JPH11150323A - Composite optical element and manufacture thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a front-APC type composite optical element (laser coupler), which modifies detection efficiency of APC signal light and reduces stray light, and a method of manufacturing the optical element. SOLUTION: In a front-APC type laser coupler, an APC signal light passing- through region between a beam-emitting end face 10 of a prism 3 and a photo diode 5 for APC signal detection is closely adhered to the end face 10 with an optical material 11, which has a refractive index substantially equal with that of the prism 3 or a refractive index lower than that of the prism 3 and has a refractive index substantially equal with that of the material constituting the surface of the photo diode 5.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a composite optical element (laser coupler) used for an optical pickup and a method for manufacturing the same.

[0002]

2. Description of the Related Art In recent years, composite optical elements (laser couplers, hereinafter the same) as shown in FIGS. 17 and 18 have been developed as pickups for optical disks such as compact disks (CD) and laser vision disks (LVD). Has been put to practical use.

As shown in FIGS. 17 and 18, this composite optical element has a laser as a light emitting source on a silicon substrate 1 provided with photodiodes 4a and 4b for detecting recording signal light in a surface region. A laser coupler chip b having a diode 2 and a prism 45 mounted on the laser light emission side (front side) is housed in a flat package 49, for example.

The laser diode 2 is usually mounted on the silicon substrate 1 via a silicon chip 47 provided with a photodiode 48 having a pin junction structure in a surface region. The photodiode 48 provided on the silicon chip 47 is provided for controlling the output of the laser diode 2 and detects a laser beam emitted from the rear surface of the laser diode 2.

The laser light emitted from the front side of the laser diode 2 is reflected in a direction substantially perpendicular to the inclined end surface (beam split surface) 46 of the prism 45, and passes through a transparent cover glass 50 on the upper surface of a flat package 49.
The light is guided from the objective lens 8 to the signal recording surface of the optical disk 51. On the other hand, the light reflected by the signal recording surface of the optical disk 51 passes through the inclined end surface 46 of the prism 45 and
It passes through the inside and is detected by the photodiodes 4a and 4b.

In the composite optical element having such a configuration, the intensity of the laser light is monitored and controlled by a photodiode on the rear surface side (rear: rear) of the laser diode 2, so that the rear-APC ( Rear Auto-Power-Control
) Type composite optical element.

Here, the rear-APC type composite optical element b
Then, as shown in FIG. 17, a light absorbing film 44 is formed on the back side of the prism 45 for the purpose of reducing stray light which is one of the weak points of this element. That is, stray light in the composite optical element may enter the photodiode for signal detection or affect other optical components.

Therefore, in the composite optical element, by providing the light absorbing film 44 on the surface of the prism 45 opposite to the beam splitting surface 46, reflection and scattering of stray light into the prism can be prevented. Leakage of laser light outside the absorption film is reduced.

On the other hand, as shown in FIGS. 14 and 15, for the rear-APC type composite optical element, photodiodes (first light detectors) 4a and 4b for detecting read signal light are provided. A composite optical element has been developed in which a laser light source 2 and a prism 40 are mounted on a substrate (photodiode IC substrate) 1 having a photodiode (second photodetector) 5 for detecting the intensity of output signal light. I have.

The method of reading a signal from an optical disc in this composite optical element is basically the same as that of the above-described rear-APC type composite optical element, but the detection of the intensity of the laser beam and its control are performed on the front side of the laser diode 2. (front:
Front-APC (Front Auto-Power-Contro)
l) type composite optical element.

When the intensity of laser light emitted from the front surface of the laser diode 2 is detected and its output is controlled as in the front-APC type composite optical element,
Since the laser beam used for detecting the intensity signal is directly detected, more accurate and precise control can be performed.

In a composite optical element for magneto-optical recording that requires a higher laser output than a composite optical element of the rear-APC type used for an optical pickup for a CD, the reflectivity at the rear of the laser light source is increased. The structure of the rear-APC employed in the composite optical element for CD is directly applied to the composite optical element for magneto-optical recording. However, since the detection and control of the laser beam intensity cannot be performed accurately, the intensity of the laser beam transmitted from the prism is detected instead, and the output intensity of the laser beam is detected based on the detected intensity. A controlling front-APC is employed.

[0013]

Here, when considering the development to the front-APC type composite optical element, similarly to the above-mentioned rear-APC type composite optical element, how to generate stray light is also considered. A big issue is how to make it smaller.

However, in the front-APC type composite optical element, as shown in FIG. 16, similarly to the rear-APC type composite optical element, when a light absorbing film or an epoxy resin is formed on the back side of the prism. Since the optical path of the laser light (APC signal light) for detecting the output intensity is blocked, and the intensity of the APC signal light is difficult to be detected by the photodiode 5, a light absorbing thin film cannot be formed on the back surface of the prism.

For this reason, in the front-APC type composite optical element, as shown in FIGS. 14 and 15, a light transmitting film (AR coating) 43 is provided on the back surface 42 of the prism 40, and the output intensity is detected. Laser light (APC signal light)
Are transmitted through the light transmitting film 43 and detected along the path of prism → air → photodiode.

However, the surface region of the photodiode 5 is formed of a thin film such as a SiO ₂ film,
Due to the difference in the refractive index between air and the SiO ₂ film (the refractive index n of the SiO ₂ film with respect to air is about 1.5), the reflection of the APC signal light occurs on the surface of the photodiode 5 and the detection level thereof. And the detection efficiency (utilization efficiency) of the output intensity detecting photodiode tends to decrease.

Furthermore, the laser light reflected on the surface area of the photodiode 5 may enter the photodiodes 4a and 4b for detecting magneto-optical signals via reflection on a package or a cover glass, and may cause stray light. Is also a factor in the increase.

As described above, it is difficult to divert the technical measures for stray light reduction used in the rear-APC type composite optical element to the front-APC type composite optical element, and it is difficult to use the rear-APC type composite optical element. The stray light which has been overcome in the composite optical element is a major problem in the front-APC type composite optical element developed with the same concept.

The present invention has been made in view of the above-mentioned circumstances, and an object of the present invention is to provide a composite optical element such as the above-described front-APC type, which improves the detection efficiency of a light beam for detecting output intensity and further improves the efficiency. An object of the present invention is to provide a composite optical element capable of reducing stray light and a method for manufacturing the same.

