JP3418577B2 - Electro-optic probe - Google Patents

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to coupling an electric field generated by a signal under measurement to an electro-optic crystal, injecting light into the electro-optic crystal, and observing the waveform of the signal under measurement depending on the polarization state of the incident light. The present invention relates to an electro-optic probe for

[0002]

2. Description of the Related Art It is possible to observe the waveform of a signal under measurement by coupling an electric field generated by the signal under measurement with an electro-optic crystal, injecting laser light into the electro-optic crystal, and observing the polarization state of the laser light. Here, pulse the laser light,
When the signal under measurement is sampled, it can be measured with very high time resolution. An electro-optic sampling oscilloscope uses an electro-optic probe that takes advantage of this phenomenon.

This electro-optical sampling (Electro Opt
ic Sampling) oscilloscope (hereinafter abbreviated as “EOS oscilloscope”), compared to a conventional sampling oscilloscope that uses an electric probe, 1) does not require a ground line when measuring a signal. Easy 2) Since the metal pin at the tip of the electro-optic probe is insulated from the circuit system, a high input impedance can be realized, and as a result, the state of the measured point is hardly disturbed 3) Since an optical pulse is used It has attracted attention because it has a feature that it can measure wideband up to GHz order.

The configuration of a conventional electro-optical probe 1 used when measuring signals with an EOS oscilloscope will be described with reference to FIG. In the electro-optic probe 1 shown in FIG. 7, a probe head 3 made of an insulator is provided at the tip of a probe body 2, and a metal pin 3 is provided at the center thereof.
a is fitted. In addition, the probe head 3 has
The electro-optical element 4 is fixed. This electro-optical element 4
Is provided with a reflection film 4a on the end face on the metal pin 3a side and is in contact with the metal pin 3a. Also, reference numeral 5
Is a half-wave plate, and reference numeral 6 is a quarter-wave plate. Reference numerals 7 and 8 are polarization beam splitters. Reference numeral 9 is
It is a half-wave plate, and reference numeral 10 is a Faraday element. Reference numeral 12 is a collimating lens, and reference numeral 13
Is a laser diode. Reference numerals 14 and 15 are condenser lenses, and reference numerals 16 and 17 are photodiodes.

Two polarization beam splitters 7,
The 8, 1/2 wave plate 9 and the Faraday element 10 allow the light emitted by the laser diode 13 to pass therethrough and separate the light reflected by the reflection film 4a.
Is.

Next, the optical path of the laser light emitted from the laser diode 13 will be described with reference to FIG.
In FIG. 7, the optical path of the laser light is represented by the symbol A. First,
The laser light emitted from the laser diode 13 is converted into parallel light by the collimating lens 12, goes straight through the polarization beam splitter 8, the Faraday element 10, the half-wave plate 9 and the polarization beam splitter 7, and further, the quarter-wave plate. 6 and 1
It enters the electro-optical element 4 through the / 2 wave plate 5. The incident light is reflected by the reflection film 4a formed on the end surface of the electro-optical element 4 on the metal pin 3a side.

The reflected laser light is transmitted again to the half-wave plates 5 and 1.
A part of the laser light passing through the / 4 wavelength plate 6 is reflected by the polarization beam splitter 7, is condensed by the condenser lens 14, and is incident on the photodiode 16. On the other hand, the laser beam transmitted through the polarization beam splitter 7 is reflected by the polarization beam splitter 8, condensed by the condenser lens 15, and enters the photodiode 17. 1/2
The wave plate 5 and the quarter wave plate 6 are adjusted in rotation angle with respect to their optical axes so that the laser beams incident on the photodiode 16 and the photodiode 17 have the same intensity.

Next, the operation of measuring the signal under measurement using the electro-optical probe shown in FIG. 7 will be described. When the metal pin 3a is brought into contact with the measurement point, the electric field in the electro-optical element 4 propagates to the electro-optical element 4 due to the voltage applied to the metal pin 3a, and the phenomenon that the birefringence changes due to the Pockels effect occurs. As a result, the laser light emitted from the laser diode 13 enters the electro-optical element 4, and the polarization state of the light changes when the laser light propagates through the electro-optical element 4. Then, the laser light whose polarization state has changed is reflected by the reflection film 4a, is condensed and incident on the photodiodes 16 and 17, and is converted into an electric signal.

