JPH0133807B2 - - Google Patents

Description

[Detailed Description of the Invention] <<Field of Industrial Application>> The present invention relates to an improvement of an optical gate device that blocks light in stages and is effective for use in optical power meters, optical power calibrators, etc. .

<<Prior Art>> As a technology related to an optical gate device, an example of an optical power calibrator shown in FIG. 6 will be explained. 1 is a dark room, 2 is a reference light source, 3 is a slit having a certain hole, and 4 is a photodetector. 5 is a first lens for collimating the light from the reference light source 2 from the slit 3; 6 is a light shielding means for limiting the amount of light transmitted from the first lens; 7 is a light shielding means 6; This is a second lens for converging the transmitted light. 8 is a shielding control means for controlling the shielding amount of the light shielding means 6; 9 is a shielding control means for controlling the shielding amount of the light shielding means 6; 9 compares and calculates the relationship between the shielding amount control signal of the light shielding means 6 and the output signal from the photodetector 4; This is a display means for displaying on a plotter.

FIG. 7 is a diagram illustrating details of the light shielding means 6,
A plurality of electrodes 21a, 21b, ... 21n are provided on a substrate 20 made of an electro-optic material such as PLZT, and a first polarizing plate 22 and a second
polarizing plates 23 are arranged so that their polarization planes are perpendicular to each other, and each electrode 21 provided on the substrate 20
A, 21b, . A transmission window is configured so that the light passes through the two polarizing plates 23, and the application of the electric field is controlled by the shielding amount control means 8.

In the power calibrator configured as described above, if an arbitrary number of transmission windows are opened (or closed), an amount of light proportional to the number of transmission windows is transmitted to the photodetector 4.
The output signal of the shielding amount control means 8 and the electrical signal of the photodetector 4 at that time are input to the display means 9, and the calculations and comparisons are performed and displayed on a CRT or plotter. Calibration can be performed.

<<Problems to be solved by the invention>> However, the light shielding means 6 used
PLZT gate array elements become PLZT over time.
Since the electro-optical effect of the switch changes, when used as a switch, it induces a drift in the output, which has the disadvantage of deteriorating accuracy and linearity. This is especially a problem when the light energy is high.

The present invention has been made to solve the above problems, and an object of the present invention is to realize an optical gate device in which output drift occurring in an optical gate array element is reduced.

<<Means for Solving the Problems>> The first optical gate device according to the present invention relates to an optical gate device that blocks input light in stages, and the first polarizing beam splitter divides the input light into two. The polarized light is divided into two optical paths, and each polarized light is passed through two optical gate arrays using electro-optic elements. The two optical gate arrays alternately rotate the polarization plane of the passing light by a stepwise set amount of light, and the second polarization beam splitter alternately outputs two polarized lights with stepwise set amounts of light. It is characterized by being configured so that

A second optical gate device according to the present invention is characterized in that the above optical gate device is configured such that the average value of one cycle of the drive signal output from the control circuit to the optical gate array is zero. .

<<Operation>> According to the configuration according to the first aspect of the present invention, since the time for applying a drive signal to each optical gate array is shortened, the amount of drift occurring in each optical gate array can be reduced.

Further, according to the configuration according to the second invention of the present invention,
Drifts can be canceled by applying drive signals with opposite polarities.

≪Example≫ The present invention will be explained in detail below using the drawings.

FIG. 1 shows an example in which the optical gate device according to the present invention is applied to an optical power calibrator.
FIG. 2 is a configuration explanatory diagram showing one in which two optical gate arrays are used alternately. 32 is a reference light source, 35 is a lens that focuses the light emitted from this reference light source 32, and 36
61 and 64 are light shielding means for limiting the amount of light transmitted from this lens 35, and 61 and 64 are first and second light shielding means.
62 and 63 are total reflection prisms, 65 and 66 are collimators with the same characteristics that limit the width of the beam, and 67 and 68 are irradiated with two polarized waves output from the polarization beam splitter 61, respectively. of the same characteristics installed as
The PLZT optical gate array 37 is a condensing lens for condensing light onto the photodetector 34. 67, 68
The PLZT optical gate array has the electrode 21 shown in Figure 7.
Electrodes similar to a, 21b, . . . 21n are provided. A control circuit 38 generates control signals Q ₁ and Q ₂ for driving the gates of the optical gate arrays 67 and 68. The polarizing beam splitters 61 and 64 and the total reflection prisms 62 and 63 constitute means for splitting input light into a plurality of optical paths.

The operation of the apparatus having such a configuration will be described next. Now 2
A case will be described in which two optical gate arrays 67 and 68 alternately switch the amount of light of one unit. The light emitted from the light source 32 is separated into P waves and S waves by a polarizing beam splitter 61, and the P waves enter an optical gate array 68 and the S waves enter an optical gate array 67, respectively.

