JPH04296667A - High-speed voltage measuring device - Google Patents

Abstract

PURPOSE:To measure voltage at good linearity and S/N ratio, even if the voltage is small, without converting, etc., output, of a light detector based on input/ output characteristics. CONSTITUTION:A high-speed voltage measuring device 10 is constructed by arranging a light source 12, a polarizer 14, a light modulator 16 onto which an electric signal to be measured is applied, a polarization interferometer 18, a streak camera 20, and a processing device 22, in that order. By utilizing the fact that interference fringes are formed on the input surface of the streak camera 20 by means of the polarization interferometer 18 and the fringes move according to the electric signal to be measured applied to the light modulator 16, the amount of movement is detected by the streak camera 20 for voltage measurement.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high-speed voltage measuring device using an electro-optic crystal.

0002

2. Description of the Related Art Conventionally, there is a high-speed voltage measuring device 1 as shown in FIG. 6, for example.

This high-speed voltage measuring device 1 includes a light source 2, a light intensity modulator 4 consisting of a polarizer 4A, a light modulator 4B, and an analyzer 4C, a high-speed photodetector 6 consisting of, for example, a streak camera, and a processing device. 7, and a display device 8. The light from the light source 2 is input to the optical intensity modulator 4, and the optical modulator 4B undergoes a refractive index change depending on the input electrical signal to be measured. As a result, the optical modulator 4B changes the state of polarization of the input light. The intensity changes, and is converted into intensity changes by the analyzer 4C and input to the high-speed photodetector 6.

The voltage V applied to the optical modulator 4B and the analyzer 4
As shown in FIG. 7, there is a relationship between the output light intensity I input to the high-speed photodetector 6 via C and the following equation (1).

I=I0 sin 2 (π/2・V/Vπ)
...(1)

[0006] Here, Vπ is a half-wave voltage, which is determined based on the performance of the optical modulator 4B.

Therefore, the high-speed photodetector 6 detects light whose intensity is modulated by the electrical signal to be measured based on the above equation (1).

[0008]

In the conventional high-speed voltage measuring device 1 as described above, as shown in FIG.
The voltage V applied to the optical modulator 4B and the output light intensity I after passing through the analyzer 4C have a relationship of a sin 2 function and are not a proportional relationship. Therefore, in order to calculate V from I, the processing device 7 must , it is necessary to convert based on the output characteristics shown in FIG.

In this case, if V is small, there is a small change in I with respect to a change in V, so there is a problem that accurate measurement is difficult.

[0010] Furthermore, since the amount of light detected by the high-speed photodetector 6 is small, there is a problem that the S/N ratio becomes poor.

The present invention was made in view of the above-mentioned conventional problems, and it is possible to easily measure even small voltages without using conversion based on input/output characteristics. Furthermore, it is an object of the present invention to provide a high-speed voltage measuring device with a good S/N ratio.

0012

[Means for Solving the Problems] The present invention provides a light source that outputs polarized light, an optical modulator using an electro-optic crystal,
A polarization interferometer and a high-speed one-dimensional photodetector are arranged in this order, and interference is formed on the input surface of the photodetector in response to changes in the electrical signal applied to the optical modulator. The above object is achieved by a high-speed voltage measuring device that detects the voltage of the electric signal based on the amount of movement of the stripes.

The polarization interferometer may include a birefringent crystal and an analyzer in this order from the light input side.

The polarization interferometer is composed of a single slit and a double slit parallel to the single slit, and polarizers with polarization directions of +45° and -45° with respect to the longitudinal direction of the single slit are connected to the double slit. A Young's interferometer is provided in each slit, and a Young's interferometer is provided on the optical output side of the Young's interferometer, and the polarization direction is 4 with respect to the polarizer.
It may also consist of analyzers that differ by 5 degrees.

[0015]

[Operations and Effects] According to the present invention, a polarization interferometer generates interference fringes according to the polarization state of incident light, and when an electrical signal to be measured is applied to the input side of this polarization interferometer, An optical modulator that outputs an output with a changed polarization state is provided, and the interference fringes move in proportion to the voltage applied to the optical modulator.

