JPH02134576A - High speed voltage measuring apparatus - Google Patents

Abstract

PURPOSE:To sample a plurality of voltages to be measured within one cycle by recombining the light pulse passing through a variable delay means and the light pulse passing through both of the variable delay means and an auxiliary delay means to allow both of them to be incident to an electro-optical modulator. CONSTITUTION:A light branch device 207A is provided to the post stage of a variable delay means 202 and an auxiliary delay means 209 is provided on the auxiliary light path 208B branched from said branch device 207A. Further, a discrimination function adding means 203B is provided to the auxiliary light path 208B. This means 203B adds discrimination function to the light pulse passing through the circuit 209 in the same way as the discrimination function adding means 203A provided to a main light path 208A. Both light pulses to which discrimination function added are combined by a light coupler 212 to be sent into an electro-optical modulator 100. The light pulse PM1 passing through the means 209 is delayed by a delay time tau1 from the original light pulse LP and the light pulse branched to the auxiliary light path 208B becomes a light pulse PM2 further delayed by a delay time tau2. As a result, two light pulses PM1, PM2 are obtained from the light pulse coupler 212 within one cycle T.

Description

DETAILED DESCRIPTION OF THE INVENTION "Field of Industrial Application" The present invention relates to a high-speed voltage measuring device that can be used to measure the response characteristics of an element that requires a high-speed response, such as a photo-electrical conversion element.

``Prior Art'' The waveform of a steeply rising pulse requires a high-speed response waveform observation device to measure the response characteristics of a photo-electrical conversion element.

Cathode ray tube oscilloscopes are widely used as waveform observation instruments, but because this type of waveform observation instrument has a structure in which the voltage to be measured is taken from the measurement point through a cable, high-frequency components contained in high-speed signals may be absorbed by the stray capacitance of the cable. The problem is that the waveform is attenuated, making it difficult to observe the true waveform.

For this reason, high-speed waveform observation devices using electro-optic modulators are being considered.

The structure and operation of the electro-optic modulator will be explained using FIG. 7.

In the figure, 100 indicates the entire electro-optic modulator.

The electro-optic modulator 100 includes a light-transmitting crystal 101, a polarizer 102 disposed on the light incident side of the crystal 101,
It is composed of an analyzer 103 placed on the light output side of the crystal body 101 and a pair of electrodes 1104A and 104B attached to the crystal body 101. Note that 105 indicates a compensation wave plate.

The electrodes 104A and 104B are arranged facing each other in a direction perpendicular to the optical axis of the crystal body 101.
During 04B(7), the voltage signal to be measured (■) is given from the signal to be measured a106.

In the crystal body lot, an electric field corresponding to the voltage value of the voltage signal to be measured (■) is generated in a direction perpendicular to the optical axis, and this electric field rotates the direction of the polarization plane of the light passing through the crystal body 101. The rotation of the analyzer 103 changes the amount of light that can pass through the analyzer 103, and the amount of output light I changes.

For example, when the polarization axis of the polarizer 102 and the polarization axis of the analyzer 103 are arranged in a relationship that is perpendicular to each other, the amount of transmitted light is O when the voltage signal to be measured (2) is zero.

On the other hand, when the voltage to be measured (■) is gradually increased, the crystal body 10
1 rotates, and the amount of light that can pass through the analyzer 103 gradually increases.

When the rotation of the polarization plane in the crystal body 101 reaches 90°, the analyzer 103 detects almost 100% of the incident light I.

The maximum amount of light is transmitted.

When the voltage applied to the crystal body 101 is further increased, the polarization plane of the light passing through the crystal body 101 exceeds 90°, so that the amount of emitted light gradually decreases.

This situation is shown in FIG. 8. As can be seen from this figure, the amount of output light I changes from O to the amount of incident light depending on the voltage value applied to the crystal body 101! It exhibits changes that go back and forth between . This change in the amount of emitted light is 1-1 osin'' αV-teleral.

In normal measurements, the output light ill is 0 to 1. Use a range between. Output light amount! is 1. The voltage until it reaches is called the half-wave voltage ■. Half-wave voltage ■, is crystal 101
Although it is determined by the distance d between the electrodes 104A and 104B sandwiching the electrodes 104A and 104B, it is possible to make a high voltage voltage of about 100 volts to about 1000 volts.

Note that the compensating wave plate 105 is provided to adjust the output light amount I to be 0 when the voltage to be measured V is 0.