Along with the change in the voltage at the measuring point, the change in polarization state due to the electro-optical element 4 is changed by the photodiode 1.
6 and the output of the photodiode 17 occur, and by detecting this output difference, the metal pin 3
The electrical signal applied to a can be measured. In the electro-optical probe 1 described above, the electric signals obtained from the photodiodes 16 and 17 are input to the electro-optical sampling oscilloscope and processed.
Alternatively, a conventional measuring instrument such as a real-time oscilloscope may be connected to the photodiodes 16 and 17 via a dedicated controller to perform signal measurement. Thereby, the broadband measurement can be easily performed using the electro-optic probe 1.

[0010]

As described above, in the signal measurement using the electro-optic probe 1, the metal pin 3 is used.
Since it is necessary to bring a into contact with the measurement point, the metal pin 3a may wear due to repeated measurement, and the probe head 3 may need to be replaced. In such cases,
Since the electro-optical element 4 fixed to the probe head 3 is expensive, the cost is high.

Further, in general, while the optimum type of metal pin changes depending on the characteristics of the signal to be measured, etc., in the electro-optical probe 1 described above, the metal pin 3a is fixed to the probe head 3. Moreover, even if an attempt is made to select the most suitable metal pin 3a in accordance with the characteristics of the signal under measurement, it is difficult to handle it.

In view of such circumstances, it is an object of the present invention to provide an electro-optical probe in which the metal pin can be easily replaced.

[0013]

In order to solve the above problems, the following means are adopted in the present invention. The electro-optical probe according to claim 1, wherein an optical path is formed inside the probe main body between a proximal end side and a distal end side of the probe main body, and one end of the optical path on the proximal end side of the probe main body is formed. A laser diode is arranged, and at the other end of the optical path on the tip end side of the probe body, an electro-optical element is arranged so as to be held by a probe head forming the tip end of the probe body, The head is provided with a metal pin, the base end of which is connected to the electro-optical element and the tip of which is projected from the probe head, and the laser light emitted from the laser diode is passed through the optical path. It is incident on an optical element, the incident light is reflected by a reflection film provided on the electro-optical element, and the reflected light is separated to be reflected by a photodiode. The probe head is configured to be converted into an electric signal, and includes a head body that holds the electro-optical element, and a tip member that is detachably provided on the head body and holds the metal pin. It is characterized by being configured.

With such a structure, in this electro-optical probe, the metal pin can be easily replaced by replacing the tip member.

An electro-optical probe according to a second aspect of the present invention is the electro-optical probe according to the first aspect, wherein one of the head body and the tip member has a male screw portion protruding toward the other. Is provided on the other side, and a female screw portion that fits with the male screw portion is formed on the other side, and the male screw portion and the female screw portion are removable.

The electro-optic probe according to claim 3 is the electro-optic probe according to claim 1, wherein the tip member is provided with a screw hole, and the tip member is arranged in the screw hole. It is characterized in that it is fixed to the head body by means of screws.

The electro-optical probe according to claim 4 is the electro-optical probe according to any one of claims 1 to 3, wherein the electro-optical element and the base end of the metal pin are the electro-optical element and the electro-optical element. It is characterized in that they are connected to each other via a buffer plate that absorbs impact due to contact between the metal pins.

With this structure, in this electro-optical probe, it is possible to prevent the electro-optical element from being damaged by contact with the metal pin when the tip member is attached to or detached from the probe body. .

An electro-optic probe according to claim 5 is the electro-optic probe according to any one of claims 1 to 4, wherein the photodiode and the laser diode are connected to an electro-optic sampling oscilloscope,
The laser diode emits the laser light as pulsed light based on a control signal from the electro-optic sampling oscilloscope.

An electro-optical probe according to a sixth aspect is the electro-optical probe according to any one of the first to fourth aspects, wherein the laser diode emits continuous light as the laser light.

