Compact optical gyro

An optical device which uses counterpropagating beams of light capable of sensing at least one environmental effect including:

• ,
• a light source which produces a first beam of light;
• means for splitting said first beam of light into at least second and third beams of light;
• a light path, said light path being capable of having the environmental effect applied thereto;
• means for directing said second and third beams of light in opposite directions along said light path to establish a counterpropagating light path for said second and third beams;
• means capable of shifting the frequency between said second and third beams of light, said means being positioned in said second and third beams of light so that one of the beams is frequency shifted prior to passing through said counterpropagating light path and the other is frequency shifted after passing through said counterpropagating light path;
• means capable of varying nonreciprocal phase shift between said second and third beams of light positioned in said second and third beams of light so that one of the beams is varied prior to passing through said counterpropagating light path and the other is varied after passing through said counterpropagating light path;
• means for recombining said second and third beams of light into a fourth beam of light after said second and third beams of light have been directed along said counterpropagating light path;
• means for detecting said fourth beam of light and producing therefrom an output indicative of phase shift induced by the environmental effect;
• means connected to said means of detecting and said means capable of varying nonreciprocal phase shift between said second and third beams of light for compensating said output of said means for detecting to restore said output of said means for detecting to the phase relationship without the environmetal effect by producing an output indicative of the degree of phase compensation and applying said output indicative of the degree of phase compensation to said means capable of shifting the frequency between said second and third beams of light, said output indicative of the degree of phase compensation also indicating the amount of environmental effect, wherein said means for directing said second and third beams of light in opposite directions along a path to establish a counterpropagating light path for said second and third beams and said means capable of shifting the frequency between said second and third beams of light include:
• an acousto-optic modulator having a front surface and a reflective back surface, said front surface being positioned to intercept said first beam of light, said acousto-optic modulator when driven generating diffracted and non-diffracted beams of different frequency which are said second and third beams of light, said back surface being tilted with respect to said front surface to reflect said second and third beams of light out of said front surface at locations different from said first beam of light into said opposite directions along the path.

An optical device which uses counterpropagating beams of light capable of sensing at least one environmental effect including:

• a light source which produces a first beam of light;
• means for splitting said first beam of light into at least second and third beams of light;
• a light path, said light path being capable of having the environmental effect applied thereto;
• means for directing said second and third beams of light in opposite directions along said light path to establish a counterpropagating light path for said second and third beams;
• means capable of shifting the frequency between said second and third beams of light, said means being positioned in said second and third beams of light so that one of the beams is frequency shifted prior to passing through said counterpropagating light path and the other is frequency shifted after passing through said counterpropagating light path;
• means capable of varying nonreciprocal phase shift between said second and third beams of light positioned in said second and third beams of light so that one of the beams is varied prior to passing through said counterpropagating light path and the other is varied after passing through said counterpropagating light path;
• means for recombining said second and third beams of light into a fourth beam of light after said second and third beams of light have been directed along said counterpropagating light path;
• means for detecting said fourth beam of light and producing therefrom an output indicative of phase shift induced by the environmental effect;
• means connected to said means of detecting and said means capable of varying nonreciprocal phase shift between said second and third beams of light for compensating said output of said means for detecting to restore said output of said means for detecting to the phase relationship without the environmental effect by producing an output indicative of the degree of phase compensation and applying said output indicative of the degree of phase compensation to said means capable of shifting the frequency between said second and third beams of light, said output indicative of the degree of phase compensation also indicating the amount of environmental effect, wherein said means for directing said second and third beams of light in opposite directions along a path to establish a counterpropagating light path for said second and third beams and said means capable of shifting the frequency between said second and third beams of light include:
• an acousto-optic modulator having;
• a first surface mis-aligned from a right angle to said first beam of light by the Bragg angle;
• a second surface aligned at a right angle to said first surface;
• a third surface aligned parallel to said second surface;
• a fourth surface parallel to said first surface;
• a first transducer mounted on said second surface;
• and
• a second transducer mounted on said third surface, said first and second transducers being alternately driven at a predetermined frequency so that said first beam emanates out of said fourth surface undiffracted as said second beam of light and a diffracted beam at a frequency alternately above and below said second beam of light by said predetermined frequency emanates out of said fourth surface as said third beam of light.