[0020]

The inventor of the present invention has made intensive studies to solve the above-mentioned problems, and as a result, in the composite optical element such as the front-APC type having the above-mentioned structure, the output intensity detecting light beam ( By filling the passage area of APC signal light) with an optical material having specific optical properties,
It has been found that the detection efficiency of the light beam for output intensity detection in the intensity detection unit can be improved, and further, the stray light can be reduced.

That is, the present invention provides a light source section for emitting a light beam, a beam splitting surface for separating the light beam into a reflected light beam and a transmitted light beam, and at least one of the transmitted light beams on the main surface of the base. A prism having an emission end surface for emitting a part thereof, a first light detection unit substantially covered with the prism, and detecting a recording signal, and a first light detection unit not covered by the prism, and A composite optical element (hereinafter referred to as a front-to-back light detector) having a second light detector on the opposite side to the light source with respect to the light detector and detecting the output intensity of the transmitted light beam as the light beam for output intensity detection; In the APC-type composite optical element, the passage area of the output intensity detection light beam between the emission end face and the second light detection unit is substantially equal to the refractive index of the prism. Less than or equal to, and substantially filled with an optical material having a refractive index substantially equal to the refractive index of the surface material of the second light detection unit, Optical element (hereinafter referred to as the first element of the present invention)
Of the composite optical element. ).

According to the first composite optical element of the present invention, in the front-APC type composite optical element, the passage area of the output intensity detection light beam (APC signal light) is:
An optical material having a refractive index substantially equal to or less than the refractive index of the prism and having a refractive index substantially equal to the refractive index of the surface material of the second light detection unit. Therefore, it is possible to suppress the scattering and reflection of the output intensity detection light beam on the emission end face of the prism and to suppress the scattering and reflection of the output intensity detection light beam on the surface of the second light detection unit. Thus, it is possible to obtain a composite optical element having improved detection efficiency and reduced stray light.

Generally, in order to suppress the reflection at the material interface, for example, the wavelength of the light beam and the size (thickness) of the optical material, in addition to the material (particularly, the refractive index) of the optical material, are used. Has a lot to do with it. Therefore, in order to suppress the reflection at the emission end face and the reflection at the surface of the second detection unit, it is conceivable to change the wavelength, the size, and the like. Difficult because of the above or optical characteristics. On the other hand, according to the present invention, the above-mentioned effects can be obtained with a simple configuration by filling the passage area of the output intensity detection light beam with the optical material having the above-described optical characteristics.

The passing area is an area between the incident area of the output intensity detecting light beam on the back side of the prism and the surface area of the second light detecting section, and is substantially. This is an area through which the output intensity detection light beam (APC signal light) passes.

According to the present invention, a light source for emitting a light beam, a first light detector for detecting a recording signal, and a first light detector opposite to the light source are provided on the main surface of the base. A second light detection unit for detecting the output intensity of the light beam, and a beam splitting surface for separating the light beam into a reflected light beam and a transmitted light beam as an output intensity detection light beam. Further, the present invention provides a composite optical element (hereinafter, referred to as a second composite optical element of the present invention) having a prism covering the first light detection unit and the second light detection unit.

According to the second composite optical element of the present invention, a light source for emitting a light beam, a first light detector for detecting a recording signal, and the first light detector are provided on the main surface of the base. The second light detection unit that detects the output intensity of the light beam and the light beam are separated into a reflected light beam and a transmitted light beam as an output intensity detection light beam on the side opposite to the light source unit with respect to And has a prism that covers the first light detection unit and the second light detection unit, and processes the output intensity detection light beam in the prism. Obtaining a composite optical element capable of suppressing scattering and reflection of an output intensity detection light beam on the surface of the second light detection unit, improving detection efficiency of the output intensity detection light beam, and further reducing stray light. Can be.

Further, the present invention provides a light source section for emitting a light beam, a beam splitting surface for separating the light beam into a reflected light beam and a transmitted light beam, and at least one of the transmitted light beams on the main surface of the base. A prism having an emission end surface for emitting a part thereof, a first light detection unit substantially covered with the prism, and detecting a recording signal, and a first light detection unit not covered by the prism, and A second light detection unit that is located on the opposite side of the light source unit with respect to the light detection unit and that detects the output intensity of the transmitted light beam as an output intensity detection light beam; And a pass area of the output intensity detection light beam between the second light detection unit and the second light detection unit is substantially equal to or less than the refractive index of the prism, and Producing a composite optical element substantially filled with an optical material having a refractive index substantially equal to the refractive index of the surface material (ie, the first composite optical element of the present invention); At this time, a method of manufacturing a composite optical element (hereinafter referred to as a manufacturing method of the present invention), wherein a region where the output intensity detection light beam passes between the emission end face and the second light detection unit is filled with a resin serving as the optical material. ) Is provided.

According to the manufacturing method of the present invention, the first method of the present invention
When manufacturing the composite optical element of (1), the passage area of the output intensity detection light beam between the emission end face and the second light detection unit is formed by a resin serving as the optical material (for example, an adhesive satisfying the optical characteristics). ), It is possible to manufacture a composite optical element in which the detection efficiency of the output intensity detection light beam is improved and the stray light is reduced by a simple and economical method.

[0029]

DESCRIPTION OF THE PREFERRED EMBODIMENTS First, a first composite optical element of the present invention will be described.

According to the first composite optical element of the present invention, in particular, the refractive index of the prism is n ₁ , the refractive index of the optical material is n ₂ , and the refractive index of the surface material of the second light detecting section is n. n ₃
Then, n ₁ ≧ n ₂ and n ₂ ≒ n ₃ (that is, n ₁ ≧ n
An optical material (index-matched optical material) that satisfies the relationship of ₂ ≒ n ₃ ) is provided in the passing region. By filling (especially closely adhering) the passage area with the optical material whose refractive index is matched in this way, the use efficiency of the output intensity detection light beam in the second light detection unit is increased, and the stray light is reduced. Can be greatly contributed to. That is, regarding the relationship between n ₁ , n _2, and n ₃ , the emission efficiency of the output intensity detection light beam emitted from the prism (that is, the introduction efficiency to the light detection unit).
In consideration of the above, n ₁ ≧ n ₂ (most preferably n ₁ > n ₂ ). In order to suppress the reflection at the light detection unit for detecting the output intensity, it is necessary to set n 1 from the reflection coefficient of Fresnel. _Two
≧ n ₃ (most preferably n ₂ = n ₃ ).

