JP3518457B2 - Optical device - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical pickup used in a reading device for an optical information recording medium such as an optical disc, and more particularly to a DVD (Digital Versat).
The present invention relates to an optical device suitable for a compatible reproduction system of ile disc) and CD-R (Compact Disc-write once) and capable of being downsized, and an optical pickup using the same.

[0002]

2. Description of the Related Art In recent years, a higher density DV has been added to a CD, which is an optical disc system for consumer use which has been popularized in general.
The D system has been proposed, commercialized, and started to spread.
In the DVD player, which is the reproducing apparatus, compatible reproduction of the CD is indispensable in order to avoid duplication of the apparatus and complexity of use. Similarly, a compatible reproduction function is also required for a CD-R (Compact Disc-write once) that can be reproduced by a CD player. Therefore,
Techniques for reproducing discs of such various standards have been developed, and further, simplification of the configuration for realizing the technique and cost reduction have become problems.

Particularly, in the above-mentioned CD-R, since the reflectance of the recording medium has a large wavelength dependency, the DV
A laser light source of 780 nm band different from the 650 nm band for D is indispensable, and a pickup optical system incorporating this light source of two wavelengths is required.

For this reason, conventionally, two independent pickups are mechanically coupled, or a light emitting and receiving integrated element is attached independently for each wavelength, and they are combined on the same optical axis by a dichroic prism, and a part of an objective lens or the like is combined. Those that share an optical system are being developed. Further, it is proposed that two semiconductor laser chips having different wavelengths are mounted in the same package, and the other parts are independent but the optical axis is made common.

On the other hand, in response to demands for cost reduction and miniaturization, attempts have been made to integrate optical pickup optical systems. For example, a semiconductor laser (LD), a photo detector (PD), and a hologram element (HOE: Holo)
A device in which a graphic optical element) is integrated has been developed and is being applied to a DVD as well as a CD. Further, the academic societies have proposed a structure in which two wavelengths are further integrated (for example, ISOM'98 Technical Digest p.
p22-, Tu-D-01).

As in the document, in an integrated device in which a semiconductor laser and a photodetector can be arranged in the immediate vicinity, it is easy to arrange the light receiving portion of the diffracted light by the hologram element and the light emitting point of the semiconductor laser at a substantially conjugate position. Is possible. Therefore, a complementary (complementary) spot size method (“SSD method”: Spot Size Detection) that uses both ± 1st order diffracted light from the hologram element
Focus error detection can be realized by. This method
Compared with other practically used "knife edge method", 1
It has an advantage that it is not necessary to strictly adjust the position of the hologram element, and it is not necessary to discard one of the 2 ± 1st order diffracted lights and the efficiency is high.

FIG. 13 shows the spot size method ("SS
FIG. 5 is an explanatory diagram illustrating focus error detection by “D method”: Spot Size Detection (Japanese Patent Laid-Open No. 5-10141).
7). More specifically, FIG. 13A is a schematic side view of the device for performing the focus error detection, and FIG.
FIG. 3 is a schematic plan view of a photodiode or the like for detecting diffracted light in the device.

As shown in FIG. 13A, in this focus error detecting device, the reflected light reflected by the optical disk 357 is separated into a pair of conjugate lights b1, b1 'by the hologram element 355 through the objective lens 356. To be done. Here, the hologram element 355 is configured such that the conjugate light b1 is focused above the light receiving element substrate 350 and the conjugate light b1 ′ is focused below the substrate 350.

Then, as shown in FIG. 13B, each of the conjugate lights b1 and b1 'is received by the photo-detecting diodes 352 and 353 provided on the light-receiving element substrate 350. The photodetection diodes 352 and 353 are connected to the conjugate light b1.
And regions 352a, 352b, 352c and 3 in the X direction orthogonal to the Y direction in which b1 'and b1' are separated, respectively.
It is divided into three parts 53a, 353b, 353c.

With this structure, the focus error signal FE of the laser beam for the optical disk 357 is obtained.
Represents the outputs of the light receiving areas 352a, 352b, 352c as w1, w2, w3, respectively, and
The outputs of 353b and 353c are respectively w4, w5 and w6.
Then, FE = (w1 + w3 + w5)-(w2 + w4 + w6) (1)

That is, when the laser light emitted from the laser light source 351 and raised by the raising mirror 354 enters the optical disc 357 through the objective lens 356, the laser light is focused on the disc 357. If so, the size of the spot S1 on the photodetection diode 352 and the size of the spot S2 on the photodetection diode 353 are the same, and the focus error signal F of the formula (1) is calculated.
E becomes zero. On the other hand, when the focus of the laser light on the optical disk 357 is deviated, the spot S1 on the detection diode 352 and the detection diode 35 are detected.
The sizes of the spots S2 on 3 are different, and the focus error signal FE of the formula (1) has a positive or negative value different from zero. Therefore, the polarity of the focus error signal FE is inverted before and after focusing. Therefore, the laser beam can be focused on the optical disc 357 by detecting the focus error signal FE.

[0012]

By the way, if the focus error detection by the spot size method and the two-wavelength optical system are made compatible, the wavelength dependence of the diffraction angle by the hologram element becomes a problem.

That is, in the diffraction grating, the characteristics such as the diffraction angle are determined by the mathematical relationship between the periodic structure and the wavelength of light, and therefore the diffraction angle greatly changes for different wavelengths. More specifically, in the “spot size method”, which is a focus error detection method suitable for an integrated device using the hologram element, a photodetector that detects hologram element diffracted light in the immediate vicinity of the conjugate point of the semiconductor laser emission point is used. It is essential to arrange the light receiving surface. However, when light beams of different wavelengths are made incident on the same hologram element, the optimum photodetector light receiving surface position greatly changes due to the above-mentioned characteristic change. Therefore, it is difficult to integrate the semiconductor laser and the photodetector on the same photodetector substrate. Further, it is difficult to derive a compatible solution for aberration correction and the like for optimizing the lens action of the hologram element.

For example, the two-wavelength integrated device (IS
OM'98 Technical Digest pp22-, Tu-D-01)
In the above, only one of the ± first-order diffracted lights is used for each wavelength, and the above-mentioned complementary structure has not been realized.

Therefore, it is an object of the present invention to provide an optical device which realizes complementary focus error detection for the two wavelengths in the optical system using the two wavelengths as described above.

