High temperature electrode seal in a ring laser gyro

Details High temperature electrode seal in a ring laser gyro High temperature electrode seal in a ring laser gyro

2001-09-11

2004-03-09

Turner, Samuel A. (Department: 2877)

Optics: measuring and testing

By light interference

Rotation rate

C372S094000

Reexamination Certificate

active

06704111

ABSTRACT:

TECHNICAL FIELD
The present invention relates generally to a ring laser gyro having an anode and a cathode for creating a laser in an optical closed loop path. More specifically, the invention is a high temperature seal used to mount electrodes to the laser block of the ring laser gyro.
BACKGROUND OF THE INVENTION
Ring laser angular rate sensors, commonly referred to as ring laser gyros, are well known and in widespread use today. For example, ring laser gyros are frequently used in guidance and navigation modules on a variety of vehicles, including airplanes, unmanned rockets, and military tanks. In addition, ring laser gyros are used in down-hole drilling operations, such as for oil, for providing precise locations of a drilling bit.
A ring laser gyro includes a laser block having a plurality of interconnected passages formed within the block. The passages are arranged in a closed loop polygon shape, such as a triangle or a rectangle, and reflective surfaces are positioned at the intersection of each passage with another passage. In this manner, an optical closed loop path is created within the laser block. A lasing gas, such as helium-neon for example, is contained within the closed loop path. A pair of electrodes are mounted to the laser block in fluid conununication with lasing gas in the closed loop path. One electrode serves as a cathode, and the other electrodes serve as anodes. An electrical potential is created across the cathode and one of the anodes through the lasing gas. This electrical potential creates lasing gas, which in turn generates a laser that traverses the optical closed loop path of the laser block. An electrical potential created across the cathode and another anode creates a counter-rotating laser traversing the optical closed loop path.
An important feature of a ring laser gyro is the seal between the electrodes and the laser block The electrodes must be sealed to the block in a gastight manner to prevent the escape of the lasing gas within the gyro. Conventionally, an indium seal has been used to mount the electrodes to the laser block. A thin ring of ductile indium is compressed between the electrode and the laser block. Durable metal-to-oxygen bonds are formed between the indium and the ring laser gyro components (i.e. the laser block and the electrode) during this operation. In high temperature applications, however, the indium melts at temperatures greater than approximately 315° Fahrenheit thereby negatively impacting the performance of the ring laser gyro. Some alloys of indium have higher melting points, but they generally have lower adhesion to the laser block and electrode when forming the compression seal.
There is thus a need for an improved ring laser gyro having an electrode seal that exhibits better high temperature performance characteristics. More specifically, a ring laser gyro with a seal between the laser block and the electrodes of the ring laser gyro that can withstand high temperature applications, and that will be less sensitive to thermal effects at higher temperature is desirable. In addition, a ring laser gyro having a seal that facilitates rework of the ring laser gyro electrodes would be highly desirable as well.
SUMMARY OF THE INVENTION
The present invention is a ring laser angular rate sensor having a high temperature seal that permits the efficient replacement of the electrodes of the ring laser gyro. The ring laser gyro comprises a laser block that is formed from a material that has a relatively low coefficient of thermal expansion and that has an optical closed loop path formed within the block. The optical closed loop path contains a gas adapted to conduct an electrical potential for creating a laser within the optical closed loop path. Electrodes in fluid conununication with the gas within the closed loop path in the laser block are sealed to the laser block As part of this seal, a first washer having a relatively low coefficient of thermal expansion is sealed to the electrode. The washer electrode assembly is mounted to the laser block through an optical bond between a first surface of the washer and the laser block.


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Author: George Wallis, Title: “Field Assisted Glass Sealing”, found in the Electrocomponent Science and Technology, 1975, vol. 2, No. 1, pp. 44-53.

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