JP2001028145A - Optical head device and disk recording/reproducing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To increase the light utilization efficiency of a second light source by preventing the generation of a side beam during the use of a second wavelength light source while permitting the generation of a side beam during the use of a first wavelength light source. SOLUTION: A semiconductor laser device 11 is provided with a first light source 1a for emitting a first wavelength light beam, and a second light source 1b for emitting a second wavelength light beam different from the first wavelength light beam. A diffraction grating 12 has a grating groove formed such that its 1st order diffraction efficiency is almost zero for a light beam from the first light source 1a, and a 1st order diffraction light is emitted for a light beam from the second light source 1b.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical head device which is effective when reading or recording signals recorded on various optical recording media (digital video disc (DVD), compact disc (CD), etc.). .

[0002]

2. Description of the Related Art In recent years, in the field of recording media, the diameter of a conventional CD on which audio or digital data is recorded (1.
DVDs that have the same size but allow high-density recording have been developed. Since the DVD has a high recording density, the wavelength of light (780 n
m), a beam with a shorter wavelength (650 nm) is required.

[0003] As a reproducing apparatus, a reproducing apparatus capable of reproducing both a CD system and a DVD system is desired.
Therefore, as an optical head device (optical pickup) using a multi-wavelength type semiconductor array, one having a light source for CD (wavelength 780 nm) and a light source for DVD (wavelength 650 nm) has been developed.

[0004] This optical head device has a first light source and a second light source, and has a diffraction grating that is guided by a light beam from any of the first and second light sources. The diffraction grating is
In particular, it separates a CD light beam into three beams. The light beam emitted from the diffraction grating passes through the hologram, passes through the collimator lens, becomes collimated light, and enters the objective lens. The light collected by the objective lens is applied to the recording surface of the disk. The light reflected from the disc passes through the objective lens and collimator lens,
It is incident on the hologram. The hologram diffracts the reflected light and guides it to a photodetector using a photodiode. The photodetector has a focus error signal, a tracking error signal,
Outputs a read signal.

[0005]

(A1) In the above-described optical head device, when a CD is read, a laser beam having a wavelength of 780 nm from a light source is input to a diffraction grating and output as three beams. One of the three beams is a main beam, and the remaining two are sub beams.
Here, the intensity ratio between the main beam and the sub beam is 8: 1.
It is about.

Next, in the DVD reading state, a laser beam having a wavelength of 650 nm from the light source also passes through the diffraction grating. For this reason, originally unnecessary side beams are generated. As a result, the efficiency of the main beam decreases, and naturally the light receiving efficiency of the main beam also decreases in the photodetector that receives the reflected light from the disk. Therefore, the signal C / N
There is a problem that worsens. In order to improve the C / N ratio of the signal, it is conceivable to increase the emission amount of the light source for DVD. However, it is more likely that the semiconductor laser will be used beyond the maximum rating and the reliability of the device will be reduced. There's a problem.

(A2) Therefore, in the present invention, in order to solve the problem (A1), a side beam is generated when the light source of the second wavelength is used, but when the light source of the first wavelength is used. It is an object of the present invention to provide an optical head device capable of preventing generation of a side beam and improving the light use efficiency of the first light source.

(B1) Recently, a laser light emitting element having a plurality of light sources at extremely close positions and switching and emitting a plurality of laser beams has been developed. For this reason, when it is necessary to generate a specific side beam for each laser beam, mechanical switching of the diffraction grating makes the entire apparatus mechanically complicated and structurally large. Problem arises.

(B2) Therefore, the present invention solves the problem of (B1) by using a laser light emitting element having a plurality of light sources at extremely close positions without increasing the size of the entire structure. It is an object of the present invention to provide an optical head device capable of generating a specific side beam.

(C1) In the conventional optical head device, a (1/4) λ plate is provided near the objective lens, and in this portion, linearly polarized light (P-polarized light) is transmitted to the light transmission system.
, And from reflected light to linearly polarized light (S-polarized light). This is because the S-polarized light reflected from the optical disk is polarized in the hologram into first-order diffracted light and guided to a photodetector. This hologram has a function that the efficiency of the 0th-order diffracted light is large for P-polarized light and the efficiency of the first-order diffracted light is large for S-polarized light.

It is preferable to use a hologram having high light use efficiency as the above hologram. However, when such a polarizing element system ((1/4) λ plate and hologram) is used, the amount of light received by the photodetector fluctuates due to the birefringence of the disk. For this reason, when the amount of birefringence of the disk is larger than the specification, there arises a problem that a reproduced signal largely changes. In the case of DVDs, because the standards are strict, those with a birefringence larger than the specification are not on the market, but those with the birefringence larger than the specification are on the CD. In addition, in the pickup device using the above-mentioned polarizing element system, the amount of received light fluctuates, which greatly affects the reproduction performance. As described above, when the optical pickup using the multi-wavelength type semiconductor array is used, the hologram is shared by the DVD and the CD. Therefore, when the polarization hologram is used, there is a problem that the reproduction signal largely fluctuates due to the birefringence of the CD. appear.

(C2) In view of the above, an object of the present invention is to provide an optical head device having an optical layout with good reproduction performance for both DVD and CD.

(D1) In the conventional multi-wavelength optical head device, the optical axis of the first light source for DVD and the optical axis of the second light source for CD are set with respect to the optical axis of the objective lens. Are arranged symmetrically. However, in such an arrangement, the light emitted from the first light source and the second light source is obliquely incident on the objective lens, and the performance of the reproduction signal is deteriorated, and the DVD and the CD are not emitted. However, there is a problem that the difference between the best inclination angles becomes larger.

(D2) In order to solve the problem of (D1), the present invention provides an optical head device using a semiconductor laser array, which has a small difference between the best tilt angles of DVD and CD and has good reproduction signal performance. It is intended to provide.

(E1) The optical axis of the light source for the CD and the optical axis of the objective lens must be set as described above in order to provide an optical layout in which the difference between the best tilt angles of the DVD and the CD is small and the reproduction performance of the reproduction signal is good. It is possible to combine. However, if the center of the hologram is maintained in alignment with the optical axis of the objective lens in this way, the optical axis of the DVD light source and the center of the hologram deviate, so that the focus error signal during DVD reproduction decreases. Problem arises.

(E2) Accordingly, the present invention relates to the above (E1)
An object of the present invention is to provide an optical head device capable of obtaining a focus error signal of higher quality for both DVD and CD.

(F1) In a conventional optical pickup using a multi-wavelength type semiconductor laser array, since the light source for DVD and the light source for CD are separated, the light source is projected on the hologram in the optical axis direction. The position does not match the center of the hologram. For this reason, there is a problem that the quality of the focus error signal is deteriorated. In order to improve this, it is preferable to arrange the hologram as far as possible from the semiconductor laser array.

