JP3509314B2 - Optical pickup - 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 an optical element, an optical disc or the like.

[0002]

2. Description of the Related Art The structure of a conventional optical pickup will be described below with reference to FIGS. FIG. 12 is a top view of an LD block of a conventional optical pickup.
3 is a side view of an LD block of a conventional optical pickup. Reference numeral 501 denotes a light source, and the light source 501 emits light having a predetermined wavelength to the outside. Here, a semiconductor laser is used. A submount 502 holds the light source 501 and has a function of releasing heat generated by the light source 501 to the outside. The light source 501 and the submount 502 are joined by soldering or the like at their connecting surfaces. Reference numeral 503 denotes a block, and the block 503 has a function of placing the submount 502 on the upper surface thereof and further releasing the heat conducted by conduction from the submount 502 to the outside.
Reference numeral 504 is a wire bonded to the upper surface of the light source 501 for supplying power to the light source 501, and 505 is a wire also bonded to the electrode surface 502a.
The light source 501 and the submount 502 having such a configuration
When inspecting the light source 501 in an assembly of the block 503 (hereinafter referred to as an LD block), a detection probe for supplying electric power is used as the electrode surface 502a and the light source 5.
The light emitted from the light source 501 was inspected for its wavelength, intensity, etc. by hitting it on the upper surface of 01.

[0003]

However, in the above-mentioned conventional structure, since the area of the upper surface of the light source 501 is very small, it is difficult to connect the detection probe to the upper surface of the light source 501. When the probe is connected to the upper surface of the light source 501, the wire bonded to the light source 501 may be damaged, or the light source 5 may be broken by the detection probe.
There was a problem that 01 itself was destroyed.

The present invention is intended to solve the above problems, and an object thereof is to make it possible to easily inspect a semiconductor laser used as a light source of an optical pickup.

[0005]

To achieve this object, a light source, a submount on which the light source is mounted, and a submount.
A block for mounting a light source, and a plurality of inclined surfaces that are inclined with respect to the incident direction of the light emitted from the light source, and reflect the light from the light source on the plurality of inclined surfaces to guide it to the optical medium. -out guide the light reflected from the medium to a predetermined position, blanking
A light guide member joined to the lock, and a plurality of electrodes provided on the surface of the submount that faces the light source. The light source is placed on the first electrode of the electrodes and the end surface of the light source and the first electrode. The electrodes are electrically connected, and the second electrode of the electrodes and the end surface opposite to the end surface of the light source are electrically connected by wire bonding.
The electrode film is formed on almost the entire surface to be the mounting surface, and the electrode film is
The groove is made by cutting or cutting with a dicing saw.
It was formed by kicking .

[0006]

With this structure, the inspection probe for inspecting the light source can be easily conducted, and the possibility of damaging the light source and the power source line for the light source can be reduced.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The packaging of a first 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 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.

Reference numeral 2 denotes a submount, and the submount 2 has a rectangular parallelepiped shape or a plate shape, and the light source 1 is attached to the upper surface thereof. This submount 2 is a light source 1
And has a function of releasing heat generated by the light source 1. In consideration of thermal conductivity and the like, a method of press-bonding a foil (thickness of several μm to several tens of μm) of Au—Sn, Sn—Pb, In or the like at high temperature is used for joining the submount 2 and the light source 1. preferable. If the light source 1 and the submount 2 are not mounted substantially horizontally, they will cause aberrations of the optical system.
Therefore, at the time of joining, it is preferable that the light source 1 is mounted on the submount 2 at a predetermined position and at a predetermined height substantially horizontally. Further, an electrode surface 2a is provided on the upper surface of the submount 2 so as to be electrically connected to the lower surface of the light source 1. The electrode surface 2a will be described with reference to FIGS. 3 and 4.
FIG. 3 is a top view of the vicinity of the light source in one embodiment of the present invention.
FIG. 4 is a side view of the vicinity of the light source in one embodiment of the present invention. The electrode surface 2a supplies power to the light source 1, and is widely provided on the upper surface of the submount 2. Further, the electrode surface 2a is connected to the first electrode surface 2 having a different potential via the groove 2d.
b and the second electrode surface 2c, and the light source 1 has its bottom surface electrically connected to either one of the first electrode surface 2b and the second electrode surface 2c. The light source 1 is mounted and the other surface of the light source 1 is electrically connected to the electrode surface on the side where the light source 1 is not mounted. For example, if the light source 1 is placed on the first electrode surface 2b, the light source 1
Is connected to the first electrode surface 2b, and the light source 1
Is electrically connected to the second electrode surface 2c. Here, wire bonding is preferably used for electrical connection between the upper surface of the light source 1 and the second electrode surface 2c. As a method of forming the groove 2d, a method of forming by etching, a method of using a dicing saw, or the like can be considered.

