JP3536485B2 - Optical pickup and optical guide member - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical pickup for recording or reproducing information on or from an optical element, an optical disc, or the like.
And an optical guide member used for the optical pickup .

[0002]

2. Description of the Related Art RF in the following conventional optical pickup
The formation of signals will be described. FIG. 11 is a conceptual diagram of a conventional optical pickup. Light emitted from the light source 1, Charles guiding the recording medium via the light guide member 505. The return light of the main beam and the side beam reflected by the information recording surface of the recording medium is the objective lens and the surface 5 of the light guide member 505.
05e, the second slope 50 of the light guide member 505.
First polarization beam splitter film 509 formed on 5b
Incident on. The first polarization beam splitter film 509 has a transmittance of almost 100% with respect to light having an oscillating component parallel to the incident surface (hereinafter simply referred to as P-polarized component),
It has a constant reflectance with respect to a vertical vibration component (hereinafter simply referred to as an S-polarized component).

Of the return light from the recording medium, the light transmitted through the first polarization beam splitter film 509 is the third slope 505 parallel to the first slope 505a of the light guide member 505.
It is incident on a second polarization beam splitter film 511 (hereinafter simply referred to as a second polarization beam splitter film) formed on c. The second polarization beam splitter film 511 has a transmittance of almost 100% for the P-polarized component and a constant reflectance for the S-polarized component similarly to the first polarization beam splitter film 509.

Here, the second polarization beam splitter film 51
The light 617 which is incident on the polarization plane conversion substrate 531 among the light fluxes which are incident on 1 will be described. Light 617 is on the third slope 5
The light is incident on the polarization plane conversion substrate 531 laminated on 05c.

FIG. 12 is a perspective view of a conventional polarization plane conversion substrate. The polarization plane conversion substrate 531 is the first other inclined surface 53.
1a (hereinafter simply referred to as the first other slope) and the first other slope 5
31a has a second other slope 531b (hereinafter simply referred to as a second other slope), a reflective film 626 is provided on the entire surface of the first other slope 531a, and a second other slope 531b is provided on the entire surface of the second other slope 531b. Polarization separation films 512 are formed respectively. Transmitted light 61
7 is incident on the polarization separation film 512 formed on the entire surface of the second other slope 531b. The second other slope 531b transmits the transmitted light 61.
The angle formed by the polarization plane 617a of No. 7 and the incidence plane 628 is approximately 45.
(2n + 1), (n is an integer). As a result, the P-polarized component 617p of the transmitted light 617 and S
The polarization component 617s comes to have an intensity ratio of about 1: 1. The P polarization component 617p having a polarization component parallel to the incidence plane 628 is transmitted by the polarization separation film 512 almost 100%, while the S polarization component 617s having a polarization component perpendicular to the incidence plane 528 is on the second other slope 531b. Polarization separation film 5
Approximately 100% of light is reflected by 12 and is incident on the surface of the first other slope 531a, reflected by the reflection film 626, and guided to the light receiving element 513.

[0006]

However, in the above-mentioned conventional configuration, the S-polarized light component 617s reflected by the polarization separation film 512 among the transmitted light 617 that has entered the polarization plane conversion substrate 531 is the same as that of the other one. The light is incident on the surface of the inclined surface 531a, is reflected by the reflection film 626 and is guided to the light receiving element 513. However, in the polarization plane conversion substrate 531, the polarization separation film 512 and the reflection film 626 form the first other slope 531a and the second other slope. Since it is formed on the entire surface of 531b, the S-polarized light component reflected by the reflection film 626 may enter the polarization separation film 512 again depending on the positional relationship between the reflection film 626 and the polarization separation film 512 at this time. The light receiving element 5
Since there was a possibility that the ratio of the amount of light of the S-polarized component and the amount of P-polarized component incident on 13 would not be 1: 1, the light reflected by the reflective film 626 and directed to the light receiving element 513 is again incident on the changed separation film 512. In order not to do so, the distance between the polarization separation film 512 and the reflection film 626 needs to be set to be considerably large.
Therefore, even if an attempt is made to reduce the size of the light guide member 505, there is a limit to the size reduction of the polarization plane conversion substrate 531 and it is very difficult.

The present invention solves the above-mentioned problems of the prior art, and is an optical pickup having an extremely small volume and capable of forming an RF signal with less noise, and an optical pickup thereof.
An object is to provide a light guide member used for an optical pickup .

