JP2002074730A - Optical pickup device and optical disk device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical pickup device that facilitates thin shape and low cost by tilt-sensing using light even if the device is structured for the use of a single light source and thereby dispensing with an externally attached tilt sensor. SOLUTION: A part of an optical flux from a light source 4 is diffracted by a diffraction element 10 and made incident on an objective lens 7 through a collimator lens 5; as a result, a part of the light-source light unused before can be utilized for tilt-detection, tilt is detected without lowering light utilizing efficiency, and by eliminating an externally attached tilt sensor, the number of parts is reduced and the optical pick up is made thin. In addition, as tilt detection light 13 is emitted to a position very close to the actual information detection light 12 through the objective lens 7, tilt detection is performed with high accuracy, and as the tilt detection light 13 is emitted nearly in a state of parallel beams, the beam diameter is large. Hence, stable tilt detection against noise, and the like is possible without being affected by the presence/ absence of pits, scratches or the like on the surface of an optical recording medium.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an optical pickup device and an optical disk device.

[0002]

2. Description of the Related Art Generally, in this type of optical disk device,
Using an optical pickup device, the light beam emitted from the light source is condensed and irradiated on the recording surface of the optical recording medium via the objective lens, and the reflected light beam reflected from the recording surface of the optical recording medium is again passed through the objective lens. Recording (or erasing) or reproducing information on the optical recording medium by guiding the light to the light receiving element.

In recent years, with the progress of high-density recording such as DVDs, the use of a lens having a large numerical aperture NA as an objective lens tends to reduce the diameter of a focused beam. is there. In this case, if the optical recording medium is tilted (inclination of the medium surface with respect to the optical axis of the objective lens), aberration occurs, and required recording / reproducing characteristics cannot be obtained. This has a greater influence as the numerical aperture NA of the objective lens increases as described above.

Therefore, generally, the tilt of the optical recording medium is detected, and the amount of tilt is corrected based on the detection result.

Although various proposals have been made for such a tilt detection method, it is basically to externally attach a tilt sensor. One of them is disclosed in, for example, JP-A-10-320.
As shown in Japanese Patent Publication No. 804, a tilt sensor is mounted near an objective lens so that a tilt amount can be detected as close as possible to a portion where information is actually read, and also a tangential tilt can be measured in addition to a radial tilt. There is something like that.

[0006]

In order to mount an optical disk drive in a notebook computer or the like, it is necessary to reduce the thickness of the drive. In this regard, the conventional external tilt sensor as described above has disadvantages such as an increase in the height direction and a decrease in the driving speed of the actuator due to attachment to the actuator.

[0007] In view of the above, there has been proposed a method of detecting tilt using a light source incorporated in an optical pickup device, for example, a semiconductor laser. To give an overview, the current DVD drive apparatus is focused on the point that two semiconductor lasers having different wavelengths are mounted as light sources so that a CD-based medium can be read. For example, a semiconductor that emits light of 650 nm wavelength is used. D with laser
It records or reproduces VD media, and records or reproduces CD media with a semiconductor laser that emits 780 nm wavelength light, but emits 780 nm wavelength light when recording or reproducing high-density DVD media that poses a tilt problem. Since the semiconductor laser is not used, this semiconductor laser emits light and is used as tilt detection light.

As described above, by performing sensing using the light of the semiconductor laser used as the light source of the optical pickup device, an external tilt sensor can be omitted, and the thickness and cost can be reduced.

However, the above proposed example is based on an optical pickup device having a plurality of (two) semiconductor lasers. In the case of a single light source (semiconductor laser), an external tilt sensor must still be used. Not something.

Therefore, according to the present invention, even if a single light source is used, an external tilt sensor can be omitted by performing tilt sensing using the light.
It is an object of the present invention to provide an optical pickup device which can be made thinner and lower in cost, and an optical disk device using the same.

Further, in order to achieve the above object, the present invention provides an optical pickup device which can reduce the amount of light in a recordable optical pickup device, which tends to generate noise in a signal, and an optical pickup device capable of improving the noise. It is an object of the present invention to provide an optical disc device using the same.

[0012]

According to the first aspect of the present invention,
The light beam emitted from the light source is condensed and irradiated on the recording surface of the optical recording medium via the collimating lens and the objective lens, and the reflected light beam reflected from the recording surface of the optical recording medium is received again via the objective lens. In an optical pickup device for recording or reproducing information on or from the optical recording medium by guiding the light to an element, a part of a light beam emitted from the light source is diffracted, and the objective lens passes through the collimating lens to form substantially parallel light. A diffractive element for irradiating the optical recording medium, and a tilt detecting device for receiving the reflected light from the optical recording medium diffracted and irradiated by the diffractive element again through the objective lens and detecting the tilt of the optical recording medium. A light receiving element.