As described above, in the electro-optic probe according to the sixth aspect, the continuous output can be obtained from the photodiode by causing the laser diode to emit continuous light, and therefore, the photodiode is exclusively used. It is also possible to connect to a conventional general-purpose measuring instrument such as a real-time oscilloscope via the controller to perform measurement.

[0022]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. 1 and 2 are a vertical sectional view and a plan view of an electro-optical probe 21 showing an embodiment of the present invention. The electro-optic probe 21 has a schematic structure in which an optical path 23 is formed inside a probe body 22.

The probe main body 22 has a tip 22a formed as a probe head 24, and a laser diode 25 housed in a base 22b. The laser diode 25 has an optical path 23.
End 23 of the probe body 22 on the base end 22b side
It is located at a and is connected to an EOS oscilloscope (not shown).

On the other hand, the probe body 22 in the optical path 23
Of the electro-optical element 26 at the other end 23b on the side of the tip 22a of the
Are arranged. The electro-optical element 26 is held by the probe head 24, and the electro-optical element 2
The probe body 22 of No. 6 has a structure in which a reflection film 28 is formed on the end surface 26a on the side of the tip portion 22a.

The probe head 24 also has a head body 30 for fixing the electro-optical element 26, and a tip member 31 provided at the tip of the head body 30. As shown in the figure, the head body 30 has
A male screw portion 30 a protruding toward the tip member 31 side is provided, while the tip member 31 has a male screw portion 30 a.
A female screw portion 31a capable of fitting with a is provided. The tip member 31 is configured to be detachable from the head body 30 by the male screw portion 30a and the female screw portion 31a.

A metal pin 32 is fixed to the tip member 31. The metal pin 32 has a base end 32a connected to the electro-optical element 26, and a tip 32b protruding from the tip member 31.

On the other hand, on the optical path 23, a collimator lens 33 and a polarization beam splitter 3 are sequentially arranged from the right side in the figure.
4, Faraday element 35, polarization beam splitter 37,
The quarter-wave plate 38 is arranged. Photodiodes 41 and 42 are provided on the sides of the optical path 23 corresponding to the polarization beam splitters 34 and 37. The photodiodes 41 and 42 are connected to the EOS oscilloscope, and are capable of converting incident light into an electric signal and transmitting the electric signal to the EOS oscilloscope.

Further, the polarization beam splitters 34, 37
Is to function as an isolator that separates a part of the light passing through the optical path 23 and reflects it toward the photodiodes 41 and 42.

When the electro-optical probe 21 is used for signal measurement, the EOS oscilloscope is activated with the tip 32b of the metal pin 32 in contact with the measurement point. As a result, based on the control signal emitted from the EOS oscilloscope, laser light is emitted from the laser diode 25, this laser light is converted into parallel light by the collimator lens 33, goes straight on the optical path 23, and reaches the electro-optical element 26.
To reach.

The laser light reaching the electro-optical element 26 is
The light enters the reflection film 28 and is reflected by the light path 2
3 will proceed to the laser diode 25 side. At this time, the electro-optical element 26 is in a state in which the birefringence has changed due to the change in the electric field at the measurement point propagated through the metal pin 32, so that the laser light is emitted from the electro-optical element 2.
The polarization state changes as it propagates through the polarization beam splitter 6, and the polarization beam splitters 34, 3
It is separated by 7, and is collected and incident on the photodiodes 41 and 42, and is converted into an electric signal. This allows
Photodiodes 41 and 4 are used to detect changes in the polarization state of laser light.
It is possible to measure the electric signal at the measurement point by detecting as the output difference of 2.

When such signal measurement is repeatedly performed, the metal pin 32 is worn away from the tip 32b side, and therefore the metal pin 32 needs to be replaced. In the optical probe 21, since the tip end member 31 is detachably attached to the head body 30, if the metal pin 32 is replaced with the tip end member 31, the metal pin 32 can be easily replaced. It can be carried out. Due to this, unlike the conventional
When replacing the metal pin 32, the probe head 2
It is not necessary to replace the entire unit 4, and as a result, it is not necessary to replace the expensive electro-optical element 26, which is advantageous in terms of cost.

