JPH0997444A - Optical pickup and optical pickup for phase transition type optical disk - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the cost of an optical pickup by forming holograms stepwise, thereby improving the diffraction efficiency of light in the respective holograms and making the utilization of a semiconductor laser of lower output possible. SOLUTION: An optical guide member 5 is formed into a rectangular parallelepiped shape and has plural slopes and holograms therein. This member has a function to project the light emitted from a light source 1 and to introduce the light returned from a recording medium to a photodetector 13. The hologram element is formed into a staircase shape (100a, 101a) in its section and has the constitution to use +1st order light as the light for signal detection. The depths T1, T2 of the holograms are specified to 200 to 400nm, more preferably 250 to 420nm. As a result, the diffraction efficiency of the +1st order light of the light by the respective holograms is improved. The utilization efficiency of the light is improved by using the signal and the fist order light as the light for signal detection. The utilization of the semiconductor laser of the lower output is made possible.

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 for recording or reproducing information on an optical disc, and an optical pickup for a phase change type optical disc.

[0002]

2. Description of the Related Art Conventionally, there has been a demand for miniaturization of an optical disc device which records and reproduces information by using a laser beam, and attempts have been made to miniaturize and reduce the weight of an optical pickup by reducing the number of optical components. It is being appreciated. Compact optical pickup
The reduction in weight is advantageous not only for downsizing the entire apparatus but also for improving performance such as shortening access time. In recent years, the use of hologram optical pickups has been mentioned as a means for reducing the size and weight of optical pickups, and some of them have been put to practical use.

[0003]

However, in the above conventional structure, the diffraction efficiency of the diffusion angle conversion hologram provided inside the light guide member is not so good, so that a sufficient amount of light is secured for recording. Therefore, a high output semiconductor laser has to be used as a light source. Therefore, the cost of the optical pickup is very high. Further, since the diffraction efficiency of the astigmatism generation hologram is not so good, the quality of the focus error signal and the track error signal is not so good, and the C / N ratio is not so large.

The present invention solves the above-mentioned problems. By forming holograms in a stepwise manner, the diffraction efficiency of light in each hologram is improved, thereby making it possible to use a semiconductor laser with a lower output, An object of the present invention is to provide a cost-effective optical pickup and an optical pickup for a phase-change type optical disc.

[0005]

To achieve this object, a light source and a plurality of inclined surfaces inclined with respect to the incident direction of light emitted from the light source are provided, and at least one of the inclined surfaces is provided. A light guide member that has a hologram on its surface, guides the light from the light source to the optical medium by reflecting the light from a plurality of inclined surfaces, and guides the light reflected from the optical medium to a predetermined position,
The hologram has a structure in which a light receiving unit that receives light and that converts the received optical signal into an electric signal is provided, and the hologram has a stepwise cross section. The depth of the hologram is 200 to 460 (nm), preferably 25.
It is set to 0 to 420 (nm), and + 1st order light is used as light for signal detection.

[0006]

With this configuration, the light in each hologram is +
The diffraction efficiency of the first-order light can be improved, and thus +1
By using the next light as the light for signal detection, the light utilization efficiency can be improved.

[0007]

The packaging of an optical pickup according to an embodiment of the present invention will be described below with reference to the drawings.

1 and 2 are sectional views showing a packaging structure of an optical pickup according to an embodiment of the present invention.

Reference numeral 1 denotes a light source. As the light source 1, various lasers such as a semiconductor laser and a gas laser such as He-Ne can be considered. Here, it is preferable to use a semiconductor laser which is the smallest among these, can reduce the size of the entire device, and has an output of several mW to several tens mW which is inexpensive. Semiconductor lasers made of AlGaAs, InGaAsP, I
nGaAlP, ZnSe, GaN, and the like are conceivable. Here, AlGaAs, which is most commonly used and is inexpensive, is used. Furthermore, when performing high-density recording, the spot diameter on the recording medium can be made smaller, and
It is preferable to use a semiconductor laser such as InGaAlP or ZnSe having a shorter wavelength than s.

2 is a submount, and the submount 2 is
Has a rectangular parallelepiped shape or a plate shape, and the light source is
1 is attached. This submount 2 is a light source 1
Along with mounting, it works to release the heat generated by the light source 1.
have. Heat is required to bond the submount 2 and the light source 1.
Considering the conductivity etc., Au-Sn, Sn-Pb, Sn-
A foil (thickness of several μm to several tens of μm) such as Pb-In is pressed at high temperature.
It is preferable to use the wearing method. Also, light source 1 and sub
If the mount 2 is not installed almost horizontally, the aberration of the optical system and
This may cause a decrease in coupling efficiency. Therefore, when joining
Source 1 is sub-mount 2 at a predetermined position and at a predetermined height with substantially water.
It is preferably mounted flat. Further sub-mount
The upper surface of the light source 2 should be in electrical contact with the lower surface of the light source 1.
An electrode surface 2a is provided. This electrode surface 2a is the light source 1
And a metal film that constitutes the electrode surface 2a.
In consideration of conductivity and corrosion resistance, use Au thin film.
And are preferred. Further, the submount 2 is generated by the light source 1.
Due to problems with heat and mounting with the light source 1, high thermal conductivity,
In addition, the coefficient of linear expansion is that of the light source 1 (about 6.5 × 10 ^-6/
A material close to ℃) is preferable. Specifically, the linear expansion coefficient is 3
~ 10 x 10^-6Thermal conductivity of 100 w / mK or more at / ° C
A substance such as AlN, SiC, T-cBN, Cu
/ W, Cu / Mo, Si etc., especially for high power laser
Thermal conductivity must be very high when
Sometimes it is preferable to use diamond or the like. light source
1 and submount 2 have the same or similar linear expansion coefficient.
Distortion between the light source 1 and the submount 2
Since it is possible to suppress the occurrence of
The mounting part with the module 2 comes off or the light source 1 is cracked.
Inconveniences, such as a problem, can be prevented. However the book
If it is out of the range, between the light source 1 and the submount 2
A large amount of distortion occurs, and the light source 1 and submount 2
The mounting part of may come off, or the light source 1 may crack.
Higher efficiency. Also, the thermal conductivity of the submount 2 can be
The heat generated by the light source 1
Can be efficiently released to the outside. However heat conduction
If the rate is below this limit, the heat generated by the light source 1
The temperature of the light source 1 rises and the light source 1
The output is reduced, the life of the light source 1 is shortened,
In case of, inconvenience such as destruction of the light source 1 occurs
Easier to do. In this embodiment, it is relatively inexpensive and these two
AlN, which is very excellent in both of the two characteristics, was used. Change
In addition, the upper surface of the submount 2 has a good bonding property with the light source 1.
In order to move from the submount 2 toward the light source 1, Ti,
It is preferable to form a thin film in the order of Pt and Au.

