JP2553715B2 - Voltage detector - Google Patents

Description

Detailed Description of the Invention [Industrial applications]

The present invention relates to a voltage detection device using an electro-optical material whose refractive index changes in response to a voltage change of an electric signal under measurement.

[Prior art]

Conventionally, an electro-optical material having an electro-optical effect, such as Li
There is known a voltage detection device that uses TaO ₃ crystal to measure the voltage of a predetermined portion of an object to be measured such as an integrated circuit in a non-contact manner. Such a voltage detecting device, for example, as shown in FIG. 10, applies an electric signal from the measured electric signal generating device 5 to an optical modulator 1 including an electro-optical material 2, a polarizer 3 and an analyzer 4. It is applied to the electro-optic material 2 through the electric chopper 6, and in this state, the laser pulse light from the laser diode 7 is irradiated, and the light passing through the optical modulator 1 is detected by the photodetector 8 and 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 measured electrical signal generator 5 is generated based on the trigger signal from the trigger signal generator 11. Further, the trigger signal generator 11 also outputs a trigger signal to the pulse light source driving device 12, so that the pulse light source driving device 12 controls the laser diode 7 to pulse-light and also controls the lighting timing. ing. Also, from the electric chopper 6, the synchronous amplifier 9
A reference signal is output to the signal processing device 10 and a sweep signal is output from the lighting timing control device 12 to the signal processing device 10. Therefore, the light emitted from the laser diode 7 is made into a component of only a certain plane of polarization by the polarizer 3, further enters the electro-optical material 2, and the plane of polarization is modulated by the electrical signal to be measured. Become. Light emitted from the electro-optic material 2 whose plane of polarization is modulated passes through the analyzer 4,
Only a certain polarization plane component is extracted, and at this time, the modulation of the polarization plane is converted into the modulation of the light intensity. The light emitted from the analyzer 4 is photoelectrically converted by the photodetector 8 and amplified with high sensitivity and low noise by the synchronous amplifier 9 which is, for example, a lock-in amplifier. In this case, the detected signal needs to be modulated in accordance with the amplification frequency of the synchronous amplifier 9, and therefore, conventionally,
As described above, the electric signal to be measured is turned on / off by interposing the electric chopper 6 or the like between the electric signal generator 5 to be measured and the optical modulator 1. When the electric chopper 6 is on, a voltage is applied to the electro-optic material 2 so that the laser pulse light is modulated here, and when it is off, no voltage is applied and therefore the laser pulse light is not modulated. Here, since the laser diode 7 is operating for a short pulse, in the case of the above device, the measured electric signal waveform shown in FIG. 11 (A) is shown in FIG. 11 (B), (C). As described above, the short pulse light is sampled and measured at points a, b, and c, for example. Therefore, if the sampling points are sequentially moved, the entire measured electric signal waveform can be obtained. Therefore, conventionally, in the pulse light source driving device 12, the sampling points are sequentially moved by using the sweep signal shown in FIG. On the other hand, the sweep signal synchronized with the movement of the sampling point is input to the signal processing device 10, and the signal processing device 10
From the output signal of the synchronous amplifier 9 and the sweep signal, the entire waveform of the electrical signal under measurement can be formed. Therefore, for example, when the trigger signal generator 11 is operating at 100 MHz, if the lighting timing is moved at intervals of 10 nsec by the sweep signal, the entire waveform can be grasped. The movement at this time may be slow, for example, the 12th
As shown in the figure, the lighting timing is 10
You may make it delay nsec. In FIGS. 13A to 13D, three sampling points a,
The measured electric signals in b and c, the incident light to the polarizer, the emitted light from the analyzer, and the output from the photodetector are shown in comparison with each other. 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 at each sampling point. Therefore, as shown in FIG. 13 (D), the output from the photodetector 8 also changes accordingly, and the output of the synchronous amplifier 9 becomes as shown in FIG.

In the above-mentioned conventional voltage detection device, the electric chopper 6 is operated in accordance with the synchronizing signal to modulate the output of the photodetector 8. However, in this method, the measured electric An element called an electric chopper 6 is inserted between the signal generator 5 and the optical modulator 1, which causes a problem that the configuration becomes complicated. Further, since the electric 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 electric signal to be measured is distorted and the measurement is not accurate. In particular, since it is difficult to obtain an electric chopper having excellent characteristics over a wide band, the problem caused by waveform distortion becomes remarkable. The present invention has been made in view of the above conventional problems, and it is possible to perform high-sensitivity and low-noise amplification without using an electric chopper or the like, and thus without giving any distortion or the like to an electric signal to be measured. It is an object of the present invention to provide a voltage detection device that is capable of operating and has a simple configuration.

