Coherent laser radar device
First Claim
1. A coherent laser radar device comprising:
- a local light source that oscillates at a single frequency;
a pulsed laser that oscillates at a frequency which is identical with or close to the single frequency of said local light source;
a transmission/reception optical system that irradiates a pulsed laser beam from said pulsed laser toward a target as a transmission light and receives a scattered light from the target as a reception light;
a light coupling means that couples the output light from said local light source and said reception light;
a photo detecting portion that conducts light coherent detection on the light coupled by said light coupling means; and
a signal processing device that calculates a speed and a distance of a target in accordance with an output from said photo detecting portion, characterized in that said photo detecting portion comprises;
a photo detecting element that conducts the light coherent detection;
a microwave switch that changes over a propagation path of an output from said photo detecting element;
a microwave amplifier; and
a switch control means that changes over said microwave switch so as to transmit a signal before a reference time to said signal processing device as a monitor signal and transmit a signal after the reference time to said signal processing device as a reception signal with said reference time being a time at which the pulse light from said pulsed laser has completely passed through said transmission/reception optical system.
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Accused Products
Abstract
An object of the invention is to obtain a coherent laser radar device that provides one system of a photo detector and eliminates a blind zone, including a pulsed laser that oscillates at a frequency which is identical with or close to an output light of a local light source as a single frequency; a transmission/reception optical system that irradiates a pulsed laser beam from the pulsed laser toward a target as a transmission light and receives a scattered light from the target as a reception light; a light coupling means that couples the output light from the local light source and the reception light; a photo detecting portion that conducts light coherent detection on a coupled light; and a signal processing device that calculates a speed and a distance of a target in accordance with an output of the detection, in which the photo detecting portion comprises: a photo detecting element that conducts the light coherent detection; a microwave switch that changes over a propagation path of an output from the photo detecting element; a microwave amplifier; and a switch control means that changes over the microwave switch so as to transmit a signal before a reference time as a monitor signal and transmit a signal after the reference time as a reception signal with a time at which the pulse light from the pulsed laser has completely passed through the transmission/reception optical system as the reference time.
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Citations
24 Claims
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1. A coherent laser radar device comprising:
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a local light source that oscillates at a single frequency;
a pulsed laser that oscillates at a frequency which is identical with or close to the single frequency of said local light source;
a transmission/reception optical system that irradiates a pulsed laser beam from said pulsed laser toward a target as a transmission light and receives a scattered light from the target as a reception light;
a light coupling means that couples the output light from said local light source and said reception light;
a photo detecting portion that conducts light coherent detection on the light coupled by said light coupling means; and
a signal processing device that calculates a speed and a distance of a target in accordance with an output from said photo detecting portion, characterized in that said photo detecting portion comprises;
a photo detecting element that conducts the light coherent detection;
a microwave switch that changes over a propagation path of an output from said photo detecting element;
a microwave amplifier; and
a switch control means that changes over said microwave switch so as to transmit a signal before a reference time to said signal processing device as a monitor signal and transmit a signal after the reference time to said signal processing device as a reception signal with said reference time being a time at which the pulse light from said pulsed laser has completely passed through said transmission/reception optical system. - View Dependent Claims (2, 3, 4)
said pulsed laser includes an adjusting mechanism that adjusts a cavity length;
said device further comprises a control circuit that controls said adjusting mechanism; and
said control circuit outputs to said adjusting mechanism a control signal that adjusts the cavity length of said pulsed laser on the basis of an error signal from said signal processing device based on a frequency difference between the laser pulse and the local light.
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3. A coherent laser radar device according to claim 1, characterized in that:
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said microwave amplifier is made up of a pre-amplifier that amplifies a signal from said photo detecting element and a post-amplifier that amplifies an output of the pre-amplifier; and
said microwave switch is disposed between said pre-amplifier and said post-amplifier, outputs a signal that has been amplified by said pre-amplifier as a monitor signal and outputs a signal that has passed through said post-amplifier as a reception signal.