By detecting the amount of movement of this interference fringe using a high-speed one-dimensional photodetector, the voltage of the electrical signal to be measured can be measured.

Since there is a proportional relationship between the voltage change of the electrical signal to be measured and the amount of movement of the interference fringes, it is easy to perform conversion without performing conversion based on input/output characteristics as in the conventional high-speed voltage measuring device shown in FIG. voltage can be measured.

Furthermore, for the same reason, the linearity between the voltage and the amount of movement of the interference fringes is good, and high measurement accuracy can be obtained. It has the excellent effect of being able to

[0019]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Examples of the present invention will be described below with reference to the drawings.

As shown in FIG. 1, a high-speed voltage measuring device 10 according to an embodiment of the present invention includes a light source 12 and a polarizer 14.
, an optical modulator 16 made of an electro-optic crystal to which an electrical signal to be measured is applied, a polarization interferometer 18 , and this polarization interferometer 1
The streak camera 20 that receives the output light from the streak camera 20, the processing device 22 that processes the output signal of the streak camera 20, and the display device 23 are arranged in this order from the light source 12 side. The voltage of the electric signal is determined based on the amount of movement of the interference fringes formed on the input surface of the streak camera 20 in response to changes in the electric signal applied to the streak camera 16.

The polarizer 14 can be omitted if the output light from the light source 12 is polarized.

As shown in FIG. 2, the polarization interferometer 18 includes an objective lens 24, a birefringent crystal 26, and an analyzer 2.
8 are arranged in this order.

The polarization direction of the analyzer 28 is arranged at an angle of 45° with the optical axis of the birefringent crystal 26.

As shown in FIG. 3, the streak camera 20 is set so that its entrance slit 20A crosses the interference fringes.

The processing device 22 also includes a streak camera 2.
The applied voltage V is determined from the interval A between the peak values of the interference fringes obtained at 0 and the amount of movement X of the peaks based on equation (2) described later.

Next, the operation of the apparatus of the above embodiment will be explained.

When polarized light enters the polarization interferometer 18 , it is expanded by an objective lens 24 and enters a birefringent crystal 26 .

In this birefringent crystal 26, the input beam is split into two polarization states, one in the direction determined by the optical axis of the crystal and the other in the direction perpendicular to this, and propagates along different paths.
An optical path difference is given to the two output lights.

As described above, the analyzer 28 is arranged so that its polarization direction is at an angle of 45° with the optical axis of the birefringent crystal 26, so that the polarization state of the light emitted from the birefringent crystal 26 is The two orthogonal beams interfere after passing through the analyzer 28, and interference fringes are formed at the entrance slit 20A, which is the input surface of the streak camera 20.

On the other hand, the optical modulator 16 changes the polarization state of the incident light according to the applied voltage and outputs it to the polarization interferometer 18.

Therefore, the interference fringes formed on the input surface of the streak camera 20 by the polarization interferometer 18 move in proportion to the change in the polarization state by the optical modulator 16, that is, the change in the applied voltage.

The movement amount X of the interference fringes at this time is given by the following equation (2), where the interval between the interference fringes is A, the voltage applied to the optical modulator 16 is V, and the half-wavelength voltage is Vπ. It turns out.

[0033]X=A/2・V/Vπ...(2
)

For example, an example of the output of the streak camera 20 when measuring an electric signal that changes in a step function manner is as shown in FIG. The peak positions (channels) of the output due to interference fringes when no voltage is applied to the optical modulator 16 (time T1) are A1 to A in FIG.
3. Here, the vertical axis in FIG. 4 represents time, and the horizontal axis represents the position of the entrance slit 20A.

The processing device 22 obtains the channels A1 to A3 of the three peaks, and obtains the interval A of the interference fringes from them.

Next, at time T2, when the electrical signal to be measured is applied to the optical modulator 16, the interference fringes move;
The peak channels B1 to B3 of the output of the streak camera 20 based on the interference fringes at
~A3, the amount of movement X of the interference fringes can be determined.

From this movement amount X, the interval A of the interference fringes, and the known Vπ, the voltage V can be determined as described above.

By performing such calculations at all times in the processing device 22, the waveform of the electrical signal to be measured can be determined.

