JP2003098350A - Optical element, optical pickup device and optical disk drive device using the optical element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To realize making a device thinner by improving the light utilization efficiency of the device in a pickup for recording or reproducing with, for example, light having a plurality of wavelengths. SOLUTION: Linearly polarized light emitted from a 650 nm LD 1 and 780 nm LD 2 is passed through a first and second holograms 3 and 4, transformed into parallel light at a collimating lens 5, reflected on an optical element 6 and condensed with an objective lens 7, thus an optical recording medium 8 is irradiated with the light. The incident linearly polarized light is given a phase difference by 1/4 wavelength when the light is passed and reflected at the optical element 6 and emitted as circular polarized light. The light reflected on the optical recording medium 8 is returned along the original optical path, is given a phase difference by 1/4 wavelength at the optical element 6 and transformed into linearly polarized light of which the polarized direction is different from that of the emitted light by 90 deg.. The linearly polarized light is diffracted with either of the first and the second holograms 3 and 4 which correspond to the respective wavelengths of light and received with a light receiving element 9.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical element, an optical pickup device, and an optical drive device using the optical pickup device, and more particularly to an optical pickup device and an optical drive device that share a DVD and a CD.

[0002]

2. Description of the Related Art For example, Japanese Patent Application Laid-Open No. 6-295464 discloses an optical pickup device using a quarter wavelength plate. In this device, the quarter wavelength plate plays a role of improving light utilization efficiency. Is responsible for The quarter-wave plate converts the linearly polarized light from the laser light source into circularly polarized light and irradiates it to the disc, and converts the circularly polarized light reflected by the disc into linearly polarized light whose polarization direction is 90 ° different from the light emitted from the laser. , Plays the function of guiding light to the light receiving element without loss.
While the quarter-wave plate can improve the light use efficiency, it is apt to be disposed on the optical path as close to the objective lens as possible because a phase difference is likely to occur at the reflecting surface when converted into circularly polarized light.

For example, in an optical pickup device, disposing a quarter-wave plate directly below an objective lens is a desirable means from the viewpoint of managing the phase difference. However, if the quarter-wave plate is arranged directly below the objective lens, there arises a problem that the entire drive device becomes thick in the height direction. Therefore, in order to make the device thinner, it is possible to reduce the thickness by omitting the quarter-wave plate by giving the function of the quarter-wave plate to the rising reflection mirror also arranged under the objective lens. There is a method to.

In recent years, an optical disk drive device called a multi-writer has been developed which can perform recording and reproduction on both CD and DVD media. In order to be able to record CDs and DVDs,
High light utilization efficiency is required for both media. Therefore, 780 nm light used for CD and DV
A 1/4 wavelength plate corresponding to 2 wavelengths that functions as a 1/4 wavelength plate for both wavelengths of 650 nm light used for D is required.

However, a normal wave plate cannot provide a function as a perfect quarter wave plate for both of the above two wavelengths, and 90 ° () for both incident lights of two wavelengths. It is not possible to give a phase difference of (1/4 wavelength), and a phase difference of, for example, 100 ° or 80 ° slightly deviated from 90 ° is given. In such a case, the light use efficiency will be reduced by the amount that the phase difference deviates from 90 °.

[0006]

As described above, C
In an optical disc drive device called a multi-writer capable of recording and reproducing D and DVD, downsizing and thinning are required. This is because mobile type personal computers such as notebook personal computers are rapidly becoming more popular than desktop type personal computers, and drive devices are also required to be smaller and thinner.

The present applicants have proposed a method of mounting a CD laser chip, a DVD laser chip, and a PD chip in one package to reduce the size of the optical pickup device in order to reduce the size of the device. Further, since high light utilization efficiency is required in order to record both a CD and a DVD, a beam shaping prism is used or an optical isolator configuration using polarized light is used.

When the beam shaping prism is used, a mirror for turning back the optical path bent by the prism is also required. However, on the mirror surface, a phase difference is likely to occur at the time of reflection, and when the phase difference occurs, circularly polarized light becomes elliptically polarized light, which disturbs the polarized light in the optical isolator structure and reduces the light utilization efficiency.

The optical isolator structure not only improves the light utilization efficiency, but also reduces the light returning to the light source and is resistant to noise. However, a beam shaping prism is used to ensure high light utilization efficiency. However, when the number of mirrors increases, a phase difference occurs at the time of reflection, and the polarization in the optical isolator is disturbed by this phase difference, so the light utilization efficiency decreases, the amount of light returning to the light source increases, noise increases, and S / N decreases. I will end up. Therefore, it becomes an issue to make the optical pickup device compact and achieve high light utilization efficiency.

The present invention has been made in view of the above circumstances, and is an optical element applicable to an optical pickup device capable of handling a plurality of wavelengths of light such as a DVD and a CD. An optical element having both a retardation plate function and a reflection mirror function capable of giving a phase difference of ¼ wavelength, and an optical pickup device which uses the optical element to enhance the light utilization efficiency of the device and realize a thin structure. An optical disk drive device using the optical pickup device is provided.

[0011]

According to a first aspect of the present invention, there is provided wideband quarter-wave plate means for providing a phase difference of quarter wavelength to each of a plurality of specific wavelength lights, and Total reflection means for reflecting all of a plurality of specific wavelength light, and incident light is reflected by the total reflection means after being acted on by the broadband ¼ wavelength plate, and the reflected light is again reflected by the broadband 1 / 4 wavelength plate means, which is an optical element which allows incident light to be emitted by the broadband ¼ wavelength plate means undergoing a total of two actions by the broadband ¼ wavelength plate means. Is, by selecting and stacking a plurality of organic films having different wavelength dispersion characteristics that are wavelength dependence of the phase difference, the wavelength dispersion of each of the organic films is compensated, and for all of the plurality of specific wavelengths. Multi-layered so as to add a phase difference of 1/4 wavelength It is obtained by said to have a machine membrane structure.

According to the second aspect of the present invention, of the plurality of specific wavelength lights, at least a part of the specific wavelength lights is ¼.
A quarter retardation plate having a function of giving a phase difference of wavelengths and a function of giving a predetermined amount of phase difference other than a quarter wavelength to light other than the partial wavelength light among the plurality of specific wavelength lights. Means, and total reflection means for reflecting all of the plurality of specific wavelength light, incident light is reflected by the total reflection means after being acted on by the quarter wavelength plate means, and the reflected light is It is characterized in that it is configured so that the incident light is acted upon by the quarter wavelength plate means a total of two times to be emitted by entering the quarter wavelength plate means again.

According to a third aspect of the present invention, there is provided a wavelength selective reflection means for reflecting a part of wavelength light of a plurality of specific wavelength light and transmitting another wavelength light, and the other of the plurality of specific wavelength light. It has a quarter-wave plate means for giving a phase difference of a quarter-wavelength to the wavelength light and a total reflection means for reflecting at least the other wavelength light, and the incident light is part of the wavelength selection means. Of the reflected light of the wavelength of and the transmitted light of the other wavelength,
After the transmitted light is acted on by the quarter-wave plate means, it is reflected by the total reflection means, and the reflected light again enters the quarter-wave plate means and is acted on by the wavelength selection means. It is characterized in that it is configured so as to pass through the means and emit.

According to a fourth aspect of the present invention, a semiconductor laser capable of emitting a plurality of lights of specific wavelengths and a light beam from the semiconductor laser are irradiated onto the recording surface of the optical recording medium so that the optical recording medium is irradiated with light. An optical unit having an objective lens for converging and a coupling lens, and a light receiving element for receiving a returning light flux when the light guided by the optical unit is reflected on the recording surface, In an optical pickup device having a function of recording or reproducing, the optical pickup device is a broadband quarter-wave plate that gives a phase difference of a quarter wavelength for each wavelength light to all of the plurality of specific wavelength light. And an optical element having total reflection means for reflecting all of the plurality of specific wavelength lights, the optical element being arranged on the optical path between the objective lens and the coupling lens. It is obtained by the features and.

