medium driving device having the same.

[0002]

2. Description of the Related Art An optical pickup device used for an optical recording medium driving device such as an optical disk drive device uses a laser beam to record and read information on an optical recording medium such as an optical disk or to detect a servo signal.

[0003] The servo signal includes a focus error signal indicating a focus shift of a condensed spot of a laser beam on an optical recording medium and a tracking error signal indicating a shift of a condensed spot from a track on the optical recording medium. .

The astigmatism method is often used for detecting a focus error signal. On the other hand, for detection of a tracking error signal, a CD (Compact disc) and a CD-ROM (CD
In the case of a read-only optical disk such as -read only memory), the three-beam method is often used. CD-R (CD-r
In the case of a recordable optical disk such as an ecordable or CD-RW (CD-rewritable), the pit does not exist in an unrecorded state, so that the three-beam method cannot be used. The push-pull method is used.

FIG. 20 is a schematic view of a conventional optical pickup device for a recordable optical disk. The semiconductor laser element 302 emits a laser beam (light beam). The luminous flux emitted from the semiconductor laser element 302 is divided into the three-division diffraction grating 30.
3 divides the light into three light beams including a main light beam and two sub light beams, and converts the light into parallel light by a collimator lens 304. The three light beams transmitted through the collimator lens 304 are transmitted through the beam splitter 305, and
The light is focused on the recording medium surface of the optical disk 301 as a main spot and sub-spots located on both sides of the main spot.

The objective lens 306 is supported by an actuator 310 so as to be movable in a radial direction of the optical disk 301 for a tracking operation and movable in a direction perpendicular to the recording medium surface of the optical disk 301 for a focusing operation.

[0007] Three return light beams (reflected light beams) from the optical disk 301 pass through the objective lens 306, are reflected by the beam splitter 305, pass through the condenser lens 307 and the cylindrical lens 308, and pass through the photodetector 30.
9 is detected. At this time, astigmatism for focus error detection is given to the three return light beams by the combination of the condenser lens 307 and the cylindrical lens 308.

FIG. 21 is a schematic plan view showing an example of the photodetector 309 of FIG. FIG. 21A shows the objective lens 3.
FIG. 21B shows the state of the converged spot when the optical disc 301 is too close to the optical disc 301, and FIG.
Shows the state of the condensed spot when is located at the in-focus position of the objective lens 306, and FIG. 21C shows the state of the condensed spot when the optical disc 301 is too far from the objective lens 306.

[0009] As shown in FIG.
The quadrant photodetector 160 provided at the center and the bisection photodetectors 16 provided on both sides of the quadrant photodetector 160
1,162. The quadrant light detector 160 is divided into four photodetectors A, B, C, and D, and is divided into two photodetectors 16.
1 is divided into two photodetectors E1 and E2, and the two-divided photodetector 162 is divided into two photodetectors F1 and F2. At the center of the quadrant light detection unit 160, the optical disc 3
The main light beam among the three return light beams from the light source 01 is incident on the optical disc 30 at the center of the two-split light detection units 161 and 162.
The sub-beams of the return light beams from 1 are respectively incident.

When the distance between the optical disk 301 and the objective lens 306 changes, the focal point of the return light beam changes, and the light is focused on the four-divided light detector 160 and the two-divided light detectors 161, 162 of the photodetector 309. The shape of the spot changes as shown in FIG.

[0011] The optical disk 30 with respect to the objective lens 306
If 1 is too close, as shown in FIG. 21A, the condensed spot S has an elliptical shape in which the direction connecting the center of the light detection unit B and the center of the light detection unit D is the long axis direction. .

When the optical disk 301 is at the focal point of the objective lens 306, as shown in FIG.
The condensed spot S is circular at the center of the photodetectors A, B, C, and D.

When the optical disk 301 is too far from the objective lens 306, the condensed spot S is directed in the direction connecting the center of the light detecting section A and the center of the light detecting section C as shown in FIG. Becomes an elliptical shape in the long axis direction.

Therefore, the output signals PA, PB, PC, P of the respective photodetectors A, B, C, D of the quadrant photodetector 160
Using D, the following equation focus error signal FES is obtained.

FES = (PA + PC) − (PB + PD) (1) The focus error signal FES in the above equation becomes negative when the optical disc 301 is too close, and 0 when the optical disc 301 is in a good focus state.
And becomes positive when the optical disk 301 is too far.
As described above, the direction of the deviation from the in-focus position of the optical disc 301 can be determined based on the sign of the focus error signal FES.

The focus error signal FES is supplied to the actuator 31
This is fed back to 0, and by moving the objective lens 306 in a direction perpendicular to the optical disc 301, the light-collecting state on the optical disc 301 is corrected.

When the optical axis of the semiconductor laser element 302 is tilted, a bias in the light intensity distribution occurs in the focused spot of the photodetector 309 in the focused state. In the astigmatism method using the four-division light detection unit 160, the semiconductor laser element 30
Even when the light intensity distribution deviates in the condensed spot due to the inclination of the optical axis of 2, the focus error signal FES hardly causes an error.

FIG. 22 is a diagram for explaining the principle of tracking servo by the push-pull method and the differential push-pull method. 22 (a), (b) and (c) show the positional relationship between the optical disc 301 and the objective lens 306 on the left side, and the light of the far field pattern (far-field image) on the photodetector 309 on the right side. 3 shows an intensity distribution. FIG.
On the left side of (a), (b), and (c), the main light beam is indicated by a solid line, and the sub light beam is indicated by a broken line.

Recordable optical disk 301 such as a CD-R
In the figure, a pre-groove (groove) 600 used for detecting a tracking error is formed on a recording medium surface. The pre-groove 600 includes a convex land portion 601 and a concave groove portion 602. Information is recorded in the land 601
Done in The tracking error signal is transmitted to the land 601.
Represents the shift of the main light beam with respect to.

The far field pattern 700 of the main light beam among the return light beams has a bimodal intensity distribution due to the light diffraction effect at the edge of the land portion 601 or the groove portion 602.

As shown in FIG.
When the converging spot of the main light beam on 01 is located at the center of the land portion 601, the far field pattern 700 of the main light beam has a symmetric bimodal intensity distribution. in this case,
The light intensity at the two light detection units A and D of the four-split light detection unit 160 is equal to the light intensity at the other two light detection units B and C.

[0022] As shown in FIG.
When the converging spot of the main beam on 01 is shifted to the right relative to the land portion 601, the far field pattern 700 of the main beam has an asymmetric bimodal intensity distribution. In this case, the light intensity at the two light detection units A and D of the four-split light detection unit 160 is higher than the light intensity at the other two light detection units B and C.

As shown in FIG. 22C, the optical disk 3
When the converging spot of the main light beam on 01 is shifted to the left relative to the land portion 601, the far field pattern 700 of the main light beam has an asymmetric bimodal intensity distribution. In this case, the light intensity at the two light detection units B and C of the four-division light detection unit 160 is higher than the light intensity at the other two light detection units A and D.

Accordingly, the main light flux of the return light is detected.
The split light detection unit 160 is divided into light detection units A and D and light detection units B and C.
Assuming that the light detection unit is divided into two, the tracking error signal TES by the push-pull method using the output signals PA, PB, PC, and PD of the light detection units A, B, C, and D
Can be obtained as follows.

TES = (PA + PD) − (PB + PC) (2) The tracking error signal TES in the above equation is obtained by
It becomes 0 when the focused spot of the main light beam on 1 is located at the center of the land portion 601, and becomes positive when the focused spot of the main light beam on the optical disc 301 is shifted to the right from the center of the land portion 601. When the focus spot of the main light beam on the optical disc 301 is shifted to the left from the center of the land portion 601, the value becomes negative.

However, when the optical disk 301 is tilted, the far field on the four-division light detecting unit 160 is not irrespective of the fact that the condensed spot of the main light beam on the optical disk 301 is located at the center of the land 601. The pattern 700 has an asymmetric bimodal intensity distribution.

In an optical pickup device that does not integrally drive the optical system including the objective lens 306, even when only the objective lens 306 is moved for tracking servo, the light is condensed by the main light beam on the optical disk 301. Although the spot is located at the center of the land 601, the far-field pattern 700 on the four-divided light detector 160 has an asymmetric bimodal intensity distribution.

In these cases, an apparent tracking error occurs. This apparent tracking error is called a tracking error offset.

In order to reduce the tracking error offset generated when the optical disk 301 is tilted or the objective lens 306 is moved, a differential push-pull method is used. In the tracking servo by the differential push-pull method, the two-divided light detectors 161 and 162 on both sides of the four-divided light detector 160 are used.

As shown in FIG. 22, condensed spots due to the sub-beams obtained by the three-division diffraction grating 303 of FIG. 20 are formed in the groove portions 602 on both sides of the land portion 601. Thereby, the far-field patterns 701 and 702 of the sub-beams of the return beam are bimodal on the two-divided photodetectors 161 and 162, respectively, due to the diffraction effect of the light at the edges of the land 601 or the groove 602. It becomes an intensity distribution.

As shown in FIG. 22A, the optical disk 3
When 01 is shifted to the left, the intensity at the light detection unit E2 of the two-segment detection unit 161 is higher than the light intensity at the light detection unit E1, and the intensity at the light detection unit F2 of the two-segment light detection unit 162 is increased. The light intensity becomes higher than the light intensity at the light detection unit F1.

As shown in FIG. 22C, the optical disk 3
When 01 is shifted to the right, the two-divided light detection unit 161
The light intensity at the light detection unit E1 is higher than the light intensity at the light detection unit E2, and the light intensity at the light detection unit F1 of the two-part light detection unit 162 is higher than the light intensity at the light detection unit F2. Become.

As described above, the asymmetry of the light intensity distribution of the far field patterns 701 and 702 due to the sub light beam is opposite to the asymmetry of the light intensity distribution of the far field pattern 700 due to the main light beam. Therefore, the light detection units A,
Output signals PA, PB, PC, PD of B, C, D and output signals PE1, PE of photodetectors E1, E2, F1, F2
2, a tracking error signal TES by the differential push-pull method using PF1 and PF2 can be obtained by the following equation.

