JP3489701B2 - Electric signal measuring device - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electric signal measuring device for measuring an electric signal propagating through a signal line provided on, for example, an integrated circuit, a mounting board, a printed circuit board or the like by using a laser beam.

[0002]

2. Description of the Related Art As a conventional electric signal measuring device, for example, there is an FET probe as shown in FIG. In this probe, the signal line 43 and the ground 44 of the circuit under measurement 42 are brought into contact with each other at two points, that is, the probe head 52 and the ground line 53, so that a small amount of current is taken out from the signal line 43. Coaxial wire 50
Is input to the FET input signal amplifier 51 having a high input impedance to measure the electric signal propagating through the signal line 43, and the waveform of the measured electric signal is displayed by the waveform display device 5
It is supposed to be displayed on 7.

Further, as a conventional electric signal measuring device,
For example, there is one disclosed in JP-A-5-72299. This conventional device measures the electro-optic effect generated in the electro-optic material by the electric field leaking from the signal line by bringing the probe with the electro-optic material fixed close to the signal line through which the electric signal propagates. Is a non-contact measurement of the potential of the electro-optic material, but the electric field strength changes depending on the distance between the signal line and the electro-optic material. Positioning device is needed.

[0004]

Among the conventional devices described above, in the device shown in FIG. 1, it is necessary to contact the probe at two points, and when there is no ground near the measurement point, It is not possible to measure in a wide band, or a small amount of current is taken out from the signal line, so especially in a circuit under test with a low driving force, the circuit under test is disturbed during measurement and the signal under test changes, resulting in high accuracy. There is a problem that various measurements cannot be performed.

Further, in the conventional apparatus disclosed in Japanese Unexamined Patent Publication No. 5-72299, it is necessary to position the electro-optical material with respect to the signal line with high precision, which requires a large-scale positioning device. There is a problem.

The present invention has been made in view of the above,
An object of the present invention is to provide an electric signal measuring device capable of economically measuring an electric signal propagating through a signal line with low disturbance, high accuracy, wide band, and relatively compact.

[0007]

In order to solve the above problems, the present invention is an electric signal measuring device for measuring an electric signal propagating in a signal line of a measuring object, wherein the signal line of the measuring object is provided with a single point. A conductor to be brought into contact, an electro-optical material having a birefringence that changes according to the strength of an electric field coupled from the conductor, the first surface being connected to the conductor, and the second surface facing the first surface. An electro-optical material having a surface, a laser light source that irradiates the electro-optical material with a laser beam, and a polarization detection unit that detects the laser beam that has undergone polarization change due to a change in birefringence of the electro-optical material, An optical amplifier that amplifies the amount of laser light output from the laser light source, an optical bandpass filter that removes a noise component superimposed by the optical amplifier from the output of the optical amplifier, and the optical bandpass filter. A polarization controller that linearly polarizes the laser light output by the laser, and a polarization maintaining fiber that guides the linearly polarized laser light output by the polarization controller to the electro-optical material while maintaining the polarization state. An electric signal measuring device is provided.

Also, in the present invention, the polarization controller is
A polarizer for linearly polarizing the laser light, a polarization adjusting means for adjusting the polarization of the laser light input to the polarizer, and a lens for condensing a part of the laser light output by the polarizer on the polarization maintaining fiber. , A photoelectric conversion element for converting the rest of the laser light output by the polarizer into a current, an ammeter for measuring the current output by the photoelectric conversion element, and a current value measured by the ammeter for conversion into digital data It is characterized by comprising an A / D converter and an arithmetic unit for processing the digital data output from the A / D converter to control the polarization adjusting means.

Further, in the present invention, the polarization adjusting unit drives the wavelength plate that changes the polarization of the laser light, the rotation mechanism that rotates the wavelength plate, and the rotation mechanism based on the output of the arithmetic unit. And a driver that outputs a signal.

Further, in the present invention, the polarization adjusting means controls the voltage control type polarization modulator for changing the polarization of the laser beam and the modulation by the voltage control type polarization modulator based on the output of the arithmetic unit. It is characterized by comprising a voltage generator that outputs a voltage.

