JPH0636338A - Optical pickup - Google Patents

Abstract

PURPOSE:To efficiently lead reflected light into a photodetector without using an adhesive by providing a prescribed space between a prism and the photodetector. CONSTITUTION:The laser light from a laser diode chip 14 of an optical pickup 30 of a copying element is reflected by a semiconductor film M1 of a prism 18 and is thrown to an optical disk or the like. The reflected light from the optical disk or the like is transmitted through the film M1 and is reflected by films M3 and M2 and is made incident on photodetectors 22 and 24. A prescribed gap is formed between the prism 18 and photodetectors 22 and 24 and the refractive index of this gap space is about one; and when the prism 18 is made of an optical member having a low refractive index, the critical angle which reflects disturbing light is obtained, and the optical pickup where only reflected light is efficiently led into photodetectors without using an adhesive is obtained.

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 an optical disk device, and more particularly to miniaturization of the optical pickup.

[0002]

2. Description of the Related Art Conventionally, in some optical disk devices such as compact disk players, a light emitting element and a light receiving element are integrated to form an optical pickup.

As shown in FIG. 2, in this type of optical pickup 1, the composite element 2 forms a light beam L1.
The light beam L1 is condensed on the optical disc 6 by the objective lens 4.

Further, in the optical pickup 1, the reflected light beam L2 reflected by the optical disk 6 is received by the objective lens 4, and the reflected light beam L2 is guided to the composite element 2.

As shown in FIGS. 3 and 4, the composite element 2
Is an optical block 8 in which a light emitting element and a light receiving element are integrated.
And the optical block 8 is housed in a semiconductor package.

In this optical block 8, a second semiconductor substrate 12 is mounted on a first semiconductor substrate 10, and a laser diode chip 14 is mounted on this second semiconductor substrate 12.

Of these, the optical block 8 has a second
A light receiving element 16 is formed on the semiconductor substrate 12, and the light receiving element 16 receives the light beam emitted from the rear of the laser diode chip 14.

As a result, the optical block 8 can monitor the light quantity of the light beam L1 emitted from the laser diode 14 based on the output signal of the light receiving element 16.

The optical block 8 has a trapezoidal prism 18 arranged in front of the laser diode chip 14, that is, on the first semiconductor 10, and emits a light beam L1 emitted from the front of the laser diode chip 14. The light is reflected by the slope of the prism 18 and emitted upward.

As a result, the optical block 8 emits the light beam L1 through the transparent sealing member (not shown) arranged on the upper surface of the semiconductor package.

Further, the optical block 8 is an optical disc 18
The reflected light beam L2 reflected by is incident on the inclined surface of the prism 18, where the reflected light beam L2 is guided inside the prism 18 and reflected by the bottom surface L and the upper surface U, respectively.

At this time, the prism 18 efficiently reflects the light beam L1 and efficiently guides the reflected light beam L2 to the inside. Therefore, a semi-transmissive film M1 is formed on the slope and the reflected light beam L2 guided to the inside is formed. In order to reflect efficiently, the total reflection film M2 is formed on the upper surface U.

Further, the prism 18 has a predetermined adhesive layer 2
The lower surface L is adhered to the semiconductor substrate 10 via 0, and the reflected light beam L2 incident from the slope in this state is first reflected on the lower surface L, then reflected on the upper surface U, and then reaches the lower surface L. ing.

At this time, the optical block 8 includes the objective lens 4
The upper surface U and the reference position corresponding to the information recording surface of the optical disk 6 are held in a conjugate relationship via
As a result, when the light beam L1 is correctly focused on the information recording surface of the optical disc 6, the first light spot diameter formed on the lower surface L by the reflected light beam L2 incident from the slope and the subsequent light reflected on the lower surface L In addition, the reflected light beam L2 reflected on the upper surface U has the same size as the second light spot diameter formed on the lower surface L.

Therefore, in the optical pickup 1, if the objective lens 4 is moved so that the beam diameters of the first and second light spots are equal, the focus of the light beam L1 can be controlled.