According to a fifth aspect of the present invention, in the fourth aspect of the invention, the broadband quarter-wave plate means is composed of a multilayer organic film in which a plurality of organic films are stacked.

According to a sixth aspect of the present invention, in the fifth aspect of the present invention, the multi-layer organic film of the wideband quarter-wave plate means is selected from a plurality of organic films having different wavelength dispersion characteristics that are wavelength dependence of phase difference. And are laminated so that the wavelength dispersion of each of the organic films is compensated, and a phase difference of ¼ wavelength can be imparted to all of the plurality of specific wavelength lights. It is what

According to a seventh aspect of the present invention, in the fifth or sixth aspect of the present invention, the multilayer organic film in the broadband quarter-wave plate means is formed by using an organic film made of polycarbonate, polyvinyl alcohol, or polymethylmethacrylate. It is characterized by being present.

According to an eighth aspect of the present invention, a semiconductor laser capable of emitting a plurality of specific wavelengths of light and a light beam from the semiconductor laser are irradiated onto the recording surface of the optical recording medium so that the optical recording medium is irradiated with light. An optical unit having an objective lens for converging and a coupling lens, and a light receiving element for receiving a returning light flux when the light guided by the optical unit is reflected on the recording surface, In an optical pickup device having a function of recording or reproducing, the optical pickup device has a function of giving a phase difference of ¼ wavelength to at least a part of wavelength lights of the plurality of specific wavelength lights, and ¼ retardation plate means having a function of giving a predetermined amount of phase difference other than ¼ wavelength to light other than the partial wavelength light among the plurality of specific wavelength lights, and the plurality of specific wavelength lights Comprising an optical element having a total reflection means for reflecting all optical element is obtained by, characterized in that disposed on the optical path between the objective lens and the coupling lens.

According to a ninth aspect of the present invention, in the eighth aspect of the present invention, the part of the wavelength light which gives the phase difference of ¼ wavelength is one of the plurality of specific wavelength lights, which is one of the shorter wavelengths. It is characterized by having a plurality of wavelengths of light.

According to a tenth aspect of the present invention, a semiconductor laser capable of emitting a plurality of specific wavelengths of light and a light beam from the semiconductor laser are irradiated onto the recording surface of the optical recording medium so that the optical recording medium is irradiated with light. An optical unit having an objective lens for converging and a coupling lens, and a light receiving element for receiving a returning light flux when the light guided by the optical unit is reflected on the recording surface, In an optical pickup device having a function of recording or reproducing, the optical pickup device comprises a wavelength selective reflection means for reflecting a part of wavelength light of the plurality of specific wavelength light and transmitting another wavelength light; 1/4 wavelength plate means for giving a phase difference of 1/4 wavelength to the other wavelength light transmitted through the wavelength selecting means among the specific wavelength light, and a total reflection hand for reflecting the other wavelength light. Comprising an optical element having bets, in which the optical element is characterized in that it is arranged on the optical path between the objective lens and the coupling lens for converging the light to the optical recording medium.

According to an eleventh aspect of the invention, in the invention of the tenth aspect, the other wavelength light that gives the phase difference of ¼ wavelength is one or a plurality of light rays on the short wavelength side of the plurality of specific wavelength light rays. It is characterized by being the light of the wavelength.

The twelfth aspect of the present invention includes the fourth to eleventh aspects.
In any one of the inventions described above, the optical element is characterized by having a light speed shaping means for shaping an incident light beam.

According to a thirteenth aspect of the invention, in the twelfth aspect of the invention, the optical element is inclined at an angle between the normal line of the incident surface of the optical element and the optical axis of the objective lens is smaller than 45 °. It is characterized by being arranged as follows.

The invention of claim 14 is the invention of claim 12 or 1.
In the invention of claim 3, there is provided a configuration in which at least the semiconductor lasers for emitting the plurality of specific wavelengths of light are mounted in one package, and the optical element includes the optical axis of the emitted light of each wavelength of the incident light and the objective. It is characterized in that it is configured to be at least parallel to the optical axis of the lens.

The invention of claim 15 is the invention of claims 4 to 14.
In any one of the inventions described above, the optical element is characterized by at least including a surface that forms an angle of 90 ° with respect to the optical axis of the objective lens.

[0026] The invention of claim 16 is the invention according to claims 4 to 15.
In any one of the inventions, the optical element is arranged on an optical path between an objective lens that converges light on an optical recording medium and a mirror that is driven integrally with the objective lens. Is.

The invention of claim 17 is the invention of claims 4 to 16.
In any one of the inventions described above, the plurality of specific wavelength lights are lights having wavelengths of 650 nm and 780 nm.

The invention of claim 18 relates to claims 4 to 17.
An optical disk drive device having the optical pickup device according to any one of 1.

[0029]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS (Embodiment 1; Corresponding to Claims 1 and 4 to 7) An optical pickup device is, for example, a DVD.
In order to improve the light utilization efficiency for both optical systems of CD and CD, a quarter wavelength (90
A broadband quarter-wave plate that can provide a phase difference of (°) is used. The broadband quarter-wave plate is provided with a reflecting function and is arranged under the objective lens, so that it also has a rising reflecting mirror function. As a result, the phase difference does not increase even if the number of reflection surfaces increases due to the adoption of the beam shaping prism, and the deterioration of the signal component can be suppressed, and unlike the conventional case, the transmission type quarter-wave plate is not arranged below the objective lens. Therefore, the device can be made thinner.

FIG. 1 is a diagram for explaining a first embodiment of the present invention, and shows a schematic configuration of an optical pickup device using an optical element according to the present invention. FIG. 1 is for explaining the action of light emitted from a 650 nm semiconductor laser of the two semiconductor lasers of 650 nm and 780 nm included in the optical pickup device. Figure 1
1, 1 is a 650 nm LD (semiconductor laser), 2 is a 780 nm LD (semiconductor laser), 3 is a first hologram, 4 is a second hologram, 5 is a collimating lens (coupling lens), 6 is an optical element, 7 is an objective lens, 8
Is an optical recording medium, and 9 is a light receiving element. 650 which is the light source
The linearly polarized light emitted from the nmLD 1 is transmitted through the first hologram 3 and the second hologram 4 in order, becomes parallel light by the collimator lens 5, is reflected by the optical element 6, and is condensed by the action of the objective lens 7. The recording medium 8 is irradiated.

In the optical element 6, when the incident linearly polarized light is transmitted and reflected, a total phase difference of ¼ wavelength is given, and the light is converted into circularly polarized light and emitted, and irradiates the optical recording medium 8. Then, the light reflected by the optical recording medium 8 returns to the original optical path, is reflected again by the optical element 6, and is subjected to the same action at this time to be given a phase difference of ¼ wavelength. It becomes linearly polarized light whose polarization direction is different from that of the outgoing light by 90 °.
This linearly polarized light is diffracted by the second hologram 4 and received by the light receiving element 9. At this time, the second hologram 4 is 650
It is a polarization hologram that diffracts nm light and has different diffraction efficiency depending on the polarization direction.

FIG. 2 is a diagram for explaining the action of light emitted from the 780 nm LD 2 in the first embodiment shown in FIG. The linearly polarized light emitted from the 780 nm LD 2 passes through the first hologram 3 and the second hologram 4 as in FIG. 1, becomes parallel light by the collimator lens 5, is reflected by the optical element 6, and is condensed by the objective lens 7. To irradiate the optical recording medium 8. Here, when reflected by the optical element 6, a phase difference of about ¼ wavelength is given, so that the reflected light becomes substantially circularly polarized light and irradiates the optical recording medium 8.

