Optics: measuring and testing – By light interference – Rotation rate
Reexamination Certificate
1999-10-18
2001-10-16
Turner, Samuel A. (Department: 2877)
Optics: measuring and testing
By light interference
Rotation rate
Reexamination Certificate
active
06304329
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to gyros. More particularly, it relates to an optical gyro whose detection range for angular velocities is wide. Further, it relates to a semiconductor device which has a laser diode of a ring resonator type.
2. Related Background Art
Heretofore, a mechanical gyro having a rotor or a vibrator, and an optical gyro have been known as gyros each of which is used for detecting the angular velocity of a moving object. In particular, the optical gyro is capable of instantaneous start and has a wide dynamic range, and it is therefore innovating in the field of gyro technology. Such optical gyros include a laser gyro of ring resonator type, an optical fiber gyro, a gyro of passive ring resonator type, etc. Among them, a ring resonator type laser gyro employing a gas laser was begun to be developed earliest, and it has already been put to practical use for aircraft etc. Recently, a ring resonator type laser gyro of small size and high precision has also been proposed, and one disclosed in the official gazette of Japanese Patent Application Laid-open No. 5-288556 is mentioned as an example. With such an optical gyro, a semiconductor ring resonator type laser is formed on a single substrate, clockwise and counterclockwise lights outputted from a ring waveguide are detected by a single photodetector outside a ring resonator, and the beat signal of the lights is detected, thereby to detect an angular velocity.
FIG. 15
of the accompanying drawings is a top plan view of the ring resonator type laser gyro contained in the official gazette of Japanese Patent Application Laid-open No. 5-288556. Numeral
110
designates a semiconductor substrate, numeral
111
a gain waveguide, numeral
112
reflective surfaces, numerals
113
and
114
output surfaces, numerals
118
and
119
lights delivered from the respective output surfaces
113
and
114
, numeral
117
a photodetector, and numerals
122
and
123
electrodes. In case of the gyro shown in
FIG. 15
, lasing lights are generated in the gain waveguide
111
having the reflective surfaces
112
, by injecting a current. The wavelengths of the clockwise light
115
and the counterclockwise light
116
differ in accordance with an angular velocity, and the two output lights
118
and
119
(corresponding to the clockwise and counterclockwise lights
115
and
116
, respectively) interfere on the photodetector
117
. Thus, the angular velocity is outputted as a voltage change from the electrode
123
.
With the prior-art example, however, the size of the laser gyro becomes large for the reason that a beat signal is detected by deriving the clockwise light and counterclockwise light which travel within the ring waveguide, and causing the lights to interfere on the photodetector. Further, a gyro of higher detection sensitivity or wider detection range for angular velocities has been requested.
SUMMARY OF THE INVENTION
The present invention has for its object to provide a gyro which has a wide detection range for angular velocities.
Another object of the present invention is to provide a gyro which has a high reliability for angular velocity detection, and which can be reduced in size.
According to the present invention, in a gyro which has a ring resonator type laser diode, and which detects a beat signal attendant on rotation, a gyro is characterized in that plural laser diodes are provided on an identical substrate.
Further, a gyro according to the present invention is characterized in that active layers of the laser diodes are arranged separately from one another.
Further, the present invention is characterized in that the sizes of the plurality of laser diodes comprises 2 sizes or more; and that the plurality of compositions of the active layers comprised in the laser diodes consists of two or more sorts of composition.
A gyro according to the present invention is characterized in that the plurality of laser diodes are formed on an identical surface of the identical substrate.
Also, the present invention is characterized in that the beat signal is detected as a change in a voltage developing across each of the laser diodes, a change in a current flowing through each laser diode, or a change in the impedance of each laser diode. More concretely speaking, the beat signal is detected as a change of frequency in the voltage, a change of frequency in the current flowing, or a change of frequency in the impedance.
A semiconductor device according to the present invention is characterized in that plural ring resonator type laser diodes, each of which undergoes a voltage change across predetermined terminals in attendance on the magnitude of an applied angular velocity when subjected to constant-current drive, are disposed in a single frame.
Also, a semiconductor device according to the present invention is characterized in that plural ring resonator type laser diodes, each of which undergoes a change in a driving current in attendance on the magnitude of an applied angular velocity when subjected to constant-voltage drive, are disposed in a single frame.
Further, a semiconductor device according to the present invention is characterized in that plural ring resonator type laser diodes, each of which undergoes a voltage change across predetermined terminals in attendance on the magnitude of an applied angular velocity when subjected to constant-current drive, are disposed on a single substrate.
Besides, a semiconductor device according to the present invention is characterized in that plural ring resonator type laser diodes, each of which undergoes a change in a driving current in attendance on the magnitude of an applied angular velocity when subjected to constant-voltage drive, are disposed on a single substrate.
With the gyro in which the plurality of ring resonator type laser diodes are disposed on the single substrate as in the present invention, the angular-velocity detection sensitivities of the respective laser diodes can be made different, and hence, an optical gyro whose detection range for angular velocities is wider than in the prior art can be provided.
REFERENCES:
patent: 4327962 (1982-05-01), Redman
patent: 4431308 (1984-02-01), Mitsuhashi et al.
patent: 4913548 (1990-04-01), Vick
patent: 62-39836 (1987-08-01), None
patent: 4-174317 (1992-06-01), None
patent: 5-288556 (1993-11-01), None
patent: 6-38529 (1994-05-01), None
Nitta Jun
Numai Takahiro
Canon Kabushiki Kaisha
Fitzpatrick ,Cella, Harper & Scinto
Turner Samuel A.
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