The present invention also provides an electric signal measuring device for measuring an electric signal propagating through a signal line to be measured,
A conductor to be brought into contact with the signal line to be measured at a single point, and an electro-optic material whose birefringence index changes depending on the strength of an electric field coupled from the conductor, a first surface connected to the conductor, and An electro-optical material having a second surface facing the first surface, a laser light source for irradiating the electro-optical material with laser light, and the laser having undergone polarization change due to birefringence change of the electro-optical material. A polarization detection means for detecting light, wherein the polarization detection means separates the reflected laser light from the electro-optical material from the incident laser light on the electro-optical material and extracts the polarized laser light as orthogonal polarization components. , And two photoelectric conversion elements that respectively convert mutually orthogonal polarization components of the reflected laser light extracted by the optical system into electric signals, and the optical system changes the polarization of the reflected laser light. It provides a wavelength plate, an electrical signal measuring apparatus characterized by having a rotating mechanism for adjusting the intensity balance of the polarization components perpendicular to each other in rotated by the reflected laser beam through the wavelength plate.

The present invention also provides an electric signal measuring device for measuring an electric signal propagating through a signal line to be measured,
A conductor to be brought into contact with the signal line to be measured at a single point, and an electro-optic material whose birefringence index changes depending on the strength of an electric field coupled from the conductor, a first surface connected to the conductor, and An electro-optical material having a second surface facing the first surface, a laser light source for irradiating the electro-optical material with laser light, and the laser having undergone polarization change due to birefringence change of the electro-optical material. A polarization detection means for detecting light, wherein the polarization detection means separates the reflected laser light from the electro-optical material from the incident laser light on the electro-optical material and extracts the polarized laser light as orthogonal polarization components. , And two photoelectric conversion elements that respectively convert mutually orthogonal polarization components of the reflected laser light extracted by the optical system into electric signals, and the optical system changes the polarization of the reflected laser light. A voltage-controlled polarization modulator, a voltage generator that outputs a voltage that controls the modulation by the voltage-controlled polarization modulator, and a voltage that the voltage generator outputs to an electrical signal that the two photoelectric conversion elements output. An electric signal measuring device having a feedback system controlled based on the above.

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[0041]

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[0046]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings.

FIG. 2 is a diagram showing an electric signal measuring device according to the first embodiment of the present invention. In FIG. 2, reference numeral 1 is a cylindrical conductor that contacts the signal line 43 of the circuit under test 42 at one point. Since the conductor 1 has a thin signal line 43, the conductor 1 is processed into a conical shape with a thin tip according to the signal line width. A laser light source 5 irradiates the electro-optical material 2 with a pulsed laser beam. Further, when the required measurement band is not so high and is 1 GHz or less, the system configuration becomes simple CW (Continuous Wave)
A laser light source that emits light may be used.

Reference numeral 3 is a mirror that reflects the laser light 40 output from the laser light source 5. The electro-optical material 2 is electrically connected to the conductor 1 via the mirror 3. This mirror 3
Is a metal mirror 3a or a dielectric multilayer film mirror 3b formed by depositing a metal or dielectric multilayer film on the lower surface of the electro-optic material 2 as shown in FIGS. 3 (a) and 3 (b), or It is a mirror polishing mirror 3c formed by mirror polishing the upper portion of the conductor 1 as shown in FIG. 3 (c). A portion composed of the conductor 1, the electro-optic material 2, and the mirror 3 is a probe head 4.

As the electro-optical material, BSO (B which has sensitivity to an electric field in a direction parallel to the traveling direction of laser light)
i ₁₂ SiO ₂₀ ), CdTe, GaAs, LN (LiNb
O ₃ ) -55 ° cut, ZnTe, KD ^* P, CuC
l, ZnS, or KTP-Z cut is used.

As shown in FIG. 3A, as the mirror 3, a metal mirror 3a is provided between the conductor 1 and the electro-optic material 2.
In the case where the laser beam is provided, the laser beam can be completely reflected by providing the metal mirror 3a having a large area different from that of the conductor 1. That is, when the conductor 1 is thinned in order to reduce the capacitance, in the structure in which the upper surface of the conductor is a mirror, the area of the mirror becomes small and it becomes difficult to reflect the laser beam. By providing the laser light, the laser light can be completely reflected and this can be solved. Further, even if the upper surface of the conductor 1 is rough, it does not affect the reflection. Furthermore, in the structure of FIG.
And a different metal can be used for the metal mirror 3a. For example, a metal having a high reflectance such as gold, silver or platinum can be used as the mirror, and a metal having a low resistivity such as phosphor bronze can be used as the conductor. It is possible to widen the room.