Reference numeral 3 is a block, and the block 3 is basically rectangular parallelepiped and has a large protrusion 3a on its side surface, and the submount 2 is attached to the upper surface thereof. Like the submount 2, the block 3 also has a high thermal conductivity and a material having a linear expansion coefficient close to that of the submount 2, for example, due to heat generated from the light source 1 and problems such as attachment to the submount 2. It is preferable to use Mo, Cu, Fe, Kovar, 42 alloy or the like other than those shown in the material examples of the submount 2. However, the requirements for these characteristic values are not so strict as compared with the submount 2, so that it is preferable to select them with emphasis on cost. Here, the block 3 is formed of a material such as Cu or Mo which is very inexpensive as compared with AlN and has relatively excellent characteristics. Further, in consideration of thermal conductivity and the like for joining the block 3 and the submount 2, Au-Sn, Sn-Pb, S, although slightly expensive, as in the case of the submount 2 and the light source 1.
It is preferable to press-bond a foil of n-Pb-In or the like (thickness: several μm to several tens of μm) at high temperature.

A heat radiating plate 4 serves to radiate the heat generated by the light source 1 and transmitted through the submount 2 and the block 3 by conduction to the outside.
Various members forming the optical pickup are mounted thereon, and serve as a packaging substrate. The heat radiating plate 4 is provided with a hole 4a for adjustment. Block 3 is brazed,
It is fixed to the upper surface of the heat sink 4 by solder foil or the like. Heat sink 4
Cu, Al, Fe, etc., which have high thermal conductivity, can be considered as the material of the.

The submount 2 and the block 3 are shown here.
Are formed separately, but when the output of the light source 1 is high and a higher thermal conductivity is required for these members, these members are integrally formed in order to improve the thermal conductivity. Is preferred. In this case, it is preferable to use those having extremely high thermal conductivity such as AlN.

It is desirable that the block 3 is larger than the submount 2 so that the contact area with the heat sink 4 is large.

Since the light source 1 is required to have high accuracy with respect to the optical axis, the upper surface of the submount 2 is preferably horizontal with high accuracy. Therefore, it is preferable to pay close attention to the mounting of the submount 2, the block 3, and the heat sink 4.

Reference numeral 5 denotes a light guide member. The light guide member 5 has a rectangular parallelepiped shape and has a plurality of slopes and various films formed on the slopes therein, and is emitted from the light source 1. The emitted light is emitted and the returned light is guided to a predetermined position. Also, the light guide member 5
Is adhered to the end surface portion 3b of the protrusion 3a of the block 3 on its side surface. The bonding material used for this purpose must have conditions such as high adhesive strength, workability that can be fixed at any moment, small changes in volume due to changes in volume before and after curing and changes in temperature and humidity, that is, low shrinkage. It is required, and by satisfying these, workability and stability of the joint surface can be improved. Here, a UV adhesive which is instantly cured by irradiating ultraviolet rays is used as such a bonding material.
Further, a moisture-absorbing and curing instant adhesive may be used. It is preferable that the contact area (S) between the block 3 and the light guide member 5 is S> 1 mm ² in order to have a sufficient mounting strength.

Reference numeral 13 is a light receiving element, and the light receiving element 13 is composed of various electric circuits formed on a plate-shaped semiconductor wafer, and is attached to the bottom surface of the light guide member 5. At the time of attachment, the position is adjusted using the holes 4 a provided in the heat sink 4. Regarding the attachment of the light receiving element 13 and the light guide member 5, a large adhesive strength, workability that can be fixed at any moment, change in volume before and after curing, temperature and
Conditions such as a small change in volume due to humidity, that is, a low shrinkage ratio are required. By satisfying these conditions, workability and stability of the joint surface are improved. As such a bonding material, a UV adhesive having particularly good workability was used because it is instantaneously cured by irradiating ultraviolet rays. Note that a moisture-absorbing-curing instant adhesive may be used. The light receiving element 13 has a plurality of light receiving portions for receiving the light signal emitted from the light source 1 and reflected by the light guide member 5 and the recording medium and returned. The light signal detected by the light receiving unit is converted into an electric signal according to the light amount. This electric signal has the magnitude of the current value at the beginning of the conversion. However, this current has the disadvantages that it is very weak and that noise is easily picked up.
For this reason, it is preferable here to use, as the light receiving element 13, an element formed with an IV amplifier having a function of converting a current value to a correlated voltage value and amplifying it. However, it is required that the response of the output voltage be good with respect to the incident frequency of light. Further, on the surface of the light receiving element 13, there are provided a plurality of electrodes 13a made of a thin film of Al or the like for extracting the received information as a signal.

14 is a package, and the package 14 is
On the upper surface of the heat radiating plate 4, the above-described block 3 and the light guide member 5,
It is provided so as to surround the light receiving element 13 and the like, and a lead frame 14a used for extracting an electric signal from the light receiving element 13, supplying power to the light source 1, and the like is molded therein. The shape of the package 14 is a rectangular parallelepiped shape with a hollow central portion.
The step 14 is formed on the inner surface of the package 14 on the side where the mold 4a is molded so as to expose the legs 14b of the lead frame.
c is provided. Note that the shape of the package 14 may be a cylindrical shape or the like. Then, the legs 14b of the lead frame exposed on the steps 14c provided on the package 14 for extracting an electric signal from the light receiving element 13
And a plurality of electrodes 13 provided on the surface of the light receiving element 13
a is connected by wire bonding with a wire 14d made of Au, Al, or the like. In order to supply power to the light source 1, the upper surface of the light source 1 and the leg 14 b of the lead frame exposed on the step 14 c provided on the package 14 are bonded by wires 14 d, and
The electrode surface 2a provided on the upper surface of the light source 1 so as to be in electrical contact with the lower surface of the light source 1 and the leg 14b of the lead frame exposed on the step 14c provided on the package 14 are also wire-bonded with the wire 14d. By connecting. The material of the package 14 is required to be excellent in low water absorption, low outgassing, and the like. Here, a thermosetting resin such as an epoxy resin, which is the most common, is used as the IC mold. As the material of the lead frame 14a, a metal such as Cu, 42 alloy or Fe plated with Ag or Au is often used. Here, Cu plated with Ni and Au plated thereon was used. Further, for attachment between the package 14 and the heat radiating plate 4, a bonding material having properties such as high adhesive strength, low water absorption, and high airtightness (low leak characteristics) is used. As a result, the stability of the bonding surface and bonding position can be improved, and impurities can be prevented from entering the inside of the packaging of the optical pickup. Here, an inexpensive epoxy adhesive excellent in these characteristics was used.