[0008]

In order to achieve this object, a polarization splitting element for transmitting or reflecting light according to the polarization direction of the light is provided on the other inclined surface of the polarization plane conversion substrate. , A reflection means for guiding the light reflected by the polarization separation element to the light receiving means, and the other area has a first area where the polarization separation element is provided and a second area where the polarization separation element is not provided. In the polarization plane conversion substrate, which is formed, the light reflected by the first region is reflected by the reflecting means, passes through the second region, and enters the light receiving means. The size of the separation element is set smaller than the area of the first other slope. More preferably, the size of the reflection film formed on the second other slope is set smaller than the area of the second other slope.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION A light source and a plurality of slopes inclined with respect to an incident direction of light emitted from the light source, the plurality of slopes are arranged substantially parallel to each other, and various slopes are formed on the slopes. A light guide member forming an optical element and having another slope different in inclination from the plurality of slopes, a light receiving unit for converting light transmitted through the light guide member into an electric signal, and provided on the other slope. And a polarization splitting element that transmits or reflects light according to the polarization direction of the light, and by providing the polarization splitting element on a part of the other inclined surface, the light reflected by the polarization splitting element is It is possible to prevent the light from entering the polarization separation element and reduce the thickness of the light guide member.

Further, by providing the polarization separation element at the light incident portion and the peripheral portion of the other inclined surface, the thickness of the light guide member can be further efficiently reduced.

Further, the light source has a plurality of slopes inclined with respect to the incident direction of the light emitted from the light source, the plurality of slopes are arranged substantially parallel to each other, and various optical elements are provided on the plurality of slopes. A light guide member that is formed and has another slope different in inclination from the plurality of slopes, a light receiving unit that converts the light transmitted through the light guide member into an electric signal, and the other slope are provided on the slope. A polarization separation element that transmits or reflects light according to the polarization direction of light,
A first area where the polarization separation element is provided and a second area where the polarization separation element is not provided on the other slope surface; and a reflection means that guides the light reflected by the polarization separation element to the light receiving means. Two regions are formed, and the light reflected by the first region is reflected by the reflecting means, passes through the second region, and enters the light receiving means. It is possible to almost completely prevent the light reflected by the element from re-entering the polarization separation element and to reduce the thickness of the light guide member.

It has a light source and a plurality of slopes inclined with respect to the incident direction of the light emitted from the light source, the plurality of slopes are arranged substantially in parallel, and various optical elements are formed on the plurality of slopes. And a light guide member having a first other slope different in inclination from the plurality of slopes, and a second other slope arranged in a predetermined relationship with the first other slope, and the light guide member A light receiving means for converting the light transmitted through to an electric signal, a polarization separation element provided on the first other inclined surface for transmitting or reflecting the light according to the polarization direction of the light, and the second A reflecting means for guiding the light reflected by the polarization separation element to the light receiving means provided on the other slope,
A first region where the polarization separation element is provided and a second region where the polarization separation element is not provided are formed on the first other slope, and the second other slope is formed on the second slope. A third area provided with a reflection means and a fourth area not provided with the reflection means are formed, and incident light passes through the fourth area and enters the first area. ,
Since the light reflected by the first region is reflected by the third region and transmitted through the second region to enter the light receiving means, the light enters the first region. It is possible to prevent the amount of light that was previously reflected by the reflecting means from decreasing and at the same time almost completely prevent the light that was reflected by the polarization separation element from entering the polarization separation element again after being reflected by the reflection means. The thickness of the guide member can be reduced.

By providing the first and second slopes substantially parallel to each other, the light guide member can be easily formed.

The first region is provided in the light incident region on the first other slope and its peripheral portion, and the third region is reflected by the first region on the second other slope. By providing the light in the area where the light is incident and its peripheral portion, it is possible to prevent the light from being reflected by the reflecting means before the light is incident on the first area and reducing the amount of light, and being reflected by the polarization separation element. It is possible to almost completely prevent the light from being reflected by the reflecting means and then enter the polarization separation element again, and it is possible to further reduce the thickness of the light guide member.

The packaging of the optical pickup according to the 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 in size among them and can be downsized as a whole, and which has a low output of several mW to several tens of mW. The material of the semiconductor laser is AlGaAs, InGaAsP, I
nGaAlP, ZnSe, GaN, etc. are considered, and the most commonly used and cheap AlGaAs is used here. When performing high-density recording, the spot diameter on the recording medium can be made smaller.
It is preferable to use a semiconductor laser such as InGaAlP or ZnSe having a wavelength shorter 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 of Pb-In or the like (thickness of several μm to several tens of μm) 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.
It is possible to prevent inconveniences such as occurrences. 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 the present embodiment, these are relatively inexpensive and
AlN which is very excellent in both of the two characteristics of
It was Further, the upper surface of the submount 2 has a bonding property with the light source 1.
To improve, go from submount 2 to light source 1
It is preferable to form a thin film in the order of Ti, Pt, Au.
Yes.

