JPS59195347A - Optical head - Google Patents

Abstract

PURPOSE:To enable both beam form converting function and optical path converting function of a prism to satisfy the prescribed value respectively, by providing a positioning part to a housing to control an angle formed by the optical axis of a collimator lens and a total reflecting surface of the prism which provided with said surface. CONSTITUTION:A positioning stage part 7 sets the position of the optical path of a lens barrel 2a containing a semiconductor laser 1 and a collimator lens 2. A positioning stage part 8 sets the position of the total reflecting surface of a prism 6. These parts 7 and 8 function to set an angle formed by the positioning surfaces such as LL, SS, etc. equal to a vertical angle theta4 of the prism 6. Therefore the angle formed by the incident optical axis to the prism 6 and the total reflecting surface of the prism 6 is controlled to the angle theta4 by pressing and fixing the total reflecting surface of the prism 6 to the part 8 and at the same time the laser 1 and the barrel 2a to the part 7 respectively. Thus an incident angle theta1 to the incident surface of the prism 6 is set correctly based on angles theta3 and theta4 of the prism 6. Then a beam form converting function of the prism 6 satisfies a prescribed conversion factor, and furthermore the orthogonal performance is also satisfied between an incident optical axis and an output optical axis.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention is used, for example, in an optical recording and reproducing device that focuses light from a semiconductor laser onto a disc-shaped recording medium (hereinafter referred to as an optical disk) to record and reproduce information. Items related to optical heads.

This is the conventional configuration and its problem beam, and wave optics teaches that even if such an elliptical beam is condensed, the aperture performance is not good.

Therefore, in order to improve the recording and reproducing characteristics of an optical recording and reproducing device, it is essential to convert an elliptical beam into a parallel circular beam.

Conventionally, such a conversion of the light beam shape was disclosed in Japanese Patent Application Laid-open No. 55-10.
As seen in Japanese Patent No. 8612, a concave-convex cylindrical lens was used. FIG. 1 is a sectional view of an optical system using the concave-convex cylindrical lens. Referring to FIG. 1, 1 is a semiconductor laser, 2i[dC-lens, 3
is a concave cylindrical lens, 4 is a convex cylindrical lens, and 5 is a housing of the entire optical head.

An optical system using such a concave-convex cylindrical lens has the disadvantage that the dimension in the optical axis direction becomes large.

Therefore, we proposed an optical head that uses a prism to convert the shape of a light beam. FIG. 2 is a configuration diagram of an optical head using the prism. 6t/i in FIG. 2 is a prism having the function of converting an elliptical beam into a circular beam and orthogonally converting the optical path of the incident chief ray CR1 to the optical path of the outgoing chief ray CR3. P.

Q, R, and Z each indicate the apex of the prism 6. Further, the surface represented by the ridgeline QR functions as a total reflection surface.

Here, the beam shape conversion rate of the prism 6 can be expressed as the ratio of the beam diameter 11 at the cross section AA to the beam sweep 2 at the cross section BB.

This ratio can be derived from the refraction at the plane of incidence represented by the ridgeline PQ. That is, the angle of incidence is θ
1. If the refraction angle θ2 is I2/11=Cosθ2/CO8θ1 However, if the refractive index of the prism material is n, the refraction angle θ2 is unique from Snell's law as K, θ2=Sin
'(,Sinθ1)f[determine].

Therefore, the beam shape conversion rate of the prism 6 is the incident principal light @
It can be seen that n is determined by the angle θ1 between CR1 and the normal to the plane of incidence represented by the ridgeline PQ, that is, the angle between CR1 and PQ.

Furthermore, the optical path conversion function of the prism 6 is indicated by the angle (deflection) formed by the incident principal ray CR1 and the outgoing principal ray CR3. It is determined by OR2, the angle formed by the total reflection surface represented by the side QR, the light ray reflected by the total reflection surface, and the angle formed by the surface represented by the side RZ.

From what has been described above, the beam shape conversion function and the optical path conversion function of the prism 6 are based on the angle θ1. Angle θ5. It can be seen that it is determined by the angle θ4.

That is, in the optical system using the light beam shape and the optical path changing prism 6 shown in FIG. 2, the angle θ5. The angular accuracy of the angle θ6 and the angular accuracy of the angle θ1 during assembly are important.

On the other hand, in a separately considered prism, the incident optical axis CR1
If the angle formed by the total reflection surface is set to be equal to θ4, the angle θ1 can obtain orthogonality between the incident optical axis CR1 and the output optical axis GR32 and the desired beam diameter ratio T.
The angle θ3. θ4 is formed.

Therefore, the first important point in an optical head using this prism is that the incident optical axis CR1 and the total reflection surface form an angle equal to θ4.

However, in the conventional example, the means for doing so was not clearly specified.

