JP2001118282A - Optical pickup device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical pickup device generating laser beams having different wavelengths, which is capable of reducing the deviation of the optical axis of light which is emitted from plural elements and reflected by a prism to improve the yield and capable of attaining cost reduction. SOLUTION: The prism 32 is provided with wavelength selective reflecting surfaces 106, 107 corresponding respectively to plural laser elements 30, 31, and these reflecting surfaces are arranged in parallel to each other. Plural laser elements 30, 31 are arranged in the same side to the prism 32.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical pickup device used for recording and reproducing signals on a plurality of optical recording media used at a plurality of laser wavelengths.

[0002]

2. Description of the Related Art Normal density optical disc media reproduction and CD
-R (Compact Disc-Recordable)
For reproduction and recording in e), a laser having a wavelength of about 780 nm is required. On the other hand, when reproducing a high-density optical recording medium such as a DVD, a short-wavelength laser of, for example, about 650 nm is required. For example, Japanese Patent Application Laid-Open No. Hei 9-120568 discloses an optical recording medium that requires a different laser wavelength as described above, which can be recorded and reproduced by one optical pickup device.

FIG. 10A shows an optical pickup device described in the above publication, wherein 1 is a first laser element for outputting a laser having a short wavelength of 655 nm, for example, and 2 is 780 for example.
a second laser element that outputs a long-wavelength laser
Is a prism, and the prism 3 transmits the laser from the first laser element 1 and makes the laser from the second laser element 2 coincide with the optical axis of the transmitted laser from the first laser element 1. Is to be reflected. Reference numeral 4 denotes a diffraction element having a hologram pattern 5 which is an uneven groove formed on a surface perpendicular to the optical axis from the prism 3. 6a and 6b are light receiving element groups, 7 is an objective lens, and 8 is an optical recording medium. The laser elements 1 and 2, the light receiving element groups 6a and 6b, and the diffraction element 4 are entirely sealed and fixed by a housing 9.

In the optical pickup device shown in FIG. 10A, a light beam from the first laser element 1 or the second laser element 2 is transmitted through the diffraction element 4 as zero-order light. The light beam transmitted through the diffraction element 4 is condensed by the objective lens 7 and forms a reading spot on the recording surface of the optical recording medium 8. The light beam reflected by the recording surface passes through the objective lens 7 and returns to the diffraction element 4. In the diffraction element 4, light is diffracted by the hologram pattern 5,
The light is guided to the light receiving element groups 6a and 6b as +1 order light 10 and −primary light 11, respectively. A focus error signal, a tracking error signal, and a reproduced signal are obtained from detection signals from the light receiving element groups 6a and 6b by a circuit (not shown).

In the above configuration, as shown in FIG. 10 (B), the prisms 3 are made of reflecting films 94 and 95 (however, reflecting films 95) in order to make the arrangement structure of the laser elements 1 and 2 and the prism 3 compact. Can transmit the laser beam from the laser element 1). A prism 3A having two prisms 96 and 97 bonded together is used, and the laser elements 1 and 2 are arranged on the opposite side of the prism 3A. Is also used.

The prism 3A is manufactured by the steps shown in FIG. First, as shown in FIG.
4, a plurality of glass plates 96A provided on one side are attached,
Cut along the parallel cutting surface 98. Similarly, a plurality of glass plates 97A each having the reflective film 95 (FIG. 11B shows a state after lamination and cutting) are similarly bonded and cut in the same manner. Then, as shown in FIG. 11B, these cut pieces are bonded to each other on the bonding surface 99 so that the positions of the reflective films 94 and 95 are aligned.
Then, the prism 3A is obtained by cutting and polishing along a cut surface 100 perpendicular to the bonding surface 99.

[0007]

When the prism 3A having such a structure is obtained by the above-described mass production process in order to reduce the manufacturing cost, the difference in thickness between the respective glass plates 96A and 97A and the accumulation of the difference. 10A and 10B due to a positional shift when the substrates are bonded as shown in FIG.
As shown by the dotted line in (B), the relative positions of the reflection films 92 and 93 are shifted, for example, such that the reflection film 93 is shifted to the right or left in the drawing.