FIG. 9 shows a conventional high-speed waveform observation device using this electro-optic modulator 100.

The electro-optic modulator 100 includes a crystal body 10 as described above.
1, a polarizer 102 provided on the incident side, an analyzer 103 provided on the output side, and a pair of electrodes 1 attached to the crystal body 101.
04A, 104B and the compensating wavelength plate 105 provided between the analyzer 103 and the crystal body 101, which is the same as the previous explanation.
An example is shown in which a lens 107 is provided between the crystal body 101 and the crystal body 101 and the analyzer 103.

A light pulse incident on the electro-optic modulator 100 is provided by a short pulse laser oscillator 200. A short-pulse laser beam emitted from the short-pulse laser oscillator 200 is split into two by an optical splitter 201 .

One of the two divided lights is guided to the main optical path that enters the electro-optic modulator 100, and the other light is given to a trigger pulse generation circuit 301 that gives a trigger signal to the object to be measured 300.

The optical pulse branched into the incident optical path of the electro-optic modulator 100 passes through the variable delay means 202 and the identification function adding means 203 which gives an identification function to the optical pulse, and is electro-optically modified! 11
1100.

In this example, the variable delay means 202 uses a variable delay means having a structure in which the amount of delay of the optical pulse is changed by changing the optical path length.

In other words, the reflector 202A placed at an angle of 90' is the driving bag! 202B, and the light amount length is changed by the movement of the reflection m202A to control the delay amount of the light pulse.

On the other hand, the identification function adding means 203 adds a function to the optical pulse to identify that it is measurement light. For this purpose, for example, the optical pulse train LP is set at a predetermined frequency 6r as shown in FIG. 10 using an acousto-optic modulator.

This can be realized by modulating into a pulse modulated wave PM having the following values. MP indicates a modulation signal given to the acousto-optic modulator.

In this way, by modulating the optical pulse train LP into a pulse modulated wave PM having a frequency f, it is sufficient to amplify the electrical signal having a frequency r on the extraction side, and in this way, the measurement signal is acquired with a good S/N ratio. be able to.

The light emitted from the electro-optic modulator 100 is transmitted to the photodetector 20.
4, it is converted into an electrical signal and input to the discriminator 205.

For example, a lock-in amplifier can be used as the discriminator 205. This discriminator 205 amplifies only the signal having the frequency r, and outputs a DC voltage corresponding to the amplitude value of the signal having the frequency f. Identification function addition means 2
The modulated signal MP to be supplied to the discriminator 205 is sent from the discriminator 205.

In other words, as shown in FIG.
The optical pulse train LP output from the variable delay means 202
As shown in FIG. 11B, if the input is delayed by τ and is input to the electro-optic modulator 100, then the DC voltage ■ corresponds to the value of the measured voltage signal ■ at this input timing.

, is output from the discriminator 205.

Therefore, by gradually delaying the amount of delay of the optical pulse PM incident on the electro-optic modulator 100, the DC voltage (2) is output from the discriminator 205. , gradually changes in response to the measured voltage ■.

Therefore, by applying and displaying the change in the DC voltage output from the discriminator 205 on the display 206, the measured voltage signal (2) can be converted into a slow signal and observed.

In this way, a signal that changes at a high speed is sampled by the electro-optic modulator 100, and by sequentially shifting the timing of the sampling, a signal that changes at a high speed is converted into a signal that changes slowly, so that the display 206 is normally used. High-speed signals can be observed using a cathode ray tube oscilloscope.

``Problem to be Solved by the Invention'' The high-speed waveform observation device described above samples the voltage signal to be measured by applying a light pulse once per cycle.

Therefore, in order to sample the data corresponding to the entire period of the voltage signal under test, the voltage signal under test must be sampled over time, so it takes time to obtain the waveform data of the voltage signal under test. There is a drawback that it takes

An object of the present invention is to provide a high-speed voltage measuring device that can obtain waveform data of a signal under test in a short time.

"Means for Solving the Problem" In this invention, the optical pulse that has passed through the variable delay means is branched by an optical splitter, and a sub-delay means is provided on the branched optical path, and the optical pulse that has passed through the sub-delay means is split by an optical splitter. It is recombined with the original light pulse that was split earlier.