TES = (PA + PD) − (PB + PC) −k {(PE1 + PF1) − (PE2 + PF2)} (3) where k is a coefficient, and is set so that the tracking error offset is initially set to 0. You. Thus, according to the differential push-pull method, the tracking error offset can be compensated.

In recent years, an attempt has been made to reduce the size of an optical pickup device for a recordable optical disk by using a hologram optical element as in the case of a conventional read-only optical pickup device.

FIG. 23 is a schematic view of an optical pickup device having a transmission type hologram optical element disclosed in Japanese Patent Application Laid-Open No. 3-76035.

In FIG. 23, the radial direction (radial direction) of the optical disk 501 is defined as the X direction,
Is defined as a Y direction, and a direction perpendicular to the disk surface of the optical disk 501 is defined as a Z direction.

The optical pickup device shown in FIG. 23 includes a hologram unit 520 and a condenser lens 511.

A heat radiating block 504 is arranged on the stem 502, and a submount 50 is mounted on a side surface of the heat radiating block 504.
5 is mounted, and a semiconductor laser element 506 is mounted on the submount 505. Heat radiation block 50
The photodetector 507 is arranged on the upper surface of the fourth light source 4. A cap 503 is provided so as to surround the heat dissipation block 504. A hologram optical element 508 is arranged in an opening on the upper surface of the cap 503. A hologram optical element 508 is provided with a three-division diffraction grating 509 on a lower surface thereof, and a hologram surface 510 is formed on an upper surface of the hologram optical element 508.

The semiconductor laser element 506 emits a laser beam (light beam) in the Z direction. The light beam emitted from the semiconductor laser element 506 is diffracted by the three-division diffraction grating 509 in a plane including substantially the Y direction and the Z direction, the 0th-order diffracted light beam (main beam), the + 1st-order diffracted light beam (sub beam), and the −1st-order light beam. The light beam is split into three light beams (light beams) and transmitted through the hologram surface 510.

The three light beams transmitted through the hologram surface 510 are condensed by the condenser lens 511 on the optical disk 501 as a main spot and sub spots located on both sides thereof. This condenser lens 511 is
Reference numeral 2 denotes a support which is movable in the X direction for the tracking operation and movable in the Z direction for the focusing operation.

The three return light beams (reflected light beams) from the optical disk 501 are diffracted by the hologram surface 510 in a plane substantially including the X and Z directions, and detected by the photodetector 507. The hologram surface 510 has an asymmetric pattern, as shown in FIG. 23, and gives astigmatism to each of the three return light beams from the optical disk 501.

[0043]

SUMMARY OF THE INVENTION Hologram optical element 5
Also, in the optical pickup device of FIG.
The operations described with reference to FIGS. 21 and 22 can be similarly realized. In this case, the photodetector 507 is configured as shown in FIG.
Like the first photodetector 309, the photodetector 309 includes a four-split photodetector 160 and two two-split photodetectors 161 and 162.

As described above, when the hologram optical element 508 is used, the semiconductor laser element 506 and the photodetector 50 are used.
The optical system can be unitized by using 7 in the state of a chip. This makes it possible to reduce the size of the optical pickup device.

However, in the semiconductor laser device 506, the oscillation wavelength varies depending on the ambient temperature. Due to the fluctuation of the oscillation wavelength, the diffraction angle of the return light beam on the hologram surface 510 changes.

FIG. 25 is a schematic plan view showing the movement of the condensed spot on the photodetector 507 due to the fluctuation of the oscillation wavelength of the semiconductor laser element 506 in the optical pickup device of FIG.

At the time of adjustment, as shown in FIG.
The condensing spot S of the main light beam is located at the center of the four-division light detection unit 160. When the ambient temperature decreases and the oscillation wavelength of the semiconductor laser element 506 decreases, as shown in FIG. 25A, the condensed spot S on the four-division light detection unit 160 moves in the direction opposite to the diffraction direction (−X direction). Go to). Conversely, when the ambient temperature increases and the oscillation wavelength of the semiconductor laser element 506 becomes longer, as shown in FIG. 25C, the condensed spot S on the four-division light detector 160 is in the same direction as the diffraction direction (+ X
Direction). As a result, the level of the focus error signal FES decreases, and the detection accuracy of the focus state decreases.

An object of the present invention is to provide an optical pickup device capable of accurately detecting a focus state on an optical recording medium even when the diffraction angle of a return light beam changes due to a wavelength variation of a light source, and an optical recording medium using the same. It is to provide a driving device.

[0049]

According to a first aspect of the present invention, there is provided an optical pickup device comprising: a light source for emitting a light beam; and a first diffraction element for diffracting a return light beam based on the light beam emitted from the light source. And a first photodetector for detecting a return light beam diffracted by the first diffraction element, wherein the first diffraction element has four regions divided by first and second division lines intersecting each other. Has two regions at one diagonal position as first and second regions, and is obtained by further equally dividing the two regions at the other diagonal position by a third division line. , Fourth, fifth and sixth regions, wherein the first photodetector is substantially parallel to the direction in which the converging spot of the return light beam diffracted by the first diffraction element moves due to wavelength fluctuation of the light source. First partition line and second partition line orthogonal to the first partition line , And the condensed spots of the return light flux diffracted by the first and second regions of the first diffraction element are formed by the first and second light detectors of the first photodetector. Of the first diffraction element, diffracted by the third, fourth, fifth, and sixth regions of the first diffraction element. A condensed spot formed by a return light beam diffracted in the first and second regions is formed on each of the four photodetectors of the first photodetector or on the first division line. Things.

Here, "each of the four light detection units or on the first division line" means substantially at the center of the four light detection units, near the first division line in the four light detection units, and in the first division. Including on the line.

When the diffraction angle of the return light beam changes due to the wavelength fluctuation of the light source, the condensed spot on the first photodetector changes to the first position.
However, the converging spots due to the return light fluxes from the first and second regions of the first diffraction element are separated from the intersection of the first and second division lines by the first diffraction element. Are formed on the first dividing line, so that even if they move along the first dividing line, they do not exceed the second dividing line.

Therefore, a change in the output signal of each photodetector due to the movement of the converging spot is prevented. Therefore, even when the wavelength of the light source changes, the focus state on the optical recording medium can be accurately detected. In addition, since the outputs of the four photodetectors at the time of focusing are equalized, adjustment is easy.

The first, second, third, fourth, fifth and sixth regions of the first diffraction element are provided on the optical recording medium by calculating the outputs of the four photodetectors of the first photodetector. A spatial variation corresponding to the focus state may be given to each light beam so that the above focus state can be detected.

In this case, a spatial variation corresponding to the focus state is given to the return light beam diffracted in the first and second regions of the first diffraction element, so that the first light detector has a first division line. The light is received by the photodetectors on both sides, and the third, fourth, fifth
And the spatial variation corresponding to the focus state is given to the return light beam diffracted in the sixth region, and
The light is received by each of the two photodetectors.

Thus, the output signals of the two photodetectors at one diagonal position of the first photodetector and the two output signals at the other diagonal position are obtained.
The focus state on the optical recording medium can be detected by comparing the output signals of the two light detection units.

The return light flux diffracted in the third, fourth, fifth and sixth regions of the first diffraction element is reflected by the first photodetector.
A condensing spot may be formed substantially at the center of each of the photodetectors.

When the diffraction angle of the return light beam changes due to the wavelength fluctuation of the light source, the condensed spot on the first photodetector changes to the first light detector.
Of the first diffractive element, the converged spot due to the return light flux from the third, fourth, fifth and sixth regions of the first diffraction element is moved by the first photodetector before the movement. Since it is formed substantially at the center of each of the four photodetectors, even if it moves substantially parallel to the first division line, it does not exceed the second division line.

Therefore, a change in the output signal of each photodetector due to the movement of the converging spot is further prevented. Therefore, even when the wavelength of the light source changes, the focus state on the optical recording medium can be detected more accurately. In addition, since the outputs of the four photodetectors at the time of focusing are equalized, adjustment is easy.

The spatial variation corresponding to the focus state may be astigmatism. In this case, when the focus state on the optical recording medium deviates from the in-focus state, the shape of the condensed spot on the first photodetector changes flat, and each photodetector of the first photodetector changes. Output signal changes. Therefore, by comparing the sum of the output signals of the two photodetectors at one diagonal position of the first photodetector with the sum of the output signals of the two photodetectors at the other diagonal position, The focus state on the recording medium can be detected.

The first, second, third, fourth, fifth and sixth regions of the first diffraction element correspond to the intersections of the first, second and third division lines of the first diffraction element. Formed as a common origin, the first and second regions of the first diffractive element are:
The first photodetector has a grating pattern set on the basis of two points on the first division line that are separated from the intersection of the first and second division lines, respectively, and the third diffraction element of the first diffraction element , The fourth, fifth, and sixth regions are arranged such that the converging spot formed by the return light beam diffracted by the first and second regions is substantially at the center of each of the four photodetectors of the first photodetector. May be set as a reference.

In particular, the first and second regions of the first diffraction element are arranged along a direction substantially perpendicular to the direction in which the condensed spot of the return light beam diffracted by the first diffraction element moves due to wavelength fluctuation of the light source. May be arranged.