Note that the streak camera 20 can measure not only repeated phenomena but also electrical signals to be measured as single phenomena.

In the above embodiment, the angle between the polarization direction of the analyzer 28 and the optical axis of the birefringent crystal 26 is 45°.
However, it is sufficient that they do not match or orthogonally intersect.

In the above embodiment, the polarization interferometer 18 includes the birefringent crystal 26, but the present invention is not limited to this, and the polarization interferometer may have other configurations.

For example, as shown in FIG. 5, it consists of a single slit 30 and a double slit 32 parallel to this, and polarized light with polarization directions of +45° and -45° with respect to the longitudinal direction of the single slit 30. Child 34A, 34
It may be constructed from a Young's interferometer 36 made of B and an analyzer 38 which is provided on the light output side of the Young's interferometer 36 and whose polarization direction differs by 45 degrees from the polarizer 14.

The light input to the Young's interferometer 36 is
The light is diffracted by the single slit 30, spreads out, and enters the double slit 32.

Since the double slit 32 is provided with polarizers 34A and 34B whose polarization directions are orthogonal to each other, the light whose polarization states are orthogonal to each other is generated.
34B, and after passing through the analyzer 38, they interfere and form interference fringes on the input surface of the streak camera 20.

When the electrical signal to be measured is applied to the optical modulator 16, the phase difference between the two lights with orthogonal polarization states changes, and the interference fringes move in accordance with this change in phase difference.

In the above embodiment, the polarizer 34A,
The polarization direction of 34B is not limited to +45° or −45° with respect to the longitudinal direction of the single slit 30, and it is sufficient that they do not coincide. Further, the polarization direction of the analyzer 38 does not need to match that of either of the polarizers 34A and 34B.

In the above embodiment, interference fringes are detected using the streak camera 20, but the present invention is not limited to this, and may be a high-speed one-dimensional photodetector that detects light at high speed. Good to have.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing an embodiment of a high-speed voltage measuring device according to the present invention.

FIG. 2 is a block diagram showing an example of a polarization interferometer in the same embodiment.

FIG. 3 is a perspective view showing the positional relationship between a streak camera and interference fringes in the apparatus of the embodiment.

FIG. 4 is a diagram showing an example of the output of the streak camera.

FIG. 5 is a block diagram showing another example of the polarization interferometer in the embodiment.

FIG. 6 is a block diagram showing a conventional high-speed voltage measuring device.

7 is a diagram showing the relationship between the voltage applied to the optical modulator and the output of the photodetector in the high-speed voltage measuring device of FIG. 6. FIG.

[Explanation of symbols]

10...High speed voltage measuring device, 12...Light source, 14, 34A, 34B...polarizer, 16...light modulator, 18...Polarization interferometer, 20...Streak camera, 22...processing device, 23...Display device, 26...birefringent crystal, 28, 38...Analyzer, 30...Single slit, 32...double slit, 36...Young's interferometer.

Claims (5)

[Claims] 1. A light source that outputs polarized light, an optical modulator using an electro-optic crystal, a polarization interferometer, and a high-speed one-dimensional photodetector, which are arranged in this order, The voltage of the electric signal is detected based on the amount of movement of interference fringes formed on the input surface of the high-speed one-dimensional photodetector in response to changes in the electric signal applied to the detector. High-speed voltage measurement device. 2. A high-speed voltage measuring device according to claim 1, wherein the polarization interferometer comprises a birefringent crystal and an analyzer in this order from the light input side. 3. In claim 1, the polarization interferometer includes a single slit and a double slit parallel to the single slit, and is arranged at an angle of +45° with respect to the longitudinal direction of the single slit.
A Young's interferometer is provided with a polarizer having a polarization direction of -45° in each slit of the double slit, and a Young's interferometer is provided on the optical output side of the Young's interferometer, and a polarizer having a polarization direction of −45° A high-speed voltage measuring device characterized by having an analyzer that differs by 45 degrees. 4. In claim 1, 2 or 3, the high speed 1
The dimensional photodetector is a high-speed voltage measurement device characterized by being a streak camera. 5. A high-speed voltage measuring device according to claim 1, wherein the light source is comprised of a light source that outputs unpolarized light and a polarizer.