On the other hand, since the hologram is shared by the DVD and the CD, it is preferable that the level of the reproduced signal does not change due to the birefringence of the disk. Therefore, it is conceivable to use a non-polarized hologram. When a non-polarized hologram is used, in the light transmission system, the 0th-order light of this hologram is irradiated onto the disk via the objective lens, and in the reflection system, the + 1st-order light of this hologram is guided to the photodetector. However, in the light transmission system, -1st-order light is generated as stray light, and in the reflection system, 0th-order light is generated as stray light. This stray light causes deterioration in the quality of the reproduced signal. In order to reduce such stray light, it is preferable to arrange a hologram near the semiconductor laser array and increase the diffraction angle.

As described above, with respect to the quality of the focus error signal, it is better that the distance between the semiconductor laser array and the hologram is longer, and to reduce stray light, the shorter the distance between the semiconductor laser array and the hologram is, the better. There are conflicting demands for good.

(F2) Therefore, the present invention relates to the above (F)
An object of the present invention is to provide an optical head device having an optimum distance between a semiconductor laser array and a hologram with respect to the problem 2).

(G1) Also, when assembling an optical system using a multi-wavelength semiconductor laser, high precision is required for positioning between components. If the arrangement relationship of the plurality of components deviates from the predetermined relationship, a desired performance cannot be obtained as the reproduction performance of the reproduction signal. In particular, in an optical system commonly used for DVD and CD laser beams, it is necessary to obtain good reproduction performance when reproducing any disc. For this purpose, it is necessary to devise a method of positioning the components.

(G2) Accordingly, the present invention provides a method for mounting a hologram in an optical head device, which can reduce the mounting accuracy of a semiconductor laser and reduce the influence of deteriorating reproduction performance even in such a relaxed state. The purpose is to provide.

[0023]

(A3) In order to achieve the object of (A2), the present invention provides a first light source for emitting a light beam of a first wavelength, A second light source that is disposed at substantially the same position and emits a light beam having a second wavelength different from the first wavelength, and a first-order diffraction efficiency is substantially equal to the light beam from the first light source. A diffraction grating that emits first-order diffracted light with respect to the light beam from the second light source. Thereby, the second
The light use efficiency of the light source can be increased.

(B3) In order to achieve the object of the above (B2), the present invention provides a light emitting means for emitting a plurality of laser beams from a close position, a light receiving element for receiving reflected light from an optical disk, In an optical head device having a hologram that diffracts reflected light from an optical disk toward the light receiving element, between the hologram and the light emitting unit, the plurality of laser beams may be incident on separated positions. A diffraction grating is arranged, and diffraction is performed on a laser beam emitted from at least one of the light sources. This is effective for obtaining an optical integrated device applicable to a plurality of disk systems without increasing the size of the entire optical system.

(C3) In order to achieve the object of (C2), the present invention uses a non-polarized blaze hologram as an element for guiding reflected light to a photodetector.
According to this means, it is possible to obtain a light use efficiency of about 1.5 times that of a non-polarized rectangular hologram, so that the reproduction performance of DVD can be improved. In addition, by using a non-polarized hologram, a stable reproduction signal can be obtained without a change in the amount of received light due to birefringence of a CD.

(D3) According to the present invention, in order to achieve the object of (D2), the second CD of the CD is located near the optical axis of the objective lens.
The optical axis of the light source is aligned. This allows
Oblique incidence occurs on the objective lens for DVDs, but does not occur for CDs. In the DVD and CD compatible objective lenses, the aberration caused by oblique incidence of DVD is astigmatism, so that the best tilt angle and the performance deterioration of the reproduction signal are small, and the difference between the best tilt angle of DVD and CD is small.
In addition, the reproduction signal reproduction performance can be improved.

(E3) In order to achieve the object of (E2), the present invention is characterized in that the center of the hologram is arranged in the middle of the optical axes of the first and second light sources. As a result, the amplitude of the focus error signal during CD reproduction is
The amplitude of the focus error signal at the time of reproduction also becomes an appropriate amplitude, and the quality of the focus error signal of the entire apparatus can be improved.

(F3) According to the present invention, when the distance between the first light source and the second light source is δ, the first and second light sources and the hologram are provided. Is in the range of 20δ to 40δ.

(G3) According to the present invention, in order to attain the object of the above (G2), a marker is provided on a hologram at a position of a light source for CD on the hologram and a position of projection of a photodetector in an optical axis direction. It is provided. When a hologram, a light source for a CD, and a photodetector are assembled according to the markers attached in this manner, the light receiving spot on the photodetector is larger than that of a CD during DVD reproduction. Even if the laser is mounted in a slightly rotated state, the performance for DVD reproduction will not be significantly degraded.

[0030]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows an embodiment of the present invention. The semiconductor laser device 11 is a so-called one-chip laser. The semiconductor laser device 11 includes a light source 1b for CD (outputting a beam having a wavelength of 780 nm) and a light source 1a for DVD (outputting a beam having a wavelength of 650 nm). Have close proximity. The light emitted from the so-called multi-wavelength semiconductor laser device 11 passes through the diffraction grating 12, passes through the hologram 13, and further enters the collimator lens 14. The light emitted from the collimator lens 14 becomes collimated light, which is parallel light, and enters the objective lens 15. Light traveling from the light source toward the recording medium is called light transmission. The light converged by the objective lens 15 is a pit train (information recording track) on the recording medium.
Is irradiated.

The light reflected from the recording medium is transmitted to the objective lens 1
5. The light passes through the collimator lens 14 and enters the hologram 13. In the hologram 13, the reflected light is refracted and guided to the photodetector 16.

As shown in FIG. 2, for example, the photodetector 16 has four divided photodiodes 6A, 6B, 6C and 6D for a main beam (one beam), and side (sub) elements disposed on the side portions thereof. Photodiode 6E for beam,
6F.

FIG. 3 shows the relationship between a pit row of a CD and three beams. Ideally, the main beam follows the center line of the read pit row (track), and the front and rear sub-beams track the left and right ends of the pit row, respectively.
Therefore, in the photodetector 16, if a difference between the photoelectric conversion outputs obtained from the photodiodes 6E and 6F is obtained, it can be used as a tracking error signal.

The feature of the present invention is that the characteristics of the diffraction grating 12 are as follows.

FIG. 3A shows the characteristics of the depth of the phase grating, the zero-order diffraction efficiency, and the first-order diffraction efficiency in the diffraction grating 12. In the case of a conventional diffraction grating, the phase grating depth with respect to the wavelength of the second light source for CD is (1/3) π
(A in FIG. 3B). In such a case,
Even in the first light source for DVD, an unnecessary side beam is generated because the first-order diffraction efficiency is improved.

