JPH03131772A - Voltage detecting device - Google Patents

Abstract

PURPOSE:To take an accurate measurement without the distortion of an electric signal to be measured due to an electric chopper by controlling the turn-on timing of a pulse light source by using a pulse-modulated sweep signal. CONSTITUTION:A pulse light source driving device 42 turns on a laser diode LD 32 at a frequency synchronized with the repetitive frequency of the electric signal to be measured. A waveform generated by imposing pulse modulation on a saw-tooth wave is used for the sweep signal of this turn-on timing. When the turn-on timing of the LD 32 is controlled with this sweep signal, laser pulse light emitted by the LD 32 at this time is turned on in the former half of a turn-on period T2 and off in the latter half and a sampling point is shifted from a reference point corresponding to the level of the electric signal to be measured, to obtain a modulated output. Consequently, the distortion of the electric signal to be measured which is caused by the electric chopper is eliminated and the measurement is accurately performed.

Description

[Detailed description of the invention]

INDUSTRIAL APPLICATION FIELD 1 This invention relates to a voltage detection device using an electro-optic material whose refractive index changes in response to changes in the voltage of an electrical signal to be measured. [Prior Art] Conventionally, electro-optic materials having an electro-optic effect, such as Li
2. Description of the Related Art A voltage detection device is known that uses a TaO3 crystal to non-contactly measure the voltage at a predetermined portion of an object to be measured, such as an integrated circuit. For example, as shown in FIG. 10, such a voltage detection device transmits an electrical signal from an electrical signal generating device to be measured 5 to an optical modulator 1 that includes an electro-optic material 2, a polarizer 3, and an analyzer 4. is applied to the electro-optical material 2 through the electric chopper 6, and in this state, a laser pulse light from the laser diode 7 is irradiated, and the light that has passed through the optical modulator 1 is detected by the photodetector 8. This is amplified by a synchronous amplifier 9, and an electric signal waveform is formed by a signal processing device 10. Here, the electrical signal from the electrical signal generator to be measured 5 is
It is generated based on a trigger signal from the trigger signal generator 11. Further, the trigger signal generator g111 outputs a trigger signal to the pulsed light source driving device 12, and the pulsed light source driving device 12 not only turns on the laser diode 7 in pulses, but also controls the lighting timing. ing. Further, the electric chopper 6 outputs a reference signal to the synchronous amplifier 9, and the electric light timing control device 12 outputs a sweep signal to the signal processing device 10. Therefore, the light emitted from the laser diode 7 is transmitted to the polarizer 3.
As a result, it becomes a component of only a certain plane of polarization, which is further incident on the electro-optic material 2, and the plane of polarization is modulated by the electrical signal to be measured. The light emitted from the electro-optic material 2 whose polarization plane has been modulated passes through the analyzer 4 to extract only a certain polarization plane component, and at this time, the modulation of the polarization plane is converted into modulation of light intensity. The light emitted from the analyzer 4 is charged and converted by the photodetector 8, and is then charged and converted by the photodetector 8, and is then charged and converted by the synchronous amplifier 9, which is a lock-in amplifier, for example.
The signal is amplified with high sensitivity and low noise. In this case, the signal to be detected needs to be modulated in accordance with the amplification frequency of the synchronous amplifier 9. For this reason, conventionally, as described above, an electric signal is connected between the electrical signal generator to be measured 5 and the optical modulator 1. A chopper 6 or the like is interposed to turn on/off the electrical signal to be measured. When the electric chopper 6 is on, a voltage is applied to the electro-optic material 2, so the laser pulse light is modulated there, and when it is off, no voltage is applied, so the laser pulse light is not modulated. Here, since the laser diode 7 operates in short pulses, in the case of the above device, the waveform of the electrical signal to be measured shown in FIG. Then, sampling measurement is performed using short pulse light at, for example, point a, point b, and point 0. Therefore, by sequentially moving the sampling points, the entire waveform of the electrical signal to be measured can be obtained. For this reason, conventionally, the pulsed light source driving device 12 sequentially moves the sampling point using the sweep signal shown in FIG. 10, and the signal processing device 10 can form the entire waveform of the electrical signal to be measured from the output signal of the synchronous amplifier 9 and the sweep signal. 100M
When operating at Hz, the entire waveform can be grasped by moving the lighting timing at intervals of 10 nsec using a sweep signal. The movement at this time may be at a low speed, and for example, as shown in FIG. 12, the lighting timing may be delayed by 10 nsec over one second. In Fig. 13 (A) to (D), three sampling points a,
The electrical signals to be measured, light incident on the polarizer, light emitted from the analyzer, and output from the photodetector in b and c are shown in comparison. The intensity of the emitted light is increased as shown in FIG. 13(C) only when the electric chopper 6 is on, corresponding to the voltage of each sampling light. Therefore, as shown in FIG. 13 (D>), the output from the photodetector 8 changes accordingly, and the output of the synchronous amplifier 9 becomes as shown in FIG. 14.