[0016]

An optical device of the present invention for achieving the above object is an optical device for reading information from an information recording medium and an optical device for reading information from an information recording medium, and has a first wavelength. A first light source for outputting a light of a second wavelength, a second light source for outputting a light of a second wavelength, the first,
A hologram element having a first diffraction area and a second diffraction area for diffracting light of a second wavelength; a light receiving element substrate provided with a first light receiving element and a second light receiving element for receiving diffracted light from the hologram element; The first diffraction region and the second diffraction region.
The diffractive region has a grating array in which the grating axis directions are parallel to each other and the grating pitches are different from each other, and the light emitting points of the first and second light sources are separated from each other by a predetermined distance in a direction orthogonal to the grating axis. The first diffraction region and the second diffraction region are spaced apart from each other.
The grating pitch of the diffractive region is determined by the incident position of the diffracted light of the first wavelength on the light-receiving element substrate surface by the first diffractive region or the second diffractive region and the 0th-order transmitted light of the first wavelength. The distance (L11; L12) from the axis is defined as the first distance, and the incident position of the diffracted light of the second wavelength on the light receiving element substrate surface by the same diffraction region and the 0th-order transmitted light of the second wavelength The second distance (L21; L22) from the fixed optical axis
The distance between the first distance and the second distance (| L
11-L21 |; | L12-22 |) is substantially equal to the interval between the light emitting points of the first and second light sources, and the diffracted light of the first or second wavelength is diffracted by the first diffraction region. wherein the incident position of the light receiving device substrate surface, the distance between the incident position of the by the second diffraction area, to the light receiving device substrate surface of the diffracted light of the same wavelength (| L11-L12 |; | L21-22
|) Is set to be substantially equal to the distance between the light emitting points, and thus the first wavelength and the second wavelength due to the first diffraction region
The diffracted light of the wavelength converges to substantially the same first position on the light receiving element substrate, and the diffracted light of the first wavelength and the second wavelength by the second diffraction region are substantially the same on the light receiving element substrate. so as to converge to a second position, the first, the respective to the second position the first, characterized in that the second light-receiving elements are arranged.

Here, "approximately equal (same)" means "5.
It means "equal (same) with an error of about 0 μm or less".

The optical device of the present invention is also an optical device for reading information from an information recording medium, the first light source outputting light of a first wavelength, the second light source outputting light of a second wavelength, and A hologram element having a first diffraction area and a second diffraction area for diffracting light of the first and second wavelengths, and a light receiving element provided with a first light receiving element and a second light receiving element for receiving the diffracted light from the hologram element. A substrate; and the first
The diffractive area and the second diffractive area have the same grating pitch, and the grating axis directions are different from each other by a predetermined angle within 30 °, and the light emitting points of the first and second light sources are the grating points. The first diffraction region and the second diffraction region are separated from each other by a predetermined distance in a direction substantially orthogonal to the axial direction.
The diffraction area grating pitch is an optical axis determined by the incident position of the diffracted light of the first wavelength on the light receiving element substrate surface by the first diffractive area or the second diffractive area and the 0th-order transmitted light of the first wavelength. Between the incident position of the diffracted light of the second wavelength on the light receiving element substrate surface by the same diffraction region and the optical axis determined by the 0th-order transmitted light of the second wavelength. Is defined as a second distance, the difference between the first distance and the second distance is set to be substantially equal to the distance between the light emitting points of the first and second light sources. The direction of the second diffractive area depends on the diffracted light of the first and second wavelengths diffracted by the first diffractive area and converges to substantially the same first position on the light receiving element substrate. , The diffracted light of the first wavelength and the second wavelength is separated from the light emitting point on the light receiving element substrate. The first and second light receiving elements are arranged at the first and second positions, respectively, so that they converge to substantially the same second position which is apart from the first position by a predetermined distance in a direction orthogonal to the direction. It is characterized by

Here, "substantially" means "with an error of 50 μm or less". For example, "substantially equal" or "converging to substantially the same first position" and "converging to substantially the same second position" are "equal with an error of 50 μm or less" or "5.
Converge to the same first position with an error of 0 μm or less ”,“ 50 μm
It means "convergence to the same second position with the following error".

In the above, it is desirable to obtain the focus error signal based on the signals from the first light receiving element and the second light receiving element.

[0021]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. In each figure, the same or similar elements are indicated by the same or similar numbers.

FIG. 1 is a perspective view of the first embodiment of the optical device of the present invention, and FIG. 2 is an explanatory view showing the light traces of diffracted light in the first embodiment.

The first embodiment of this optical device is an optical device 23 for reading information from the information recording medium 21,
A first light source 25 that outputs light of a first wavelength, a second light source 27 that outputs light of a second wavelength, and a first diffraction region 29 and a second diffraction region that diffract the light of the first and second wavelengths. A hologram element 33 having 31 and a light receiving element substrate 39 provided with a first light receiving element 35 and a second light receiving element 37 for receiving diffracted light from the hologram element 33 are provided, and the first diffraction area 29 and the first diffraction area 29 are provided. The two-diffraction region 31 has a lattice arrangement in which the lattice axis directions are parallel to each other and the grating pitches are different from each other, and the emission points of the first and second light sources 25 and 27 are Y parallel to the lattice axis direction. In the X-axis direction orthogonal to the axial direction, they are separated from each other by a predetermined distance d, and the grating pitch of the first diffraction region 29 and the second diffraction region 31 is equal to the first pitch.
Between the incident position of the diffracted light of the first wavelength on the surface of the light receiving element substrate 39 by the diffractive region 29 (or the second diffractive region 31) and the optical axis A1 determined by the 0th-order transmitted light of the first wavelength. The distance L11 (L12) is the first distance, and the optical axis A2 is determined by the incident position of the diffracted light of the second wavelength on the surface of the light receiving element substrate 39 by the same diffraction region and the 0th-order transmitted light of the second wavelength. When a distance L21 (L22) between the first distance and the second distance is defined as a second distance | L11-L21
| (| L12-L22 |) is substantially equal to the distance d between the light emitting points of the first and second light sources, and the diffracted light of the first (or second) wavelength by the first diffraction region 29. The incident position on the surface of the light receiving element substrate 39 of the second diffraction region 3
1, the distance | L11-L12 | (| L21- between the incident position of the diffracted light of the same wavelength on the surface of the light receiving element substrate 39
L22 |) is set to be substantially equal to the distance d between the light emitting points, and thus the first diffraction region 29
The diffracted lights of the wavelengths and the second wavelengths converge to substantially the same first position on the light receiving element substrate 39, and the diffracted lights of the first and second wavelengths by the second diffraction region 31 are the light receiving elements. It is characterized in that it converges to substantially the same second position on the substrate 39, and the first and second light receiving elements 35 and 37 are arranged at the first and second positions, respectively.

More specifically, as shown in FIGS. 1 and 2,
The optical device 23 of the first embodiment is a DVD or C
A first light source 25 for outputting light of a first wavelength λ1 and a second light source 27 for outputting light of a second wavelength λ2 are used for an optical pickup that reads information from an information recording medium 21 such as D. , Is provided. Here, the first wavelength λ1 is, for example, 650 nm for DVD, and the second wavelength λ2 is
Is, for example, 780 nm for CD.

The first light source 25 and the second light source 27 are separated from each other by a predetermined distance d in the direction (X-axis direction) orthogonal to the lattice axis direction (Y-axis direction) of the hologram element described later. In FIG. 2, conjugate points C1 and C2 of the light emitting points of the light sources 25 and 27 are shown. This conjugate point C
Reference numerals 1 and C2 represent image positions of the light emitting points of the first and second light sources 25 and 27 by the reflection mirror 41 shown in FIG.

The optical device 23 further comprises a hologram element 33 having a first diffraction area 29 and a second diffraction area 31 for diffracting the light of the first and second wavelengths reflected by the information recording medium 21.

As shown in FIG. 3, the hologram element 3
The first diffraction region 29 and the second diffraction region 31 of No. 3 are obtained by dividing a circular region on the substrate (not shown) of the hologram element 33 by a straight line a extending in the X-axis direction and a straight line b extending in the Y-axis direction. In this case, they are formed at a pair of diagonally existing positions and at another pair of diagonally existing positions, respectively. The grating pitch Λ1 of the first diffraction area 29 is set to be larger than the grating pitch Λ2 of the second diffraction area 31. Therefore, when light of one wavelength is incident, the first
The diffraction angle of the diffracted light by the diffraction area 29 is determined by the second diffraction area 3
It becomes smaller than the diffraction angle of the diffracted light (of the same order) by 1.

