JPH0385459A - Voltage detector - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] [Table of Contents] Overview Industrial Application Fields Conventional Technology Problems to be Solved by the Invention Means for Solving the Problems Effects of the Invention [Summary] The present invention provides a voltage detection device, In particular, the purpose of the present invention is to provide a voltage detection device that can reduce the size of the device and improve detection sensitivity, with respect to a device that detects voltage using the electro-optic effect. an electro-optic crystal whose refractive index is related to the object to be detected and whose refractive index changes depending on the voltage applied to the object, wherein light is incident on the electro-optic crystal and based on reflected light from the electro-optic crystal. hand,
A voltage detection device that detects a voltage applied to a detected object,
Light generation that generates two incident lights to be incident on the electro-optic crystal, which have polarization planes parallel to two anisotropic axes induced in the crystal and have different frequencies. an optical receiver that receives two reflected lights from the electro-optic crystal, and generates a signal having a frequency difference in frequency between the two reflected lights and a detection phase; a reference phase generator that generates a phase of a signal having as a reference phase; a phase comparator that compares the detected phase from the light receiver with the reference phase from the reference phase generator and generates a phase difference between the two phases; and an arithmetic unit that calculates the voltage applied to the object to be detected based on the phase difference from the phase comparator.

[Industrial application field]

The present invention relates to a voltage detection device, and particularly to a device that detects voltage using an electro-optic effect.

When manufacturing and using semiconductor devices such as LSIs, it is necessary to accurately measure voltage signal waveforms inside and outside the device. However, with the speeding up of devices in recent years, conventional LSI
Accurate measurement is difficult with an electrical measurement method using a tester or the like. Therefore, an optical voltage signal waveform measurement method using the electro-optic effect of the semiconductor element substrate crystal was proposed.
According to this method, the voltage waveform of a high-speed signal can be measured (for example, J, A, Valamxnis gn
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elecl+onicg sampling:pri
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IEEE JOURNAL OF QUAN-TUM
ELECTRONIC3, YOL, QE-22, p
p, S9-78, etc.).

The optical voltage signal waveform measurement method described above uses a high-output pulsed laser beam as a light source and uses high-intensity light to measure weak signal voltage changes, and is a sampling method that improves detection sensitivity. Therefore,
There is a problem that the device becomes larger. In addition, as another measurement method, a method is known in which an LSI to be detected is placed on a detection crystal and the voltage signal waveform is measured (
(See Japanese Patent Application Laid-Open No. 64-28566). Even in such a method, there are challenges to achieving miniaturization of the device and improving detection sensitivity when using a small, low-power laser.

Therefore, in a voltage detection device that utilizes the electro-optic effect, it is desired to reduce the size of the device and improve detection sensitivity.

[Conventional technology]

In a conventional voltage detection device using an electro-optic effect, an electro-optic crystal is used as a converter for optically detecting an electric signal.

Normally, this electro-optic crystal contains several hundred to several 1
A voltage of 0,000 volts is applied, which is a big difference from the voltage amplitude of several pols P used inside and outside of LSI. Therefore, the measurement result light obtained as a change in the polarization plane of the measurement light has a small amplitude. Therefore, high-intensity measurement light is used to increase the amount of measurement result light, thereby improving detection sensitivity.

[Problem to be solved by the invention]

In the conventional voltage detection device using the electro-optic effect described above, the detection sensitivity is improved by using a measuring light with high intensity.Increasing the intensity of the measuring light in this way has the problem of increasing the size of the device. there were.

An object of the present invention is to provide a voltage detection device that can be miniaturized and improve detection sensitivity.

[Means to solve the problem]

A first invention includes an object to be detected to which a voltage is applied, and an electro-optic crystal body associated with the object and whose refractive index changes depending on the applied voltage of the object to be detected, and the electro-optic crystal body A voltage detection device that detects a voltage applied to an object to be detected based on the reflected light from the electro-optic crystal, the voltage detecting device detecting the voltage applied to the object based on the reflected light from the electro-optic crystal. a light generator that generates two incident lights with different frequencies and having planes of polarization parallel to the two anisotropic axes induced in the crystal; and a light generator that receives two reflected lights from the electro-optic crystal. and a reference phase generator that generates as a reference phase the phase of a signal having a frequency equal to the frequency difference between the two reflected lights and a detection phase. a phase comparator that compares the detected phase from the light receiver with a reference phase from the reference phase generator and generates a phase difference between the two phases; It is characterized in that it includes a computing unit that computes the voltage applied to the detection object.