For this reason, the first semiconductor substrate 10 has the first and second light receiving elements 22 and 24 formed at the positions where the first and second light spots are formed, and the first and second light receiving elements are formed. The elements 22 and 24 divide the light-receiving surface into predetermined areas,
The light receiving result is output from each area.

As a result, the optical block 8 detects the difference between the light spot diameters of the first and second light receiving elements 22 and 24 by adding / subtracting the output signals of the respective areas, thereby detecting the focus error signal. It is like this.

Further, by maintaining the conjugate relationship as described above, the tracking error can be detected by detecting the formation position of the light spot with respect to the light receiving elements 22 and 24.

As a result, in this type of optical pickup, a tracking error signal can be generated by subjecting the output signals of the light receiving elements 22 and 24 separately to addition and subtraction processing.

On the other hand, the reproduction signal can be generated by adding the output signals of the respective light receiving elements 22 and 24.

Therefore, in the prism 18, a semi-transmissive film M3 is formed on the adhesive surface on the side of the light receiving element 22, so that the light receiving elements 22 and 24 can receive the reflected light beam L2.

[0022]

By the way, when the reflected light beam L2 is refracted by the inclined surface of the prism 18 and guided to the inside of the prism 18 in this way, in the light beam L1,
By specularly reflecting on the slope, the reflected light beam L2 enters the slope at the same incident angle.

Therefore, in the light beam L1, it is inevitable that part of the light beam L1 will pass through the slope and enter the inside of the prism 18, and when this light (hereinafter referred to as interfering light) enters the light receiving elements 22 and 24. The optical pickup 1 may not be able to accurately detect the tracking error signal and the focus error signal.

Therefore, in the conventional optical block 8, only the reflected light beam L2 is selectively received by utilizing the fact that the interfering light transmitted through the inclined surface and the reflected light beam L2 are incident on the bottom surface L at different incident angles. It is adapted to lead to elements 22 and 24.

That is, in the optical block 8 of this type, the critical angle at the boundary surface between the prism 18 and the adhesive 20 is selected to a predetermined value by selecting the refractive indexes of the prism 18 and the adhesive layer 20. Therefore, only the reflected light beam L2 is selectively transmitted through the boundary surface.

However, since the refractive index of the adhesive layer 20 cannot be made too small in order to set the critical angle under such conditions, the refractive index of the prism 18 must be selected to be a large value in order to make a difference from this. I don't get it. Therefore, a special material has to be selected, so that there is a drawback that the prism cannot be formed by using a general material such as plastic.

On the other hand, in the case where only the reflected light beam L2 is selectively transmitted by utilizing the refractive index of the adhesive layer 20 as described above, when the film thickness of the adhesive layer 20 becomes thin, the reflected light beam becomes adhesive. The layer 20 undergoes multiple reflections, whereby the light receiving element 22
There is also a drawback in that the reflected light beam may not be incident on 24 and 24.

Further, since the linear expansion coefficient is largely different between the adhesive layer 20 and the semiconductor substrate 10, there is a problem that the generation of strain is unavoidable when the temperature changes.

The present invention has been made in view of the above problems,
In an optical pickup in which a light receiving element and a light emitting element are integrated using a prism, an object is to provide an optical pickup that can selectively guide only a reflected light beam to a light receiving element efficiently without using an adhesive. To do.

[0030]

According to the invention of claim 1, a light receiving element and a light emitting element are formed on a substrate, and a light beam emitted from the light emitting element is reflected on the slope of the prism. In the optical pickup, the reflected light beam reflected by the optical disc is guided to the prism through the slope and then emitted to be received by the light receiving element. This is achieved by the optical pickup in which the void is formed.

Preferably, the prism is constructed so that the mounting position of the prism can be changed with respect to the light receiving element and the position can be adjusted and held.