Referring again to FIG. 2, optical axes A1 and A2 determined by the 0th-order transmitted light of the first and second wavelengths λ1 and λ2.
Passes through the conjugate points C1 and C2, and the X and Y coordinates thereof represent the X and Y coordinates of the conjugate points C1 and C2.

By the way, when the distance d between the light emitting points of the first light source 25 and the second light source 27 is given,
The grating pitch Λ1, of the diffraction area 29 and the second diffraction area 31
Λ2 is determined so as to satisfy the following two conditions.

1. + 1st order diffracted light r of the first wavelength λ1 by the first diffraction region 29 (or the second diffraction region 31)
The distance L11 (L12) between the incident position P1 (P2) of 11 (r12) on the surface of the light receiving element substrate 39 and the optical axis A1 determined by the 0th-order transmitted light of the first wavelength λ1 is defined as the first distance. , The second wavelength λ2 by the same diffraction region 29 (31)
The distance L21 (L22) between the incident position P1 (P2) of the diffracted light r21 (r22) on the surface of the light receiving element substrate 39 and the optical axis A2 determined by the 0th-order transmitted light of the second wavelength λ2 is represented by When the distance is two, the difference between the first distance and the second distance |
L11-L21 | (| L12-L22 |) is substantially equal to the distance d between the light emitting points of the first and second light sources.

2. Diffracted light r11 of the first wavelength λ1 (or the second wavelength λ2) by the first diffraction region 29.
Incident position P1 of (r21) on the surface of the light receiving element substrate 39
And an interval | L11-L12 | (| L21-L2 between the incident position P2 of the diffracted light r12 (r22) of the same wavelength λ1 (λ2) on the light receiving element substrate surface by the second diffraction region 31.
2│) becomes almost equal to the interval of the light emitting points d.

Here, "substantially equal (same)" means "5.
It is desirable that “equal (same) with an error of 0 μm or less” is more preferable, and “equal with same (same) with an error of 20 μm or less” is more desirable, and further “equal with same error (same) with an error of about 1 μm”. desirable.

More specifically, when the distance h between the light receiving element substrate 39 and the hologram element 33 is, for example, 3000 μm, when the distance d is set to, for example, about 100 μm, each of Λ1 and Λ2 is, for example, about 4 μm. , About 3.3 μm.

As shown in FIG. 2, with the above configuration, the light having the first wavelength λ1 from the first light source 25 is reflected by the information recording medium 21, and then the first and second diffractive regions 29, The first and second diffracted lights r11 and r12 diffracted by 31.
Cause Then, the diffracted light r11 converges on the first position P1 on the light receiving element substrate 39, and diffracted light r12
Converges to the second position P2 on the light receiving element substrate 39. At this time, the distance between the first position P1 and the second position P2 is about 100 μm.

The second wavelength λ from the second light source 27
The light having 2 is reflected by the information recording medium 21,
The first and second diffracted regions 29 and 31 are diffracted to generate first and second diffracted lights r21 and r22. Then, the first diffracted light r21 converges to the first position P1 on the light receiving element substrate 39 within an error range of about 10 μm, and the second diffracted light r22 falls within an error range of about 10 μm. , To the second position P2 on the light receiving element substrate 39.

A first light receiving element 35 and a second light receiving element 37 having a width of about 100 μm in the X-axis direction are arranged at the first position P1 and the second position P2, respectively.
Therefore, the diffracted lights r11 and r21 both converge on the first light receiving element 35, and the diffracted lights r12 and r22 both converge on the second light receiving element 37.

When the lens power is applied to the first diffraction area 29 and the second diffraction area 31, the diffracted light r1
1, r21 acts as a concave lens, diffracted light r12,
Lens power is applied to r22 so as to act as a convex lens. Therefore, a focus error signal by complementary (complementary spot size method) can be obtained based on the outputs from the first light receiving element 35 and the second light receiving element 37.

Further, by setting the distance d between the first and second light sources and setting the grating pitches Λ1 and Λ2 as described above,
The −1st order diffracted lights r11 ′, r12 ′, r21 ′ of the first and second wavelengths by the first and second diffraction regions 29 and 31.
The r22 ′ converges on the light receiving element substrate 39 to a third position P3, a fourth position P4, a fifth position P5, and a sixth position P6, which are separated from each other by about 100 μm (FIG. 2).

Then, the third position P3 and the fourth position P
A third light receiving element 4 having a width of about 100 μm in the X-axis direction at each of the fourth, fifth position P5 and sixth position P6.
The third, fourth light receiving element 45, fifth light receiving element 47, and sixth light receiving element 49 are arranged.

Therefore, the −1st-order diffracted lights r11 ′, r12 ′, r21 ′, r22 ′ of the first and second wavelengths are respectively the third light receiving element 43, the fourth light receiving element 45, the fifth light receiving element 47, It converges on the sixth light receiving element 49.

Therefore, as will be described later, the third and fourth
Based on the output signals from the light receiving elements 43 and 45, it is possible to obtain the tracking error signal of the DVD light flux having the first wavelength λ1.

Further, the tracking error signal of the CD-R light flux can be obtained from the output signals from the fifth and sixth light receiving elements 47 and 49 arranged at the fifth and sixth positions P5 and P6.

Although not shown, in the first embodiment of the optical device, the second light source 27 and the information are used in order to detect the tracking error of the light flux for CD (second wavelength λ2) by the three-beam method. A three-beam generation diffraction grating (not shown) is provided between the recording media 21. The three-beam generating diffraction grating (not shown) is provided, for example, on the surface of the diffraction element substrate (not shown) provided with the hologram element 31 on the opposite side to the surface provided with the hologram element 31. You can

Further, a seventh light receiving element 51 and an eighth light receiving element 53 are provided on both sides of the first and second light receiving elements 35 and 37 in order to detect the tracking error by the three-beam method. Further, ninth and tenth light receiving elements 55 and 57 are provided on both sides of the fifth and sixth light receiving elements 47 and 49, respectively.

With the above structure, the light flux for CD emitted from the second light source 27 is arranged in the tangential direction (Y-axis direction) of the information recording medium 21 by the three-beam generating diffraction grating (not shown). It is split into three light beams. At this time, the depth of the grating is appropriately set (for example, 2 at 650 nm).
It is more convenient to generate the diffractive action only at the wavelength of the light flux for CD by performing the phase modulation of nπ).

The three light beams are reflected by the information recording medium 21 and then are reflected by the first and second diffraction regions 2 respectively.
The diffracted light r21, r22, r2 is diffracted by 9, 31
The light receiving element 5 diffracted at the same diffraction angle as 1 ', r22' and arranged in the Y-axis direction on the light receiving element substrate 39.
5, 47 (49), 57 or light receiving elements 51, 35
(37), converges on 53. Therefore, the light receiving element 5
Based on the outputs from 1, 53, 55 and 57, it is possible to obtain the tracking error signal of the light flux for CD by the three-beam method.