However, the diffraction grating 12 according to the present invention
The wavelength of the beam of the first light source for DVD is λ1, the refractive index is n, and the grating groove depth h0 is h0 = λ1 / (n-1).

Here, the phase grating depth φ0 of the diffraction grating 12
Is calculated from φ0 = 2π · h0 · (n−1) / λ. The relationship between the phase grating depth φ0 and the diffraction efficiency η is as shown in FIG. Here, DVD
Since the wavelength of the beam of the first light source is λ1, φ0 = 2π · h0 · (n−1) / λ1 = 2π, where the 0th-order diffraction efficiency η0 = 100% and the 1st-order diffraction efficiency η1 = 0 %. The fact that the first-order diffraction efficiency is 0 means that no sub-beam (diffracted light) is generated. The depth of the groove of the phase grating of the diffraction grating 12 for realizing this is about five times (b in FIG. 3B).

That is, in the present invention, when a light source (light source for DVD) that does not require a sub-beam is used in the optical path of the optical pickup, the wavelength of the light source is m / (n).
-1) A diffraction grating having a depth of a grating groove of (m is a natural number, n is the refractive index of the diffraction grating) is used. This allows
In the DVD mode, no side beam is generated, the light receiving efficiency of the main beam can be improved, and the C / N of the signal can be improved without increasing the emission amount of the light source.

When the second light source (light source for CD) is used, the operation is as follows. That is, the diffused light emitted from the light source 1 b enters the diffraction grating 12. Since the wavelength of the second light source is λ2, the phase grating depth φ0 of the diffraction grating 12 is φ0 = 2π · λ1 / λ2 λ2 = 780 nm and λ1 = 650 nm, so that φ0 =
1.67π.

At this time, as can be seen from the characteristics of FIG. 3A, the 0th-order diffraction efficiency η0 = about 75%, the 1st-order diffraction efficiency η1 = about 10%, and the 0th-order main beam and ± 1st-order Side beam is generated. This enables the diffraction grating 12 to realize detection of a tracking error signal called a so-called three-beam method.

As described above, according to the optical head device of the present invention, when the light source 1b for CD is used, a side beam necessary for detecting a tracking error signal can be generated, and the light source 1a for DVD Is used, the loss of light emitted from the light source 1a can be suppressed without generating a side beam. Thereby, an appropriate relationship between the irradiation amount of the light source 1a and the reproduction signal can be maintained, and the quality and reliability of the optical pickup device can be improved.

The present invention is not limited to the above embodiment.

This optical head device is, for example, a DVD-R
When used in an apparatus for detecting a tracking error signal by using a differential push-pull method like AM, it may be configured as follows.

That is, the grating groove depth h0 = λ2 / (n−1) is set so that a side beam is generated only when a DVD light source is used. The side beam at this time is used for a differential push-pull method for detecting a tracking error detection signal.

The grating groove depth h0 = λ1 / (n−
1), two diffraction gratings of h1 = λ2 / (n−1) are configured to realize a differential push-pull method for detecting a tracking error detection signal when using a light source for DVD; When a light source for CD is used, the tracking error signal may be detected by a three-beam method.

As described above, various embodiments are possible for the structure of the diffraction grating having two or more kinds of grating depths.

That is, as shown in FIG. 4A, on one surface of the diffraction grating 21, two types of uneven gratings having different groove directions are provided. On the other hand, in the diffraction grating characteristics, as described in the first embodiment, for example, when the light source for DVD is used, the first-order diffraction efficiency is designed to be 0, and the light source for CD is used. In this case, the first-order diffraction efficiency is set to 10% and the zero-order diffraction efficiency is set to 75%. Also, with the other diffraction grating characteristic, a differential push-pull method for detecting a tracking error detection signal during DVD-RAM recording can be realized.

In the above embodiment, the grating is formed on one surface of the diffraction grating 21. However, as shown in FIG. 2B, one surface and the other surface have different diffraction grating characteristics. Is also good. For example, on the surface 22A, as described in the first embodiment, when the light source for DVD is used, 1
The first-order diffraction efficiency is designed to be 0, and when a light source for CD is used, the first-order diffraction efficiency is 10% and the 0th-order diffraction efficiency is 75%. On the other surface 22B, a differential push-pull method for detecting a tracking error detection signal during DVD-RAM recording can be realized.

Since the relationship between the phase grating depth φ0 and the diffraction efficiency η changes periodically every phase 2π, the grating groove depth h
0 is h0 = λ1 / (n−1), h1 = λ2 /
By setting it to m times (n-1) (m is a natural number), the diffraction efficiency of the side beam can be set to a desired value.

The semiconductor laser device may be a device using a plurality of different semiconductor lasers which are separated and arranged in the vicinity instead of the multi-wavelength type semiconductor laser array.

Next, the pit structure of the disk read by the optical head device of the present invention will be described.

FIG. 5A shows the structure of the recording surface of the CD.
FIG. 5B shows the structure of the recording surface of the DVD-ROM.
FIG. 5C shows the structure of the recording surface of the DVD-RAM.
As described above, as optical discs, there are discs having a large track pitch and shortest pit length.
There is a need for a light source for obtaining light beams having different wavelengths as described above.

FIG. 6 shows an example of an electric signal system for processing a signal read by the optical head device.
The photodetector 16 is provided with the photodiodes 6A, 6B, 6C, 6D, 6E, and 6F as described with reference to FIG. Each photodiode 6A, 6B, 6C, 6D, 6
The outputs of E and 6F are supplied to buffer amplifiers 23a and 23a, respectively.
3b, 23c, 23d, 23e, and 23f. Buffer amplifiers 23a, 23b, 23c, 23d,
The A to F signals output from 23e and 23f are calculated as follows.

The adder 231 generates the (A + B) signal,
The adder 232 generates a (C + D) signal. The adder 233 uses the (A + C) signal from the adder 231 and the (C + D) signal from the adder 232 to generate (A + B) −
(C + D). This (A + B)-(C +
D) signal is used as a focus error signal.

The adder 234 generates a (A + C) signal, and the adder 235 generates a (B + D) signal. The (A + C) signal and the (B + D) signal are input to the phase difference detector 31. The output of the phase difference detector 31 is DVD
Used as a tracking error signal. on the other hand,
The (EF) signal obtained based on the detection signal of the sub beam is ignored because the switch 322 is turned off.

The (A + C) signal and the (B + D) signal are also input to the adder 236. The adder 235 calculates (A + B
+ C + D) signal (referred to as HF signal).

