JPS602920A - Optical path switch - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

Detailed Description of the Invention The present invention employs a pair of beam splitters for polarization separation and a crystal element having an electro-optic effect, for example, a crystal element having a secondary electro-optic effect, as an optical path switching element to reduce the total amount of incident light. (both linearly polarized beams la and lb)
The present invention relates to an optical path changeover switch that can emit light onto a first switching optical path and a second switching optical path.

FIG. 1 shows a beam gooseberry and vine 5' for polarization separation as an optical path switching element shown for comparison with the present invention.
It also shows the principle of Sochi, an optical path switching switch using a crystal element 3' having an electro-optic effect.

As is known, the light beam l is made up of two linearly polarized beams la and lb f components whose polarization directions are orthogonal to each other. The polarized beam currant 5' has the function of separating the incident light beam into two different directions depending on the polarization direction and outputting the separated light beam. For example, one of the linearly polarized beams Ia, which is a component of the incident light beam 1, is emitted from an exit pupil in a direction perpendicular to the direction of incidence, and the other linearly polarized beam lb is emitted in the same direction.

Therefore, by setting the light beam incident on the polarized beam currant 5' to either the linearly polarized beam la or ib, the output direction can be changed, that is, a switch operation can be obtained.

In order to selectively convert the polarization direction of the light beam incident on the polarizing beam splitter 5' into the linearly polarized beam 1a or II'i1b, the crystal element 3' having the electro-optic effect described above is used. The electro-optic effect is a phenomenon in which the refractive index of a crystal changes when a voltage is applied to the crystal. Crystals with such properties include single crystal l,
There are iNbα, transparent ceramic, Tsuku PLZT, etc. In particular, transparent ceramics, which are crystals having a secondary electro-optic effect, are considered to be promising as elements for optical path switches because they have a large electro-optic effect and can be driven at low voltage.

A crystal element having an electro-optic effect as described above can be produced by applying a voltage (
It has a function of converting the passing light beam into a different polarization direction when the voltage is turned on (ON), and allows the light beam to pass through without changing the polarization direction when the voltage application is released (OFF).

FIG. 1a shows an optical path switching switch using a polarizing beam splitter 5' having the above-mentioned function and an electro-optic crystal element 31.
, b will be explained in detail based on FIG.

As described above, the incident light beam l is a circularly polarized beam, and is composed of two linearly polarized beams far1bTh components whose polarization directions are orthogonal to each other. On the optical path of this incident light beam l, a polarizing element 2' for light selection is arranged to allow only the linearly polarized beam la in one polarization direction to pass through, and the light of the linearly polarized beam la that has passed through the polarizing element 2'. ONN13 mentioned above on the road
A secondary electro-optic crystal element 3' for polarization direction conversion that changes the polarization direction at tOFF is disposed, and the optical path of the polarized beam that has passed through the element 3' is arranged in a perpendicular direction according to the polarization direction of the light beam described above. Alternatively, a beam splitter 5' for polarization separation that emits light in a straight direction is arranged.

As described above, the incident light beam 1 is incident on the polarizing element 2', and only the linearly polarized beam la in one polarization direction is allowed to pass and is incident on the electro-optic crystal element 3'.

Electro-optic crystal element 3' is provided with electrodes on two opposing surfaces parallel to the VcI/i optical path and connected to a power source 4'. The electrode surface is 45 mm with respect to the polarization direction of the light beam passing through it.
°pr4 Slanted.

As shown in FIG. 1a, when no voltage is applied to the electro-optic crystal element 3', the light beam la/ri
The entire beam passes through without changing its polarization direction and enters the polarization beam sinter 5'.

As described above, 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. The linearly polarized beam la that has passed through the crystal element 3' is reflected from the polarizing beam splitter 5' in a perpendicular direction depending on its polarization direction and is emitted.

On the other hand, when a predetermined half-wave voltage is fully applied to the electro-optic crystal element 3' as shown in FIG. It is converted into a direct 1151 polarized beam lb and enters the polarized beam splitter 5'.