First, a method using etching will be described. The material and thickness are the same as the submount 2,
On one surface of the submount substrate capable of cutting out a plurality of submounts, a Ti film to be the electrode surface 2a, Pt
A film and an Au film are sequentially formed on the entire surface. Next, a mask processed according to the shape of the electrode surface 2a to be formed is placed on the upper surface of the submount 2 and etched. As a result, the first electrode surface 2b, the second electrode surface 2c and the groove portion 2d are provided,
The electrode surface 2a having a predetermined shape is formed. The type of etching at this time may be either dry etching or wet etching. Then, by cutting the submount substrate into a predetermined shape, the submount 2 having the electrode surface 2a having a predetermined shape is completed.

When a dicing saw is used, as in the case of etching, a Ti film, a Pt film, and an Au film, which will be the electrode surface 2a, are sequentially formed on almost the entire surface of the submount substrate, and then the submount substrate is formed. The electrode surface 2a side is processed with a dicing saw to make a notch, and the notch is used as a groove 2d to form the electrode surface 2a.

In particular, when joining the light source 1 and the submount 2 with solder, an electrode formed on the upper surface of the submount 2 in order to improve the leakability of the solder and the adhesive force of the solder. Ti film, Ni film, A as a film forming the surface 2a
It is preferable to use a u film, a Ni film, or an Au film.

Next, a method of inspecting the light source 1 mounted on the submount 2 thus constructed will be described. A semiconductor laser is mainly used for the light source 1. However, since the non-defective product ratio is relatively low, it is necessary to inspect at the time of assembly. At the time of inspection, a voltage detection probe is connected to the first electrode surface 2b and the second electrode surface 2c of the electrode surface 2a provided on the upper surface of the submount 2, and a voltage is applied to the light source 1, The light source 1 is caused to emit light, and the characteristics of the wavelength, divergence angle, and current / light intensity of the emitted light are measured. An optical spectrum analyzer is used to measure the wavelength, and a power meter is used to measure the light intensity.

Submount 2 having the above structure
Then, when the light source 1 is to be inspected, the electric detection probe may be connected to the first electrode surface 2b and the second electrode surface 2c widely provided on the upper surface of the submount 2 for inspection. That is, unlike the conventional case, it is not necessary to connect the detection probe to the upper surface of the light source 1, so that the inspection is easy and the light source is less likely to be damaged.

Furthermore submount 2, the mounting problems such as heat and light source 1 for generating at the light source 1, the thermal conductivity is high and it linear expansion coefficient of the light source 1 (about 6.5 × 10 ^{- 6} /
A material close to ℃) is preferable. Specifically, the linear expansion coefficient is 3
A substance having a thermal conductivity of 100 w / mK or more at 10 × 10 ⁻⁶ / ° C., such as AlN, SiC, T-cBN, Cu
It is preferable to use / W, Cu / Mo, Si or the like, and particularly diamond or the like when a high output laser is used and the thermal conductivity must be extremely high. When the linear expansion coefficients of the light source 1 and the submount 2 are set to be the same or close to each other, it is possible to suppress the occurrence of distortion between the light source 1 and the submount 2, so that It is possible to prevent inconveniences such as detachment of the mounting portion and cracking of the light source 1. However, if it is out of this range, a large distortion may occur between the light source 1 and the submount 2, and the mounting portion between the light source 1 and the submount 2 may come off, or the light source 1 may be cracked or the like. Get higher Further, by taking the thermal conductivity of the submount 2 as large as possible, the heat generated in the light source 1 can be efficiently released to the outside. However, when the thermal conductivity is less than or equal to this limit, the heat generated in the light source 1 becomes difficult to escape to the outside, so that the temperature of the light source 1 rises, the output of the light source 1 decreases, and the life of the light source 1 shortens. In some cases, inconveniences such as destruction of the light source 1 in the worst case may occur. In this embodiment, it is relatively inexpensive and these two
AlN, which is very excellent in both of the two characteristics, was used.