When the reflection films 94 and 95 are displaced in this way, the distance from one laser element 2 to the reflection film 95 is displaced as shown in FIG.
The beam 101 directed to the optical recording medium 8 is deviated from a normal position as shown by a dotted line, and an error occurs at the position where the reflected light from the optical recording medium 8 forms an image. Such an error causes an error in the focus error signal, the tracking error signal, and the reproduction signal, thereby lowering the yield.

In order to prevent the occurrence of such an error, an adjusting mechanism is provided on a mounting base on which the laser elements 1 and 2 are mounted so as to adjust the positions of the laser elements 1 and 2 in the beam 101 direction. However, the structure becomes complicated and the cost is increased.

In view of the above problems, the present invention provides an optical pickup device having a plurality of laser elements for generating laser beams having different wavelengths and a diffractive element for guiding light reflected from an optical recording medium to a light receiving element. It is an object of the present invention to provide an optical pickup device having a structure capable of reducing a shift of an optical axis of light emitted from a laser element, thereby improving a yield and achieving a cost reduction.

Another object of the present invention is to provide an optical pickup device having a structure capable of adjusting the deviation of the optical axis by simple means and further improving the yield.

[0012]

According to a first aspect of the present invention, there is provided an optical pickup device comprising: a plurality of laser elements for outputting laser beams having different wavelengths corresponding to a plurality of types of optical recording media having different wavelengths of laser light used; A prism for guiding laser light from these laser elements to a recording surface of an optical recording medium, a diffraction element for diffracting light reflected from the optical recording medium, and a light receiving element for receiving the diffracted light diffracted by the diffraction element An optical pickup device including an element assembly, wherein the prism has a wavelength-selective reflecting surface corresponding to each of the plurality of laser elements, and these reflecting surfaces are arranged in parallel with each other, and Are characterized by being arranged on the same side with respect to the prism.

As described above, if the plurality of reflecting surfaces of the prism are configured to be parallel, the prism can be manufactured by cutting a glass plate provided with a reflecting film and pasting it. In such a prism, the error of the optical axis substantially depends on the thickness of the glass plate, and the accumulation of the thickness error and the positioning error between the laminated glass plates do not occur.

According to a second aspect of the present invention, there is provided an optical pickup device for outputting first and second laser beams having different wavelengths corresponding to first and second optical recording media having different wavelengths of laser light to be used. Element, optical means for guiding laser light from these laser elements to the recording surfaces of the first and second optical recording media, and diffractive element for diffracting reflected light from the first and second optical recording media An optical pickup device comprising: a light receiving element assembly for receiving the diffracted light diffracted by the diffraction element; wherein the prisms correspond to the first and second laser elements, respectively. Surfaces, and these reflecting surfaces are arranged parallel to each other,
A plurality of laser elements are arranged on the same side with respect to the prism, a first light receiving element for focus error detection for receiving diffracted light generated by the first laser element and diffracted by the diffraction element; Generated by the second laser element,
And a second light receiving element for focus error detection that receives the diffracted light diffracted by the diffractive element, provided at a position relatively rotated about the optical axis of the reflected light incident on the diffractive element, The position of the diffraction element is adjusted in at least two directions: a direction parallel to the optical axis of the reflected light incident on the diffraction element and a rotation direction about the optical axis, and the first and second light receiving elements are adjusted. The spots of the respective diffracted lights are combined.

As described above, in the optical pickup device of the second aspect, the first and second light receiving elements for detecting a focus error are relatively rotated about the optical axis of the reflected light incident on the diffraction element. Position. That is, the first and second light receiving elements for focus error detection are set at positions shifted in the rotation direction about the optical axis of the reflected light. When the diffraction element is moved in a direction parallel to the optical axis, the distance between two spots on the light receiving element of the two types of diffracted light can be adjusted. If the distance is properly adjusted, the two spots can be adjusted to desired positions of the respective focus error detecting light receiving elements by rotating the diffraction element about the optical axis.

[0016]

FIG. 1 is a block diagram showing an embodiment of an optical pickup device according to the present invention. In FIG. 1, reference numeral 30 denotes a first laser element which is a semiconductor laser chip which generates a laser beam having a wavelength of 785 nm, and 31 denotes a second laser element which is a semiconductor laser chip which generates a laser beam having a wavelength of 655 nm. Reference numeral 32 denotes a prism for commonly directing the laser beams generated by the laser elements 30 and 31 to the diffraction element 33 side.