The irradiation light reflected by the optical recording medium 8 returns to the original optical path and is reflected again by the optical element 6, and at this time, a phase difference of ¼ wavelength is similarly given and 780 nm LD2
The output light is linearly polarized light having a 90 ° polarization direction different from that of the output light. This linearly polarized light is diffracted by the first hologram 3 and received by the light receiving element 9. The first hologram 3 is 780 nm
It is a polarization hologram that diffracts light and has different diffraction efficiency depending on the polarization direction.

FIG. 3 is a diagram for explaining the detailed structure and operation of one embodiment of the optical element according to the present invention. In the figure, 6 is an optical element, 6a and 6d are glass substrates, and 6b is a phase difference. The film 6c is a total reflection film. The optical element 6 includes a retardation film 6b that functions as a broadband wavelength plate that imparts a phase difference to a plurality of specific wavelength lights (650 nm and 780 nm wavelength lights in this embodiment) as described above, and incident light linearly polarized light. And a total reflection film 6c that causes the linearly polarized light to pass through the retardation film 6b twice and be given a phase difference of ¼ wavelength to become circularly polarized light. As the retardation film 6b that functions as a broadband quarter-wave plate, a structure in which a plurality of organic films are stacked to suppress wavelength dispersion is used.

As shown in FIG. 3, the optical element 6 is constructed such that a retardation film 6b and a total reflection film 6c are sandwiched between a glass substrate 6a and a glass substrate 6d. The linearly polarized light emitted from the laser light source passes through the glass substrate 6a and passes through the retardation film 6b. At this time, the retardation film 6b gives a phase difference and becomes elliptically polarized light. Then, the light is reflected by the total reflection film 6c and transmitted again through the retardation film 6b. Here, the phase difference is further given, and the phase difference of 1/4 wavelength is added in total to become almost circularly polarized light, and goes toward the disk. This retardation film 6b
Is a broadband quarter-wave plate, 660nm, 780n
A phase difference of ¼ wavelength (90 °) is given to any wavelength light of m. In the optical pickup device configured as described above, all the elements on the optical path except the optical element 6 and the optical recording medium shown in this embodiment transmit linearly polarized light, so that signal deterioration due to the phase difference is minimized. Can be suppressed to

FIG. 12 is a diagram showing an example of an optical system when the size of the pickup is reduced by using, for example, a beam shaping prism. In FIG. 12, 17 is a beam shaping prism and 1 is a beam shaping prism.
8 is a rising reflection mirror, 13 is a mirror-integrated actuator, 14 is a reflection mirror, 15 is a hologram unit,
Reference numeral 15a is a quarter-wave plate, and 16 is an objective lens.

In FIG. 12, linearly polarized light emitted from a light source (not shown) is converted into circularly polarized light by the quarter-wave plate 15a provided in the hologram unit 15, and the beam shaping prism 11, the reflection mirror 14, and the mirror integrated type. The light is reflected by the mirror of the actuator 13 and the rising reflection mirror 12, enters the objective lens 16, is condensed, and illuminates the disk. Then, the light reflected by the disk travels in the reverse path of the incident light and returns to the quarter-wave plate 15a. During this time, there are four surfaces (eight surfaces in total considering the round-trip optical path) that are reflected in the circularly polarized state, so the light utilization efficiency will be improved unless the phase is shifted on all four surfaces. Will fall.

As described above, in order to prevent the phase shift from occurring for both the DVD and the CD wavelength light, FIG.
It is necessary to apply a multilayer coat of about 30 layers or more on all of the four reflecting surfaces shown in 2. Such a multi-layer coat is necessary to secure a high reflectance for two-wavelength light and to prevent a phase difference for both two-wavelength light. This is an issue unique to pickups. Even if the individual phase shifts can be reduced by the multi-layer coating, since there are four surfaces that require the multi-layer coating, even if the phase shifting is slight, the total phase variation is caused by adding these. Will become bigger.

In the present invention, the hologram unit 15 in FIG. 12 is not provided with the quarter wave plate 15a, and the rising reflection mirror 18 is made to have the function of the quarter wave plate.
As a result, the beam shaping prism 17, the rising reflection mirror 18, and the mirror of the mirror-integrated actuator 13 reflect linearly polarized light in any of the two wavelengths of light, so that a multilayer coat of approximately 30 layers or more is applied. Since it is not necessary and a usual metal film coat can be used, the cost can be reduced.

650 nm wavelength light as described above, and 78
To obtain high light utilization efficiency in both of the above wavelength lights by an optical element that also serves as a rising reflection mirror and a broadband quarter wavelength plate that gives a phase difference of 1/4 wavelength to both 0 nm wavelength light. And the phase variation is reduced,
No expensive multi-layered reflective film is required. Moreover, since the above-mentioned optical element has a reflection function, it can be installed in place of the conventional stand-up reflection mirror, and the height of the optical pickup device does not become high. Is also a suitable configuration.

That is, in the optical pickup device according to the present embodiment, since the phase difference of about 90 ° is given to the two wavelength lights by the wide band 1/4 wavelength plate, the light utilization efficiency of both wavelength lights should be improved. Therefore, it is suitable for a multi-light pickup. In addition, the optical element that gives a phase difference to linearly polarized light and converts it into circularly polarized light is arranged on the optical path immediately before the objective lens, so even if there are many reflective surfaces in the pickup component, those reflective surfaces will be linear. Since the light is reflected by polarized light, it is not necessary to form a multilayer film on the reflection surface for maintaining the phase, and the cost of the device can be reduced.

Next, the multilayer retardation film functioning as a broadband quarter-wave plate as described above will be specifically described.
FIG. 13 is a diagram for explaining the function of the quarter-wave plate used as the optical element of the present embodiment, and FIG. 13 (A) is a diagram for explaining the polarization conversion function of the quarter-wave plate. 1
FIG. 1 is a diagram for explaining chromatic dispersion of a quarter wave plate.
3 (B).

As described above, in this embodiment, 650n
1/4 wavelength (9
A broadband wave plate that gives a phase difference of 0 ° is used. In order to give a phase difference of 1/4 wavelength to both wavelength lights at the same time, it is necessary that the wavelength dispersion in the 1/4 wavelength plate is small. For that purpose, a structure may be adopted in which a plurality of retardation films are stacked to cancel the chromatic dispersion of each retardation film.

In the present invention, a broadband quarter-wave plate having a structure in which wavelength dispersion is suppressed by stacking a plurality of organic films is used. That is, as shown in FIG.
For example, by stacking two organic films, 650 nm and 7
Polarization conversion of light having a wavelength of 80 nm is performed. As for the chromatic dispersion at this time, as shown in FIG. 13B, by stacking two organic films, the chromatic dispersion is made uniform as compared with the case of one organic film. Examples of such an organic film include polycarbonate, polyvinyl alcohol, polymethylmethacrylate, and the like, and cost reduction can be achieved by using an inexpensive organic material such as polyvinyl alcohol or polycarbonate.

Further, it is expected that a higher density optical disc using a blue laser will appear in the future. In such cases,
Three types of wavelength light: λ1, λ2, λ3 (λ1 <λ2 <λ3)
It is necessary to give a phase difference of 1/4 wavelength at the same time. In that case, the broadband wavelength plate must have wavelength dispersion characteristics such that the phase differences become equal to the above three types of wavelength light. In this case, by combining a plurality of organic materials such as polyvinyl alcohol and polycarbonate, 1 /
It is necessary to obtain a phase difference of 4 wavelengths.