Reference numeral 3 denotes a block. 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 in joining the block 3 and the submount 2, Au-Sn, Sn-Pb, I, although slightly expensive, is also used, as in the case of the submount 2 and the light source 1.
It is preferable to press-bond a foil such as n (thickness several μm to several tens 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. The block 3 is fixed to the upper surface of the heat dissipation plate 4 by brazing, solder foil or the like. As the material of the heat dissipation plate 4, Cu, Al, F having high thermal conductivity is used.
e etc. are 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 to have a large contact area with the heat sink 4. The surface of the block 3 facing the light source 1 is divided into two parts by a dicing saw or the like.

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 a light source. It has a function of emitting the emitted light and guiding the returned light to a predetermined position. Further, the light guide member 5 is adhered to 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. Regarding attachment of the light receiving element 13 and the light guide member 5, there is a large adhesive strength, workability that can be fixed at an arbitrary moment, change in volume before and after curing, and change in volume due to temperature and humidity are small, that is, low shrinkage rate. Conditions such as the above are required, and by satisfying these conditions, workability and stability of the joint surface are improved. As such a bonding material, U which has particularly good workability because it is instantly cured by being irradiated with ultraviolet rays.
V adhesive was used. 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 outer peripheral shape of the package 14 may be cylindrical or the like. And the light receiving element 13
1 of the lead frame exposed on the step 14c provided on the package 14 for extracting the electric signal from the lead frame 1.
4b and a plurality of electrodes 13a provided on the surface of the light receiving element 13 are connected by wire bonding with a wire 14d formed of Au, Al or the like. Further, in order to supply power to the light source 1, the legs 14 of the lead frame exposed at the step 14c provided on the upper surface of the light source 1 and the package 14.
b is bonded with a wire 14d, and leads exposed on the electrode surface 2a provided on the upper surface of the submount 2 so as to be electrically connected to the lower surface of the light source 1 and the step 14c provided on the package 14. The legs 14b of the frame are also connected by wire bonding with wires 14d. 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. The material of the lead frame 14a is Cu, 42 alloy, F
In many cases, a metal such as e is plated with Ag or Au. Here, Cu is plated with Ni, and A is applied on top of it.
A u-plated product was used. 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, although it takes some time to bond, an inexpensive epoxy adhesive excellent in these properties was used.

Reference numeral 15 denotes 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. Polyethylene terephthalate (hereinafter referred to as PBT) having excellent properties was used here. 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 is a cover member, which is used to prevent dust and dirt 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 by an epoxy adhesive. ing. Further, as the material of the cover member 16, it is preferable to use glass such as BK-7, FK-1, K-3, or a resin having a high light transmittance such as urethane, polycarbonate, or acrylic.
When reading a magneto-optical signal, it is not preferable to use a member having a large birefringence even if the light transmittance is high. Further, an antireflection film 16a is formed on both upper and lower surfaces of the cover member 16 to prevent reflection. This antireflection film 16a is preferably formed of a material such as MgF ₂ . However, if reflection on the surface of the cover member 16 does not pose a problem, the antireflection film 16a may not be provided.

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 brought into contact with each other or 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 structure, the height of the packaging 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≤.
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.

From the viewpoint of preventing oxidation of the light source 1 and the light receiving element 13, the inside of the packaging of the optical pickup is
A dry antioxidant gas such as N ₂ gas 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. Further, in this case, the cover member 16 also has a function of separating the inside and the outside of the packaging.

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.

Next, the operation of the optical pickup according to the embodiment of the present invention will be described with reference to the drawings. FIG. 5 is a sectional view of an optical pickup according to an embodiment of the present invention, and FIG. 6 is a perspective view showing an assembly of the optical pickup according to the embodiment of the present invention.

In FIGS. 5 and 6, the laser light emitted horizontally from the light source 1 mounted horizontally on the heat sink 4 via the submount 2 is the surface of the light guide member 5 having a plurality of parallel inclined surfaces. The diffusion angle of the light that is incident on the light guide member 5 from 5f and is formed on the second slope 5b of the light guide member 5 and that is emitted is converted with respect to the diffusion angle of the incident light (hereinafter referred to as NA conversion). It reaches the reflection type diffusion angle conversion hologram 7 having a function. Diffusion angle conversion hologram 7
The light whose NA has been converted and reflected by the first slope 5
The reflection type diffraction grating 6 formed in a divides the light into 0th order diffracted light (hereinafter referred to as main beam) and ± 1st order diffracted light (hereinafter referred to as side beam). 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). 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. In addition, the main beam and the side beam that reflect the first beam splitter film 9 are
The light passes through the surface 5e of the light guide member 5, 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. At this time, the recording medium surface 2
Beam spot 2 of two side beams on 7a
9a and 29c are beam spots 29b of the main beam
An image is formed at a position substantially symmetrical with respect to. Information recording or reproduction signals, tracking, and focusing, so-called servo signals are read from the recording medium surface 27a by beam spots 29b, 29a, and 29c of main beams and side beams.