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. Similar to the submount 2, this block 3 also has a high thermal conductivity and a linear expansion coefficient close to that of the submount 2 due to problems such as heat generated in the light source 1 and attachment to the submount 2, for example, 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, since the requirements for these characteristic values are not so strict as compared with the submount 2, it is preferable to select them in consideration of cost. Here, the block 3 is formed of a material such as Cu or Mo which is much cheaper than AlN and is relatively excellent in these 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.

Reference numeral 4 denotes a heat radiating plate. The heat radiating plate 4 has a function of releasing heat generated by the light source 1 and transmitted through the submount 2 and the block 3 to the outside.
Various members forming an optical pickup are placed and serve as a packaging substrate. Further, the heat dissipation plate 4 is provided with a hole 4a for adjustment. Block 3 is brazed,
It is fixed to the upper surface of the heat dissipation plate 4 with solder foil or the like. Heat sink 4
As the material of Cu, Al, Fe, or the like having high thermal conductivity can be considered.

The submount 2 and the block 3 are used here.
Although they are formed separately, when the output of the light source 1 is high and high thermal conductivity is required for these members, these members are integrally formed to improve the thermal conductivity. It is preferable. In this case, it is preferable to use a material having a very 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 attachment 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, 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 has a large adhesive strength, workability that can be fixed at any moment, small changes in volume before and after curing, and changes in volume due to changes in temperature and humidity, that is, low shrinkage ratio. The workability and the stability of the joint surface can be improved by satisfying these requirements. As such a bonding material, a UV adhesive which is instantly cured by being irradiated with ultraviolet rays is used here.
Also, a moisture-curing type instant adhesive may be used. In order to have sufficient attachment strength, the contact area (S) between the block 3 and the light guide member 5 is preferably S> 1 mm ² .

Reference numeral 13 denotes 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 hole 4a provided in the heat dissipation plate 4. Regarding the attachment of the light receiving element 13 and the light guide member 5, there is great adhesive strength, workability that can be fixed at an arbitrary moment, change in volume before and after curing, temperature,
Conditions such as a low shrinkage ratio that requires a small volume change due to humidity are required. By satisfying these conditions, workability and the stability of the joint surface are improved. As such a bonding material, a UV adhesive having particularly good workability is used here because it is instantly cured by irradiation with ultraviolet rays. A moisture-curing type instant adhesive may be used. Further, the light receiving element 13 has a plurality of light receiving portions for receiving the optical signal emitted from the light source 1, reflected by the light guide member 5, the recording medium and the like and returned. The optical signal detected by the light receiving unit is converted into an electric signal according to the amount of light. This electric signal has a magnitude of a current value at the beginning of conversion. However, this current has a demerit that it is extremely weak and noise is easily picked up.
Therefore, it is preferable to use the light receiving element 13 in which an IV amplifier having a function of converting a current value into a correlated voltage value and amplifying it is formed. However, it is required that the output voltage has a good response to the incident frequency of light. Further, the surface of the light receiving element 13 is provided with a plurality of electrodes 13a made of a thin film of Al or the like for taking out the received information as a signal.

