JPS6128931A - Optical path switching mechanism - Google Patents

Abstract

PURPOSE:To reduce the cause of light scattering as much as possible and to project a stable light switching signal output on each switching optical path by using a right-angled spectral type polarization beam splitter which separates and emits light in a straight traveling direction and a right-angled direction as a light incidence element and a light projection element. CONSTITUTION:An incident light beam 1 is separated by the 1st polarization beam splitter 5A into linear polarized beams 1a and 1b, which are emitted. The linear polarized beam 1b which is emitted to the 2nd optical path 8B and has a lateral polarization direction is passed through a half-wavelength plate 7 to have the polarization direction turned by 90 deg. and thus converted into a linear polarized beam 1a having a longitudinal polarization direction, which is incident on the 2nd electrooptic crystal element 3B. Therefore, light beams incident on the 1st and the 2nd electrooptic crystal elements 3A and 3B are both linear polarized beams 1A and 1a having the same polarization direction. The linear polarized beam 1a passed through the half-wavelength plate 7 is transmitted through the 2nd electrooptic crystal element 3B without having the polarization direction turned because no voltage is applied to the element 3B and incident on the 2nd polarization beam splitter 5B, so that the light is emitted in the straight traveling direction.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an optical path switching mechanism that selectively drives a pair of electro-optic crystal elements to switch optical paths.

In particular, in the present invention, each linearly polarized beam that has passed through each of the electro-optic crystal elements is firstly polarized. While making it possible to utilize substantially the entire light amount of the incident light beam by superimposing it onto the second switching optical path and emitting it,
An optical path switching mechanism is provided that also aims to suppress light scattering as much as possible.

Conventionally known optical path switching mechanisms using a mechanical switching method are relatively easy to manufacture and have the advantage of being able to output almost the entire amount of incident light onto the switching optical path, but on the other hand, the switching speed is limited due to the presence of movable parts.

There is a problem of reduced reliability due to wear and fatigue of moving parts. On the other hand, the electro-optic effect type optical path switching mechanism has no moving parts at all and utilizes the polarization direction changing effect by applying a voltage to the electro-optic crystal, so it can freely switch at high speed and uses a mechanical switching method. Unlike the above, there is no problem of lack of reliability due to wear of moving parts.

For example, an optical path switching mechanism using the electro-optic crystal element described above is illustrated in FIGS. 1A and 1B.

As shown in the figure, the incident light beam l is a circularly polarized beam, and two linearly polarized beams la whose polarization directions are orthogonal are shown.
, lb as components. A polarizing element 2 for light selection that allows only the linearly polarized beam 1a in one polarization direction to pass is arranged on the optical path of the incident light beam l, and the polarizing element 2
An electro-optic crystal element 3 is disposed on the optical path of the linearly polarized beam 1a that has passed through the element 3, and the electro-optic crystal element 3 is emitted on the optical path of the polarized beam that has passed through the element 3 in a perpendicular direction or a straight direction depending on the polarization direction of the light beam. A beam splitter 5 for polarization separation is arranged.

As a result of the above, the incident light beam l is incident on the polarizing element 2,
Only the linearly polarized beam 1a in one polarization direction is allowed to pass and enters the electro-optic crystal element 3.

The electro-optic crystal element 3 is provided with electrodes on two opposing surfaces parallel to the optical path, and is connected to a power source 4. The electrode surface is inclined at 45° with respect to the polarization direction of the light beam passing through it.

As shown in FIG. 1A, when no voltage is applied to the electro-optic crystal element 3, the light beam 1a passes through the electro-optic crystal element 3 without having its polarization direction changed, and enters the polarizing beam splitter 5. incident.

The polarizing beam splitter 5 has the function of emitting a light beam in a straight direction or a right angle direction depending on its polarization direction. Therefore, as shown in Figure A, the linearly polarized beam la selected by the polarizing element 2 and passed through the electro-optic crystal element 3 is reflected and emitted from the polarizing beam splitter 5 in a perpendicular direction depending on its polarization direction.