The diffusion angle conversion hologram 7 is a diffusion angle conversion hologram 7 with respect to a diffusion angle of a light beam of the light emitted from the light source 1 which can enter the diffusion angle conversion hologram 7.
The diffusion angle of the reflected light from can be freely converted.
Also, the diffusion angle conversion hologram 7 can convert parallel light having no diffusion angle. Further, as shown in FIG. 1, the same divergence angle conversion hologram 7 forms an ideal spherical wave 30 in which the wavefront aberration integrated by the light flux emitted from the light guide member 5 in the midway path is removed. Therefore,
The incident light on the objective lens 26 becomes an ideal spherical wave 30, and the image forming spot on the recording medium 27 by the objective lens 26 is narrowed down to the diffraction limit to an ideal size, so that information can be easily recorded or reproduced. 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 first inclined surface 5a of the light guide member 5, and again the second light guide member. Is incident on the first beam splitter film 9 formed on the slope 5b. 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 S
(Referred to as the polarization component) has a constant reflectance.

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 polarization beam splitter film 11 has a transmittance of almost 100% for the P-polarized component and a constant reflectance for the S-polarized component similarly to the first beam splitter film 9.

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. 7 is a perspective view of a polarization plane conversion substrate according to one embodiment of the present invention, and FIG. 8 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 conversion substrate 31 includes a first other slope 31a (hereinafter simply referred to as the first other slope) and a second other slope 31b parallel to the first other slope 31a (hereinafter simply referred to as the second other slope). The reflection film 126 is formed on the first other inclined surface 31a, and the polarization separation film 12 is formed on the second other inclined surface 31b. The transmitted light 117 enters the polarization separation film 12 formed on the second other inclined surface 31b. The second other slope 31b is the transmitted light 1
The angle between the polarization plane 117a of 17 and the incident surface 128 is approximately 4
It is formed so as to be 5 ° (2n + 1), (n is an integer). As a result, the P-polarized component 117p and the S-polarized component 117s of the transmitted light 117 have an intensity ratio of about 1: 1. The P polarization component 117p having a polarization component parallel to the incident surface 128 is almost 100% transmitted by the polarization separation film 12, while the S polarization component 117s having a polarization component perpendicular to the incidence surface 128 is on the second other inclined surface 31b. Polarization separation film 12
Is reflected by approximately 100%, enters the surface of the first other inclined surface 31a, is reflected by the reflective film 126, and is guided to the light receiving element 13. Of the light guided onto the light receiving element 13, the P deflection component 117p reaches the light receiving section 170, and the S deflection component 117s reaches the light receiving section 171.

Next, the reflected light 123 of the light beam incident on the second beam splitter film 11 shown in FIG. 5 will be described. The reflected light 123 enters the astigmatism generation hologram 10 formed by the reflection type hologram on the second slope 5b. The reflected light 123 is reflected by the reflection film 124 and the reflection film 125 while the astigmatism is generated by the astigmatism generation hologram 10, and the return light of the main beam is reflected by the light receiving section 172 on the light receiving element 13 to the side beam. The return light reaches the light receiving portions 176 and 177 on the light receiving element 13.

Next, in the first embodiment of the present invention, the structure of the optical pickup particularly adapted to the phase change type optical disk will be described with reference to the drawings. A phase-change optical disc records information by changing the crystal structure in the recording medium by irradiating light, and thus requires a larger amount of light than the conventional optical recording / reproducing device to change the crystal structure. Therefore, a more efficient optical system is required. FIG. 9 is a conceptual diagram showing the operation of the optical pickup for a phase change type optical disc in one embodiment of the present invention. The members having the same numbers as those shown in FIGS. 1, 2 and 3 have the same functions and configurations, and thus the description thereof will be omitted.