Further, as shown in FIG. 3B, when the dielectric multilayer film mirror 3b is provided, the following effects are obtained. That is, generally, the electric field penetrating into the electro-optical material is proportional to the contact surface area of the conductor which is almost in contact, but when the dimension of the area of the conductor 1 is larger than the thickness of the electro-optical material 2, the electric field is the upper surface of the electro-optical material. It penetrates through, and the potential of the upper surface does not become zero. In such a state, the electric field from a signal line other than the signal line to be measured is easily affected, and the absolute value cannot be measured.
When the metal mirror 3a is used as described above, an electric field is generated from the entire metal mirror 3a, and as described above, the electric field easily penetrates the upper surface of the electro-optic material. In order to prevent this, the electric field generation source is small in the center of the electro-optic material, and the dielectric multilayer mirror 3b is used to increase the area of the mirror.

Further, as shown in FIG. 3C, when the surface of the conductor 1 is mirror-polished, there is an advantage that the structure is the simplest as compared with the other methods described above.

In the electric signal measuring device shown in FIG. 2, the conductor 1 is brought into the same potential as the signal line 43 by bringing the conductor 1 into contact with the signal line 43, and an electric field to be measured from the conductor 1 propagates through the signal line 43. 41 leaks and the electric field couples to the electro-optic material 2. A laser beam 4 is applied to the electro-optical material 2 in this state.
When 0 is entered, the polarization of the laser light 40 changes. This change in polarization is detected as a change in the intensity of electricity by the polarization detector 6, processed by the signal processor 35, and then displayed on the waveform display device 7. The polarization detector 6 includes a polarization beam splitter, a Faraday element, a wave plate, and
It is composed of optical components such as photoelectric conversion elements.

The electric field 41 coupled to the electro-optical material 2 is determined by the material and shape of the conductor 1, the electro-optical material 2 and the mirror 3 which form the probe head 4. Sufficient electro-optical material 2
Is thickened so that the electric field 41 does not reach the upper surface of the electro-optical material 2, the influence of the electric field from the adjacent signal line other than the signal line to be measured is eliminated, and the electric potential of the upper surface of the electro-optical material 2 becomes zero. In addition, since the lower surface of the electro-optical material 2 has the same potential as the signal line 43, the electric signal measuring device of the present invention has
The point contact enables absolute value measurement that does not depend on the shape of the measurement target.

More generally, the electro-optical material in the electric signal measuring device of the present invention includes a surface to which a conductor is connected and a surface opposite to this surface, the potential of which is the signal line to be measured and other than that. And a facing surface that does not change due to an electric field from the signal line. Specifically, for example, when the measurement symmetry is 10 GHz, the diameter of the conductor 1 is 0.5 mm,
The height is 4 mm, the diameter of the conductor 1 is 2 mm and the height is 8.5 mm when the measurement symmetry is 5.5 GHz. In each case, the thickness of the electro-optic material 2 is relative to the diameter of the conductor 1. It is desirable that the thickness is sufficiently thicker than 5 mm.

Further, in the electric signal measuring device of the present invention, a known electric signal is measured in advance using an appropriate signal line, and a correction coefficient is obtained from the relationship between the known voltage of the electric signal and the signal strength detected by the probe. Is calculated and stored, and the voltage axis can be calibrated by correcting the signal strength detected using this correction coefficient during the actual measurement of the measurement target. That is, as shown in FIG. 4, an electric signal 91 having a known voltage is applied to a predetermined reference wiring 90 from a predetermined signal source 92, and the probe head 4 of the electric signal measuring device of the present invention is applied to the reference wiring 90. The measurement is performed by contacting at one point, the correction coefficient is obtained by the signal processing device 35 from the relationship between the detected signal strength and the known voltage of the electric signal 91,
The correction coefficient is stored in the memory 35A in the signal processing device 35. After that, at the time of actually measuring the measurement target, the detected signal strength is multiplied by the correction coefficient stored in the memory 35A, and then displayed on the waveform display device 7. The reference wiring 90 and the signal source 92 shown in FIG. 4 may be provided in the apparatus body as a part of the electric signal measuring apparatus of the present invention. Also,
An electrical signal 91 having a known voltage has a low frequency, eg 1
In the case of 0 MHz, a metal terminal may be used instead of the reference wiring 90. FIG. 5 shows a modification of the electric signal measuring device of FIG. 2 in which the electro-optical material 2 is fixed (or held) to the laser light source 5 and the polarization detector 6 via an insulating fixture 60. It is a thing.