Therefore, a part of the light beam, which has not been used in the past, is used for tilt detection by diffracting a part of the light beam from the light source with the diffraction element and making the light beam enter the objective lens through the collimating lens. Thus, the tilt can be detected without lowering the light use efficiency. In addition, since an external tilt sensor is not required, the number of components can be reduced and the device can be reduced in thickness. In addition, since the adjustment is not required, the cost can be reduced. Further, since the tilt detection light is applied to a position very close to the actual information detection light via the objective lens, the tilt detection can be performed with very high accuracy.
Furthermore, since the tilt detection light is radiated in a substantially parallel light state, the beam diameter is large, and it is not sensitive to pits or scratches on the optical recording medium surface, and the tilt detection is stable against noise and the like. Becomes possible.

According to a second aspect of the present invention, in the optical pickup device of the first aspect, the diffractive element has a cross-sectional shape such that light incident from the light source side is diffracted into a lens effective diameter of the collimating lens. It is characterized by being formed asymmetrically in the left and right direction as viewed in the traveling direction of light.

Therefore, more light can be guided to the optical recording medium surface by suppressing the generation of unnecessary diffracted light, and flare light is not generated, and the signal light becomes larger, so that stable tilt detection can be performed. .

According to a third aspect of the present invention, in the optical pickup device according to the second aspect, the diffractive element has a cross-sectional shape which is formed asymmetrically in the right and left direction as viewed in the light traveling direction by blazing. I do.

Therefore, in realizing the optical pickup device according to the second aspect, by using a blazed diffractive element having a large diffraction efficiency, it is possible to secure an amount of light used for tilt sensing and to obtain a highly reliable good tilt signal. Can be obtained.

The invention described in claim 4 is the first to third aspects of the present invention.
In the optical pickup device according to any one of the above, a plurality of the diffraction elements are provided at different positions around the optical axis of the objective lens.

Therefore, since a plurality of diffraction elements are provided and tilt detection is performed using the diffracted light, a large amount of light can be applied to the optical recording medium surface, and stable tilt signal detection can be performed. In addition, a tangential tilt can be detected in addition to the radial tilt.

The invention according to claim 5 is the invention according to claims 1 to 4.
In the optical pickup device according to any one of the above, the diffraction element is a polarization diffraction element whose diffraction efficiency depends on the polarization direction of incident light.

Therefore, by using a polarization diffraction element as the diffraction element, unnecessary flare light returned from the optical recording medium can be reduced, and a good tilt signal with high reliability can be obtained.

According to a sixth aspect of the present invention, in the optical pickup device of the fifth aspect, the polarization diffraction element is formed of an organic film.

Therefore, in realizing the optical pickup device according to the fifth aspect, by using an organic film having excellent fine processing properties as a material of the polarization diffraction element, it is possible to cope with processing with a small pitch, and to achieve accuracy and efficiency. Since a good polarization diffraction element can be manufactured, highly reliable signals can be obtained by irradiating light with smaller aberration.

The invention according to claim 7 is the invention according to claims 1 to 6
The diffraction area of the diffraction element in the optical pickup device according to any one of the above, is characterized in that the diffraction area is long in a track groove direction in the optical recording medium.

Therefore, by making the spot for detecting the tilt into a spot shape having a short axis in the direction of movement due to the tilt, the sensitivity is improved, and the tilt signal can be detected stably with respect to noise. .

According to the present invention, the light beam emitted from the light source is condensed and irradiated on the recording surface of the optical recording medium via the collimator lens and the objective lens, and is reflected from the recording surface of the optical recording medium. In an optical pickup device that records or reproduces information on the optical recording medium by guiding the reflected light flux to the light receiving element again via the objective lens, a plurality of optical pickup devices are provided at different positions around the optical axis of the objective lens. A plurality of light beams emitted from the light source and passed through the collimating lens are irradiated on the optical recording medium so as to diffract a part of the light flux and form an image at an out-of-focus position on a recording surface of the optical recording medium by the objective lens. Diffractive elements and reflected light from the optical recording medium diffracted and irradiated by these diffractive elements are again received via the objective lens, respectively, and then received by the intensity difference. Comprising a tilt detecting light-receiving element for detecting the tilt of the optical recording medium.

Accordingly, by irradiating the optical recording medium with a plurality of diffracted lights in a defocused state in order to detect a tilt, if there is a tilt, the sizes of those spots are different. Since the tilt amount can be determined, the alignment of the tilt detection light-receiving element can be facilitated, assembling adjustment can be facilitated, and the tilt can be detected stably even with aging or displacement. it can.

According to a ninth aspect of the present invention, in the optical pickup device of the eighth aspect, each of the diffraction elements has a cross-sectional shape such that light incident from the light source side is diffracted into a lens effective diameter of the objective lens. It is characterized in that it is formed left and right asymmetrically as viewed in the light traveling direction.

Therefore, more light can be guided to the optical recording medium surface by suppressing the generation of unnecessary diffracted light, and flare light is not generated, and the signal light becomes larger, so that stable tilt detection can be performed. .

According to a tenth aspect of the present invention, in the optical pickup device of the ninth aspect, each of the diffractive elements has a cross-sectional shape which is formed asymmetrically in the right and left directions as viewed in the light traveling direction by blazing. And

Therefore, in realizing the optical pickup device according to the ninth aspect, by using a blazed type diffraction element having a large diffraction efficiency, it is possible to secure an amount of light used for tilt sensing, and to obtain a highly reliable good tilt signal. Can be obtained.