On the other hand, No. □. Figure 8, Ioyo, pneumatic crystal element
(When a predetermined half-wave voltage is applied to the polarizing beam splitter 3, the linearly polarized beam 1a incident on it is converted into a linearly polarized beam 1b with its polarization direction rotated by 90 degrees when passing through the polarizing beam splitter. 5.

Therefore, this linearly polarized beam 1b is
5 and is emitted straight ahead without being reflected.

As can be understood from the above comparison example, the combination of the polarizing beam splitter 5 and the electro-optic crystal element 3 can provide an optical path switching mechanism that can accurately switch the optical path of an incident light beam in two directions. A linearly polarized beam 1 whose light beam components always have a vertical or horizontal polarization direction.
Unless either a or lb is present, the desired optical path switching cannot be achieved, and the other linearly polarized beam must be cut from the incident light and used.

That is, the above-mentioned optical path changeover switch has the problem that only half of the total amount of incident light can be utilized at any given time, resulting in a 50% light loss.

As in the comparative example above, the present invention is an electro-optic effect type optical path switching mechanism using a beam splitter for polarization separation and a crystal element having an electro-optic effect as optical path switching elements. It was developed to accurately solve the problem of optical loss with an extremely simple optical circuit configuration. At the same time, it eliminates the causes of light scattering as much as possible and outputs stable optical switching signals to each switching optical path. is emitted.

As shown in FIG. 2, the first pair of orthogonal spectrometers are placed on the diagonal of the virtual rectangle. Second polarizing beam splitter-5A, 5
Arrange B. The first polarizing beam splitter 5A converts the incident light beam l into a straight direction (on the first optical path 8A) and a perpendicular direction (on the first optical path 8A) according to the polarization direction of the linearly polarized beams la and lb, which are its components.
It has a function of separating and emitting light onto the second optical path 8B). That is, the first polarizing beam splitter 5A emits linearly polarized beams la and lb having different polarization directions onto optical paths along two adjacent sides forming right angles of the virtual rectangle.

The second polarized beam splitter 5B has a function of superimposing the linearly polarized beams la and lb which are respectively incident at right angles, and outputting the superimposed linearly polarized beams onto the first switching optical path 9A or the second switching optical path 9B. That is, the second polarizing beam splitter 5B outputs the linearly polarized beam incident from the optical path along the other two right-angled adjacent sides of the virtual rectangle onto each switching optical path on the extension of the two sides.

Further, a first light reflecting element (for example, a prism) 6A and a second light reflecting element (for example, a prism) 6B are arranged on the other diagonal of the virtual rectangle. The first light reflecting element 6A has a function of turning one of the light beams emitted from the first polarizing beam splitter 5A onto the first optical path 8A toward the second polarizing beam splitter 5B in a direction perpendicular to this direction. Turning light path 8
A'), the second light reflecting element 6B converts the other light beam that can be emitted from the first polarizing beam splitter 5A onto the second optical path 8B to the second polarizing beam splitter 5B in a direction perpendicular to the first polarizing beam splitter 5A. (This orthogonal turning optical path is referred to as 8B').

For purposes of explanation, optical paths 8A and 8A' are referred to as the first optical path, and optical paths 8B and 8B'.
is called the second optical path. First polarizing beam splitter-5A
A first optical path 8 leading from to a second polarizing beam splitter 5B
A, 8A' and the second optical paths 8B, 8B' exhibit rectangular trajectories as shown in the figure, as understood from the above description.

Further, a first electro-optic crystal element 3A is disposed on the optical path 8A between the first polarizing beam splitter 5A and the first light reflecting element 6A, and a first electro-optic crystal element 3A is disposed on the optical path 8A between the first polarizing beam splitter 5A and the first light reflecting element 6A, and a A second electro-optic crystal element 3B is placed on an optical path 8B' parallel to the optical path 8A.

