JPH03116005A - Non-polarization beam splitter - Google Patents

Abstract

PURPOSE:To hold the ratio of transmission light and reflected light by constituting a polarizing film to be applied of a non-polarizing film for bringing a P polarization component and an S polarization component to transmission and reflection in an equivalent ratio, so that an incident angle in the plane of polarization becomes about 45 deg. against an incident light limited to prescribed wavelength width. CONSTITUTION:A polarizing film is constituted of a non-polarizing film for bringing a P polarization component and an S polarization component to transmission and reflection in an equivalent ratio, respectively, and also, a combination arrangement of a first - a fourth surfaces 110 - 113 and a plane of polarization 114 is set so that an incident angle in the plane of polarization 114 comes to about 45 degrees against an incident light limited to prescribed wavelength width. In such a case, a transmission light 116 and a radiated light 120 are radiated from the same point 119 on the surface 111. In such a way, even if an adhered article, etc., exist on the surface 111, or the quantity of the adhered article, etc., is varied with the lapse of time, a ratio of the transmission light 116 and the reflected light 120 can always be hold so as to be constant.

Description

[Detailed Description of the Invention] [Industrial Application Fields] The present invention separates incident light of a certain wavelength into transmitted light and reflected light by an internally incorporated film, and radiates the light to the outside from the same part on the same surface. It is configured like this! ! Related to polarizing beam splitters.

[Prior Art] A conventional polarized beam splinter (hereinafter referred to as PBS) is disclosed in Japanese Patent Publication No. 63-40288, and its configuration has a cross-sectional shape as shown in FIG. . That is, the first surface 10 and the second surface 11, the third surface 12 and the fourth surface J3 are arranged in parallel, respectively, and are combined so that they have a parallelogram cross-sectional shape. .

In general, the depth of this PBS is configured to have a length comparable to the height of the parallelogram, and the distance between the intersection line of plane 10 and plane 13 and the intersection line of plane 11 and plane 12 is Polarization planes 14 are arranged diagonally. Glass or the like is used as the material for each of these surfaces, and since the surface 12 is used as a reflective surface, a reflective film is deposited on the surface.

Further, a polarizing film is deposited on the polarizing surface 14.

Here, when incident light 15 having circular polarization characteristics enters surface 10 in parallel to light 13, it is refracted by a predetermined refractive index and then separated into a P polarization component and an S polarization component at point 21 on polarization surface 14. The P-polarized light component shown by the solid line in FIG.

Note that at this time, the optical path of the transmitted light 16 is parallel to the optical path of the incident light 15.

On the other hand, the S-polarized light component shown by the dotted line in Figure 1 is at point 2 on the polarization plane 14.
1, passes through an optical path 17, is reflected at a reflective surface 12, passes through an optical path 18, passes through a point 22 on a polarizing plane 14, and is emitted from a point 19 on a surface 11, becoming reflected light 20.

Note that the optical path of one reflected light 20 is perpendicular to the optical path of the incident light 15. The environment surrounding the PBS is limited to substances with a refractive index of 1 or very close to 1, such as air or vacuum.

[Problems to be Solved by the Invention] However, with the above-mentioned conventional configuration, there are cases where the polarization characteristics of the incident light cannot be defined, or where the polarization characteristics are unstable due to, for example, elliptically polarized light whose polarization direction is rotated. In this case, there was a problem in that the ratio between the P-polarized light component and the S-polarized light component, that is, the ratio between the transmitted light and the reflected light, could not be kept constant.

The present invention has been made to eliminate the above-mentioned drawbacks, and even when the polarization characteristics of incident light cannot be specified, transmitted light and reflected light can be combined without being affected by the polarization characteristics of incident light. An object of the present invention is to provide a non-polarizing beam splitter that can maintain a constant ratio.

[Means for Solving the Problems] The non-polarizing beam splitter of the present invention has a polarizing film coated on a polarizing surface that transmits and reflects P-polarized light components and S-polarized light components in equal amounts. A polarizing film is used, and the planes constituting the parallelogram and the plane of polarization are arranged in combination so that the angle of incidence on the plane of polarization is approximately 45° for incident light limited to a predetermined wavelength width. I have to.