According to an eleventh aspect of the present invention, in the optical pickup device according to any one of the eighth to tenth aspects, each of the diffraction elements is a polarization diffraction element whose diffraction efficiency depends on the polarization direction of incident light. It is characterized by the following.

Therefore, by using a polarization diffraction element as the diffraction element, unnecessary flare light returned from the optical recording medium can be reduced, and a good tilt signal with high reliability can be obtained.

According to a twelfth aspect of the present invention, in the optical pickup device of the eleventh aspect, the polarization diffraction element is formed of an organic film.

Therefore, in realizing the optical pickup device according to the eleventh aspect, by using an organic film having excellent fine processing properties as a material of the polarization diffraction element, it is possible to cope with processing with a small pitch, and to achieve accuracy and efficiency. Since a good polarization diffraction element can be manufactured, highly reliable signals can be obtained by irradiating light with smaller aberration.

In the optical disk apparatus according to the present invention, a drive source for rotating and driving the optical recording medium and a seek source movable in a radial direction with respect to the optical recording medium are provided. And an optical pickup device.

Therefore, since the optical pickup device according to any one of the first to twelfth aspects of the invention is provided with a small and thin optical pickup device which does not require an external tilt sensor, the optical disk device itself can be reduced in thickness and size. An optical disk device suitable for mounting on a notebook personal computer or the like can be provided.

[0038]

FIG. 1 shows a first embodiment of the present invention.
A description will be given based on FIG. FIG. 1 shows a schematic configuration example of an optical disk device to which the present embodiment is applied. The optical disk device may be a read-only information reproducing device or a recordable information recording / reproducing device. This optical disk device generally includes a spindle motor 2 as a drive source for rotationally driving an optical recording medium 1 such as a DVD, and a reproducing or recording surface for recording on an optical recording medium 1 that is rotationally driven. An optical pickup device 3 for irradiating light is provided.

The optical pickup device 3 basically includes a semiconductor laser 4 as a light source for emitting light toward the optical recording medium 1, a collimating lens 5 for converting the divergent light into parallel light, and an incident light. A beam splitter 6 for separating reflected light from the optical recording medium 1 side, an objective lens 7 for converging and irradiating a parallel light beam onto a recording surface of the optical recording medium 1, and an optical recording medium 1
A detection lens 8 for condensing the reflected light reflected from the object and passing again through the objective lens 7 and deflected and separated by the beam splitter 6, and a light receiving element 9 for receiving the reflected light condensed by the detection lens 8. . The light receiving element 9 is constituted by, for example, a two-division light-receiving element or a four-division light-receiving element, and is configured to be able to detect a focus / tracking error signal together with an RF signal by signal processing obtained from each divided area.

In this embodiment, the diffraction element 10 is provided between the semiconductor laser 4 and the collimating lens 5 in such an optical pickup device 3.
This diffraction element 10 is a parallel flat plate 1 transparent to the wavelength of the light source.
1 of the divergent light emitted from the semiconductor laser 4 and not the information recording / reproducing light 12 originally used for recording or reproduction, and if there is no diffraction element 10, FIG. A light beam (tilt detection light) 13 which is directed outside the effective diameter φ of the collimator lens 5 and is not captured by the collimator lens 5 as shown by A therein is diffracted so as to be captured within the effective diameter φ of the collimator lens 5. is there. The collimator lens 5 functions to focus the tilt detection light 13 diffracted by the diffraction element 10 on the near side of the objective lens 7. As a result, the tilt detection light 13 is radiated by the objective lens 7 to the optical recording medium 1 in the state of a substantially parallel light beam in the vicinity of the original condensing spot of the information recording / reproducing light 12.

The tilt detection light 1 reflected by the optical recording medium 1
3 passes through the objective lens 7 again and is reflected by the beam splitter 6 to the detection lens 8 side. Here, a tilt detection light receiving element 14 that receives the tilt detection light 13 transmitted through the detection lens 8 is provided. The tilt detecting light receiving element 14 is a two-divided light receiving element divided into two in the radial direction of the medium (tracking direction), and the detection signal from each area is arithmetically processed by the arithmetic unit 15 to detect the tilt. It is configured. Although separately shown in the drawing, the tilt detecting light receiving element 14 has a light receiving area formed in a predetermined shape at a position corresponding to each of the original light receiving element 9 and the same sensor substrate. The element is an integral element.

The tilt detecting operation in such a configuration will be described. Of the divergent light emitted from the semiconductor laser 4, the tilt detection light 13 is diffracted by the diffraction element 10 and is condensed by the collimator lens 5 before the objective lens 7. After that, the light becomes substantially parallel light by the objective lens 7 and is irradiated onto the optical recording medium 1 surface. Then, the tilt detection light 13 reflected on the optical recording medium 1 returns to the original optical path, is reflected by the beam splitter 6, passes through the detection lens 8, and is received by the two-part tilt detection light receiving element 14. Here, if the optical recording medium 1 has no tilt (tilt), there is no change in the return state of the tilt detection light 13 irradiated as a substantially parallel light beam. However, if the optical recording medium 1 has a tilt (inclination) in the radial direction, the return state of the tilt detection light 13 irradiated as a substantially parallel light beam also changes, and the tilt detection light-receiving element Since the spot position is shifted with respect to the two areas 1 and the light receiving state (light receiving amount) is different, the degree and direction of the tilt of the optical recording medium 1 are detected by arithmetically processing the detection signals obtained from the two areas. can do.