Therefore, this linearly polarized beam Ib is
The light is emitted in a straight direction without being reflected at 5'. In the figure, 1a' indicates scattered light emitted in the perpendicular direction when the electro-optic crystal element 3' is turned on.

As explained above, according to the comparative example, the combination of the polarizing beam splitter 5' and the electro-optic crystal element 3' provides an optical path switching switch that can accurately switch the optical path of the incident light beam in two directions. On the other hand, in the optical path switching method described above, the light beam components used are always linearly polarized beams having polarization directions in the vertical and ξ horizontal directions.
Unless either a or tiib is used, the desired optical path switching cannot be achieved, and therefore the other linearly polarized beam must be cut from the incident light and used (in the above comparison column, m
The linearly polarized light beam 1b is cut and linearly polarized light and -Ala are used).

As described above, the biggest problem with the above optical path switching switch is that the light beam emitted onto each switching optical path can always utilize only half of the total amount of incident light, resulting in a 50% optical loss. have.

Similarly to the comparative example above, the present invention uses a beam splitter 1 for polarization separation as an optical path switching element. It was developed to fundamentally solve the problem of optical loss, which was the problem in the comparative example, while employing a crystal element having an electro-optic effect. That is, the present invention comprises a first polarizing beam splitter that is shared by the incident light element and the light output element for the first switching optical path, and a second polarizing beam splitter that is applied to the light output element for the second switching optical path. Regarding the optical path changeover switch consisting of
In cooperation with a crystal element having a circular electro-optic effect, the two linearly polarized beams incident on the first polarized beam splitter and separated are sent to the first switching optical path of the first polarized beam splinter. or the second polarizing beam splitter
High reliability, high sensitivity, and high precision in which substantially the entire amount of incident light is guided onto each of the first or second switching optical paths to obtain optical switching operation by superimposing the incident light onto the switching optical path and emitting it. The present invention aims to provide an optical path changeover switch.

Hereinafter, the present invention will be explained in detail based on FIGS. 2a and 2b.

In the figure, A indicates the incident optical path in the optical path switching switch, A+ indicates the first switching optical path, and A2Fi indicates the second switching optical path. 4 and 5 are polarizing beam splitters that separate the incident light beam into a linearly polarized beam whose polarization direction is perpendicular to the plane of the paper and a linearly polarized beam whose polarization direction is parallel to the plane of the paper, as described above. Polarizing beam splitter, 7, 5 to 2nd polarizing beam splitter 1. It is called tar.

The 11th second polarizing beam splitter-4, 5 is 45°
The tilted polarization separation planes are made parallel to each other and the incident light beam l
are arranged in the same direction on the extension of the optical axis of the first
Polarizing beam splitter, input optical path AI'l above the printer 4:
The second polarizing beam splitter 5 is used as a light emitting element that guides the output light beam 2 onto the above-mentioned switching optical path A+, which is perpendicular to the input optical path AK, and to the first switching optical path A+. The second switching optical path A is parallel.
At the same time, the first polarizing beam splitter 4 is used as a light input element for polarizing and separating the incident light beam 1.

Reference numeral 6 denotes a first reflecting mirror that further reflects in the orthogonal direction the linearly polarized beam la that has been polarized and separated by the first polarized beam splitter 4 and is emitted in the orthogonal direction; 7, the first reflecting mirror 6;
The reflected light beam is further reflected in a perpendicular direction by a second reflecting mirror and enters a second polarizing beam splitter 5.

9 to 12 are first to fourth secondary electro-optic crystal elements PL
ZT, each of the crystal elements 9 to 12 is provided with electrodes on two opposing surfaces that are parallel to the optical path (the electrode surfaces are inclined at 45° with respect to the polarization direction of the light beam passing through).
, 120 set and 10.11 set have switching terminals S+, S
It is connected to the power supply 18 so that it can be switched alternately with
As mentioned above, if no voltage is applied to the crystal element (
When the crystal element is OFF), the light beam passes through it without having its polarization direction changed, and when a voltage is applied to the same crystal element (ON), the light beam passes through this crystal element with its polarization direction changed and exits. do. In order to distinguish between the ON and OFF states of the crystal element 9 on all drawings, the ON crystal element is marked with diagonal lines, and the ON state is marked with diagonal lines.
The same crystal element of F is shown in white.