FIG. 4 shows a more detailed structure of the first light receiving element 35, the second light receiving element 37, and the third to tenth light receiving elements 43 to 57 and their operation.

Here, FIG. 4A shows the diffracted light r11, r12, r11 ', r12 having the first wavelength λ1 to the first to tenth light receiving elements 35, 37, 43 to 57.
4B shows the relationship between each light receiving element and the spot of each diffracted light when ′ is incident, and FIG. 4B shows the diffracted light r21, r22, having the second wavelength λ2, to each light receiving element.
The relationship between the light receiving elements and the spots of the diffracted light when r21 'and r22' are incident is shown.

As shown in FIG. 4A, the first light receiving element 35 and the second light receiving element 37 are divided into three light receiving regions 35a, 35b, 35c in the Y-axis direction, respectively. Similarly, the light receiving element 37 has a light receiving area 37.
It is divided into a, 37b, and 37c.

Further, the third light receiving element 43 is divided into light receiving areas 43a and 43b in the Y-axis direction, and the fourth light receiving element 45 and the fifth light receiving element 47 similarly receive light receiving areas 45a and 45b and light receiving areas, respectively. It is divided into areas 47a and 47b.

Next, a method for obtaining the focus error signal, the tracking error signal, and the recording signal of the light of the first wavelength and the second wavelength based on the output from each light receiving element having the above configuration will be described.

First, with reference to FIG. 4A, a method of obtaining a focus error signal, a tracking error signal, and a recording signal of the DVD light flux having the first wavelength (λ1 = 650 nm) will be described.

In FIG. 4A, cross hatch marks 59 on the light receiving element represent spots of diffracted light r11 and r11 'by the first diffraction region 29. The hatch mark 61 represents the spot of the diffracted lights r12 and r12 ′ by the second diffraction area 31.

By the way, as described above, when the lens power is applied to the first diffraction area 29 and the second diffraction area 31, the + 1st order diffracted light r11 from the first diffraction area 29 is given.
Is given a concave lens power, and the + 1st order diffracted light r12 from the second diffraction region 31 is given a convex lens power. Therefore, the cross hatch mark 59 represents a spot of light having a concave lens power, and the hatch mark 61 represents a spot of light having a convex lens power. Therefore, the light receiving element 35
Based on the outputs from the light receiving regions 35a to 35c and the outputs from the light receiving regions 37a to 37c of the light receiving element 37,
A focus error signal of the DVD light flux having the first wavelength can be obtained.

More specifically, the light receiving regions 35b, 37
Let S1 be the sum of the outputs from a and 37c, and
When the sum of the output signals from 5a, 35c and 37b is S2, the focus error signal FE is FE = S1-S
Given by 2.

On the other hand, the tracking error signal of the DVD light flux of the first wavelength with respect to the information recording medium 21 is the light receiving areas 43a, 43b, 45a, 45b having the spot marks 59, 61 of the diffracted lights r11 ', r12'. It is possible to perform arithmetic detection based on the detection signal from. More specifically, the light receiving areas 43a, 45a, 43b, 4
When the output of 5b is D1, D2, D3, D4, these outputs become tracking error detection signals by the difference detection method (DPD).

The recording signal RF of the information recording medium 21
Is given by the sum of the outputs from the first light receiving element 35, the second light receiving element 37, the third light receiving element 43, and the fourth light receiving element 45. That is, the recording signal RF is RF = S1 + S2 + D
It is given by 1 + D2 + D3 + D4.

Next, with reference to FIG. 4B, a method of obtaining the focus error signal, tracking error signal, and recording signal of the CD light flux having the second wavelength (λ2 = 780 nm) will be described.

In FIG. 4B, cross hatch marks 59 represent spots of the diffracted lights r21 and r21 ', and hatch marks 61 are diffracted lights r22 and r22'.
Represents the spot.

The focus error signal FE of the CD light flux having the second wavelength is received by the light receiving regions 35a to 35c of the first light receiving element 35, as in the case of the light having the first wavelength λ1.
Also, calculation and detection can be performed based on the output signals from the light receiving regions 37a to 37c of the second light receiving element 37. More specifically, the focus error signal FE of the CD light having the second wavelength λ2 is the light receiving areas 35b, 37a, 37c.
Let S1 be the sum of the outputs from the light receiving areas 35a, 35
When the sum of the output signals from c and 37b is S2, FE
= S1-S2.

On the other hand, the tracking error signal TE of the light flux for CD is detected by three beams by the three beam method. More specifically, the eighth and tenth light receiving elements 5
When the sum of the outputs from 3, 57 is E and the sum of the outputs from the seventh and ninth light receiving elements 51, 55 is F,
The beam tracking error signal TE is given by TE = EF.

In the case of the light flux for CD, the recording signal RF of the information recording medium 21 has the sum of the outputs of the light receiving area 35b and the light receiving areas 37a and 37c as S1, and the light receiving area 37b and the light receiving areas 35a and 35c. The sum of outputs is S2, the sum of outputs of the light receiving area 47a of the fifth light receiving element 47 and the light receiving area 49a of the sixth light receiving element 49 is R1, and the light receiving area 47b of the fifth light receiving element 47 and the sixth light receiving element 49 are When the sum of the outputs of the light receiving region 49b is R2, it is given by RF = S1 + S2 + R1 + R2.

In the case of CD-R, the tracking error signal is the sum of the outputs of the light receiving regions 47a and 49a, which is R1.
Then, when the sum of the outputs of the light receiving regions 47b and 49b is R2, TE (pp / CD-R) = R1-R2 can also be obtained.

Therefore, according to the first embodiment, the light receiving areas 35a, 35b, 35c of the first light receiving element 35 and the light receiving areas 37a, 37b, 3 of the second light receiving element 37 are formed.
The output of 7c is the focus error signal FE (and the recording signal R for both the first wavelength light and the second wavelength light).
Used for detection of F).

The outputs of the third light receiving element 43 and the fourth light receiving element 45 are used exclusively for calculating the tracking error signal (and the recording signal RF) of the light flux for DVD.

The outputs from the seventh light receiving element 51, the eighth light receiving element 53, the ninth light receiving element 55, and the tenth light receiving element 57 are for calculating the three-beam tracking error signal TE of the CD light flux. Used only for.

Therefore, this first embodiment has the following advantages.

(1) Regarding the detection of the focus error signal, the signal system can be shared by the DVD light flux and the CD light flux.

(2) It is possible to completely separate the signal system for the focus error signal detection processing and the signal system for the tracking error signal detection processing, thus simplifying the structure of the signal processing system. be able to.

(3) With respect to the tracking error signal detection processing itself, the signal system can be completely separated for the DVD light flux and the CD light flux, and thus the signal processing system can be simplified.

FIGS. 5 and 6 show that when the conditions 1 and 2 are satisfied, the diffracted lights r11 and r21 of the first wavelength and the second wavelength by the first diffraction region 29 are on the light receiving element substrate 39. At substantially the same first position P1 and the diffracted lights r12 and r22 having the first wavelength and the second wavelength by the second diffraction region 31 converge at substantially the same second position P2 on the light receiving element substrate 39. Here's why.