With this arrangement, the positional relationship between the laser light source 5 and the polarization detector 6 with respect to the electro-optical material 2 can be fixed. Therefore, if the optical axis of the laser is adjusted once at the initial stage of the device assembly, the adjustment is required thereafter. Since there is no need for an optical system adjusting mechanism inside the device, the device can be downsized.

FIG. 6 is a diagram showing a modified example of the electro-optical material 2 that can be used in the above-described embodiment. Figure 6 (a)
Is an electrode 2a that is electrically isolated from the conductor 1 and has a fixed potential that is irrelevant to the potential of the conductor 1 and is provided on the side surface of the electro-optical material 2. Also, FIG. Is provided on the upper surface of the electro-optical material 2 with a transparent electrode 2b having a fixed potential that is electrically isolated and separated from the potential of the conductor 1.

As shown in FIG. 6A, the electro-optic material 2
By providing the electrodes 2a on both side surfaces of the electro-optical material, it is possible to absorb the electric field entering the electro-optical material 2 into the electrode by appropriately selecting the potential of the electrode.
Can be prevented from penetrating to the upper surface. See also FIG.
As shown in (b), when the transparent electrode 2b is provided on the upper surface of the electro-optical material 2, laser light can be transmitted and the electric field is similarly prevented from penetrating to the upper surface of the electro-optical material 2. can do. The structure shown in FIG. 6 can be applied to all the structures shown in FIG.

FIG. 7 shows LT (LiTaO ₃ ) and LN having sensitivity to an electric field in a direction orthogonal to the traveling direction of laser light.
(LiNbO ₃ ), KTP, DAST, or AAN
It is an example of composition of probe head 4 when it is set as electro-optic material 2'using P. FIG. 7A shows a configuration example in which a conductor 1'having a bent portion at a right angle is connected to one side surface of the electro-optical material 2 '. FIG. 7B shows a configuration example in which a mirror for reflecting the laser beam 40 is added to the lower surface of the electro-optical material 2 ′ in the configuration of FIG. 7A. FIG. 7C shows a conductor 1 via a conductive wire 1a having a bent portion at a right angle to the electrode 1b connected to one side surface of the electro-optical material 2 '.
And an electrode 2a 'electrically isolated from the conductor 1 is added to the surface facing the one side surface. 7D is a surface other than the surface facing the one side surface in place of the electrode 2a ′ in the configuration of FIG. 7C (for example, FIG. 7D).
Then the upper surface) and the electrode 2 electrically isolated from the conductor 1.
The structural example which added b'is shown. When such an electro-optic material 2'is used, the mirror 3 has the structure shown in FIG.
The dielectric multilayer mirror as shown in (b) is used.

FIG. 8 is a diagram showing the configuration of an electric signal measuring apparatus according to the second embodiment of the present invention. This electrical signal measuring device constitutes a hand-held probe, and particularly shows in detail the configuration from the generation of laser light to the waveform display in FIG. In FIG. 8, 4 is a probe head composed of the conductor 1, the electro-optic material 2 and the mirror 3 shown in FIG.
It is attached to 2. Reference numeral 9 is a polarization maintaining fiber that introduces the laser light 40 generated from the laser light source 5 into the probe main body 32. When laser light of appropriate linear polarization is incident on the polarization maintaining fiber 9 from the laser light source 5, the laser light can be introduced into the probe main body 32 while maintaining linear polarization even when disturbance such as twisting of the fiber portion is applied. Therefore, the measurement conditions do not change even if the probe main body 32 is tilted at an arbitrary angle for measurement. In FIG. 8, thick arrows indicate the flow of laser light, and thin arrows indicate the flow of electrical signals.