A second invention includes an object to be detected to which a voltage is applied, and an electro-optic crystal that is associated with the object and whose refractive index changes depending on the applied voltage of the object. A voltage detection device that detects a voltage applied to an object to be detected based on the reflected light from the electro-optic crystal, the voltage detecting device detecting the voltage applied to the object based on the reflected light from the electro-optic crystal. a light generator that generates two incident lights with different frequencies and having planes of polarization parallel to the two anisotropic axes induced in the crystal; and a light generator that receives two reflected lights from the electro-optic crystal. a light receiver that generates a frequency difference between the two reflected lights as a detection frequency; a reference frequency generator that generates a frequency difference between the two incident lights as a reference frequency; and a reference frequency generator that generates a detection frequency from the light receiver as a reference frequency. A comparator that generates a frequency difference of the same frequency by comparing it with a reference frequency from the comparator, and a frequency-voltage converter that converts the frequency difference from the comparator into a voltage.
and an integrator that integrates the converted signal from the converter to determine the voltage applied to the object to be detected.

[Effect]

First, in the tJX1 invention, the object of measurement is changed from changes in light intensity to changes in optical phase, so that detection sensitivity can be improved even for relatively low intensity light. Explain the principle.

By applying a voltage, two birefringent anisotropic axes are induced in the electro-optic crystal, and the plane of polarization is parallel to the two birefringent anisotropic axes induced in the crystal. Two lights having different frequencies are made incident on the electro-optic crystal. As the refractive index of the crystal changes as the voltage applied to it changes, the light that passes through the crystal and is reflected is
Phase modulation is performed independently for each plane of polarization. By performing hetero gain detection on this phase-modulated light, a phase change is obtained, and the voltage applied to the crystal body is detected with high sensitivity based on the phase change.

Hereinafter, the operation of the first invention will be explained in detail.

Two incident lights with different frequencies and having planes of polarization parallel to two anisotropic axes induced in an electro-optic crystal are made incident on the crystal, and from the two reflected lights from the crystal, bidirectional incident light is generated. The phase of the signal having a frequency corresponding to the frequency difference is obtained as the detected phase. Furthermore, the phase of a signal having a frequency equal to the frequency difference between the two incident lights is obtained as a reference phase. The detected phase is then compared with a reference phase to determine the phase difference between the two phases, and based on the phase difference, the voltage applied to the object to be detected is determined.

Next, in the second invention, the measurement target is changed from a change in light intensity to a change in frequency so that the detection sensitivity can be improved even for light of relatively low intensity (for example, He-Ne laser light). The principle of this change will be explained below.

By applying a voltage, an electro-optic crystal (e.g. KDP:
Two birefringent anisotropic axes are induced in the vertical modulator of potassium dihydrogen phosphate (potassium dihydrogen phosphate), and the refractive index of the anisotropic axis direction changes depending on the voltage applied to the crystal. ,Change.

This change is expressed by the following formula (1)% Formula % Here, v(t) represents the voltage applied to the crystal body. The time change in the optical path length of the crystal is expressed by the crystal thickness l and Δn
It is found by differentiating the product with respect to time. That is, =±V...
(2) Equation (2) equivalently indicates that the position of the reflecting surface changes with time, and therefore Doppler displacement occurs. The frequency displacement amount Δf' is expressed by the following equation (3).

By converting the frequency displacement amount obtained in this way into a voltage and integrating it, the applied voltage (waveform) of the crystal body is obtained.

The principle of the second invention will be explained in further detail.