14 is a package, and the package 14 is
On the upper surface of the heat dissipation plate 4, the above-mentioned block 3 and the light guide member 5,
It is provided so as to surround the light receiving element 13 and the like, and inside thereof, a lead frame 14a used for taking out an electric signal from the light receiving element 13 and supplying power to the light source 1 is molded. The package 14 has a rectangular parallelepiped shape with a hollowed central portion.
The step 14 is formed on the inner surface of the package 14 on the side where 4a is molded so as to expose the foot 14b of the lead frame.
c is provided. The shape of the package 14 may be cylindrical or the like. The lead frame foot 14b exposed on the step 14c provided on the package 14 for taking out 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 to a by wire bonding with a wire 14d made of Au, Al, or the like. Further, in order to supply power to the light source 1, the upper surface of the light source 1 and the foot 14b of the lead frame exposed on the step 14c provided on the package 14 are bonded with a wire 14d, and the submount 2
The electrode surface 2a, which is provided on the upper surface of the above so as to make electrical contact with the lower surface of the light source 1, and the foot 14b of the lead frame exposed at the step 14c provided on the package 14 are wire-bonded by the wire 14d as well. By connecting. The material of the package 14 is required to be excellent in low water absorption, low outgassing, etc. Here, a thermosetting resin such as an epoxy resin, which is the most common as an IC mold, is used. 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 was plated with Ni, and then Au was plated thereon. Further, for attachment between the package 14 and the heat dissipation plate 4, a bonding material having properties such as high adhesive strength, low water absorption, high airtightness (low leak characteristic), etc. is used. As a result, the stability of the bonding surface and the 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 designates a shell, and the shell 15 also has an outer shape like a rectangular parallelepiped hollowed out like the package 14, and its horizontal cross section is substantially the same as that of the package 14. . In addition, the material is required to have characteristics such as low water absorption and low outgassing in order to prevent impurities from entering the inside of the packaging. Here, polybutylene terephthalate (hereinafter referred to as PBT) having excellent properties was used. However, especially when properties such as strength and dimensional accuracy are required, an LCP that is more expensive than PBT but is excellent in these properties 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 mounting of the package 14 and the heat dissipation plate 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 denotes a cover member, which is used to prevent dust and the like from adhering to the light guide member 5 and the light receiving element 13, 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 with each other, the light guide member 5 is attached to the bottom of the cover member 16 with an epoxy adhesive, a UV adhesive, or the like. At this time, the thickness (t1) of the cover member 16 is 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 attached light guide member 5 or the tension when the adhesive hardens, 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 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 0.1≤t2≤.
It is preferable that the distance (d) between the cover member 16 and the light guide member 5 is 3.0 (mm) and 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. Regarding d, the smaller the better, the better it is, but the accuracy error during assembly may not be less than 0.1 mm. In this case, the cover member 16 comes into contact with the light guide member 5 during assembly and is damaged. There is a risk that By using such a configuration, the mounting relative positional accuracy between the light guide member 5, the light source 1, the submount 2 and the block 3 is improved, and the block 3 or the submount 2 is brought into thermal contact with another member. Therefore, the heat generated by 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.
From the standpoint of preventing dew condensation at 6, etc., gas such as N ₂ or Ar, N
It is preferable to fill an inert gas such as e and He. In that case, the gap 17 existing between the heat sink 4 and the light receiving element 13 has a bonding material having characteristics such as a small shrinkage rate, low water absorption, and high airtightness (excellent leak characteristics), for example, an epoxy potting agent. It is necessary to fill it with solder or solder. Thereby, the airtightness inside can be improved.

By using the configuration shown above,
The heat generated by the light source 1 can be easily radiated to the outside, and by providing a total of two openings on both end faces of the packaging, the antioxidant gas can be easily enclosed. Further, in the optical system, since 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 held, malfunctions due to the displacement of these positions, extra optical aberration, etc. occur. 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 according to the embodiment of the present invention, and FIG. 4 is a perspective view of the light guide member according to the embodiment of the present invention.

In FIG. 3, the submount 2 is mounted on the heat sink 4.
The laser light horizontally emitted from the light source 1 mounted horizontally via the block 3 enters the light guide member 5 through the surface 5f of the light guide member 5 having a plurality of parallel inclined surfaces, and the light guide member 5 Reaching the reflection type diffusion angle conversion hologram 7 which is formed on the second slope 5b and has a function of converting the diffusion angle of outgoing light with respect to the diffusion angle of incident light (hereinafter referred to as NA conversion). . The light whose NA is 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, and the 0th order diffracted light (hereinafter referred to as the main beam) and the ± 1st order diffracted light (hereinafter referred to as the side beam). Called)). The main beam and side beams generated by the diffraction grating 6 are incident on the first polarization-selective beam splitter film 9 (hereinafter simply referred to as the first beam splitter film). The first beam splitter film 9 has a transmittance of almost 100% with respect to light having an oscillating component parallel to the incident surface (hereinafter simply referred to as P-polarized component), and has a vertical oscillating component (hereinafter simply referred to as S (Referred to as the polarization component) has a constant reflectance.
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. The main beam and the side beam linearly polarized into the S-polarized component reflected by the first beam splitter film 9 are transmitted through the surface 5e of the light guide member 5 and the cover member 16, and 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. At this time, the beam spots 29a and 29c of the two side beams are the main beam beam spot 2 on the recording medium surface 27a.
An image is formed in a substantially symmetrical position about 9b. The main beam and side beam beam spots 29b, 29a, and 29c are used to record or reproduce information signals and perform tracking and focusing, so-called servo signals are read from the recording medium surface 27a.

The divergence angle conversion hologram 7 corresponds to the divergence angle of a light beam of the light emitted from the light source 1 which can enter the divergence angle conversion hologram 7.
Converts the diffusion angle of reflected light from. Also, the diffusion angle conversion hologram 7 can convert parallel light having no diffusion angle. 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 spot on the recording medium 27 by the objective lens 26 is narrowed down to the diffraction limit to an ideal size, and information recording or reproduction is easily performed. You can

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

Of the return light from the recording medium 27, the light transmitted from the first beam splitter film 9 is the light guide member 5.
Second polarization-selective beam splitter film 11 formed on a third slope 5c parallel to the first slope 5a of
(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 has a constant reflectance for the S-polarized 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 slope 5c.