[Means for Solving the Problems]

The present invention provides a pulse light source for generating pulsed light in a voltage detection device for contact or non-contact measurement using an electro-optic material whose refractive index changes according to a voltage change of an electric signal to be measured, and the electro-optic material. An optical modulator consisting of a material, a polarizer and an analyzer, a light incident means to the optical modulator, a light emitting means from the optical modulator, and a pulsed light emitted from the light emitting means to receive an electric signal. A photodetector for converting into a light, a synchronous amplifier for amplifying an output signal of the photodetector, and the pulse light source for pulse lighting in synchronization with the electrical signal under measurement, and the lighting timing of the pulse light. The above object is achieved by providing a pulsed light source driving device that performs modulation in synchronization with the amplifier. In addition, the pulse light source driving device,
The lighting frequency is the same as the repetition frequency of the electric signal to be measured, an integral multiple, or a repetition frequency of an integer fraction, and the lighting timing is based on the reference first timing and the first timing. The first and second lighting timings are alternately switched at the second timing with the timing shifted, and at the synchronizing frequency of the synchronous amplifier. In the pulse light source driving device, the second lighting timing is set to a reference first lighting timing.
The object is achieved by sequentially shifting. Further, the pulse light source driving device is configured so that the timings of the first and second lighting timings are sequentially changed with respect to the measured electrical signal while the interval between the first and second lighting timings is constant. To achieve. Further, the above-mentioned object is achieved by configuring the pulse light source driving device such that one or both of the first timing and the second timing have a constant timing change amount per unit time. Furthermore, the pulsed light source driving device includes the first and second
The above object is achieved by obtaining the differential waveform of the electrical signal to be measured using the output signal of the synchronous amplifier such that the timing interval is about the pulse width of the pulse signal. Further, the above-described object is achieved by providing the signal processing device with an adding circuit or an integrating circuit for sequentially adding or integrating the outputs of the synchronous amplifier. Further, the above object is achieved by using a laser diode as the pulse light source. Further, the above-described object is achieved by providing the pulse light source driving device with a timing control device capable of changing the timing of lighting the pulse light source in proportion to the input voltage.

[Action]

In the present invention, the pulse light source driving device also has the function of the conventional electric chopper, and by using the pulse-modulated sweep signal to control the lighting timing of the pulse light source, the chopper is added to the measured electric signal. The same operation as that applied is performed, whereby a voltage waveform similar to the conventional one can be obtained without using a chopper means such as an electric chopper. Therefore, since there is no distortion of the electric signal waveform to be measured by the electric chopper, more accurate measurement can be performed.