The E signal and the F signal are input to the adder 237. The (EF) signal is obtained from the adder 237. The (EF) signal is used as a tracking error signal for CD. That is, when the apparatus is in the CD playback mode, the switch 322 is turned on.

The present invention is not limited to the above embodiment.

According to the present invention, the first disk (for example, DV
An object of the present invention is to provide an optical head device having an optical layout with good reproduction performance for both D) and a second disk (for example, a CD). For this purpose, a non-polarized blaze hologram is used as an element for guiding the reflected light to the photodetector. According to this configuration, a light use efficiency of about 1.5 times that of a non-polarized rectangular hologram can be obtained, so that the DVD reproduction performance can be improved. In addition, by using a non-polarized hologram, a stable reproduction signal can be obtained without a change in the amount of received light due to birefringence of a CD.

In the conventional optical head device, a (1/4) λ plate is provided between the hologram and the objective lens. At this portion, the light transmission system is changed from linearly polarized light (P-polarized light) to circularly polarized light. For reflected light, change from circularly polarized light to linearly polarized light (S-polarized light)
I have to. This is because the S-polarized light reflected from the optical disk is polarized in the hologram into first-order diffracted light and guided to a photodetector. This hologram has a function that the efficiency of the 0th-order diffracted light is large for P-polarized light and the efficiency of the first-order diffracted light is large for S-polarized light.

It is preferable to use a hologram having high light use efficiency as the above hologram. However, such a polarization element system ((1/4) λ plate and polarization hologram)
Is used, the amount of light received by the photodetector varies due to the birefringence of the disk. For this reason, when the amount of birefringence of the disk is larger than the specification, there arises a problem that a reproduced signal largely changes. In the case of DVDs, because the standards are strict, those with a birefringence larger than the specification are not on the market, but those with the birefringence larger than the specification are on the CD. In addition, in the pickup device using the above-mentioned polarizing element system, the amount of received light fluctuates, which greatly affects the reproduction performance. Thus, when an optical pickup using a multi-wavelength type semiconductor array is specified,
Since a hologram is shared by a DVD and a CD, the use of a polarization hologram causes a problem that a reproduction signal greatly varies due to birefringence of the CD.

Therefore, in the present invention, a non-polarization hologram 13 as shown in FIG. 7 (B) or FIG. 7 (C) is used in the configuration as shown in FIG. 7 (A).

That is, in the present invention, a hologram having a blazed grating is used. The lattice shape of the hologram may be an asymmetrical shape as shown in FIG. 7B or an asymmetrical step shape as shown in FIG. 7C.

The semiconductor laser device 11 outputs a DVD beam having a wavelength of 650 mm from the first light source 1a and outputs a CD beam having a wavelength of 780 mm from the second light source 1b. The hologram 13 is a blaze hologram. The 0th-order and + 1st-order diffraction efficiencies are substantially the same with respect to the incident light, and the -1st-order diffraction efficiency has a smaller amount than that. This hologram 13 is a non-polarization hologram, and the polarization direction of incident light (P or S polarization)
Thus, the diffraction efficiency does not change.

At the time of reproducing a DVD, the light emitted from the first light source 1a enters the hologram 13. The zero-order light emitted by the hologram 13 is converted by the collimator lens 14 into collimated light, enters the objective lens 15, and is focused and irradiated on the recording surface of the optical recording medium. The reflected light reflected from the optical recording medium enters the hologram 13 via the objective lens 15 and the collimator lens 14. The + 1st-order light emitted from the hologram 13 is guided to the photodetector 16 and converted into an electronic signal by a photoelectric conversion element.

When reproducing a CD, the second light source 1b is used. The light emitted from the light source 1b is guided to the photodetector 16 through a path similar to that described above, and the reflected light from the optical disk is converted into an electronic signal by a photoelectric conversion element.

With the above configuration, since the light use efficiency is improved, the reproduction performance of the DVD can be improved. Also, by using a non-polarized hologram, C
A stable reproduced signal can be obtained without a large change in the amount of received light due to the sub refraction of D. In the case of an optical system using a conventional polarizing element system ((1/4) λ plate and polarization hologram), the amount of received light fluctuates due to the birefringence of the CD.
As shown in (D), there is a problem that the reproduction signal fluctuates greatly. However, the optical head device of the present invention eliminates such a problem.

The present invention is not limited to the above embodiment.

The present invention provides an optical head device using a semiconductor laser array, in which the difference between the best tilt angles of DVD and CD is small and the reproduction signal performance is good. Therefore, the second CD of the CD is located near the optical axis of the objective lens.
The optical axis of the light source is aligned. This allows
Oblique incidence occurs on the objective lens for DVDs, but does not occur for CDs. In the DVD and CD compatible objective lenses, the aberration caused by oblique incidence of DVD is astigmatism, so that the best tilt angle and the performance deterioration of the reproduction signal are small, and the difference between the best tilt angle of DVD and CD is small.
In addition, the reproduction signal reproduction performance can be improved.

FIG. 8 shows an embodiment thereof.

As shown in FIG. 8A, the relationship is such that the optical axis of the second light source 1b for CD almost coincides with the optical axis of the objective lens 15.

At the time of reproducing a DVD, the diffused light emitted from the first light source 1a enters the hologram 13. The light emitted by the hologram 13 is converted into collimated light by a collimator lens 14, enters an objective lens 15, and is focused and irradiated on a recording surface of an optical recording medium. The reflected light reflected from the optical recording medium enters the hologram 13 via the objective lens 15 and the collimator lens 14. The + 1st-order light diffracted and emitted from the hologram 13 is guided to the photodetector 16 and converted into an electronic signal by the photoelectric conversion element.

At the time of reproducing a CD, the second light source 1b is used. The light emitted from the light source 1b is guided to the photodetector 16 through a path similar to that described above, and the reflected light from the optical disk is converted into an electronic signal by a photoelectric conversion element.

The objective lens 15 can be driven in a focusing method or a tracking direction by a servo device so that the objective lens driving device (not shown) can follow the surface runout and eccentricity of the disk.

FIG. 8B shows the relationship between the oblique incidence of the objective lens 15 and the best tilt angle, and FIG. 8C shows the relationship between the oblique incidence of the objective lens 15 and the jitter. DVD
An objective lens having / CD compatibility is designed with DVD priority. When reproducing a DVD, astigmatism is generated with respect to oblique incidence. On the other hand, when this lens is used at the time of reproducing a CD, coma aberration occurs because the sine condition is broken by oblique incidence. For this reason, the oblique incidence deteriorates the best tilt angle and jitter characteristics during CD reproduction,
In D, the degree of deterioration is small.