As shown in FIG. 2A, the laser elements 30 and 31 are fixed to a mounting table 102 mounted on a housing 70 and arranged on the same side as the prism 32. 33, a diffraction element provided between the objective lens 7 and the prism 32; 34, a light receiving element assembly including a plurality of photodiodes; 7, an objective lens held by a holder 71;
Is an optical recording medium composed of an optical disk.

The laser elements 30, 31, the prism 3
2, the diffraction element 33 and the light receiving element assembly 34
0 is attached. A drive coil 72 is attached to the holder 71 of the objective lens 7. The driving coil 72 includes a focusing coil and a tracking coil. These holder 71 and housing 70 are provided with housing 73
Attached to

As shown in FIG. 2A, the prism 32
Is composed of two triangular prisms 103 and 104, one parallelogram prism 105, and reflection films 106 and 107 provided on a joint surface between the prisms 103 and 104 and the prism 105 and constituting a reflection surface. The reflective film 106
A hot mirror surface which efficiently reflects the laser light having a wavelength of 785 nm generated by the first laser element 30 and transmits the laser light having a wavelength of 655 nm is formed. The reflection film 107 has a wavelength 65 generated by the second laser element 31.
A cold mirror surface that efficiently reflects 5 nm laser light and transmits 785 nm wavelength laser light generated by the first laser element 30 is formed.

As shown in FIG. 2B, the prism 32 is formed by bonding glass plates 103A, 105A, and 104A, cutting along the cut surface 109, and then cutting the cut surface 110.
Can be manufactured by cutting along the surface and polishing. In this case, the reflection film 106 is made of a glass plate 103A, 1
The reflective film 107 is provided on one of the opposing surfaces of the reflective film 107A.
Is provided on one of the glass plates 104A and 105A.

If the prism 32 is manufactured in such a process, the processing accuracy of the prism simply depends on the thickness of the glass plate 105A, and the bonding step described with reference to FIG. Accuracy can be easily increased because the accumulation of errors and thickness errors is eliminated. For this reason, without adjusting the mounting position of the laser elements 30 and 31 with respect to the mounting base 102,
The deviation of the optical axis of the reflected light from the laser elements 30 and 31 in the prism 32 can be reduced.

Next, the operation of the optical pickup device will be described in detail, and the adjustment of the deviation of the optical axes of the two types of reflected light from the prism 32 will be described. FIG. 3 is a view of the diffraction element 33 and the light receiving element assembly 34 viewed from the objective lens 7 side in the optical axis direction. As shown in FIG. 3, the diffraction element 33 has hologram patterns 35 to 38 formed of concave and convex grooves for performing diffraction.
Is provided in an area divided into four by vertical and horizontal lines 81 and 82 passing through the center 33a. The diffraction element 33 is shown in FIG.
As shown in (A), the distance L1 from the diffraction element 33 to the image plane 40 of the primary light 100 and the distance L1 passing through the diffraction element 33
Ratio L1 / L2 of next light 101 to distance L2 to image surface 41
Is set to 1 as shown in FIG. 4 (B).

In FIG. 1, when the first laser element 30 is driven, the laser light of a long wavelength emitted from the first laser element 30 is reflected by the reflection film 106 of the prism 32, and The transmitted light is condensed by the objective lens 7 and reflected by the recording surface of the optical recording medium 8.
Returns to the diffraction element 33. In the diffraction element 33, part of the reflected light is converted into hologram patterns 35 to 38 shown in FIG.
, And the light receiving element assembly 34 is irradiated with the diffracted light 42.

When the second laser element 31 is driven, the laser light having a short wavelength is applied to the reflecting film 10 of the prism 32.
The light reflected by the optical recording medium 7 travels along the same path as described above, and the return light from the optical recording medium 8 is diffracted by the diffractive element 33, and the diffracted light 43 is irradiated to the light receiving element assembly 34. Since the diffracted light 43 having a short wavelength has a smaller diffraction angle than the diffracted light 42 having a long wavelength, the diffracted light 43 is applied to a position near the optical axis 45 of the light receiving element assembly 34.

As shown in FIG. 3A, the light receiving element assembly 34 includes one light receiving element group including light receiving elements 46 to 49 and the other light receiving element group including light receiving elements 51 to 54. . One light receiving element group includes the first laser element 30.
, Which receives the diffracted light of the long-wavelength laser light from the light source. Since the long wavelength has a large diffraction angle, it is arranged farther from the optical axis 45 than the other light-receiving element group that receives the short-wavelength diffracted light. .