An optical device which uses counterpropagating beams of light capable of sensing at least one environmental effect including:

• a light source which produces a first beam of light;
• means for splitting said first beam of light into at least second and third beams of light;
• a light path, said light path being capable of having the environmental effect applied thereto;
• means for directing said second and third beams of light in opposite directions along said light path to establish a counterpropagating light path for said second and third beams;
• means capable of shifting the frequency between said second and third beams of light, said means being positioned in said second and third beams of light so that one of the beams is frequency shifted prior to passing through said counterpropagating light path and the other is frequency shifted after passing through said counterpropagating light path;
• means capable of varying nonreciprocal phase shift between said second and third beams of light positioned in said second and third beams of light so that one of the beams is varied prior to passing through said counterpropagating light path and the other is varied after passing through said counterpropagating light path;
• means for recombining said second and third beams of light into a fourth beam of light after said second and third beams of light have been directed along said counterpropagating light path;
• means for detecting said fourth beam of light and producing therefrom an output indicative of phase shift induced by the environmental effect;
• means connected to said means of detecting and said means capable of varying nonreciprocal phase shift between said second and third beams of light for compensating said output of said means for detecting to restore said output of said means for detecting to the phase relationship without the environmental effect by producing an output indicative of the degree of phase compensation and applying said output indicative of the degree of phase compensation to said means capable of shifting the frequency between said second and third beams of light, said output indicative of the degree of phase compensation also indicating the amount of environmental effect, wherein said light path includes:
• a length of optical fiber having first and second ends, and wherein said means for directing said second and third beams of light in opposite directions along a path to establish a counterpropagating light path for said second and third beams and said means capable of shifting the frequency between said second and third beams of light include:
• a fiber spatial filter through which said first beam of light passes;
• and
• an acousto-optic modulator, said acousto-optic modulator having:
• a front surface;
• and
• a back surface, said front surface being positioned to intercept said first beam of light out of said fiber spatial filter, said acousto-optic modulator when driven generating diffracted and non-diffracted beams of different frequency which are said second and third beams of light which pass out of said back surface to said first and second ends of said optical fiber respectively, after passing through said optical fiber where information is impressed thereon, said second and third beams of light pass out of said second and first ends respectively to said acousto-optic modulator where they are diffracted and a portion of each is passed back to said fiber spatial filter.

An optical device which uses counterpropagating beams of light capable of sensing at least one environmental effect including:

• a light source which produces a first beam of light;
• means for splitting said first beam of light into at least second and third beams of light;
• a light path, said light path being capable of having the environmental effect applied thereto;
• means for directing said second and third beams of light in opposite directions along said light path to establish a counterpropagating light path for said second and third beams;
• means capable of shifting the frequency between said second and third beams of light, said means being positioned in said second and third beams of light so that one of the beams is fredquency shifted prior to passing through said counterpropagating light path and the other is frequency shifted after passing through said counterpropagating light path;
• means capable of varying nonreciprocal phase shift between said second and third beams of light positioned in said second and third beams of light so that one of the beams is varied prior to passing through said counterpropagating light path and the other is varied after passing through said counterpropagating light path;
• means recombining said second and third beams of light into a fourth beam of light after said second and third beams of light have been directed along said counterpropagating light path;
• means for detecting said fourth beam of light and producing therefrom an output indicative of phase shift induced by the environmental effect;
• and
• means connected to said means of detecting and said means capable of varying nonreciprocal phase shift between said second and third beams of light for compensating said output of said means for detecting to restore said output of said means for detecting to the phase relationship without the environmental effect by producing an output indicative of the degree of phase compensation and applying said output indicative of the degree of phase compensation to said means capable of shifting the frequency between said second and third beams of light, said output indicative of the degree of phase compensation also indicating the amount of environmental effect, said means capable of varying nonreciprocal phase shift between said second and third beams of light including:
• a polarizing beamsplitter cube having first, second, and third surfaces, said second beam of light being directed through said first surface and out of said second surface thereof with a predetermined polarization state and said third beam of light being directed through said third surface and out of said second surface thereof with a predetermined polarization state opposite from said predetermined polarization state of said second beam of light;
• a quarter-wave plate positioned so that said second and third beams out of said second surface pass therethrough;
• and
• a variable etalon positioned to phase shift said second and third beams out of said quarter-wave plate and pass said phase shifted second and third beams back through said quarter-wave plate and said third and first surfaces of said polarizing beamsplitter cube respectively.