With the above arrangement, when the light source 1b for CD is used, oblique incidence does not occur on the objective lens 15, so that the best tilt angle and the jitter characteristics are not deteriorated. When the light source 1a for DVD is used, oblique incidence on the objective lens 15 occurs. However, since the aberration generated by the oblique incidence is astigmatism, the deterioration of the best tilt angle and the deterioration of the jitter characteristic are acceptable. Becomes

As described above, the device of the present invention has
It has a second light source and has an objective lens 15. Here, the first light source and the second light source are arranged in an asymmetric relationship with respect to the optical axis of the objective lens.

The substrate thickness of the first optical disk is t1, the substrate thickness of the second optical disk is t2, the distance between the axis of the first light source and the optical axis of the objective lens is δ1, the axis of the second light source and the objective. When the distance from the optical axis of the lens is δ2, t1 <t2,
It is preferable that δ1> δ. The optical axis of the second light source is substantially aligned with the optical axis of the objective lens. The first and second light sources constitute a multi-wavelength semiconductor laser device.

The present invention is not limited to the above embodiment.

According to the present invention, it is possible to obtain a focus error signal of higher quality for both DVD and CD. For this purpose, the center of the hologram is arranged in the middle of the optical axes of the first and second light sources. As a result, the amplitude of the focus error signal during CD reproduction is
The amplitude of the focus error signal at the time of reproduction also becomes an appropriate amplitude, and the quality of the focus error signal of the entire apparatus can be improved.

FIG. 9 and FIG. 10 are diagrams for explaining the embodiment.

As shown in FIG. 9A, the hologram 13
Is located on the optical axis of the second light source 1b and coincides with the optical axis of the objective lens 15, the area of the hologram 13 through which the light beam passes is as follows. That is, FIG. 9B shows the case where the second light source 1b (for CD) is used, and the hologram pattern 3a and the reproduction beam 9a are concentric. On the other hand, FIG. 9 (C)
This is the time when the first light source 1a (for DVD) is used, and the hologram pattern 3a and the reproduction beam 9b are largely displaced in the arrangement direction of the light sources.

In such a state, the signal amplitude of the focus error signal is greatly reduced. Therefore, in the present invention, as shown in FIG. 10A, the optical axis 151 of the objective lens 15 is aligned with a position substantially close to the optical axis of the second light source 1b. The function (origin of function) axis 131 is arranged so as to be substantially at an intermediate position between the optical axis of the first light source 1a and the optical axis of the second light source 1b.

FIG. 10B shows an example of a beam pattern on the light receiving element of the photodetector 16. This beam pattern is for a CD, for example, and the main beam is branched into two, and each sub beam is also branched into two. The principle of operation is the same as that described above.

FIG. 11A shows a side view of the optical head device having the hologram 13 arranged as shown in FIG. In such an arrangement, FIG.
As shown in FIGS. 11B and 11C, the use areas of the light beam 8a of the first light source 1a and the light beam 8b of the second light source 1b are shifted from the center of the hologram pattern 3a in opposite directions. Position.

However, even in such a state, FIG.
As can be seen from the relationship characteristic between the focus error amplitude and the light beam position on the hologram pattern shown in (D), the arrangement of FIG. 11A can obtain a larger focus error amplitude. That is, a large amplitude can be obtained as the amplitude of the focus error signal both at the time of DVD reproduction and at the time of CD reproduction. With the hologram arrangement position as shown in FIG. 9, as can be seen from FIG. 11D, only a small-amplitude focus error signal can be obtained when reproducing a DVD.

With the above configuration, an appropriate focus error signal amplitude can be obtained for both DVD and CD, and the reliability of the pickup device can be improved.

On the other hand, the tracking error signal of DVD is
The light beam divided into four by the hologram pattern 3a is received by 6a to 6d (FIG. 10B) of the photodetector 16,
It is obtained by detecting the phase difference between the respective light receiving amounts. Therefore, the light beam 8a of the DVD has the hologram pattern 3
It is desired to be close to the center of a. On the other hand, the tracking error signal of the CD does not depend on the relative position between the hologram pattern 3a and the light beam 8b because the three-beam method is used. Therefore, when a tracking error signal is considered, a CD has more margin for positional deviation than a DVD.

From such considerations, it is possible to arrange the center of the hologram 13 closer to the first light source 1a than the intermediate position between the first light source 1a and the second light source 1b with respect to the optical axis of the optical system. , The amplitude of the tracking error signal can be obtained satisfactorily.

The above focus error signal is obtained by the mixed aberration method (US Pat. No. 5,161,139) provided on the hologram 13.
) Is detected by the lens action.

According to the above-described apparatus of the present invention, the first optical disc that emits the light beam of the first wavelength to be irradiated on the first optical disc is
Light source and a second optical disc having different specifications from the first optical disc.
And irradiating the optical disk with a light beam having a second wavelength different from the first wavelength and arranged in a direction substantially parallel to the light beam having the first wavelength. A second light source. At least one beam for radiating the light beams emitted from the first and second light sources to the recording / reproducing surface of the optical disk in a focused manner and passing reflected light from the recording / reproducing surface in a direction opposite to the traveling direction of the beam. With two objective lenses. The hologram includes at least a hologram for detecting a focus shift between the recording / reproducing surface and the light beam focused and irradiated by the objective lens.

The position where the center of the hologram is projected in the direction of the optical axis of the objective lens on the plane including the first light source and the second light source is located between the first and second light sources. Is to be placed.

When the distance between the projection position and the first light source is δ1 and the distance between the projection position and the second light source is δ2, δ1 = δ2. Further, the hologram detects a focus shift by a mixed aberration method.

The apparatus of the present invention irradiates a first optical disk with a first light source that emits a light beam of a first wavelength and irradiates a second optical disk having a specification different from that of the first optical disk. A second light source disposed at substantially the same position as the first light source and emitting a light beam of a second wavelength different from the first wavelength in a direction substantially parallel to the light beam of the first wavelength; Having. And a diffraction grating for generating a side beam for detecting a tracking shift of the second optical disc. Further, it has the objective lens and the hologram.

Here, the distance between the projection position where the center of the hologram is projected in the direction of the optical axis of the objective lens and the distance between the first light source and the surface of the hologram in the plane including the first light source and the second light source. δ1, δ1 <δ2, where δ2 is the distance between the projection position and the second light source.

The present invention is not limited to the above-described embodiment, and still another embodiment will be described below.

In an optical pickup using a multi-wavelength semiconductor laser array, since the light source for DVD and the light source for CD are separated, the position where the light source is projected on the hologram in the optical axis direction and the center of the hologram There is a disagreement. For this reason, there is a problem that the quality of the focus error signal is deteriorated. In order to improve this, it is preferable to arrange the hologram as far as possible from the semiconductor laser array.