Therefore, it is desirable that the optical material is substantially adhered to the prism and the surface material without passing through air. However, other substances may be slightly present within the range where the refractive index can be matched.

Further, an anti-reflection film may be provided on the exit surface side of the transmitted light beam in the prism, and the light exit surface of the anti-reflection film may form the exit end surface. That is, in the first composite optical element of the present invention, the prism and the second light detection unit may be directly adhered to each other with the optical material, but the prism may be disposed on the exit surface side of the prism. In order to suppress the reflection of the light beam, it is preferable that the antireflection film is provided. This antireflection film is formed of, for example, a dielectric multilayer film having different refractive indexes and film thicknesses, and needs to have an intermediate refractive index between the prism and the surface material of the second photodetector. It is.

In the first composite optical element of the present invention,
It is preferable that a resin having a refractive index substantially equal to a refractive index of a surface material of the second light detection unit is provided as the optical material. By providing a resin having a refractive index substantially equal to the refractive index of the surface material of the second light detection unit, reflection of the output intensity detection light beam at the second light detection unit is suppressed, and consequently stray light. Can be reduced.

As the resin, an adhesive resin for bonding the prism and the base may be used.
It may be a resin satisfying the above-mentioned optical characteristics. As the resin, for example, a refractive index of 1.
428 XE17-A3629 (trade name: manufactured by Toshiba Silicone Co., Ltd.).

It is preferable that the resin is covered with a light absorbing film. That is, stray light can be further reduced by providing a light absorbing film (absorbing material) on the resin provided in the area where the output intensity detection light beam passes.
As the light absorption film, specifically, a multilayer film of carbon and epoxy resin can be used.

In the first composite optical element of the present invention, an optical component having a refractive index substantially equal to the refractive index of the surface material of the second photodetector is fixed as the optical material. You may. In particular, it is desirable that the optical component is fixed with an adhesive resin having a refractive index substantially equivalent to the above. The material of the optical component may be, for example, the same material as the prism,
Any material that satisfies the above optical characteristics may be used.

In the optical component, a surface other than a region through which the output intensity detecting light beam passes may be a light reflecting surface. The light reflecting surface may be, for example, a light reflecting surface utilizing an interface between the optical component and air, or a light reflecting film may be provided. By making the surface other than the passing area a light reflecting surface, stray light can be reduced and the detection efficiency of the output intensity detection light beam in the second light detection unit can be improved.

Further, in the optical component, a surface other than the passing area may be covered with a light absorbing film. As the absorbing film, those described above may be used. By providing the light absorbing film, stray light can be further reduced.

Further, the first composite optical element of the present invention can be configured as a signal detection pickup of a magneto-optical recording medium such as an MD (mini disc). Generally, in a light beam detection pickup of a magneto-optical recording signal that requires a higher laser output than a composite optical element used for an optical pickup for a CD, the reflectivity at the rear of the light source is increased and the light is emitted from the front of the light source. The present invention is configured to increase the output of a light beam (especially a laser beam), and therefore, as in the present invention, a front-APC type composite for detecting and controlling the intensity of the output intensity detecting light beam at the front of the light source. An optical element is effective (the same applies to the second composite optical element of the present invention).

Next, the second composite optical element of the present invention will be described.

In the second composite optical element of the present invention,
The prism covers the first light detection unit and the second light detection unit, and is fixed to the base by an adhesive resin having a refractive index substantially equal to a surface material of the second light detection unit. Is desirable. Since it is fixed by such an adhesive resin, the reflection of the light beam on the surface portions of the first light detection unit and the second light detection unit is suppressed,
A composite optical element with less stray light and high detection efficiency in each detection unit can be formed.

Preferably, at least a part of a surface of the prism opposite to the beam splitting surface is inclined with respect to a main surface of the base. The inclined surface is preferably formed with an inclination such that the output intensity detecting light beam is focused on the second light detecting section.

In the second composite optical element of the present invention,
It is preferable that the output intensity detection light beam is configured to be incident on at least a part of the inclined surface. That is, the output intensity detection light beam may be directly input to the second light detection unit without passing through the inclined surface, but the output intensity detection efficiency is improved, and
For the purpose of reducing stray light, the output intensity detection light beam is collected by the second light detection unit so that the output detection light beam is incident on at least a part of the inclined surface, and the inclination of the inclined surface is adjusted. It is desirable to be configured to emit light.

Further, by making the surface of the prism opposite to the beam splitting surface an inclined surface, the light beam reflected on the fixing surface (or the substrate surface) of the prism,
Reflected light in the prism that passes through the lower part of the fixed surface of the prism (in general, various reflections occur inside the prism,
The light finally passing through the lower part of the back surface of the prism) can also be guided to the second light detection unit,
The detection efficiency of the APC signal light in the light detection unit can be further improved.

The inclined surface may be a light reflecting surface, and the light reflecting surface may be a reflecting surface utilizing a difference in refractive index at the interface, or a light reflecting film may be provided. You may. With this light reflecting surface, the detection efficiency of the output intensity detection light beam in the second light detection unit can be further improved, and stray light can be further reduced. The light reflection film is, for example, a TiO ₂ / Si having a 20-layer structure.
It may be a multilayer film composed of O ₂ / TiO ₂ ... / SiO ₂ / TiO ₂ .

Further, the inclined surface may be covered with a light absorbing film. The same light absorbing film as described above can also be used for this light absorbing film, whereby stray light can be further reduced.

Further, it is desirable that an incident area of the output intensity detection light beam on the inclined surface is a light reflecting surface, and the other region is covered with a light absorbing film. That is, the output intensity detection light beam incident on the incident area is reflected and input to the second light detection unit, and further, by providing a light absorbing film in the other area, stray light reduction and detection efficiency are reduced. Improvement is achieved at a high level.

Further, in the second composite optical element of the present invention, a bulging portion having the inclined surface is formed so as to cover the second light detecting portion for the purpose of reducing stray light and improving detection efficiency. The surface of the prism, including the surface of the bulging portion, on the side opposite to the beam splitting surface may be covered with a light absorbing film. Furthermore, the surface of the bulging portion may be a light reflecting surface, and a surface of the prism opposite to the beam splitting surface except for the bulging portion may be covered with a light absorbing film.

