JPH0472202B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a double-image prism, and particularly to a double-image prism in which a dielectric multilayer film is formed and bonded between two crystal bodies.

(Prior art) As is well known, a double-image prism is a combination of crystal prisms 1 and 2 whose optical axes are orthogonal to each other, as shown in FIG. It separates into polarized light. As an optical system using such a double-image prism, there is a polarization plane rotation detecting device based on the magneto-optical effect as shown in FIG.

This is used, for example, as a recording/reproducing optical system in a magneto-optical disk device, and is used to reflect linearly polarized light emitted from a light source (generally a semiconductor laser) 4 on the surface of a recording medium 5 having a perpendicularly magnetized film. The reflected light whose polarization plane is slightly rotated from the reference polarization plane before reflection due to the effect is split by the beam splitter 6, and the amount of the reflected light is detected by the sensor 9 and used as a servo signal. On the other hand, for transmitted light, it is 1/2
By passing through the wavelength plate 7, the plane of polarization is tilted at 45 degrees with respect to the optical axis of the crystal on the incident surface side of the double-image prism 8 provided at the next stage, so that the polarized waves emitted from the double-image prism 8 are mutually polarized. Information on the recording medium is read by detecting optical outputs whose wavefronts are perpendicular to each other by optical sensors 10 and 11, and then determining the difference between the two outputs by an output difference detector 12.

However, the above-mentioned optical system using a double-image prism has the disadvantage that it requires an expensive beam splitter, making the optical system large and expensive.

(Object of the Invention) The present invention has been made in order to eliminate the defects of the optical system using the conventional double-image prism as described above. It is an object of the present invention to provide a double-image prism that can be configured.

(Summary of the Invention) In order to achieve the above-mentioned object, a double-image prism according to the present invention is made by joining at least two crystal bodies via a dielectric multilayer film.

(Example) The present invention will be described in detail below based on an example shown in the drawings.

Figure 1a shows the configuration of a Wollaston prism, which has been commonly used as a double-image prism, and is made by joining two crystal bodies 1 and 2 so that their optical axes are perpendicular to each other. However, when the crystal body 1 is used as a prism on the incident side and the plane of polarization of the incident light 3 is inclined at 45 degrees with respect to its optical axis, the output light obtains an optical output having planes of polarization perpendicular to each other. It's uri.

Then, a suitable dielectric multilayer film 14 is provided on the joint surface of this Wallaston prism, and two crystal bodies 7 are formed.
It will be understood that if the parts 2 and 2 are joined together via the dielectric multilayer film 14, the part constitutes a half-mirror, resulting in a double-image prism 13 having the function of a beam splitter.

If an optical system as shown in FIG. 3 is constructed using the double-image prism of the present invention having the function of a beam splitter as described above, the result will be as shown in FIG. 1b.

In other words, in this case, the beam splitter 6 in FIG. 1 is removed, and the linearly polarized light emitted from the light source 4 is reflected on the surface of the recording medium 5 having a perpendicular magnetization film, and the plane of polarization is changed before reflection due to the Kerr effect. By passing the reflected light slightly rotated from the reference polarization plane of
Tilt it at 45 degrees. A dielectric multilayer film 14 is formed between the two crystals constituting the double-image prism 13, so that, for example, the transmittance and reflectance of the incident light are the same regardless of whether the light is P-polarized or S-polarized. Since a part of the light is reflected, a sensor 9 is used to detect the amount of light and used as a servo signal, while for transmitted light, optical sensors 10 and 11 detect optical outputs whose polarization planes are orthogonal to each other, and then output both outputs. The information on the recording medium 5 can be read by determining the difference between the two using the output difference detector 12, and measurement can be performed without using an expensive beam splitter.

Although the present invention has been described above using the Wallaston prism, which is the most common double-image prism, as an example, it goes without saying that the present invention is not necessarily limited to this.

(Effects of the Invention) Since the present invention is constructed and functions as described above, it is possible to construct an optical system for detecting the rotation of the plane of polarization based on the magneto-optical effect at low cost with a small number of parts, and also to use these components. This has a significant effect on facilitating adjustment.

[Brief explanation of the drawing]

FIG. 1a is a configuration diagram showing an embodiment of a double-image prism according to the present invention, FIG. 1b is a diagram showing the configuration of an optical system using this prism, and FIGS. A configuration diagram showing the configuration of the prism and A-
A sectional view and FIG. 3 are diagrams showing an example of a conventional optical system using this. 1, 2...Crystal, 14...Dielectric multilayer film.

Claims (1)

[Scope of Claims] 1. A double-image prism in which a dielectric multilayer film is formed on the joint surface of at least two crystal bodies to provide a beam splitter function. 2. The double-image prism according to claim 1, wherein three or more separated beams are obtained by forming the dielectric multilayer film. 3. A double-image prism in which a dielectric multilayer film is formed on the joint surface of at least two crystals to provide a beam splitter function, and a light exit surface of the prism that is reflected by the dielectric multilayer film or the dielectric 1. An optical system for detecting polarization plane rotation using a magneto-optical effect, comprising a light receiving element disposed on an output surface of a light beam transmitted through a multilayer film. 4. The polarization plane rotation detection optical system using the magneto-optical effect according to claim 3, characterized in that the optical system is configured such that light reflected by a recording medium having a perpendicularly magnetized film is incident on the incident surface of the double-image prism. system.