Further, in this electro-optical probe 21, the tip member 31 can be easily replaced with one having the most suitable metal pin 32 according to the characteristics of the signal to be measured, etc. Therefore, the measurement accuracy can be improved.

The above is one example of an embodiment of the present invention, but the present invention is not limited to the above embodiment, and changes in shape, structure, etc. can be made without departing from the spirit of the present invention. It is possible.

For example, as shown in FIG. 3, a buffer plate 44 is provided between the electro-optical element 26 and the base end 32a of the metal pin 32, so that the metal pin 32 and the electro-optical element can be attached and detached when the tip member 31 is attached or detached. The shock generated between the element 26 and the element 26 may be reduced. In this case, the electro-optical element 26
The risk of damage to the electro-optic probe 21 is reduced, and the durability of the electro-optic probe 21 can be improved.

Further, the means for fixing the tip member 31 to the head body 30 is not necessarily limited to the above-mentioned embodiment, and for example, the tip member 31 side has a male screw portion and the head body 30 side has a female screw portion. May be provided. Also,
As shown in FIG. 4, a screw hole 45 may be provided in the tip member 31, and a screw 46 may be provided in the screw hole 45 to fix the tip member 31 to the head body 30. Of course, in this case as well, as shown in FIG. 5, a buffer plate 44 may be provided between the electro-optical element 26 and the base end 32a of the metal pin 32.

Separately from this, as shown in FIG. 6, the metal pin 32 is divided into a base end portion 32c and a tip end portion 32d, and the base end portion 32 is separated from the electro-optical element 26.
And the front end portion 32d is fixed to the front end member 31, and the base end portion 32c and the front end portion 32d may be integrated when the front end member 31 is fitted to the head body 30. Good.

By doing so, the metal pin 32
The positional relationship between the base end 32a and the electro-optical element 26 can be made constant, and highly accurate measurement can be realized. Further, in this case, if a silver paste is arranged between the base end portion 32c and the tip end portion 32d, these can be integrated well.

Further, in the above embodiment, if continuous light is emitted from the laser diode 25, it is possible to perform signal measurement by a conventional general-purpose measuring instrument such as a real-time oscilloscope, sampling oscilloscope, spectrum analyzer, or the like. In this case, the photodiodes 41, 4
2. Instead of the EOS oscilloscope, a real-time oscilloscope, sampling oscilloscope, spectrum analyzer, etc. may be connected via a dedicated controller.

[0039]

As described above, in the electro-optical probe according to the first aspect, the tip member for holding the metal pin is formed so as to be detachable from the head main body, so that the metal pin needs to be replaced. If this happens, this can be easily replaced together with the tip member. As a result, unlike the conventional case, it is not necessary to replace the entire probe head when replacing the metal pin, and as a result, it is not necessary to replace an expensive electro-optical element, which is advantageous in terms of cost.

Further, in this case, when the male screw portion is provided on one of the tip member and the head body and the female screw portion is provided on the other, the tip member and the head body are provided. It can be easily attached and detached, and the invention of claim 1 can be satisfactorily realized. Further, even if the tip member is provided with a screw hole and the screw is disposed in the screw hole to fix the tip member to the head body, the same effect as that of the second aspect can be obtained. it can.

Further, by providing a buffer plate between the electro-optical element and the metal pin as in claim 4, it is possible to prevent the electro-optical element from being impacted when the tip member is attached or detached, and as a result, Therefore, the durability can be improved.

In the above invention, the photodiode and the laser diode are connected to the electro-optical sampling oscilloscope, and the laser light from the laser diode is pulsed based on the control signal from the electro-optical sampling oscilloscope. If the light is emitted as light, it is possible to perform highly accurate signal measurement in a wide band using an electro-optic sampling oscilloscope.

Further, according to the sixth aspect, continuous light is emitted from the laser diode, so that continuous output can be obtained from the photodiode. Therefore, the photodiode is connected to the real-time oscilloscope via the dedicated controller. It is also possible to connect to a conventional general-purpose measuring instrument such as the one described above to perform measurement, and the versatility is high.

[Brief description of drawings]

FIG. 1 is a vertical cross-sectional view of an electro-optical probe schematically showing an embodiment of the present invention.