In the first polarization beam splitter 11, the polarization component parallel to the paper surface of the laser light 40 goes straight, and the polarization component perpendicular to the paper surface is bent at 90 °. The polarization of the laser beam 40 is rotated by 45 ° by the Faraday element 12, and the polarized light is returned by the 45 ° rotated by the Faraday element 12 by the next first wave plate 13. With such an optical system, the laser light 40 reflected by the probe head 4
Can be separated from the incident light and can be obtained as polarization components orthogonal to each other by the first polarization beam splitter 11 and the second polarization beam splitter 14. After the separation, the first photoelectric conversion element 17 and the second photoelectric conversion element 18 convert the signal into an electric signal, and then the differential amplifier 19 detects a signal component having an opposite phase. Here, the noise becomes an in-phase component and is removed by differential detection. The second wave plate 15 has a mechanism that allows it to rotate about the optical axis of the laser light 40, and as a result, the intensity of the two separated laser lights is balanced and S
/ N is adjusted to be large, and the S / N of the signal detected by this can be adjusted. The signal detected by the differential amplifier 19 is the waveform display device 7
Captured in and the waveform is displayed.

By miniaturizing the above-mentioned optical components into a small-sized module and hand-held, the measurement can be easily performed even when there is a restriction on the measurement environment such as a board or a printed circuit board incorporated in the apparatus.

FIG. 9 is a diagram showing the configuration of an electric signal measuring device according to a third embodiment of the present invention, which is a more specific version of the electric signal measuring device of FIG. The device shown in FIG.
The probe head 4 including the conductor 1, the electro-optical material 2, and the dielectric multilayer mirror 3 is attached to the probe main body 32 by the insulating holder 31. Has been done.

In the configuration shown in FIG. 9, when the power of the laser light 40 output from the laser light source 5 is small, the laser light 40 is amplified by using the optical amplifier 39, and the noise component superimposed by using the optical amplifier 39 is removed. It is removed by the optical bandpass filter 38. When the power of the laser light 40 output from the laser light source 5 is high, the optical amplifier 39 and the optical bandpass filter 38 may not be used.

Numeral 8 linearly polarizes the laser light 40 output from the optical bandpass filter 38, and the polarization maintaining fiber 9
It is a polarization controller that is incident on. Here, the polarization direction of the laser light 40 output from the polarization controller 8 is adjusted in the polarization controller 8 so that the polarization is preserved in the polarization maintaining fiber 9. With this adjustment, the laser beam 40 can be incident on the probe body 32 while maintaining the linearly polarized light even if a disturbance such as twisting or bending of the polarization maintaining fiber 9 is applied. The measurement conditions do not change even when tilted.

Laser light 4 output from polarization maintaining fiber 9
0 becomes parallel light by the collimating lens 10. In the first polarization beam splitter 11, the laser light 40 has a polarization component in a direction parallel to the paper surface that goes straight, and a polarization component that is perpendicular to the paper surface has its travel direction bent by 90 degrees. The polarization of the laser beam 40 is rotated by 45 degrees at the Faraday element 12. The first λ / 2 wave plate 13 which is rotated by the Faraday element 12 by only 45 degrees
The direction of polarization returns. With such an optical system, the laser light 40 reflected by the probe head 4 can be separated from the incident light and can be obtained as polarization components orthogonal to each other by the first polarization beam splitter 11 and the second polarization beam splitter 14. After the separation, the first photoelectric conversion element 17 and the second photoelectric conversion element 18 convert it into an electric signal, and the differential amplifier 19 detects a signal component having an opposite phase. In this case, the noise becomes the in-phase component, so it is removed by differential detection. λ /
The four-wave plate 15A and the second λ / 2-wave plate 15B are used for the laser light 4
It has a mechanism that can rotate about the optical axis of 0, so that the S / N becomes large while balancing the intensity of the laser light reaching the first photoelectric conversion element 17 and the second photoelectric conversion element 18. The S / N ratio of the signal detected as a result can be adjusted. Of the signal output from the differential amplifier 19, only the frequency component containing the signal under measurement is passed by the electrical bandpass filter 36, and the averaged value is added by the averager 37. Display it.