On the other hand, since the hologram is shared by the DVD and the CD, it is preferable that the level of the reproduced signal does not change due to the birefringence of the disc. Therefore, it is conceivable to use a non-polarized hologram. When a non-polarized hologram is used, in the light transmission system, the 0th-order light of this hologram is irradiated onto the disk via the objective lens, and in the reflection system, the + 1st-order light of this hologram is guided to the photodetector. However, the -1st-order light in the light transmission system reaches the photodetector as the 0th-order light in the reflection system, and generates stray light. This stray light causes deterioration in the quality of the reproduced signal. To reduce such stray light, place a hologram near the semiconductor laser array and increase the diffraction angle,
It is preferable that the negative light in the light transmission system is blocked by the aperture.

As described above, regarding the quality of the focus error signal, it is better that the distance between the semiconductor laser array and the hologram is long, and to obtain stray light, the distance between the semiconductor laser array and the hologram is short. There are conflicting demands for good.

Therefore, the present invention allows the optimum distance between the semiconductor laser array and the hologram to be set.

FIG. 12A is a structural view of the optical head device. During DVD reproduction, light emitted from the first light source 1a enters the hologram 13 and is converted into collimated light by the collimator lens 14. Collimator lens 14
The emitted collimated light is limited to an appropriate numerical aperture by the aperture, enters the objective lens 15, and is focused and irradiated on the recording surface of the recording medium. Light reflected from the recording medium enters the hologram 13 via the objective lens 15, the aperture, and the collimator lens 14. The hologram 13 emits + 1st-order diffracted light, which is guided to a photodetector 16. Here, an operation of converting light into an electric signal is performed.

On the other hand, at the time of reproducing a CD, the second light source 1b is used. The light emitted from the first light source 1b travels along the same path as before, and the reflected light from the recording medium is converted to light by the photodetector 16.
It is led to.

As described above, in this optical head device, one hologram 13 is shared when the first light source is used and when the second light source is used. Here, since the diffraction angle of the hologram 13 is almost proportional to the wavelength, a DV having a short wavelength is used.
The first light source 1a for D is arranged on the photodetector 16 side, and
From the photodetector 16 to the first light source 1a.
More distant position. With this configuration, one light detector 16 can receive light from the first and second light sources.

Since the diffraction angle is substantially proportional to the wavelength, the distance from the first light source 1a to the second light source 1b is
The distance from the first light source 1a to the photodetector 16 is also in a proportional relationship.

As shown in FIG. 12A, in the multi-wavelength type semiconductor laser array, the first light source and the second light source are separated by the optical axis because the first light source and the second light source are located at separate positions. The position projected on the hologram in the direction cannot coincide with the center of the hologram 13 at the same time. Therefore, FIG.
As shown in FIG. 2B, the beam is off the center of the hologram pattern of the hologram 13.

FIG. 12C shows the ratio of the distance between the semiconductor laser light source to the hologram 13 and the distance between the two light sources on the horizontal axis, and the vertical axis shows the amplitude of the focus error signal. When the distance from the semiconductor laser to the hologram 13 increases, the beam on the hologram 13 increases, so that the influence of the light source shift becomes relatively small and the amplitude of the focus error signal increases.

Assuming that the amplitude of the focus error signal when there is no light source displacement is 1, the allowable value of the amplitude decrease is 0.8, so that the distance from the semiconductor laser light source to the hologram 13 and the distance between the two light sources Is preferably 20 or more.

On the other hand, as shown in FIG. 12A, the −1st-order light of the hologram of the light transmission system is not limited in part by the aperture, and may enter the objective lens 15. This light is
The zero-order light of the hologram 13 of the light receiving system is incident on the light detector 16 and becomes stray light.

FIG. 12D shows the light amount ratio between the 0th-order light in the light transmission system and the -1st light in the light transmission system on the horizontal axis, and the vertical axis shows the reproduction signal jitter. The larger the light amount ratio, the more S / N
And the reproduction signal jitter is reduced.

In FIG. 12E, the ratio of the distance between the semiconductor laser light source to the hologram 13 and the distance between the light sources is plotted on the horizontal axis, and the vertical axis shows the −1st order light of the light transmission system. Of the light transmission system
Looking at the allowable range of the primary light, the ratio of the distance from the semiconductor laser light source to the hologram 13 to the distance between the two light sources is 4
It is desirably 0 or less.

From the above results, by setting the ratio of the distance from the semiconductor laser light source to the hologram 13 to the distance between the two light sources to be 20 or more and 40 or less, the quality of the focus error signal is good and the reproduction signal reproduction It can be understood that an optical head having good performance can be obtained.

The present invention also provides a manufacturing method for assembling the above optical head device with high accuracy.

Now, it is assumed that the optical head device is assembled with the arrangement relationship of each component as shown in FIG. Here, it should be noted that the semiconductor laser device 11 is a multi-wavelength semiconductor laser device. For example, a light source 1b for CD (outputs a beam with a wavelength of 780 nm), a DVD
Light source 1a (outputs a beam with a wavelength of 650 nm)
In close proximity. The hologram 13 is configured to be integrated with the semiconductor laser device 11 and the photodetector 16 with an accuracy of about 10 μm.

In order to facilitate such an assembly,
As shown in FIG. 13B, in the present invention, the hologram 13
Are provided with markers 3a and 3b. And marker 3
a is provided at a position where the second light source 1b is projected in the optical axis direction, and the marker 3b is provided at a position where the light detector 16 is projected in the optical axis direction.

When the position of the hologram 13 is adjusted during assembly, the laser device side is observed from the collimator 14 side by, for example, a microscope, and the markers 3a, 3
The marker position is adjusted so that b matches the predetermined optical axis.

In FIG. 13C, the second light source 1b is aligned with the marker 3a provided at the center of the hologram pattern of the hologram 13, and the optical axis guided to the photodetector 16 is aligned with the marker 3b. 4 shows an example of a state.

Normally, the beam of the first light source 1b of the semiconductor laser device 11 coincides with the line connecting the markers 3a and 3b, but in this example, the semiconductor laser device 11 is rotated slightly. This shows the arrangement.

FIGS. 13D and 13E show examples of beam spots formed on the four-division diode of the photodetector 16 when alignment is performed in such a state.
Is shown in

FIG. 13D shows the beam spot of the main beam for DVD. As shown in FIG. 13C, the projection spot on the hologram of the first light source 1a corresponds to the marker 3a. Due to the deviation from the line connecting 3b, the spot of the reflected light guided onto the photoelectric conversion element of the photodetector 16 is slightly shifted from a desired position on the photoelectric conversion element. That is, the spot becomes an asymmetric spot on the division line of the photoelectric conversion element. However, in the case of a DVD beam, since the aperture is large, the diameter of the beam spot is large. Thus, even if the beam is shifted from a desired position, the reproduction function of the reproduction signal hardly deteriorates. In other words, the influence of the deviation on the reproduction performance is relatively smaller than the influence of the deviation of the CD beam spot described below on the reproduction performance.