As shown in FIG. 2a, the first and fourth secondary electro-optic crystal elements 9 and 12 converge the linearly polarized beams la and lbi onto the first polarized beam splinter 4 and superimpose them onto the first switching optical path A+. These are the same crystal elements that are turned ON when emitting light, and as shown in the same figure, second and third secondary electro-optic crystal elements 10.
Reference numeral 11 denotes the same crystal element which is turned on when the linearly polarized beams la and lb are condensed onto the second polarizing beam splitter 5, superimposed onto the second switching optical path A2, and emitted.

Second, the secondary electro-optic crystal element 9 is arranged between the first and second polarizing beam splitters 4 and 5, that is, between the first polarizing beam splitter and the second polarizing beam splitter.
4, the polarized beam is separated and goes straight to the second polarized beam sub-retarder.
5, and the second secondary electro-optic crystal element 1O is placed on the optical path of the linearly polarized beam lb heading towards the second polarizing beam splitter 10 without having its polarization direction converted by the secondary electro-optic crystal element 9. Linearly polarized beam 1 incident on 5 and traveling straight
a, and a third secondary electro-optic crystal element 11
is polarized by the first polarizing beam splitter 4 and emitted in the right angle direction, and is placed on the optical path of the linearly polarized beam la which passes through the mirror 6.7 and heads towards the second polarizing beam splitter 5. The next electro-optic crystal element I2 is the second and first polarization beam splinter 5, 41'JJ f71
] The linearly polarized light enters the second polarizing beam splitter 5 without being converted in its polarization direction by the third secondary electro-optic crystal element 11, is reflected in the right angle direction, and heads toward the first polarized beam splitter 4. It is arranged on the optical path of beam la.

8 is a right-angled prism whose polarization direction is converted by the second secondary electro-optic crystal element 0 and the emitted linearly polarized beam 1akU is turned and re-entered into the second polarized beam sinter 5; 13 is a fourth second polarized beam; A half-wave plate 1 provided on the optical path of the linearly polarized beam 1b whose polarization direction is converted by the electro-optic crystal element 12 and which heads toward the first polarized beam sinter 4.
4 is a secondary electro-optic crystal element 9 whose polarization direction is converted into a second polarized beam splitter 1.4. This half-wave plate is disposed on the optical path of the linearly polarized beam la that is reflected in the right angle direction by the mirror 7.6 and goes to the first polarized beam nullifier 4, and both half-wave plates 13 and 14 has the effect of completely converting the polarization direction of the light beam passing through it (when the linearly polarized beam passing through it is 1a, it is converted to 1b, and when it is 1b, it is converted to la).

15 and 16 are polarizing elements that have the function of blocking scattered light emitted when the secondary electro-optic crystal element is turned on. That is, the polarizing elements 15 and 16 allow only either the linearly polarized beam Filb to pass in the direction perpendicular or horizontal to the plane of the paper. In other words, the passage of light beams other than the light beams in one of the polarization directions is blocked.

The present invention will be further described in detail along with an explanation of its operation as follows.

As mentioned above, Figure 2a is the same as Figure 1. A predetermined voltage is applied from the switch driving power source 18 to the fourth secondary electro-optic crystal elements 9 and 12, and the linearly polarized beams la and ib are sent to the first switching source path A1 using the first polarizing beam splitter 4 as a light emitting element.
This shows an operating state in which one superimposed light beam is output as an output light beam 2.

In the same figure, first, an incident light beam l is input from an incident optical path A to a first (Ii light beam slurritter 4), and the beam slurry 4 produces two linearly polarized light beams la and lb in a straight direction and a right angle direction. Divided into.