FIG. 5A shows the + 1st-order diffracted light r11 and the -1st-order diffracted light r11 'having the first wavelength, which are diffracted by the first diffraction region 29 having the grating pitch Λ1.
FIG. 5B shows + 1st-order diffracted light r21 and −1st-order diffracted light r21 ′ having the second wavelength, which are diffracted by the first diffraction region 29.

Here, the lattice pitch Λ1 is the same as the condition 1
Is set to satisfy. Therefore, the + 1st order diffracted light r11 of the first wavelength λ1 by the first diffraction region 29 is generated.
The distance L11 between the incident position P11 on the surface of the light receiving element substrate 39 and the optical axis A1 determined by the 0th-order transmitted light of the first wavelength λ1 is defined as a first distance, and the second diffraction pattern is formed by the same diffraction region.
The light-receiving element substrate 39 for the + 1st-order diffracted light r21 having the wavelength λ2
When the distance L21 between the incident position P21 on the surface and the optical axis A2 defined by the 0th-order transmitted light of the second wavelength λ2 is defined as the second distance, the difference between the first distance L11 and the second distance L21. │
L11-L21 | is substantially equal to the distance d between the light emitting points of the first and second light sources.

Therefore, as shown in FIG. 5C in which FIG. 5A and FIG. 5B are superposed, the diffracted light r11, r
21 converges on substantially the same first position P1 on the light receiving substrate 39.

FIG. 6 shows that not only the diffracted lights r11 and r21 converge to the same first position P1 but also the second position P1.
It is shown that the diffracted lights r12 and r22 by the diffractive region 31 are also converged to the substantially same second position P2 on the light receiving element substrate 39.

More specifically, FIG. 6A shows ± first-order diffracted lights r11 and r11 'of the first wavelength by the first diffraction region 29 having the grating pitch Λ1 and the second diffraction region 31 having the grating pitch Λ2. ± first-order diffracted light r of the first wavelength λ1 due to
12, r12 'are shown. FIG. 6B shows the first diffraction region 2
The second-order ± 1st-order diffracted lights r21 and r21 ′ of the second wavelength 9
And the ± first-order diffracted light r of the second wavelength by the second diffraction region 31
22 and r22 'are shown.

The lattice pitches Λ1 and Λ2 are set so as to satisfy the above condition 1. Therefore, the first wavelength λ due to the first diffraction region 29 or the second diffraction region 31 is
The light-receiving element substrate 3 for the + 1st-order diffracted lights r11 and r12 of 1
The incident positions P11 and P12 on the 9th surface and the first wavelength λ1
Distance L11, L from the 0th-order transmitted light to the optical axis A1
12, where 12 is the first distance, the incident positions P21, P22 of the diffracted lights r21, r22 of the second wavelength λ2 by the same diffraction region on the surface of the light receiving element substrate 39, and 0 of the second wavelength λ2.
Distances L21 and L22 from the optical axis A2 determined by the next transmitted light
Is the second distance, the differences | L11-L21 | and | L12-L22 | between the first distance and the second distance are substantially equal to the distance d between the light emitting points of the first and second light sources.

Therefore, as shown in FIG. 6C in which FIG. 6A and FIG. 6B are overlapped, P11 and P21 are substantially equal to each other, and P12 and P22 are substantially equal to each other. . In other words, the first diffraction region 29
The diffracted lights r11 and r21 of the wavelengths and the second wavelengths converge on the same first position P1 on the light receiving element substrate 39, and the diffracted lights r12 of the first and second wavelengths by the second diffraction region 31. , R22 converge to substantially the same second position P2 on the light receiving element substrate 39.

By the way, the distance s1 between the incident positions P11 and P12 of the + 1st order diffracted lights r11 and r12 shown in FIG. 6A and the second wavelength λ2 shown in FIG.
Strictly speaking, the distance s2 between the incident positions P21 and P22 of the first-order diffracted lights r21 and r22 does not necessarily match.

Therefore, the first light source 25 and the second light source 2
The distance d between 7 and the grating pitches Λ1 and Λ2 of the first diffraction region 29 and the second diffraction region 31 are P11 and P21.
And P12 and P22 are the first and second light receiving elements 3
It must be determined so as to agree with each other within an error range of 5,37.

7 and 8 show the grating pitches Λ1 and Λ.
2 and a method of determining the distance d between the first and second light sources 25 and 27 will be described.

Referring to FIGS. 7 and 8, step S1
Then, the distance h between the light receiving element substrate 39 and the hologram element 33 is determined.

The optical axis A1 and the diffracted light r11
The distance L11 from the incident position P11 is determined. And
The diffraction angle θ11 of the diffracted light r11 is determined based on these values h and L11.

In step S2, the grating pitch Λ1 is determined by the diffraction formula based on the diffraction angle θ11 and the first wavelength value λ1 obtained in step S1.

In step S3, based on the grating pitch Λ1 of the first diffraction region 29 and the second wavelength value λ2,
The diffraction angle θ21 of the diffracted light r21 is determined.

In step S4, the incident position P21 of the diffracted light r21 is determined based on the diffraction angle θ21 obtained in step S3 and the distance h, and the distance L21 between the position P21 and the optical axis A2 is determined. To decide.

In step S5, the grating pitch Λ2 is determined so that the diffraction angle θ12 of the diffracted light r12 becomes equal to the diffraction angle θ21 of the diffracted light r21.

In step S6, the diffraction angle θ22 of the diffracted light r22 is determined by the diffraction formula based on the grating pitch Λ2 and the second wavelength value λ2. Further, P22 which is the incident position of the diffracted light r22 is determined from this diffraction angle θ22, and the distance L between this position P22 and the optical axis A2 is determined.
22 is decided.

In step S7, L12-L11 (= s
1) and d is determined as the intermediate position of L22-L21 (s2).

The grating pitches Λ1 and Λ2 and the distance d between the first and second light sources 25 and 27 determined by the above method are as follows, for example. For example, the distance h between the light receiving element substrate 39 and the hologram element 33 is 3000 μm.
m and the distance L11 is 500 μm,
The grating pitch Λ1 of the first diffraction area 29 is determined to be about 4.0 μm, and the grating pitch Λ2 of the second diffraction area 31 is about 3.
3 μm, the distance d between the light emitting points of the light source is about 1
It is determined to be 20 μm.

In the above case, the incident position P11,
The distance between P21 is about 11 μm, and the incident position P2
The distance between 1 and P22 is about 12 μm. Also, the above-
Incident points P11 ′, P12 ′, P2 of the first-order diffracted lights r11 ′, r12 ′, r21 ′, r22 ′ on the light receiving element substrate 39.
The intervals s4, s5, and s6 between 1'and P22 'are about 104 μm, about 120 μm, and about 130 μm, respectively.

Therefore, according to the above method, the first diffraction region 2
The + 1st order diffracted lights r11 and r21 according to
Within the error range of about m, both converge to substantially the same position on the light receiving element substrate 39, and the + first-order diffracted light r1
The distances d between the grating pitches Λ1 and Λ2 and the first and second light sources 25 and 27 are determined so that 2 and r22 also converge to substantially the same position on the light receiving tissue plate 39 within an error range of about 10 μm. It

9 to 11 show a second embodiment of the optical device according to the present invention.