On the other hand, FIG. 13E shows a beam spot of a main beam for CD. FIG.
As shown in (C), with respect to the second light source 1b, the projection spot on the hologram was adjusted to match the marker 3a, so that the spot of the reflected light guided to the photodetector 16 was photoelectrically converted. It matches the desired position on the device.

The present invention is not limited to the above embodiment, but may be a method as shown in FIG. That is, the first and second light sources 1 of the semiconductor laser device 11
The first marker 3a is provided in the middle of the projected positions of the light beams a and 1b, and the marker 3b is provided in the position where the middle position of the four-division diode of the photodetector 16 is projected in the optical axis direction. The semiconductor laser device 11 and the photodetector 16 are mounted on a substrate (not shown). When the hologram 13 is mounted thereon, the semiconductor laser device 11 and the hologram 13 are observed from the optical axis direction, and the marker 3a on the hologram 13 matches the center of the light sources 1a and 1b.
The third hologram is fixed by adjusting the position of the second marker 3b so as to match the center of the main beam detecting portion of the photodetector 16 (the center of the quadrant diode). With this configuration, even when the semiconductor laser device 11 is mounted in a state where the semiconductor laser device 11 is slightly displaced from a desired position (a rotated example in FIG. 14A), the first light source 1a for DVD and the CD The second light source 1b is arranged to be shifted from the marker of the hologram 13. Thereby, the beam spot for DVD on the photodetector 16,
14B and FIG. 14B.
As shown in (C), each is formed in an asymmetric shape with respect to the dividing line. In this embodiment, either DVD playback or CD playback does not significantly reduce either of the playback performances.

In the above optical head device, the numerical aperture NA1 when the light beam from the first light source is
If the numerical aperture NA2 when a light beam from the light source is adopted, then NA1> NA2.

It is needless to say that the concept of the present invention may be applied by combining the technical concept described with reference to FIG. 1 and the technical concept described with reference to FIG. Furthermore, it goes without saying that the technical idea described with reference to FIG. 8 may be selectively or combined applied to such a technical idea.

The present invention includes a concept combining both the technical concept described with reference to FIG. 8 and the technical concept described with reference to FIG. Furthermore, the technical ideas described with reference to FIG. 7 may be further combined, and such ideas are also included in the scope of the present invention.

Further, for each of the above technical ideas,
Needless to say, the technical ideas described with reference to FIG. 12 may be combined.

[0127]

As described above, according to the present invention,
When the light source of the first wavelength is used, a side beam is generated, but when the light source of the second wavelength is used, the side beam is not generated, and the light use efficiency of the second light source is increased. be able to.

[Brief description of the drawings]

FIG. 1 is a configuration explanatory view of an optical head device according to an embodiment of the present invention.

FIG. 2 is an explanatory diagram of a configuration of the photodetector of FIG. 1 and an explanatory diagram of a beam spot when data is read by a three-beam method.

FIG. 3 is an explanatory view of characteristics of a phase grating depth and diffraction efficiency and a grating depth shown for explaining the principle of the present invention.

FIG. 4 is an explanatory view of a diffraction grating according to another embodiment of the present invention.

FIG. 5 is an explanatory diagram showing a recording surface of a CD, a DVD-ROM, and a DVD-RAM.

FIG. 6 is a diagram showing an example of an electrical signal processing path of the optical head device according to the present invention.

FIG. 7 shows still another embodiment of the present invention.
FIG. 3 is an explanatory diagram of an apparatus using a non-polarized hologram.

FIG. 8 is a view showing still another embodiment of the present invention, and is an explanatory view of a device in which the optical axis of an objective lens is arranged asymmetrically with respect to the optical axes of first and second light sources.

FIG. 9 is an explanatory diagram of a beam spot projected on a hologram.

FIG. 10 is still another embodiment of the present invention, and is an explanatory view of an apparatus in which a center position of a hologram is shifted from an optical axis of an objective lens.

11 is an explanatory diagram of a beam spot projected on a hologram in the apparatus of FIG.

FIG. 12 shows still another embodiment of the device of the present invention, in which the relationship between the distance between the semiconductor laser device and the hologram and the distance between the first and second light sources of the semiconductor laser device is devised. FIG.

FIG. 13 is a view for explaining a method of assembling the apparatus according to the present invention.

FIG. 14 is a view for explaining still another assembling method.

[Explanation of symbols]

11: semiconductor laser device, 12: diffraction grating, 13: hologram, 14: collimator lens, 15: objective lens.

Claims (30)