A first light receiving element 49 included in one of the light receiving element groups is for detecting a focus error, and is a diffracted light of a long wavelength laser light generated by the first laser element 30 from the hologram pattern 38. Is received as a spot. The first light receiving element 49 includes a pair of light receiving sections 5.
8 and 59 are arranged adjacently via a detection line 60, and generate a focus error signal by the knife edge method or the Foucault method. Also, the light receiving elements 46, 47, 4
Reference numeral 8 denotes a hologram pattern 3 for returning light of a long wavelength.
The light is diffracted at 6, 37, and 35, and receives the diffracted light as a spot.

The second light receiving element 51 included in the other light receiving element group is for detecting a focus error, and is a diffracted light of the short wavelength laser light generated by the first laser element 31 from the hologram pattern 36. Is received as a spot. The second light receiving element 51 includes a pair of light receiving sections 6.
Numerals 1 and 62 are arranged adjacently via a detection line 63, and generate a focus error signal by the knife edge method or the Foucault method. Further, the light receiving elements 52, 53, 5
4 is a hologram pattern 3 of the diffraction element 33, respectively.
It receives the diffracted lights from 7, 35, and 38 as spots.

When a long wavelength laser beam is used, the sum of the outputs of the light receiving elements 46 to 49 of one of the light receiving element groups is used as a reproduction signal. Further, the difference between the outputs of the light receiving elements 47 and 48 is obtained and used as a track error signal as a phase difference method. When using laser light of a short wavelength, the sum of the outputs of the light receiving elements 51 to 54 of the other light receiving element group is used as a reproduction signal. The difference between the outputs of the light receiving elements 52 and 53 is used as a track error signal as a phase difference method.

As shown in FIG. 3A, the detection line 60 of the first light-receiving element 49 and the detection line 63 of the second light-receiving element 51 are perpendicular to the plane of the light entering the diffraction element 33. The optical axis of the reflected light (usually this optical axis is the center 33 of the diffraction element 33)
a) is set at a position relatively rotated around the center. The detection lines 60 and 63 are twisted with respect to the optical axis of the reflected light incident on the diffraction element 33, that is, non-parallel to the optical axis and the extension of the detection lines 50 and 63 is the light Set in a direction that does not intersect the axis. In this example, the detection lines 60 and 63 are set parallel to each other.

In FIG. 1, reference numeral 65 denotes a focus control circuit, which receives the outputs of the first light receiving elements 49 and 51 as inputs and obtains a focus error signal, and focuses the driving coil 72 in accordance with the focus error signal. By energizing the coil, the position of the objective lens 7 in the focus direction is controlled. Reference numeral 66 denotes a tracking control circuit, and the light receiving elements 47 and 48 and the light receiving elements 52 and 5
A tracking error signal is obtained by inputting the output of the objective lens 3 as an input, and the position of the objective lens 7 in the tracking direction is controlled by energizing a tracking coil of the drive coil 72 in accordance with the tracking error signal.

FIG. 5 is a diagram for explaining spots on the light receiving element. FIGS. 5A to 5C are explanatory diagrams of spots when reproducing at a long wavelength. FIG. 5A shows the shape of the spot when the focal point is deeper than the recording surface position of the optical recording medium 8 in the case of reproducing with a long wavelength, with the light receiving elements 46 to 49 being indicated by oblique lines. In this case, in the first light receiving element 49 for focus error detection, the spot 66a is mainly formed on one light receiving section 58. FIG. 5 (B)
Is the shape of the spot 66b when the focus coincides with the recording surface position of the optical recording medium 8. At this time, the light receiving units 58 and 59
Are equal. FIG. 5C shows the shape of the spot 66c when the focal point is located before the recording surface position of the magneto-optical recording medium 8. At this time, in the light receiving element 49, a spot 66c is formed mainly on the other light receiving portion 59.

Accordingly, when the outputs of the light receiving sections 58 and 59 are V58 and V59, respectively, and the focus error signal is FE, FE = V58-V59, and the focus position is determined by monitoring the sign of the focus error signal FE. can do.

