Optics: measuring and testing – By light interference – Rotation rate
Reexamination Certificate
1999-10-18
2001-10-02
Turner, Samuel A. (Department: 2877)
Optics: measuring and testing
By light interference
Rotation rate
Reexamination Certificate
active
06297883
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a gas laser, which is in particular a ring resonator type gas laser. The present invention also relates to a gyro comprising a gas laser and a method of operating such a gyro. More particularly, the present invention relates to an optical gyro adapted to reduce the coupling loss generated when laser beams are incident upon a photodetector and the noise generated by the reflected beams reentering the laser from an external point of reflection as well as to a method of operating such an optical gyro.
2. Related Background Art
Mechanical gyros comprising a rotor and a vibrator as well as optical gyros adapted to detect the angular velocity of a moving object are known. Particularly, optical gyros are regarded as real innovation because they can start to operate instantaneously and provide a wide dynamic range. Optical gyros include ring resonator type laser gyros, optical fiber gyros and passive type ring resonator gyros, of which ring resonator type raser gyros comprising a gas laser were developed most early and have been used in aeronautic applications and other applications. Recently, small, high precision, ring resonator type laser gyros have been proposed and Japanese Patent Application Laid-Open No. 5-288556 described such a gyro.
However, known ring resonator type laser gyros are so designed that a laser beam propagating clockwise and another laser beam propagating counterclockwise are once emitted therefrom to the outside and received by a photodetector, which detects their optical beat and transforms it into an electric beat as a signal. This means that a coupling loss arises when the laser beams enter the photodetector. Additionally, known ring resonator type laser gyros need an optical isolator in order to avoid the noise generated by the beams reflected from an external point of reflection to the laser.
Particularly, since gas lasers are bulky and costly and consume driving electric power to a large extent, there is a strong demand for gyros comprising gas lasers that can be realized with a reduced number of components and hence at low cost and little power consumption.
SUMMARY OF THE INVENTION
Therefore, it is an object of the present invention to provide a gyro that is totally or almost totally free from the problem of coupling loss and that of noise due to reflected beams as well as a method of operating it.
According to the invention, the above object is achieved by providing a gyro comprising a ring resonator type gas laser with laser beams propagating circuitally in opposite directions relative to each other and a terminal for detecting a beat signal.
According to a first aspect of the invention, there is provided a gyro comprising a ring resonator type gas laser with laser beams propagating circuitally in opposite directions relative to each other, the gyro being adapted to detect a beat signal.
Preferably, the beat signal is detected as a change in the electric current flowing through, the voltage applied to, or the impedance of the ring resonator type laser.
Alternatively, the beat signal is detected as a frequency change of the electric current flowing through, the voltage applied to, or the impedance of the ring resonator type laser.
Preferably, the beat signal is taken out from the discharging electrodes of the ring resonator type gas laser.
According to a second aspect of the invention, there is provided a gyro comprising a ring resonator type gas laser with laser beams propagating circuitally in opposite directions relative to each other and a beat signal detecting meaps.
Preferably, the beatsignal detecting means includes a voltage detection circuit, an electric current detection circuit or an impedance detection circuit.
Alternatively, the beat signal detecting means includes a frequency/voltage converter.
Preferably, the electric current or the voltage for driving the ring resonator type gas laser is modulated in a frequency band, which is different from that of the frequency of the beat signal.
Alternatively, the beat signal is detected synchronously with a vibration, which is applied to the laser and has a frequency different from that of the beat signal.
According to a third aspect of the invention, there is provided a method of operating a gyro comprising a ring resonator type gas laser with laser beams propagating circuitally in opposite directions relative to each other and a terminal for detecting the beat signal produced therefrom as a change in electric current, voltage or impedance, the change in the electric current flowing through, the voltage applied to or the impedance being used as signal for determining the angular velocity of the ring resonator type laser.
REFERENCES:
patent: 3390606 (1968-07-01), Podgorski
patent: 4431308 (1984-02-01), Mitsuhashi et al.
patent: 4913548 (1990-04-01), Vick
patent: 60-148185 (1985-08-01), None
patent: 62-39836 (1987-05-01), None
patent: 4-174317 (1992-06-01), None
patent: 5-288556 (1993-11-01), None
patent: 6-38529 (1994-05-01), None
patent: 6-140364 (1994-05-01), None
patent: 7-131123 (1995-05-01), None
patent: 7-146150 (1995-06-01), None
patent: 8-018166 (1996-01-01), None
patent: 8-125251 (1996-05-01), None
Canon Kabushiki Kaisha
Fitzpatrick ,Cella, Harper & Scinto
Turner Samuel A.
LandOfFree
Ring laser gas gyro with beat signal detection from current,... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Ring laser gas gyro with beat signal detection from current,..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Ring laser gas gyro with beat signal detection from current,... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2575859