Reference numeral 15 denotes a shell, and the shell 15 also has an outer shape like a hollowed-out rectangular parallelepiped like the package 14, and its horizontal cross section is substantially the same as that of the package 14. . The material is required to have characteristics such as low water absorption and low outgassing in order to prevent impurities from being mixed into the interior of the packaging. Here, polybutylene terephthalate (hereinafter referred to as PBT) having excellent properties is used. However, in particular, when characteristics excellent in strength, dimensional accuracy, and the like are required, an LCP that is more expensive than PBT but has these characteristics may be used. And the adhesion between the shell 15 and the package 14 is
An epoxy adhesive was used for the same reason as the attachment of the package 14 and the heat sink 4 described above. This shell 1
Instead of using 5, the height of the side wall portion of the package 14 may be made higher than that of the light guide member 5 for substitution.

Reference numeral 16 is a cover member, and the cover member 16 prevents dust and dirt from adhering to the light guide member 5, the light receiving element 13 and the like, and is attached to the upper surface of the shell 15 with an epoxy adhesive. ing. Further, as the material of the cover member 16, it is preferable to use glass such as BK-7 or Kovar glass. Furthermore, the cover member 1
It is preferable to form an antireflection film 16a on both upper and lower surfaces of 6 to prevent reflection. This antireflection film 16a is made of Mg
It is preferably formed of a material such as F ₂ .

As for the positional relationship between the cover member 16 and the light guide member 5, it is considered that the cover member 16 and the light guide member 5 are in contact with each other and a space is provided between them. When the two are brought into contact, the light guide member 5 is attached to the bottom of the cover member 16 with an epoxy-based adhesive or a UV adhesive. At this time, the thickness (t1) of the cover member 16 is set to 0.3 ≦ t1 ≦ 3.0 (m
m) is preferable. The reason for this is that if the lower limit is made thinner than this, the cover member 16 may not be able to withstand the weight of the light guide member 5 or the like attached thereto or the tension when the adhesive is hardened, and may be damaged. Regarding the upper limit, since the cover member 16 has a larger refractive index than air, a converging action is generated on the light and the light does not spread. As a result, the cover member 16 and the collimator lens (in the case of an infinite optical system) or the objective lens (In the case of a finite optical system), you have to increase the distance from
This is because it is disadvantageous in downsizing the pickup unit. By using such a configuration, the height of the optical pickup can be further reduced, and the pickup unit can be downsized while maintaining sufficient mounting strength.

On the other hand, when a space is provided between the two, the thickness (t2) of the cover member 16 is set to 0.1≤t2≤.
3.0 (mm), and the distance (d) between the cover member 16 and the light guide member 5 is also preferably 0.1 ≦ d ≦ 3.0 (mm). The reason for this is that the lower limit of t2 is different from the previous example in that the light guide member 5 is not attached, and it is only necessary to withstand external factors such as vibration. Also, as for d, the smaller the better, the better. However, there is a possibility that the accuracy error during assembly cannot be reduced to 0.1 mm or less. In this case, the cover member 16 comes into contact with the light guide member 5 during assembly and breaks. There is a risk that it will. By using such a configuration, the block 3 or the submount 2 is brought into thermal contact with another member while improving the relative positional accuracy between the light guide member 5 and the light source 1, the submount 2, and the block 3. Therefore, the heat generated in the light source 1 can be easily released to the outside.

Inside the optical pickup, the light source 1 and the light receiving element 13 are prevented from being oxidized and the light guide member 5 and the cover member 1 are provided.
6, gas such as N ₂ or Ar, N
It is preferable to fill an inert gas such as e or He. In this case, the gap 17 existing between the heat radiating plate 4 and the light receiving element 13 is filled with a bonding material having characteristics such as a small shrinkage ratio, low water absorption, and high airtightness (excellent leak characteristics), for example, an epoxy potting agent. It is necessary to fill with solder or solder. Thereby, the inside airtightness can be improved.

By using the configuration shown above,
The heat generated by the light source 1 can be easily released to the outside, and the antioxidant gas can be easily sealed by providing a total of two openings on both end surfaces of the packaging. Further, in the optical system, the relative positional relationship between the light source 1, the light guide member 5, and the light receiving element 13 can be correctly and firmly maintained. do not do.

The thermal resistance of the entire packaging of this optical pickup is preferably 35 ° C./w or less because heat can be more efficiently released to the outside of the package. Next, the operation of the optical pickup according to the embodiment of the present invention will be described with reference to the drawings. FIG. 3 is a conceptual diagram of the operation of the optical pickup in one embodiment of the present invention,
FIG. 4 is a perspective view of a light guide member according to an embodiment of the present invention.

In FIGS. 3 and 4, the laser light emitted horizontally from the light source 1 mounted horizontally on the heat sink 4 via the submount 2 and the block 3 has a plurality of parallel inclined surfaces. 5 is incident on the light guide member 5 from the surface 5f and is formed on the second slope 5b of the light guide member 5 and converts the diffusion angle of the emitted light with respect to the diffusion angle of the incident light (hereinafter NA is converted. Then, the reflection type diffusion angle conversion hologram 7 having a function is reached. The light whose NA has been converted and reflected by the diffusion angle conversion hologram 7 is reflected by the reflection type diffraction grating 6 formed on the first slope 5a as a 0th-order diffracted light (hereinafter referred to as a main beam) and ± 1st-order diffracted light (hereinafter referred to as a side beam). ). The main beam and side beam generated by the diffraction grating 6 are incident on a first polarization-selective beam splitter film 9 (hereinafter simply referred to as a first beam splitter film). The first beam splitter film 9 is a light having a vibration component parallel to the incident surface (hereinafter simply referred to as a P-polarized component).
And has a constant reflectance with respect to a vertical vibration component (hereinafter simply referred to as S-polarized component). Of the light that enters the first beam splitter film 9, the light that passes through the first beam splitter film 9 is used as the monitor light of the light emitted from the light source 1. Further, the main beam and side beam linearly polarized into the S-polarized light component reflected by the first beam splitter film 9 are:
The light passes through the surface 5 e of the light guide member 5 and the cover member 16, enters the objective lens 26, and is focused on the recording medium surface 27 a of the recording medium 27 by the light condensing action of the objective lens 26. At this time, the beam spots 29a and 29c of the two side beams are imaged on the recording medium surface 27a at positions substantially symmetrical with respect to the beam spot 29b of the main beam. Information is recorded or reproduced by the beam spots 29b, 29a of the side beam and the beam spot 29c of the main beam on the recording medium surface 27a, and tracking and focusing, so-called servo signals are read.

The divergence angle conversion hologram 7 corresponds to the divergence angle conversion hologram 7 with respect to the divergence angle of the light beam of the light emitted from the light source 1 that can enter the divergence angle conversion hologram 7.
The angle of diffusion of the light reflected from the object is converted. Further, the light can be converted into parallel light having no diffusion angle by the diffusion angle conversion hologram 7. Also, the same diffusion angle conversion hologram 7
Thus, as shown in FIG. 3, the light flux emitted from the light guide member 5 becomes an ideal spherical wave 30 from which the wavefront aberration accumulated in the midway path is removed. Therefore, the incident light on the objective lens 26 becomes an ideal spherical wave 30, and the beam spots 29 a, 29 b, 29 on the recording medium 27 by the objective lens 26.
c is narrowed down to the diffraction limit and has an ideal size, and information can be recorded or reproduced easily.