As shown in FIGS. 9 to 11, the optical device according to the second embodiment is an optical device for reading information from an information recording medium, and includes a first light source 25 for outputting light of a first wavelength and a first light source 25. A second light source 27 that outputs light of two wavelengths, and a hologram element 133 that has a first diffraction region 129 and a second diffraction region 131 that diffracts the light of the first and second wavelengths,
First for receiving the diffracted light from the hologram element 133
A light receiving element substrate 39 provided with a light receiving element 35 and a second light receiving element 37, and the first diffraction region 129 and the second diffraction region 131 have the same grating pitch, and the direction u of each grating axis. , V are different from each other by a predetermined angle within 30 °, and the light emitting points of the first and second light sources 25 and 27 are mutually different in the X axis direction substantially orthogonal to the lattice axis directions u and v. The grating pitches of the first diffraction area 129 and the second diffraction area 131 are separated by a predetermined distance d, and the first diffraction area 129 (or the second diffraction area 1).
31), the + 1st-order diffracted light r11 (r
12) incident position P1 on the surface of the light receiving element substrate 39
(P2) and the optical axis A determined by the 0th order transmitted light of the first wavelength
The distance L11 (L12) with respect to 1 is defined as the first distance, and the incident position P1 (P2) of the + 1st-order diffracted light r21 (r22) of the second wavelength by the same diffraction region 129 (131) on the surface of the light receiving element substrate 39 is set. , The second distance L21 (L22) with respect to the optical axis A2 determined by the 0th-order transmitted light of the second wavelength
When the distance is defined as the first distance L11 (L12) and the second distance
Difference with distance L21 (L22) | L11-L21 | (| L
12-L22 |) is the first light source 25 (second light source 27)
Is set to be substantially equal to the distance d between the light emitting points of the first diffraction region 129 and the first diffraction region 129, 131.
The diffracted light of the wavelength converges on the first position P1 which is substantially the same on the light receiving element substrate,
The diffracted light having the wavelength and the second wavelength are determined so as to converge on the light receiving element substrate 39 to substantially the same second position P2 which is apart from the first position P1 by a predetermined distance in the Y-axis direction,
The first and second light receiving elements 35 and 37 are arranged at the first and second positions P1 and P2, respectively.

As best shown in FIG. 11, the first and third light receiving elements 35 and 37 are located at substantially the same position in the X-axis direction and both sides of the axis w connecting the optical axes A1 and A2. Located in.

The third to sixth light receiving elements 43 to 49 and the ninth and tenth light receiving elements are provided at predetermined positions on the light receiving element substrate 39.
Light receiving elements 55 and 57 are provided. Here, the 3rd and 4th
The light receiving elements 43 and 45 have −1st order diffracted lights r11 ′ and r12 ′ having the first wavelength from the diffraction areas 129 and 131.
For receiving light. In addition, the fifth and sixth light receiving elements 47 and 49 are provided from the diffraction areas 129 and 131, respectively.
It is for receiving the −1st order diffracted light r21′r22 ′ having the second wavelength. The ninth and tenth light receiving elements 55,
57 is for receiving the three beams for CD.

The dimensions of the light receiving elements 55 and 57 in the Y-axis direction are determined to cover the incident light beam diameter (for example, about 80 μm) (for example, about 90 μm) and do not overlap each other in the vicinity of the X-axis. The tilt angle is determined. Here, this tilt angle may be determined by tilt angles α and β of the diffraction axis of the hologram, and the light receiving elements may have the same angle. In practice, for example, α = β = 10 ° can be designed.

The third and fourth light receiving elements 43 and 45 have X
They are arranged on both sides of the axis w at substantially the same position in the axial direction and are separated from each other by a predetermined distance in the Y-axis direction. Further, the fifth and sixth light receiving elements 47 , 49 are also arranged on both sides of the axis w at substantially the same position in the X axis direction and separated from each other by a predetermined distance in the Y axis direction. However, the distance between the fifth and sixth light receiving elements 47, 49 is equal to the third,
It is larger than the distance between the fourth light receiving elements 43 and 45. Also,
The ninth and tenth light receiving elements 55 and 57 are arranged on both sides of the fifth and sixth light receiving elements 47 and 49, respectively. That is, the ninth and tenth light receiving elements 55 and 57 are the same as the light receiving element 4
7, 49 are arranged side by side in the Y-axis direction.

The light receiving elements 43 and 45 and the light receiving element 47,
49 are spaced apart in the X-axis direction, and the distance between them is, for example, about 210 μm.

More specifically, the second embodiment of this optical device has the following configuration.

That is, in this optical device, as shown in FIGS. 9 to 11, the first light source 25 that outputs the light of the first wavelength λ1 and the second light source 27 that outputs the light of the second wavelength λ2.
And. Here, the first wavelength λ1 is, for example, DV
650 nm for D, and the second wavelength λ2 is, for example, C
It is 780 nm for D. The distance d between the light emitting points of the light sources 25 and 27 is set to about 104 μm, for example.

The directions of the grating axes u and v of the diffraction areas 129 and 131 have angles α and β with respect to the Y axis, respectively. The angles α and β are set to a value of about 8.6 degrees, for example. In this case, the grating axes u and v of the diffraction areas 129 and 131 have an angle of about 17.2 degrees with each other. The grating pitch Λ of the first diffraction area 129 and the second diffraction area 131 of the hologram element 133 are both set to about 4.0 μm.

The distance between the light receiving element substrate 39 and the hologram element 133 is set to, for example, 3000 μm as in the case of the first embodiment. With the above configuration, the first wavelength emitted from the first light source 25 is emitted. After being reflected by an information recording medium (not shown), the light flux for DVD having is diffracted by the first diffractive region 129 and the second diffractive region 131 to generate ± first-order diffracted light r11, r12, r11 ′, r12 ′. Occurs. Then, the + 1st-order diffracted light r11 by the first diffraction area 129 is converged on the first light receiving element 35, and the + 1st-order diffracted light r12 by the second diffraction area is converged on the second light receiving element 37. On the other hand, the −1st order diffracted lights r11 ′ and r1 by the first diffraction region 129 and the second diffraction region 131.
2 ′ converges on the third light receiving element 43 and the fourth light receiving element 45, respectively.

The light flux for CD having the second wavelength from the second light source 27 is reflected by an information recording medium (not shown) and then diffracted by the first and second diffraction areas 129 and 131. , ± 1st-order diffracted light r21, r22, r21 ′, r
22 '. Then, the + 1st-order diffracted light r21 by the first diffraction area 129 is converged on the first light receiving element 35, and the + 1st-order diffracted light r22 by the second diffraction area 131.
Converges on the second light receiving element 37. On the other hand, the −first-order diffracted lights r21 ′ and r22 ′ by the first diffraction region 129 and the second diffraction region 131 are respectively received by the fifth light receiving element 4.
The light is converged on the seventh and sixth light receiving elements 49.

When the lens power is applied to the first diffraction area 129 and the second diffraction area 131, the diffracted light r1
1 and r21 are given a concave lens action, and diffracted light r1
It is designed so that a convex lens action is given to 2, r22. Therefore, as in the case of the first embodiment, it is possible to obtain the focus error signal by the complementary spot size method based on the outputs from the first light receiving element 35 and the second light receiving element 37.

As will be described later, similar to the case of the first embodiment, the DV having the first wavelength is based on the outputs from the third light receiving element 43 and the fourth light receiving element 45.
A tracking error signal of the D light flux can be obtained.