As described above, regarding the tilt detecting operation, the tilt detecting light 13 for detecting the inclination of the optical recording medium 1 surface is used.
Is a light beam which is not the original information recording / reproducing light 12 of the light emitted from the semiconductor laser 4 but has been eliminated without being taken into the collimating lens 5 in the related art. By diffracting the light that is not originally taken into the collimating lens 5 by the diffractive element 10 and taking in the light, the power on the optical recording medium 1 surface is not reduced, and the external tilt Tilt can be detected without using a sensor, the number of components can be reduced, and the number of adjustment points can be reduced. Thus, both thinness, miniaturization, and cost reduction can be achieved. Also, the tilt detection light 1
Regarding No. 3, since the irradiation light on the surface of the optical recording medium 1 is substantially parallel light, the signal can be stably detected even when the surface of the optical recording medium 1 is defocused, and the beam diameter is small. Since it is several hundred μm on one surface, it is not sensitive to the presence or absence of pits or scratches on the one surface of the optical recording medium, and stable detection of noise and the like is possible.

Now, the grating shape of the diffraction element 10 will be described. As described above, since the tilt detection light 13 is light that is not originally applied to the optical recording medium 1, the light amount is small when used in a recordable pickup. for that reason,
As shown in FIG. 2B, when the diffraction element 10 has a lattice shape that is symmetrical with respect to the traveling direction of light (in the radial direction) as shown in FIG. Since a large amount of diffracted light B is generated, the amount of light guided to the tilt detection light-receiving element 14 may be further reduced, and the S / N as a signal may be deteriorated. Therefore, in order to use more light as the tilt detection light 13, the grating shape of the diffraction element 10 is, for example, as shown in FIG.
As shown in FIG. 3A, by generating a blazed (or stepped) shape so as to be captured within the lens effective diameter φ of the collimating lens 5 in an asymmetrical shape, unnecessary generation of diffracted light is suppressed. Optical recording medium 1 for more light
Can lead to the surface.

In the case of the present embodiment, when the objective lens 7 shifts during tracking, the tilt detection light 13 also shifts. The direction of the shift is the tilt detecting light receiving element 14.
Since the direction is the same as the direction in which the tilt is shifted at the time of tilting, the signal from the tilt detection light receiving element 14 is used to separate the signal from the shift of the objective lens 7 and the signal due to the tilt, It is necessary to devise an actuator such that the light beam does not shift on the light receiving element 14.

FIGS. 3 and 4 show a second embodiment of the present invention.
It will be described based on. The same portions as those described in the first embodiment are denoted by the same reference numerals, and description thereof is omitted (the same applies to the following embodiments). Also in the present embodiment, since the tilt detection light 13 is light that is not originally applied to the surface of the optical recording medium 1, the light amount is small when the tilt detection light 13 is used in the recordable optical pickup device 3. By arranging them individually, the amount of light is secured.

That is, the corresponding tilt detection light beams 13a and 13b are diffracted at symmetrical positions on both the left and right sides (both radial directions) of the parallel plate 1 with the optical axis of the objective lens 7 therebetween.
Two diffraction elements 10a and 10b are provided. Two light receiving elements 14a and 14b for tilt detection are provided corresponding to these diffraction elements 10a and 10b.

In such a configuration, by using the two diffraction elements 10a and 10b, tilt detection can be performed by using twice as much light quantity as that of the case where only one diffraction element is used. As an example of the tilt detection in this case, for example, as shown in FIG. 4A, the respective signals in the light receiving areas of the tilt detecting light receiving elements 14a and 14b are a1, a2, b1,
Assuming that b2 is the radial tilt, for example, (a1-a2)
It is calculated as + (b1-b2). That is, the sensitivity is doubled compared to the case of one.

The two tilt detecting lights 13a and 13b
Is used, it is possible not only to double the light amount but also to detect a tilt signal from the difference signal between the two tilt detecting light receiving elements 14a and 14b. This utilizes that one of the tilt detection lights 13a and 13b is kicked by the objective lens 7 due to the inclination of the optical recording medium 1. In this case, the tilt detecting light receiving elements 14a and 14b
4 may be indivisible, and when the respective light receiving signals are a and b as shown in FIG. 4B, the radial tilt can be obtained by a−b, so that the light receiving element adjustment can be simplified.

Furthermore, there is a tangential tilt in addition to the radial tilt, but according to the present embodiment, two two-divided light receiving elements 14a and 14 for tilt detection are provided.
It is also possible to detect the tangential tilt and the radial tilt simultaneously from b. In this case, under the light receiving element configuration shown in FIG.
2) Detect radial tilt by + (b1-b2),
Depending on the tilt of the optical recording medium 1, the tilt detection light 13a or 13
The tangential tilt may be detected by (a1 + a2)-(b1 + b2) utilizing the fact that one of b is kicked by the objective lens 7.