FIG. 10 is a diagram showing in detail the configuration of the polarization controller 8 used in the apparatus of FIG. The laser light 40 output from the laser light source 5 is emitted from the λ / 4 wavelength plate 20 and λ
It can be changed to an arbitrary polarization state by rotation of the / 2 wavelength plate 22. The λ / 4 wave plate 20 and the λ / 2 wave plate 22 are connected to the first rotating mechanism 21 and the second rotating mechanism 23, respectively. The laser light passing through the two wave plates is polarized 25
When incident on, the linearly polarized light components orthogonal to each other are output.
One of the linearly polarized laser lights output from the polarizer 25 is incident on the photoelectric conversion element 27, and the other one is a condenser lens 34.
The light is collected by and is incident on the polarization maintaining fiber 9.

The amount of laser light received by the photoelectric conversion element 27 is measured as an electric current by the ammeter 28, this value is converted into digital data by the A / D converter 29, and then the photoelectric conversion element 2
The arithmetic unit 30 sends a command to the driver 24 that drives the first rotating mechanism 21 and the second rotating mechanism 23 so that the amount of laser light received at 7, that is, the current detected by the ammeter 28 becomes minimum, and λ / The rotations of the four-wave plate 20 and the λ / 2-wave plate 22 are adjusted. With such a configuration, linearly polarized laser light can always be efficiently incident on the polarization maintaining fiber 9. Here, the direction of the incident surface of the polarization maintaining fiber 9 is adjusted so that the polarization of the linearly polarized laser light is preserved so that the polarization direction of the laser light and the polarization maintaining direction of the polarization maintaining fiber 9 are aligned. It

Further, instead of the laser light output from the polarizer 25 being received by the photoelectric conversion element 27, a beam splitter is provided between the polarizer 25 and the condensing lens 34, and among the laser light entering the polarization maintaining fiber 9, Of the laser light is received by the photoelectric conversion element 27, and the λ / 4 wavelength plate 20 and the λ / 2 wavelength are adjusted so that the light amount of the laser light, that is, the current detected by the ammeter 28 becomes maximum. The rotation of the plate 22 may be adjusted.

Furthermore, the λ / 4 wave plate 20 and the λ / 2 wave plate 2
The above control system may be configured by using a polarization modulator capable of controlling the polarization of the laser light by a voltage instead of 2, and using a voltage generator generating a control signal instead of the driver. That is, as shown in FIG. 11, λ / 4 of FIG.
The wave plate 20, the first rotation mechanism 21, the λ / 2 wave plate 22, and the second rotation mechanism 23 are replaced with a voltage control type polarization modulator 61,
The driver 24 may be replaced with the voltage generator 62.

The configuration of FIG. 9 may be modified as shown in FIG. That is, the λ / 4 wave plate 15A and the λ /
The two-wave plate 15B is replaced with a voltage control type polarization modulator 15C, and the output of the differential amplifier 19 and the voltage control type polarization modulator 15 are replaced.
A / D converter 63, calculator 64, voltage generator 6 between C
5 is provided. In this case, it is possible to detect the deviation of the balance of the laser light intensity reaching the first photoelectric conversion element 17 and the second photoelectric conversion element 18 from the output of the differential amplifier 19, and the deviation is detected by the A / D converter 63. A feedback system is configured to control the voltage generator 65 from the arithmetic unit 64 so that the voltage that corrects the D / D conversion is input to the arithmetic unit 64 and the voltage that corrects the deviation is input to the voltage-controlled polarization modulator 15C. This makes it possible to quickly adjust the S / N to a good state.

Further, the configuration of FIG. 9 may be modified as shown in FIG. That is, the semiconductor laser 71 may be built in the probe main body 32, and the laser driver 72 that generates an electric signal for causing the semiconductor laser 71 to emit light may be provided outside the probe main body 32. In this case, when viewed from the outside of the probe main body 32, an electric signal is input to the probe main body 32 to obtain an output of the electric signal.

FIG. 14 shows various configurations of the probe head 4 and the insulating holder 31 which can be used in the device of FIG. It has a buffer mechanism for protecting the optical material 2 and the mirror 3. FIG. 14A shows a probe head in which the conductor 1, the electro-optic material 2 and the mirror 3 are integrated, and a protrusion-shaped stopper 1A that abuts the insulating holder 31a is provided on the side of the conductor 1. And also in FIG.
(B) shows that the conductor 1 is separated from the electro-optical material 2 and the mirror 3 and held by the insulating holder 31b, and the conductive and elastic wire 81 is provided between the conductor 1 and the mirror 3. In FIG. 14C, an insulating holder 31c is provided with an elastic body 82 such as a spring having a degree of freedom only in the same direction as the optical axis of the laser beam, and the conductor 1 is held through the elastic body 82.