An electro-optic effect occurs in which the optical gate array 67 is turned on, and the polarization plane of the S wave passing through it is rotated by 90 degrees to become a P wave, which is output in the A direction via a total reflection prism 63 and a polarizing beam splitter 64. Ru. On the other hand, since the optical gate array 68 is turned off, no electro-optic effect occurs, and the P wave passing therethrough is output in the B direction via the polarizing beam splitter 64.

Conversely, when the optical gate array 68 is turned on, an electro-optic effect occurs, and the polarization plane of the P wave passing through it is rotated by 90 degrees to become an S wave, which is output in the A direction via the polarizing beam splitter 64. . On the other hand, since the optical gate array 67 is off, no electro-optic effect occurs.
The S wave passing through this is outputted in the B direction via a total reflection prism 63 and a polarizing beam splitter 64.

When this is repeated in the To period, one unit of light that has passed through different optical gate arrays is output alternately, and as a result, the output light in the B direction becomes as shown in the time chart in Figure 2. Even when multiple units of light intensity are set in the optical gate array, multiple units of light are similarly output alternately, so the output light intensity in the B direction with respect to the number of optical gates changes as shown in the characteristic curve diagram of FIG. 3.

By switching the optical gate array at the To period in this manner, the adverse effects of PLZT drift can be reduced.

Also, since there are no moving parts, it is superior in terms of speed and reliability. For example, by switching the output light amount at high speed in an optical power calibrator, the time required for calibration can be significantly shortened.

In the above embodiment, control signals Q ₁ and Q ₂ of the same polarity were used, but as shown in the time chart in FIG. If a signal is applied from the control circuit to each optical gate array, the drifts in opposite directions that occur in the PLZT due to applied voltages of different polarities can be canceled out, and the drifts can be further reduced.

Furthermore, in each of the above embodiments, if the optical output in the A direction is also used, it is possible to calibrate two photodetectors at the same time.

Furthermore, in each of the above embodiments, as shown in FIG. It is possible to obtain an output light amount of .

Furthermore, in each of the above embodiments, a plurality of PLZTs and collimators (for example, the first
By arranging the PLZT (perpendicular to the plane of the drawing) and sequentially switching between them, the usage time per PLZT can be shortened and drift can be further reduced.

<<Effects of the Invention>> As described above, according to the present invention, it is possible to realize an optical gate device that reduces the output drift that occurs in an optical gate array element, and it is possible to realize an optical gate device that reduces the output drift that occurs in an optical gate array element. , linearity can be improved.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram of the configuration of an optical power calibrator to show an embodiment of the optical gate device according to the present invention, FIG. 2 is a time chart to explain the operation of the device shown in FIG. 1, and FIG. Fig. 1 is a characteristic curve diagram for explaining the operation of the device, Fig. 4 is a time chart for explaining the operation of a modification of the device in Fig. 1, and Fig. 5 is another modification of the device in Fig. 1. FIG. 6 shows an example of a related optical power calibrator, and FIG. 7 shows a light shielding means used therein. 38... Control circuit, 61... First polarizing beam splitter, 64... Second polarizing beam splitter, 66, 67... Optical gate array, Q ₁ , Q ₂ ...
...Drive signal.

Claims (1)

[Scope of Claims] 1. An optical gate device that blocks input light in stages, including a first polarizing beam splitter that splits the input light into two optical paths, and a second polarizing beam splitter that outputs from the first polarizing beam splitter. two optical gate arrays each using an electro-optical element that inputs two polarized beams; a second polarizing beam splitter that inputs the transmitted light of these two optical gate arrays from different surfaces; a control circuit for driving the control circuit to alternately rotate the polarization plane of the passing light by a stepwise set amount of light;
1. An optical gate device characterized in that the polarization beam splitter is configured to alternately output two polarized lights with stepwise set amounts of light. 2. In an optical gate device that blocks input light in stages, there is a first polarizing beam splitter that splits the input light into two optical paths, and two polarized lights emitted from this first polarizing beam splitter are respectively incident. Two optical gate arrays using electro-optical elements, a second polarizing beam splitter that makes the transmitted light of these two optical gate arrays incident from different surfaces, and the two optical gate arrays are set in stages. The control circuit is provided with a control circuit that is driven by a drive signal whose average value in one cycle is 0 so as to alternately rotate the polarization plane of the passing light by the amount of light, and the control circuit is set in stages from the second polarization beam splitter. What is claimed is: 1. An optical gate device characterized in that the optical gate device is configured such that two types of polarized light having different amounts of light are outputted alternately.