FIGS. 5 and 6 show a third embodiment of the present invention.
It will be described based on. This embodiment shows an example of application to an optical pickup device 23 using a polarization hologram element 21 and a quarter-wave plate 22 instead of the beam splitter 6. That is, the polarization hologram element 21 and the collimator lenses 5 and 1 are placed on the optical path connecting the semiconductor laser 4 and the objective lens 7.
/ 4 wavelength plate 22 is provided in order, and the semiconductor laser 4
A light receiving element 24 (a form having both light receiving elements 9 and 14) is provided in parallel with the above. Thus, basically, the laser light emitted from the semiconductor laser 4 passes through the polarization hologram element 21, is converted into a parallel light beam by the collimator lens 5, and then converted from linearly polarized light to circularly polarized light by the １ ／ wavelength plate 22. The light is condensed and radiated on the optical recording medium 1 by the objective lens 7. Then, the reflected light from the optical recording medium 1 is re-parallelized by the objective lens 7 and then converted from circularly polarized light into linearly polarized light different from the incident light by 90 ° by the quarter-wave plate 22. Then, the light is incident on the polarization hologram element 21, diffracted in a direction different from that of the semiconductor laser 4, is incident on the light receiving element 24, and is used for signal detection. Thereby, the optical components such as the conventional beam splitter 6 can be replaced with the low-cost polarization hologram element 2.
In addition, since the semiconductor laser 4 and the light receiving element 24 can be arranged close to each other, the semiconductor laser 4 and the light receiving element 24 can be formed into one package to reduce the size.

Here, in the present embodiment, a polarization hologram element (polarization diffraction element) 25 is provided as a diffraction element at a stage preceding the polarization hologram element 21 (on the side of the semiconductor laser 4). The polarization diffraction element 25 is used because, when a simple diffraction grating is used, the diffraction element and the polarization hologram element 21 are arranged close to each other. Since the light passes through the element, some light is diffracted by the diffractive element, making accurate signal detection impossible.In addition, some of the diffracted light becomes flare, This is because the signal deteriorates. Therefore,
Using the polarization dependence of the diffraction efficiency of a polarization hologram,
By using the polarization hologram element 25 as the diffraction element, light diffracted by the polarization hologram element 21 is configured not to be diffracted by the diffraction element.

In this case, the polarization hologram element 25 is arranged so that the characteristics are opposite to those of the polarization hologram element 21. For example, as shown in FIG.
Is diffracted by the diffraction hologram element 25 and transmitted through the polarization hologram element 21 without being diffracted, while the S-polarized light returning from the optical recording medium 1 is polarized hologram as shown in FIG. It is set so that the light is diffracted by the element 21 and transmitted by the polarization hologram element 25 without being diffracted.
Thus, even if the light diffracted by the polarization hologram element 21 passes through the polarization hologram element 25, no diffracted light is generated, so that accurate signal detection without flare can be performed.

By the way, in order to manufacture the polarization hologram element 25, a material having birefringence must be finely processed. LiNbO ₃ crystal is a popular material having birefringence, but it is difficult to process finely, and it is difficult to process the lattice pitch small. Therefore, in the present embodiment, an organic material such as a polyimide resin or a PET resin having good fine processing properties is used for manufacturing the polarization hologram element 25. Since it is possible to process even a grating with a small pitch, a polarization hologram element 25 with high accuracy can be manufactured, and a tilt signal can be detected with high accuracy by irradiating the optical recording medium 1 with light with small aberration. Become.

A fourth embodiment of the present invention will be described with reference to FIG. The present embodiment is directed to a light receiving element 1 for tilt detection.
4 relates to the sensitivity characteristic. It is desirable that the tilt signal be output linearly in accordance with the tilt of the optical recording medium 1 and that the signal output greatly change (high sensitivity) even with a small tilt. Generally, the light receiving element 1
It is sufficient that the spot fluctuates greatly on the surface 4. However, since the specifications of the collimator lens 5 and the objective lens 7 are determined by the recording / reproducing characteristics, the lens cannot be adjusted to the tilt.

Therefore, in the present embodiment, the beam shape irradiating the optical recording medium 1 (accordingly, the light detecting element 1 for tilt detection)
4 (which is also the beam shape for 4) to increase the sensitivity.

As shown in FIG. 7A, the length of the spot 26 on the tilt detecting light receiving element 14 divided in the tracking direction along the track direction is a, and the length in the tracking direction is a. b, the tilt signal is the difference in the amount of received light between the two divided areas, so that the tilt signal = {(a × b / 2) − (a × b / 2)} / {(a × b
/ 2) + (a × b / 2)}. As shown in FIG. 7B, assuming that the shift amount of the spot 26 on the tilt detecting light receiving element 14 caused by the tilt is Δd, , The signal component is represented by 2a × Δd.
The larger the value, the greater the signal output for tilt and the better the sensitivity. Therefore, in the case of detecting the radial tilt, the sensitivity can be improved by making the spot formed on the optical recording medium 1 by the diffraction area of the diffraction element 10 or 25 to be a long spot in the track direction (track groove direction). Good signal can be obtained. Conversely, if it is desired to detect tangential tilt with high sensitivity, a signal with high sensitivity can be obtained by increasing the dimension b, that is, by setting the spot to be long in the tracking direction.