[Claims] A first light source that emits a light beam having a first wavelength; and a first light source that is disposed at substantially the same position as the first light source.
A second light source that emits a light beam having a second wavelength different from that of the first light source. The first-order diffraction efficiency of the light beam incident from the first light source becomes substantially zero, An optical head device, comprising: a diffraction grating that emits as a first-order diffracted light beam with respect to a light beam incident from the light source (1), on an optical path between the first and second light sources and the objective lens. 2. When the refractive index of the diffraction grating is n and the wavelength of the first light source is λ1, the depth h0 of the grating groove of the diffraction grating is h0 = m · λ1 / (n−1). 2. The optical head device according to claim 1, wherein (m is a natural number). 3. The optical head device according to claim 2, wherein m is 1. 4. The optical head device according to claim 1, wherein the first-order diffracted light of the second light source is used for detecting a tracking error signal. 5. The optical head device according to claim 1, wherein the first light source and the second light source are multi-wavelength semiconductor laser arrays. 6. A first light source for emitting a light beam having a first wavelength, and a light beam having a second wavelength different from the first wavelength, the light source being arranged at substantially the same position as the first light source. The first-order diffraction efficiency becomes substantially zero for the light source from the second light source and the light beam from the first light source, and the first-order diffraction light for emitting the first-order diffraction light for the light beam from the second light source. The first diffraction grating emits first-order diffracted light with respect to the light beam from the first light source, and the second diffraction grating with which the first-order diffraction efficiency becomes substantially zero with respect to the light beam from the second light source. An optical head device comprising: a diffraction grating. 7. The refractive index of the first diffraction grating is n1, the refractive index of the second diffraction grating is n2, the wavelength of the first light source is λ1, and the wavelength of the second light source is λ2. In this case, the depth h01 of the grating groove of the first diffraction grating is: h01 = m1 · λ1 / (n1-1) The depth h02 of the grating groove of the second diffraction grating is: h01 = m1 · λ2 / ( 7. The optical head device according to claim 6, wherein (n2-1) (m1 and m2 are natural numbers). 8. The optical head device according to claim 7, wherein at least one of m1 and m2 is 1. 9. The optical head device according to claim 6, wherein the first diffraction grating and the second diffraction grating are formed on an integrated substrate. 10. A first light source for emitting a light beam having a first wavelength.
A light source, a second light source that is disposed at substantially the same position as the first light source and emits a light beam of a second wavelength different from the first wavelength, and irradiates the recording medium with a light beam; An optical head device having a hologram for guiding the reflected light to a photodetector, wherein the hologram is a non-polarization hologram. 11. The optical head device according to claim 10, wherein the non-polarization hologram has an asymmetric lattice shape. 12. The optical head device according to claim 10, wherein the non-polarized hologram has a blaze grating shape. 13. The optical head device according to claim 10, wherein the non-polarization hologram has a step-like asymmetric lattice shape. 14. A first light source that emits a light beam having a first wavelength, and a light beam having a second wavelength different from the first wavelength, which is disposed at substantially the same position as the first light source. An optical head device comprising: a second light source that emits light; and an objective lens that focuses a light beam from the first light source and the second light source on a recording medium, wherein the optical axis of the objective lens is An optical head device, wherein the optical head device is positioned asymmetrically with respect to the optical axes of the first and second light sources. 15. The recording medium includes a first disk that is symmetric when the first light source is used, and a second disk that is symmetric when read using the second light source, The substrate thicknesses of the first and second disks are t1 and t, respectively.
2, the distance between the optical axis of the first light source and the optical axis of the objective lens is δ1, and the distance between the optical axis of the second light source and the optical axis of the objective lens is δ2, t1 14. The optical head device according to claim 13, wherein the relationship is <t2, δ1> δ2. 16. The optical system according to claim 14, wherein the optical axis of the second light source substantially coincides with the optical axis of the objective lens.
An optical head device according to claim 1. 17. The optical head device according to claim 14, wherein said first and second light sources are constituted by a multi-wavelength type semiconductor laser array. 18. A first light source for emitting a light beam of a first wavelength.
And the light source is disposed at substantially the same position as the first light source,
A second light source that emits a light beam having a second wavelength different from the first wavelength, an objective lens that focuses and irradiates the first or second light source and laser light onto the optical disc, and an objective lens that is reflected from the optical disc. An optical head device having a hologram that diffracts reflected light returned via the objective lens and guides the reflected light to a light receiving element, wherein the projection on the hologram is performed at an intermediate position between the optical axes of the first and second light sources. An optical head device, wherein the hologram is arranged so as to be centered. 19. The distance between the center of the hologram and the optical axis of the first light source is δ1, and the center of the hologram and the optical axis of the second light source are within the projection plane of the objective lens in the optical axis direction. 19. The optical head device according to claim 18, wherein when a distance from the optical head is δ2, approximately δ1 = δ2. 20. The distance between the center of the hologram and the optical axis of the first light source in the projection plane of the objective lens in the optical axis direction is δ1, the center of the hologram and the optical axis of the second light source. 19. The optical head device according to claim 18, wherein, when the distance from the optical head is δ2, approximately δ1 <δ2. 21. The optical head device according to claim 18, wherein the hologram is for detecting a focus shift by a mixed aberration method. 22. A first light source for emitting a light beam of a first wavelength.
And the light source is disposed at substantially the same position as the first light source,
A second light source that emits a light beam having a second wavelength different from the first wavelength, an objective lens that focuses and irradiates the first or second light source and laser light onto the optical disc, and an objective lens that is reflected from the optical disc. An optical head device having a hologram for diffracting reflected light returned via the objective lens and guiding the reflected light to a light receiving element, wherein the distance between the first and second light sources is δ, An optical head device wherein a distance between a second light source and the hologram is between 20δ and 40δ. 23. The optical head device according to claim 22, wherein the hologram is a non-polarization hologram. 24. A first light source for emitting a light beam having a first wavelength.
And the light source is disposed at substantially the same position as the first light source,
A second light source that emits a light beam having a second wavelength different from the first wavelength, an objective lens that focuses and irradiates the first or second light source and laser light onto the optical disc, and an objective lens that is reflected from the optical disc. An optical head device having a hologram for diffracting the reflected light returned through the objective lens and guiding the diffracted light to a light receiving element, An optical head device, wherein a first marker is attached to a projection position in an optical axis direction. 25. A first light source for emitting a light beam of a first wavelength.
And the light source is disposed at substantially the same position as the first light source,
A second light source that emits a light beam having a second wavelength different from the first wavelength, an objective lens that focuses and irradiates the first or second light source and laser light onto the optical disc, and an objective lens that is reflected from the optical disc. An optical head device having a hologram for diffracting the reflected light returned via the objective lens and guiding the diffracted light to a light receiving element, wherein the hologram is provided with a mark of the first light source as a mark when the mounting operation is performed. The projection position in the optical axis direction and the second
An optical head device, wherein a first marker is provided at an intermediate position between the light source and the projection position in the optical axis direction. 26. When the numerical aperture NA when the light beam from the first light source is adopted and the numerical aperture NA2 when the light beam from the second light source are adopted, NA1> N.
The optical head device according to claim 23, wherein the optical head device is A2. 27. The hologram is provided with a second marker at a position corresponding to an optical axis directed to an arbitrary point on the light receiving element.
The optical head device according to any one of the above. 28. The optical head device according to claim 27, wherein the arbitrary point is a center of the light receiving element. 29. The optical head device according to claim 27, wherein the arbitrary point is a marker provided on the light receiving element. 30. A first light source for emitting a light beam of a first wavelength, and a light beam of a second wavelength different from the first wavelength, the light source being arranged at substantially the same position as the first light source. No. to emit
2 light sources, and the first and second light sources and the objective lens are disposed on the optical path. The 0th-order diffracted light is almost 100% and 1% with respect to the light beam incident from the first light source. The diffraction order becomes almost zero, and for the light beam incident from the second light source, a diffraction grating that emits zero-order and first-order diffraction light, and on a light path between the objective lens and the diffraction grating. A hologram that is arranged and irradiates an optical disc through the objective lens and reflects reflected light from the optical disc through the objective lens to a light receiving element for signal reproduction; and a photoelectric conversion from the light receiving element. A circuit for processing the output, performing tracking error processing on the photoelectric conversion output of the reflected light corresponding to the first-order diffracted light, and performing the tracking error processing on the photoelectric conversion output of the reflected light corresponding to the zero-order diffracted light. Signal A disk recording / reproducing apparatus comprising a signal processing circuit for obtaining a tracking error signal by raw output and / or phase detection.