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4. A coherent laser radar device according to claim 1, characterized in that:
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said microwave amplifier is made up of a pre-amplifier that amplifies a signal from said photo detecting element and a post-amplifier that amplifies an output of the pre-amplifier; and
said microwave switch is disposed between said photo detecting element and said pre-amplifier, outputs a signal from said photo detecting element as a monitor signal and outputs a signal that has passed through said post-amplifier as a reception signal.
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5. A coherent laser radar device comprising:
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a local light source that oscillates at a single frequency;
a pulsed laser that oscillates at a frequency which is identical with or close to the single frequency of said local light source;
a transmission/reception optical system that irradiates a pulsed laser beam from said pulsed laser toward a target as a transmission light and receives a scattered light from the target as a reception light;
a coupling means that couples said reception light and an internal reflection light to an optical path, the internal reflection light comprising a part of the pulsed laser beam from said pulsed laser used for generating a monitor signal;
a photo detecting portion that conducts light coherent detection on the light coupled to the optical path by said light coupling means; and
a signal processing device that calculates a speed and a distance of a target in accordance with an output from said photo detecting portion, characterized in that said photo detecting portion comprises;
a photo-detecting element that conducts the light coherent detection;
a microwave amplifying portion that amplifies an output signal from said photo detecting element; and
a gain control means that controls the gain of said microwave amplifying portion so that an amplitude of the output signal from said microwave amplifying portion does not exceed a given threshold value. - View Dependent Claims (6, 7, 8)
said pulsed laser includes an adjusting mechanism that adjusts a cavity length;
said device further comprises a control circuit that controls said adjusting mechanism; and
said control circuit outputs to said adjusting mechanism a control signal that adjusts the cavity length of said pulsed laser on the basis of an error signal from said signal processing device based on a frequency difference between the laser pulse and the local light.
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7. A coherent laser radar device according to claim 5, characterized in that:
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said microwave amplifier is made up of a pre-amplifier that amplifies a signal from said photo detecting element and a gain control amplifier that amplifies an output of the pre-amplifier; and
said gain control means controls the gain of said gain control amplifier.
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8. A coherent laser radar device according to claim 5, characterized in that:
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said microwave amplifier is made up of a pre-amplifier that amplifies a signal from said photo detecting element and a post-amplifier that amplifies an output of the pre-amplifier; and
said gain control means comprises a microwave variable attenuator disposed between said pre-amplifier and said post-amplifier, and an attenuation control circuit that controls the attenuation of said microwave variable attenuator.
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9. A coherent laser radar device characterized by comprising:
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a local light source that oscillates at a single frequency;
a pulsed laser that oscillates at a frequency which is identical with or close to the single frequency of said local light source;
a transmission/reception optical system that irradiates a pulsed laser beam from said pulsed laser toward a target as a transmission light and receives a scattered light from the target as a reception light;
a coupling means that couples said reception light and an internal reflection light to an optical path, the internal reflection light comprising a part of the pulsed laser beam from said pulsed laser used for generating a monitor signal;
a photo detecting portion that conducts light coherent detection on the light coupled to the optical path by said optical coupler; and
a signal processing device that detects a speed and a distance of a target in accordance with an output from said photo detecting portion;
a light variable attenuator disposed between said transmission/reception optical system and said photo detecting portion; and
a control means that controls the attenuation of said light variable attenuator in such a manner that an amplitude of the output from said photo detecting portion does not exceed a given threshold value. - View Dependent Claims (10)
said pulsed laser includes an adjusting mechanism that adjusts a cavity length;
said device further comprises a control circuit that controls said adjusting mechanism; and
said control circuit outputs to said adjusting mechanism a control signal that adjusts the cavity length of said pulsed laser on the basis of an error signal from said signal processing device based on a frequency difference between the laser pulse and the local light.