A light beam emitted from the light source is provided in the optical path between the light source and the first diffractive element, and is divided into the main light beam and the first and second light beams.
A second diffractive element for splitting the second light beam into two sub-beams, and a second light detector having two light detecting sections divided into two by a line substantially parallel to the first line of the first light detector And a third photodetector having two photodetectors divided into two by a section line substantially parallel to the first section line of the first photodetector, wherein the first diffraction element comprises: The first return light beam from the optical recording medium based on the main light beam is diffracted and guided to the first photodetector, and the second and third return light beams from the optical recording medium based on the first and second auxiliary light beams are diffracted. Is diffracted to the second and third photodetectors, respectively, and the first return light flux diffracted at the first and second regions of the first diffraction element is converted to the first light beam of the first photodetector. Forming condensed spots at opposite positions on the first division line on the first division line about the intersection of the first and second division lines , The first return light flux diffracted by the third, fourth, fifth and sixth regions of the first diffraction element converges substantially at the center of each of the four photodetectors of the first photodetector. A second return light beam that forms a light spot and is diffracted by the first and second regions of the first diffraction element forms a converging spot on a section line of the second photodetector, Second diffracted light at the third, fourth, fifth and sixth regions of the diffractive element
Return light beams form condensed spots in the two photodetectors of the second photodetector, and the first and second diffraction elements of the first diffraction element.
The third return light beam diffracted in the region of No. 3 forms a condensed spot on the dividing line of the third photodetector, and the third return beam in the third, fourth, fifth and sixth regions of the first diffraction element. The diffracted third return light beam may form a condensed spot in the two photodetectors of the third photodetector.

In this case, the condensed spot by the first return light beam diffracted in the first and second regions of the first diffraction element is located on the first and second division lines of the first photodetector. The first, second, third, and fourth diffractive elements of the first diffractive element are formed at positions separated from each other on the first division line about the intersection.
Focused spots of the first return light beam diffracted in the fifth and sixth regions are formed substantially at the center of each of the four photodetectors of the first photodetector. Further, the second and third diffracted light at the first and second regions of the first diffractive element.
Are formed on the dividing lines of the second and third photodetectors, respectively, and are diffracted by the third, fourth, fifth, and sixth regions of the first diffraction element. 2
And a condensed spot by the third return light beam are formed in the two photodetectors of the second and third photodetectors, respectively.

When the diffraction angle of the first return light beam changes due to the fluctuation of the wavelength of the light source, the condensed spots of the first return light beam move on the first photodetector substantially in parallel with the first division line. However, the condensed spot by the first return light flux from the first and second regions of the first diffraction element is shifted by a first return distance from the intersection of the first and second parting lines before the movement.
Are formed on the first dividing line, so that even if they move along the first dividing line, they do not exceed the second dividing line. Before the movement, the condensed spot of the first diffraction beam from the third, fourth, fifth, and sixth regions of the first diffraction element has a condensed spot substantially at the center of each of the four photodetectors. Formed first
Does not exceed the second division line even if it moves substantially parallel to the second division line.

Further, the condensed spot by the second return light beam from the first and second regions of the first diffraction element is the second spot.
Move along the division line of the photodetector, and the condensed spot by the second return light flux from the third, fourth, fifth, and sixth regions of the first diffraction element is subjected to the second light detection. It moves substantially parallel to the parting line in the two photodetectors of the vessel.

Further, the first and second diffraction elements of the first diffraction element
The condensed spot by the third return light flux from the area of the first diffraction element moves along the dividing line of the third photodetector, and moves from the third, fourth, fifth, and sixth areas of the first diffraction element. The condensed spot by the third return light beam moves substantially parallel to the dividing line in the two photodetectors of the third photodetector.

Therefore, a change in the output signal of each photodetector due to the movement of the converging spot is prevented. Therefore, even when the wavelength of the light source fluctuates, the focus state and the tracking state on the optical recording medium can be accurately detected.

On the other hand, the third, fourth and fifth diffraction elements of the first diffraction element
And the return light beam diffracted in the sixth region is divided into four lights on or near the first division line, which are separated from each other on the second division line of the first photodetector and opposite to each other. A condensing spot may be formed on each of the detection units.

When the diffraction angle of the return light beam changes due to the wavelength fluctuation of the light source, the condensed spot on the first photodetector changes to the first position.
Of the first diffractive element, the condensed spots due to the returning luminous flux from the third, fourth, fifth and sixth regions of the first diffractive element are moved before the first and second sections. Since it is formed on or near the first division line apart from the intersection of the lines, it does not exceed the second division line even if it moves substantially parallel to the first division line.

Therefore, a change in the output signal of each photodetector due to the movement of the converging spot is further prevented. Therefore, even when the wavelength of the light source changes, the focus state on the optical recording medium can be detected more accurately. In addition, since the outputs of the four photodetectors at the time of focusing are equalized, adjustment is easy.

The spatial variation corresponding to the focus state is astigmatism in the first and second regions,
In the fourth, fifth, and sixth regions, changes in the condensed spots on the four photodetectors of the first photodetector based on the Foucault method may be used.

In this case, when the focus state of the optical recording medium deviates from the in-focus state, the light is condensed by the return light flux from the first and second regions of the first diffraction element on the first photodetector. The shape of the spot changes flat,
The output signal of each photodetector of the first photodetector changes. Also, the third of the first diffraction elements on the first photodetector,
The shape of the converging spot in the return light beam from the fourth, fifth and sixth regions changes based on the Foucault method,
The output signal of each photodetector of the photodetector changes. Therefore, by comparing the sum of the output signals of the two photodetectors at one diagonal position of the first photodetector with the sum of the output signals of the two photodetectors at the other diagonal position, The focus state on the recording medium can be detected.

The first, second, third, fourth, fifth, and sixth regions of the first diffraction element correspond to intersections of the first, second, and third division lines of the first diffraction element. Formed as a common origin, the first and second regions of the first diffractive element are:
The first photodetector has a grating pattern set on the basis of two points on the first division line that are separated from the intersection of the first and second division lines, respectively, and the third diffraction element of the first diffraction element , The fourth, fifth and sixth regions are such that the converged spots formed by the return light beams diffracted in the first and second regions are opposite to each other about the second division line of the first photodetector. A grid pattern may be set on each of the four photodetectors on or near the first division line separated to the side.

In particular, the first and second regions of the first diffraction element are arranged along a direction substantially perpendicular to the direction in which the condensing spot of the return light beam diffracted by the first diffraction element moves due to the wavelength fluctuation of the light source. May be arranged.

A light beam emitted from the light source is provided in the optical path between the light source and the first diffraction element, and is divided into the main light beam and the first and second light beams.
A second diffractive element for splitting the second light beam into two sub-beams, and a second light detector having two light detecting sections divided into two by a line substantially parallel to the first line of the first light detector And a third photodetector having two photodetectors divided into two by a section line substantially parallel to the first section line of the first photodetector, wherein the first diffraction element comprises: The first return light beam from the optical recording medium based on the main light beam is diffracted and guided to the first photodetector, and the second and third return light beams from the optical recording medium based on the first and second auxiliary light beams are diffracted. Is diffracted to the second and third photodetectors, respectively, and the first return light flux diffracted at the first and second regions of the first diffraction element is converted to the first light beam of the first photodetector. Forming condensed spots at opposite positions on the first division line on the first division line about the intersection of the first and second division lines The first return beam diffracted by the third, fourth, fifth, and sixth regions of the first diffraction element is separated from each other about a second section line of the first photodetector. A condensed spot is formed on each of the four photodetectors on the first division line or near the first division line, and the second return light flux diffracted by the first and second regions of the first diffraction element is , A condensed spot is formed on the division line of the second photodetector, and the second return light flux diffracted by the third, fourth, fifth, and sixth regions of the first diffraction element is the second return light flux. Photodetector 2
A condensed spot is formed in the two photodetectors, and the third return light beam diffracted by the first and second regions of the first diffraction element forms a condensed spot on a section line of the third photodetector. The third return light beam formed and diffracted in the third, fourth, fifth and sixth regions of the first diffraction element forms the second return light beam of the third photodetector.
A condensed spot may be formed in one photodetector.

In this case, the condensed spot by the first return light beam diffracted in the first and second regions of the first diffraction element is located on the first and second division lines of the first photodetector. The first, second, third, and fourth diffractive elements of the first diffractive element are formed at positions separated from each other on the first division line about the intersection.
Focused spots of the first return light beam diffracted in the fifth and sixth regions are respectively applied to the four photodetectors on or near the first division line of the first photodetector. It is formed. Convergent spots formed by the second and third return light beams diffracted by the first and second regions of the first diffraction element are formed on the division lines of the second and third photodetectors, respectively. The condensed spots of the second and third return light beams diffracted in the third, fourth, fifth and sixth regions of the first diffraction element are separated by two light beams of the second and third photodetectors, respectively. It is formed in the light detecting section.

When the diffraction angle of the first return light beam changes due to the wavelength fluctuation of the light source, the condensed spots of the first return light beam move on the first photodetector substantially in parallel with the first division line. . In this case, the condensed spot by the first return light flux from the first and second regions of the first diffraction element is moved to the first section separated from the intersection of the first and second section lines before moving. Since it is formed on a line, even if it moves along the first division line, it does not exceed the second division line. The first from the third, fourth, fifth and sixth regions of the first diffractive element
The focused spot formed by the return light beam diffracted in the first and second regions before moving is on the first section line of the first photodetector or the first section. Since it is formed in each of the four photodetectors near the line, it does not exceed the second division line even if it moves substantially parallel to the first division line.

The condensed spot by the second return light beam from the first and second regions of the first diffraction element is the second spot.
Move along the division line of the photodetector, and the condensed spot by the second return light flux from the third, fourth, fifth, and sixth regions of the first diffraction element is subjected to the second light detection. It moves substantially parallel to the parting line in the two photodetectors of the vessel.

Further, the first and second diffraction elements of the first diffraction element
The condensed spot by the third return light flux from the area of the first diffraction element moves along the dividing line of the third photodetector, and moves from the third, fourth, fifth, and sixth areas of the first diffraction element. The condensed spot by the third return light beam moves substantially parallel to the dividing line in the two photodetectors of the third photodetector.

Therefore, a change in the output signal of each photodetector due to the movement of the converging spot is prevented. Therefore, even when the wavelength of the light source fluctuates, the focus state and the tracking state on the optical recording medium can be accurately detected. In this case, the area of the return light beam incident on the first and second regions of the first diffraction element is reduced. The area is larger than the area of the return light beam incident on the third, fourth, fifth, and sixth regions. Thereby, the light intensity of the condensed spot formed on the first division line of the first photodetector is changed to the light intensity of the condensed spot formed on each of the four photodetectors of the first photodetector. Higher than.