FIG. 2 is a plan view of the same.

FIG. 3 is a vertical cross-sectional view of a probe head showing an example in which a buffer plate is arranged between a metal pin and an electro-optical element in the electro-optical probe shown in FIG.

FIG. 4 is a vertical cross-sectional view of the probe head showing a state in which the tip member and the head main body are fixed by means other than that shown in FIG.

5 is a vertical cross-sectional view showing an example of a case where a buffer plate is arranged between a metal pin and an electro-optical element in the probe head shown in FIG.

6 is a vertical cross-sectional view showing an example of the probe head shown in FIG. 4 in which a metal pin is divided into a base end portion and a tip end portion.

FIG. 7 is a schematic configuration diagram of an electro-optical probe schematically showing a conventional technique of the present invention.

[Explanation of symbols]

21 Electro-optic probe 22 Probe body 22a tip 22b base end 23 optical path 23a One end 23b the other end 24 probe head 25 laser diode 26 Electro-optical element 28 Reflective film 30 head body 30a Male screw part 31 Tip member 31a female screw part 32 metal pins 32a base end 32b tip

Front page continued (72) Inventor Toshiyuki Yagi 4-19-7 Kamata, Ota-ku, Tokyo Ando Electric Co., Ltd. (72) Inventor Mitsuru Shinagawa 2-3-1 Otemachi, Chiyoda-ku, Tokyo Nippon Telegraph and Telephone Corporation In-house (72) Inventor Tadao Nagatsuma 2-3-1 Otemachi, Chiyoda-ku, Tokyo Nippon Telegraph and Telephone Corporation (72) Inventor Junzo Yamada 2-3-1 Otemachi, Chiyoda-ku, Tokyo Nippon Telegraph and Telephone (56) References JP 10-268003 (JP, A) JP 8-262117 (JP, A) JP 10-90371 (JP, A) JP 6-265606 (JP, A) JP-A-6-242152 (JP, A) JP-A-5-267407 (JP, A) JP-A-59-44665 (JP, A) JP-A-7-98329 (JP, A) US Pat. US, A) International publication 89/09413 (WO, A1) (58) Fields investigated (Int.Cl. ⁷ , DB name) G01R 13/40 G01R 1/06 G01R 15/24 G01R 19/00 G01R 31/302

Claims (6)

(57) [Claims] 1. An optical path is formed inside a probe body between a base end side and a tip end side of the probe body, and a laser diode is provided at one end of the optical path on the base end side of the probe body. At the other end of the optical path on the tip end side of the probe body, an electro-optical element is placed in a state of being held by a probe head that constitutes the tip end portion of the probe body. The pin has a base end connected to the electro-optical element and a tip protruding from the probe head. Laser light emitted from the laser diode is incident on the electro-optical element through the optical path. , The incident light is reflected by the reflection film provided on the electro-optical element,
Further, the reflected light is separated and is converted into an electric signal by a photodiode, the probe head is detachably provided on the head body that holds the electro-optical element, and the head body, An electro-optic probe having a tip member that holds the metal pin. 2. The electro-optical probe according to claim 1, wherein one of the head body and the tip member is:
A male screw portion that projects toward the other side is provided, and a female screw portion that fits with the male screw portion is formed on the other side, and the male screw portion and the female screw portion are detachable. An electro-optic probe characterized by. 3. The electro-optical probe according to claim 1, wherein the tip member is provided with a screw hole, and the tip member is formed by a screw arranged in the screw hole.
An electro-optic probe fixed to the head body. 4. The electro-optical probe according to claim 1, wherein the electro-optical element and the base end of the metal pin are impacted by contact between the electro-optical element and the metal pin. An electro-optical probe, wherein the electro-optical probes are connected to each other via a buffer plate that relaxes. 5. The electro-optical probe according to claim 1, wherein the photodiode and the laser diode are
An electro-optic probe connected to an electro-optic sampling oscilloscope, wherein the laser diode emits the laser light as pulsed light based on a control signal from the electro-optic sampling oscilloscope. 6. The electro-optical probe according to claim 1, wherein the laser diode emits continuous light as the laser light.