The laser light emitted horizontally from the light source 1 is
The surface 32f of the light guide member 32 having a plurality of parallel inclined surfaces
Is incident on the light guide member 32 from the surface 32e of the light guide member 32 through the diffusion angle conversion hologram 7 and the beam splitter film 35 having polarization selectivity (hereinafter referred to as the beam splitter film). Here, unlike the case of the first embodiment, the beam splitter film 35 has an S-polarized component reflectance of 95% or more and a P-polarized component reflectance of approximately 1%.
It is a degree. Of the light that is incident on the beam splitter film 35, the light that passes through the beam splitter film 35 (a few percent of the total amount of light in the P-polarized component) is used as monitor light for the light emitted from the light source 1. The light emitted from the surface 32 e of the light guide member 32 passes through the λ / 4 plate 33 provided on the cover member 16. FIG. 10 is a diagram showing the configuration of the λ / 4 plate 33. The λ / 4 plate 33 is the light guide member 32.
The extraordinary optical axis is π / 4.
(2m-1); (where m is a natural number: the same applies hereinafter) and has a function of generating a phase difference of π / 2 · (2m-1) between the extraordinary light component and the ordinary light component of the incident light. Have A uniaxial crystal material is generally used as a material forming the λ / 4 plate 33. Among them, it is preferable to use a crystal that is low in cost and excellent in light transmittance. The uniaxial crystal has an extraordinary optical axis 616 and an ordinary optical axis 617, and has different refractive indexes called extraordinary light refractive index n _e and ordinary light refractive index n _o with respect to each optical axis. Since the traveling speeds of light are different between the extraordinary light and the ordinary light, a phase difference Δ determined by the following relational expression occurs when the substrate thickness of the λ / 4 plate 33 is QD and the incident light wavelength is λ. The thickness QD of the λ / 4 plate 33 is such that this phase difference Δ is π / 2.
・ It is decided to be (2m-1).

Δ = 2π · (n _e −n _o ) · QD / λ In this embodiment, the wavelength λ = 790 nm and the extraordinary light refractive index ne.
= 1.5477, and ordinary refractive index no = 1.5388 (however, the refractive index differs depending on the cutting angle of the substrate. Here, the refractive index is cut parallel to a plane including both the extraordinary optical axis and the ordinary optical axis). On the other hand, the substrate thickness of the λ / 4 plate 33 is 2
It becomes 1.9 · (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. In addition, here, a crystal of 21.9 μm was provided on the cover member 16 as the λ / 4 plate 33,
The same effect can be obtained by providing the surface 32e of the light guide member or the objective lens 26.

The light which 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 circularly polarized light reflected by the surface of the recording medium has its rotation direction reversed, so the return light is the objective lens 26.
When transmitted through the λ / 4 plate 33 again, it is converted into linearly polarized light containing only the P-polarized component. The return light thus converted passes through the surface 32e of the light guide member 32 again,
It again enters the beam splitter film 35 formed on the second inclined surface 32b of the light guide member. The beam splitter film 35 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-polarized component). (Referred to) has a constant reflectance. Therefore, the return light having only the P-polarized component almost passes through the beam splitter film 35.

Then, the return light is incident on the half mirror 34 formed on the third slope 32c parallel to the first slope 32a of the light guide member 32. The half mirror 34 has a function of reflecting a predetermined amount of incident light and transmitting the rest.

Among the light fluxes that have entered the half mirror 34, the transmitted light 117 is guided to the light receiving section 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. 11 will be described. Figure 1
FIG. 2 is a layout view of a light receiving portion on a light receiving element of an optical pickup for a phase change type optical disk in one embodiment of the present invention.
The reflected light 123 enters the astigmatism generation hologram 10 formed by the reflection type hologram on the second inclined surface 32b. 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 structure, the λ / 4 plate is used as the beam splitter film 35 and the recording medium 2.
7, which converts the emitted light, which is the linearly polarized light of the S-polarized component, into circularly polarized light, and then converts the circularly polarized light, which is reflected by the recording medium 27 and whose rotation direction is reversed, into only the P-polarized component. The beam splitter film 35 by converting it into linearly polarized light
Since the light reflected by the recording medium 27 can be guided to almost the light receiving element 36 by making the incident light on the light receiving element 36, the reflectance of the S-polarized component of the beam splitter film 35 can be significantly increased, and therefore the recording medium 27 It is possible to increase the amount of light that is emitted to the.