FIG. 14 is a diagram for explaining another function of the quarter-wave plate according to the present invention, and FIG. 1 is a diagram for explaining the polarization conversion function of the quarter-wave plate having the three-layer structure.
FIG. 4B is a diagram for explaining the wavelength dispersion of the quarter-wave plate having a three-layer structure in FIG. 4A.
As shown in FIG. 14A, by stacking three organic films, for example, polarization conversion of light having wavelengths of 410 nm, 650 nm, and 780 nm is performed. At this time, as shown in FIG. 14B, by stacking three organic films, the chromatic dispersion can be suppressed low for the corresponding wavelengths (410 nm, 650 nm, 780 nm). That is, FIG.
As shown in (B), 1/4 over the entire region of λ1 to λ3.
Even if the phase difference in wavelength is not maintained, the phase difference may be set to ¼ wavelength in accordance with λ1, λ2, and λ3 which are discretely present.

As described above, according to the present invention, a wide band 1/4 wavelength plate can be realized at low cost by stacking a plurality of organic films to reduce the wavelength dispersion, which is advantageous in reducing the cost of the pickup.

(Embodiment 2; Corresponding to Claims 2, 8 and 9) In the above-mentioned Embodiment 1, a 1/4 wavelength unit is used for all two or three wavelength lights by the broadband 1/4 wavelength plate. A phase difference is given so that high light utilization efficiency can be obtained in all wavelength light. The optical pickup device of the present embodiment enhances the light utilization efficiency by giving a phase difference of ¼ wavelength to circularly polarized light only for the DVD wavelength light, for example.
A wavelength difference for D is given a phase difference other than a quarter wavelength to be elliptically polarized light, and the light utilization efficiency does not become higher than that of a DVD, but a conventional hologram unit can be diverted to achieve cost reduction. Is.

Generally, in the development of LD, the short wavelength L
Since it is difficult to increase D output, as described above, λ
For wavelengths of 1 and λ2 (λ1 <λ2), it is often necessary to increase the light utilization efficiency of the wavelength light of λ1 on the short wavelength side. Therefore, in the present embodiment, the phase difference of 1/4 wavelength is not given to the two wavelength lights, but the phase difference of 1/4 wavelength is given to only one wavelength light (especially the wavelength light on the short wavelength side). The other wavelength light is given a phase difference other than the quarter wavelength.

FIG. 4 is a graph showing an example of the relationship between the phase difference and the signal strength. For example, 1 / for wavelength light of 650 nm
Phase difference of four wavelengths (90 °) (650/4 = 162.5n
m), the 650 nm wavelength light becomes circularly polarized light,
High light utilization efficiency can be obtained. At this time, the above 162.5
Since the phase difference of nm corresponds to the phase difference of 75 ° in the case of light having a wavelength of 780 nm (162.5 / 780 × 360 = 75), the obtained signal strength is about 92 as shown in FIG.
%, The light use efficiency is reduced by about 8% with respect to the phase difference of 90 °.

In the above method, the efficiency is reduced by 8% with one wavelength light (wavelength light on the long wavelength side), but on the long wavelength light side, the LD itself has a high output, and the light receiving element itself has a high output. Considering that the sensitivity is also large output on the long wavelength side, there is a possibility that the specifications of the dual wavelength recording type drive device can be sufficiently satisfied. Moreover, as the wave plate, a normal wave plate having a wide band can be used, so that the cost can be reduced.

Also, when the method of this embodiment is applied to three wavelengths, the same thing as the case corresponding to the above two wavelengths can be said. For example, three wavelengths λ1, λ2, λ3 (λ1 <λ2 <
When λ3) is 410 nm, 650 nm, and 780 nm, the output of λ1 (410 nm) LD is currently delayed most, so in the three-wavelength compatible optical disk drive device, the ¼ wavelength plate has the shortest wavelength. λ1 (41
The phase difference of 1/4 wavelength with respect to (0 nm) may be given.

The quarter wavelength of 410 nm is 102.5 nm
And the phase difference is 57 with respect to λ2 (650 nm).
However, the light utilization efficiency may be reduced to 80% or less, but it is at a level that can be sufficiently utilized for reproduction. When the decrease in the light use efficiency of λ2 (650 nm) is not desired, it is effective to use the wideband 1/4 wavelength plate as shown in the first embodiment.

Similarly, when the third wavelength is 780 nm, the angle is 47 °, and the light utilization efficiency is 60% as shown in FIG.
Although it drops to below, it is at a level where it can be sufficiently used for recycling. Moreover, the output of the 780 nm LD is increasing, and the absolute power of the LD can be secured even if the light utilization efficiency is low. Therefore, if the recording speed is lowered a little, it is possible to secure the optical power at a sufficiently recordable level.

In this embodiment, for example, a phase difference of 1/4 wavelength is given only to the wavelength light for DVD whose LD output is not sufficient, and a phase difference slightly deviated from the quarter wavelength to the wavelength light for CD. By making it applicable even if there is a DVD
The light utilization efficiency of the optical system for use can be improved, and conventional parts can be used for the optical system for CD, so that the cost can be reduced.

(Third Embodiment: Corresponding to Claims 3, 10 and 11) In the first and second embodiments, it is assumed that both the DVD and the CD are recorded or reproduced together, and the wavelengths corresponding to both media are set to 1 for both wavelengths. / 4 wavelength or a predetermined phase difference is given. However, if the emission power of the LD light source is sufficiently large, sufficient recording power can be secured on the optical recording medium 8 without using an isolator structure using a polarization hologram and a quarter-wave plate. In this case, an ordinary non-polarization hologram can be used without using a polarization hologram, which is advantageous in terms of cost. That is, in the present embodiment, for example, the phase difference of ¼ wavelength is given only to the wavelength light for DVD to improve the light utilization efficiency, and the phase difference is not given to the wavelength light for CD. Although the light utilization efficiency does not increase, the conventional hologram unit can be applied to reduce the cost.

At present, the output of the 780 nm LD for the CD system is considerably high and the sufficient power is obtained, while the output of the 650 nm LD for the DVD system is not relatively high and the sufficient power is obtained. Has not been done. CD
A non-polarization hologram is used for the system, and 1/4 for the DVD system.
In many cases, it has an isolator configuration using a wave plate. In order to deal with such a configuration, the optical element of the present invention can be configured as shown in FIG.

FIG. 5 is a view for explaining the structure and operation of still another embodiment of the present invention, in which 10 is an optical element,
10a is a glass substrate, 10b is a wavelength selection film, 10c is a retardation film, 10d is a total reflection film, and 10e is a glass substrate. The optical element 10 of this embodiment is the optical element 6 shown in FIG.
In this configuration, a wavelength selection film is added between the glass substrate 6a and the retardation film 6b. That is,
The optical element 10 of the present embodiment has a structure in which a wavelength selection film 10b, a retardation film 10c, and a total reflection film 10d are sandwiched in this order from the incident side between a glass substrate 10a and a glass substrate 10e. .

The 780 nm wavelength light emitted from the light source is
The light passes through the glass substrate 10a, is reflected by the wavelength selection film 10b, and travels toward the optical recording medium surface. On the other hand, 6 emitted from the light source
The 50 nm light transmits through the glass substrate 10a and the wavelength selection film 10b and further through the retardation film 10c. 650n
The incident linearly polarized light of m is given a phase difference by the retardation film 10c to become elliptically polarized light, is then reflected by the total reflection film 10d and is transmitted through the retardation film 10c again. At this time, the retardation film 10c is further imparted with a retardation, and is imparted with a retardation of ¼ wavelength in total to become almost circularly polarized light. The circularly polarized light passes through the wavelength selection film 10b and goes toward the optical recording medium 8.