FIG. 5 is a perspective view of a polarization plane conversion substrate of an optical pickup according to an embodiment of the present invention, and FIG. 6 is a diagram showing a light receiving portion arrangement and signal processing of the optical pickup according to the embodiment of the present invention. . The polarization plane conversion substrate 31 has a first other slope (hereinafter referred to as a first other slope 31a) and a second other slope (hereinafter referred to as a second other slope 31b), and the first other slope 31a includes A reflective film 126 is provided,
The polarization separation film 12 is formed on the second slope 31b. The transmitted light 117 first enters the second other slope 31b. The polarization separation film 12 transmits the transmitted light 1 on the second slope 31b.
It is provided at 17 incident positions. And the polarization separation film 1
2 is preferably formed so that the incident transmitted light 117 is almost entirely projected onto the film.

The second other inclined surface 31b is preferably provided so as to be inclined with respect to the transmitted light 117, and in particular, the angle formed by the polarization plane 117a of the transmitted light 117 and the incident surface 128 is approximately 45 × (2n + 1). It is preferable that it is formed so as to be ∘: (n is an integer). With such a configuration, the P-polarized component 117p and the S-polarized component 117s of the transmitted light 117 have an intensity ratio of approximately 1: 1. Therefore, by detecting the respective signals, the differential is obtained. , The noise component on the signal can be cancelled, and the signal amount can be almost doubled.
An F signal can be obtained.

Here, the structure of the polarization plane conversion substrate 31 will be described in more detail. 7 is a side view of the light guide member 5 according to the embodiment of the present invention, FIG. 8 is a top view of the light guide member 5 according to the embodiment of the present invention, and FIG. 9 is a surface of the light guide member 5 according to the embodiment of the present invention. Light guide member 5 at AB
FIG. As shown in the figure, the polarization plane conversion substrate 31
In many cases, the shape is a rectangular parallelepiped shape, and a plurality of substantially transparent substrates are bonded together, and the first and second slopes 31a and 31b arranged in the polarization plane conversion substrate 31 are arranged. have. Further, the first other slope 31a and the second other slope 31b are a straight line formed by the first other slope 31a or the second other slope 31b on the AB cross section of the light guide member 5 and the transmitted light 117 incident on the polarization separation film 12. Is preferably arranged with an angle of α between the first and second slopes 31a and 31b with respect to the extending direction of the straight line formed by the side surface 5g of the light guide member 5 in FIG. It is preferable to be arranged with an angle of β with the extending direction of the straight line formed by 31b. If the incident angle of the transmitted light 117 entering the polarization separation film 12 is θ1, the transmitted light 1
The angle between the polarization direction 117a of 17 and the incident surface 128 of the polarization separation film 12 (a plane including the incident optical axis of the transmitted light 117 with respect to the polarization separation film 12 and the reflection optical axis reflected by the polarization separation film 12) is approximately It is preferable that α and β are arranged at an angle represented by the following equation using θ1 so that it can be set to 45 °.

[0042]

[Equation 1]

[0043]

[Equation 2]

Further, the arrangement of the optical elements provided on the polarization plane conversion substrate 31 will be described. FIG. 10 is a comparative cross-sectional view of a light guide member according to an embodiment of the present invention and a conventional light guide member.

In FIG. 10, the above is a cross-sectional view of a conventional light guide member, which is a polarization plane conversion substrate 531.
Since the polarization separation film 512 and the reflection film 626 provided on the first separation slope 531a and the second separation slope 531b are provided over the entire surface, the polarization separation film 512 reflects and the reflection film 6
In order to prevent the light that has reached 26 and is reflected there toward the light receiving element from entering the polarization separation film 512, the lateral width L1
Was very large.

On the other hand, as shown in the lower part of FIG. 10, the reflection film 126 is provided on a part of the first other slope 31a, and the polarization separation film 12 is provided on a part of the second other slope 31b. Even if the separation film 12 and the reflection film 126 are made closer to each other, there is almost no possibility that the light reflected by the reflection film 126 is incident on the polarization separation film 12 again. Therefore, the second other slope 31b on which the polarization separation film 12 is formed and the reflection film 126
Since the polarization plane conversion substrate 31 can be formed in a state in which the distance between the first and other slopes 31a on which the light is formed is extremely small, the volume of the polarization plane conversion substrate 31 can be greatly reduced, and in particular L The thickness in the direction can be made very thin. As a result, it is possible to greatly reduce the size of the optical pickup, which is a market need, and it is possible to reduce the cost by reducing the raw material cost accompanying the size reduction.

