Voltage measuring apparatus

• US 4,982,151 A
• Filed: 08/08/1989
• Issued: 01/01/1991
• Est. Priority Date: 10/05/1988
• Status: Expired due to Term

• Current Assignee: Hamamatsu Photonics KK
• Original Assignee: Hamamatsu Photonics KK
• Inventors: Tsuchiya, Yutaka, Takahashi, Hironori, Aoshima, Shinichiro
• Primary Examiner(s): Karlsen, Ernest F.
• Assistant Examiner(s): Burns, William J.
• Application Number:
  US07/390,768
• Time in Patent Office: 511 Days
• Field of Search: 324/98, 324/99 R, 324/99, 324/96, 324/77 R, 350/356, 350/374-378, 250/225
• US Class Current: 324/96
• CPC Class Codes: G01R 1/071 containing electro-optic elements
• CPC Class Codes: G01R 15/242 based on the Pockels effect, i.e. linear electro-optic effect

Abstract

A voltage measuring apparatus comprises an optical probe furnished with an electro-optic material whose refractive index is changed in accordance with a voltage developing in a given part of an object and an auxiliary electrode for terminating electric lines of force coming from the given part, a light source for producing light to be inputted to the electro-optic material, a light polarization detector for detecting a polarization state of output light from the electro-optic material, and a power source for applying a variable voltage to the auxiliary electrode. An absolute value of the voltage in the given part can be determined as a specific value of the variable voltage obtained when no change is detected in the polarization state of the output light.

Claims

1. A voltage measuring apparatus for measuring a first voltage developing in a given part of an object, comprising:

an optical prove comprising an electro-optic material for sensing said first voltage as a change in its refractive index, and an auxiliary electrode for terminating electric lines of force coming from said given part;

a light source for producing a light beam to be supplied to said electro-optic material, said light beam to be supplied having a first polarization state;

light detecting means for detecting a change between the first polarization state of said light beam to be supplied and a second polarization state of an output light beam from said electro-optic material; and

means for applying and varying a second voltage to said auxiliary electrode to provide that said light detecting means does not detect a change between the first polarization state of said light beam to be supplied and the second polarization state of the output light beam from said electro-optic material;

whereby

said second voltage is equal to an absolute voltage in said given part.

2. A voltage measuring apparatus as claimed in claim 1, wherein said auxiliary electrode is transparent and is disposed on a face of said electro-optic material which is opposed to a tip face of said electro-optic material.

3. A voltage measuring apparatus as claimed in claim 1, wherein said auxiliary electrode is disposed on a lateral side of said optical probe which is in proximity to a top face of said electro-optic material.

4. A voltage measuring apparatus as claimed in claim 1, wherein said light source is a pulse light source for producing a pulse light beam, and said light detecting means samples said second polarization state of said output light beam.

5. A voltage measuring apparatus as claimed in claim 4, further comprising delay means for adjusting timing between voltage development in said given part and light incident on said optical probe.

6. A voltage measuring apparatus as claimed in claim 1, wherein said light source is a CW light source for producing a CW light beam or a pulse light source for producing a pulse light beam, and said light detecting means is a high-speed light response detector.

7. A voltage measuring apparatus as claimed in claim 1, wherein said voltage applying means comprises a power source for producing said variable voltage, and a voltmeter for measuring said variable voltage.

8. A method employing an electro-optic material having an auxiliary electrode for measuring a first voltage developing in a given part of an object comprising the steps of:

producing a light beam to be supplied into the electro-optic material, said electro-optic material sensing said first voltage as a change in its refractive index;

detecting a change between a polarization state of said light beam to be input and a polarization state of an output light beam from said electro-optic material;

applying a second voltage of zero volts to the auxiliary electrode within close proximity of said electro-optic material;

increasing said second voltage until a change between the polarization state of said light beam to be supplied and the polarization state of the output light beam from said electro-optic material is not detected;

transmitting the final value of the increased second voltage as the detected first voltage developed in said given part.

9. The method according to claim 8 further comprising the step of pulsing said light beam to be supplied.

10. The method according to claim 9 further comprising the step of adjusting timing between voltage development in said given part and said light beam to be supplied.