The return light of the main beam and the side beam reflected by the information recording surface 27a of the recording medium 27 passes through the objective lens 26 and the surface 5e of the light guide member 5 again,
The light enters the first beam splitter film 9 formed on the second slope 5b of the light guide member 5.

Of the returned light from the recording medium 27, the light transmitted from the first beam splitter film 9 is the light guide member 5.
A second polarization-selective beam splitter film 11 formed on a third slope 5c parallel to the first slope 5a of FIG.
(Hereinafter simply referred to as a second beam splitter film). The second beam splitter film 11 is similar to the first beam splitter film 9 in that the P beam component is almost 10
It has a transmittance of 0% and a constant reflectance for the S-polarized light component.

Here, the transmitted light 117 of the light flux incident on the second beam splitter film 11 will be described. The transmitted light 117 enters the polarization plane conversion substrate 31 laminated on the third inclined surface 5c.

FIG. 5 is a perspective view of a polarization plane conversion substrate according to one embodiment of the present invention, and FIG. 6 is a diagram showing the arrangement of light receiving portions and signal processing of an optical pickup according to one embodiment of the present invention.
The polarization plane conversion substrate 31 includes a first other slope 31a (hereinafter simply referred to as a first other slope) and a second other slope 31b (hereinafter simply referred to as a second other slope) substantially parallel to the first other slope 31a. ), The reflection film 126 is provided on the first other slope 31a,
The polarization separation film 12 is formed on each of the second other inclined surfaces 31b. The transmitted light 117 enters the polarization splitting film 12 formed on the second other slope 31b. The second other inclined surface 31b is formed so that the angle formed by the polarization plane 117a of the transmitted light 117 and the incident surface 128 is approximately 45 × (2n + 1) °: (n is an integer). As a result, the P-polarized component 117 of the transmitted light 117
The p and S polarization components 117s have an intensity ratio of approximately 1: 1. The P polarization component 117p having a polarization component parallel to the incident surface 128 is almost 100% due to the polarization separation film 12.
On the other hand, the S-polarized component 117s having a polarization component perpendicular to the incident surface 128 is reflected by the polarization separation film 12 on the second other inclined surface 31b by about 100% and is incident on the first other inclined surface 31a surface to form a reflection film. It is reflected by 126 and guided to the light receiving element 13. P deflection component 117p guided to the light receiving element 13
To the light receiving section 170, and the S-polarized component 117s also reaches the light receiving section 171 to create an RF signal.

Next, the reflected light 123 of the light beam incident on the second beam splitter film 11 shown in FIG. 3 will be described. The reflected light 123 is incident on the astigmatism generating hologram 10 formed by a reflection type hologram on the second inclined surface 5b. The reflected light 123 generates astigmatism by the astigmatism generation hologram 10 and is further reflected by the reflecting films 124 and 125, and the return light of the main beam is transmitted to the light receiving section 172 on the light receiving element 13 to the side beam. The return light of arrives at the light receiving portions 176 and 177 on the light receiving element 13.

Next, in one embodiment of the present invention, the structure of an optical pickup particularly adapted to a phase change type optical disk will be described with reference to the drawings. Phase-change optical discs record information by irradiating light to change the crystal structure in the recording medium, and require more light than conventional optical recording / reproducing devices to change the crystal structure. Therefore, a more efficient optical system is required. FIG. 7 is a configuration diagram of an optical pickup for a phase change type optical disc in one embodiment of the present invention. Note that members having the same numbers as those shown in FIGS. 1, 2 and 3 have the same functions and configurations, and thus description thereof will be omitted.

The laser light emitted from the light source 1 enters the light guide member 41 from the surface 41f of the light guide member 41 having a plurality of parallel inclined surfaces, and the diffusion angle conversion hologram 7, the diffraction grating 6 and the polarization selective light. A certain beam splitter film 3
5 (hereinafter, referred to as a beam splitter film), and is emitted from the surface 41 e of the light guide member 41. Unlike the embodiment shown in FIG. 3, the beam splitter film 35 has an S-polarized component reflectance of 95% or more and a P-polarized component reflectance of about 1%. Beam splitter film 35
The light that is transmitted through the beam splitter film 35 (about several percent of the total amount of light in the P-polarized component) of the light that is incident on is used as the monitor light of the light emitted from the light source 1. The light emitted from the surface 41e of the light guide member 41 is covered by the cover member 1
6 passes through the λ / 4 plate 33. FIG. 8 is a schematic view of a λ / 4 plate in one embodiment of the present invention. The λ / 4 plate 33 is provided with respect to the plane of polarization of the incident light from the light guide member 41.
The extraordinary optical axis 616 is installed in the direction of π / 4 · (2m−1); (m is a natural number: the same applies hereinafter), and the phase difference between the extraordinary optical component and the ordinary optical component of the incident light is π / 2 ·. (2m-
It has the function of generating only 1). Generally, a uniaxial crystal material is used as a material forming the λ / 4 plate 33.
Among them, it is preferable to use quartz which is low in cost and excellent in light transmittance. In uniaxial crystals have abnormal optical axis 616 and ordinary light axis 617, and has a different refractive index, called extraordinary refractive index n _e and ordinary index n _o for each of the optical axes. Since the optical distances of extraordinary light and ordinary light are different, λ /
Assuming that the substrate thickness of the four plate 33 is QD and the incident light wavelength is λ, a phase difference Δ determined by the following relational expression occurs. The thickness QD of the λ / 4 plate 33 is determined so that the phase difference Δ is π / 2 · (2m−1).

Δ = 2π · (n _e −n _o ) · QD / λ In this embodiment, the wavelength λ = 790 nm and the extraordinary light refractive index n _e
= 1.5477, the ordinary refractive index n _o = 1.5388 (provided that the refractive index varies in cut angle of the substrate. Cut parallel here a plane containing both the axis of the extraordinary light axis 616 and the ordinary axis 617.) Under the above condition, the substrate thickness of the λ / 4 plate 33 is 21.9 · (2m−1) μm. By setting such conditions, it is possible to convert linearly polarized light that is incident at an incident angle of 0 degree into circularly polarized light. That is, the linearly polarized light including only the S-polarized component emitted from the light source 1 can be converted into circularly polarized light. Note that here, the λ / 4 plate 33
As a result, a crystal of 21.9 μm was provided on the cover member 16, but the surface 41e of the light guide member 41 and the objective lens 26
In some cases.