Further, the polarization separation film 12 is formed only on the light incident portion of the second other inclined surface 31b and its periphery, and the reflection film 1 is formed.
By forming 26 only on the light incident portion of the first other slope 31a and its periphery, the light before entering the polarization separating film 12 can be obtained even if the distance between the polarization separating film 12 and the reflecting film 126 is further reduced. The amount of light that is reflected by the reflection film 126 and is incident on the polarization separation film 12 is hardly reduced, and there is almost no possibility that the light reflected by the reflection film 126 is incident on the polarization separation film 12 again. Therefore, the polarization plane conversion substrate 31 can be configured with the distance between the second other slope 31b on which the polarization separation film 12 is formed and the first other slope 31a on which the reflection film 126 is formed being further reduced. The volume of the polarization plane conversion substrate 31 can be greatly reduced, and the thickness in the L direction can be made extremely small. As a result, it is possible to greatly reduce the size of the optical pickup, which is a market need, and it is possible to reduce the cost by reducing the raw material cost accompanying the size reduction.

Part of the light does not enter the reflection film 126 before entering the polarization separation film 12, and the light reflected by the polarization separation film 12 is reflected by the reflection film 126 and then re-polarized. Since it does not enter the separation film 12, almost all of the light that has entered the polarization plane conversion substrate 31 can be guided to the polarization separation film 12, and the polarization separation film 12 has an optical path of approximately 1: in the optical path corresponding to the component. The light divided into 1 can be guided to the light receiving portion corresponding to each component of the light receiving element 13 while maintaining the light amount. Therefore, the amount of signal converted by the light receiving element 13 can be made sufficient, and
A good RF signal can be formed.

In the present embodiment, both the polarization separation film 12 and the reflection film 126 are provided so as to be smaller than the area of the first other slope 31a and the second other slope 31b, but only one of them is formed in this way. With such a configuration, the same effect can be obtained to some extent.

Further, the first other slope 31a and the second other slope 31b.
By forming and in parallel, it suffices to bond the polarization plane conversion substrate 31 to the parallel plane substrates on which a plurality of predetermined optical elements are formed and cut it out, and it is not necessary to adjust the angle during the bonding. Therefore, the polarization plane conversion substrate 3 can be very easily
1, the polarization plane conversion substrate 31 with high positional accuracy can be obtained at low cost.

In the polarization plane conversion substrate 31 attached so as to satisfy such conditions, the light transmitted through the second beam splitter film 11 is first polarized light separation film 12.
Incident on. Since the polarization separation film 12 has a function of transmitting the P-polarized component and reflecting the S-polarized component, the P-polarized component 117p having the polarized component parallel to the incident surface 128 is formed.
Transmits almost 100% through the polarization separation film 12, while the S polarization component 117s having a polarization component perpendicular to the incident surface 128 is almost 100% due to the polarization separation film 12 on the second other inclined surface 31b.
%, And enters the reflection film 126 provided on the first other slope 31a. Then, the S-polarized component 1 that has entered
17s is reflected there and is guided to the light receiving element 13. The material of the reflective film 126 is Ag, Au, Al, C
It is preferable to use a metal material having a high reflectance even if it is relatively thin, such as u, or an alloy material obtained by adding Si, Ti, Ni, or the like to these metal materials, because the light utilization efficiency can be increased. . In particular, Ag is preferable because it is excellent in reflectance and cost.

By setting the polarization plane conversion substrate 31, the polarization separation film 12 and the reflection film 126 at the angles as described above, the polarization separation film 512 and the reflection film 6 are formed as in the conventional case.
26 is not formed on the entire surface of the first other slope 531a and the second other slope 531b provided on the polarization conversion substrate 531.
Since the polarization separation film 12 and the reflection film 126 are provided at and around the portion where the light flux enters, the polarization plane conversion substrate 31
In particular, since the thickness in the L direction can be made thin, the thickness in the L direction of the light guide member 5 can be made thin, and thus the thickness of the optical pickup can be made thin, and the volume thereof can be greatly reduced. be able to.

In this embodiment, the polarization direction 117a of the transmitted light 117 and the incident surface of the polarization separation film 12 (the incident optical axis of the transmitted light 117 with respect to the polarization separation film 12 and the reflection optical axis reflected by the polarization separation film 12 are The angle (hereinafter referred to as δ) formed with the plane including is about 45 °, but by setting δ not to be 0 ° (non-parallel), a significant amount of P
Since the polarization component and the S polarization component can be formed,
The noise level can be reduced and the amount of signal can be increased. Further, by setting δ to 40 ° to 50 °, the P-polarized component and the S-polarized component that are formed can be made to have substantially the same amount, so that the noise level can be further reduced and the signal amount can be increased. Can be made.