A fifth embodiment of the present invention will be described with reference to FIGS. Also in this embodiment, the polarization hologram elements 21 and 1/4
An example of application to an optical pickup device 23 using a wavelength plate 22 is shown. Unlike the case shown in FIG. 5, the polarization hologram element 21 is disposed on the optical path between the collimator lens 5 and the objective lens 7. I have. A transparent parallel flat plate 28 having two diffraction gratings 27a and 27b is provided in front of the polarization hologram element 21.

That is, instead of irradiating the optical recording medium 1 with substantially parallel light for tilt detection as in the case of the above-described embodiment, optical recording is performed as two convergent light or divergent light in this embodiment. This is to irradiate an unfocused position of the medium 1. Referring to FIG. 8, two divergent lights (or convergent lights) 29a and 29b are generated by diffractive elements 27a and 27b from light emitted from the semiconductor laser 4 and converted into parallel light by the collimating lens 5. is there.

Here, the diverging lights 29a and 29b are almost parallel light but slightly diverge, and when converged by the objective lens 7 as shown in FIG. A spot state as shown in FIG. In other words, while the spot 30c of the main beam 12 for recording and reproducing information forms an image on the surface of the optical recording medium 1, the spots 30a and 30b for tilt detection by the divergent lights 29a and 29b are both used. In a state before the image formation, a total of three spots 30a to 30c are formed on the surface of the optical recording medium 1.

These three spots 30a to 30c
Is reflected by the optical recording medium 1, diffracted by the polarization hologram element 21, and guided to the light receiving element 24, as shown in FIG. Here, the light receiving element 24 includes tilt detecting light receiving elements 31a and 31b having light receiving areas a to c and d to f divided into three parts on both sides of a central portion that receives the spot 30c of the main beam 12. Therefore, the two divergent light beams 29a and 29b for tilt detection are received by the two light receiving elements 31a and 31b for tilt detection, and the tilt is detected by looking at the output of (a + c + e)-(b + d + f) as in the beam size method. be able to.

As shown in FIG. 11, when the surface of the optical recording medium 1 is inclined, it becomes far from the divergent light 29a for tilt detection,
Since it is close to the divergent light 29b for tilt detection,
The spot on the light receiving element 24 is as shown in FIG. 12A, and the output of (a + c + e)-(b + d + f) becomes negative. When tilted in the opposite direction, (a + c + e)-(b + d +
Since the output of f) is positive, the tilt can be detected.

By the way, when the optical recording medium 1 is defocused as shown in FIG. 13, both spots 30a and 30b become smaller or larger similarly as shown in FIG. Defocus does not affect the tilt signal.

In the method of the present embodiment, the size of the spots 30a and 30b is used instead of the positional deviation of the spot to detect the tilt. Therefore, even if the spots 30a and 30b are displaced on the surface of the light receiving element 24, the influence on the signal is small, so that stable signal detection can be performed.

Incidentally, also in the present embodiment, the light amount for tilt detection may be weak, and the S / N as a signal may be poor. Therefore, in order to use more light for tilt detection, the diffraction elements 27a and 27b
As shown in FIG. 2A, the shape of the grating is blazed or formed in a stepwise manner so as to be left-right asymmetric with respect to the traveling direction, thereby suppressing the generation of unnecessary diffracted light. It is preferable that the light is guided to the surface of the optical recording medium 1 and the light receiving element 24.

Further, the diffraction gratings 27a and 27b correspond to FIG.
As in the case described in the above, it is desirable to configure the polarization hologram element (polarization diffraction element) so that the light diffracted by the polarization hologram element 21 is not diffracted by the diffraction elements 27a and 27b. At this time, the characteristics are made opposite to those of the polarization hologram element 21. For example, as described in FIG. 6, the P-polarized light from the semiconductor laser 4 is diffracted by the diffraction elements 27a and 27b, is not diffracted by the polarization hologram element 21, and the S-polarized light returned from the optical recording medium 1 is the polarization hologram element. At 21, diffraction occurs, and the diffraction elements 27a and 27
At b, no diffraction occurs. As a result, the light diffracted by the polarization hologram element 21 is diffracted by the diffraction elements 27a and 27b.
Since no diffracted light is generated even when the light passes through, accurate signal detection without flare can be performed. In addition, since the amount of tilt detection light does not decrease, signal detection with less noise can be performed.

In the present embodiment, the diffraction elements 27a and 27b for detecting tilt have a lens function of diverging or converging, so that the pitch is not equal and the peripheral part in particular often has a small pitch. Since processing becomes difficult when the pitch is small, it is preferable to manufacture the diffraction elements (polarization hologram elements) 27a and 27b using an organic material such as a polyimide resin or a PET resin having good fine processing properties.
Since such a material can be processed even with a grating having a small pitch, it is possible to make the diffraction elements 27a and 27b with high accuracy, and it is possible to irradiate the optical recording medium 1 with light with small aberration and detect a tilt signal with high accuracy. become able to.