The recombined optical pulses include an optical pulse that has passed through only the variable delay means and an optical pulse that has passed through both the variable delay means and the sub-delay means. Therefore, the delay amount of the optical pulse that has passed through both the variable delay means and the sub-delay means is longer by the delay time of the sub-delay means than the delay amount of the optical pulse that has passed only the variable delay means.

By inputting optical pulses with different delay amounts into the electro-optic modulator, the IJillJI of the voltage signal to be measured is
Can be sampled once.

As a result, the amount of data that can be captured can be doubled, so the waveform data of the voltage signal to be measured can be
It can be captured in 72 hours.

Furthermore, by branching the optical pulse into a plurality of N pieces, which is more than 2, and providing a sub-delay means in each branch path, one part of the voltage signal to be measured is
N sampling pulses can be obtained within a period.

If an identification function is added to the plurality of optical pulses by an identification function adding means provided in each branch path, the data can be identified and imported on the data acquisition side.

Therefore, if N optical pulses are obtained within one cycle of the voltage signal to be measured, the data acquisition time can be reduced to 1/N.

"Embodiment" FIG. 1 shows an embodiment of the present invention, and the embodiment in FIG. 1 shows an embodiment corresponding to the first invention of this application. In the first invention of this application, an optical splitter 207A is provided on the downstream side of the variable delay means 202, and a sub-delay means 209 is provided on the sub-optical path 208B branched by the optical splitter 207A. In the illustrated example, a variable delay circuit having the same configuration as the variable delay means 202 is used as the sub-delay means 209, but the structure does not have to be such that the delay time can be varied.

In addition to the sub delay means 209, an identification function addition means 203B is provided in the sub optical path 208B branched by the optical splitter 207A. This identification function addition means 203B adds an identification function to the optical pulse that has passed through the sub-delay means 209, similar to the identification function addition means 203A provided in the main optical path 208A.

The identification function is added by converting the optical pulse train into a pulse modulated wave modulated by the modulation frequencies f1 and 11 using an acousto-optic modulator as described above.

The optical pulses to which identification functions have been added by the identification function adding means 203A and 203B are combined by an optical coupler 212 and sent to the electro-optic modulator 100.

The optical pulses fed into the electro-optic modulator 100 are shown in the second figure. As shown in FIG. 2, the optical pulse PM delayed by the variable delay means 202 and passing through the main optical path 208A is delayed by the delay time τ1 of the variable delay means 202 than the original optical pulse LP. On the other hand, the optical pulse branched to the sub optical path 208B becomes an optical pulse PMz delayed by the delay time τ8 of the sub delay means 209.

As a result, the optical pulse optically coupled by the optical coupler 212 is
As shown in the figure, two optical pulses PM and PM are obtained within one period T.

Optical pulse PM and PM are identification function adding means 203A,
At 203B, the signals are modulated at modulation frequencies r□ and f□. This modulated wave is shown in FIG. Function adding means 203A for identifying modulated signals MP and MPo.

203B, the identification function adding means 203
Modulated waves PM and PM are output from A and 203B.

Photodetector 204 provided on the output side of electro-optic modulator 100
The electrical signal converted by is sent to two discriminators 205A and 205B.
and each optical pulse P is input to the discriminator 205A and 205B.
DC voltage El + E2 corresponding to the value of the measured voltage ■ at the timing of passage of M and PM (Fig. 2 E, F
) is output.

These DC voltages E, ,E change in accordance with the waveform of the voltage to be measured (■) by scanning in a direction that sequentially increases the delay time τ of the variable delay means 202, and the waveform of the voltage to be measured (■) is displayed on the display. 206 can be displayed.

In this example, the discrimination outputs of the discriminators 205A and 205B are input to the microcomputer 207, and the microcomputer 207 processes the data and displays it on the display 206.

Further, the delay time τ1 of the variable delay means 202 is also controlled by the microcomputer 207 and scanned.

Although the delay time of the sub-delay means 209 is fixed during measurement,
The delay time τ depends on the rising speed of the measured voltage ■.
2 may be changed.

FIG. 4 shows an embodiment corresponding to the second invention of this application.

In this example, three optical splitters 207A, 207B, and 207C are provided after the variable delay means 202, and these three optical splitters 207A, 207B, and 207C
8A is branched into three sub optical paths 208A to 208D, and each sub optical path 208A to 208D includes a sub delay means 209A,
209B and 209C are inserted.