FIGS. 6A to 6C are explanatory diagrams of spots when reproducing at a short wavelength. In FIG. 5A, the shape of the spot when the focal point is deeper than the recording surface position of the optical recording medium 8 is indicated by oblique lines. In this case, in the second light receiving element 51 for focus error detection, a spot 67a is mainly formed on one of the light receiving portions 61 as described above. FIG.
(B) shows the shape of the spot 67b when the focal point coincides with the recording surface position of the optical recording medium 8, in which case the light receiving section 6
The light receiving amounts of 1, 62 become equal. FIG. 6C shows the shape of the spot 67c when the focal point is located before the recording surface position of the magneto-optical recording medium 8. In this case, the spot 67c is mainly formed on the other light receiving portion 62.

Therefore, also in this case, the outputs of the light receiving sections 61 and 62 are V61 and V62, respectively, and the focus error signal is F.
Assuming that E, FE = V61−V62, and the focus position can be determined by monitoring the sign of the focus error signal FE.

FIG. 7A is a diagram showing an example of the configuration of the housing 70 of the optical pickup device of the present invention. The housing 70 includes the laser elements 30 and 31 and the light receiving element assembly 3.
Optical components 69 such as 4 are attached. A cylindrical body 74 is fixed to the front surface of the housing 70 by fixing means 75 such as solder. The cylindrical body 74 holding the diffraction element 33 is rotatably mounted on the cylindrical body 74 before being fixed by the fixing means 77, as shown by an arrow 78, and the center line of the cylindrical body 76 as shown by an arrow 79. It is mounted so that the position can be adjusted in the direction, that is, in the optical axis direction. After adjusting the position of the cylindrical body 76 in the direction parallel to the rotation direction and the optical axis, the cylindrical body 76 is fixed by fixing means 77.

Conventionally, as shown in FIG. 7B, a cylindrical body 76 having a diffractive element is fixed to a housing 70 only in the direction of rotation about the optical axis and fixed by fixing means 75.

FIG. 8 shows the detection lines 60 and 63 of the first and second light receiving elements 49 and 51 for detecting a focus error, and the diffracted light from the hologram pattern 38 or 36 among the diffracted lights 42 and 43 from the diffractive element 33. FIG. 7 is a diagram for explaining a method of the present invention for matching spots 66 and 67 of FIG. FIG. 8 (A)
For example, because the arrangement positions of the laser elements 30 and 31 are deviated from the design positions, the optical axis 45A of the long-wavelength laser light returning from the optical recording medium 8 to the diffraction element 33 and the short-wavelength laser light The figure shows a spot position shift on the light receiving elements 46 to 54 when the optical axis 45B of the return light is shifted. In this case, in a state where the spot 67 of the diffracted light from the hologram pattern 36 is aligned with the detection line 63 of the second light receiving element 51 for detecting a focus error, the hologram pattern 38 traveling toward the first light receiving element 49 for detecting a focus error In the case where the spot 66 of the diffracted light from the laser beam deviates from the detection line 60, the following adjustment is performed.

As shown in FIG. 3A, the detection lines 60 and 63 of the first and second light receiving elements 49 and 51 correspond to the diffraction element 33.
Is parallel to the horizontal dividing line 82 in the drawing of the hologram pattern, and the detection line 6 is viewed from the objective lens 7 side.
0 and 63 are on both sides of the extension of the dividing line 82. In the example of FIG. 8, the distance between the spots 66 and 67 is larger than the distance between the detection lines 60 and 63 in the direction perpendicular to the dividing line 82. In this case, first, the position is adjusted in a direction to move the diffraction element 33 away from the objective lens 7 along the optical axis, that is, in a direction to approach the light receiving element assembly 34 side. Thus, as shown in FIG. 8B, the spots 66 and 67 approach the optical axes 45A and 45B along the lines 83 and 84, respectively. By adjusting this movement amount, the spot 6
The distance between the spots 6 and 67 can be adjusted so as to be reduced to the extent that the distance between the spots 66 and 67 and the distance between the detection lines 60 and 63 substantially coincides with each other.

After adjusting the distance between the spots 66 and 67 in this way, in order to adjust the displacement between the spot 66 and the detection line 60 or between the spot 67 and the detection line 63, the optical axis 45 is moved as shown by an arrow 85. The diffraction element 33 is rotated as a center. Thus, as shown in FIG. 8C, the spots 66 and 67 are aligned with the detection lines 60 and 63 of the first light receiving elements 49 and 51, respectively.