Further, the fifth and sixth light receiving elements 47, 49
CD-R having a second wavelength based on the output signal from the
It is possible to obtain a tracking error signal of the luminous flux for use.

Although not shown, also in the second embodiment of this optical device, in order to detect the tracking error of the light flux for CD (second wavelength λ2) by the three-beam method, the second light source 27 and the information recording medium are combined. A diffraction grating (not shown) for generating three beams is provided between them. The three-beam generating diffraction grating (not shown) is formed, for example, on the surface of the diffraction element substrate (not shown) provided with the hologram element 131, which is opposite to the surface provided with the hologram element 131. It

Further, in order to detect the tracking error by the three-beam method, ninth and tenth light receiving elements 57 and 59 are provided on both sides of the fifth and sixth light receiving elements 47 and 49, respectively.

With the above structure, the three CD light beams emitted from the second light source 27 are aligned in the tangential direction (Y-axis direction) of the information recording medium by the three-beam generating diffraction grating (not shown). Is decomposed into the luminous flux of. This 3
The light flux of the book is reflected by the information recording medium, diffracted by the first and second diffractive regions 129 and 131, and diffracted at the same diffraction angle as the diffracted lights r21 ′ and r22 ′, and the light receiving element substrate. The light receiving elements 55, 47, 57 or the light receiving elements 5 arranged side by side in the Y-axis direction on 39.
5, 49, 57 converge upwards . Therefore, for example, based on the outputs from the light receiving elements 55 and 57, it is possible to obtain the tracking error signal of the CD light flux by the three-beam method.

FIG. 12 shows the first to sixth light receiving elements 3
5, 37, 43, 45, 47, 49 and the ninth and tenth light receiving elements 55, 57 are shown in more detail. More specifically, FIG. 12A shows a case where a DVD light beam is incident on the light receiving element, and a hatch mark 201 represents a spot of the DVD light beam on the light receiving element. Also, FIG. 12 (b)
Represents the case where a light flux for CD enters the light receiving element,
The hatch mark 203 represents the spot of the CD light flux on the light receiving element.

As shown in FIGS. 12 (a) and 12 (b), as in the case of the first embodiment, the first light receiving element 35 and the second light receiving element 37 are substantially along the Y-axis direction. Are divided into three light receiving areas 35a, 35b, 35c and light receiving areas 37a, 37b, 37c.

The third, fourth, fifth and sixth light receiving elements 43, 45, 47 and 49 respectively have two light receiving regions 43a, 43b; 45a and 45 substantially along the Y-axis direction.
b; 47a, 47b; 49a, 49b.

With the above arrangement, the light receiving regions 35a, 3
The outputs from 5b and 35c and the light receiving regions 37a and 37
The focus error signals of the DVD light flux of the first wavelength λ1 and the CD light flux of the second wavelength λ2 can be obtained based on the outputs from b and 37c.

More specifically, the light receiving regions 35b and 37 are formed.
The sum of the outputs from a and 37c is S1, and the light receiving area 35
When the sum of the outputs from a, 35c and 37b is S2, the focus error signal FE is given by FE = S1-S2.

The tracking error signal of the light flux for DVD is similar to that of the first embodiment, and the third light receiving element 43 is used.
The outputs D1 and D3 from the light receiving areas 43a and 43b and the outputs D2 and D4 from the light receiving areas 45a and 45b of the fourth light receiving element 45, respectively.

The tracking error signal TE of the light flux for CD has the output of the ninth light receiving element 55 as E and the tenth
When the output of the light receiving element 57 is F, it is given by TE = EF.

In the case of CD-R, the tracking error signal is the sum of outputs of the light receiving regions 47a and 49a, which is R1.
And when the sum of the outputs of the light receiving regions 47b and 49b is R2, TE (pp / CD-R) = R1-R
Obtained by 2.

Further, the recording signal RF for the DVD light flux is expressed as RF = S1 + S2 + D1 + D2 + D3 + D4.

Also, the recording signal RF for the light flux for CD is used.
R1 is the sum of the outputs of the light receiving area 47a of the fifth light receiving element 47 and the light receiving area 49a of the sixth light receiving element 49, and the light receiving area 47b of the fifth light receiving element 47 and the light receiving area 49b of the sixth light receiving element 49 are When the sum of the outputs of R2 is R2, it is expressed as RF = S1 + S2 + R1 + R2.

Therefore, the second embodiment has the following advantages as in the first embodiment.

(1) For the detection of the focus error signal, the signal system can be shared by the DVD light flux and the CD light flux.

(2) The signal system for the focus error signal detection processing and the signal system for the tracking error signal detection processing can be completely separated, thereby simplifying the structure of the signal processing system. be able to.

(3) With respect to the tracking error signal detection processing itself, the signal system can be completely separated for the DVD light flux and the CD light flux, and thus the signal processing system can be simplified.

In the optical device of the second embodiment,
Arrangement positions of the first light source 25 and the second light source 27, and lattice axis directions u and v of the first and second diffraction regions 129 and 131.
The positions of the first and second light receiving elements 35 and 37 are determined as follows, for example.

As shown in FIG. 11, first, the optical axis A1
The light flux for DVD having the first wavelength λ1 emitted from
A virtual diffracted light, which is diffracted by a virtual diffraction grating having the same grating pitch as the first and second diffraction regions and oriented in an arbitrary direction, is drawn on the light receiving element substrate 39 (hereinafter referred to as a diffraction circle). Is defined as q1. Similarly, the CD light flux having the second wavelength λ2 emitted from the optical axis A2 is diffracted by a virtual diffraction grating having the same grating pitch as the first and second diffraction regions and oriented in an arbitrary direction. In this case, the diffraction circle drawn by the virtual diffracted light on the light receiving element substrate 39 is q2.

Then, the distance d between the optical axes A1 and A2 is determined so that the diffraction circle q1 contacts the diffraction circle q2.

As shown in FIG. 11, the diffraction circle q
The positions P1 and P2 in the vicinity of where 1 and q2 are in contact with each other are the positions where the first light receiving element 35 and the second light receiving element 37 are arranged. The positions P1 and P2 of the light receiving elements 35 and 37 are
May be at any position as long as the distance between the diffraction circles q1 and q2 is 50 μm or less (preferably 20 μm or less).

Next, the first and second diffraction areas 129 and 131
Of the grating axes u and v of the diffracted regions 129 and 131 are diffracted lights r11, r21 and r1 of the first and second wavelengths.
2 and r22 are determined so as to converge on the light receiving elements 35 and 37.

As described above, the first and second light sources 25, 2
7 and the first and second light receiving elements 35 and 37.
And the lattice axis directions u and v of the first and second diffractive regions 129 and 131 are determined, the + 1st-order diffracted light r11 of the first wavelength and the second wavelength by the first diffractive region 129, Both r21 can be made to converge on the light receiving element 35, and the + 1st order diffracted lights r12 and r22 of the first wavelength and the second wavelength by the second diffraction region 131 can both be made to converge on the light receiving element 37.

[0131]

As described above, according to the present invention,
With a two-wavelength optical system, complementary focus error detection for the two wavelengths can be realized.

Therefore, it is possible to realize miniaturization, simplification, cost reduction and high efficiency in a DVD and CD-R compatible pickup or reproducing device.