Therefore, when the condensed spot on the first photodetector moves along the first division line due to the wavelength fluctuation of the light source, the output signal of each photodetector of the first photodetector is output. Change becomes small. As a result, the focus state on the optical recording medium can be detected more accurately even when the wavelength of the light source fluctuates.

[0082] The astigmatism may be provided in a direction approximately 45 degrees with respect to the first and second division lines of the first photodetector. In this case, when the focus state on the optical recording medium deviates from the focused state, the shape of the condensed spot on the first photodetector is approximately 45 degrees with respect to the first and second division lines.
It has an elliptical shape with a major axis at an angle of degrees.

The first and second dividing lines of the first diffraction element make an angle of approximately 45 degrees with the first and second dividing lines of the first photodetector, and The third parting line may be substantially parallel to the first parting line of the first photodetector.

The light source emits a light beam having an elliptical far-field image, the return light beam forms an elliptical light spot on the first diffraction element, and the short axis of the elliptical light spot is the first diffraction element. Extends substantially parallel to the third parting line and has a long axis
The positional relationship between the light source and the first diffraction element may be set so as to extend to the first and second regions of the diffraction element.

An optical recording medium driving device according to a second aspect of the present invention includes a rotation driving section for rotating the optical recording medium, an optical pickup device for irradiating the optical recording medium with a light beam, and an optical pickup device according to the first aspect. The optical disc drive includes a pickup driving unit that moves the optical recording medium in a radial direction, and a signal processing unit that processes an output signal from a photodetector of the optical pickup device.

In the optical recording medium driving device according to the present invention, since the optical pickup device according to the first invention is used, the focus state on the optical recording medium can be accurately detected even when the wavelength of the light source changes. it can.

The hologram optical element according to the third invention is
A diffractive surface for diffracting the incident light beam and forming a condensed spot of the diffracted light beam on a virtual surface, wherein the diffractive surface is one of four regions divided by first and second dividing lines intersecting each other; Third and fourth regions obtained by having two regions at one diagonal position as first and second regions and equally dividing the two regions at the other diagonal position by a third division line. ,
Fifth and sixth regions, wherein the first and second division lines are approximately 45 degrees with respect to the intersection line between the plane including the optical axis of the incident light beam and the optical axis of the diffracted light beam and the diffraction surface. The angle of
The third dividing line is substantially parallel to an intersection line between a plane including the optical axis of the incident light beam and the optical axis of the diffracted light beam and the diffraction surface.

When the hologram optical element according to the present invention is used as a diffractive element in an optical pickup device, it is possible to prevent the output signal of each light detecting section from changing due to the movement of the converging spot. Therefore, even when the wavelength of the light source changes, the focus state on the optical recording medium can be accurately detected.

[0089]

DESCRIPTION OF THE PREFERRED EMBODIMENTS (1) First Embodiment FIG. 1 is a schematic diagram of an optical pickup device according to a first embodiment of the present invention. Optical pickup device 10 of FIG.
0 performs focus servo by astigmatism method and tracking servo by differential push-pull method.

In FIG. 1, the radial direction (radial direction) of the reflective optical disk 1 such as a CD-R is defined as the X direction, the track direction of the optical disk 1 is defined as the Y direction, and the direction perpendicular to the disk surface of the optical disk 1 is defined as the Z direction. And

The optical pickup device 100 includes a light emitting / receiving unit 10 and a condenser lens 5. The light emitting and receiving unit 10 includes a semiconductor laser element 2, a transmission type three-division grating 3, a transmission type hologram optical element, and a photodetector 6.

A block 8 is provided on a base 7, and a heat sink 9 is attached to a side surface of the block 8. The semiconductor laser device 2 is attached to a surface end of the heat sink 9. The three-division diffraction grating 3 is made of optical glass, optical resin, or the like, and is disposed in a holder 71 with a spacer 72 interposed therebetween. Further, the transmission type hologram optical element 4
Are arranged in the opening on the upper surface of the holder 71.

The semiconductor laser device 2 emits a laser beam (light beam) in the Z direction. The three-division diffraction grating 3 converts a light beam emitted from the semiconductor laser element 2 into a 0th-order diffracted light (main light beam), a + 1st-order diffracted light beam (sub-beam), and a -1st-order diffracted light in a plane substantially including the Y direction and the Z direction. 3 consisting of luminous flux (secondary luminous flux)
The light beam is divided into book light beams and transmitted through the transmission type hologram optical element 4. In the drawing, the three light beams are represented as one light beam.

The condenser lens 5 is supported by the actuator 73 so as to be movable in the radial direction (X direction) of the optical disk 1 for tracking servo, and is movable in the vertical direction (Z direction) for focus servo. Supported. The condensing lens 5 converts the main light beam and the two sub light beams diffracted and transmitted through the transmission type hologram optical element 4 at the 0th order onto the optical disc 1 as a main spot M0 and sub spots S1 and S2 located on both sides thereof. Collect light.

The transmissive hologram optical element 4 has a six-divided hologram surface 40, divides three return light beams (reflected light beams) from the optical disk 1 into six, and in-plane substantially includes the X and Z directions. Is diffracted first order and is incident on the photodetector 6. At this time, the transmission type hologram optical element 4 gives astigmatism to the three return light beams from the optical disc 1 respectively.

In the present embodiment, the optical disk 1 corresponds to an optical recording medium, the semiconductor laser device 2 corresponds to a light source,
The transmission hologram optical element 4 corresponds to a first diffraction element, and the three-division diffraction grating 3 corresponds to a second diffraction element.
Further, the four-divided light detection unit 60 corresponds to a first light detector,
The two-segment light detector 61 corresponds to a second photodetector, and the two-segment light detector 62 corresponds to a third photodetector.

FIG. 2 is a schematic plan view of the transmission hologram optical element 4 and the photodetector 6 used in the first embodiment.

The six-divided hologram surface 40 of the transmission hologram optical element 4 is divided into six regions Ha, Hb, Hc, Hd, He, and Hf by virtual dividing lines 4L, 4M, and 4N. The dividing lines 4L and 4M are orthogonal to each other and make an angle of approximately 45 degrees with respect to the radial direction (X direction) of the optical disc 1. The dividing line 4N is parallel to the radial direction (X direction) of the optical disc 1. Thereby, the two opposing regions Ha and Hd have the same area. The four opposing regions Hb, Hc, He, Hf have the same area.

The photodetector 6 has a four-division light detection unit 60 provided at the center for performing focus servo using the astigmatism method, and a four-division light detection unit 60 for performing tracking servo by the differential push-pull method. It includes two-divided light detectors 61 and 62 provided on both sides of the light detector 60.

The quadrant light detecting section 60 is composed of four light detecting sections A, B, C,
D. The division line LX is arranged substantially parallel to the radial direction (X direction) of the optical disc 1, and the division line LY is arranged substantially parallel to the track direction (Y direction) of the optical disc 1.

The two-divided light detecting section 61 is divided into two equal-area light detecting sections E1 and E2 by a dividing line LE. The dividing line LE is arranged substantially parallel to the radial direction (X direction) of the optical disc 1.

The two-divided light detector 62 is divided into two equal-area light detectors F1 and F2 by a dividing line LF. The dividing line LF is arranged substantially parallel to the radial direction (X direction) of the optical disc 1.

FIGS. 3 and 4 show the six-division hologram surface 4 of the transmission hologram optical element 4 according to the first embodiment.
It is a schematic diagram which shows the design method of 0 hologram pattern. Here, a case where astigmatism in which a light beam incident on the transmission type hologram optical element 4 is inverted with respect to the division line 4L as a symmetric axis and forms a spot on the photodetector 6 will be described. Two areas Ha, of the transmission type hologram optical element 4
The hologram pattern of Hd is shown in FIGS.
As shown in (d), each is designed based on the points C1 and C4 on the dividing line LX of the four-division light detection unit 60. The points C1 and C4 are located at a predetermined distance from the center point C0.

As for the design of the region Ha, as shown in FIG.
This is performed by creating only the area Ha corresponding to the converging spot Sa on the four-divided light detection unit 60 in the hologram pattern HA forming the converging spot SA centered at 1. Regarding the design of the region Hd, as shown in FIG. 4D, the four-divided light of the hologram pattern HD that forms the condensed spot SD centered on the point C4 on the dividing line LX of the four-divided light detection unit 60 Focused spot S on detection unit 60
This is performed by creating only a portion corresponding to d.

The hologram patterns of the four regions Hb, Hc, He and Hf of the transmission type hologram optical element 4 are as shown in FIGS. 3 (b) and 3 (c) and FIGS. 4 (e) and 4 (f), respectively. In addition, the photodetector A of the quadrant photodetector 60,
It is designed based on the points C2, C3, C5, and C6 substantially at the centers of D, C, and B, respectively.

As for the design of the region Hb, as shown in FIG. 3B, of the hologram pattern HB that forms the converging spot SB centered on the point C2 on the light detecting portion A, This is performed by creating only a portion corresponding to the converging spot Sb.

Regarding the design of the region Hc, as shown in FIG. 3C, of the hologram pattern HC that forms the condensed spot SC centered on the point C3 on the photodetector D, This is performed by creating only a portion corresponding to the converging spot Sc.

As for the design of the region He, as shown in FIG. 4E, of the hologram pattern HE which forms the condensed spot SE centered on the point C5 on the light detecting section C, This is performed by creating only a portion corresponding to the converging spot Se.

As for the design of the region Hf, as shown in FIG. 4F, the hologram pattern HF that forms the condensed spot SF centered on the point C6 on the light detecting portion B has This is performed by creating only a portion corresponding to the converging spot Sf.

Six regions Ha, Hb, Hc, Hd, H
The origin of the creation of the hologram patterns e and Hf is the intersection (the center of the circle) of the dividing lines 4L, 4M and 4N in common.