With the configuration of this embodiment, 650n
It is possible to give a phase difference of ¼ wavelength to the light of wavelength m, whereby the light utilization efficiency can be improved. On the other hand, since the phase difference is not given to the light having the wavelength of 780 nm, the light utilization efficiency does not increase, but the configuration using the non-polarization hologram can be adopted, and the cost can be reduced.

In this embodiment, the optical isolator configuration is applied to only one wavelength light of the two to give a phase difference of 1/4 wavelength, and the other wavelength light is not polarized. The parts can be diverted so that the cost can be reduced. The present embodiment can be applied to not only the above-mentioned optical element compatible with two wavelengths but also three wavelengths (or more). In this case, some wavelength light of the multiple wavelength light (especially one or multiple wavelength light on the short wavelength side)
On the other hand, a phase difference of ¼ wavelength may be given to make circularly polarized light, and other wavelength light may be reflected by the wavelength selection film and used.

(Embodiment 4) An embodiment corresponding to claim 12 This embodiment has a structure in which a beam shaping function is added to the structure of the optical element of the first embodiment. In other words, both the DVD and the CD integrate the two-wavelength compatible quarter-wave plate and the two-wavelength beam shaping prism in order to increase the light utilization efficiency. FIG. 6 is a diagram for explaining the configuration and operation in still another embodiment of the present invention, and is a diagram showing an optical element in which a beam shaping function is added to the configuration of the above-described first embodiment. In FIG. 6, 11 is an optical element, 11a is a glass substrate, 11b is a retardation film, 11c is a prism,
d is a total reflection film.

The optical element 11 has a glass substrate 11a, a retardation film 11b, a prism 11c and a total reflection film 11d. Since the configuration of the entire pickup can be applied to the configuration shown in FIGS. 1 and 2, the behavior of light in the optical element 11 will be described. In FIG. 6, a light source (6 in FIG.
65 emitted from 50 nm LD1 and 780 nm LD2)
The 0 nm light and the linearly polarized light of 780 nm are used for the glass substrate 11
The light is transmitted through the retardation film 11b through a. Retardation film 11b
Then, the incident linearly polarized light is given a phase difference to become elliptically polarized light. The elliptically polarized light then passes through the prism 11c, is reflected by the total reflection film 11d, and is transmitted through the retardation film 11b again. The reflected light is further given a phase difference by the retardation film 11b and becomes substantially circularly polarized light, and travels to the optical recording medium 8 shown in FIG.

The structure of the present embodiment is about 1 / about the incident light.
Regarding the point that the phase difference of 4 wavelengths is given, the above-mentioned Embodiment 1 is used.
However, by passing through the prism 11c, the incident beam is expanded in the minor axis direction to perform beam shaping. As a result, the amount of light irradiated onto the surface of the optical recording medium is increased by the isolator structure using the quarter-wave plate, and the light utilization efficiency can be further increased, and more light can be irradiated onto the surface of the optical recording medium. Therefore, higher speed recording can be achieved.

FIG. 15 is a diagram for explaining the above-mentioned beam shaping, in which 21 is a collimating lens and 22 is a collimating lens.
Is a first prism, and 23 is a second prism. In the optical pickup device, particularly in the case of a recording type, in order to increase the light utilization efficiency as much as possible, a collimator lens is arranged in the vicinity of the laser light source, or a collimator lens having a large NA is used.
Since the elliptical beam is emitted from the collimator lens, it is condensed by the objective lens to form an elliptical spot on the optical recording medium. Therefore, beam shaping is necessary to make the elliptical beam after the collimating lens circular.

That is, as shown in FIG. 15, the elliptical beam B ₁ emitted from the collimator lens can be shaped into a circular beam B ₂ having an isotropic intensity distribution by using an optical system such as a prism. . FIG. 15 shows two triangular prisms 22, 2 on the optical path after the collimating lens 21.
3 shows a configuration for arranging 3 to perform beam shaping. Here, two prisms are used to emit the light beam in the same direction as the incident light beam, but the beam can be shaped by one prism as in this embodiment.

In the first prism 22, between the incident angle θ ₁ , the refraction angle θ ₀ , the incident beam diameter D ₁ and the outgoing beam diameter D ₀ , D _P = D ₁ / sin (90−θ ₁ ). = D ₀ / sin (90-θ ₀ ) Therefore, D ₀ / D ₁ = cos θ ₀ / cos θ ₁ Equation 1 is established, and assuming that the refractive index of the prism is n, the relationship between θ ₁ and θ ₀ is Snell's According to the law, sin θ ₁ = n sin θ ₀ . At this time, assuming that the apex angle of the prism is α, α = θ _0. Therefore, the above-mentioned formula 1 is D ₀ / D ₁ = cos α / (1-n ² sin ² α) ^1/2 ... Therefore, the beam shaping optical system can be configured by designing and arranging the prism in consideration of the above expression 2. It should be noted that such beam shaping can be realized by combining cylindrical lenses, but it is easier to produce by using a prism.

By using the optical element having the beam shaping function as described above, the wavelength light for DVD and C
By beam-shaping the D wavelength light, it is possible to improve the light utilization efficiency of both wavelength lights and realize a multi-light pickup capable of high-speed recording. It is obvious that the configuration shown in FIG. 6 can be applied to the configuration in which the beam shaping function is added to the second embodiment.

(Fifth Embodiment: Corresponding to Claim 12) This embodiment describes an embodiment of an optical element having a beam shaping function similarly to the fourth embodiment. It has a configuration with a shaping function added. FIG. 7 is a diagram for explaining the configuration and operation of still another embodiment of the present invention, in which 12 is an optical element, 12a is a glass substrate, 12b is a wavelength selection film, 12c is a retardation film,
12d is an edge prism and 12e is a total reflection film. In the third embodiment, a phase difference of ¼ wavelength is given only to light of a specific wavelength for which the LD power is insufficient to form an optical isolator structure, and light of a wavelength for which the LD power is sufficiently secured is obtained. On the other hand, the example in which the optical isolator configuration is not used has been described. In the present embodiment, a beam shaping function is added to the above configuration.

That is, in this embodiment, the beam shaping is performed only on the light of the wavelength for which the LD power is insufficient to improve the light utilization efficiency. The optical element 12 shown in FIG. 7 is configured by arranging an edge prism 12d instead of the glass substrate 10e shown in FIG. The optical element 12 of this embodiment includes a glass substrate 12a and a wavelength selection film 12
b, a retardation film 12c, an edge prism 12d, and a total reflection film 12e.

The 780 nm wavelength light emitted from the light source (780 nm LD2 in FIG. 1) passes through the glass substrate 12a, is reflected by the wavelength selection film 12b, and travels toward the optical recording medium surface.
On the other hand, 6 emitted from the light source (650 nm LD1 in FIG. 1)
The 50 nm light passes through the glass substrate 12a and the wavelength selection film 1
2b and then the retardation film 12c. 65
The 0 nm linearly polarized light is given an optical phase difference by the retardation film 12c to become elliptically polarized light, then is reflected by the total reflection film 12e via the edge prism 12d and is transmitted through the retardation film 12c again. This reflected light is further given a phase difference by the retardation film 12c, becomes substantially circularly polarized light, passes through the wavelength selection film 12b, and travels toward the optical recording medium 8 in FIG. Edge prism 12d
Then, beam shaping is performed. Since the beam shaping function has been described in the fourth embodiment, its repeated description will be omitted.