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11. An apparatus implemented in a laser radar device, the laser radar device being configured to transmit a pulsed laser beam toward a target and process scattered light received from the target in a signal processing unit, the apparatus comprising:
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light coupling means for coupling the output light of a light source with the received scattered light, the light source being used to generate the pulsed laser beam;
photo-detecting means for generating a signal by performing coherent detection on the light coupled by the light coupling means;
outputting means for outputting the signal generated by the photo-detecting means to the signal processing unit as a monitor signal before a reference time, and for outputting an amplified version of the signal generated by the photo-detecting means to the signal processing unit as a reception signal after the reference time, wherein the reception signal is used by the signal processing unit to determine at least one of a speed and direction of the target, and the reference time corresponds to a time at which internal reflection signals of the laser radar device are diminished. - View Dependent Claims (12, 13, 14, 15, 16, 17, 18, 19)
a photo-detecting element that performs the coherent detection; - and
a pre-amplifier operable to generate a first amplified signal by amplifying an output of the photo-detecting element.
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14. The apparatus of claim 13, wherein
the photo-detecting means further include a post-amplifier operable to generate a second amplified signal by amplifying the first amplified signal, and the outputting means includes a microwave switch disposed between the preamplifier and the post amplifier, the microwave switch being operable to: -
direct the first amplified signal to the signal processing unit as the monitoring signal before the reference time; and
direct the first amplified signal to the post-amplifier after the reference time, thereby allowing the second amplified signal being output to the signal processing unit as the reception signal.
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15. The apparatus of claim 11, wherein the outputting means include,
a microwave amplifier operably connected to the photo-detecting means, and gain control means for controlling a gain of a signal output by the microwave amplifier. -
16. The apparatus of claim 15, wherein the photo-detecting means include,
a photo-detecting element that performs the coherent detection; - and
a pre-amplifier configured to generate an amplified signal by amplifying an output of the photo-detecting element, the amplified signal being sent to the outputting means.
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17. The apparatus of claim 16, wherein
the microwave amplifier is a gain control amplifier operably connected to receive the amplified signal output by the pre-amplifier, an output of the microwave amplifier further being directed to the signal processing unit, and the gain control means controls a gain of the gain control amplifier to increase after the reference time. -
18. The apparatus of claim 16, wherein
the gain control means is a microwave variable attenuator operably connected to receive the amplified signal output by the pre-amplifier, the microwave variable attenuator being controlled to attenuate the received amplified signal before the reference time, and the microwave amplifier is a post amplifier operably connected to receive an output of the microwave variable attenuator, an output of the post amplifier being directed to the signal processing unit. -
19. The apparatus of claim 11, further comprising a light variable attenuator operably connected to transfer the received scattered light to the photo-detecting means, light variable attenuator being controlled to attenuate the received scattered light to a given threshold before the reference time.
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20. A method in a laser radar device, the laser radar device being configured to transmit a pulsed laser beam toward a target and process scattered light received from the target in a signal processing unit, the method comprising:
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coupling the output light of a light source with the received scattered light, the light source being used to generate the pulsed laser beam;
generating a first signal by performing coherent detection on the coupled light to generate a first signal;
outputting, before a reference time, the first signal to the signal processing unit as a monitor signal; and
outputting, after the reference time, a second signal to the signal processing unit as a reception signal, the second signal being an amplified version of the first signal, wherein the reception signal is used by the signal processing unit to determine at least one of a speed and direction of the target, and the reference time corresponds to a time at which internal reflection signals of the laser radar device are diminished. - View Dependent Claims (21, 22, 23, 24)
utilizing a pre-amplifier to amplify a signal generated by the coherent detection;
utilizing a post-amplifier to amplify an output of the pre-amplifier; and
utilizing a microwave switch to perform the output steps, the microwave switch being configured to direct the output of the pre-amplifier to the signal processing unit before the reference time, and to direct an output of the post-amplifier to the signal processing unit after the reference time.
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22. The method of claim 20, wherein
the outputting steps are performed by a gain control amplifier configured to receive a signal generated as a result of the coherent detection, and the method further comprises: controlling a gain of the gain control amplifier to increase after the reference time.
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23. The method of claim 20, further comprising:
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utilizing a microwave variable attenuator to attenuate a signal generated as a result of the coherent detection to a given threshold before the reference time, wherein the outputting steps are performed by a microwave amplifier configured to amplify an output of the microwave variable attenuator.
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24. The method of claim 20, further comprising:
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utilizing a light variable attenuator to attenuate the received scattered light to a given threshold before the reference time, wherein the coupling step couples an output of the light variable attenuator to the output light of the light source.
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Specification