[0054]

As described above, according to the present invention, in a light guide member constituting an optical pickup, a first region in which a polarization separation element is provided on a first other inclined surface and a second region in which a polarization separation element is not provided. And a third region provided with the reflection means and a fourth region not provided with the reflection means are formed on the second other inclined surface, and the incident light transmits through the fourth region to form the third region. The light incident on the first region and reflected on the first region is reflected on the third region, passes through the second region and is incident on the light receiving means. Before the light is reflected by the reflection means and the light amount is prevented from decreasing, and the light reflected by the polarization separation element is almost completely prevented from entering the polarization separation element again after being reflected by the reflection means. Therefore, it is possible to reduce the amount of light that has entered the polarization conversion substrate. The total amount can be guided to the polarization separation element, and the light split by the polarization separation element into an optical path corresponding to the component in a ratio of about 1: 1 can be adjusted according to each component provided in the light receiving means while maintaining the light amount. It can be guided to the light receiving part. Therefore, the amount of signal converted by the light receiving means can be made sufficient, and a good RF signal can be formed.

Further, since the thickness of the light guide member can be reduced, it is possible to easily reduce the size of the optical pickup, which is a market need, and to reduce the cost by reducing the raw material cost accompanying the size reduction. It will be possible.

[Brief description of drawings]

FIG. 1 is a sectional view showing a packaging configuration 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 of the optical pickup according to the 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 side view of the light guide member according to the embodiment of the present invention.

FIG. 8 is a top view of the light guide member according to the embodiment of the present invention.

FIG. 9 is a cross-sectional view of the light guide member on the plane AB in the embodiment of the present invention.

FIG. 10 is a comparative cross-sectional view of a light guide member according to an embodiment of the present invention and a conventional light guide member.

FIG. 11 is a conceptual diagram of a conventional optical pickup.

FIG. 12 is a perspective view of a conventional polarization plane conversion substrate.

[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 5g side 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 31c Side surface 31d Reflection film 117 Transmitted light 117a Polarization plane 117s S polarization composition 117p P-polarized light component 123 reflected light 124 reflective film 125 reflecting film 126 reflective film 128 incident surface 170,171,172,172a, 172b, 172
c, 172d, 176, 177 Light receiving part

Claims (20)