1st. As explained based on FIG. 1, the second electro-optic crystal elements 3A and 3B are provided with electrodes on two opposing surfaces parallel to the optical path, and the electrodes are connected to a power source (not shown) at an angle of 45 degrees. When no voltage is applied, the incident linearly polarized beam travels straight without changing its polarization direction, and when a voltage is applied, the polarization direction of the linearly polarized beam passing through it is changed to 90°. It has the function of rotating and emitting light.
! Crystal elements having the above-mentioned electro-optic effect include single-crystal niozoate and polycrystalline transparent ceramic (PLZT). In particular, transparent ceramics having a secondary electro-optic effect have a large electro-optic effect and can be used at low voltage. Since it can be driven, it is suitable as an element for optical path switching.

Further, a half wavelength plate 7 is arranged on the optical path 8B between the first polarizing beam splitter 5A and the second light reflecting element 6B.

This half-wave plate 7 has a function of constantly converting the polarization direction of the incident linearly polarized beam and outputting it, and by disposing it on the second optical path, the first polarizing beam splitter 5A
The polarization direction of the linearly polarized beam 1b emitted from is converted and provided to the second electro-optic crystal element 3B.

Therefore, if the second electro-optic crystal element 3B is placed on the output light side of the half-wave plate 7, both may be placed on the second optical path 8B or 8B'.

Further, the above-mentioned half wavelength plate 7 is a first polarizing beam splitter.
It is sufficient to convert the polarization direction of either the linearly polarized beam la or 1b emitted from 5A and arrange it so that it is applied to one electro-optic crystal element.
It is also possible to arrange the polarization direction of the linearly polarized beam 1a emitted from the polarized beam splitter 7A to be changed. In this case, the first electro-optic crystal 3A is placed on the output light side of the half-wave plate 7, as described above.

As mentioned above, the half-wave plate 7 is used to select one of the linearly polarized beams emitted from the first polarizing beam splitter 5A, e.g.
Convert the polarization direction of b to the first polarization beam splitter-5.
It has the same polarization direction as the other linearly polarized beam la emitted from A and is applied to one electro-optic crystal element 3B.

1st. One or the other of the second electro-optic crystal elements 3A and 3B is selectively driven to convert the polarization direction. Therefore, the first
．． Second electro-optic crystal element 3A.

When one of the linearly polarized beams supplied from 3B to the second polarizing beam splitter 5B is a linearly polarized beam having a vertical polarization direction, the other is a linearly polarized beam having a horizontal polarization direction; When one is a linearly polarized beam with a longitudinal polarization direction, the other is a linearly polarized beam with a horizontal polarization direction.

Thus, the first. Second electro-optic crystal element 3A.

By selectively activating (applying a voltage to) either one of 3B, the first switching optical path of the polarizing beam splitter 5B converts substantially the entire amount of the incident light beam 1 into the output light beam 1' depending on which one is activated. 9A or the second switching optical path 9B. This will be explained as follows by distinguishing between the case where a voltage is applied to the first electro-optic crystal element 3A (FIG. 3) and the case where a voltage is applied to the second electro-optic crystal element 3B. First, explanation will be given with reference to FIG.

The incident light beam 1 is separated from the first polarizing beam splitter 5A into linearly polarized beams 1a and 1b, which are emitted. The linearly polarized beam ib having a horizontal polarization direction that is emitted onto the second optical path 8B passes through the half-wave plate 7, so that the polarization direction is rotated by 90 degrees, and the linearly polarized beam ib has a vertical polarization direction. The beam is converted into a beam la and is incident on the second electro-optic crystal element 3B. Therefore, the first. The light beams incident on the second electro-optic crystal elements 3A and 3B have the same polarization direction, so they are linearly polarized beams la and la, and the half-wave plate 7
Since no voltage is applied to the second electro-optic crystal element 3B, the linearly polarized beam la that has passed through the second electro-optic crystal element 3B passes through the second polarizing beam splitter without having its polarization direction changed.
5B, and is emitted in the straight direction (on the first switching optical path 9A).