The linearly polarized beam la emitted in the orthogonal direction passes through the mirrors 6 and 7, without being changed in polarization direction by the third secondary electro-optic crystal element 11 to which no voltage is applied, and becomes a second polarized beam. The light enters the splitter 5, exits in a perpendicular direction depending on its polarization direction, and enters the fourth secondary electro-optic crystal element 12. Since this crystal element 12Vc is in the ON state due to voltage being applied, the linearly polarized light beam I
The polarization direction of a is changed and it is output as a linearly polarized beam lb. When this polarized beam tb further passes through the half-wave plate 13, its polarization direction is converted again to the original linearly polarized beam la, which passes through the polarizing element 16' and enters the first polarizing beam splitter 4.

This linearly polarized beam la is reflected from the beam splitter 4 in a right angle direction depending on its polarization direction, and is emitted onto the first switching optical path A1.

The scattered light 1b' generated by 0NYc of the fourth secondary electro-optic crystal element 12 is completely blocked by the polarizing element 16.

Note that in Figure 2a, the intention is only to output the light beam onto the first switching optical path A+, and if we ignore the output of the scattered light onto the same switching path A+ in Figure 2A, which will be described later. ,
In the figure, without using the secondary electro-optic crystal element 12, the half-wave plate 13, and the polarizing plate 16',
It is possible to make the linearly polarized beam la' which is reflected by the linearly polarized beam la' and emitted in the right angle direction even if it is incident on the first polarized beam subdirection 4 without reconverting the polarization method described above.

On the other hand, in Figure A, the linearly polarized beam lb split in the straight direction by the first polarizing beam splitter 4 is turned on and then passes through the secondary electro-optic crystal element 9, thereby changing the polarization direction force; and the linearly polarized beam I
a and enters the second polarizing beam splitter 5,
Depending on its polarization direction, it is emitted from the beam splinter 5 in a perpendicular direction, passes through mirrors 7 and 6, and enters a half-wave plate 14. Its polarization direction is changed by passing through the half-wave plate 14, and a linearly polarized beam lb , : and enters the first polarized beam sinter 4. Therefore, this polarized beam lb
is the first polarized beam sinter according to its polarization direction.
4, and is superimposed on the preceding linearly polarized beam la, and is emitted as an output light beam 2 to the I-th switching optical path A].

At this time, when passing through the secondary electro-optic crystal element 9 which is in the ON state, the generated scattered light lb' passes straight through the second polarizing beam splitter 5, and passes through the second secondary electro-optic crystal element which is in the OFF state. Although it reaches the polarizing element 15 through the element lo and the right angle prism 8, it is completely blocked by this, and this scattered light is transmitted to the second polarizing element.
It is possible to avoid a situation where the light enters the polarized beam splinter 5 and is output onto a second switching optical path A2, which will be described later.

As mentioned above, two linearly polarized beams la are input from the incident optical path A to the first optical beam splitter 4 and are separated.
, Ib is refocused onto the first polarization beam splitter 4 via the second polarization beam splitter 5 in cooperation with the secondary electro-optic crystal element 9° 12, and superimposed on the first switching optical path A+. Approximately 100% of the light beam incident from optical path A (including optical loss due to scattered light) can be used for optical path switching.

Furthermore, Figure 2A is the opposite of Figure 1A;
The fourth secondary electro-optic crystal elements 9 and 12 are turned off, and the second
, a third secondary electro-optic crystal element 10, 1lkONK, and a second polarizing beam splitter 5 as a light emitting element to superimpose both linearly polarized beams la and Ib on a second switching optical path A2 and output it as an output light beam 3. Indicates operating status.

As before, the incident light beam l incident from the incident optical path A
is separated into linearly polarized beams la and lb in a direction perpendicular to the straight direction by a first polarizing beam splitter 4 and emitted.