[0111] As shown in FIG.
The main light beams diffracted in the zero areas Ha and Hd are condensed as condensed spots Sa and Sd at positions opposite to each other with respect to the points C1 and C4 on the dividing line LX of the four-division light detection unit 60, respectively. . On the other hand, the region H of the six-segment hologram surface 40
The main beams diffracted by b, Hc, He, and Hf are condensed as condensed spots Sb, Sc, Se, and Sf substantially at the centers of the photodetectors A, D, C, and B of the quadrant photodetector 60, respectively. Is done.

Areas Ha and Hd on Six-Segment Hologram Surface 40
One of the sub-beams diffracted by is collected as condensed spots Qa and Qd on the dividing line LE of the two-divided light detector 61, respectively. One of the sub-beams diffracted in the regions Hb and Hc of the six-divided hologram surface 40 is condensed on the photodetector E2 as condensed spots Qb and Qc, and one of the sub-beams diffracted in the regions He and Hf is , And are condensed as condensed spots Qe and Qf on the photodetector E1.

Areas Ha and Hd on Six-Partition Hologram Surface 40
The other sub-beams diffracted by are collected as condensed spots Ra and Rd on the dividing line LF of the two-divided light detection unit 62. One of the sub-beams diffracted in the regions Hb and Hc of the six-segment hologram surface 40 is condensed as condensed spots Rb and Rc on the photodetector F2, and one of the sub-beams diffracted in the regions He and Hf is The light is focused on the light detection unit F1 as light focusing spots Re and Rf.

As described above, the focused spot is divided into six parts,
Two converging spots Sa and S arranged along the X direction
d are arranged at positions shifted from each other in opposite directions. The points C1 and C4 are set at positions away from the center point C0 so that the converging spots Sa and Sd do not exceed the division line LY due to fluctuations in the oscillation wavelength of the semiconductor laser element 2.

FIG. 5 is a schematic plan view showing the focusing state of the main light beam and the sub light beam on the photodetector in the first embodiment.

When the optical disk 1 separates from the condenser lens 5 and enters a focus error state, as shown in FIG. 5A, the condensed spot Sa moves from the point C1 on the dividing line LX to the light detector B. And the converging spot Sd
Has a shape extending from the point C4 on the dividing line LX into the light detecting portion D, and the condensed spots Sb, Sc, Se, and Sf have a shape extending within the light detecting portions A, D, C, and B, respectively.

When the main light beam is focused on the optical disc 1 (at the time of focusing), as shown in FIG.
The condensed spot Sa becomes a quarter circle extending over the photodetectors A and B about the point C1 on the division line LX, and the condensed spot Sd is formed on the photodetectors C and C about the point C4 on the division line LX. 1/4 circle spanning D
b, Sc, Se, Sf are 1 in the photodetectors A, D, C, B
/ 8 yen.

Further, when the optical disk 1 approaches the condenser lens 5 and enters a focus error state, FIG.
As shown in (c), the condensed spot Sa has a shape extending from the point C1 on the division line LX into the light detection unit A, and the condensed spot Sd is from the point C2 on the division line LX to the inside of the light detection unit C. And the converging spots Sb, Sc, Se, S
f has a shape extending in the photodetectors A, D, C, and B.

As described above, the focused spots Sb, Sc, S
e and Sf represent the conventional hologram surface 510 shown in FIG.
Changes exactly in the case of using
Changes apparently so as to move between the light detecting units A and B, and the light spot Sd changes apparently so as to move between the light detecting units C and D.

Therefore, the output signals PA, PB, PC, PD of the respective photodetectors A, B, C, D of the quadrant photodetector 60
Can be used to obtain a focus error signal FES by the following equation.

FES = (PA + PC) − (PB + PD) (1) The focus error signal FES in the above equation becomes positive when the optical disc 1 is too close, becomes 0 when the optical disc 1 is in a good focus state, and the optical disc 1 is too far. If negative. As described above, the optical disc 1 is determined based on the sign of the focus error signal FES.
Can be determined from the in-focus position.

The focus error signal FES is supplied to the actuator 73.
Then, by moving the condenser lens 5 in a direction perpendicular to the optical disk 1, it is possible to correct the state of light collection on the optical disk 1.

In this case, the condensed spots Sa and Sd by the main beam from the areas Ha and Hd on the six-segment hologram surface 40
Greatly contributes to the focus error signal FES.

The output signals PA, PB, PC, PD of the photodetectors A, B, C, D and the photodetectors E1, E2, F
The tracking error signal TES by the differential push-pull method can be obtained by the following equation using the output signals PE1, PE2, PF1, and PF2 of F1, F2.

TES = (PA + PD) − (PB + PC) −k {(PE1 + PF1) − (PE2 + PF2)} (3) where k is a coefficient, and is set so that the tracking error offset is initially set to 0. You. Thus, according to the differential push-pull method, the tracking error offset can be compensated.

FIG. 6A shows a condensed light spot when the ambient temperature increases and the oscillation wavelength becomes longer, and FIG.
6 shows a converging spot at the time of adjustment, and FIG. 6C shows a converging spot when the ambient temperature becomes lower and the oscillation wavelength becomes shorter.

At the time of adjustment, as shown in FIG. 6B, the condensed spots Sa and Sd are located at the center between the photodetectors A and B and the center between the photodetectors C and D, respectively. The light spots Sb, Sc, Se, and Sf are light detection units A,
It is located at the center of D, C and B.

When the oscillation wavelength of the semiconductor laser element 2 changes depending on the ambient temperature, the diffraction angle of the feedback light in the transmission hologram optical element 4 changes. Thereby, the condensed spots Sa, Sb, Sc, Sd,
Se and Sf move in the X direction parallel to the dividing line LX.

When the ambient temperature rises, the semiconductor laser device 2
When the oscillation wavelength becomes longer, the condensed spots Sa, Sb, Sc, Sd, Se, and Sf move so as to approach the left side of the quadrant light detector 60 as shown in FIG.

When the ambient temperature decreases and the oscillation wavelength of the semiconductor laser device 2 decreases, the condensed spots Sa, Sb, Sc, Sd, Se, and Sf as shown in FIG.
Moves so as to approach the right side of the quadrant light detection unit 60.

At this time, the condensing spot Sa is separated from the dividing line LX.
Move within the range of the photodetectors A and B, and the condensed spot Sd moves within the range of the photodetectors C and D along the dividing line LX, so that the output signals PA, PB, PC, PD Does not affect Further, the converging spots Sb, Sc, Se, S
Since f moves in the photodetectors A, D, C, and B, it does not affect the output signals PA, PD, PC, and PB.

(2) Second Embodiment Next, an optical pickup device according to a second embodiment of the present invention will be described. The overall configuration of the optical pickup device according to the second embodiment is the same as that of FIG.

FIG. 7 is a plan view of the transmission hologram optical element 4 and the photodetector 6 used in the optical pickup device according to the second embodiment. The structure of the light detector 6 is the same as that of the light detector 6 of FIG.

The transmission type hologram optical element 4 shown in FIG.
The difference from the transmission type hologram optical element 4 is that a hologram pattern is created so that astigmatism occurs in the same direction only in the two areas Ha and Hd of the transmission type hologram optical element 4, and the remaining four areas Hb2, Hc2, H
For e2 and Hf2, a six-division hologram surface 41 in which a hologram pattern that focuses on the photodetector 6 without generating astigmatism is used.

FIGS. 8 and 9 are diagrams showing a method of designing the six-divided hologram surface 41 of the transmission hologram element 4 according to the second embodiment. Here, a case will be described in which the light beam incident on the transmission type hologram optical element 4 has astigmatism in which a spot is formed on the photodetector 6 in an inverted shape with the division line 4L as a symmetric axis. As shown in FIGS. 8A and 9D, the method of designing the hologram patterns of the two regions Ha and Hd of the transmission hologram optical element 4 is as follows.
This is the same as the design method of the two regions Ha and Hd in FIGS. 3A and 4D.

The hologram patterns of the four regions Hb2, Hc2, He2 and Hf2 of the transmission type hologram optical element 4 are shown in FIGS. 8 (b) and (c) and FIGS. 9 (e) and 9 (e).
As shown in FIG. 8F, in the photodetectors A, D, C, and B of the four-divided photodetector 60, the dividing line LX shown in FIG.
C2, C3, C5, C near the upper point C1 or C4
6 are respectively designed.

For the design of the region Hb2, see FIG.
As shown in (1), this is performed by creating only 1/8 of the hologram pattern HB2 that is focused on the point C2 on the light detection unit A.

The design of the region Hc2 is described with reference to FIG.
As shown in (1), this is performed by creating only 1/8 of the hologram pattern HC2 focused on the point C3 on the light detection unit D.

The design of the area He2 is described in FIG.
As shown in (2), this is performed by creating only 1/8 of the hologram pattern HE2 focused on the point C5 on the light detection unit C.

For the design of the region Hf2, see FIG.
As shown in (1), this is performed by creating only 1/8 of the hologram pattern HF2 focused on the point C6 on the light detection unit B.

The six areas Ha, Hb2, Hc2, Hd,
The origin of creation of the hologram pattern of He2, Hf2 is commonly the intersection of dividing lines 4L, 4M, 4N (center of circle)
It is.

As shown in FIG.
The main light beams diffracted in the first areas Ha and Hd are condensed as condensed spots Sa and Sd, respectively, at positions opposite to each other with respect to the points C1 and C4 on the dividing line LX of the four-division light detection unit 60. . On the other hand, the region H of the six-divided hologram surface 41
The main luminous flux diffracted by b2, Hc2, He2, and Hf2 is
The light is condensed as condensed spots Sb, Sc, Se, and Sf near the dividing line LX of the four-division light detection unit 60, respectively.

Areas Ha and Hd of Six-Partition Hologram Surface 41
One of the sub-beams diffracted by is collected as condensed spots Qa and Qd on the dividing line LE of the two-divided light detector 61, respectively. Further, the region Hb of the 6-divided hologram surface 41
2, one of the sub-beams diffracted by Hc2 is a photodetector E2.
The light is condensed on the top as condensed spots Qb and Qc, and
2, one of the sub-beams diffracted by Hf2 is a photodetector E1.
Light is condensed on the upper surface as light condensing spots Qe and Qf.