[0068]

According to the optical pickup device of the first aspect of the present invention, the conventional optical pickup device is provided with a diffractive element to diffract a part of the light beam from the light source and to enter the objective lens through the collimating lens. A part of the light source light that has not been used is used for tilt detection, so tilt can be detected without lowering the light use efficiency, and the number of components is reduced because an external tilt sensor is not required. In addition to being thinner, adjustment is not required, so that cost can be reduced.Also, since the tilt detection light is radiated to a position very close to the actual information detection light via the objective lens, it is very In addition to being able to perform tilt detection with high accuracy, the beam diameter is large because the tilt detection light is irradiated in the state of substantially parallel light, and it is not sensitive to pits or scratches on the optical recording medium surface. Without It is possible to stable tilt detection in size and the like.

According to the second aspect of the present invention, the cross-sectional shape of the diffractive element in the optical pickup device according to the first aspect is such that the light incident from the light source side is diffracted into the effective diameter of the collimating lens. Since it is formed asymmetrically as viewed in the direction of travel, it is possible to suppress the generation of unnecessary diffracted light and guide more light to the optical recording medium surface,
Since the flare light does not occur and the signal light increases, stable tilt detection can be performed.

According to the third aspect of the present invention, in realizing the optical pickup device of the second aspect, by using a blazed diffractive element having a large diffraction efficiency, the amount of light used for tilt sensing can be secured. A good and reliable tilt signal can be obtained.

According to the fourth aspect of the present invention, in order to realize the optical pickup device according to any one of the first to third aspects, a plurality of diffractive elements are provided, and a tilt is generated by using the diffracted light. Since the detection is performed, a large amount of light can be applied to the optical recording medium surface, stable tilt signal detection can be performed, and tangential tilt as well as radial tilt can be detected.

According to the fifth aspect of the present invention, in realizing the optical pickup device according to any one of the first to fourth aspects, since the diffraction element is a polarization diffraction element, it is possible to return from the optical recording medium. Unwanted flare light can be reduced, and a good tilt signal with high reliability can be obtained.

According to the sixth aspect of the present invention, in realizing the optical pickup device according to the fifth aspect, by using an organic film having excellent fine workability as a material of the polarization diffraction element, processing with a small pitch can be achieved. , And a highly accurate and efficient polarization diffraction element can be manufactured. Therefore, a highly reliable signal can be obtained by irradiating light with less aberration.

According to the seventh aspect of the present invention, in realizing the optical pickup device according to any one of the first to sixth aspects, the spot for detecting the tilt has a short axis in a direction in which the tilt moves. As a result, the sensitivity is improved, and the tilt signal can be detected stably with respect to noise.

According to the optical pickup device of the present invention, a plurality of diffracted lights are applied to the optical recording medium in a defocused state in order to detect a tilt. Since the magnitude of the tilt is different, the amount of tilt can be determined based on the difference in intensity. This facilitates the alignment of the light-receiving element for tilt detection, facilitates the adjustment of assembly, changes over time and displacement. The tilt can be detected stably.

According to the ninth aspect of the present invention, each of the diffraction elements in the optical pickup device according to the eighth aspect has a light-cross-sectional shape such that light incident from the light source side is diffracted into the effective diameter of the objective lens. Is formed asymmetrically as viewed in the direction of travel, so that generation of unnecessary diffracted light can be suppressed, more light can be guided to the optical recording medium surface, and flare light does not occur and signal light increases. Therefore, stable tilt detection can be performed.

According to the tenth aspect, the ninth aspect is provided.
In realizing the optical pickup device described above, by using a blazed diffractive element having a large diffraction efficiency, it is possible to secure a light amount used for tilt sensing and obtain a highly reliable and favorable tilt signal.

According to the eleventh aspect, according to the eighth aspect,
In realizing the optical pickup device described in any one of the above items 10 to 10, since the diffraction element is a polarization diffraction element, unnecessary flare light returned from the optical recording medium can be reduced, and reliability can be improved. A high favorable tilt signal can be obtained.

According to the twelfth aspect, according to the first aspect,
In realizing the optical pickup device described in 1, the use of an organic film having excellent micro-processability as a material of the polarization diffraction element makes it possible to cope with processing with a small pitch and to produce a polarization diffraction element with high accuracy and efficiency. Therefore, a highly reliable signal can be obtained by irradiating light with smaller aberration.

According to the optical disk apparatus of the present invention, since the optical pickup apparatus is provided with a small and thin optical pickup apparatus which does not require an external tilt sensor, the optical disk apparatus is provided. The optical disk device itself can be made thinner and smaller, and it is possible to provide an optical disk device suitable for being mounted on a notebook computer or the like.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram illustrating an optical disc device according to a first embodiment of the present invention.

FIG. 2 is a configuration diagram including a partially enlarged view showing a configuration example of the diffraction grating.

FIG. 3 is a schematic configuration diagram illustrating an optical pickup device according to a second embodiment of the present invention.

FIG. 4 is a plan view for explaining a light receiving state of a light receiving element for tilt detection.

FIG. 5 is a schematic configuration diagram illustrating an optical pickup device according to a third embodiment of the present invention.

FIG. 6 is a configuration diagram for explaining optical characteristics of the polarization hologram elements.