(57) [Claims] 1. A light source and a plurality of slopes inclined with respect to an incident direction of light emitted from the light source are arranged substantially parallel to each other to form various optical elements on the slopes and the slopes. A light guide member having a plurality of other inclined surfaces further inclined with respect to each other, and a light receiving means for converting light transmitted through the light guide member into an electric signal, and one of the plurality of other inclined surfaces A polarization separation element that transmits or reflects light depending on the polarization direction of light is provided on the slope in an area smaller than the area of the one other slope, and among the plurality of other slopes. An optical pickup characterized in that a reflecting means for reflecting light is provided on another one of the other slopes. 2. The optical pickup according to claim 1, wherein the reflecting means is provided in an area smaller than the area of the one other inclined surface. 3. The optical pickup according to claim 1, wherein the polarization separation element is provided at a portion where light is incident on the one other inclined surface and a peripheral portion thereof. Wherein said reflecting means optical pickup according to claim 1, characterized in that provided on the portion and its periphery which light is incident on said one other slopes. 5. A light source, said plurality of slopes with and a plurality of inclined surfaces which are inclined relative to the direction of the irradiated light are arranged substantially parallel to each other to form various optical elements to said plurality of slopes from the light source A light guide member having a plurality of other inclined surfaces further inclined with respect to each other, and a light receiving means for converting light transmitted through the light guide member into an electric signal, and one of the plurality of other inclined surfaces A polarization separation element that transmits or reflects light according to the polarization direction of light is provided on the slope, and a reflection means that reflects light is provided on another one of the other slopes. And a second region where the polarization separation element is not provided and a second region where the polarization separation device is not provided are formed on the one other slope. The light reflected in the area of An optical pickup characterized in that the light is reflected by a means, transmitted through the second region and made incident on the light receiving means. 6. A light source, comprising a plurality of inclined surfaces which are inclined relative to the direction of light emitted from said light source, said plurality of slopes arranged substantially parallel to each other, various optical elements to said plurality of inclined surfaces A light guide member having a first other slope different in inclination from the plurality of slopes and a second other slope arranged in a predetermined relationship with the first other slope.
A light receiving means for converting the light transmitted through the light guide member into an electric signal; and a polarization separation element provided on the first other inclined surface for transmitting or reflecting the light according to the polarization direction of the light, A reflection means for guiding the light reflected by the polarization separation element to the light receiving means provided on the second other inclined surface, and the polarization separation element is provided on the first other inclined surface. An area and a second area where the polarization separation element is not provided are formed, and a third area where the reflecting means is provided and the reflecting means are not provided on the second other inclined surface. A fourth region is formed, the incident light is transmitted through the fourth region and is incident on the first region, and the light reflected by the first region is reflected by the third region. And pass through the second region to enter the light receiving means. The optical pick-up that. Wherein said first other inclined surface and the second optical pickup according to claim 6, characterized in that the other inclined surface is provided substantially in parallel. 8. The optical pickup as claimed in any one of claims 7, characterized in that said polarization separation element is formed by a dielectric film. 9. The optical pickup according to claim 1, wherein the reflecting means is made of a metal material. 10. The first area is provided in a light incident area on the first other inclined surface and a peripheral portion thereof,
10. The optical pickup according to claim 6, wherein the third region is provided in a region where the light reflected by the first region is incident and a peripheral portion thereof. . 11. A plurality of slopes, which are arranged to be inclined with respect to the direction of light emitted from a light source, are arranged substantially parallel to each other, and various optical elements are formed on the plurality of slopes. In contrast, it has a plurality of other inclined surfaces which are further inclined, and emits the light incident from the light source to the outside, and guides the light incident from the outside to a predetermined position through the plurality of inclined surfaces and the plurality of other inclined surfaces. A light guide member, wherein a polarization separation element that transmits or reflects light according to the polarization direction of light is provided on one of the other inclined surfaces, and the polarization separation element is larger than the area of the other inclined surface. A light guide member, which is provided in a small area, and is provided with a reflection means for reflecting light on another one of the plurality of other slopes. Claims 12. The reflecting means is characterized in that provided in the area smaller than the area of said one of the other slope 1
1. The light guide member according to 1 . 13. The light guide member according to claim 11, wherein the polarization separation element is provided at a portion where light is incident on the one other inclined surface and a peripheral portion thereof. 14. The reflecting means is provided at a portion where light is incident on the one other inclined surface and a peripheral portion thereof.
The light guide member according to claim 11 . 15. A plurality of slopes arranged to be inclined with respect to a direction of light emitted from a light source are arranged substantially parallel to each other to form various optical elements on the slopes and to the slopes. A plurality of other inclined surfaces that are further inclined, and a polarization separation element that transmits or reflects light according to the polarization direction of light is provided on one of the other inclined surfaces. A reflecting means for reflecting light is provided on the other one of the plurality of other slopes, the light incident from the light source is emitted to the outside, and the light incident from the outside is the plurality of slopes and the plurality of slopes. A light guide member for guiding to a predetermined position via another inclined surface, wherein the polarization separation element and the first region where the polarization separation element is provided are provided on one of the other inclined surfaces. Not formed a second region, said The light guide member characterized in that the light reflected by the first area is reflected by the reflecting means and transmitted through the second area to be guided to a predetermined position. 16. A plurality of slopes that are inclined with respect to the direction of light emitted from a light source are arranged substantially parallel to each other to form various optical elements on the slopes, and the slopes are The first other inclined surface having a different inclination, and the second other inclined surface arranged in a predetermined relationship with the first other inclined surface, the light depending on the polarization direction of the light on the first other inclined surface. A polarization separating element that transmits or reflects light, and a reflecting unit that guides the light reflected by the polarization separating element to a predetermined position on the second other inclined surface, and externally reflects the light incident from the light source. Is a light guide member that guides light incident on the outside through a plurality of slopes and a plurality of other slopes to a predetermined position, and the polarization separation element is provided on the first other slope. The first region and the second region where the polarization separation element is not provided. Region is formed, a third region where the reflecting means is provided and a fourth region where the reflecting means is not provided are formed on the second other slope, and the incident light is The light transmitted through the fourth region and incident on the first region, and the light reflected by the first region is reflected by the third region and transmitted through the second region to be guided to a predetermined position. A light guide member characterized by the above. 17. The method of claim 1, characterized in that said first other inclined surface and the second other inclined surface is provided substantially in parallel
6. The light guide member according to 6 . 18. The light guide member according to claim 11, wherein the polarization separation element is formed of a dielectric film. 19. The claim 17 claim 11, characterized in that said reflecting means is formed of a metal material 1
The light guide member according to. 20. The first region is provided in a region on the first other slope where light is incident and a peripheral portion thereof,
20. The light guide according to claim 16, wherein the third region is provided in a region where light reflected by the first region is incident and a peripheral portion thereof. Element.