On the contrary, the interval between the spots 66 and 67 in the direction perpendicular to the dividing line 82 is
In the case where the distance is smaller than 3, the position of the diffraction element 33 is adjusted in a direction to approach the objective lens 7 side, and the spots 66 and 67 are adjusted.
Make adjustments to increase the spacing between them. Further, the adjustment is also performed by rotating the diffraction element 33 about the optical axis 45.

By performing such adjustment, even if the two laser elements 30 and 31 are not installed at optically equivalent positions, both of the two spots 66 and 67 are connected to the detection line 6.
0, 63. According to the experiment, even if the installation error of the laser elements 30 and 31 is about ± 50 μm or the installation angle error of the prism 32 is about ± 1 degree, the spots 66 and 67 are detected by the above method. Assembly adjustment can be performed according to 60 and 63.

Such adjustment can be performed by adjusting the position of the cylindrical body 76 in the rotation direction indicated by the arrow 78 shown in FIG. 7A, or by adjusting the position in the direction parallel to the optical axis indicated by the arrow 79. However, in practice, the position adjustment of the diffraction element 33 in the direction parallel to the optical axis is about ± 100 μm, and the rotation direction is also about 2 to 3 degrees at most.
The fitting structure for position adjustment by the cylindrical bodies 74 and 76 shown in FIG. For example, the cylindrical body 76 to which the diffraction element 33 is fixed is held by a holder whose position can be adjusted in a direction parallel to the optical axis and in a rotational direction about the optical axis, and while monitoring the positions of the spots 66 and 67, When the spots 66 and 67 match the detection lines 60 and 63, the cylindrical body 76 may be directly fixed to the housing 70 by a fixing means such as solder or an adhesive.

Next, the displacement β of the spots 66 and 67 with respect to the light receiving element assembly 34 due to the adjustment of the magnification β of the diffraction element 33 and the direction parallel to the optical axis 45 of the diffraction element 33 will be considered. As shown in FIG.
Is not 1, when the diffraction element 33 is moved in a direction parallel to the optical axis 45 as shown by an arrow 86, FIG.
As shown in (C), the image plane 41 of the zero-order light 101, which is the transmitted light of the diffraction element 33, does not move, but the image plane 40 of the ± first-order light 100 moves in the direction of the arrow 86. That is, the image plane 40 of the ± first-order light 100 and the image plane 41 of the zero-order light 101 before moving.
Is the image plane 4 of the ± primary light 100 after the movement.
It is not equal to the distance L4 between 0 and the image plane 41 of the 0th-order light 101 (L3 ≠ L4).

On the other hand, as shown in FIG. 4B, when the magnification β of the diffractive element 33 is 1, even if the diffractive element 33 is moved in a direction parallel to the optical axis 45, ± first-order light 100 and zero-order light Both image planes 40 and 41 of 101 do not move. In FIG. 4, the ± primary light 100 shows only one primary light.

In the present invention, since the adjustment is performed by moving the diffraction element 33 in a direction parallel to the optical axis, if the image plane 40 of the diffracted light moves in a direction parallel to the optical axis 45 by this adjustment work, the focus error signal Causes an offset.
Therefore, in order to adjust the diffraction element 33 in a direction parallel to the optical axis, it is preferable that the magnification β of the diffraction element 33 is 1 or as close to 1 as possible. The influence of the offset of the focus error signal on the jitter of the reproduced signal is large. FIG. 9 (A)
FIG. 9 is a diagram showing a change in jitter with respect to a change in magnification β of the diffraction element 33.

The spot 66 or 67 is connected to the detection line 60
Or 63, the other spot 67 or 66 is 50 μm in the direction orthogonal to the detection line 63 or 60.
In the case of deviation, when the magnification β is in the range of about 0.75 to 1.33, there is no practical problem, that is, about 1% increase from the lowest value of jitter. When the magnification β of the diffraction element 33 is out of this range, the jitter is sharply deteriorated, and the practical use cannot be tolerated. This magnification β is 0.80 or more,
More preferably 1.25 or less, 0.95 or more,
If it is 1.05 or less, it can be substantially regarded as 1.0.