Next, the manufacturing method of the present invention will be described.

In the manufacturing method of the present invention, the optical material can be formed by using an adhesive resin for adhering the prism and the base as the resin, and utilizing a protruding portion of the adhesive resin. . That is, the optical material can be formed by previously providing a predetermined amount of the adhesive resin on the fixing surface of the prism or the upper surface of the base, without requiring a procedure for separately providing the resin. Can be. Further, the optical material may be formed by attaching (potting) the resin. Note that the same resin as described above may be used as the resin.

Further, an anti-reflection film may be provided on the exit surface side of the transmitted light beam in the prism, and the light exit surface of the anti-reflection film may be the exit end surface. As described above, by providing the anti-reflection film, it is possible to suppress reflection of the output intensity detection light beam of the prism on the emission surface.

Further, in the manufacturing method of the present invention, if the resin is covered with a light absorbing film, stray light can be further reduced. This light absorbing film may be the same absorbing film as described above.

Next, the present invention will be described according to preferred embodiments.

[First Embodiment] A composite optical element (hereinafter, sometimes referred to as a laser coupler) according to a first embodiment of the present invention will be described with reference to FIGS.

As shown in FIGS. 1A and 2, in the laser coupler A according to the present embodiment, a laser diode 2 which is a light source for outputting a laser beam is connected to a silicon substrate 1 via a chip (pedestal) 12. Attached to the main surface 9.
In addition, a light beam for detecting output intensity (hereinafter referred to as A
The laser light is separated into a transmitted laser beam (indicated by a solid line in the figure) as a PC signal light and a reflected laser beam (indicated by a dotted line in the figure) for obtaining an information signal from an optical disk (not shown) via the objective lens 8. Beam splitting surface 6 and APC
A prism 3 having an emission end face 10 for emitting at least a part of the signal light is attached. Further, an antireflection film 7 is provided on the emission end face 10 of the prism 3 for the purpose of preventing the reflection of the APC signal light into the prism 3 (omitted in FIG. 2).

The prism 3 is a prism made of a birefringent material such as KTP (KTiOPO ₄ ) or LN (LiNbO ₃ ) in the case of a pickup for a magneto-optical recording medium. It may be a quartz glass prism formed of an isotropic material.

Further, on the main surface 9 of the silicon substrate 1, photodiodes 4 a and 4 b as first light detecting portions for detecting a recording signal light beam indicated by dotted lines in the drawing are provided at positions covered by the prism 3. The detection of the output intensity of the APC signal light (solid line in the figure) is provided at a position which is not covered by the prism 3 and which is opposite to the laser diode 2 with respect to the photodiodes 4a and 4b. A photodiode 5 is provided.

In the laser coupler according to the present embodiment, the prism 3 (substantially, between the emitting end face 10 of the prism 3 (substantially, the surface of the antireflection film 7) and the photodiode 5 is provided. In order to prevent the reflection of the APC signal light on the emission end face 10 of the anti-reflection film 7) and the reflection on the surface of the photodiode 5, and to improve the detection efficiency thereof, the passing area of the APC signal light (hereinafter, referred to as The adhesive resin 11 is filled so as to include an optical path.

Here, in the laser coupler according to the present embodiment, the refractive index of the prism 3 is n ₁ , the refractive index of the adhesive resin 11 is n ₂ , the surface material of the photodiode 5 (Si
Assuming that the refractive index of O ₂ ) is n ₃ , n ₁ = about 1.75 (non-linear optical crystal prism) n ₂ = 1.428 (silicone resin) n ₃ = about 1.5 (SiO ₂ thin film) since, (substantially equivalent to the n ₂ and n ₃₎ that APC signal reflection light can be sufficiently suppressed at each material interface. Further, the interface between the adhesive resin 11 and air serves as a reflecting surface due to the difference in the refractive index, and the reflected light of the APC signal light is returned to the photodiode 5 again at this interface. The detection efficiency can be further increased. In particular, compared to the laser coupler a shown in FIG.
The detection efficiency of the C signal light is improved by 20 to 50%, and the stray light can be reduced by 20 to 50%.

As shown in FIG. 1B and FIG. 2, the adhesive resin 11a may be provided so as to have substantially the same width as the width of the prism 3, but as shown in FIG. 11b
May be provided so as to cover at least the surface region of the photodiode 5. Although not shown, there is no problem even if the adhesive resin protrudes to the side surface of the prism 3 or the like, because it does not hinder the optical path of the APC signal light or the optical path of another light beam.

Here, photodiodes (first photodetectors) 4a and 4 for obtaining information signals from the magneto-optical disk
The operation of b will be described.

The laser coupler according to the present embodiment uses the aforementioned birefringent prism and utilizes a magneto-optical phenomenon called the Kerr effect. That is, as shown in FIG. 2 (B), the laser beam emitted from the laser diode 2 and whose deflection direction is appropriately controlled is reflected by the beam splitting surface 6 of the birefringent prism 3, and the magneto-optical disk not shown When the reflected laser light reflected by the signal recording surface of the disk is made incident on the birefringent prism 3 from the beam splitting surface 6, the reflected laser light is applied to the photodiode 4b as shown in the figure. Thus, the light is separated into ordinary light that obeys Snell's law and extraordinary light that does not obey Snell's law, and a magneto-optical signal can be obtained from the difference between these two components.

That is, the regions a to d in the photodiode 4a and the regions l _x to l in the photodiode 4b.
By performing predetermined arithmetic processing for the detection signals detected by l _z and region j _x to j _z, a focus signal, a tracking signal, a read signal by the read signal and magneto-optical effect by the reading signal (normal signal pit Inclusive) can be detected. Therefore, in an optical pickup using this laser coupler, for example, MD
It is possible to apply to a system corresponding to both a normal pit disk and a magneto-optical disk like a (mini disk) system. In the signal detection system having such a configuration, the interval t ₂ between the extraordinary light and the ordinary light in the photodiode 4b is usually t ₂ = 55 μm or less, and the interval t ₁ between the centers is usually t ₁ = 85 μm. It is as follows.

Next, a method of manufacturing a laser coupler according to the present embodiment will be described with reference to FIG.