Birefringence induced in an electro-optic crystal When two lights with different frequencies and polarization planes parallel to the anisotropic axes are incident on the crystal, the crystal changes due to the change in the voltage applied to the crystal. Since the refractive index of the body changes, the light that passes through the crystal and is reflected changes its frequency independently for each plane of polarization (
frequency modulation). By performing heterogain detection on this frequency-modulated light, reflected light is detected as a change in beat frequency, and by integrating the detected change in beat frequency, the voltage applied to the crystal body is detected with high sensitivity.

Hereinafter, the operation of the second invention will be explained in detail.

Two incident lights with different frequencies and polarization planes parallel to the two anisotropic axes induced in the electro-optic crystal are made incident on the crystal, and two reflected lights from the crystal (this is the Doppler displacement ), the frequency difference between both reflected lights is obtained as the detection frequency. Further, the frequency difference between two incident lights (which are not affected by Doppler displacement) is obtained as a reference frequency. Then, the detected frequency is compared with a reference frequency, a frequency difference between the two frequencies is determined, the frequency difference is converted into a voltage, and the voltage is integrated to determine the voltage applied to the object to be detected.

In addition, in the second invention, when the change in the voltage applied to the crystal body is fast, such as several tens of MHz, it is possible to respond up to the comparator (for example, a frequency mixer), but the frequency -
In voltage converters and integrators, there may be a frequency range in which the response is not easy and is suitable for measurement. In such cases, the incident light to be incident on the crystal body is pulsed,
Voltage measurement can be performed using a strobe method.

〔Example〕

Hereinafter, preferred embodiments of the present invention will be described based on the drawings.

FIG. 1 shows a circuit of a voltage detection device according to a first embodiment of the invention.

In FIG. 1, the symbol 0 indicates an LSI, and the LSI
A voltage is applied to l0 from the LSI driver 12 via the terminal 10a. An electro-optic crystal 14 is disposed close to the LSI10, and as shown in FIG. On the side surface 14b, a metal film 16 for reflecting measurement light is formed as a spot-like measurement point corresponding to the terminal 10a of the LSI. When the applied voltage of LSllo acts on the spot-like metal film 16 of the crystal body 14, an electric field is generated inside the crystal body 14, and this electric field causes the crystal body 14 to
The refractive index of changes. As shown in FIG. 3, when two measuring beams are incident on the crystal body 14, the two beams reciprocate within the crystal body 14 due to the change in the refractive index of the crystal body 14 mentioned above.
The phase of the two measurement lights changes. And then, 2 underwent a change.
When a phase difference is determined by comparing the phase of one measuring beam with the phase of two unchanged measuring beams, the voltage applied to LSllo can be determined from the phase difference. The voltage detection device shown in FIG. 1 will be described in further detail below.

Reference numeral 18.20 indicates a laser driver controlled by the control circuit 22, which causes a laser beam 28.30 to be generated from a laser generator 24.26. Here, the laser beam 28.30 is transmitted to the crystal body 1
It has a plane of polarization parallel to two anisotropic axes induced by 4, and its frequency is f Sf . The laser beams 28.302 are combined into one beam by the polarizing beam splitter 32, and then split into two by the beam splitter 34, and one beam is incident on the crystal via the XY deflection mechanism 36. The spot-like metal film (measurement point) 16 of the body 14 is positioned and made incident. The reflected light from the crystal body 14 is
The light passes through the X-Y deflection mechanism 36 and the beam splitter 34, passes through the analyzer 38, and is received by the light receiver 40. Here, as mentioned above, the crystal body 1 is
Since the electric field inside the crystal body 4 changes and the refractive index of the crystal body 14 changes, the signal from the photoreceiver 40 changes from the 2
The phase of a signal with a frequency equal to the frequency difference of two reflected lights (
detection phase).

The other beam split into two by the beam splitter 34 passes through an analyzer 42 and is received by a light receiver 44. The signal from this light receiver 44 indicates the phase (reference phase) of a signal having a frequency equal to the frequency difference between the two incident lights.