In particular, in this case, the substrate and the prism are housed in a predetermined housing case and sealed with a transparent sealing member, and the prism is adhered to the transparent sealing member to provide a predetermined space between the prism and the light receiving element. Can be formed, and the sealing position of the transparent sealing member can be varied to hold the transparent sealing member at a predetermined position with respect to the light receiving element.

Further, an antireflection film may be formed on the light receiving surface of the light receiving element, the light receiving element may be formed on the semiconductor substrate at this time, and the antireflection film may be formed by the protective film on the semiconductor substrate. In addition, a predetermined surface other than the light receiving surface of the light receiving element can be configured to be shielded by a light shielding member.

[0034]

According to the above-mentioned structure, the boundary between the prism and the space having a small refractive index can be formed by forming the predetermined air gap between the prism and the light receiving element. The rate can be chosen to set the critical angle of this boundary.

At this time, by changing the mounting position with respect to the light receiving element and holding the light receiving element at a predetermined position, the reflected light beam can be surely incident on the light receiving element. When a transparent sealing member is used for sealing, a prism is preferably adhered to the transparent sealing member to form a predetermined gap between the prism and the light receiving element, and the sealing position of the transparent sealing member is set. By varying, it can be held at a predetermined position with respect to the light receiving element.

Further, an antireflection film is formed on the light receiving surface of the light receiving element, the light receiving element is formed on the semiconductor substrate at this time, and the antireflection film is formed by the protective film of the semiconductor substrate.
It is possible to prevent reflection of the reflected light beam on the light receiving surface, and also to prevent interference light from entering a portion other than the light receiving surface by blocking a predetermined surface other than the light receiving surface of the light receiving element with a light blocking member. .

[0037]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A preferred embodiment of the present invention will be described below in detail with reference to the accompanying drawings. The examples described below are
Since it is a preferred specific example of the present invention, various technically preferable limitations are attached, but the scope of the present invention is, unless otherwise stated to limit the present invention, in the following description.
These aspects are not limited.

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

In the figure, in the structure of the composite element 30, the parts denoted by the same reference numerals as those in the conventional example have the same structure, and thus the duplicated description will be omitted.

The optical pickup 30 is formed by accommodating an optical block 34 in a semiconductor package 32, and the optical block 34 holds the prism 18 and the first semiconductor substrate 10 separately via a predetermined gap. It has become.

That is, in the semiconductor package 32, a wall surface 38 is formed around a base 36, and the base 36 holds the first semiconductor substrate 10.

Further, the semiconductor package 32 has a wall surface 38.
The inner upper end portion of the is formed in a substantially stepped shape, and the first and second cover glasses 40 and 42 are mounted in two layers on the stepped end portion, and the upper end portion is sealed by bonding. It is supposed to stop.

Of these, the lower cover glass 40 has the prism 18 adhered to and held on the lower surface thereof, so that in the composite element 30, a space having a predetermined interval is formed instead of the adhesive layer 20 (FIG. 4). Light receiving elements 22 and 2 sandwiched between
The prism 18 is arranged on the upper part of the table 4.

Here, since the refractive index is approximately 1 in such a space, in the composite element 30, the prism 18 is formed of an appropriate optical member having a low refractive index to reflect the interference light. You can get a horn.

In other words, in the composite element 30, various optical members can be selected as the material of the prism 18, for example, plastic can be selected and the prism 18 can be formed by applying the injection molding method. Can be simplified.

Further, the first semiconductor substrate 10 and the prism 1
Since there is no adhesive layer between the layers 8, it is possible to prevent distortion from occurring.

Further, the package 36 and the cover glass 4
Since the gap interval can be controlled only by controlling the dimensional accuracy of 0, multiple reflection between the prism 18 and the semiconductor substrate 10 can be easily prevented.

Further, in this embodiment, in the semiconductor substrate 10, an oxide film 44 having a predetermined thickness is formed on the surfaces of the light receiving elements 22 and 24, and the reflected light beam L is formed by this oxide film 44.
The second antireflection film is formed.

As a result, in the composite element 30, reflection of the reflected light beam L2 on the light receiving surfaces of the light receiving elements 22 and 24 is prevented in advance, and the reflected light beam L2 can be reliably received.