[Function] In the present invention, when the incident light is incident on the non-polarizing film at an angle of incidence of approximately 45°, the zero reflected light is transmitted and reflected in equal proportions of the P-polarized light component and the S-polarized light component, respectively. The light is totally reflected by the reflective surface and passes through the non-polarizing film again, but at this time all of the reflected light passes through this non-polarizing film. Therefore, at the radiation point, the transmitted light and the reflected light are radiated in directions perpendicular to each other, and the ratio of the transmitted light to the reflected light is a constant ratio that does not depend on the polarization characteristics of the incident light.

[Example] Hereinafter, an example of the present invention will be described in detail based on the drawings.

FIG. 1 shows the cross-sectional shape of a non-polarizing beam splitter showing an embodiment of the present invention. The cross-sectional shape is almost the same as the conventional structure shown in Fig. 2, so corresponding parts are given the same numbers with 100 added.
Description of its detailed configuration will be omitted.

The difference from the conventional configuration shown in FIG. 2 is that the polarization plane 11
4, a non-polarizing film is deposited.

Because of this non-polarizing film, for example, the incident light 11 has polarization characteristics of elliptical polarization and whose polarization direction rotates with time.
5 is incident on the surface 110 parallel to the surface 113, and after a predetermined refraction, it is incident on the polarization surface 114. At one point 121, this incident light 115 becomes transmitted light with equal amounts of P-polarized light component and S-polarized light component, respectively. It is separated into reflected light. The transmitted light is then radiated from a point 119 on the surface 111 and becomes transmitted light 116. Therefore, this transmitted light 116 includes a P polarized light component and an S polarized light component. Further, the optical path of the transmitted light 116 is parallel to the optical path of the incident light 115.

On the other hand, the reflected light reflected at the point 121 on the polarization plane 114 is
It passes through the optical path 117 and is totally reflected by the reflective surface 112, and the optical path 11
8, passes through a point 122 on the polarization plane 114, is emitted from a point 119 on the plane 111, and becomes reflected light 120. Note that this reflected light 120 also includes a P-polarized light component and an S-polarized light component. Furthermore, the optical path of the reflected light 120 is perpendicular to the optical path of the incident light 115.

Figure 3 is a diagram showing the wavelength versus transmittance characteristics of the polarization plane of the non-polarizing beam splitter according to the present invention using the incident angle as a parameter, where the vertical axis shows the transmittance and the horizontal axis shows the wavelength (λ). . A transmittance of 100% means total transmission, and a transmittance of 0% means total reflection. Further, the transmittance of 50% means a transmission characteristic in which transmitted light and reflected light are equal. Therefore, the wavelength λ shown in FIG. 1 indicates the wavelength of incident light at which the transmittance is 50%. Furthermore, the solid line shows the transmission characteristic of the P-polarized light component, and the one-dot line shows the transmission characteristic of the S-polarized light component.

Here, in the state shown by ■ in the figure where the incident angle to the polarizing film 114 is approximately 45 degrees, the transmitted light and reflected light of the P-polarized light component and the S-polarized light component, respectively, in the vicinity (±Δ) of the wavelength λ. The optical properties of the non-polarizing film are selected so that the light is evenly separated.

- When the incident angle to the forceless polarizing film is sufficiently small, that is, when the incident light is almost vertical, as shown by ■ in Figure 5, the wavelength λ of the incident light does not exceed a predetermined value. The transmittance of both the S-polarized component and the S-polarized component is 100%, but when the wavelength λ of the incident light increases beyond a predetermined value, P
Both the polarized light component and the S-polarized light component make a sharp transition from transmittance 100% to transmittance 0%.As shown in the figure, the wavelength λ at which this transition occurs is located on the much longer wavelength side than There is. Therefore, in the range of wavelength λ and ±Δ, both the P-polarized light component and the S-polarized light component have a transmittance of 100%.