FIG. 7 is a schematic plan view showing an image spot formed on a tilt detecting light receiving element according to a fourth embodiment of the present invention.

FIG. 8 is a schematic configuration diagram illustrating an optical pickup device according to a fifth embodiment of the present invention.

FIG. 9 is an explanatory diagram showing an enlarged image formation state near the optical recording medium.

FIG. 10 is a plan view showing a state of an image forming spot and a light receiving spot on a light receiving element.

FIG. 11 is an explanatory diagram showing an enlarged image formation state near the optical recording medium at the time of tilt.

FIG. 12 is a plan view showing a state of an image forming spot and a light receiving spot on a light receiving element.

FIG. 13 is an explanatory diagram showing an enlarged image formation state near the optical recording medium at the time of defocusing.

FIG. 14 is a plan view showing a state of an image forming spot and a light receiving spot on a light receiving element.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 optical recording medium 2 drive source 3 optical pickup device 4 light source 5 collimating lens 7 objective lens 9 light receiving element 10 diffractive element 14 tilt detecting light receiving element 23 optical pickup device 24 light receiving element 25 polarization diffraction element, diffraction element 27a, 27b diffraction element 31a, 31b Photodetector for tilt detection

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) G03H 1/04 G03H 1/04 G11B 7/095 G11B 7/095 GF term (Reference) 2H049 AA03 AA13 AA57 AA65 BA05 BA46 BC01 BC21 CA15 CA20 CA28 2K008 AA00 EE01 FF13 FF14 5D118 AA03 AA14 BA01 BB02 BF02 BF03 CD04 CF03 CG03 CG04 CG10 CG24 DC02 5D119 AA04 AA28 AA43 BA01 DA01 DA05 EA01 JA11 JA23 KA02 KA02

Claims (13)

[Claims] 1. A light beam emitted from a light source is condensed and irradiated on a recording surface of an optical recording medium via a collimating lens and an objective lens, and a reflected light beam reflected from the recording surface of the optical recording medium is returned to the objective light. In an optical pickup device that records or reproduces information on the optical recording medium by guiding to a light receiving element via a lens, a part of a light beam emitted from the light source is diffracted, and the objective lens passes through the collimating lens through the collimating lens. A diffractive element that irradiates the optical recording medium as substantially parallel light, and receives again the reflected light from the optical recording medium that has been diffracted and irradiated by the diffractive element via the objective lens to tilt the optical recording medium. An optical pickup device comprising: a tilt detecting light receiving element for detecting. 2. The cross-sectional shape of the diffractive element is formed to be asymmetrical left and right as viewed in the traveling direction of the light so that light incident from the light source side is diffracted into a lens effective diameter of the objective lens. The optical pickup device according to claim 1, wherein: 3. The optical pickup device according to claim 2, wherein the diffractive element has a cross-sectional shape that is asymmetrical in the left-right direction when viewed in the light traveling direction due to the blaze. 4. The optical pickup device according to claim 1, wherein a plurality of the diffractive elements are provided at different positions around the optical axis of the objective lens. 5. The optical pickup device according to claim 1, wherein the diffraction element is a polarization diffraction element whose diffraction efficiency depends on a polarization direction of incident light. 6. The optical pickup device according to claim 5, wherein said polarization diffraction element is formed of an organic film. 7. The optical pickup device according to claim 1, wherein the diffraction region of the diffraction element has a shape elongated in a track groove direction in the optical recording medium. 8. A light beam emitted from a light source is condensed and irradiated on a recording surface of an optical recording medium via a collimator lens and an objective lens, and a reflected light beam reflected from the recording surface of the optical recording medium is returned to the objective light. In an optical pickup device for recording or reproducing information on the optical recording medium by guiding the light to a light receiving element via a lens, a plurality of light sources are provided at different positions around the optical axis of the objective lens, and are emitted from the light source. A plurality of diffractive elements for irradiating the optical recording medium such that a part of the light beam having passed through the collimating lens is diffracted to form an image at a non-focus position on the recording surface of the optical recording medium by the objective lens; The reflected light from the optical recording medium diffracted and irradiated by the diffractive element is again received via the objective lens, and the tilt of the optical recording medium is determined by the difference in intensity. Optical pickup apparatus comprising: the tilt detecting light-receiving element for detecting a. 9. The cross-sectional shape of each of the diffractive elements is formed to be asymmetrical left and right when viewed in the traveling direction of the light so that light incident from the light source side is diffracted into a lens effective diameter of the objective lens. The optical pickup device according to claim 8, wherein: 10. The optical pickup device according to claim 9, wherein each of the diffractive elements has a cross-sectional shape which is asymmetrical in the left-right direction when viewed in the light traveling direction by blazing. 11. The optical pickup device according to claim 8, wherein each of the diffraction elements is a polarization diffraction element whose diffraction efficiency depends on a polarization direction of incident light. 12. The optical pickup device according to claim 11, wherein said polarization diffraction element is formed of an organic film. 13. A drive source for rotating and driving an optical recording medium, and the optical pickup device according to claim 1, which is capable of moving a seek relative to the optical recording medium in a radial direction. An optical disc device characterized by the above-mentioned.