First, as shown in FIG. 3 (A), an adhesive resin 11c which satisfies the above-mentioned optical characteristics is provided on the bottom surface of the prism 3.
Is applied. Here, this adhesive resin is applied more than usual.

Next, as shown in FIG. 3B, the lower end of the prism 3 on the side of the beam splitting surface 6 is placed at a predetermined position on the main surface 9 of the silicon substrate 1 on which the photodiodes 4a, 4b and 5 are provided. Make contact. At this time, it is desirable that the adhesive resin 11d does not protrude to the beam split surface 6 side.

Next, the prism 3 is gradually lowered with respect to the main surface 9 around the end (in the direction of the arrow x in the figure).
As shown in FIG. 3C, the adhesive resin 11e
The surface of the photodiode 5 is covered so as to include the optical path of the PC signal light. As described above, the adhesive resin 11e may protrude from the side surface of the prism 3; however, the protruding portion of the adhesive resin may be removed after the prism 3 is bonded, or the side surface portion may be exposed to laser light. Since they are not substantially involved, they may be left as they are from the viewpoint of maintaining the adhesive strength between the prism 3 and the substrate 1.

As described above, according to the present embodiment, the utilization efficiency of the APC signal light is high by a simple method using the protruding portion of the adhesive resin for bonding the prism 3 and the substrate 1, and A laser coupler with less stray light can be configured. In addition to the above method, for example, the prism 3 is fixed to the substrate 1 in advance, and then the adhesive resin is attached.
It may be formed by a method such as coating and potting.

[Second Embodiment] With reference to FIG. 4, a composite optical element according to a second embodiment of the present invention will be described.

As shown in FIG. 4A, the laser coupler B according to the present embodiment has the first configuration except that a resin (resin other than the adhesive resin) 15 that satisfies the above-described optical characteristics is used as the optical material. The configuration is basically the same as that of the laser coupler A according to the embodiment.

That is, the emission end face 10 of the prism 3 (substantially the surface of the antireflection film 10) and the photodiode 5
Is filled with the resin 15 so that the reflection of the APC signal light on the exit end face 10 of the prism 3 and the surface of the photodiode 5 can be suppressed, thereby reducing stray light and reducing the APC signal light. The improvement of the use efficiency of the signal light can be satisfied at the same time. Also, as in the first embodiment, the interface between the resin 15 and air serves as a reflecting surface due to the difference in the refractive index.
Since the reflected light of the C signal light is returned to the photodiode 5 again, the detection efficiency of the photodiode 5 can be further increased.

In this embodiment, FIG.
4B, the resin 15a only needs to cover at least the area where the APC signal light passes, that is, the surface area of the photodiode 5, and as shown in FIG. May be provided. This resin can be formed, for example, based on a technique such as so-called potting in which the resin is disposed in a selected area.

[Third Embodiment] Referring to FIG. 5, a composite optical element according to a third embodiment of the present invention will be described.

The laser coupler C according to the present embodiment uses a triangular prism-shaped optical component (for example, made of quartz glass) that satisfies the optical characteristics as shown in FIG. Unless used,
This is basically the same as the laser coupler A according to the first embodiment.

That is, the emission end face 10 of the prism 3 (substantially the surface of the antireflection film 10) and the photodiode 5
As shown in FIG. 5 (B), the optical component 16 is closely attached to the area where the APC signal light passes between the light source and the APC signal light. Therefore, it is possible to simultaneously reduce the stray light and improve the use efficiency of the APC signal light. Similarly to the first embodiment, the interface 17 between the optical component 16 and air serves as a reflecting surface due to the difference in the refractive index, and the interface (light reflecting surface) 17
Since the reflected light of the APC signal light is returned to the photodiode 5 again, the detection efficiency of the photodiode 5 can be further increased.

In this embodiment, FIG.
As shown in FIG. 4C, it is sufficient that the optical component 16a is filled at least in the area where the APC signal light passes, that is, the surface area of the photodiode 5 is covered. As shown in FIG. 16b may be in close contact with the prism 3 so as to have substantially the same width.

[Fourth Embodiment] Referring to FIG. 6, a composite optical element according to a fourth embodiment of the present invention will be described.

The laser coupler D according to the present embodiment covers the adhesive resin that fills the area where the APC signal light passes in the laser coupler A according to the first embodiment with a light absorbing film.

That is, the emission end face 10 of the prism 3 (substantially the surface of the antireflection film 10) and the photodiode 5
After securing the optical path of the APC signal light between the protrusions of the adhesive resin and fixing the prism 3, the surface opposite to the beam splitting surface 6 (substantially, the antireflection film 10 and the adhesive resin Since the light absorbing film 19 is formed by applying an absorbing agent to the surface of the APC signal light 18, the reflection of the APC signal light on the exit end face 10 of the prism 3 and the surface of the photodiode 5 is suppressed, and the APC signal light is reduced. It is possible to obtain a laser coupler that realizes improvement in light use efficiency and further reduction of stray light.

[Fifth Embodiment] With reference to FIG. 7, a composite optical element according to a fifth embodiment of the present invention will be described.

The laser coupler E according to the present embodiment is a resin (a resin other than the adhesive resin) that fills the area where the APC signal light passes in the laser coupler B according to the second embodiment.
Is covered with a light absorbing film.

That is, the emission end face 10 of the prism 3 (substantially the surface of the antireflection film 10) and the photodiode 5
The optical path of the APC signal light between the two is filled with, for example, a potted resin, and the surface opposite to the beam splitting surface 6 (substantially, the surfaces of the antireflection film 10 and the resin 20)
The light absorbing film 21 is formed by applying an absorbent to the
It is possible to obtain a laser coupler that suppresses the reflection of the C signal light on the emission end face 10 of the prism 3 and the surface of the photodiode 5, thereby improving the use efficiency of the APC signal light and further reducing stray light.

[Sixth Embodiment] A composite optical element according to a sixth embodiment of the present invention will be described with reference to FIG.

The laser coupler F according to the third embodiment is similar to the third embodiment except that a rectangular parallelepiped optical component (for example, made of quartz glass) having a light absorbing film that satisfies the above-described optical characteristics is used. Is basically the same as that of the laser coupler C.