On the other hand, since a voltage is applied to the first electro-optic crystal element 3A, the linearly polarized beam 1a emitted from the first polarizing beam splitter 5A onto the optical path 8A has its polarization direction rotated by 90 degrees and is converted into a linearly polarized beam 1b. The polarized beam is then emitted and incident on the second polarizing beam splitter 5B, where it is directed in the perpendicular direction (
(onto the first switching optical path 9A). As a result, the linearly polarized beams la and lb separated by the first polarizing beam splitter 5A are superimposed and emitted onto the first switching optical path 9A. That is, substantially the entire amount of the incident light beam 1 is output onto the first switching optical path 9A as the output light beam 1', and optical path switching without optical loss is possible.

Also, number 1. Since only one of the second electro-optic crystal elements 3A and 3B needs to be turned on, the cause of light scattering is reduced by half compared to when both are turned on.

Next, the case where a voltage is applied to the second electro-optic crystal element 3B will be explained based on FIG. 4.

Same as above, 1st. The light beams incident on the second electro-optic crystal elements 3A and 3B are linearly polarized beams la and la having the same polarization direction.

Since a voltage is applied to the second electro-optic crystal element 3B, the linearly polarized beam la having the vertical polarization direction that has passed through the half-wave plate 7 is rotated by 90 degrees, and the polarization direction is changed to the horizontal polarization direction. The linearly polarized beam 1b is converted into a linearly polarized beam 1b having a polarized beam 1b, and is emitted, which is incident on the second polarized beam splitter 5B, and is emitted in the perpendicular direction (on the second switching optical path 9B). On the other hand, the linearly polarized beam la emitted from the first polarized beam splitter 5A onto the optical path 8A is directed to the first electro-optic crystal element 3A.
Since no voltage is applied to the beam, the beam passes through this without changing its polarization direction, enters the second polarizing beam splitter 5B, and is emitted in the straight direction (on the second switching optical path 9B).

As a result, the linearly polarized beams la and lb separated by the first polarizing beam splitter 5A are ultimately superimposed and emitted onto the second switching optical path 9B. That is, substantially the entire amount of the incident light beam 1 is emitted onto the first switching optical path 9B as the outgoing light beam 1'. That is, optical path switching without optical loss is possible. Also, number 1. Since only one of the second electro-optic crystal elements 3A and 3B needs to be turned on, the cause of light scattering is reduced by half compared to when both are turned on.

For example, in FIG. 2, the 1/2 wavelength plate 7 is not used and the first. Even if the second electro-optic crystal elements 3A and 3B are turned on or off at the same time, it is possible to utilize almost the entire amount of light of the incident light beam, but when both are turned on, the cause of noise (light scattering) increases twice. . Also, both crystal elements 3A and 3B are OFF.
In this case, the cause of the noise is eliminated, but the balance between the optical outputs when both are ON and when both are OFF will be significantly disturbed.

In the present invention, the half wavelength plate 7 is arranged as described above.
By using together, the first. Since it is only necessary to selectively turn on either one of the 211tth optical crystal elements 3A and 3B, the noise can be reduced by half, and moreover, the noise can be reduced by half. The light output onto the second switching optical paths 9A, 9B is completely balanced.

The present invention can provide an optical path switching mechanism that can utilize substantially the entire amount of incident light as an output light amount (light switching signal) while achieving the above effects.

In the embodiments described above, a polarizing beam splitter of the orthogonal splitting type that separates and emits the light in straight and perpendicular directions according to the polarization direction was used as the light input element and the light output element in the switching mechanism. As long as the input element and the light output element have a polarization separation function of separating and emitting light components into two directions depending on the polarization direction of the light components, it is not limited to the above-mentioned orthogonal spectral type.