The detected phase and reference phase from both the light receivers 40 and 44 are then supplied to a phase comparator 46 and compared. Here, the reference phase is indicated by Δφ (=φ1φ2=constant), and the detected phase is indicated by Δφ+Δφ′ (Δ4=φ −φ2=constant, Δφ
'oen', -yl', , n'xSnl are the refractive indices of the laser beam 28.30 respectively), and the signal from the phase comparator 46 indicates the phase difference Δφ' between the detected phase and the reference phase. , which is supplied to the arithmetic unit 48 (see FIG. 4). Based on the signal indicating the phase difference Δφ' from the phase comparator 46, the arithmetic unit 48 calculates the L
The applied voltage of SI10 can be calculated.

Next, FIG. 5 shows a circuit of a voltage detection device according to a second embodiment of the present invention. In addition, in Fig. 5, L
The SI 50, the LSI driver 52, and the electro-optic crystal 54 have the same configuration as that shown in FIG. 1.2.

Reference numeral 56 denotes a laser driver controlled by a control circuit 58. Frequencies f 2 and f 2 are supplied to the laser driver 56 from a reference frequency generator 60, and the laser driver 56 generates a two-frequency laser light generator. From 62, laser light 64 is generated. Here, the laser beam 64 has a polarization plane parallel to the two anisotropic axes induced in the crystal body 54 and has a frequency f S f2. This laser beam 64 is pulsed by a laser beam pulsing mechanism 66, passes through a beam splitter 68, and is supplied to a spot-like metal film (measurement point) of the crystal body 54 via an XY deflection mechanism 70. Ru. The reflected light from the crystal body 54 passes through an analyzer 72 via an X-Y deflection mechanism 70 and a beam splitter 68, and is sent to a light receiver 7.
The light is received at 4.

Here, the electric field inside the crystal body 54 changes due to the voltage applied to the LSI 50, and the refractive index of the crystal body 14 changes.
The optical path length of the crystal body 54 changes, and as a result, the optical path length of the crystal body 54 changes.
The position of the reflecting surface changes depending on the voltage applied to the LSI 50. Therefore, the reflected light from the crystal body 54 is reflected from the LSI 50
The signal from the light receiver 74 has a frequency difference between the two reflected lights as a detection frequency, and this is supplied to the frequency mixer 76.

The frequency mixer 76 is supplied with the frequency difference between the frequencies f and f2 (which is not affected by Doppler displacement) from the reference frequency generator 60 as a reference frequency. The detected frequency from the reference frequency generator 60 is the reference frequency Δf (=f
−f2=constant). Here, the detection frequency from the light receiver 74 is Δf+Δf' (Δf=f −
f2=■ constant, Δf' ccn 'n', n'x
, n' is laser IT
J (refractive index by light).

The signal indicating the frequency difference Δf' from the frequency mixer 76 is
After being subjected to frequency-voltage conversion through the f-V converter 78,
The signal is supplied to an integrator 80 and integrated. And integrator 8
0 determines the voltage applied to the LSI 50 based on the voltage obtained by converting the frequency difference Δf'.

6 shows voltage waveforms at each stage of the voltage detection device of FIG. 5, and the voltage obtained by integrating the output voltage from the fV converter 78 corresponds to the applied voltage of the LSI 50. That is understood.

It goes without saying that by using a two-frequency laser beam generator in the first embodiment and using two laser generators in the second embodiment, the same effect as that of the above invention can be obtained.