An optical device which uses counterpropagating beams of light capable of sensing at least one environmental effect including:

• a light source which produces a first beam of light;
• means for splitting said first beam of light into at least second and third beams of light;
• a light path, said light path being capable of having the environmental effect applied thereto;
• means for directing said second and third beams of light in opposite directions along said light path to establish a counterpropagating light path for said second and third beams;
• means capable of shifting the frequency between said second and third beams of light, said means being positioned in said second and third beams of light so that one of the beams is frequency shifted prior to passing through said counterpropagating light path and the other is frequency shifted after passing through said counterpropagating light path, said means capable of shifting the frequency between said second and third beams of light including:
• an acousto-optic modulator, said acousto-optic modulator having:
• a modulator element with a first side, a second side at a right angle to said first side, a third side at a right angle different by the Bragg angle to said first side, and a fourth side, said first side being positioned in said first beam of light at a right angle different by the Bragg angle;
• a first transducer mounted to said second side adjacent said first side being driven at a predetermined carrier frequency;
• and
• a second transducer mounted to said third side spaced from said first side being driven at said predetermined carrier frequency different by the shift frequency, whereby beams at the frequency of said first beam, at the frequency of said first beam plus said shift frequency and at the frequency of said first beam minus said shift frequency emanate out of said fourth surface in different predetermined directions;
• means capable of varying nonreciprocal phase shift between said second and third beams of light positioned in said second and third beams of light so that one of the beams is varied prior to passing through said counterpropagating light path and the other is varied after passing through said counterpropagating light path;
• means for recombining said second and third beams of light into a fourth beam of light after said second and third beams of light have been directed along said counterpropagating light path;
• means for detecting said fourth beam of light and producing therefrom an output indicative of phase shift induced by the environmental effect;
• and
• means connected to said means of detecting and said means capable of varying nonreciprocal phase shift between said second and third beams of light for compensating said output of said means for detecting to restore said output of said means for detecting to the phase relationship without the environmental effect by producing an output indicative of the degree of phase compensation and applying said output indicative of the degree of phase compensation to said means capable of shifting the frequency between said second and third beams of light, said output indicative of the degree of phase compensation also indicating the amount of environmental effect.

An optical device which uses counterpropagating beams of light capable of sensing at least one environmental effect including:

• a light source which produces a first beam of light;
• means for splitting said first beam of light into at least second and third beams of light;
• a light path, said light path being capable of having the environmental effect applied thereto;
• means for directing said second and third beams of light in opposite directions along said light path to establish a counterpropagating light path for said second and third beams;
• means capable of shifting the frequency between said second and third beams of light, said means being positioned in said second and third beams of light so that one of the beams is frequency shifted prior to passing through said counterpropagating light path and the other is frequency shifted after passing through said counterpropagating light path, said means capable of shifting the frequency between said second and third beams of light including:
• an acousto-optic modulator, said acousto-optic modulator having:
• a trapezoidal modulator element with a first side, a second side at a right angle different by the Bragg angle to said first side, a third side at a right angle different by the Bragg angle to said first side, and a fourth side parallel to said first side, said first side being positioned in said first beam of light at a right angle thereto;
• a first transducer mounted to said second side adjacent said first side being driven at a predetermined carrier frequency;
• and
• a second transducer mounted to said third side spaced from said first side being driven at said predetermined carrier frequency different by the shift frequency, whereby a beam at the frequency of said first beam emanates out of said fourth surface at a right angle thereto, a beam at the frequency of said first beam different by said predetermined carrier frequency emanates out of said fourth surface at a right angle different by twice the Bragg angle, and a beam at the frequency of said first beam different by said frequency that said second transducer is driven emanates out of said fourth surface at a right angle different by twice the Bragg angle;
• means capable of varying nonreciprocal phase shift between said second and third beams of light positioned in said second and third beams of light so that one of the beams is varied prior to passing through said counterpropagating light path and the other is varied after passing through said counterpropagating light path;
• means for recombining said second and third beams of light into a fourth beam of light after said second and third beams of light have been directed along said counterpropagating light path;
• means for detecting said fourth beam of light and producing therefrom an output indicative of phase shift induced by environmental effect;
• and
• means connected to said means of detecting and said means capable of varying nonreciprocal phase shift between said second and third beams of light for compensating said output of said means for detecting to restore said output of said means for detecting to the phase relationship without the environmental effect by producing an output indicative of the degree of phase compensation and applying said output indicative of the degree of phase compensation to said means capable of shifting the frequency between said second and third beams of light, said output indicative of the degree of phase compensation also indicating the amount of environmental effect.

An optical device which uses counterpropagating beams of light capable of sensing at least one environmental effect including:

• a light source which produces a first beam of light;
• means for splitting said first beam of light into at least second and third beams of light;
• a light path, said light path being capable of having the environmental effect applied thereto;
• means for directing said second and third beams of light in opposite directions along said light path to establish a counterpropagating light path for said second and third beams;
• means capable of shifting the frequency between said second and third beams of light, said means being positioned in said second and third beams of light so that one of the beams is frequency shifted prior to passing through said counterpropagating light path and the other is frequency shifted after passing through said counterpropagating light path, said means capable of shifting the frequency between said second and third beams of light including:
• an acousto-optic modulator, said acousto-optic modulator having:
• a modulator element with a first side, a second side at a right angle to said first side, a third side at a right angle to said first side, and a fourth side parallel to said first side, said first side being positioned in said first beam of light;
• a first transducer mounted to said second side being driven at a predetermined carrier frequency;
• and
• a second transducer mounted to said third side being driven at said predetermined carrier frequency different by the shift frequency, whereby a beam at the frequency of said first beam emanates out of said fourth surface parallel to said first beam, a beam at the frequency of said first beam different by aid predetermined carrier frequency emanates out of said fourth surface at the Bragg angle from said first beam, and a beam at the frequency of said first beam different by said frequency that said second transducer is driven emanates out of said fourth surfaces at the Bragg angle from said first beam;
• means capable of varying nonreciprocal phase shift between said second and third beams of light positioned in said second and third beams of light so that one of the beams is varied prior to passing through said counterpropagating light path and the other is varied after passing through said counterpropagating light path;
• means for recombining said second and third beams of light into a fourth beam of light after said second and third beams of light have been directed along said counterpropagating light path;
• means for detecting said fourth beam of light and producing therefrom an output indicative of phase shift induced by the environmental effect;
• and
• means connected to said means of detecting and said means capable of varying nonreciprocal phase shift between said second and third beams of light for compensating said output of said means for detecting to restore said output of said means for detecting to the phase relationship without the environmental effect by producing an output indicative of the degree of phase compensation and applying said output indicative of the degree of phase compensation to said means capable of shifting the frequency between said second and third beams of light, said output indicative of the degree of phase compensation also indicating the amount of environmental effect.

