Multi-point vibration measurement system

Abstract

In a multi-point vibration measurement system, high-precision multi-point vibration measurement is performed without the risk of the stability of the optical path lengths of the two optical waves, the reference light and the measurement light, affecting the measurement value. [Solution] By providing an optical path length variation compensation optical system 11 in one or more projection optical systems 40 equipped with multiple single-point irradiation heads 4 that irradiate the measurement surface 5 of the object to be measured with demultiplexed measurement light, at least one frequency component of the demultiplexed measurement light obtained by demultiplexing each frequency component of the measurement light in the optical demultiplexing optical system is used as a demultiplexed measurement reference light for optical path length variation compensation, and the compensation optical path length including at least one channel of optical path length variation compensation optical path is measured, and based on the measurement result, the variation in the demultiplexed measurement light for each frequency component and the optical path length of each of the multiple channels of measurement optical transmission paths 134 through which the demultiplexed measurement light passes is corrected.

Claims

[Claim 1] A light source that outputs coherent measurement light and reference light, having a spectrum with multiple modes in the shape of an optical comb at predetermined frequency intervals, An interference optical system receives measurement light and reference light output from the above light source, as well as measurement reflected light that is returned when the measurement light irradiated onto the measurement surface of the object to be measured is reflected by the measurement surface, and outputs measurement interference light by interfering the above reference light and the above measurement reflected light. The optical optical splitter and multiplexer optical system receives the measurement light output from the above light source via the above interference optical system, decomposes the frequency components contained in the measurement light, and outputs decomposed measurement light for each frequency component, receives the decomposed measurement reflected light for each frequency component that is reflected back by the measurement surface after the decomposed measurement light for each frequency component is irradiated onto multiple measurement points on the measurement surface of the object to be measured, and combines the decomposed measurement reflected light for each frequency component and inputs it to the above interference optical system, Multiple projection optical systems, each equipped with a single-point irradiation head, receive decompressed measurement light for each frequency component separated by the above-mentioned optical splitter / multiplexer optical system, irradiate multiple measurement points on the measurement surface of the object to be measured with decompressed measurement light of at least one frequency component for each measurement point, and input decompressed measurement reflected light of at least one frequency component, which is reflected back from the multiple measurement points on the measurement surface, to the above-mentioned optical splitter / multiplexer optical system. A multi-channel measurement optical transmission path consisting of multiple optical fiber cables connecting the above optical splitter / multiplexer optical system and the above projection optical system, A measuring interference photodetector that receives the measuring interference light obtained by the above interference optical system and converts it into an electrical signal to obtain a measuring interference signal, A signal processing unit analyzes the vibration information of the measurement surface based on the interference signal obtained by the above-mentioned interference photodetector. Equipped with, A multi-point vibration measurement system is provided, wherein a demultiplexed measurement light with at least one frequency component is assigned to each of the multiple measurement points on the surface of the object to be measured and irradiated to each measurement point, and the demultiplexed measurement reflected light with at least one frequency component is combined in the optical demultiplexing and combining optical system to obtain vibration information of the multiple measurement points on the surface of the object to be measured, The optical path length variation compensation optical system includes a portion of the decompressed measurement light for each frequency component, decompressed by the optical wave splitting and multiplexing optical system, used as a decompressed measurement reference light, which is irradiated to multiple measurement points on the measurement surface of the object to be measured via multiple single-point irradiation heads provided in the multiple projection optical systems, and an optical path length variation compensation optical system that includes an optical path for compensating for optical path length variation, through which the decompressed measurement reference light passes, which compensates for the optical path length variation of the multiple channels of measurement optical transmission paths through which the decompressed measurement reflected light, which is reflected back from the multiple measurement points on the measurement surface and has at least one frequency component at each measurement point, passes. One or more of the above-mentioned multiple projection optical systems are configured such that the single-point illumination head and the transmission optical path of the optical path length variation compensation optical system are arranged in the same environment, and the single-point illumination head and the return optical path section of the optical path length variation compensation optical system are arranged therein. A multi-point vibration measurement system configured such that, for each measurement point on the measurement surface, the decompressed measurement light for each frequency component, decompressed by the optical splitter / multiplexer optical system, is irradiated from the multiple single-point irradiation heads to multiple measurement points on the measurement surface via the multiple channel measurement transmission paths, and for each measurement point, decompressed measurement reflected light of at least one frequency component, which is reflected by the multiple measurement points on the measurement surface and returns from the multiple single-point irradiation heads to the multiple channel measurement transmission paths, and decompressed measurement reference light as an optical path length compensation optical signal for each measurement point, which returns via the optical path length variation compensation optical system, are input to the optical splitter / multiplexer optical system. The signal processing unit is configured to analyze vibration information at each measurement point on the measurement surface by correcting the optical path length of each of the multiple channel measurement optical transmission paths through which the decompressed measurement light and decompressed measurement reflected light for each frequency component pass, using the calculation result of the optical path length of at least one channel optical path length variation compensation optical path using the decompressed measurement reference light, based on the measurement interference signal obtained by the measurement interference optical detector. [Claim 2] The multi-point vibration measurement system according to claim 1, characterized in that the optical demultiplexing and multiplexing optical system receives measurement light output from the light source via the interference optical system, demultiplexes each frequency component contained in the measurement light into broadband demultiplexed measurement light for each of the multiple frequency components using an optical demultiplexing element, outputs demultiplexed measurement light for each frequency component via a first multi-channel