Areas Ha and Hd of Six-Segment Hologram Surface 41
The other sub-beams diffracted by are collected as condensed spots Ra and Rd on the dividing line LF of the two-divided light detection unit 62. Areas Hb2 and Hc of six-segment hologram surface 41
One of the sub-beams diffracted at 2 is condensed as condensed spots Rb and Rc on the light detection unit F2, and is condensed into the regions He2 and Hf
One of the sub-beams diffracted by 2 is condensed on the light detection unit F1 as converging spots Re and Rf.

As described above, the focused spot is divided into six parts,
Two converging spots Sa and S arranged along the X direction
d are arranged at positions shifted from each other in opposite directions. The points C1 and C4 are formed at positions away from the center point C0 so that the converging spots Sa and Sd do not exceed the division line LY due to fluctuations in the oscillation wavelength of the semiconductor laser element 2.

FIG. 10 is a schematic plan view showing the focusing state of the main light beam and the sub light beam on the photodetector in the second embodiment.

When the optical disk 1 approaches the condenser lens 5 and enters a focus error state, as shown in FIG. 10 (c), the condenser spot Sa moves to the point C1 on the dividing line LX.
From the light spot A to the light detecting portion A.
d has a shape extending from the point C4 on the dividing line LX into the light detecting portion C, and each of the condensed spots Sb, Sc, Se, and Sf is enlarged, and the spot shape is a six-divided hologram surface 41
Hb2, Hc2, He2, and Hf2.

When the main light beam is focused on the optical disc 1 (at the time of focusing), as shown in FIG. 10B, the condensed spot Sa is focused on the point C1 on the dividing line LX by the light detecting section. A 1/4 circle extends over A and B, and the converging spot Sd becomes a 1/4 circle extending over the photodetectors C and D around the point C4 on the dividing line LX, and the converging spots Sb, Sc, and Se. , Sf are focused as points in the photodetectors A, D, C, B.

Further, when the optical disc 1 separates from the condenser lens 5 and enters a focus error state, FIG.
As shown in (a), the condensed spot Sa has a shape extending from the point C1 on the division line LX into the light detection unit B, and the condensed spot Sd is from the point C4 on the division line LX to the inside of the light detection unit D. And the converging spots Sb, Sc, Se, S
f is enlarged, and the spot shape becomes similar to the shapes of the regions Hb2, Hc2, He2, and Hf2 of the six-divided hologram surface 41. Focused spots Sb, Sc, Se, S in this case
f are formed point-symmetrically with the converging spots Sb, Sc, Se, and Sf of FIG. 10C when the optical disk 1 approaches the converging lens 5 and enters a focus error state.

As described above, the focused spots Sb, Sc, S
e and Sf are deformed because they are based on the principle of the Foucault method.

In this embodiment, focus error detection is performed by the astigmatism method in the first embodiment and the Foucault method described below. FIG. 11 is a schematic diagram for explaining the principle of the Foucault method.

In FIG. 11A, a light beam 901 is converged by a lens 900 to form a focal point 902. here,
As shown in FIG. 11B, a shielding plate 903 is arranged in a half area in the light beam 901. In this case, half of the light beam 901 is shielded by the shielding plate 903. The fact that a part of the light beam is shielded by an object is called “kere”. Due to this “shaking”, only half of the light flux 901 is focused at 90 °.
Connect two.

At the focal point 902, a two-divided photodetector 905 is arranged. Here, as shown in FIG. 11D, the two-segment light detection is performed so that a condensed spot 920 is formed on the dividing line 911 between the two-segment light detectors 910A and 910B of the two-segment light detector 905. The position of the vessel 905 is adjusted.

When the two-divided photodetector 905 is located at the focal point 902, the condensed spot 910 has a small dot shape. The two-segment photodetector 905 has a lens 9
When the position is close to 00, as shown in FIG. 11E, a semicircular condensed spot 920b is formed on the light detection unit 910B of the two-segment photodetector 905.

When the two-segment photodetector 905 is located farther from the lens 900 than the focal point 902, FIG.
As shown in (c), a semicircular condensed spot 920a is formed on the light detection unit 910A of the two-segment photodetector 905.

As described above, the case where the two-segment photodetector 905 is located closer to the focal point 902 from the lens 900 and the case where the two-segment photodetector 905 is located farther from the lens 900 with respect to the focal point 902. In some cases, the condensed spots 920a and 920b formed on the photodetectors 910A and 910B of the two-divided photodetector 905 are point-symmetric. Therefore, the output signals fa, f of the photodetectors 910A, 910B
The focus error signal FES can be obtained by the following equation using b.

FES = fa−fb (4) Whether the two-split photodetector 905 is located closer to or farther from the lens than the focal point 902 is determined by the sign of the focus error signal FES. Can be.

The method of detecting the focus error based on the change of the converging spot due to the "beam" of the light beam is called the Foucault method or the knife edge method.

FIG. 12 is a view for explaining the principle in which the focal spot Sb is deformed according to the Foucault method in the present embodiment.

In the in-focus state shown in FIG. 12B, the light beam from the area Hb2 of the 6-split hologram surface 41 focuses on the point C2 on the 4-split light detection unit 60. Area Hb of 6-split hologram surface 41
Since the focal point of the light beam from No. 2 is behind the surface of the four-division light detection unit 60, the six-division hologram surface 4 as shown in FIG.
The converging spot Sb having a similar shape in the area Hb2 of FIG.
Are formed on the four-division light detection unit 60 with the vertex as the vertex.

When the optical disc 1 is farther from the focused state, the focal point of the light beam from the area Hb 2 of the six-divided hologram surface 41 is closer to the front than the four-divided light detector 60. At a position farther than the focal point, since the shape of the condensed spot is inverted with respect to the point C2, the condensed spot Sb having a similar shape in the area Hb2 of the six-divided hologram surface 41 is divided into four as shown in FIG. When the optical disc 1 is close to the point C2 on the light detection unit 60, the condensed spot Sb in FIG.
It is formed at a position that is point symmetric with respect to. Therefore, when the optical disk 1 is far, the level of the output signal PA of the light detection unit A in the four-division light detection unit 60 decreases, and the light detection unit B
Output signal PB rises. The same applies to the deformation of the converging spots Sc, Se and Sf.

In this embodiment, as in the first embodiment, the direction of deviation from the in-focus position of the optical disc 1 is determined based on the sign of the focus error signal FES according to the equation (1), and 1 can be corrected. In this case, the condensed spots Sa, S of the main beam from the areas Ha, Hd of the six-divided hologram surface 41
not only d but also the region Hb on the six-segment hologram surface 41
2, Hc2, He2, and the converging spots Sb, Sc, Se, and Sf of the main luminous flux from Hf2 also greatly contribute to the focus error signal FES.

As described above, when the focus is deviated, the light quantity of most of the condensed spots contributes to the focus error signal FES, so that a focus error with high sensitivity can be detected.

Also, in the present embodiment, as in the first embodiment, the tracking error offset is compensated for by the differential push-pull method based on the tracking error signal TES according to the equation (3). Can be.

Here, when the points C2, C3, C5, and C6 are set on the dividing line LX of the photodetector 6, the effect by the Foucault method becomes more remarkable, but the dead zone is on the dividing line LX, and the focusing is performed. There is a disadvantage that the amplitude of the reproduction signal HFS is reduced because the total light amount in the state is reduced. Therefore, the points C2 and C6 or the points C3 and C5 are set as close to the division line LX as possible.

FIG. 13 is a schematic plan view showing the movement of the condensed spot on the photodetector 6 due to the fluctuation of the oscillation wavelength of the semiconductor laser device 2. FIG. 13A shows a condensed spot when the ambient temperature increases and the oscillation wavelength increases.
FIG. 13B shows a converging spot at the time of adjustment.
(C) shows a condensed spot when the ambient temperature is lowered and the oscillation wavelength is shortened.

In this embodiment, as in the first embodiment, when the oscillation wavelength of the semiconductor laser device 2 fluctuates depending on the ambient temperature, the condensed spot Sa becomes the dividing line L
X moves within the range of the photodetectors A and B, and the condensed spot Sd moves along the division line LX within the range of the photodetectors C and D, so that the output signals PA, PB, PC, Does not affect PD. Further, the converging spots Sb, Sc, Se,
Since Sf moves in the photodetectors A, D, C, and B respectively, it does not affect the output signals PA, PD, PC, and PB.

(3) Third Embodiment The optical positional relationship between the far-field pattern (beam cross-sectional intensity distribution) spot of the laser beam emitted from the semiconductor laser device 2 of FIG. 1 and the six-segment hologram surface 40 or 41. Is set as follows, the accuracy of the focus error signal FES can be improved.

FIG. 14 shows the optical pickup device 100 of FIG.
3 is a top view of the semiconductor laser device 2 in FIG.

As shown in FIG. 14, the semiconductor laser device 2
Mainly includes a clad layer 21, an active layer 22, and a clad layer 23. Usually, the active layer 2 of the semiconductor laser device 2
The divergence angle of the laser light emitted from 2 in the vertical direction (direction perpendicular to the active layer 22) is larger than the divergence angle in the horizontal direction (direction parallel to the active layer 22). Therefore, the far-field image 20 of the laser beam has an elliptical shape whose major axis is perpendicular to the active layer 22.

Optical pickup device 100 of the present embodiment
, The active layer 22 of the semiconductor laser device 2 is attached to the side surface of the heat sink 9 so as to be perpendicular to the Y direction. Therefore, the far-field image 20 of the laser beam has an elliptical shape having a major axis parallel to the Y direction and a minor axis parallel to the X direction.

FIG. 15 shows a condensed spot on the optical disc 1,
FIG. 4 is a schematic plan view showing a relationship between a light spot on a six-division hologram surface 40 and a converged spot on a photodetector.