[Problems to be Solved by the Invention] In the conventional voltage detection device, the electric chopper 6 is operated in accordance with the synchronization signal to modulate the output of the photodetector 8. An element called an electric chopper 6 is inserted between the signal generator 5 and the optical modulator 1, resulting in a problem that the configuration becomes complicated. Further, since the electrical signal to be measured is applied to the electro-optical material 2 via the electric chopper 6, there is a problem that the waveform of the electrical signal to be measured is distorted and the measurement is not accurate. In particular, since it is difficult to obtain an electric chopper with good characteristics over a wide band, problems caused by waveform distortion become significant. This invention has been made in view of the above-mentioned conventional problems, and it is an object of the present invention to perform high-sensitivity and low-noise amplification without using an electric chopper or the like, and therefore without giving any distortion or the like to the electrical signal to be measured. It is an object of the present invention to provide a voltage detection device that can perform the following functions and has a simple configuration. (Means for Solving the Problems) The present invention provides a voltage detection device using an electro-optic material whose refractive index changes in response to changes in the voltage of an electrical signal to be measured. A light modulator comprising an electro-optic material, a polarizer, and an analyzer, a means for introducing light into the light modulator, a means for emitting light from the light modulator, and a means for receiving pulsed light emitted from the light emitting means. A photodetector that converts into an electrical signal, a synchronous amplifier that amplifies the output signal of the photodetector, and pulse lighting of the pulsed light source in synchronization with the electrical signal to be measured, and the timing of the lighting is controlled by: The above object is achieved by providing a pulsed light source driving device that performs pulse modulation in synchronization with the synchronous amplifier.Furthermore, the pulsed light source driving device modulates the pulsed light source by repeating the electrical signal to be measured. The same integer multiple as the frequency, or
The light is turned on at a repetition frequency of 1/integer, and the light is turned on at a reference first timing and at a second timing shifted from the first timing, and at the same time, At the amplification frequency of the amplifier,
The above object is achieved by alternately switching the first and second lighting timings. Further, the above object is achieved by sequentially shifting the second lighting timing of the pulse light source driving device with respect to the reference first lighting timing. Further, the above object is achieved by configuring the pulse light source driving device so that the interval between the first and second lighting timings remains constant and the timings of both are sequentially changed. Further, the above object is achieved by configuring the pulse light source driving device so that the amount of change in timing of one or both of the first timing and the second timing is constant per unit time. Furthermore, the pulsed light source driving device is configured to generate a differential waveform of the electrical signal to be measured using the output signal of the synchronous amplifier so that the interval between the first and second timings is about the pulse width of the pulse signal. The above objective is achieved by obtaining the following. Further, the above object is achieved by providing the signal processing device with an addition circuit or an integration circuit that sequentially adds or integrates the outputs of the synchronous amplifiers. Further, the above object is achieved by using a laser diode as the pulse light source. Furthermore, the above object is achieved by providing the pulse light source driving device with a timing ilJ control device that can change the timing of turning on the pulse light source in proportion to the input voltage. [Operation] In this invention, the pulsed light source driving device also has the function of a conventional electric chopper, and by controlling the lighting timing of the pulsed light source using a pulse-modulated sweep signal, the electrical signal to be measured is This produces the same effect as when a chopper is applied to the voltage, and thereby a voltage waveform similar to the conventional one can be obtained without using chopper means such as an electric chopper. Therefore, since there is no distortion of the electrical signal waveform to be measured due to the electric chopper, more accurate measurement can be performed.