According to the configuration of this embodiment as described above, 6
Since it is possible to give a phase difference of ¼ wavelength only to 50 nm light and perform beam shaping, it is possible to further improve the light utilization efficiency. Further, since the phase difference is not given to the 780 nm light, the light utilization efficiency does not increase, but the conventional parts can be applied as the configuration using the non-polarization hologram, and thus the cost can be reduced.

(Embodiment 6: Corresponding to claim 13) FIG.
FIG. 6 is a diagram for explaining the configuration and action of still another embodiment of the present invention, in which 11 is an optical element, 11a is a glass substrate, 11b is a retardation film, 11c is an edge prism, and 1c.
1d is a total reflection film, and X is an optical axis of the objective lens. The present embodiment shows a configuration in which the optical pickup device is thinned by using the optical element 11 of the fourth embodiment described in FIG. As described in the fourth embodiment, the optical element 11 gives a phase difference of ¼ wavelength to the corresponding wavelength light on the assumption that both DVD and CD are recorded or reproduced, and the objective lens 7 (see FIG. It also has the function of a rising reflection mirror for making the light incident on 1), and further has a beam shaping function.

The optical element 11 has a glass substrate 11a, a retardation film 11b, an edge prism 11c and a total reflection film 11d. The edge prism 11c has a shape in which the incident side of light from the light source is thick and the emitting side to the objective lens 7 is thin. At this time, the normal line of the total reflection surface of the total reflection film 11 d is inclined by the angle β with respect to the optical axis X of the objective lens 7. In order for the light reflected by the total reflection surface to come out in parallel with the optical axis X of the objective lens, β must be a value smaller than 45 °. Also, the glass substrate 11a
Similarly, the inclination α between the normal line of the incident side surface and the optical axis X of the objective lens must be smaller than 45 °.

In the conventional rising reflection mirror, the angle formed by the normal line of the mirror surface and the optical axis X of the objective lens is 45 °, whereas the optics of the embodiment having the edge prism shape as described above. Since the angle of the element is inclined to a value smaller than 45 °, the thickness of the pickup in the height direction can be reduced without increasing the thickness of the pickup in the height direction.

On the contrary, as shown in FIG. 9, if the edge prism 11c has a thick emission side, the angle γ formed by the normal line of the total reflection surface of the total reflection film 11d and the optical axis of the objective lens is 4.
Since the value is larger than 5 °, the thickness of the pickup in the height direction cannot be reduced. That is, as in the present embodiment, by using a prism having a thin exit side to the objective lens 7, the thickness of the pickup can be reduced, which is suitable for mounting on a mobile computer such as a notebook computer.

The optical pickup device according to this embodiment is
By arranging the optical element so that its height is thinner than that of a normal rising reflection mirror, the normal line of the total reflection surface of the front reflection film and the optical axis of the objective lens are tilted so as to be smaller than 45 °. , It is possible to make the pickup thinner so that it can be easily applied to laptop computers and mobile devices.

(Embodiment 7: Corresponding to Claim 14) Embodiment 4
Also, in Example 6, the phase difference of ¼ wavelength is given to both of the two types of wavelength light, and the beam shaping is performed by the beam shaping prism. By using the chromatic aberration of the beam shaping prism when passing therethrough, even when the positions of the light emitting points at 650 nm and 780 nm are different, the optical axis and the incident angle can be made equal and incident on the objective lens. In recent years, one LD has been used to reduce the size of pickups.
A monolithic LD having two emission points of 650 nm and 780 nm on a chip and a pickup of a one-package configuration in which two LD chips are closely arranged in one package have been proposed.

FIG. 10 is a diagram for explaining an optical path relating to the arrangement of two light sources in the optical pickup device having the light source of the one package structure as described above.
When using the light source as described above, two light emitting points (65
Since 0 nm LD1 and 780 nm LD2) cannot be arranged on the optical axis Xc of the collimator lens 5 at the same time, both light emitting points are arranged at positions deviated from the optical axis Xc. In the case of the configuration as shown in FIG. 10, the optical path after the collimating lens 5 has the same wavelength for both wavelengths.
The optical axis Xc is not parallel to the optical axis Xc, and proceeds with an inclination. Therefore, as it is, the light is incident on the objective lens 7 (FIG. 1) with an inclination, so that a coma aberration occurs in the focused spot on the optical recording medium.

Therefore, in the present embodiment, the chromatic aberration of the prism 11c of the optical element 11 is used to make the optical axis of the light incident on the objective lens coincident with (or at least parallel to) the optical axis of the objective lens. To do. As shown in FIG. 10, by selecting the prism 11c of the optical element 11 and the material of the glass substrate 11a to give optimum chromatic aberration, 650 nm
It is possible to make the incident optical axis of the two-wavelength light of 780 nm and the incident optical axis to the objective lens coincide with (or be parallel to) the optical axis of the objective lens. In this way, coma aberration does not occur in the focused spot on the optical recording medium.

According to the present embodiment, when the semiconductor laser is mounted in one package, even if the position of the light emitting point is different and the incident angle to the optical element is different, the optical element is used as the objective lens. By aligning (or at least making them parallel to) the incident optical axis of 1 and the optical axis of the objective lens, it is possible to suppress aberration and obtain a good spot. Also, since the optical axes are parallel even if the wavelengths are different, the movement amount of the actuator may be the same as that of a normal actuator, and the load on the actuator does not increase.

(Embodiment 8: Corresponding to Claim 15) FIG.
FIG. 8 is a diagram for explaining still another embodiment of the present invention. In this embodiment, in the optical pickup device shown in each of the above-mentioned embodiments, the shape of the optical element is defined in order to make the height direction of the drive device thin.
Specifically, as shown in FIG. 11, by processing the bottom surface and the top surface of the optical element 6 so as to be perpendicular (90 °) to the optical axis of the objective lens, it is possible to reduce the thickness of the optical pickup device. it can.

That is, when the upper glass substrate 6a, the retardation film 6b, the total reflection film 6c, and the lower glass substrate 6d are laminated, usually a laminated body having rectangular surfaces is obtained.
When this laminated body is used as the optical element 6, the optical element 6 is arranged obliquely in the optical pickup device. Therefore, the surface of the optical element 6 is ground in order to make the device thinner. As a result, the height when incorporated into the device is reduced. That is, by processing the optical element 6 so as to have a surface perpendicular to the optical axis of the objective lens, it is possible to reduce the thickness of the optical pickup, and thus it is possible to suitably correspond to a notebook computer or a mobile device. .

(Embodiment 9: Corresponding to claim 16) In order to increase the recording speed of the optical pickup device, the light amount of the main beam can be increased by adopting the one-beam tracking method rather than the three-beam tracking method. It is possible and advantageous. On the other hand, in the one-beam tracking method, a large offset occurs in the track signal when the objective lens is shifted, and the track cannot be detected correctly.
Therefore, the applicant has developed a mirror-integrated actuator that drives a mirror together with an objective lens.
A method has been proposed that is beam tracking and does not cause a large offset in the track signal (for example, Japanese Patent Laid-Open No. 09-180207).

In the method of Japanese Patent Laid-Open No. 09-180207, the light from the light source is reflected by the mirror and then guided to the objective lens.
There are many reflection surfaces for a total of two times, one for the return path and one for the return path. When circularly polarized light is incident on the reflecting surface, a phase difference occurs. Therefore, if linearly polarized light is incident on the reflecting surface in the optical path to the mirror of the mirror-integrated actuator, the phase difference can be suppressed. Therefore, as in the present invention, linearly polarized light is used in the optical path to the mirror in the mirror-integrated actuator, and converted to circularly polarized light by the rising reflection mirror section immediately before the objective lens, so that a phase difference appears even if there are many reflecting surfaces. The amount can be reduced.