As mentioned above, in the non-polarizing beam splitter shown in FIG.
At the point 121 where P 15 is incident on the polarization plane 114, P
The incident angle and the wavelength λ of the incident light are set so that the transmitted light and reflected light of the polarized light component and the S-polarized light component are separated equally by −1.
, and set it to 1.

1 = One side At point 122 on the polarization plane 114, the reflected light totally reflected by the 1 reflection surface 112 has a small incident angle with respect to the polarization plane 114, so as is clear from FIG. 3, the wavelength λ and the odor are P Both the polarized light component and the S-polarized light component are transmitted 100%.

Note that the specifications in the above-mentioned embodiment are as follows. That is, the refractive index of the glass that forms the base of the non-polarizing beam splitter is 1.684. The angles between the plane 113 and the plane of polarization 114 and between the plane 112 and the plane of polarization 114 are 24°48, respectively.
', 110 and polarization plane 114, and 111 and polarization plane 1
The angles formed with 14 are 22° 12', respectively.

Note that the above-mentioned specifications are not limited to these, and the angle formed by each plane and the polarization plane is selected so that the angle of incidence at the point where the incident light enters the polarization plane is approximately 45°. I can do it.

[Effects of the Invention] As explained below, according to the present invention, 5 transmitted lights 116
Since both the reflected light 120 and the reflected light 120 are emitted from the same point 119 on the surface 111, even if there are deposits on the surface 111 or the grooves of the deposits change over time, they will not pass through. The ratio between the light 116 and the reflected light 20 can always be kept constant. The same applies even if physical property changes such as deposits or the like change the optical attenuation characteristics over time. Furthermore, even if there is a deposit on the entrance surface 110,
Since these deposits act on the transmitted light 116 and the reflected light 120 in common, the transmitted light 116 and the reflected light 120 are not affected by optical changes in the surface condition of the splitter.
The ratio is maintained constant. Furthermore, the polarization characteristic of the incident light 115 is not only linearly polarized light or circularly polarized light in which the polarization direction is stably maintained, but also elliptically polarized light whose polarization direction rotates over time, that is, polarized light. Even if the state of direction cannot be determined over time,
At point 121 on polarization plane 114, P polarization component and S
Since the transmitted light and reflected light of each polarized light component are equally separated, it is possible to maintain the ratio of transmitted light 116 and reflected light 120 constant at all times.

[Brief explanation of drawings]

FIG. 1 is a diagram showing a cross-sectional structure of a non-polarizing beam splitter according to an embodiment of the present invention, FIG. 2 is a diagram showing a cross-sectional structure of a conventional polarizing beam splitter, and FIG. 3 is a diagram showing a cross-sectional structure of a non-polarizing beam splitter according to an embodiment of the present invention. 110 is a diagram showing the wavelength versus transmittance characteristics in the polarization plane of the splitter. First surface, 111
...Second surface, 112...Third surface,
113... Fourth surface, 114... Polarization plane, 115... Incident light, 116... Transmitted light, 120... Reflection light.

Claims (1)

[Claims] The first (110) and second (111) planes and the third (112) and fourth (113) planes arranged in parallel have a cross-sectional shape of a parallelogram. Combination, 2nd (111)
and the intersection line of the third (112) plane, the first (110) and the fourth plane
A polarizing plane (114) is arranged between the intersection line of the (113) plane, and a total reflection film is placed on the third (112) plane.
114) is coated with a polarizing film, incident light having polarization characteristics parallel to the fourth (113) surface is incident on the first (110) surface, and a specific portion (119) of the second (111) surface is applied. ), the transmitted light (116) and reflected light (120) are perpendicular to each other.
In the non-polarized beam splatter that separates and radiates the polarized light, the polarizing film is configured to transmit and reflect the P-polarized light component and the S-polarized light component in equal proportions, and has a predetermined wavelength width. The first to fourth beams are arranged so that the angle of incidence on the plane of polarization is approximately 45 degrees for the limited incident light.
A non-polarizing beam splitter characterized in that a combination arrangement of the plane of the plane and the plane of polarization is set.