First, the linearly polarized beam la emitted from the first polarized beam splitter 4 in the perpendicular direction passes through the mirror 6.7 and is turned on.
The polarized light beam is incident on the secondary electro-optic crystal element 11 which is in the state, and its polarization direction is converted during passage, becoming a linearly polarized beam tb and incident on the second polarized beam sinter 5.

According to its polarization direction, this original beam lb travels straight through the second polarizing beam splitter 5, and is emitted as three negative beams of the output light beam 3 to the second switching optical path A2. At this time, the scattered light 1a' generated by the third secondary electro-optic crystal element 11 which is in the ON state is reflected by the second polarizing beam sinter 5, and is reflected by the fourth secondary electro-optic crystal element 12 which is in the OFF state. The scattered light 1b' passes through the plate 13 and reaches the polarizing element 161C, thereby completely blocking it.

In the diagram in the other direction, the linearly polarized beam tb emitted from the first polarized beam splitter 4 in the straight direction is in an OFF state [passes through the first polarized beam splitter 9 without undergoing any conversion of the polarization direction. second polarizing beam splitter 5
and is emitted in a straight direction according to its polarization direction.
It enters the second secondary electro-optic crystal element 10 in the N state, is converted into a linearly polarized beam la by the element 10, is U-turned at the tm right angle rhythm 8, passes through the polarizing element 15, and is transmitted to the second polarizing beam splitter. 5.

According to its polarization direction, this light beam la is reflected by the second polarization beam sinter 5 and is superimposed on the linearly polarized light beam lb, and is sent to the second switching optical path A as an output light beam 2.
This leads to the emission to 2.

At this time, the second secondary electro-optic crystal element l in the ON state lCa3
The scattered light 1 generated by O is completely blocked by the polarizing element "151c" before the -J2 polarizing beam splitter 5.

As described above, the two linearly polarized beams ta and 1b, which are incident on the first polarizing beam splitter 4 from the incident optical path A and separated in two directions, cooperate with the secondary electro-optic crystal element 10.11. It is possible to refocus the light onto the second polarizing beam splitter 5 and to superimpose it onto the second switching optical path A2 and output it, and approximately 100% of the light beam l incident from the optical path A is used for optical path switching. be able to.

The present invention cleverly employs the secondary electro-optic effect of a secondary electro-optic crystal element, which is suitable as an optical path switching element, and the polarization separation effect of a polarizing beam splitter, and uses the first polarizing beam splitter for the first switching optical path. The light emitting element and the second polarizing beam splitter are used as the light emitting element for the second switching optical path, and the first polarizing beam splitter is also used as the incident optical element, thereby forming two sets of one electro-optic crystal element. This is the first to provide a 7-inch optical path switching device in which the entire amount of the incident light beam is emitted onto each of the first and second switching optical paths by alternately turning ON and OFF.

Comparison F! II! As shown in Figure 2, the basic concept of an optical path switching switch that uses an electro-optic crystal element and a polarizing beam splitter is to alternately convert a linearly polarized beam having one polarization direction and use it for switching the optical path. It was said that the increase in a stalk and the optical loss of 50% of the amount of incident light due to light scattering when the electro-optic crystal element is ON cannot be avoided. Each of the polarizing beam sinters is used as an exit window for two switching optical paths, and one is used as a window for an input optical path,
A combination of this and an electro-optic crystal element solves the problem of the above-mentioned contrast array, and as described above, almost the entire amount of the incident light beam is guided to each of the first or second switching optical paths to perform optical switching. Highly sensitive and highly reliable optical path switching switch designed to provide optimal operation.
This is what Sochi offers.

In the conventional method of outputting the original beam from a single polarizing beam splitter to the first switching source path and the second switching optical path, elements are arranged to prevent the scattered light from being removed due to the structure (naturally, it is not possible to remove the scattered light). If the beam is placed on the optical path of the original beam), it is possible to switch one optical path, but when switching the other optical path, the originally necessary normal original beam will be blocked, making it impossible to accomplish the purpose of optical path switching. Scattered light cannot be removed, and it has been considered almost impossible to prevent crosstalk caused by this.