For example, in the configuration shown in FIG. 12, the hologram unit 15 is not provided with a quarter wavelength plate, and linearly polarized light is propagated up to the mirror of the mirror-integrated actuator 13, and the rising mirror 12 is provided with the optical element of the present invention. By using it and converting it into circularly polarized light, the phase difference generated in the mirror can be suppressed. That is, by mounting the optical element according to the present invention on an actuator in which an objective lens and a mirror move integrally, track detection can be performed with one beam suitable for high-speed recording, and the phase difference generated by the mirror can be suppressed. As a result, good signal detection without signal deterioration can be performed.

(Example 10: Corresponding to claim 18) FIG.
FIG. 3 is a diagram for explaining an optical disc drive device according to the present invention, in which 30 is an optical disc drive device, 31 is a polarization hologram for two wavelengths, 32 is an achromatic lens for two wavelengths, 33 is a beam shaping prism for three wavelengths, Three
Reference numeral 4 is a movable mirror, 35 is an objective lens, 36 is a DVD disc, 37 is a CD diameter disc, and 38 is a broadband quarter-wavelength rising mirror according to the present invention. When the optical pickup device of the present invention is mounted on the optical disc drive device 30, since the two wavelengths are circularly polarized by the wide band 1/4 wavelength plate 38, the optical utilization efficiency of both wavelengths is increased and the optical disc drive device of high recording speed is realized. it can. Further, since the polarization of the light returning to the LD is also rotated, noise is reduced, and there is an advantage that a highly reliable recording / reproducing characteristic can be obtained. The optical pickup device shown in each of the above embodiments can detect signals with high sensitivity because the signal deterioration due to the phase difference can be suppressed to the minimum, and further, the light utilization efficiency is high and the thinning is possible. It is possible to realize an optical disk drive device suitable for an environment such as a drive device with a built-in personal computer, which can be carried around or used for a long time with limited electric power such as a battery.

[0088]

According to the optical element and the optical pickup device of the present invention, for example, in a pickup device compatible with a plurality of wavelengths, which can be used for both DVD and CD media,
It is possible to improve the light utilization efficiency and optimize the light for a plurality of wavelengths, which enables high-speed recording. Further, in the optical pickup device of the present invention, the expression of the phase difference can be minimized by converting the light into circularly polarized light immediately before the objective lens. Further, by combining the optical element having a broadband wavelength plate function with the rising reflection mirror, it is possible to realize a thinner device. The optical element is advantageous in reducing the cost of the pickup by stacking a plurality of organic films to reduce wavelength dispersion.

Also, for example, DV whose LD output is not sufficient
By giving a phase difference of ¼ wavelength only to specific wavelength light such as D wavelength light, the light utilization efficiency of the optical system of the specific wavelength light is increased, and conventional optical components of other wavelengths are used. It is possible to reduce the cost by making it possible to transfer. In addition, it is possible to divert the conventional component by providing only one of the above wavelengths as an optical isolator structure and providing a phase difference of ¼ wavelength, and not using polarization for the other wavelength, and it is possible to reduce the cost. .

Further, by beam-shaping light of a plurality of wavelengths to improve light utilization efficiency, a multi-light pickup capable of high speed recording can be realized. Alternatively, by beam shaping only specific wavelength light to improve light utilization efficiency and support high-speed recording, by not beam shaping other wavelength light, conventional parts can be diverted and cost can be reduced. become.

Also, by making the height of the optical element lower than that of a normal rising reflection mirror, the optical element is tilted so that the pickup can be made thin and easily compatible with a notebook computer or a mobile device. You can Further, even if the light emitting point position of the light source is different, the incident optical axis to the objective lens and the optical axis of the lens are made parallel to each other, whereby the aberration can be suppressed and a good spot can be obtained. Also,
By grinding the top and bottom surfaces of the optical element, the pickup can be made thinner, and it can be used for notebook computers and mobile devices.

By mounting the optical pickup device of the present invention on an actuator in which an objective lens and a mirror move integrally, track detection can be performed with one beam suitable for high-speed recording, and the phase difference generated by the mirror can be reduced. Therefore, it is possible to suppress the signal, and it is possible to perform excellent signal detection without signal deterioration.

Further, the optical disk drive device according to the present invention can realize the downsizing and the energy saving effect by mounting the optical pickup device of the present invention, and can be easily carried when applied to a portable drive device. And it can be played for a long time.

[Brief description of drawings]

FIG. 1 is a diagram for explaining a first embodiment of the present invention.

FIG. 2 shows the first embodiment shown in FIG.
It is a figure for demonstrating the effect | action of the emitted light from mLD.

FIG. 3 is a diagram for explaining a detailed configuration and action in one embodiment of the optical element according to the present invention.

FIG. 4 is a graph showing an example of the relationship between phase difference and signal strength.

FIG. 5 is a diagram for explaining the configuration and operation of still another embodiment of the present invention.

FIG. 6 is a diagram for explaining the configuration and operation in yet another embodiment of the present invention.

FIG. 7 is a diagram for explaining the configuration and operation of yet another embodiment of the present invention.

FIG. 8 is a diagram for explaining the configuration and operation of yet another embodiment of the present invention.

FIG. 9 is a diagram for explaining a comparative example in arrangement of beam shaping means.

FIG. 10 is a diagram for explaining an optical path relating to the arrangement of two light sources in an optical pickup device having a light source of one package configuration.

FIG. 11 is a diagram for explaining yet another embodiment of the present invention.

FIG. 12 is a diagram showing an example of an optical system when a pickup is downsized using a beam shaping prism.

FIG. 13 is a diagram for explaining the function of the quarter-wave plate used as the optical element of the present embodiment.

FIG. 14 is a diagram for explaining another function of the quarter-wave plate according to the present invention.

FIG. 15 is a diagram for explaining a beam shaping function applied to the present invention.

FIG. 16 is a diagram for explaining an optical disk drive device according to the present invention.

[Explanation of symbols]

1 ... 650 nm LD (semiconductor laser), 2 ... 780 nm
LD (semiconductor laser), 3 ... 1st hologram, 4 ... 2nd
Hologram, 5 ... Collimating lens (coupling lens), 6 ... Optical element, 6a ... Glass substrate, 6b ... Retardation film, 6c ... Total reflection film, 6d ... Lower glass substrate, 7 ... Objective lens, 8 ... Light Recording medium, 9 ... Light receiving element, 10 ... Optical element, 10a ... Glass substrate, 10b ... Wavelength selection film, 10
c ... Retardation film, 10d ... Total reflection film, 10e ... Glass substrate, 11 ... Optical element, 11a ... Glass substrate, 11b ... Retardation film, 11c ... Prism, 11d ... Total reflection film, 12 ...
Optical element, 12a ... Glass substrate, 12b ... Wavelength selection film,
12c ... Retardation film, 12d ... Edge prism, 12e ...
Total reflection film, 13 ... Mirror integrated actuator, 14 ...
Reflecting mirror, 15 ... Hologram unit, 15a ... 1 /
4 wavelength plate, 16 ... Objective lens, 17 ... Beam shaping prism, 18 ... Standing up reflection mirror, 21 ... Collimating lens, 22 ... First prism, 23 ... Second prism, 3
0 ... Optical disc drive device, 31 ... 2 wavelength compatible polarization hologram, 32 ... 2 wavelength compatible achromatic lens, 33 ... 3 wavelength beam shaping prism, 34 ... Movable mirror, 35 ... Objective lens, 36 ... DVD disk, 37 ... CD diameter Disk, 38 ... Broadband 1/4 wavelength rising mirror.