Example 1 An example of the present invention will be described below with reference to the drawings. FIG. 1 shows a first embodiment of a voltage detection device according to the present invention. A voltage detection device 20 according to this embodiment includes a polarizer 22, an electro-optic material 24, and an analyzer 26, and includes an electro-optic material 24 and an analyzer 26.
4, an optical modulator 30 to which an electrical signal from the electrical signal generator to be measured 28 is applied, and a laser diode 3 which is a pulsed light source that irradiates the optical modulator 30 with laser pulsed light.
2, a photodetector 34 that receives the pulsed light emitted from the optical modulator 30 and converts it into an electrical signal, a synchronous amplifier 36 that amplifies the output signal of the photodetector 34, and the electrical signal generator to be measured 28. a trigger signal generator 38 that outputs a trigger signal to the target; and based on the trigger signal from the trigger signal generator 38, the laser diode 32 is pulse-lit in synchronization with the electrical signal to be measured;
It is provided with a pulsed light source driving device 42 that pulse-modulates the lighting timing in synchronization with the synchronous amplifier 36. The pulse light source driving device 42 includes a laser diode 32
In order to synchronize the lighting timing with the synchronous amplifier 36, a synchronizing signal is output to the synchronous amplifier 36. Further, the output signal of the synchronous amplifier 36 is transmitted to the signal processing device 4.
The signal processing device 44 processes the input signal based on the sweep signal from the pulsed light source driving device 42, and can reproduce the waveform of the electrical signal to be measured. The pulse light source driving device 42 is configured to turn on the laser diode 32, which is the pulse light source, at a repetition frequency that is the same as, an integral multiple, or an integral fraction of the repetition frequency of the electrical signal to be measured. For example, when the pulse light source driving device 42 operates at 100 MHz, the period of the trigger signal is t+ = 1.
0 nsec, and at that time, the pulse light source driving device 42
As shown in Fig. 3, the sweep signal for the lighting timing is pulse-modulated with a period of t2 = 0.1 m5ec so that the deviation in the lighting timing changes from 0 to 10 nsec in 1 second, and the entire waveform is Let it be measured. That is, in the conventional voltage detection device shown in FIG. 10, the sweep signal in the pulsed light source driving device 42 was a sawtooth signal, as shown in FIG.
In the case of the present invention, this sawtooth wave is pulse-modulated. In this way, when the lighting timing of the laser diode 32 is controlled by the pulse-modulated sawtooth h11 signal, the laser pulse light emitted from the laser diode 32 at that time is as shown in FIG. 2(B) and It will look like (C). Of the lighting period t2 of the laser pulse light, the lighting timing is constant at the first timing in the first half, whereas at the second timing in the latter half, the lighting timing is equal to the height of the pulse waveform in FIG. The sampling point deviates from the reference point. At sampling point a, as shown in Figure 2 (A), the output of the electrical signal to be measured is zero, so as shown in Figure 4 (C).
As shown in FIG. 2, there is no change in the intensity of the light emitted from the analyzer 26. Further, at the first timing of the period t2 of the laser pulse light, the sampling point is a, and the laser pulse light is not modulated. However, at the second timing in the second half of the period t2, depending on the position of each sampling point, for example, the voltage signal to be measured of the light C, as shown in b and C of FIG. 4(C). It becomes like this. That is, as shown in FIG. 4A, the electrical signal from the electrical signal generating device 28 to be measured applied to the electro-optic material 24 in the optical modulator 30 is not chopped, but the electrical signal in the pulsed light source driving device 42 is chopped. Since the sweep signal is turned off at the first timing in the first half of the period t2 and turned on at the second timing in the second half, the analyzer output light is as shown in FIG. Thus, in the second half of the period t2, an output modulated in accordance with the intensity of the electrical signal to be measured is obtained. Therefore, the output of the photodetector 34 which receives the light emitted from the analyzer 26 and converts it photoelectrically is as shown in FIG. The processing device 44 can obtain an electrical signal waveform as shown in FIG. Here, the electrical signal from the voltage signal generator to be measured ff128 is not chopped, but is subjected to the same effect as chopping by the pulse modulation of the sweep signal, so the electrical signal to be measured is not distorted and is accurate. measurements can be made. It is assumed that the timing of turning on the pulsed light by the pulsed light source driving device 42 is such that the amount of change in the second timing is constant per unit time. In the above embodiment, the electrical signal generator to be measured 28 is synchronized with the trigger signal from the trigger signal generator 38, but as in the second embodiment shown in FIG. The device 38 may be configured to be synchronized with the electrical signal generating device 28 under test. Further, the pulsed light source driving device 42 may be composed of a synchronizing pulse generating device 46, a reference signal generating device M4B, and a timing modulation circuit 50, as in the third embodiment shown in FIG. The timing modulation circuit 50 includes the synchronization pulse generator 4