The light that has been circularly polarized after passing through the λ / 4 plate 33 enters the objective lens 26 and is focused on the recording medium surface 27a of the recording medium 27 by the condensing action of the objective lens 26.
Is reflected. The rotation direction of the circularly polarized light reflected by the recording medium surface 27a is reversed, so that when the return light passes through the objective lens 26 and again through the λ / 4 plate 33, P
It is converted into linearly polarized light containing only the polarized component. The return light converted in this way again passes through the surface 41e of the light guide member 41 and again enters the beam splitter film 35 formed on the second inclined surface 41b of the light guide member 41. As described above, the beam splitter film 35 has a transmittance of about 100% for the P-polarized component and a reflectance of about 100% for the S-polarized component. Therefore, the return light having only the P-polarized component is almost transmitted through the beam splitter film 35.

Then, the returned light is incident on the half mirror 34 formed on the third slope 41c parallel to the first slope 41a of the light guide member 41. The half mirror 34 has a function of reflecting a predetermined amount of the incident light and transmitting the rest.

FIG. 9 is a layout view of a light receiving portion provided in a light receiving element of an optical pickup for a phase change type optical disk in one embodiment of the present invention. Here, of the light fluxes incident on the half mirror 34, the transmitted light 117 is guided to the light receiving portion 37 provided on the light receiving element 36.

Next, the reflected light 123 of the light beam incident on the half mirror 34 shown in FIG. 3 will be described. The reflected light 123 is incident on the astigmatism generating hologram 10 formed of a reflection type hologram on the second inclined surface 41b. The reflected light 123 generates astigmatism by the astigmatism generation hologram 10 and is further reflected by the reflecting films 124 and 125, and the return light of the main beam is transmitted to the light receiving portion 38 on the light receiving element 36 and the side beam. Of the return light reaches the light receiving portions 39 and 40 on the light receiving element 36.

In the optical pickup having the above-mentioned structure, the λ / 4 plate 33 is provided between the beam splitter film 35 and the recording medium 27, and the outgoing light, which is the linearly polarized light of the S-polarized component, is converted into circularly polarized light. The light reflected by the recording medium 27 is converted, and then the circularly polarized light, which is reflected by the recording medium 27 and whose rotation direction is reversed, is converted into linearly polarized light having only a P-polarized component and made incident on the beam splitter film 35. Of the S-polarized light component of the beam splitter film 35 can be significantly increased, and thus the amount of light with which the recording medium 27 is irradiated can be increased. . That is, the recording medium 27 can be efficiently irradiated with the limited output of the light source 1, and
The reflected light from the recording medium 27 can be efficiently guided to the light receiving element 37.

The light guide member in the two embodiments described above, that is, the light guide member 5 in the embodiment shown in FIG. 3 and the light guide member 41 in the embodiment shown in FIG. 7 are provided. Diffusing angle conversion hologram 7
Further, the astigmatism generation hologram 10 (hereinafter collectively referred to as hologram) will be described in more detail. Most of the light incident on the hologram (this light contains 0th-order light, ± 1st-order light, ± 2nd-order light, ...) Can be converted into desired light necessary for signal detection. Especially here +1
It is preferably converted into the next-order diffracted light.

Although it is ideal that these holograms have a saw-toothed cross-sectional shape, it is technically very difficult in reality, and even if they can be realized, the cost is very high. It becomes a product. Therefore, in the present embodiment, the cross-sectional shape of the hologram is obtained at a low cost and with sufficient performance, and the grating portion is stepped as shown in FIGS. Here, FIG. 10 is a sectional view of a four-step hologram in one embodiment of the present invention, and FIG. 11 is a sectional view of an eight-step hologram in one embodiment of the present invention. In the hologram having such a shape, the + 1st order light can be generated most as the ratio of the light component in the diffracted light. Therefore, by using the + 1st order light as the signal detection light, the ratio of the signal detection light amount to the incident light amount, that is, the light utilization efficiency can be maximized. Therefore, even when a semiconductor laser having a small output, that is, a small amount of emitted light is used, a sufficient amount of light can be easily guided to the optical medium, and the light for signal detection is +1.
It is preferable to use the next light.

Further, the larger the number of steps of the steps forming this hologram, the closer to the ideal shape (sawtooth shape), but the diffraction efficiency (incident light) of the + 1st order light hologram actually used for signal detection. +1 out of the hologram
The rate of the next light does not change so much in the most efficient region, no matter how many stages are used. That is, even if the number of stages is increased, the light amount of the signal detection light guided to the optical medium does not change so much. Therefore, here, it is preferable to use a hologram having four or eight steps, which can reduce the number of steps for forming the hologram and can reduce the cost and make the performance of the optical pickup sufficient.

With respect to the diffusion angle conversion hologram 7 and the astigmatism generation hologram 10 having such a shape and having four steps, light is incident on the hologram at an incident angle of about 45 °, and the hologram is formed. The ratio of the amount of the + 1st order diffracted light to the total amount of the reflected diffracted light, that is, the relationship between the diffraction efficiency of the 1st order diffracted light in the hologram and the depth of the hologram is as shown in FIG. However, at this time, the total width of the steps of the hologram, that is, the pitch (Λ) is 10
λ (λ is the wavelength of incident light). As is clear from FIG. 12, the hologram depth (T1) is 200 to 3
A diffraction efficiency of 60% or more can be obtained in the range of 70 (nm), and a diffraction efficiency of approximately 70% or more can be obtained in the range of T1 of 250 to 300 (nm). Further, FIG. 13 shows changes in diffraction efficiency with respect to pitch (Λ) / wavelength of light (λ). As is clear from FIG. 13, a diffraction efficiency of 70% or more can be obtained when the pitch is 6λ or more, and a diffraction efficiency of 75% or more can be obtained when the pitch is 9λ or more. Therefore, in a hologram having a stepped structure, the hologram depth (T1) is 20
0 ≦ T1 ≦ 370 (nm), pitch (Λ) is Λ ≧ 6λ,
More preferably 250 ≦ T1 ≦ 300 (nm), Λ ≧ 9
By setting λ, the light emitted from the light source 1 can be efficiently guided to the medium. As a result, even if the semiconductor laser used as the light source 1 has a low output, that is, an inexpensive one, the amount of light guided to the optical medium or the like can be sufficiently secured, so that the performance of the optical pickup is sufficient. In addition, the cost of the optical pickup can be reduced.

Next, a hologram having eight steps will be described. In this hologram, as is clear from FIG. 14, the hologram depth (T3) is 270 to 460.
A diffraction efficiency of 70% or more can be obtained in the range of (nm), and a diffraction efficiency of approximately 80% or more can be obtained in the range of 300 to 420 (nm). Further, FIG. 15 shows changes in diffraction efficiency with respect to pitch (Λ) / wavelength of light (λ). As is clear from FIG. 15, a diffraction efficiency of 80% or more can be obtained when the pitch is 6λ or more, and a diffraction efficiency of 85% or more can be obtained when the pitch is 9λ or more. Therefore, in a hologram having a stepped structure of 8 steps, the hologram depth (T3) is set to 27.
0 ≦ T3 ≦ 460 (nm), pitch (Λ) is Λ ≧ 6λ,
More preferably, 300 ≦ T3 ≦ 420 (nm), Λ ≧ 9
By setting λ, the light emitted from the light source 1 can be efficiently guided to the medium. Therefore, even if a semiconductor laser used as the light source 1 has a low output, that is, an inexpensive one, it is possible to secure a sufficient amount of light guided to the optical medium, etc. In addition, the cost of the optical pickup can be reduced.