In practicing the present invention, in FIG. 3A, when viewed in the optical axis direction of the reflected light incident on the diffraction element 33,
At least one of the angles θ3 and θ4 between the lines 86 and 87 connecting the center 35 of the diffraction element 33 and the centers of the detection lines 60 and 63 and the detection lines 60 and 61 is set to 10 degrees or more and 80 degrees or less. It is preferable that In other words, when viewed in the optical axis direction of the reflected light incident on the diffraction element 33, the detection line 6
It is preferable that at least one of each optical axis of the diffracted light traveling toward 0 and 61 and each of the twists of each of the detection lines 60 and 61 be within the range of the angle. Because this angle θ3
If θ4 is less than 10 degrees, the relative movement of the spot 66 or 67 with respect to the detection lines 60 and 63 when the diffraction element 33 is moved in the direction parallel to the optical axis 45 becomes insufficient, and adjustment becomes difficult. is there. If the angle θ3 or θ4 is higher than 80 degrees and 90 degrees or less, it becomes difficult to align the spot 66 or 67 with the detection line 60 or 63 when the diffraction element 33 is rotated.

FIGS. 3B and 3C show another example of the hologram pattern provided on the diffraction element 33. FIG. FIG. 3B shows that the hologram pattern is divided into five parts, and the hologram pattern 38 is used for detecting a focus error during reproduction of a long wavelength.
The hologram patterns 36a and 36b are used for focus error detection during reproduction of a short wavelength. Hologram pattern 3
Reference numerals 5 and 37 are used for track error detection by the phase difference method at both long and short wavelengths, as in the above-described example.

In the example of FIG. 3C, the hologram pattern is divided into four parts, and the division lines 90 and 91 are divided into the detection lines 60 and 61.
It is formed to be inclined with respect to. In this example, the hologram pattern 36 is used for detecting a focus error when reproducing a short wavelength. The hologram pattern 38 is used for detecting a focus error when reproducing a long wavelength. The hologram patterns 35 and 37 are used for detecting a track error by the push-pull method.

FIG. 9B shows another example of the light receiving element assembly 34, in which the light receiving elements 47 of the one light receiving element group and the light receiving elements 52 of the other light receiving element group are combined into one light receiving element 92. The light receiving element 48 of the one light receiving element group and the light receiving element 53 of the other light receiving element group are combined into one light receiving element 93, whereby the number of pins of the light receiving element assembly 34 is reduced.

In the above embodiment, the knife edge method or Foucault method was used for focus error detection, and the phase difference method or push-pull method was used for track error detection. However, the beam size method and astigmatism were used for focus error detection. The method and the track error detection can be applied to a three-beam method and the like. The present invention is also applicable to a case where three types of laser light are used.

[0052]

According to the first aspect of the present invention, the prism is provided with a wavelength-selective reflecting surface corresponding to each of the plurality of laser elements, and these reflecting surfaces are arranged in parallel with each other. The prism can be manufactured by cutting a glass plate provided with a reflective film and pasting the same. In such a prism, the positional deviation of the reflecting surface depends only on the positional deviation of the glass plate, and there is no sticking error, so that the processing accuracy is improved and the optical axis alignment is facilitated. For this reason, the yield of products is improved, and it is possible to contribute to a reduction in manufacturing costs.

According to the second aspect, in addition to the first aspect, by further adjusting the position of the diffractive element in a direction parallel to the optical axis and in a rotational direction about the optical axis, the laser light of any of the long and short wavelengths is obtained. Can be adjusted to the light receiving element for focus error detection. For this reason, it is possible to tolerate the displacement of the laser element, the manufacturing error of the prism, the manufacturing error of the dimensions, and the like, thereby contributing to the improvement of the yield and the reduction of the cost of the manufacturing equipment, and the cost of the optical pickup device. Can be further reduced.

[Brief description of the drawings]

FIG. 1 is a configuration diagram showing an embodiment of an optical pickup device according to the present invention.

2A is a layout view of a prism and a laser element of FIG. 1, and FIG. 2B is an explanatory view of a manufacturing process of the prism.

FIG. 3 is a diagram of the diffraction element and the light receiving element assembly viewed in the optical axis direction in the present embodiment.

4A is a correlation diagram between the diffraction element and the image plane when the magnification of the diffraction element is not 1; FIG. 4B is a correlation diagram between the diffraction element and the image plane when the magnification of the diffraction element is 1; , (C), (D)
6A and 6B are correlation diagrams between the diffraction element and the image plane when the diffraction elements of FIGS. 7A and 7B are moved in a direction parallel to the optical axis.