[Brief explanation of drawings]

FIGS. 1A and 1B are perspective views illustrating the switching operation of an electro-optic effect type optical path switching mechanism in comparison with the present invention, showing the element arrangement, and FIG. 2 is a perspective view of an optical path switching mechanism according to the present invention. FIG. 3 is a perspective view of the same optical path switching mechanism illustrating the operation of switching the optical path in one direction, and FIG. 4 is a plan view showing the embodiment with the element arrangement. FIG. 4 is a perspective view of the same optical path switching mechanism explaining the operation of switching the optical path in the other direction Perspective view,
It is. l...Incoming light beam, 1a, lb...Linearly polarized beam, 3A...First electro-optic crystal element, 3B...Second
Electro-optic crystal element, 5A...first polarizing beam splitter, 5B...second polarizing beam splitter-56A.
...First light reflection element, 6B...Second light reflection element, 7.
...Half wavelength plate, 8A, 8A'...First optical path, 8
B, 8B'...second optical path, 9A...first switching optical path, 9B...second switching optical path. Procedural amendment 9/1982 Patent Application No. 150090 2 Title of invention Optical path switching mechanism 3 Relationship with the case of the person making the amendment Patent applicant 4, agent 144 6. Number of inventions increased by amendment 7. Subject of amendment Each column of claims of the specification and detailed explanation of the invention (1) The scope of claims of the specification is amended as shown in the appendix "Notes". (2) The explanations from "Therefore..." on page 9, line 13 of the same issue to "we provide..." on page 10, line 10 of the same issue were deleted, and the explanation was replaced with [as mentioned above, The half-wave plate 7 is placed on the first optical path 8A, 8A' or the second optical path 8B, 8B', and always changes the polarization direction of either one of the linearly polarized beams passing on the same optical path. The same effect can be obtained by arranging it before or after the electro-optic crystal element if it is on the same optical path. ” Hatake 171
D＞', Cedar. ``Note'' (Claims) ``A first polarizing beam splitter that separates an incident light beam into a first optical path and a second optical path according to the polarization direction of the optical component and outputs the same.
a half-wave plate disposed in either the first optical path or the second optical path to make one of the linearly polarized beams have the same polarization direction as the other linearly polarized beam; an electro-optic crystal element that is provided in each of the elements and changes the polarization direction of the linearly polarized beam passing therethrough by selectively applying a voltage;
A second polarizing beam splitter that selectively superimposes both linearly polarized beams obtained from the first optical path and the second optical path onto the first switching optical path and the second switching optical path according to the polarization directions of the optical components, respectively, and outputs the resulting beams. A light path characterized by consisting of! exchange device. ”

Claims (1)

[Claims] A linearly polarized beam passes through a first polarizing beam splitter that separates the incident light beam into a first optical path and a second optical path according to the polarization direction of the light component and outputs the beam, and outputs the linearly polarized beam from the first polarizing beam splitter onto the first optical path. Either of the linearly polarized beams emitted onto the second optical path is passed through a half-wave plate so that the polarization direction is the same as that of the other linearly polarized beam emitted from the first polarization beam splitter, and the polarization direction is Both of the same linearly polarized beams are passed through separate electro-optic crystal elements, and by selectively applying a voltage to one of the electro-optic crystal elements, one of the linearly polarized beams passes through both electro-optic crystal elements. The configuration is such that the polarization direction of the beam is changed, and a linearly polarized beam with both polarization directions changed and a linearly polarized beam with the polarization direction not changed are placed on a first switching optical path and a second switching optical path, respectively, depending on the polarization direction of the light component. The linearly polarized beams are selected to pass through a second polarizing beam splitter that is selectively emitted, thereby changing the polarization direction, so that the linearly polarized beams are superimposed on either the first switching optical path or the second switching optical path. An optical path switching device characterized by being configured to emit light.