The timing of the pulse signal from 6 can be changed by changing the input voltage based on the reference signal from the reference signal generator 48. Here, the reference signal generator 48 outputs a reference signal to the synchronous amplifier 36. The specific configuration of the reference signal generator 48 and the timing modulation circuit 50 is, for example, as shown in FIG. Among the four fixed contacts 53A to 53D, 53A and 53G
It is configured to include a short cable 54 connected to the fixed contacts 53B and 53D, and a long cable (delay 1t) 56 connected to the fixed contacts 53B and 53D. In this embodiment, the rotating contact 52A is the fixed contact 53.
When it is in contact with A or 53G, there is no timing modulation, that is, it forms the first timing in the first embodiment, and when it is in contact with fixed contact 53B or 53D, it is a delay line. The second timing is formed by the action of the long cable 54. In the above embodiment, the pulse light source driving device 42 sets the first timing at which the sweep signal is not output and the second timing at which the sweep signal is output by arbitrarily shifting the time relative to this. The present invention is not limited to this. For example, if the entire waveform of the electrical signal to be measured is not required, the second timing may not change with respect to the first timing. Alternatively, the difference between the output values of the sweep signals at the first timing and at the second timing may be constant. That is, as shown in FIG. 9, the first timing and the second timing in the pulse-modulated sweep signal may be sequentially changed while keeping the timing interval constant. The potential difference between the sampling points at the first and second timings can be sequentially measured. In this case, if the difference between the first and second timings is further shortened to about the width of an optical pulse, the differential waveform of the electrical signal to be measured can be obtained from the output signal of the synchronous amplifier 36, so an integrating circuit is added to the signal processing device 44. By doing so, the waveform of the electrical signal to be measured can be easily obtained. Alternatively, the timing may be changed stepwise as shown in FIG. 15 to amplify the Nobutori component at a frequency of 1/lo in a narrow band. [Effects of the Invention] Since the present invention is configured as described above, it is possible to obtain substantially the same effect as chopping by processing the sweep signal of the pulsed light source without chopping the electrical signal to be measured using an electric chopper or the like. Therefore, it has the excellent effect of preventing waveform distortion due to chopping of the electrical signal to be measured and making it possible to perform accurate measurements.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing a first embodiment of the voltage detection device according to the present invention, FIG. 2 is a diagram showing the waveform of the electrical signal to be measured and the state of the laser pulse light in the same embodiment device, and FIG. 3 Figure 4 is a line diagram showing the state of the sweep signal applied to the laser pulse emission source, and Figure 4 is a line diagram showing a comparison of the electrical signal to be measured, polarizer incident light, analyzer output light, and photodetector output at each sampling point. 5 is a diagram showing the waveform of the electrical signal to be measured obtained by the signal processing device, FIG. 6 is a block diagram showing a second embodiment of the present invention, and FIG. 7 is a third embodiment of the present invention. 8 is a circuit diagram showing a specific example of the timing modulation circuit and reference signal generating device in the third embodiment, and FIG. 9 is a waveform of the sweep signal output from the pulsed light source driving device. FIG. 10 is a block diagram showing a conventional voltage detection device, FIG. 11 is a diagram showing the state of the electrical signal to be measured and laser pulse light in the conventional voltage detection device, and FIG. A line diagram showing a sweep signal in a conventional pulsed light source driving device, and FIG. 13 shows the electrical signal to be measured, polarizer incident light, analyzer output light, and photodetector output in the same conventional voltage detection device at each sampling light. 14 is a diagram showing the waveform of the electrical signal to be measured obtained by the signal processing device in the conventional voltage detection device,
FIG. 15 is a diagram showing a modified example of timing. 20... Voltage detection device, 22... Polarizer, 24... Electro-optical material, 26... Analyzer, 28... Electrical signal generator to be measured, 30... Optical modulator, 32 ... Laser diode, 34... Photodetector, 36... Synchronous amplifier, 38... Trigger signal generator, 42... Pulse light source driver, 44... Signal processing device, 46... - Synchronous pulse generator, 48... Reference signal generator, 50... Timing modulation circuit.