[0173] As shown in FIG.
Is formed with a pre-groove 600 including a land portion 601 and a groove portion 602. A main spot M0 is formed by a main beam on the land portion 601 of the optical disc 1, and sub-spots S1 and S2 are formed by sub-beams on groove portions 602 on both sides of the land portion 601.

As shown in FIG. 15B, the light spot SP of the return light beam formed on the six-divided hologram surface 40 is
It has an elliptical shape having a major axis extending to the regions Ha and Hd and a minor axis extending along the dividing line 4N. As a result, the amount of return light flux incident on the regions Ha and Hd is reduced to the regions Hb and Hd.
The light amount becomes larger than the amount of the return light beam incident on c, He, and Hf.

Therefore, as shown in FIG.
Focused spots Sa, formed on the four-divided light detection unit 60
The light intensity of Sd becomes larger than the light intensity of the converging spots Sb, Sc, Se, Sf. Thus, the focus error signal F
Since the light amounts of the condensed spots Sa and Sd that greatly contribute to the ES increase, a sufficient level of the focus error signal FES can be obtained.

When the main spot M0 is displaced from the center of the land 601 in the radial direction of the optical disc 1, the light spot SP on the six-division hologram surface 40 moves along the division line 4N. Thereby, the total light amount of the converging spots Sb and Sc on the four-divided light detecting unit 60 and the converging spot S
There is a difference between the total light quantity of e and Sf. Also, a difference occurs between the total light quantity of the converging spots Qb and Qc and the total light quantity of the converging spots Qe and Qf on the two-divided light detecting unit 61,
There is a difference between the total light quantity of the condensed spots Rb and Rc on the two-divided light detection unit 62 and the total light quantity of the condensed spots Re and Rf.

Therefore, the tracking error signal TES by the differential push-pull method can be obtained by the above equation (3).

In this case, the converged spots Sb, Sc, Se, Sf on the four-divided light detector 60 and the converged spots Qb, Qc, Qe, Qf on the two-divided light detector 61 and the two-divided light detector 62 The upper converging spots Rb, Rc, Re, Rf greatly contribute to the tracking error signal TES.

Six-division hologram surface 4 of the first embodiment
According to 0, the condensed spots Sb, Sc, Se, Sf contributing to the tracking error signal TES are detected by the photodetectors A, D,
It is formed at the center of C and B. In addition, the focusing spot Q
b and Qc are formed in the light detecting portion E2,
e, Qf are formed in the photodetector E1, and the converging spot R
b, Rc are formed in the light detecting portion F2,
e and Rf are formed in the photodetector F1. Therefore,
The tracking error signal TES becomes stable. as a result,
High-precision tracking servo becomes possible. Similar results can be obtained by using the six-segmented hologram surface 41 in the second embodiment.

FIG. 16 is a schematic diagram showing a first arrangement example of the hologram unit 10 in the optical pickup device according to the first or second embodiment. FIG. 17 is a schematic diagram showing a second arrangement example of the hologram unit 10 in the optical pickup device according to the first or second embodiment.

In the example of FIG. 16, the hologram unit 10
A laser beam is emitted perpendicularly to the optical disc 1 from the
The light is focused on the recording medium surface of the optical disk 1 by the focusing lens 5. In the example of FIG. 17, a laser beam is emitted from the hologram unit 10 in parallel with the optical disc 1, and the reflection mirror 7
The light is reflected perpendicularly to the optical disk 1 by the optical disk 5, and is collected on the recording medium surface of the optical disk 1 by the condenser lens 5. In the example of FIG. 17, the thickness of the optical pickup device can be reduced.

FIG. 18 is a block diagram showing a configuration of an optical recording medium driving device 200 using the optical pickup device 100 of the above embodiment. The optical recording medium drive 200 shown in FIG. 18 is an optical disk drive for reading information from the optical disk 1.

The optical recording medium driving device 200 includes an optical pickup device 100, a motor 11, a feed motor 12, a rotation control system 13, a signal processing system 14, and a pickup control system 1.
5, including a feed motor control system 16 and a drive controller 17.

The motor 11 rotates the optical disc 1 at a predetermined speed. The rotation control system 13 controls the rotation operation of the motor 11. The feed motor 12 moves the optical pickup device 100 in the radial direction of the optical disc 1. The feed motor control system 16 controls the operation of the feed motor 12.
The optical pickup device 100 irradiates the optical disc 1 with a laser beam and receives a return light beam from the optical disc 1. The pickup control system 15 controls the light emitting / receiving operation of the optical pickup device 100.

The signal processing system 14 includes the optical pickup device 1
00, an output signal from the photodetector 6 is calculated, a reproduction signal, a focus error signal, and a tracking error signal are calculated, the reproduction signal is supplied to the drive controller 17, and the focus error signal and the tracking error signal are output to the pickup control system 15.
Give to. The drive controller 17 controls the rotation control system 13, the signal processing system 14, the pickup control system 15 and the feed motor control system 16 according to a command given via the drive interface 18, and outputs a reproduction signal via the drive interface 18. I do.

In this embodiment, the motor 11 and the rotation control system 13 correspond to a rotation drive unit, the feed motor 12 and the feed motor control system 16 correspond to a pickup drive unit, and the signal processing system 14 functions as a signal processing unit. Equivalent to.

Since the optical pickup device 100 of the above embodiment is used in the optical recording medium driving device 200 of FIG. 18, an accurate focus error signal can be obtained even when the wavelength of the laser light changes. As a result, focus servo is performed with high accuracy, and a high-quality reproduced signal is obtained.

In the above embodiment, the transmission type hologram optical element 4 is used as the first diffraction element. However, a reflection type diffraction element such as a reflection type hologram optical element may be used as the first diffraction element. .

In the above embodiment, the transmission type three-division grating 3 is used as the second diffraction element.
The present invention can be similarly applied to an optical pickup device using a reflection type three-division grating as the second diffraction element.

Further, as shown in FIG. 17, an optical path can be refracted by interposing a reflecting member such as a mirror between the light source and the optical recording medium.

Further, an optical element in which the three-divided diffraction grating 3 and the transmission hologram optical element 4 are integrated may be used. Further, a method other than the differential push-pull method described above may be used as the tracking servo method. CD-RO
If used only for read-only optical disks such as M, 3
A beam method may be used. FIG. 19 is a schematic plan view of a photodetector when the three-beam method is used. As shown in FIG. 19, a photodetector 6 having photodetectors 63 and 64 is used. In this case, if the outputs of the photodetectors E and F are PE and PF, respectively, the tracking error signal TES
Is obtained as the following equation.

TES = PE-PF (5) It is also possible to adopt the DPD method (Differential Phase Detection method) using only the four-divided photodetector 60 at the center of the photodetector 6. In this case, the light detection units A,
If the outputs of B, C and D are PA, PB, PC and PD, the following equations are obtained as the reproduction signal HFS and the diagonal difference signal DDS, respectively.

HFS = PA + PB + PC + PD (6) DDS = (PA + PC) − (PB + PD) (7) Then, the diagonal difference signal DD based on the reproduction signal HFS
If the phase of S is detected, a tracking error signal TES can be obtained.

Although the aperture of the transmission type hologram optical element 4 is a circular aperture in the above embodiment, other apertures such as a square aperture may be used.

[Brief description of the drawings]

FIG. 1 is a schematic diagram of an optical pickup device according to a first or second embodiment of the present invention.

FIG. 2 is a schematic plan view of a transmission hologram optical element and a photodetector used in the first embodiment.

FIG. 3 is a schematic diagram showing a method of designing a hologram pattern on a six-division hologram surface according to the first embodiment.

FIG. 4 is a schematic diagram illustrating a method of designing a hologram pattern on a six-divided hologram surface according to the first embodiment.

FIG. 5 is a schematic plan view illustrating a light condensing state on a photodetector according to the first embodiment.

FIG. 6 is a schematic plan view showing movement of a condensed spot on a photodetector due to fluctuation of an oscillation wavelength of a semiconductor laser element.

FIG. 7 is a schematic plan view of a transmission hologram optical element and a photodetector used in a second embodiment.

FIG. 8 is a schematic diagram illustrating a method of designing a hologram pattern on a six-divided hologram surface according to the second embodiment.

FIG. 9 is a schematic diagram showing a method of designing a hologram pattern on a six-division hologram surface according to the second embodiment.

FIG. 10 is a schematic plan view showing a light condensing state on a photodetector according to a second embodiment.

FIG. 11 is a schematic diagram for explaining the principle of the Foucault method.

FIG. 12 is a diagram illustrating the principle that a condensed spot deforms according to the Foucault method in the second embodiment.

FIG. 13 is a schematic plan view showing the movement of a converging spot on a photodetector due to a change in oscillation wavelength of a semiconductor laser device.

FIG. 14 is a top view of a semiconductor laser device in the optical pickup device of FIG. 1;

FIG. 15 is a schematic plan view showing a relationship between a converged spot on an optical disc, a light spot on a six-division hologram surface, and a condensed spot on a photodetector.

FIG. 16 is a diagram showing a first arrangement example of a hologram unit in the optical pickup device of FIG. 1;

FIG. 17 is a diagram showing a second arrangement example of the hologram units in the optical pickup device of FIG. 1;

18 is a block diagram showing a configuration of an optical recording medium driving device using the optical pickup device of FIG.

FIG. 19 is a schematic plan view of a photodetector when a three-beam method is used.

FIG. 20 is a schematic view of a conventional optical pickup device for a recordable optical disk.

FIG. 21 is a schematic plan view showing a light condensing state on a photodetector in the optical pickup device of FIG.

FIG. 22 is a diagram for explaining tracking servo by a push-pull method and a differential push-pull method.

FIG. 23 is a schematic view of a conventional optical pickup device using a hologram optical element.

24 is a plan view of a hologram surface of a hologram optical element in the optical pickup device of FIG.