measurement optical transmission path, the demultiplexed measurement light for each frequency component irradiated onto multiple measurement points on the measurement surface of the object to be measured is reflected at the multiple measurement points, the reflected light containing each vibration information is input from the measurement points as demultiplexed measurement reflected light for each frequency component via a second multi-channel measurement optical transmission path to an optical multiplexing element, and the demultiplexed measurement reflected light for each frequency component is combined and input to the interference optical system as the measurement reflected light. [Claim 3] The multipoint vibration meter system according to claim 1, characterized in that the optical demultiplexing and multiplexing optical system comprises an optical demultiplexing element that demultiplexes each frequency component contained in the measurement light and outputs demultiplexed measurement light for each frequency component, and an optical multiplexing element that irradiates multiple measurement points on the measurement surface of an object to be measured with the demultiplexed measurement light for each frequency component demultiplexed by the optical demultiplexing element, and combines the demultiplexed measurement reflected light for each frequency component that is reflected back by the measurement surface and inputs it to the interference optical system as the measurement reflected light. [Claim 4] The coupled optical system comprises multiple coupled optical elements, each having the function of inputting delimited measurement light for each frequency component, delimited by the optical demultiplexing element of the optical splitter / multiplexer optical system, via the first multi-channel measurement light transmission path, outputting delimited measurement light that illuminates multiple measurement points on the measurement surface of the object to be measured via multiple single-point irradiation heads constituting the projection optical system, and inputting the delimited measurement reflected light, which is reflected by the multiple measurement points on the measurement surface and returns via the multiple single-point irradiation heads, to the optical multiplexing element of the optical splitter / multiplexer optical system via the second multi-channel measurement light transmission path. A multi-point vibration measurement system according to any one of claims 1 to 3, characterized in that the decoupled measurement light of at least one frequency component from the decoupled measurement light for each frequency component obtained by the optical decoupler of the optical decoupler optical system is input to the feedback optical path section of at least one optical path length variation compensation optical system provided in the projection optical system via a coupling optical element connected to at least one optical path length variation compensation optical path of the plurality of channels measurement optical transmission paths as the decoupled measurement reference light, and the decoupled measurement reflected light, which includes the decoupled measurement reference light that returns from the feedback optical path section via the coupling optical element to at least one optical path length variation compensation optical path of the plurality of channels measurement optical transmission paths, is combined by the optical multiplexer of the optical decoupler optical system to obtain a measurement reflected light. [Claim 5] The projection optical system comprises multiple optical path length variation compensation optical systems provided for each of the multiple single-point illumination heads constituting the above projection optical system, Using multiple decompressed measurement beams, obtained by decompressing each frequency component contained in the above measurement light, as the above decompressed measurement reference beam, The multi-point vibration measurement system according to any one of claims 1 to 3, characterized in that the signal processing unit is configured to correct for variations in the length of each optical path of the multiple channels of measurement optical transmission paths connecting the multiple single-point irradiation heads constituting the projection optical system and the optical splitter / multiplexer optical system. [Claim 6] The multi-point vibration measurement system according to claim 4, characterized in that each of the multiple single-point irradiation heads constituting the projection optical system incorporates a coupling optical element of the coupling optical system, and is connected to the optical demultiplexing element of the optical demultiplexing optical system via a pair of optical fiber cables consisting of an optical fiber cable through which the demultiplexing measurement light passes and an optical fiber cable through which the demultiplexing measurement reference light passes, and is also connected to the optical multiplexing element of the optical demultiplexing optical system via a pair of optical fiber cables consisting of an optical fiber cable through which the demultiplexing measurement reflected light passes and an optical fiber cable through which the demultiplexing measurement reference light passes. [Claim 7] The above optical demultiplexing optical system comprises an optical demultiplexing element that demultiplexes each frequency component contained in the measurement light input from the above interference optical system via a single optical fiber cable and outputs demultiplexed measurement light for each frequency component via multiple optical fiber cables, and an optical multiplexing element that combines the demultiplexed measurement reflected light for each frequency component input via multiple optical fiber cables and outputs it via a single optical fiber cable. The multi-point vibration measurement system according to claim 6, characterized in that the coupling optical system comprises a coupling optical element that aligns the two optical axes of delimited measurement light and delimited measurement reflected light, which have mutually orthogonal polarization directions and pass through two optical fiber cables, on the measurement surface side. [Claim 8] The multi-point vibration measurement system according to claim 4, characterized in that the optical path length variation compensation optical system comprises a reflector that reflects the deselected measurement reference light for optical path length variation compensation, which is irradiated from the optical splitter / multiplexer optical system through the optical path length variation compensation optical path and the coupling optical element, and returns it to the optical splitter / multiplexer optical system through the coupling optical element and the optical path length variation compensation optical path. [Claim 9] The multi-point vibration measurement system according to claim 4, characterized in that the optical path length variation compensation optical system comprises a retroreflector that reflects the deselected measurement reference light for optical path length variation compensation, which is irradiated from the optical splitter / multiplexer optical system through the optical path length variation compensation optical path and the coupling optical element, and returns it to the optical splitter / multiplexer optical system through the coupling optical element and the optical path length variation compensation optical path. [Claim 10] The multi-point vibration measurement system according to any one of claims 1 to 3, characterized in that the optical path length variation compensation optical system comprises an optical fiber path that directs the deselected measurement reference light for optical path length variation compensation, which is input from the optical splitter / multiplexer optical system via the optical path for optical path length variation compensation, back to the optical path length variation compensation optical system and guides it to the optical splitter / multiplexer optical system.

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