Further, since the presence of fine irregularities on the surface of the hologram directly causes the generation of aberrations, it is preferable to perform processing while paying attention to the surface being as smooth as possible during step formation of the hologram. In this embodiment, it is preferable to set the surface roughness of the hologram to 5 (nm) or less, preferably 2 (nm) or less, because the occurrence of aberration can be suppressed. Thereby, the light diffracted by the hologram can be correctly guided to a predetermined position and a predetermined shape via the downstream optical member.

Further, regarding the hologram formed in the stepwise shape, the angle (θ1) formed by the side wall portion 100a and the step portion 101a and the angle (θ2) formed by the side wall portion 100b and the step portion 101b are obtuse angles, particularly 90 ° <. θ1 ≦ 100
It is preferable that the angle is 90 ° <θ2 ≦ 100 °. With such a configuration, light can be guided to the optical medium more efficiently, and therefore the performance of the optical pickup can be further improved.

[0048]

The present invention has a light source and a plurality of inclined surfaces inclined with respect to the incident direction of the light emitted from the light source, and at least one of the inclined surfaces has a hologram, Light is guided by a plurality of inclined surfaces to the optical medium, and the light reflected from the optical medium is guided to a predetermined position. The light guide member receives the light and converts the received optical signal into an electrical signal. The hologram is provided with a light receiving unit, a light source, a light guide member, and a housing member that houses the light receiving unit, and the hologram has a stepwise cross section, so that the diffraction efficiency of the + 1st order light in the hologram is improved. Since it can be increased, it improves the light utilization efficiency when used as light for signal detection, and ensures a sufficient amount of light guided to the optical medium even when using a light source with a smaller output. You Since it is, the optical pickup performance can be sufficient. The depth of the hologram is 200 to 460 (nm), preferably 25.
By setting 0 to 420 (nm), particularly good +1
The diffraction efficiency of the next light can be obtained.

[Brief description of drawings]

FIG. 1 is a sectional view showing a packaging structure of an optical pickup according to an embodiment of the present invention.

FIG. 2 is a sectional view showing a packaging structure of an optical pickup according to an embodiment of the present invention.

FIG. 3 is a conceptual diagram of the operation of the optical pickup according to the embodiment of the present invention.

FIG. 4 is a perspective view of a light guide member according to an embodiment of the present invention.

FIG. 5 is a perspective view of a polarization plane conversion substrate according to an embodiment of the present invention.

FIG. 6 is a diagram showing a light receiving unit arrangement and signal processing of an optical pickup according to an embodiment of the present invention.

FIG. 7 is a configuration diagram of an optical pickup for a phase-change optical disc according to an embodiment of the present invention.

FIG. 8 is a schematic view of a λ / 4 plate according to an embodiment of the present invention.

FIG. 9 is a layout view of a light receiving portion provided in a light receiving element of an optical pickup for a phase-change optical disc according to an embodiment of the present invention.

FIG. 10 is a cross-sectional view of a four-stage hologram according to an embodiment of the present invention.

FIG. 11 is a sectional view of an eight-step hologram according to an embodiment of the present invention.

FIG. 12 is a diagram showing the relationship between hologram depth and diffraction efficiency in a four-stage hologram according to an embodiment of the present invention.

FIG. 13 is a relational diagram of the diffraction efficiency with respect to the pitch in the four-step hologram of one embodiment of the present invention.

FIG. 14 is a diagram showing the relationship between the hologram depth and the diffraction efficiency in the 8-step hologram according to the embodiment of the present invention.

FIG. 15 is a relationship diagram of the diffraction efficiency with respect to the pitch in the 8-step hologram according to the embodiment of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 light source 2 submount 2a electrode surface 3 block 3a protrusion 3b end surface 4 heat sink 4a hole 5 light guide member 5a first slope 5b second slope 5c third slope 5e surface 5f surface 6 diffraction grating 7 diffusion angle Conversion hologram 9 First beam splitter film 10 Astigmatism generation hologram 11 Second beam splitter film 12 Polarization separation film 13 Light receiving element 13a Electrode 14 Package 14a Lead frame 14b Lead frame foot 14c Step 14d Wire 15 Shell 16 Cover member 16a Antireflection film 17 Gap 26 Objective lens 27 Recording medium 27a Recording medium surface 29a, 29b, 29c Beam spot 30 Ideal spherical wave 31 Polarization plane conversion substrate 31a First other slope 31b Second other slope 32 CCD 33 λ / 4 plate 34 Half Mirror 35 Bee Splitter film 36 Light receiving element 37, 38, 39, 40 Light receiving portion 41 Light guide member 41a First slope 41b Second slope 41c Third slope 41e Face 41f Face 100a, 100b Side wall 101a, 101b Step portion 117 Transmitted light 117a Polarization plane 117s S polarization component 117p P polarization component 123 Reflected light 124 Reflective film 125 Reflective film 126 Reflective film 128 Incident surface 170, 171, 172, 172a, 172b, 172
c, 172d, 176, 177 Light receiving part 616 Extraordinary optical axis 617 Ordinary optical axis θ1 Angle between side wall and step θ2 Angle between side wall and step

Claims (35)