[Brief description of drawings]

FIG. 1 is a schematic perspective view of a first embodiment of an optical device according to the present invention.

FIG. 2 is an explanatory diagram showing a light trace of diffracted light in the first embodiment.

FIG. 3 is a schematic diagram of a hologram element in the first embodiment.

FIG. 4 is an explanatory plan view showing configurations and actions of the first to tenth light receiving elements in the first embodiment.

FIG. 5 is an explanatory diagram illustrating a manufacturing method of the first embodiment.

FIG. 6 is an explanatory diagram illustrating the manufacturing method of the first embodiment.

FIG. 7 is an explanatory diagram illustrating the manufacturing method of the first embodiment.

FIG. 8 is an explanatory diagram illustrating the manufacturing method of the first embodiment.

FIG. 9 is a schematic perspective view of a second embodiment of the optical device of the present invention.

FIG. 10 is a schematic diagram of a hologram element in the second embodiment.

FIG. 11 is an explanatory plan view showing the positions of two light sources and a light receiving element in the second embodiment.

FIG. 12 is an explanatory plan view showing a configuration of first to tenth light receiving elements in the second embodiment.

FIG. 13 is an explanatory diagram illustrating focus error detection by the spot size method.

[Explanation of symbols]

25: first light source 27: second light source 29, 129: first diffraction area 31, 131: second diffraction area 133: hologram element, 35: first light receiving element 37: second light receiving element 39: light receiving element substrate 43, 45, 47, 49, 51, 53, 55, 57: third to tenth light receiving elements

Front page continuation (58) Fields surveyed (Int.Cl. ⁷ , DB name) G11B 7/135 G11B 7/125

Claims (6)

(57) [Claims] 1. An optical device for reading information from an information recording medium, comprising a first light source for outputting light of a first wavelength, a second light source for outputting light of a second wavelength, and the first and second wavelengths. A hologram element having a first diffraction area and a second diffraction area for diffracting the light, and a light receiving element substrate provided with a first light receiving element and a second light receiving element for receiving the diffracted light from the hologram element, The first diffractive area and the second diffractive area have a grating array in which the grating axis directions are parallel to each other and the grating pitches are different from each other, and the light emitting points of the first and second light sources are orthogonal to the grating axis. The grating pitches of the first diffraction region and the second diffraction region are separated from each other by a predetermined distance in the direction in which the diffracted light of the first wavelength is received by the first diffraction region or the second diffraction region. The incident position on the element substrate surface The distance between the optical axis determined by the zero-order transmitted light of the first wavelength (L1
1; L12) as the first distance, and between the incident position of the diffracted light of the second wavelength on the light receiving element substrate surface by the same diffraction region and the optical axis determined by the 0th-order transmitted light of the second wavelength. When the distance (L21; L22) is the second distance, the first distance
Difference between the distance and the second distance (| L11-L21 |; | L12
−22 |) is substantially equal to the distance between the light emitting points of the first and second light sources, and the diffracted light of the first or second wavelength on the surface of the light receiving element substrate is diffracted by the first diffraction region. and the incident position, the distance between the incident position of the by the second diffraction area, to the light receiving device substrate surface of the diffracted light of the same wavelength (| L11-L12 |; | L21-
22 |) is set to be substantially equal to the interval between the light emitting points, so that the diffracted lights of the first wavelength and the second wavelength by the first diffraction region are moved to substantially the same first position on the light receiving element substrate. The diffracted lights of the first wavelength and the second wavelength which are converged and which are caused by the second diffraction region are substantially the same on the light receiving element substrate.
So as to converge to the position, the first, the respective to the second position the first optical device, characterized in that the second light-receiving elements are arranged. 2. The diffracted light to the first and second positions is the + 1st order diffracted light by the first and second diffractive areas, and the diffracted light by the first and second diffractive areas. Third-fourth-first-order diffracted lights of the first wavelength and the second wavelength, which are separated from each other at a predetermined interval so that they can be received by independent light-receiving regions that do not overlap each other on the light-receiving element substrate.
The distance between the light emitting points of the first and second light sources and the grating pitch of the first diffraction region and the second diffraction region are set so as to converge to the fifth and sixth positions. Item 2. The optical device according to Item 1. 3. The −1st-order diffracted light of the first wavelength by the first diffraction region and the second diffraction region converges on the third and fourth positions, and the first diffraction region and the second diffraction region generate the first-order diffracted light. The -1st-order diffracted light of the second wavelength converges on the fifth and sixth positions, and based on the detection signals from the light receiving elements arranged at the third and fourth positions , the tracking error signal for the first wavelength. And obtaining a tracking error signal for the second wavelength based on a signal from the light receiving element divided into a plurality of regions by the fifth or sixth position or a straight line substantially orthogonal to these positions in the grating axis direction. The optical device according to claim 2, wherein the optical device is a device. 4. An optical device for reading information from an information recording medium, a first light source for outputting light of a first wavelength, a second light source for outputting light of a second wavelength, and the first and second wavelengths. A hologram element having a first diffraction area and a second diffraction area for diffracting the light, and a light receiving element substrate provided with a first light receiving element and a second light receiving element for receiving the diffracted light from the hologram element, The first diffractive region and the second diffractive region have the same grating pitch, and the grating axis directions are different from each other by a predetermined angle within 30 °, and the light emitting points of the first and second light sources are different from each other. , The grating pitches of the first diffraction area and the second diffraction area are separated from each other by a predetermined distance in a direction substantially orthogonal to the grating axis direction, and the grating pitch of the first diffraction area or the second diffraction area is The diffracted light of the first wavelength The distance between the incident position on the substrate surface of the light receiving element and the optical axis defined by the 0th-order transmitted light of the first wavelength is the first
The distance is defined as the incident position of the diffracted light of the second wavelength on the surface of the light receiving element substrate by the same diffraction region, and 0 of the second wavelength.
When the distance from the optical axis determined by the next transmitted light is the second distance, the difference between the first distance and the second distance is the first and second distances.
The distance between the light emitting points of the light source is set to be substantially equal to each other, and the orientations of the first diffraction region and the second diffraction region are such that the diffracted light of the first wavelength and the second wavelength by the first diffraction region is , Converges to substantially the same first position on the light receiving element substrate, and diffracted light of the first wavelength and the second wavelength by the second diffraction region is on the light receiving element substrate in the light emitting point separation direction. in orthogonal directions determined so as to converge to substantially the same second position a predetermined distance from said first position, said first, said respective to the second position first, and characterized in that the second light-receiving elements are arranged Optical device. 5. The optical device according to claim 1, wherein a focus error signal is obtained based on signals from the first light receiving element and the second light receiving element. 6. The diffracted light to the first and second positions is + 1st order diffracted light by the first and second diffractive regions, and the diffracted light by the first and second diffractive regions. A -1st-order diffracted light of one wavelength is obtained on the basis of a signal from a light-receiving element arranged at the third and fourth positions on the light-receiving substrate, and a tracking error signal of the light of the first wavelength is obtained, and Fifth position or sixth position where the −1st-order diffracted light of the second wavelength by the first diffraction region or the second diffraction region converges on the light receiving substrate, or a plurality of regions in a straight line orthogonal to these positions in the lattice axis direction. The optical device according to claim 4, wherein a tracking error signal of the light of the second wavelength is obtained based on a signal from the light receiving element divided into two.