Furthermore, in the semiconductor substrate 10, black oxide paint is applied to the surface of the oxide film 44 so as to avoid the light-receiving surfaces of the light-receiving elements 22 and 24, whereby the surface other than the light-receiving surfaces of the light-receiving elements 22 and 24 is coated. It is designed to block the light incident from the part.

That is, in the semiconductor substrate 10 of this type, when such unintended light enters a portion other than the light receiving surface, noise may be mixed into the original output signal.
In this embodiment, the SN ratio of the output signal is improved by blocking the light other than this purpose.

As a result, in the composite element, the detection sensitivity of the tracking error signal and the focus error signal can be further improved.

The cover glass 40 on the lower side further includes the wall 38.
In the composite element 30, the prism 18 is bonded to the cover glass 40 and then the cover glass 40 is bonded to the wall 38 in the composite element 30. The position where the prism 18 is arranged can be adjusted by adjusting the bonding position.

That is, by moving the cover glass 18 in the direction in which the light receiving elements 22 and 24 are continuous, the position of the reflected light beam L2 incident on the light receiving elements 22 and 24 can be adjusted in this direction.

On the other hand, by rotating the cover glass 18 while holding it in parallel with the semiconductor substrate 10,
The reflected light beam L2 is correctly reflected by both the light receiving elements 22 and 24.
Can be incident.

Accordingly, in the composite element 30, during assembly, the position of the cover glass 18 is adjusted while receiving the reflected light beam L2 and monitoring the output signals of the light receiving elements 22 and 24, and then fixed with the adhesive. Then, the whole is sealed with the second cover glass 42.

As a result, the mounting position of the optical pickup can be easily adjusted, and the assembling work can be simplified.

[0058]

As described above, according to the present invention, it is possible to provide an optical pickup which can selectively and efficiently guide only a reflected light beam to a light receiving element without using an adhesive.

[Brief description of drawings]

FIG. 1 is a sectional view showing an example of a composite element of an optical pickup according to the present invention.

FIG. 2 is a side view showing a conventional optical pickup.

FIG. 3 is a perspective view showing the optical block.

FIG. 4 is a side view of the optical pickup of FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Optical pickup 8,30 Composite element 10,12 Semiconductor substrate 14 Laser diode chip 16,22,24 Light receiving element 18 Prism 40,42 Cover glass

Claims (6)

[Claims] 1. A light-receiving element and a light-emitting element are formed on a substrate, a light beam emitted from the light-emitting element is reflected by an inclined surface of a prism and emitted to an optical disk, and a reflected light beam reflected by the optical disk is applied to the inclined surface. An optical pickup in which the light is guided to the inside of the prism through the light and then is emitted by the light receiving element to form a predetermined gap between the prism and the light receiving element. 2. The optical pickup according to claim 1, wherein the prism is configured such that a mounting position of the prism is variable, the position of the prism is adjusted, and the prism is held. 3. The substrate and the prism are housed in a housing case, and an upper end of the housing case is sealed with a transparent sealing member, and the prism is bonded to the transparent sealing member to receive the light. A predetermined space is formed between the element and the transparent sealing member, and the sealing position of the transparent sealing member can be changed with respect to the storage case. The optical pickup according to claim 2, wherein the optical pickup is configured to be held at a predetermined position with respect to the light receiving element. 4. The optical pickup according to claim 1, wherein the light receiving element has an antireflection film formed on the surface of the light receiving surface. 5. The substrate according to claim 4, wherein the substrate is a semiconductor substrate, the light receiving element is formed on the semiconductor substrate, and the antireflection film is formed by a protective film of the semiconductor substrate. The optical pickup described. 6. The substrate is a semiconductor substrate, the light receiving element is formed on the semiconductor substrate, and the semiconductor substrate has a predetermined surface other than the light receiving surface of the light receiving element shielded by a light shielding member. The optical pickup according to any one of claims 1 to 5, which is characterized.