〔Effect of the invention〕

As explained above, according to the present invention, the voltage applied to the object to be detected is determined based on the change in phase difference or the change in frequency difference, rather than the change in light intensity, so even relatively low intensity light can be used. The voltage can be detected with high accuracy even if there is a voltage, and therefore the device can be miniaturized and the detection sensitivity can be improved.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram of a voltage detection device according to a first embodiment of the present invention, FIG. 2 is an external perspective view showing the relationship between an LSI and an electro-optic crystal, and FIG. 3 is a diagram of an electro-optic crystal. An explanatory diagram showing the relationship between the birefringence anisotropic axis and incident polarized light, FIG. 4 is a signal waveform diagram of a detection signal and a reference signal, and FIG. 5 is a circuit of a voltage detection device according to a second embodiment of the present invention. FIG. 6 is a diagram of voltage waveforms at each stage of the device of FIG. 5. 10...LS1 12...LSI driver 14...Electro-optic crystal 18.20...Laser driver 22...Control circuit 24.26...Laser light generator 28.30...Laser Light 32...Polarization beam splitter 34...Beam splitter 36...X-Y deflection mechanism 38...Analyzer 40...Light receiver 42...Analyzer 44...Light receiver 46...・Phase comparator 48... Arithmetic unit 50... LSI 52... LSI driver 54... Electro-optic crystal 56... Laser driver 58... Control circuit 60... Reference frequency generator 62 ... Two-frequency laser light generator 64 ... Laser light 66 ... Laser light pulsing mechanism 68 ... Beam splitter 70 ... X-Y deflection mechanism 72 ... Analyzer 74 ... Light reception device 76... frequency mixer 78... f-V converter 80... integrator

Claims (1)

[Claims] 1. An object to be detected (10) to which a voltage is applied, and an electro-optic crystal that is associated with the object to be detected (10) and whose refractive index changes depending on the applied voltage of the object to be detected (10). The detected object (14) is made to enter the electro-optic crystal (14), and based on the reflected light from the electro-optic crystal (14), the detected object (14) is detected.
0), which detects an applied voltage of two incident lights to be incident on the electro-optic crystal (14), and two anisotropy induced in the crystal (14). a light generator (24, 26) that generates two incident lights with polarization planes parallel to the axis and different frequencies; and a light generator (24, 26) that receives two reflected lights from the electro-optic crystal (14);
A light receiver (40) that generates a phase of a signal having a frequency equal to the frequency difference between the two reflected lights and a detection phase; and a reference phase generator that generates a reference phase that has a phase of a signal having a frequency equal to the frequency difference between the two incident lights. Vessel (44)
and a reference phase generator (
a phase comparator (46) that generates a phase difference between the two phases by comparing the phase with a reference phase from the phase comparator (44);
) A voltage detection device comprising: a calculation unit (48) that calculates the voltage applied to the detected object (10) based on the phase difference from the detected object (10). 2. The apparatus of claim 1, wherein the light generator (24, 2
6) is equipped with two semiconductor laser generators (24, 26), and voltage detection whose temperature and injection current are controlled so that their oscillation frequency is stable and the frequency difference between them is constant. Device. 3. The apparatus of claim 1, wherein the light generator (24, 2
6) is a voltage detection device that oscillates in two-frequency orthogonal polarization mode. 4. A detected object (50) to which a voltage is applied; an electro-optic crystal (54) associated with the detected object (50) and whose refractive index changes depending on the applied voltage of the detected object (50); The detected object (5) is detected based on the reflected light from the electro-optic crystal (54).
0), which detects an applied voltage of two incident lights to be incident on the electro-optic crystal (54), and two anisotropy induced in the crystal (54). a light generator (62) that generates two incident lights with polarization planes parallel to the axis and different frequencies; and a light generator (62) that receives two reflected lights from an electro-optic crystal (54);
a light receiver (74) that generates a frequency difference between both reflected lights as a detection frequency; a reference frequency generator (60) that generates a frequency difference between the two incident lights as a reference frequency; and the light receiver (74).
A comparator (76) that compares the detected frequency from the reference frequency generator (60) with the reference frequency from the reference frequency generator (60) and generates a frequency difference between the two frequencies, and converts the frequency difference from the comparator (76) into a voltage. The frequency-voltage converter (78) and the converted signal from the converter (78) are integrated, and the detected object (50
); and an integrator (80) for determining the applied voltage. 5. In the device according to claim 4, the light generator (62) includes a He-Ne laser light generator (62) that uses the Zeeman effect and performs two-frequency oscillation, and the light generator (62) uses the Zeeman effect and includes a He-Ne laser light generator (62) that performs two-frequency oscillation, so that the frequency difference between them is constant. and a voltage detection device in which the applied magnetic field strength and discharge current are controlled. 6. The apparatus of claim 4, wherein the reference frequency generator (
60) is a voltage detection device that generates a reference frequency based on the frequency from another oscillation device.