As shown in FIG. 14A, by providing the stopper 1A on a part of the conductor 1, the shock generated when the conductor 1 contacts the signal line is received by the entire insulating holder 31a through the stopper 1A. The impact on the electro-optic material 2 can be mitigated. Further, as shown in FIG. 14B, by providing a conductive and elastic wire 81 between the conductor 1 and the mirror 3, the impact generated when the conductor 1 contacts the signal line is bent. Can be absorbed and the impact on the electro-optical material 2 can be mitigated.
In addition, as shown in FIG. 14C, the insulating holder 31c
By providing the elastic body 82 such as a spring on the core 1, the impact generated when the conductor 1 contacts the signal line can be absorbed by the elasticity of the elastic body 82, and the impact on the electro-optic material 2 can be mitigated.

Further, as shown in FIG. 14 (d), a recessed notch is provided on the side of the conductor 1, and the side of the conductor 1 including the recessed notch is attached to the insulating holder 31d with an adhesive 83. You may fix with. In this case as well, similarly to the case shown in FIG. 14A, the shock generated when the conductor 1 contacts the signal line is received by the entire insulating holder 31d, so that the shock to the electro-optic material 2 can be mitigated.

[0077]

As described above, according to the present invention,
A conductor is brought into contact with a signal line, an electric field generated from the conductor is coupled, and an electro-optic material whose birefringence index changes according to the strength of the coupling electric field is irradiated with laser light to polarize the birefringence of the electro-optic material. Since the changed laser light is detected, current is not taken out from the signal line to the signal detection section as in the past, so the electrical signal propagating through the signal line can be spread with high precision and low disturbance in a wide band. Since it can be measured and does not require a large scale positioning device, it can be constructed economically and relatively compactly.

[Brief description of drawings]

FIG. 1 is a diagram showing a schematic configuration of an example of a conventional electric signal measuring device.

FIG. 2 is a diagram showing a schematic configuration of an electric signal measuring device according to a first embodiment of the present invention.

FIG. 3 is a diagram showing a configuration of various mirrors that can be used in the electric signal measuring device of FIG.

FIG. 4 is a diagram showing a configuration for calibrating a voltage axis in the electric signal measuring device of FIG.

FIG. 5 is a diagram showing a schematic configuration of a modified example of the electric signal measuring device of FIG.

6 is a diagram showing a modified configuration example of an electro-optical material that can be used in the electrical signal measuring device of FIG.

7 is a diagram showing another configuration example of an electro-optical material that can be used in the electrical signal measuring device of FIG.

FIG. 8 is a diagram showing a configuration of an electrical signal measuring device according to a second embodiment of the present invention.

FIG. 9 is a diagram showing a configuration of an electrical signal measuring device according to a third embodiment of the present invention.

10 is a diagram showing an example of a configuration of a polarization controller used in the electric signal measuring device shown in FIG.

11 is a diagram showing another example of the configuration of the polarization controller used in the electrical signal measuring device shown in FIG.

FIG. 12 is a diagram showing a configuration of a modification of the electric signal measuring device of FIG. 9.

FIG. 13 is a diagram showing the configuration of another modification of the electric signal measuring device of FIG. 9.

FIG. 14 is a diagram showing a configuration of a probe head having various buffering mechanisms that can be used in the electric signal measuring device shown in FIG.

[Explanation of symbols]

1 conductor 2 Electro-optical material 3 mirror 4 probe head 5 Laser light source 6 Polarization detector 7 Waveform display device 8 Polarization controller 9 Polarization maintaining fiber

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI H01L 21/66 G01R 15/07 C (72) Inventor Ken Takeya 1-1-6 Uchisaiwaicho, Chiyoda-ku, Tokyo Nippon Telegraph and Telephone Corporation (56) Reference JP-A-4-350568 (JP, A) JP-A-5-34378 (JP, A) JP-A-1-147376 (JP, A) JP-A-5-267408 (JP, A) JP 5-47883 (JP, A) JP 63-19682 (JP, A) JP 6-102295 (JP, A) JP 63-196862 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) G01R 1/06-1/073 G01R 15/00-19/00 G01R 31/28-31/3193 G02F 1/03 H01L 21/64-21/66