[Claims] 1. A light source and a plurality of inclined surfaces inclined with respect to an incident direction of light emitted from the light source, and a hologram is provided on at least one surface of the inclined surface, and light from the light source is provided. An optical guide member that guides the light reflected from the plurality of inclined surfaces to the optical medium and guides the light reflected from the optical medium to a predetermined position, and a light receiving unit that receives the light and converts the received optical signal into an electrical signal. An optical pickup comprising: means, wherein the hologram has a stepwise cross-section, and the + 1st order light of the light diffracted by the hologram is used as signal detection light. 2. A light source, a light guide member having a plurality of inclined surfaces inclined with respect to an incident direction of light emitted from the light source, and a hologram provided on at least one surface of the inclined surfaces, And a light receiving means for receiving the received light and converting the received light signal into an electric signal, a housing member for housing the light source, the light guide member and the light receiving means and having an opening, and an opening of the housing member. A cover member, wherein the light guide member reflects the light from the light source on the plurality of inclined surfaces to guide the light to the optical medium through the cover member, and reflects the light from the optical medium through the cover member. The light is guided to the light receiving means, the cross section of the hologram is formed stepwise, and the + 1st order light of the light diffracted by the hologram is used as the light for signal detection. The optical pick-up to be. 3. A light source, and a holding member for holding the light source,
An optical guide member having a plurality of inclined surfaces that are inclined with respect to the incident direction of the light emitted from the light source, and a hologram on at least one of the inclined surfaces, and an optical signal that receives and receives light. A light receiving means for converting the light source to the electric signal, a storage member that stores the light source, the holding member, the light guide member, and the light receiving means, and an opening, and a cover member that covers the opening of the storage member. Prepare,
The light guide member reflects the light from the light source on the plurality of inclined surfaces and guides the light to the optical medium through the cover member, and the light receiving unit receives the light reflected from the optical medium through the cover member. In addition, the hologram has a stepwise cross-section, and the + 1st order light of the light diffracted by the hologram is used as signal detection light. 4. A light source and a plurality of inclined surfaces that are inclined with respect to an incident direction of light emitted from the light source, and at least one surface of the inclined surfaces is provided with a hologram, and the light from the light source is provided. An optical guide member that guides the light reflected from the plurality of inclined surfaces to the optical medium and guides the light reflected from the optical medium to a predetermined position, and a light receiving unit that receives the light and converts the received optical signal into an electrical signal. Means, a housing member for housing the light source, the light guide member, and the light receiving means,
A base on which the storage member is placed, the hologram has a stepwise cross-section, and + 1st order light of the light diffracted by the hologram is used as signal detection light. And an optical pickup. 5. A light source, a light guide member having a plurality of inclined surfaces inclined with respect to an incident direction of light emitted from the light source, and a light guide member having a hologram on at least one of the inclined surfaces, And a light receiving means for receiving the received light and converting the received light signal into an electric signal, a housing member for housing the light source, the light guide member and the light receiving means and having an opening, and an opening of the housing member. The light guide member includes a cover member and a base on which the storage member is placed, and the light guide member reflects the light from the light source on the plurality of inclined surfaces and guides the light to the optical medium through the cover member. The light reflected from the optical medium through a member is guided to the light receiving means, and further, the hologram has a stepwise cross section, and the + 1st order light of the light diffracted by the hologram is detected. An optical pickup which comprises using as the light use. 6. A light source, and a holding member for holding the light source,
An optical guide member having a plurality of inclined surfaces that are inclined with respect to the incident direction of the light emitted from the light source, and a hologram on at least one of the inclined surfaces, and an optical signal that receives and receives light. A light receiving means for converting into an electric signal, a light source, the holding member, the light guide member and the light receiving means, and a storage member having an opening, a base for mounting the storage member, and A cover member that covers the opening, wherein the light guide member reflects the light from the light source at the plurality of inclined surfaces and guides the light to the optical medium through the cover member, and the light through the cover member. Guide the light reflected from the medium to the light receiving means,
Further, the hologram has a stepwise cross section, and the + 1st order light of the light diffracted by the hologram is used as light for signal detection. 7. A light source and a holding member for holding the light source,
Light having a plurality of inclined surfaces inclined with respect to the incident direction of the light emitted from the light source, the plurality of inclined surfaces are arranged substantially parallel to each other, and various optical elements are formed on the plurality of inclined surfaces. A guide member, a light receiving unit for converting light transmitted through the light guide member into an electric signal, a connecting member for taking out the electric signal converted by the light receiving unit, the light source, the holding member, and the light guide member. An optical pickup comprising: a housing member that houses the light receiving means and the connection member and has an opening; and a cover member that covers the opening of the housing member, wherein at least one of the optical elements is a hologram. In addition, the hologram has a stepwise cross section, and the + 1st order light of the light diffracted by the hologram is used as the light for signal detection. The optical pick-up to be. 8. A light source, and a holding member for holding the light source,
Light having a plurality of inclined surfaces inclined with respect to the incident direction of the light emitted from the light source, the plurality of inclined surfaces are arranged substantially parallel to each other, and various optical elements are formed on the plurality of inclined surfaces. A guide member, a light receiving unit for converting light transmitted through the light guide member into an electric signal, a connecting member for taking out the electric signal converted by the light receiving unit, the light source, the holding member, and the light guide member. A storage member that stores the light receiving means and the connection member, and has an opening, and a cover member that covers the opening of the storage member,
An optical pickup having a base on which the storage member is mounted, wherein at least one of the optical elements is a hologram, and the hologram has a stepwise cross-section and is diffracted by the hologram. An optical pickup characterized by using + first-order light of the generated light as light for signal detection. 9. The height difference (d) between the most concave part and the most convex part of the hologram is 200 ≦ d ≦ 460 (nm), preferably 25.
9. The optical pickup according to claim 1, wherein the optical pickup is formed so that 0 ≦ d ≦ 420 (nm). 10. The optical pickup according to claim 1, wherein the number of steps of the steps of the hologram cross section is four. 11. The height difference (d) between the most concave portion and the most convex portion of the hologram is 200 ≦ d ≦ 370 (nm), preferably 2
The optical pickup according to claim 10, wherein the optical pickup has a thickness of 50 ≦ d ≦ 300 (nm). 12. The optical pickup according to claim 1, wherein the number of steps in the cross section of the hologram is eight. 13. The height difference (d) between the most concave portion and the most convex portion of the hologram is 270 ≦ d ≦ 460 (nm), preferably 3
13. The optical pickup according to claim 12, wherein the optical pickup has a thickness of 00 ≦ d ≦ 420 (nm). 14. The surface roughness of the step portion of the stepwise hologram is 5 (nm) or less, preferably 2 (nm) or less.