Claims (9)

[Claims] (1) A voltage detection device using an electro-optic material whose refractive index changes in response to changes in the voltage of an electrical signal to be measured, including a pulsed light source that generates pulsed light, the electro-optic material, a polarizer, and an analyzer. a light modulator consisting of a light modulator, a light input means to the light modulator, a light output means from the light modulator, and a photodetector that receives pulsed light emitted from the light output means and converts it into an electrical signal. , a periodic amplifier that amplifies the output signal of the photodetector, and a pulse light source that turns on the pulse light source in synchronization with the electrical signal to be measured, and pulse-modulates the lighting timing in a period with the synchronous amplifier. A voltage detection device comprising: a pulsed light source drive device for controlling the pulsed light source; (2) In claim 1, the pulsed light source driving device includes:
The pulsed light source is turned on at a repetition frequency that is the same as, an integral multiple, or an integer fraction of the repetition frequency of the electrical signal to be measured, and the lighting timing is set to a reference first timing and this first timing. A voltage detection device characterized in that the first and second lighting timings are alternately switched at a second timing that is shifted from the timing of the periodic amplifier, and at the amplification frequency of the periodic amplifier. (3) In claim 2, the pulsed light source driving device:
A voltage detection device characterized in that the second lighting timing is sequentially shifted with respect to the reference first lighting timing. (4) In claim 2, the pulsed light source driving device:
A voltage detection device characterized in that the first and second lighting timings are configured such that the timings thereof are sequentially changed while the interval between the first and second lighting timings is constant. (5) In claim 2, 3, or 4, the pulsed light source driving device is configured such that a timing change amount of one or both of the first timing and the second timing is constant per unit time. Characteristic voltage detection device. (6) In claim 4, the pulsed light source driving device comprises:
The differential waveform of the electrical signal to be measured is obtained using the output signal of the periodic amplifier by making the interval between the first and second timings approximately equal to the pulse width of the pulse signal. voltage detection device. (7) The voltage detection device according to claim 6, wherein the signal processing device includes an addition circuit or an integration circuit that sequentially adds or integrates the outputs of the synchronous amplifier. (8) The voltage detection device according to any one of claims 1 to 7, wherein the pulsed light source is a laser diode. (9) In any one of claims 1 to 8, the pulse light source driving device includes a timing control device that can change the timing of turning on the pulse light source in proportion to the input voltage. Featured voltage detection device.