Claims (6)

(57) [Claims] 1. An electric signal measuring device for measuring an electric signal propagating through a signal line to be measured, comprising: a conductor to be brought into contact with the signal line to be measured at one point; and a strength of an electric field coupled from the conductor. An electro-optical material having a birefringence variable, the electro-optical material having a first surface connected to the conductor, and a second surface facing the first surface; A laser light source for irradiating laser light, a polarization detecting means for detecting the laser light that has undergone polarization change due to a change in birefringence of the electro-optic material, and an optical amplifier for amplifying the light amount of the laser light output by the laser light source. An optical bandpass filter for removing a noise component superimposed by the optical amplifier from the output of the optical amplifier, and a polarization control for linearly polarizing the laser light output by the optical bandpass filter. When an electrical signal measuring apparatus characterized by having a polarization maintaining fiber for guiding the linearly polarized of laser light the polarization controller is output to the electro-optic material while maintaining the polarization state. 2. The polarization controller includes a polarizer that linearly polarizes the laser light, a polarization adjusting unit that adjusts the polarization of the laser light input to the polarizer, and a part of the laser light output by the polarizer. A lens for focusing on the polarization maintaining fiber, a photoelectric conversion element for converting the rest of the laser light output by the polarizer into a current, an ammeter for measuring the current output by the photoelectric conversion element, and the ammeter. An A / D converter for converting the measured current value into digital data, and an arithmetic unit for processing the digital data output from the A / D converter to control the polarization adjusting means. The electric signal measuring device according to claim 1. 3. The polarization adjusting means outputs a wave plate for changing the polarization of the laser light, a rotating mechanism for rotating the wave plate, and a signal for driving the rotating mechanism based on the output of the computing unit. The electrical signal measuring device according to claim 2, comprising a driver. 4. The polarization adjusting means outputs a voltage control type polarization modulator for changing the polarization of laser light and a voltage for controlling the modulation by the voltage control type polarization modulator based on the output of the arithmetic unit. The electrical signal measuring device according to claim 2, further comprising a voltage generator. 5. An electric signal measuring device for measuring an electric signal propagating through a signal line to be measured, comprising: a conductor to be brought into contact with the signal line to be measured at one point; and a strength of an electric field coupled from the conductor. An electro-optical material having a birefringence variable, the electro-optical material having a first surface connected to the conductor, and a second surface facing the first surface; A laser light source that irradiates a laser beam, and a polarization detection unit that detects the laser beam that has undergone polarization change due to a change in birefringence of the electro-optical material are provided, and the polarization detection unit is a reflection from the electro-optical material. An optical system that separates the laser light from the incident laser light to the electro-optical material and extracts the polarized light components that are orthogonal to each other, and an orthogonal polarization component of the reflected laser light that is extracted by the optical system are electrically transmitted. And two optical conversion elements for converting the optical system, the optical system, a wavelength plate for changing the polarization of the reflected laser light, and the intensity of polarization components of the reflected laser light orthogonal to each other by rotating the wavelength plate. An electric signal measuring device having a rotating mechanism for adjusting balance. 6. An electric signal measuring device for measuring an electric signal propagating through a signal line to be measured, comprising: a conductor to be brought into contact with the signal line to be measured at one point; and a strength of an electric field coupled from the conductor. An electro-optical material having a birefringence variable, the electro-optical material having a first surface connected to the conductor, and a second surface facing the first surface; A laser light source that irradiates a laser beam, and a polarization detection unit that detects the laser beam that has undergone polarization change due to a change in birefringence of the electro-optical material are provided, and the polarization detection unit is a reflection from the electro-optical material. An optical system that separates the laser light from the incident laser light to the electro-optical material and extracts the polarized light components that are orthogonal to each other, and an orthogonal polarization component of the reflected laser light that is extracted by the optical system are electrically transmitted. And two photoelectric conversion elements for converting the optical system, the optical system outputs a voltage for controlling the modulation by the voltage control type polarization modulator for changing the polarization of the reflected laser light, and the voltage control type polarization modulator. And a feedback system for controlling the voltage output by the voltage generator based on the electrical signals output by the two photoelectric conversion elements.