The optical pickup according to any one of 1. 15. The optical pickup according to claim 1, wherein an angle formed by the step portion and the side wall portion in the stepwise hologram is an obtuse angle. 16. A light source and a plurality of inclined surfaces that are inclined with respect to an incident direction of light emitted from the light source, and at least one of the inclined surfaces has a hologram, and the light from the light source is provided. An optical guide member that guides the light reflected from the plurality of inclined surfaces to the optical medium and guides the light reflected from the optical medium to a predetermined position, and a light receiving unit that receives the light and converts the received optical signal into an electrical signal. Means for the phase-change optical disc, wherein the hologram has a stepwise cross-section, and the + 1st order light of the light diffracted by the hologram is used as the light for signal detection. pick up. 17. A light source, a light guide member having a plurality of inclined surfaces inclined with respect to an incident direction of light emitted from the light source, and a hologram provided on at least one of the inclined surfaces, And a light receiving means for receiving the received light and converting the received light signal into an electric signal, a housing member for housing the light source, the light guide member and the light receiving means and having an opening, and an opening of the housing member. A cover member, wherein the light guide member reflects the light from the light source on the plurality of inclined surfaces to guide the light to the optical medium through the cover member, and reflects the light from the optical medium through the cover member. The light is guided to the light receiving means, and further, the hologram has a stepwise cross section, and among the lights diffracted by the hologram, the + 1st order light is used as the light for signal detection. An optical pickup for a phase-change optical disc to. 18. A hologram having a light source, a holding member for holding the light source, and a plurality of inclined surfaces inclined with respect to an incident direction of light emitted from the light source, and at least one of the inclined surfaces is a hologram. A light guide member, a light receiving means for receiving light and converting a received light signal into an electric signal, the light source, the holding member, the light guide member and the light receiving means, and an opening. A storage member having, and a cover member for covering the opening of the storage member,
The light guide member reflects the light from the light source on the plurality of inclined surfaces and guides the light to the optical medium through the cover member, and the light receiving unit receives the light reflected from the optical medium through the cover member. In addition, the hologram has a stepwise cross section, and the + 1st order light of the light diffracted by the hologram is used as light for signal detection. . 19. A light source and a plurality of inclined surfaces that are inclined with respect to an incident direction of light emitted from the light source, and at least one surface of the inclined surfaces is provided with a hologram, and the light from the light source is provided. An optical guide member that guides the light reflected from the plurality of inclined surfaces to the optical medium and guides the light reflected from the optical medium to a predetermined position, and a light receiving unit that receives the light and converts the received optical signal into an electrical signal. Means, a storage member for storing the light source, the light guide member, and the light receiving means, and a base on which the storage member is placed, the hologram having a stepwise cross section, and the hologram An optical pickup for a phase-change optical disc, characterized in that + 1st-order light of the light diffracted by is used as light for signal detection. 20. A light source, a light guide member having a plurality of inclined surfaces inclined with respect to an incident direction of light emitted from the light source, and a hologram provided on at least one surface of the inclined surfaces, And a light receiving means for receiving the received light and converting the received light signal into an electric signal, a housing member for housing the light source, the light guide member and the light receiving means and having an opening, and an opening of the housing member. A cover member,
The light guide member includes a base on which the storage member is mounted, the light guide member reflects the light from the light source on the plurality of inclined surfaces and guides the light to the optical medium through the cover member, and through the cover member. The light reflected from the optical medium is guided to the light receiving means, and further, the hologram has a stepwise cross section, and the + 1st order light of the light diffracted by the hologram is used as the light for signal detection. An optical pickup for a phase change type optical disc, which is characterized by: 21. A hologram having a light source, a holding member for holding the light source, and a plurality of inclined surfaces inclined with respect to an incident direction of light emitted from the light source, wherein at least one of the inclined surfaces is a hologram. A light guide member, a light receiving means for receiving light and converting a received light signal into an electric signal, the light source, the holding member, the light guide member and the light receiving means, and an opening. A storage member having, a base on which the storage member is placed, and a cover member that covers the opening of the storage member, the light guide member reflects the light from the light source on the plurality of inclined surfaces. The light is guided to the optical medium via the cover member, and the light reflected from the optical medium is guided to the light receiving means via the cover member, and further, the hologram has a stepwise cross section, and Out of the light diffracted by the program +
An optical pickup for a phase-change optical disc, characterized in that primary light is used as light for signal detection. 22. A light source, a holding member that holds the light source, and a plurality of inclined surfaces that are inclined with respect to the incident direction of light emitted from the light source, and the plurality of inclined surfaces are substantially parallel to each other. A light guide member having various optical elements formed on the plurality of inclined surfaces and arranged, a light receiving unit for converting light transmitted through the light guide member into an electric signal, and an electric signal converted by the light receiving unit. Connection member to take out,
An optical pickup including: a light source, the holding member, the light guide member, the light receiving means, and the connection member, and a storage member having an opening, and a cover member covering the opening of the storage member. And at least one of the optical elements is a hologram, and the hologram has a stepwise cross section, and the + 1st order light of the light diffracted by the hologram is used as signal detection light. An optical pickup for a phase change type optical disc, which is characterized by: 23. A light source, a holding member for holding the light source, and a plurality of inclined surfaces inclined with respect to an incident direction of light emitted from the light source, and the plurality of inclined surfaces are substantially parallel to each other. A light guide member having various optical elements formed on the plurality of inclined surfaces and arranged, a light receiving unit for converting light transmitted through the light guide member into an electric signal, and an electric signal converted by the light receiving unit. Connection member to take out,
The light source, the holding member, the light guide member, the light receiving means, and the connection member are stored, and a storage member having an opening, a cover member that covers the opening of the storage member, and the storage member are placed. An optical pickup including a base, wherein at least one of the optical elements is a hologram, and the hologram has a stepwise cross-section, and the light diffracted by the hologram is +1. An optical pickup for a phase-change optical disk, characterized in that the next light is used as light for signal detection. 24. A λ / 4 plate is provided between the light emitting surface of the light guide member and the optical medium, and the λ / 4 plate and the optical axis of the light are substantially perpendicular to each other. 20. An optical pickup for a phase change type optical disc as described in any one of 19 above. 25. A λ / 4 plate is provided between the light emitting surface of the light guide member and the optical medium, and the λ / 4 plate and the optical axis of the light are substantially perpendicular to each other. , 18, 20, 2
1. An optical pickup for a phase change type optical disc according to any one of 1, 22, 23. 26. An optical pickup for a phase-change optical disk according to claim 25, wherein a λ / 4 plate is provided on the cover member. 27. The reflected light from the optical medium is guided to the light receiving means through a light guiding means that transmits or reflects light at least one of.
An optical pickup for the described phase change optical disc. 28. The optical pickup according to claim 27, wherein the light guide means is a half mirror. 29. The height difference (d) between the most concave portion and the most convex portion of the hologram is set to 200 ≦ d ≦ 460 (nm), preferably 250 ≦ d ≦ 420. 16. An optical pickup for a phase change type optical disc according to any one of 16 to 28. 30. The hologram according to claim 16, wherein the number of stairs in the hologram cross section is four.
An optical pickup for the described phase change optical disc. 31. The height difference (d) between the most concave portion and the most convex portion of the hologram is set to 200 ≦ d ≦ 370 (nm), preferably 250 ≦ d ≦ 300 (nm). The optical pickup for a phase-change optical disk according to claim 30. 32. The hologram according to any one of claims 16 to 28, wherein the number of stairs in the cross section of the hologram is eight.
An optical pickup for the described phase change optical disc. 33. The height difference (d) between the most concave portion and the most convex portion of the hologram is set to 270 ≦ d ≦ 460 (nm), preferably 300 ≦ d ≦ 420 (nm). The optical pickup for a phase change type optical disc according to claim 32. 34. The surface roughness of the step portion of the stepwise hologram is 5 (nm) or less, preferably 2 (nm) or less.
3. An optical pickup for a phase change type optical disc as described in any one of 1. 35. An optical pickup for a phase-change optical disk according to claim 16, wherein an angle formed by the step portion and the step portion in the stepwise hologram is an obtuse angle.