【Example】

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows a first embodiment of the voltage detecting device according to the present invention. The voltage detection device 20 according to this embodiment includes a polarizer 22, an electro-optical material 24, and an analyzer 26, and the electro-optical material 24 is an optical modulator to which an electric signal from a measured electric signal generator 28 is applied. 30, a laser diode 32 which is a pulse light source for irradiating the optical modulator 30 with laser pulse light, and an optical modulator 30
A photodetector 34 that receives the emitted pulsed light from the device and converts it into an electric signal, a synchronous amplifier 36 that amplifies the output signal of the photodetector 34, and a trigger signal to the measured electric signal generator 28. Based on the trigger signal generator 38 for outputting and the trigger signal from the trigger signal generator 38, the laser diode 32 is pulse-lighted in synchronization with the electrical signal under measurement, and its lighting timing is Pulse light source driving device for pulse modulation in synchronization with the synchronous amplifier 36
It is equipped with 42 and. The pulsed light source driving device 42 synchronizes the lighting timing of the laser diode 32 with the synchronous amplifier 36,
A synchronizing signal is output to the synchronizing amplifier 36. Further, the output signal of the synchronous amplifier 36 is a signal processing device 44.
The signal processing device 44 processes the output signal of the synchronous amplifier 36 based on the sweep signal from the pulse light source driving device 42 and reproduces the waveform of the electrical signal under measurement. The pulsed light source driving device 42 is adapted to turn on the laser diode 32, which is the pulsed light source, at a repetition frequency which is the same as the repetition frequency of the electrical signal under measurement, an integral multiple, or an integral fraction. The pulse light source driving device 42, for example, when operating at 100MHz, the cycle of the trigger signal t ₁ = 10nsec,
At that time, the sweep signal at the lighting timing in the pulse light source driving device 42 is t ₂ = 0.1 mse as shown in FIG.
All waveforms are measured by pulse-modulating in c cycle so that the deviation of lighting timing changes from 0 to 10 nsec in 1 second. That is, in the conventional voltage detection device shown in FIG. 10, as shown in FIG.
The sweep signal at 42 was a sawtooth signal, but in the case of the present invention, this sawtooth wave is pulse-modulated. As described above, when the lighting timing of the laser diode 32 is controlled by the pulse-modulated sawtooth-shaped sweep signal, the laser pulse light emitted from the laser diode 32 at that time is shown in FIG. It becomes like (C). The lighting timing is constant at the first timing in the first half of the lighting cycle t ₂ of the laser pulse light, while the height of the pulse waveform in FIG. 3 is at the second timing in the latter half. The sampling point deviates from the reference point by an amount. At the sampling point a, as shown in FIG. 2 (A), the output of the electric signal to be measured is zero, so as shown in FIG. 4 (C), the intensity of the light emitted from the analyzer 26 is increased. There is no change in. Further, at the first timing of the cycle t ₂ of the laser pulse light, the sampling point becomes a and the laser pulse light is not modulated. However, at the second timing in the latter half of the cycle t ₂ , depending on the position of each sampling point, for example, by the measured voltage signal at the points b and c, it is shown in b and c of FIG. 4 (C). Will be That is, as shown in FIG. 4 (A), the electric signal from the measured electric signal generator 28 applied to the electro-optic material 24 in the optical modulator 30 is not chopped, but the sweep in the pulse light source driver 42 is performed. The signal is the first half of the first half of period t ₂ .
Is turned off at the second timing and turned on at the second timing in the latter half of the second half, so that the light emitted from the analyzer becomes
As shown in b and c of FIG. (C), in the latter half of the cycle t ₂ ,
It will be obtained as an output modulated according to the strength of the electrical signal under measurement. Therefore, the output of the photodetector 34 that receives the emitted light from the analyzer 26 and photoelectrically converts it is as shown in FIG. 4 (D), which is amplified by the synchronous amplifier 36 to obtain a signal. The processing unit 44 can obtain an electric signal waveform as shown in FIG. Here, the electric signal itself from the measured electric signal generator 28 is not chopped, and the same effect as chopping is obtained by pulse modulation of the sweep signal, so that the measured electric signal is not distorted and is accurate. Various measurements can be performed. Regarding the pulsed light lighting timing by the pulsed light source driving device 42, the change amount of the second timing is constant per unit time. In the above embodiment, the electrical signal generator 28 to be measured is adapted to be synchronized with the trigger signal from the trigger signal generator 38. However, as in the second embodiment shown in FIG. The device 38 may be arranged to synchronize with the electrical signal generator 28 under test. Further, the pulse light source driving device 42 may be composed of a synchronizing pulse generating device 46, a reference signal generating device 48 and a timing modulation circuit 50 as in the third embodiment shown in FIG. The timing modulation circuit 50 includes a synchronization pulse generator 46.
With respect to the pulse signal from, the timing can be changed by 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. Specific configurations of the reference signal generator 48 and the timing modulation circuit 50 are, for example, as shown in FIG. 8, a high-speed rotary type rotary switch 52 whose rotation speed can be adjusted by an input voltage and its rotary contact 52A. Of the four fixed contacts 53A to 53D, a short cable 54 connected to 53A and 53C and a long cable (delay line) 56 connected to the fixed contacts 53B and 53D are included. In this embodiment, when the rotary contact 52A is in contact with the fixed contact 53A or 53C, there is no timing modulation, that is, the first timing in the first embodiment is formed, and the fixed contact is not generated. When in contact with the child 53B or 53D, the action of the long cable 54 that is a delay line
Is to form the timing. In the above embodiment, the pulsed light source driving device 42 takes 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. The present invention is not limited to this, and for example, when the entire waveform of the electric signal under measurement is not required, the second timing may not be changed with respect to the first timing. Further, the difference in the output value of the sweep signal between the first timing and the second timing may be constant. That is, as shown in FIG. 9, in the pulse-modulated sweep signal, the first timing and the second timing may be sequentially changed together with the timing interval kept constant. In this case, The potential difference between the sampling points at the first and second timings can be sequentially measured. In this case, when the first and second timing differences are further shortened to about the optical pulse width, the differential waveform of the electrical signal under measurement can be obtained from the output signal of the synchronous amplifier 36, so the signal processing device
By adding an integrating circuit to 44, the electric signal waveform to be measured can be easily obtained. Further, as shown in FIG. 15, the timing may be changed stepwise to narrow-band amplify the signal component having a frequency of 1 / t ₀ .