Continued front page    F-term (reference) 2H042 DA00 DA01 DA12 DE00                 2H049 BA07 BA42 BB03 BB42 BB43                       BB46 BB63 BC21 CA05 CA08                       CA09 CA20                 5D119 AA02 AA41 AA43 BA01 BB01                       BB04 EC45 EC47 FA05 FA08                       JA02 JA06 JA32 JA43 JA57                       LB05                 5D789 AA02 AA41 AA43 BA01 BB01                       BB04 EC45 EC47 FA05 FA08                       JA02 JA06 JA32 JA43 JA57                       LB05

Claims (18)

[Claims] 1. Broadband quarter wave plate means for giving a phase difference of a quarter wavelength for each wavelength light to all of the plurality of specific wavelength lights, and all for reflecting all of the plurality of specific wavelength lights. A reflecting means, wherein the incident light is acted on by the broadband ¼ wavelength plate and then reflected by the total reflection means, and the reflected light is incident on the broadband ¼ wavelength plate means again, An optical element configured to cause incident light to be emitted by being subjected to a total of two actions by the broadband ¼ wavelength plate means, wherein the broadband ¼ wavelength plate means has a wavelength that is wavelength-dependent in phase difference. By selecting and stacking a plurality of organic films having different dispersion characteristics, the wavelength dispersion of each organic film is compensated,
An optical element having a multi-layer organic film structure configured so as to impart a phase difference of ¼ wavelength to all of the plurality of specific wavelengths. 2. A function of providing a phase difference of ¼ wavelength only to at least a part of specific wavelength light among a plurality of specific wavelength lights, and the partial wavelength light of the plurality of specific wavelength lights. Other than the 1/4 wavelength, a 1/4 phase difference plate means having a function of giving a predetermined amount of phase difference other than the 1/4 wavelength, and a total reflection means for reflecting all of the plurality of specific wavelength lights are incident. After the light is acted on by the quarter-wave plate means, the light is reflected by the total reflection means, and the reflected light is incident on the quarter-wave plate means again, whereby the incident light is changed to the quarter-wave plate. An optical element characterized in that the optical element is configured to receive the action of a total of two times to be emitted. 3. A wavelength selective reflection means for reflecting a part of wavelength light of a plurality of specific wavelength light and transmitting other wavelength light,
1 with respect to the other wavelength light among the plurality of specific wavelength light
A quarter wavelength plate means for giving a phase difference of / 4 wavelength, and a total reflection means for reflecting at least the other wavelength light,
The incident light is separated by the wavelength selection means into reflected light of the part of the wavelength and transmitted light of the other wavelength, and the transmitted light is
After being acted on by the quarter-wave plate means, it is reflected by the total reflection means, and the reflected light again enters the quarter-wave plate means and is acted upon, and then is transmitted through the wavelength selecting means and emitted. An optical element characterized by being configured to: 4. A semiconductor laser capable of emitting light of a plurality of specific wavelengths, and an objective lens for converging light on the optical recording medium so as to irradiate a recording surface on the optical recording medium with a light flux from the semiconductor laser. It has an optical means having a coupling lens and a light receiving element for receiving a returning light flux when the light guided by the optical means is reflected by the recording surface, and records or reproduces information on the recording medium. In the optical pickup device having a function, the optical pickup device includes wideband quarter-wave plate means for providing a phase difference of a quarter wavelength for each wavelength light to all of the plurality of specific wavelength lights, An optical element having a total reflection means for reflecting all the specific wavelength light of the optical element, the optical element being arranged on the optical path between the objective lens and the coupling lens. Pickup device. 5. The optical pickup device according to claim 4, wherein the broadband quarter-wave plate means is composed of a multilayer organic film in which a plurality of organic films are stacked. 6. The optical pickup device according to claim 5, wherein the multilayer organic film of the wideband quarter-wave plate means comprises:
By selecting and stacking a plurality of organic films having different wavelength dispersion characteristics that are wavelength dependence of the phase difference, the wavelength dispersion of each of the organic films is compensated, and for all of the plurality of specific wavelength lights. An optical pickup device, characterized in that it is configured so as to impart a phase difference of ¼ wavelength. 7. The optical pickup device according to claim 5 or 6, wherein the multilayer organic film in the broadband quarter-wave plate means is formed of an organic film of polycarbonate, polyvinyl alcohol, or polymethylmethacrylate. An optical pickup device characterized by the above. 8. A semiconductor laser capable of emitting light of a plurality of specific wavelengths, and an objective lens for converging light on the optical recording medium to irradiate a recording surface of the optical recording medium with a light beam from the semiconductor laser. It has an optical means having a coupling lens and a light receiving element for receiving a returning light flux when the light guided by the optical means is reflected by the recording surface, and records or reproduces information on the recording medium. In the optical pickup device having a function, the optical pickup device has a function of giving a phase difference of ¼ wavelength only to at least a part of wavelengths of the plurality of specific wavelengths, and the plurality of specific wavelengths. Of the light, a quarter wave plate means having a function of giving a predetermined amount of phase difference other than the quarter wave to the light other than the partial wavelength light, and all of the plurality of specific wavelength lights are reflected. An optical pickup device comprising an optical element having total reflection means, the optical element being arranged on an optical path between an objective lens and a coupling lens. 9. The optical pickup device according to claim 8, wherein the part of the wavelength light that gives the phase difference of the quarter wavelength is one or a plurality of wavelengths on the short wavelength side of the plurality of specific wavelengths. An optical pick-up device having the same wavelength light. 10. A semiconductor laser capable of emitting light of a plurality of specific wavelengths, and an objective lens for converging light on the optical recording medium so as to irradiate a recording surface on the optical recording medium with a light flux from the semiconductor laser. It has an optical means having a coupling lens and a light receiving element for receiving a returning light flux when the light guided by the optical means is reflected by the recording surface, and records or reproduces information on the recording medium. In the optical pickup device having a function, the optical pickup device includes a wavelength selective reflection means for reflecting a part of wavelength light of the plurality of specific wavelength light and transmitting a light of another wavelength, and a plurality of the specific wavelength light. Among them, a phase difference of 1/4 wavelength is given to the other wavelength light transmitted through the wavelength selection means 1 /
An optical element having a four-wave plate means and a total reflection means for reflecting the other wavelength light is provided, and the optical element is provided on the optical path between the objective lens and the coupling lens for converging the light on the optical recording medium. An optical pickup device characterized by being arranged. 11. The optical pickup device according to claim 10, wherein the other wavelength light that gives the phase difference of the quarter wavelength is one of the plurality of specific wavelength lights on the short wavelength side.
Alternatively, the optical pickup device is characterized in that the light has a plurality of wavelengths. 12. The optical pickup device according to claim 4, wherein the optical element has a light speed shaping means for shaping an incident light flux. 13. The optical pickup device according to claim 12, wherein the optical element is inclined at an angle between the normal line of the incident surface of the optical element and the optical axis of the objective lens being smaller than 45 °. An optical pickup device characterized in that it is arranged as follows. 14. The optical pickup device according to claim 12 or 13, wherein at least the semiconductor lasers that emit light of the specific wavelengths are mounted in one package, and the optical element is incident. An optical pickup device characterized in that the optical axis of the emitted light of each wavelength light and the optical axis of the objective lens are at least parallel to each other. 15. The optical pickup device according to claim 4, wherein the optical element includes at least a surface that is at 90 ° with respect to the optical axis of the objective lens. Drive device. 16. The optical pickup device according to claim 4, wherein the optical element is between an objective lens that converges light on an optical recording medium and a mirror that is driven integrally with the objective lens. The optical pickup device is arranged on the optical path of the optical pickup device. 17. The optical pickup device according to claim 4, wherein the plurality of specific wavelength lights are lights having wavelengths of 650 nm and 780 nm. 18. An optical disk drive device comprising the optical pickup device according to claim 4. [000]