Identification function addition means 203B, 203C1203D are provided at the subsequent stage of each sub-delay means 209A, 209B, 209C, and these identification function addition means 203B, 203C, 203
At D, pulse modulation is performed at frequencies f, t, f s3, and fl, and the pulse-modulated optical pulses are sent to six optical couplers 21.
2A, 212B, 212C, 212D, 212E, 21
2F and enters the electro-optic modulator 100.

In this way, the three sub-delay means 203B, 203C120
By adding 3D, four pulses can be obtained within one period of the voltage signal to be measured (2), and the data acquisition time can be reduced to 1/4 compared to the conventional method.

FIG. 5 shows another embodiment of the discriminator 205. In this example, the discriminator 205 is constructed from a band pass filter BPF, an A/D converter AD, an averaging circuit AV, and a Fourier transformer FL.

When data is discriminated by the Fourier transformer FL in this way, if the embodiment of FIG. 4 is applied to the optical pulse sending side, the discrimination function addition means 2
Frequency spectra SP+, SPz, SP, , SP are obtained for each function added in 03A to 203D.

In other words, the modulation frequency f0, f, 3, fan, f, the delay time of the modulated optical pulse τ3, τ2, τ8, τ4
and these delay times τ1, τ2, τ1, τ4 are τ1
Assuming that τ is set to τ3<τ4, each frequency spectrum SP.

SP! , SP3, and SP4 each indicate a position corresponding to the waveform of the voltage to be measured (■). Therefore, variable delay means 2
By scanning the delay time of 02 on the time axis, waveform data of the voltage to be measured ■ can be obtained.

"Effects of the Invention" As explained above, according to the present invention, it is possible to make a plurality of optical pulses enter the electro-optic modulator 100 within one period of the voltage to be measured (2), thereby making it possible to ]
It is possible to sample multiple times within XJI.

Therefore, waveform data of the voltage to be measured (2) can be obtained in a short time.

[Brief explanation of the drawing]

Fig. 1 is a block diagram showing an embodiment of the first invention of this application, Figs. 2 and 3 are waveform diagrams for explaining its operation, and Fig. 4 shows an embodiment of the second invention of this application. FIG. 5 is a block diagram showing a modified example of the discriminator, FIG. 6 is a graph for explaining the operation of FIG. 5, and FIG. 7 shows the structure and structure of the electro-optic modulator used in the present invention. FIG. 8 is an exploded perspective view to explain the operation, FIG. 8 is a graph to explain the operation of the electro-optic modulator, FIG. 9 is a block diagram to explain the conventional high-speed waveform observation device, and FIGS. FIG. 11 is a similar waveform diagram. 100: Electro-optic modulator, 101: Crystal, 200:
Short pulse laser oscillator, 201, 207A, 207B,
207C: Optical splitter, 202: Variable delay means, 209A
, 209B, 209C: Sub delay means, 203, 203A
~203D: Discrimination function addition means, 205: Discriminator.

Claims (2)

[Claims] (1) A crystal placed on the optical axis, a polarizer provided on the light incidence side of the crystal, and an analyzer provided on the light output side of the crystal, perpendicular to the optical axis of the crystal. A voltage signal to be measured is applied between the electrodes of the electro-optic modulator, and a pulse is generated in synchronization with the period of the voltage signal to be measured. A laser beam of a shape is inputted, and its output amount is measured, and the timing of the light applied to the electro-optic modulator is sequentially delayed by a variable delay means, so that the timing of the incident light relative to the period of the voltage signal to be measured is sequentially adjusted on the time axis. In a high-speed voltage signal measuring device that captures the waveform of a voltage signal to be measured from changes in the light intensity of each emitted light by scanning in the direction, an optical splitter is provided on the optical path of the light that has passed through the variable delay means, and this A sub-delay means is provided on the optical path branched by the optical splitter, the light delayed by the sub-delay means is recombined with the light delayed by the variable delay means by the optical coupler, and the recombined light is A high-speed voltage measuring device, wherein a plurality of optical pulses are incident on the electro-optic modulator within a cycle of a voltage signal to be measured. (2) A plurality of optical splitters are provided on the optical path of the light that has passed through the variable delay means, sub-delay means are provided for each of the optical paths branched by the plurality of optical splitters, and the light delayed by each sub-delay means is A high-speed voltage measurement device in which two or more optical pulses are recombined and input into an electro-optic modulator, and two or more optical pulses are input within the period of a voltage signal to be measured.