OBJECTS OF THE INVENTION The present invention takes the above points into consideration and aims to ensure the accuracy of the light beam shape conversion and optical path conversion functions of the prism.

Structure of the Invention The present invention has a semiconductor laser and a collimator lens, and is configured to convert incident light, which is converted into a parallel elliptical beam by the collimator lens, into a parallel circular beam orthogonal to the incident light. A prism having a surface is provided, and a positioning portion for regulating the angle formed between the optical axis of the collimator lens and the total reflection surface of the prism is provided in a housing housing the collimator lens and the prism, and the light beam of the prism is An optical head with reliable shape conversion and optical path conversion functions.

DESCRIPTION OF EMBODIMENTS Next, an embodiment of the present invention will be described with reference to FIGS. 3 and 4. FIG. 3 is a plan view of an optical head in one embodiment of the present invention, and FIG. 4 is a front view thereof.

Reference numeral 7 denotes a stepped portion for positioning the optical axis of the lens barrel 2a that accommodates the semiconductor laser 1 and the collimator lens 2. 8 is a step portion for positioning all the anti-contact surfaces of the prism 6.-0 The positioning step portions 7 and 8 are each LL.

It is formed so that the angle formed by the positioning surface represented by SS is equal to the apex angle θ4 of the prism 6.

Therefore, if the total reflection surface of the prism 6 is pressed against the step 8 and fixed, and the semiconductor laser 1 and the mirror m2a' are pressed against the step 7 and fixed, the total reflection of the prism 6 will be The angle formed by the surfaces is defined as angle θ4.

Therefore, the angle θ3 of the prism 6. From θ4, prism 6
The angle of incidence θ1 on the incident surface of the prism 6 is set correctly, and
The beam shape conversion function satisfies a predetermined conversion rate and also satisfies the orthogonality of the incident optical axis and the output optical axis.

Here, the reason why the total reflection surface, that is, the surface represented by the edge QR is used as the positioning surface is that if the entrance surface β, which can be represented by the edge PQ, or the exit surface, which can be represented by the edge RZ, is used as the positioning surface, the aperture limit This led to the increase in the size of prism 6.

In fact, there are restrictions on the shape and arrangement of optical systems, etc. that can be placed following the failure of the collimator lens 2 or the prism 6. Further, since the representative surface of the edge PZ is a surface that has no influence on the accuracy of the prism 6, this surface cannot be used as a positioning surface.

Next, another embodiment of the present invention will be described using FIGS. 5 and 6. FIG. 5 is a plan view of another embodiment of the present invention, and FIG.
The figure is a front partial cross-sectional view.

Reference numeral 8 in the figure is a stepped portion provided in the housing of the optical system, and in the case of this embodiment, the prism 6 is attached as a stepped portion lower than the surface. 9 is a positioning hole formed so that its central axis forms an angle θ4 with the fully refracted surface of the prism 6, and the lens barrel 2a housing the collimator lens 2 and the semiconductor laser 1 are coaxially engaged. do.

In this embodiment, after positioning by pressing the entire non-conforming surface of the prism 6 against the positioning plate, the positioning plate is removed.

With such a configuration, all anti-fouling surfaces come into direct contact with air, so good anti-fouling properties can be obtained without the need to form a special anti-fouling film. The optical head of the present invention has a semiconductor laser and a collimator lens, and the collimator lens converts one beam into a parallel elliptical beam into a parallel beam perpendicular to the incident light. By providing a positioning part in the housing that regulates the angle formed by the total repulsion surface (having a prism and the optical axis of the collimator lens and the above-mentioned), the aperture of the entrance surface and exit surface of the prism can be adjusted. The beam shape conversion function and the optical path conversion function of the prism can satisfy predetermined values without any restrictions on the shape or arrangement of the optical system on the incident side or output side of the prism, and It has great industrial value.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional side view of an optical head in a conventional example, and FIG.
3 is a sectional plan view of an optical head in an embodiment of the invention, FIG. 4 is a front view of the same, and FIG. , a cross-sectional view of an optical head in another embodiment of the present invention, FIG.
It is the same sectional front view. 1...Semiconductor L'-"!-12...Collimator lens, 6-...Prism, A, 8...Ko position fA? deciding step part, 9...... position L!71'/)
Name Figure 3 S \\et l '7 Figure 4 Figure 5? Figure 6 Otsu 8 Wrinkles

Claims (1)

[Claims] A prism includes a semiconductor laser and a collimator lens, and has a total reflection surface configured to convert incident light that has been converted into a parallel elliptical beam by the collimator lens into a parallel internal beam that is perpendicular to the incident light. An optical head further comprising: a positioning portion for regulating the angle formed between the optical axis of the collimator lens and the total reciprocal surface of the prism in a housing housing the collimator lens and the prism.