That is, the emission end face 10 of the prism 3 (substantially the surface of the antireflection film 10) and the photodiode 5
As shown in FIG. 8B, an optical component 22 having a surface other than a part of the optical path of the APC signal light covered with a light absorbing film 23 is provided in a region where the APC signal light passes between the two. Because of the close contact, the exit end face 10 of the prism 3 of the APC signal light
And the reflection on the surface of the photodiode 5 is suppressed.
It is possible to obtain a laser coupler that satisfies both the improvement of the use efficiency of the PC signal light and the further reduction of the stray light.

In this embodiment, FIG.
As shown in FIG. 8C, it is sufficient that the optical component 22a is at least filled in the area where the APC signal light passes, that is, the surface area of the photodiode 5 is covered. As shown in FIG. The prism 22b may be in close contact with the prism 3 so as to have substantially the same width.

The composite optical elements according to the first to sixth embodiments correspond to the first composite optical element according to the present invention, and the composite optical elements according to the following seventh to sixth embodiments are described. The composite optical element according to the eleventh embodiment corresponds to the second composite optical element of the present invention.

[Seventh Embodiment] With reference to FIG. 9, a composite optical element according to a seventh embodiment of the present invention will be described.

In the laser coupler G according to the present embodiment, as shown in FIG. 9A, a laser diode 2 which is a light source for outputting a laser beam is provided on a main surface 9 of a silicon substrate 1 via a chip (pedestal) 12. The main surface 9 has a transmitted laser beam (shown by a solid line in the figure) as an APC signal beam and a reflected laser beam for obtaining an information signal from an optical disc (not shown) via the objective lens 8. (Shown by a dotted line in the figure), a prism 24 having a beam splitting surface 25 and an inclined surface 26 whose surface opposite to the beam splitting surface is inclined with respect to the main surface 9 is attached. I have. However, a light reflecting film 27 is provided on the inclined surface 26 of the prism 27 for the purpose of condensing the APC signal light on the photodiode 5 and increasing its use efficiency (detection efficiency).

On the main surface 9 of the silicon substrate 1, the photodiodes 4a and 4b as the first light detecting portions for detecting the recording signal light beam indicated by the dotted lines in the drawing are provided at positions covered by the prism 24. , This photodiode 4
At a position opposite to the laser diode 2 with respect to a and 4b, a photodiode 5 for detecting the output intensity of the APC signal light (solid line in the figure) is provided.

That is, the laser coupler G according to the present embodiment is a laser coupler having the prism 24 formed so as to process the APC signal light in the prism.
The incident laser light incident from the beam splitting surface 25 is A
It can be directly monitored as PC signal light, and the refractive index of the prism 25 is substantially equal to or higher than the refractive index of the surface material of the photodiode 5 (particularly, the refractive index of the prism is n ₄ , and the refractive index of the surface material is n ₄₎ . If the rate and n _5,
n ₄ ≧ n ₅ is desirable. ), The reflection of the APC signal light on the surface of the photodiode 5 is suppressed to reduce stray light, and the detection efficiency is improved.

In this embodiment, the light reflecting film 27 is provided on the inclined surface 26 of the prism 24. However, even if no light reflecting film is provided, the refractive index of the prism 24 and the external The inclined surface 26 can be used as a reflecting surface depending on the difference in the refractive index.

Also, as shown in FIG. 9B, the prism in the present embodiment may be formed such that the inclined surface 26a has substantially the same width as the width of the prism 24.
As shown in FIG. 9C, the inclined surface 26b may be formed so as to cover at least the surface region of the photodiode 5.

[Eighth Embodiment] A composite optical device according to an eighth embodiment of the present invention will be described with reference to FIG.

The laser coupler H according to the present embodiment is basically the same as the laser coupler G according to the seventh embodiment except that a light absorbing film is provided instead of the light reflecting film.

That is, not only the photodiodes 4a and 4b but also the photodiode 5 for detecting the APC signal light is covered by the prism 24, and the prism 24 covers the inside of the prism 24, that is, without passing through other substances (for example, air). Since the APC signal light is processed, the reflection of the APC signal light on the surface of the photodiode 5 is suppressed, and the detection efficiency is improved. Further, since the light absorbing film 26 is provided on the inclined surface 26 of the prism 24, it is possible to further reduce stray light.

The absorption film 28 is used to improve the detection efficiency of the APC signal light at the photodiode 5.
The refractive index of the prism 24 is adjusted to match the refractive index (in) so as to have some reflectance for the incident APC signal light.
dex-matching) It is desirable that the membrane has slightly shifted conditions.

[Ninth Embodiment] A composite optical element according to a ninth embodiment of the present invention will be described with reference to FIG.

The laser coupler I according to the present embodiment is basically the same as the laser coupler H according to the eighth embodiment except that a light absorbing film (or light reflecting surface) is provided on a part of the light reflecting film. It is a laser coupler.

That is, not only the photodiodes 4a and 4b but also the photodiode 5 for detecting the APC signal light is covered by the prism 24, and the prism 24 covers the inside of the prism 24, that is, without passing through other substances (for example, air). Since the APC signal light is processed, reflection of the APC signal light on the surface of the photodiode 5 is suppressed, stray light is reduced, and the detection efficiency is improved.

Further, on the inclined surface 26 of the prism 24,
The light reflection film 29 (or light reflection surface) is provided in the incident area of the APC signal light, and the light absorption film 30 whose refractive index is matched so as to absorb all the reflected light is provided in other areas. It is possible to further improve detection efficiency and reduce stray light.

[Tenth Embodiment] Referring to FIG.
A composite optical element according to a tenth embodiment of the present invention will be described.

The laser coupler J according to the present embodiment is basically the same as the laser coupler G according to the seventh embodiment except that the shape of the prism is changed.

That is, not only the photodiodes 4a and 4b but also the photodiode 5 for detecting the APC signal light is covered by the prism 31, so that the prism 31 does not pass through the inside of the prism 31, that is, without passing through other substances (for example, air). Since the APC signal light is processed, the reflection of the APC signal light on the surface of the photodiode 5 is suppressed to reduce stray light, and at the same time, the detection efficiency is improved. Further, since the light absorbing film 30 is provided on the inclined surface 38 on the back surface 33 side of the prism 31, it is possible to further reduce stray light.