Therefore, the non-invention is to direct the linearly polarized beam I onto the first switching optical path A+.
The first element dedicated to a, Ibk synthesis and output
The optical switching system is equipped with a polarizing beam splitter 4 and a dedicated second polarizing beam splitter 5 as an element for combining and outputting the linearly polarized beam 1 a rlbe onto the second switching source path A2. Since the basic configuration adopts a system in which the light beams 2.3 to be used for optical path switching are emitted from the element, there is a path for guiding the light beams la and lb to the first switching optical path A+, and a path for guiding the light beams la and lb to the second switching source path A2. Therefore, when the original beam 2 is emitted from the first polarizing beam splitter 4 onto the first switching optical path, the scattered light is 2 polarizing beam splitter-5
Similarly, when the light beam 3 is emitted from the second polarizing beam splitter 5 onto the second switching optical path A2, the scattered light is blocked by the path before reaching the first polarizing beam splitter. It is possible to adopt a configuration in which the block is cut off at the path before reaching -4, and flJ is effective in preventing crosstalk caused by light scattering, which was considered to be a fatal flaw in optical path switching switches, as exemplified in Fig. 2. It has now become possible to realize an optical path changeover switch that can handle this problem.

[Brief explanation of the drawing]

Figures 1a and 1b are perspective views showing the principle of an optical path changeover switch in contrast to the present invention by means of element arrangement, and Figure 1a is a perspective view showing the principle of an optical path changeover switch in contrast to the present invention. The same figure shows the optical path switching state when the same voltage is applied. Figures 2a and 2b show an optical path switching switch showing an embodiment of the present invention;
A perspective view showing the Sochi principle using the element arrangement.
The figure shows an optical path switching state when a light beam is emitted from a first polarizing beam splitter onto a first switching optical path by applying a voltage to one set of two sets of secondary electro-optic crystal elements. , the same figure shows an optical path switching state in which the original beam is emitted from the second polarizing beam splitter onto the second switching optical path by applying a voltage to the same crystal element of the other set. A...Incoming optical path, A...First output optical path, A2...
...Second output optical path, l...Incoming light beam (input), t
a+xb...linearly polarized beam, 2...outgoing light beam (output) to the first outgoing optical path, 3... outgoing light beam to the second outgoing optical path, 4...light input element of the incoming optical path and a first @ optical beam splitter 15 which shares a light output element to the first output optical path...second polarizing beam splitter 16, 7 which is a light output element to the second output optical path...reflection mirror, 8・・・
・Right angle prism, 9, 14... □ to the first switching optical path
11th and 4th secondary electro-optic crystal elements that are in the ON state when switching the optical path; 11.12...2nd and 3rd secondary electro-optic crystal elements that are in the ON state when switching the optical path to the second switching source path; Next electro-optic crystal element, 13.14... Half-wave plate, 15.1
6...Polarizing element, 18...Power source.

Claims (1)

[Claims] a first polarizing beam splitter arranged in parallel on the same optical axis;
a second polarizing beam splitter, the first polarizing beam splitter is used as a light emitting element for the first switching optical path, the second polarizing beam splitter is used as a light emitting element for the second switching optical path, and the first polarizing beam splitter is used as a light emitting element for the second switching optical path, and The first polarized beam splitter is also used as a light input element, and the two linearly polarized beams that enter the first polarized beam splitter and are separated between the eleventh and second switching optical paths and the input optical path are converted into "second polarized beams". A path for refocusing the light onto the first polarizing beam splitter through the beam splitter, superimposing it on the first switching optical path, and emitting it.''
A path for condensing light onto a second polarized beam sinter, superimposing it on the second switching optical path, and emitting it, and an electro-optic crystal element is arranged on each of the above-mentioned paths, and an electro-optic crystal element is arranged alternately on the second switching optical path.
N, 0FFK: An optical path switching switch, characterized in that it is configured to switch between the two paths.