FIGS. 5A, 5B, and 5C show a case where the focal point is deeper than the recording surface position of the optical recording medium when reproducing at a longer wavelength in the embodiment of FIG. The shape of the spot when the focal point coincides with the recording surface position of the optical recording medium and the focal point is located before the recording surface position of the magneto-optical recording medium.

FIGS. 6A, 6B, and 6C show a case where the focal point is deeper than the recording surface position of the optical recording medium when reproducing at a shorter wavelength in the embodiment of FIG. The shape of the spot when the focal point coincides with the recording surface position of the optical recording medium and the focal point is located before the recording surface position of the magneto-optical recording medium.

FIG. 7A is a cross-sectional view illustrating an example of a position adjusting mechanism of a diffraction element employed in the present invention, and FIG. 7B is a cross-sectional view illustrating a conventional diffraction element mounting structure.

FIGS. 8A to 8C are diagrams illustrating a method for adjusting the position of a diffraction element in the present embodiment.

FIG. 9A is a correlation diagram between a diffraction element and jitter,
(B) is a figure which shows the other example of arrangement | positioning of the light receiving element of this invention.

FIG. 10A is a configuration diagram showing a conventional optical pickup device, and FIG. 10B is a diagram showing an example of a conventional prism.

FIGS. 11A and 11B are diagrams showing a manufacturing process of a prism of a conventional optical pickup device.

[Explanation of symbols]

30: first laser element, 31: second laser element, 3
2: prism, 33: diffraction element, 34: light receiving element assembly, 35 to 38: hologram pattern, 40, 41: image plane, 42, 43: diffracted light, 45: optical axis, 46 to 48: light receiving element, 49 : First light receiving element, 51: second light receiving element, 52 to 54: light receiving element, 58, 59, 61, 62:
Light receiving unit, 60, 63: detection line, 65: focus control circuit, 66: tracking control circuit, 66, 66a to 66
c, 67, 67a to 67c: spot, 70: housing, 7
1: holder, 72: drive coil, 73: housing,
74, 76: cylindrical body, 75, 77: fixing means, 92, 9
3: light receiving element, 102: mounting base, 103, 104: triangular prism, 105: parallelogram prism, 106, 1
07: reflective film

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Toru Kineri 1-13-1, Nihonbashi, Chuo-ku, Tokyo TDK Corporation F-term (reference) 5D119 AA41 AA43 BA01 EC47 FA05 FA08 JA07 JA13 JA27 KA04

Claims (2)

[Claims] 1. A plurality of laser elements which output laser beams having different wavelengths corresponding to a plurality of types of optical recording media having different wavelengths of laser light to be used, and optically record laser light from these laser elements. An optical pickup device comprising: a prism that guides a recording surface of a medium; a diffraction element that diffracts light reflected from the optical recording medium; and a light receiving element assembly that receives the diffracted light diffracted by the diffraction element. The prism has a wavelength-selective reflecting surface corresponding to each of the plurality of laser elements, and the reflecting surfaces are arranged in parallel with each other, and the plurality of laser elements are arranged on the same side with respect to the prism. An optical pickup device, comprising: 2. A first and a second laser element for outputting laser beams having different wavelengths corresponding to first and second optical recording media having different wavelengths of laser light to be used, and these laser elements. Optical means for guiding the laser light from the optical disc to the recording surfaces of the first and second optical recording media; a diffractive element for diffracting the reflected light from the first and second optical recording media; A light receiving element assembly for receiving the diffracted light, wherein the prism has a wavelength-selective reflecting surface corresponding to the first and second laser elements, respectively. The reflecting surfaces are arranged in parallel with each other, the plurality of laser elements are arranged on the same side with respect to the prism, and the focal point receives diffracted light generated by the first laser element and diffracted by the diffractive element. First for error detection The light receiving element and the second light receiving element for focus error detection for receiving the diffracted light generated by the second laser element and diffracted by the diffractive element are light of reflected light incident on the diffractive element. The diffraction element is provided at a position relatively rotated about an axis, and the diffraction element is arranged in at least two directions of a direction parallel to an optical axis of reflected light incident on the diffraction element and a rotation direction about the optical axis. An optical pickup device wherein the positions of the respective diffracted lights on the first and second light receiving elements are adjusted by adjusting the position.