Note that the prism 31 according to the present embodiment is
As shown in FIG. 12B, an inclined surface 38 is provided on the back surface 33 side.
The swelling portion 35 having the swelling portion 35 is provided.
Is configured to cover the photodiode 5. Further, as shown in FIG. 12C, the bulging portion 35a of the prism 31a may be formed to have substantially the same width as the width of the prism 31a.
As shown in FIG. 2 (D), it is sufficient that the bulging portion 35b of the prism 31b is formed so as to cover at least the surface area of the photodiode 5.

In order to improve the detection efficiency of the photodiode 5, the light absorbing film 30 has a refractive index different from that of the prism 31 so that the light absorbing film 30 has a slight reflectance with respect to the incident APC signal light. Index-matchin
g) It is desirable for the film to have slightly different conditions.

[Eleventh Embodiment] Referring to FIG.
A composite optical element according to an eleventh embodiment of the present invention will be described.

The laser coupler K according to the present embodiment is basically the same as the laser coupler J according to the tenth embodiment except that a light reflecting film (or light reflecting surface) is introduced in a part of the light absorbing film. It is a laser coupler.

That is, not only the photodiodes 4a and 4b but also the photodiode 5 for detecting the APC signal light are covered by the prism 31, and the prism 31 covers the inside of the prism 31, that is, without passing through other substances (for example, air). Since the APC signal light is processed, the reflection of the APC signal light on the surface of the photodiode 5 is suppressed, stray light is reduced, and the detection efficiency of the APC signal light is improved.

Further, the light reflection film 36 (or light reflection surface) and the other rear surface 33 are provided on the surface of the bulging portion 36 on the rear surface 33 side of the prism 31, that is, on the incident area of the APC signal light.
Since the surface region is provided with the light absorbing film 37 whose refractive index is matched so as to absorb all the reflected light, it is possible to further improve the detection efficiency and reduce the stray light.

As described above, according to the various embodiments of the present invention, the optical path of the APC signal light that does not particularly pass through the air is formed, that is, the beam split surface of the prism → resin, the optical component, or the like. Since the optical path from the prism to the photodiode (SiO ₂ film) is formed, the reflection of the APC signal light on the surface of the photodiode 5 is suppressed, stray light is reduced, and the detection efficiency of the APC signal light is improved. A coupler can be obtained.

The embodiment in which the present invention is applied to the laser coupler used in the optical pickup for the magneto-optical disk has been described above. However, the present embodiment can be applied to the optical pickup of another optical disk. The present invention can also be applied to a composite optical element for optically reading information from an information recording medium other than a disk such as a disk or an optical card.

Further, a light absorbing film or a light reflecting film (or a light reflecting film or a light reflecting film) is formed on the side surface of the prism or the like for the purpose of reducing stray light as long as the light beam for detecting the output intensity or the light beam for detecting the recording signal is not affected. Surface) may be provided.

[0114]

According to the first composite optical element of the present invention, in the composite optical element such as the front-APC type, the refractive index of the prism is substantially equal to or smaller than the refractive index of the prism in the area where the APC signal light passes. Since it is less than that and is filled with an optical material having a refractive index substantially equal to the refractive index of the surface material of the second photodetector, the APC signal light at the emission end face of the prism is It is possible to suppress the scattering and reflection, and at the same time, suppress the scattering and reflection of the APC signal light on the surface of the second light detection unit, thereby improving the detection efficiency of the APC signal light and obtaining a composite optical element with reduced stray light. be able to.

According to the second composite optical element of the present invention, the light source for emitting a light beam, the first light detector for detecting a recording signal, and the first light detector are provided on the main surface of the base. A second light detection unit for detecting the output of the light beam and the light beam, and a reflected light beam and an AP
A prism having a beam splitting surface for splitting into a transmitted light beam as a C signal light, and covering the first light detection unit and the second light detection unit; Since the signal light is processed, scattering and reflection of the APC signal light on the surface of the second light detection unit can be suppressed, the detection efficiency of the APC signal light is improved, and a composite optical element with reduced stray light is obtained. Can be.

According to the manufacturing method of the present invention, the first method of the present invention
When manufacturing the composite optical element of the above, since the passage area of the APC signal light between the emission end face and the second light detection unit is filled with the resin serving as the optical material, the method is simple and economical. It is possible to provide a composite optical element in which the resin serving as the optical material is brought into close contact with the passage area, the detection efficiency of APC signal light is improved, and stray light is reduced.

[Brief description of the drawings]

FIG. 1 is a schematic side view (A), a schematic top view (B), and another schematic top view (C) of a composite optical element according to a first embodiment of the present invention.

FIG. 2 is a schematic perspective view (A) of the composite optical element according to the first embodiment, and is a schematic view (B) of a main part of a photodetector of the same.

FIG. 3 is a schematic side view illustrating the method for manufacturing the composite optical element according to the first embodiment.

FIG. 4 is a schematic side view (A), a schematic top view (B), and another schematic top view (C) of the composite optical element according to the second embodiment.

FIG. 5 is a schematic side view (A), another schematic side view (B), a schematic top view (C), and another schematic top view (D) of the composite optical element according to the third embodiment. .

FIG. 6 is a schematic side view of the composite optical element according to the fourth embodiment.

FIG. 7 is a schematic side view of the composite optical element according to the fifth embodiment.

FIG. 8 is a schematic side view (A), another schematic side view (B), a schematic top view (C), and another schematic top view (D) of the composite optical element according to the sixth embodiment. .

FIG. 9 is a schematic side view (A), a schematic top view (B), and another schematic top view (C) of the composite optical element according to the seventh embodiment.

FIG. 10 is a schematic side view of the composite optical element according to the eighth embodiment.

FIG. 11 is a schematic side view of the composite optical element according to the ninth embodiment.

FIG. 12 is a schematic side view (A), another schematic side view (B), a schematic top view (C), and another schematic top view (D) of the composite optical element according to the tenth embodiment. .

FIG. 13 is a schematic side view of the composite optical element according to the eleventh embodiment.

FIG. 14 is a schematic side view of a conventional front-APC composite optical element.

FIG. 15 is a schematic perspective view of the front-APC type composite optical element.

FIG. 16 is a schematic side view when a partial structure of a conventional rear-APC type composite optical element is applied to a front-APC type composite optical element.

FIG. 17 is a schematic side view showing a housed state and operation of a conventional rear-APC type composite optical element.