An optical device which uses counterpropagating beams of light capable of sensing at least one environmental effect including:

• a light source which produces a first beam of light;
• means for splitting said first beam of light into at least second and third beams of light;
• a light path, said light path being capable of having the environmental effect applied thereto;
• means for directing said second and third beams of light in opposite directions along said light path to establish a counterpropagating light path for said second and third beams;
• means capable of shifting the frequency between said second and third beams of light, said means being positioned in said second and third beams of light so that one of the beams is frequency shifted prior to passing through said counterpropagating light path and the other is frequency shifted after passing through said counterpropagating light path, said means capable of shifting the frequency between said second and third beams of light including:
• an acousto-optic modulator, said acousto-optic modulator having:
• a modulator element with a first side, a second side at a right angle to said first side, a third side at a right angle to said first side, and a fourth side parallel to said first side, said first side being positioned in said first beam of light;
• a first transducer mounted to said second side being driven at a predetermined carrier frequency;
• and
• a second transducer mounted to said third side being driven at said predetermined carrier frequency different by the shift frequency, whereby a first modulator output beam at the frequency of said first beam, a second modulator output beam at the frequency of said first beam different by said predetermined carrier frequency, and a third modulator output beam at the frequency of said first beam different by said frequency that said second transducer is driven emanate out of said fourth surface at predetermined angles from said first beam;
• means capable of varying nonreciprocal phase shift between said second and third beams of light positioned in said second and third beams of light so that one of the beams is varied prior to passing through said counterpropagating light path and the other is varied after passing through said counterpropagating light path;
• means for recombining said second and third beams of light into a fourth beam of light after said second and third beams of light have been directed along said counterpropagating light path;
• means for detecting said fourth beam of light and producing therefrom an output indicative of phase shift induced by the environmental effect;
• and
• means connected to said means of detecting and said means capable of varying nonreciprocal phase shift between said second and third beams of light for compensating said output of said means for detecting to restore said output of said means for detecting to the phase relationship without the environmental effect by producing an output indicative of the degree of phase compensation and applying said output indicative of the degree of phase compensation to said means capable of shifting the frequency between said second and third beams of light, said output indicative of the degree of phase compensation also indicating the amount of environmental effect.

An optical device which uses counterpropagating beams of light capable of sensing at least one environmental effect including:

• a light source which produces a first beam of light;
• means for splitting said first beam of light into at least second and third beams of light;
• a light path, said light path being capable of having the environmental effect applied thereto;
• means for directing said second and third beams of light in opposite directions along said light path to establish a counterpropagating light path for said second and third beams;
• means capable of shifting the frequency between said second and third beams of light, sand means being positioned in said second and third beams of light so that one of the beams is frequency shifted prior to passing through said counterpropagating light path and the other is frequency shifted after passing through said counterpropagating light path, said means capable of shifting the frequency between said second and third beams of light including:
• an acousto-optic modulator, said acousto-optic modulator having:
• a modulator element with a first side, a second side at a right angle different by the Bragg angle to said first side, a third side at a right angle different by five times the Bragg angle to said first side, and a fourth reflective side different by three times the Bragg angle to said first side, said first side being positioned at a right angle to said first beam of light;
• a first transducer mounted to said second side being driven at a predetermined carrier frequency;
• and
• a second transducer mounted to said third side being driven at said predetermined carrier frequency different by the shift frequency, whereby a first modulator output beam at the frequency of said first beam, a second modulator output beam at the frequency of said first beam different by said predetermined carrier frequency, and a third modulator output beam at the frequency of said first beam different by said frequency that said second transducer is driven emanate out of said first surface at predetermined angles from said first beam;
• means capable of varying nonreciprocal phase shift between said second and third beams of light positioned in said second and third beams of light so that one of the beams is varied prior to passing through said counterpropagating light path and the other is varied after passing through said counterpropagating light path;
• means for recombining said second and third beams of light into a fourth beam of light after said second and third beams of light have been directed along said counterpropagating light path;
• means for detecting said fourth beam of light and producing therefrom an output indicative of phase shift induced by the enviromental effect;
• and
• means connected to said means of detecting and said means capable of varying nonreciprocal phase shift between said second and third beams of light for compensating said output of said means for detecting to restore said output of said means for detecting to the phase relationship without the environmental effect by producing an output indicative of the degree of phase compensation and applying said output indicative of the degree of phase compensation to said means capable of shifting the frequency between said second and third beams of light, said output indicative of the degree of phase compensation also indicating the amount of environmental effect.