FIG. 25 is a schematic plan view showing movement of a condensed spot on a photodetector due to a change in oscillation wavelength of a semiconductor laser element in the optical pickup device of FIG.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Optical disk 2 Semiconductor laser element 3 Diffraction grating for 3 division 4 Transmission hologram optical element 4L, 4M, 4N Division line 5 Condensing lens 6 Photodetector 40, 416 Six division hologram surface 60 Four division light detection part 61, 62 2 Split light detectors Ha, Hb, Hc, Hd, He, Hf, Hb2, Hc
2, He2, Hf2 area LX, LY, LE, LF Separator line

Continued on the front page (51) Int.Cl. ⁷ Identification FI FI Theme Court II (Reference) G11B 7/135 G11B 7/135 A (72) Inventor Toyozo Nishida 2-5-5 Keihanhondori, Moriguchi-shi, Osaka Inside Sanyo Electric Co., Ltd. (72) Inventor Yasuaki Inoue 2-5-5 Keihanhondori, Moriguchi-shi, Osaka Prefecture Inside Sanyo Electric Co., Ltd. (72) Inventor Yasuhiro Ueda 2-5-2, Keihanhondori, Moriguchi-shi, Osaka No. 5 Inside Sanyo Electric Co., Ltd. (72) Masayuki Shono 2-5-5, Keihanhondori 2-chome, Moriguchi City, Osaka Prefecture Inside Sanyo Electric Co., Ltd. (72) Minoru Sawada 2-chome, Keihanhondori, Moriguchi City, Osaka Prefecture No. 5-5 in Sanyo Electric Co., Ltd.

Claims (15)

[Claims] 1. A light source for emitting a light beam, a first diffraction element for diffracting a return light beam based on the light beam emitted from the light source, and a first for detecting a return light beam diffracted by the first diffraction element. Wherein the first diffraction element comprises a first and a second crossing each other.
Of the four regions divided by the dividing line, the two regions at one diagonal position as the first and second regions, and the two regions at the other diagonal position are further divided by a third dividing line. Third, fourth, fifth and sixth obtained by equal division
Wherein the first photodetector has a first dividing line substantially parallel to a direction in which a condensed spot of a return light beam diffracted by the first diffraction element moves due to a wavelength variation of the light source. And the first
And four light detection sections divided by a second division line orthogonal to the division line. The return light flux diffracted by the first and second regions of the first diffraction element is Forming condensed spots at opposite positions on the first division line with respect to the intersection of the first and second division lines of the first photodetector; The return light beams diffracted in the third, fourth, fifth, and sixth regions form condensed spots on each of the four photodetectors of the first photodetector or on the first division line. An optical pickup device. 2. The first, second, and third diffraction elements of the first diffraction element.
The third, fourth, fifth and sixth areas are in focus states so that the focus state on the optical recording medium can be detected by calculating the outputs of the four light detectors of the first photodetector. 2. The optical pickup device according to claim 1, wherein a spatial variation corresponding to (c) is given to each light beam. 3. The third, fourth, and third diffraction elements of the first diffraction element.
The return light beam diffracted in the fifth and sixth regions forms a focused spot substantially at the center of each of the four photodetectors of the first photodetector. Optical pickup device. 4. The third, fourth, and fourth diffraction elements of the first diffraction element.
The return light beam diffracted in the fifth and sixth regions is on or near the first division line, which is separated from the second division line of the first photodetector on the opposite side with respect to the second division line. 3. The optical pickup device according to claim 2, wherein condensed spots are formed on each of the four photodetectors. 5. The optical pickup device according to claim 3, wherein the spatial variation corresponding to the focus state is astigmatism. 6. The spatial variation corresponding to the focus state is astigmatism in the first and second regions, and is based on the Foucault method in the third, fourth, fifth, and sixth regions. 5. The optical pickup device according to claim 4, wherein the change is a change in a condensed spot on the four light detection units of the first photodetector. 7. The apparatus according to claim 5, wherein the astigmatism is given in a direction substantially 45 degrees with respect to the first and second division lines of the first photodetector. Optical pickup device. 8. The first, second, and third diffraction elements of the first diffraction element.
The third, fourth, fifth and sixth regions are formed with the intersection of the first, second and third dividing lines of the first diffraction element as a common origin, and The first and second regions are grid patterns respectively set on the basis of two points on the first division line that are separated from the intersection of the first and second division lines of the first photodetector. And the third, fourth, fifth, and sixth regions of the first diffraction element are respectively set with reference to a substantially center of each of four light detection units of the first light detector. 8. A grid pattern as defined in claim 3, wherein
An optical pickup device according to any one of the above. 9. The first, second, and third diffraction elements of the first diffraction element.
The third, fourth, fifth and sixth regions are formed with the intersection of the first, second and third dividing lines of the first diffraction element as a common origin, and The first and second regions are grid patterns respectively set on the basis of two points on the first division line that are separated from the intersection of the first and second division lines of the first photodetector. Wherein the third, fourth, fifth and sixth regions of the first diffractive element are spaced away from each other about the second section line of the first photodetector 8. The optical pickup according to claim 4, wherein the optical pickup has a grating pattern set on each of the four photodetectors on or near the first division line. 9. apparatus. 10. A second diffraction element which is provided in an optical path between the light source and the first diffraction element and divides a light beam emitted from the light source into a main light beam and first and second sub light beams. A second photodetector having two photodetectors divided into two by a section line substantially parallel to the first section line of the first photodetector; and a second photodetector of the first photodetector. A third photodetector having two photodetectors divided into two by a section line substantially parallel to the first section line, wherein the first diffraction element is configured to perform the optical operation based on the main light beam. The first return beam from the recording medium is diffracted and guided to the first photodetector, and the second and third return beams from the optical recording medium based on the first and second sub-beams are diffracted. To the second and third photodetectors, respectively, and the first of the first diffraction elements Preliminary the diffracted by the second region the first feedback light beam, said about the intersection of the first of said first and second marking lines of the photodetector first
Converging spots are formed respectively at positions on opposite sides of each other on the dividing line, and the first feedback diffracted by the third, fourth, fifth and sixth regions of the first diffraction element The light beam forms a condensed spot substantially at the center of each of the four light detection units of the first photodetector, and the light beams diffracted by the first and second regions of the first diffraction element. The return light beam of No. 2 forms a condensed spot on the division line of the second photodetector, and is diffracted by the third, fourth, fifth and sixth regions of the first diffraction element. The second return light beam forms condensed spots in two light detecting portions of the second photodetector, and the third diffracted light is diffracted by the first and second regions of the first diffraction element. Return beam forms a condensed spot on the dividing line of the third photodetector, and the first diffraction element The third return light beam diffracted in the third, fourth, fifth, and sixth regions forms a converging spot in two photodetectors of the third photodetector. The optical pickup device according to any one of claims 3, 5, 7, and 8. 11. A second diffraction element which is provided in an optical path between the light source and the first diffraction element, and divides a light beam emitted from the light source into a main light beam and first and second sub light beams. A second photodetector having two photodetectors divided into two by a section line substantially parallel to the first section line of the first photodetector; and a second photodetector of the first photodetector. A third photodetector having two photodetectors divided into two by a section line substantially parallel to the first section line, wherein the first diffraction element is configured to perform the optical operation based on the main light beam. The first return beam from the recording medium is diffracted and guided to the first photodetector, and the second and third return beams from the optical recording medium based on the first and second sub-beams are diffracted. To the second and third photodetectors, respectively, and the first of the first diffraction elements Preliminary the diffracted by the second region the first feedback light beam, said about the intersection of the first of said first and second marking lines of the photodetector first
Converging spots are respectively formed at distant positions opposite to each other on the dividing line of the first diffraction element, and the first feedback diffracted by the third, fourth, fifth and sixth regions of the first diffraction element The light flux is condensed on each of the four photodetectors on the first division line or near the first division line, which are separated from each other on the first division line at the opposite sides of the second division line. Forming a spot, wherein the second return light beam diffracted by the first and second regions of the first diffraction element forms a converged spot on a section line of the second photodetector; The second return light flux diffracted in the third, fourth, fifth, and sixth regions of the first diffraction element is condensed spots in two photodetectors of the second photodetector. Forming the third diffracted light in the first and second regions of the first diffractive element. The return light beam forms a condensed spot on the dividing line of the third photodetector, and the third light beam diffracted by the third, fourth, fifth and sixth regions of the first diffraction element. The optical pickup device according to any one of claims 4, 6, 7, and 9, wherein the return light beam forms a converging spot in two light detection units of the third photodetector. 12. The first and second parting lines of the first diffractive element make an angle of approximately 45 degrees with the first and second parting lines of the first photodetector, The first
12. The optical pickup device according to claim 1, wherein the third division line of the diffraction element is substantially parallel to the first division line of the first photodetector. 13. The light source emits a light beam having an elliptical far-field pattern, the return light beam forms an elliptical light spot on the first diffraction element, and a minor axis of the elliptical light spot. Extend substantially parallel to the third dividing line of the first diffractive element and have a major axis extending to the first and second regions of the first diffractive element. The optical pickup device according to claim 1, wherein a positional relationship with the element is set. 14. A rotation drive unit for rotating an optical recording medium, the optical pickup device according to claim 1, which irradiates a light beam to the optical recording medium, and the optical pickup device according to claim 1, An optical recording medium driving device comprising: a pickup driving unit that moves in a radial direction of the optical pickup device; and a signal processing unit that processes an output signal from the photodetector of the optical pickup device. 15. A diffractive surface for diffracting an incident light beam and forming a condensed spot of the diffracted light beam on a virtual plane, wherein the diffractive surface is divided by first and second dividing lines intersecting each other. Two regions at one diagonal position out of the four regions as the first and second regions, and the two regions at the other diagonal position are equally divided by a third dividing line. And third, fourth, fifth, and sixth regions, wherein the first and second dividing lines include a surface including an optical axis of the incident light beam and an optical axis of the diffracted light beam, and the diffraction surface. Forming an angle of approximately 45 degrees with respect to the line of intersection with the plane, wherein the third dividing line is at the intersection of the plane containing the optical axis of the incident light beam and the optical axis of the diffracted light beam with the diffraction surface. A hologram optical element which is substantially parallel.