【The invention's effect】

Since the present invention is configured as described above, it is possible to obtain substantially the same effect as the chopping by processing the sweep signal of the pulse light source without chopping the electric signal to be measured with an electric chopper or the like. It has an excellent effect that the waveform distortion due to the chopping of the measurement electric signal can be prevented and the accurate measurement can be performed.

[Brief description of drawings]

FIG. 1 is a block diagram showing a first embodiment of a voltage detecting device according to the present invention, and FIG. 2 is a diagram showing an electric signal waveform to be measured and a state of laser pulse light in the device of the same embodiment, and FIG. Is a diagram showing the state of the sweep signal applied to the laser pulse emission source, and FIG. 4 is a diagram showing the electrical signals to be measured, the incident light of the polarizer, the emitted light of the analyzer, and the photodetector output at each sampling point. FIG. 5 is a diagram showing a measured electric signal waveform obtained by a 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. FIG. 8 is a block diagram showing a main part of FIG. 8, FIG. 8 is a circuit diagram showing a concrete example of a timing modulation circuit and a reference signal generator in the third embodiment, and FIG. 9 is a waveform of a sweep signal output from a pulse light source driving device. Fig. 10 is a block diagram showing a conventional voltage detection device. FIG. 11, FIG. 11 is a diagram showing a state of an electric signal to be measured and laser pulse light in the conventional voltage detection device, FIG. 12 is a diagram showing a sweep signal in the conventional pulse light source driving device, FIG. FIG. 13 is a diagram showing the measured electric signal, the incident light of the polarizer, the emitted light of the analyzer, and the output of the photodetector at each sampling point in the conventional voltage detection device,
FIG. 15 is a diagram showing a measured electrical signal waveform obtained by a signal processing device in the conventional voltage detection device, and FIG. 15 is a diagram showing a modification of timing. 20 ... Voltage detection device, 22 ... Polarizer, 24 ... Electro-optical material, 26 ... Analyzer, 28 ... Electrical signal generator under test, 30
...... Light modulator, 32 …… Laser diode, 34 …… Photo detector, 36 …… Synchronous amplifier, 38 …… Trigger signal generator, 42
...... Pulse light source driving device, 44 …… Signal processing device, 46 ……
Synchronous pulse generator, 48 ... Reference signal generator, 50 ...
Timing modulation circuit.

Claims (9)

(57) [Claims] 1. A voltage detection device for contact or non-contact measurement using an electro-optic material whose refractive index changes in response to a voltage change of an electric signal to be measured, and a pulsed light source for generating pulsed light; An optical modulator consisting of an optical material, a polarizer and an analyzer, a light incident means to the optical modulator, a light emitting means from this optical modulator, and a pulsed light emitted from the light emitting means. A photodetector for converting into an electric signal, a synchronous amplifier for amplifying an output signal of the photodetector, the pulsed light source for causing a pulse to be lit in synchronization with the electrical signal to be measured, and its lighting timing, And a pulse light source driving device that modulates in synchronization with the synchronous amplifier. 2. The pulse light source driving device according to claim 1, wherein the pulse light source is turned on at a repetition frequency that is the same as the repetition frequency of the electrical signal under test, an integral multiple, or an integer fraction. The lighting timing is set to a reference first timing and a second timing obtained by shifting the timing with respect to the first timing, and at the synchronization frequency of the synchronous amplifier, the first and second points. A voltage detection device characterized in that lighting timings are alternately switched. 3. The pulse light source driving device according to claim 2, wherein the second lighting timing is sequentially shifted with respect to a first lighting timing serving as a reference. And voltage detector. 4. The pulse light source driving device according to claim 2, wherein the timings of the first and second lighting timings are sequentially changed with respect to the electrical signal to be measured while the interval between the first and second lighting timings is constant. A voltage detection device having the above-mentioned configuration. 5. The pulse light source drive device according to claim 2, 3 or 4, wherein the timing change amount of one or both of the first timing and the second timing is constant per unit time. A voltage detection device characterized by the above. 6. The output signal of the synchronous amplifier according to claim 4, wherein the pulse light source driving device sets the interval between the first and second timings to be about the pulse width of the pulse signal. A voltage detecting device characterized in that a differential waveform of an electric signal to be measured is obtained by using the voltage detecting device. 7. The signal processing device according to claim 6,
A voltage detecting device comprising an adding circuit or an integrating circuit for sequentially adding or integrating the outputs of the synchronous amplifier. 8. The voltage detecting device according to claim 1, wherein the pulse light source is a laser diode. 9. The pulsed light source driving device according to claim 1, wherein the pulsed light source driving device is proportional to an input voltage,
A voltage detection device comprising a timing control device capable of changing the timing of lighting a pulse light source.