FIG. 18 is a schematic perspective view of the rear-APC composite optical element.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Substrate, 2 ... Light source (laser light source), 3, 24, 31, 31a, 31b, 40, 45 ... Prism, 4a, 4b ... Photodiode (1st light detection part), 5 ... Photodiode (2nd light) 6, 25, 32, 41, 46: Beam splitting surface, 7, 43: Antireflection film, 8: Objective lens, 9: Main surface, 10, 42: Outgoing end surface, 11, 11a, 11b, 11c , 11d, 11e, 18
... Adhesive resin, 12 ... Chip, 15, 15a, 15b, 20 ... Resin, 16, 16a, 16b, 22, 22a, 22b ... Optical components, 17, 29, 36 ... Mirror surface (light reflecting surface), 19, 21, 23, 28, 30, 34, 37, 44: light absorbing film, 26, 26a, 26b, 38: inclined surface, 33: prism back surface, 35, 35a, 35b: bulging portion, 47: silicon chip, 48 ... photodiode, 49 ... flat package, 50 ... transparent cover glass

Claims (27)

[Claims] 1. A light source unit for emitting a light beam, a beam splitting surface for separating the light beam into a reflected light beam and a transmitted light beam, and at least a part of the transmitted light beam, A prism having an emission end face to be irradiated, a first light detection unit substantially covered by the prism and detecting a recording signal, and a first light detection unit not covered by the prism and A composite optical element having a second light detection unit on the opposite side to the light source unit for detecting an output intensity of the transmitted light beam as an output intensity detection light beam, wherein the emission end face and the second A passage area of the output intensity detection light beam between the light detection unit and the light intensity detection light beam is substantially equal to or less than the refractive index of the prism, and the refraction of the surface material of the second light detection unit. Characterized in that it is substantially filled with a substantially optical material having the same refractive index as the composite optical element. 2. The composite optical element according to claim 1, wherein the optical material is in close contact with the prism and the surface material without passing through air. 3. The composite optics according to claim 1, wherein an anti-reflection film is provided on an exit surface side of the transmitted light beam in the prism, and a light exit surface of the anti-reflection film forms the exit end surface. element. 4. The composite optical element according to claim 1, wherein a resin having a refractive index substantially equal to a refractive index of a surface material of the second light detection unit is provided as the optical material. 5. The composite optical element according to claim 4, wherein said resin is an adhesive resin for bonding said prism and said base. 6. The resin is covered with a light absorbing film.
The composite optical element according to claim 4. 7. The composite optical element according to claim 1, wherein an optical component having a refractive index substantially equal to a refractive index of a surface material of the second light detection unit is fixed as the optical material. 8. The composite optical element according to claim 7, wherein the optical component is fixed by an adhesive resin having a refractive index substantially equal to the optical component. 9. The composite optical element according to claim 7, wherein a surface of the optical component other than a region where the output intensity detection light beam passes is a light reflecting surface. 10. The composite optical element according to claim 7, wherein a surface of the optical component other than a region through which the output intensity detection light beam passes is covered with a light absorbing film. 11. The composite optical element according to claim 1, wherein the composite optical element is configured as a pickup for detecting a signal of a magneto-optical recording medium. 12. A light source unit for emitting a light beam, a first light detection unit for detecting a recording signal, and a light source unit on the opposite side of the first light detection unit from the light source unit. A second light detection unit for detecting the output intensity of the light beam and a beam split surface for separating the light beam into a reflected light beam and a transmitted light beam as an output intensity detection light beam, and A composite optical element having a prism covering the first light detection unit and the second light detection unit. 13. The composite optical element according to claim 12, wherein said prism is fixed to said base by an adhesive resin having a refractive index substantially equal to a surface material of said second light detection unit. 14. The composite optical element according to claim 12, wherein at least a part of a surface of said prism opposite to said beam splitting surface is inclined with respect to a main surface of said base. 15. The composite optical element according to claim 14, wherein the output intensity detection light beam is configured to be incident on at least a part of the inclined surface. 16. The composite optical element according to claim 15, wherein said inclined surface is a light reflecting surface. 17. The composite optical element according to claim 15, wherein said inclined surface is covered with a light absorbing film. 18. The composite optical element according to claim 15, wherein the incident area of the output intensity detection light beam on the inclined surface is a light reflecting surface, and the other region is covered with a light absorbing film. 19. A method for covering the second photodetector,
The composite optical element according to claim 12, further comprising a prism on which a bulged portion having the inclined surface is formed. 20. The composite optical element according to claim 19, wherein a surface of the prism, including a surface of the bulging portion, on a side opposite to the beam splitting surface is covered with a light absorbing film. 21. A surface of the bulging portion is a light reflecting surface,
20. The composite optical element according to claim 19, wherein a surface of the prism opposite to the beam split surface except for the bulging portion is covered with a light absorbing film. 22. The composite optical element according to claim 12, wherein the composite optical element is configured as a pickup for detecting a signal of a magneto-optical recording medium. 23. A light source unit for emitting a light beam, a beam splitting surface for separating the light beam into a reflected light beam and a transmitted light beam, and at least a part of the transmitted light beam. A prism having an emission end face to be irradiated, a first light detection unit substantially covered by the prism and detecting a recording signal, and a first light detection unit not covered by the prism and A composite optical element having a second light detection unit on the opposite side to the light source unit for detecting an output intensity of the transmitted light beam as an output intensity detection light beam, wherein the emission end face and the second A passage area of the output intensity detection light beam between the light detection unit and the light intensity detection light beam is substantially equal to or less than the refractive index of the prism, and the surface material of the second light detection unit is bent. When manufacturing a composite optical element characterized by being substantially filled with an optical material having a refractive index substantially equal to the refractive index, the distance between the emission end face and the second light detection unit A method of manufacturing a composite optical element, wherein a passage area of an output intensity detection light beam is filled with a resin serving as the optical material. 24. The manufacturing of the composite optical element according to claim 23, wherein an adhesive resin for bonding the prism and the base is used as the resin, and the optical material is formed by a protruding portion of the adhesive resin. Method. 25. The method according to claim 23, wherein the optical material is formed by attaching the resin. 26. The method of manufacturing a composite optical element according to claim 23, wherein an anti-reflection film is provided on the emission surface side of the transmitted light beam in the prism, and a light emission surface of the anti-reflection film is used as the emission end surface. . 27. The method according to claim 23, wherein the resin is covered with a light absorbing film.