[0047]

According to the present invention, the light source and the sub-device on which the light source is mounted are mounted.
A mount, a block on which the submount is mounted, and a plurality of inclined surfaces that are inclined with respect to the incident direction of the light emitted from the light source, and the light from the light source is reflected by the plurality of inclined surfaces to form an optical medium. guides, provided-out guide the light reflected from the optical medium to a predetermined position, and the light guide member which is joined to the block, and a plurality of electrodes provided on the light source and the surface facing the submount, of the electrodes The light source is placed on the first electrode to electrically connect the end surface of the light source and the first electrode, and the second electrode of the electrodes and the end surface opposite to the end surface of the light source are electrically connected by wire bonding. It is connected to, the plurality of electrodes Sa
An electrode film is formed on almost the entire surface of the bumount that will be the mounting surface of the light source.
And then etching the electrode film or cutting with a dicing saw.
By forming by forming the groove portion by embedding ,
The inspection probe for inspecting the light source can be easily used, and the possibility of damaging the light source and the power source line for the light source can be reduced. Further, by forming an electrode surface on the surface of the holding member facing the light source and providing a strip-shaped insulating portion for dividing the electrode surface, the divided electrode surface can be easily formed, and an inspection probe for light source inspection can be provided. It can be used easily and the possibility of damaging the light source and the power source line for the light source can be reduced. Further, by electrically connecting the second electrode and the upper surface of the light source by wire bonding, the two can be more easily connected.

[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 top view of the vicinity of a light source according to an embodiment of the present invention.

FIG. 4 is a side view of the vicinity of a light source according to an embodiment of the present invention.

FIG. 5 is a conceptual diagram of the operation of the optical pickup according to the embodiment of the present invention.

FIG. 6 is a perspective view of a light guide member according to an embodiment of the present invention.

FIG. 7 is a perspective view of a polarization plane conversion substrate of an optical pickup according to an embodiment of the present invention.

FIG. 8 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. 9 is a conceptual diagram of the operation of the optical pickup of the phase change type optical disc in one embodiment of the present invention.

FIG. 10 is a perspective view of a λ / 4 plate according to an embodiment of the present invention.

FIG. 11 is a layout view of a light receiving portion of an optical pickup for a phase change optical disc according to an embodiment of the present invention.

FIG. 12 is a top view of an LD block of a conventional optical pickup.

FIG. 13 is a side view of an LD block of a conventional optical pickup.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 light source 2 submount 2a electrode surface 2b first electrode surface 2c second electrode surface 2d groove 3 block 3a protrusion 3b side 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 others Slope 31b Second other slope 32 Light guide member 32a First slope 2b Second inclined surface 32c Third inclined surface 32e Surface 32f Surface 33 λ / 4 plate 34 Half mirror 35 Beam splitter film 36 Light receiving element 37, 38, 39, 40 Light receiving portion 117 Transmitted light 117a Polarization surface 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

─────────────────────────────────────────────────── --Continued from the front page (56) References JP-A-6-203420 (JP, A) JP-A-61-71432 (JP, A) JP-A-7-111282 (JP, A) JP-A-6- 85019 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) G11B 7/135

Claims (5)

(57) [Claims] 1. A light source and a submount on which the light source is mounted.
A block on which the submount is mounted, and a plurality of inclined surfaces inclined with respect to the incident direction of the light emitted from the light source, and the light from the light source is reflected by the plurality of inclined surfaces. and guides to the optical medium, guide-out, is joined to the block the light reflected from the optical medium to a predetermined position
A light guide member and a plurality of electrodes provided on a surface of the submount that faces the light source. The light source is mounted on the first electrode of the electrodes and the end surface of the light source and the first electrode. electrically connected to the electrode, and electrically connected to the end face opposite the end face of the light source and the second electrode of the electrode by wire bonding, the plurality of electrodes before
Almost the entire surface of the submount that will be the mounting surface of the light source
An electrode film is formed on the electrode film, and etching or dicing is performed on the electrode film.
An optical pickup formed by forming a groove portion by cutting a gusset . 2. A plurality of electrodes are a Ti film from the submount side,
Pt film, Au film formed in order, or submount side
To Ti film, Ni film, Au film in order,
Although Ni film and Au film were formed in order from the bumount side,
The optical pickup according to claim 1, wherein the optical pickup is any one of them . 3. A semiconductor laser composed of GaN as a light source.
The optical pickup according to claim 1, wherein the optical pickup is used. 4. AlN, SiC as a material of the submount
The optical pickup according to claim 1, wherein: 5. The optical pickup of claim 1 Symbol mounting, characterized in that corresponding to the phase change optical disc.