WO2026038352A1 - Capteur de vibrations - Google Patents

Capteur de vibrations

Info

Publication number
WO2026038352A1
WO2026038352A1 PCT/JP2024/029141 JP2024029141W WO2026038352A1 WO 2026038352 A1 WO2026038352 A1 WO 2026038352A1 JP 2024029141 W JP2024029141 W JP 2024029141W WO 2026038352 A1 WO2026038352 A1 WO 2026038352A1
Authority
WO
WIPO (PCT)
Prior art keywords
light
optical system
light receiving
vibration
spot
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Pending
Application number
PCT/JP2024/029141
Other languages
English (en)
Japanese (ja)
Inventor
裕之 河野
拓也 古田
まさ子 浅村
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Mitsubishi Electric Corp
Original Assignee
Mitsubishi Electric Corp
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Mitsubishi Electric Corp filed Critical Mitsubishi Electric Corp
Priority to PCT/JP2024/029141 priority Critical patent/WO2026038352A1/fr
Publication of WO2026038352A1 publication Critical patent/WO2026038352A1/fr
Pending legal-status Critical Current
Anticipated expiration legal-status Critical

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Classifications

    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01H—MEASUREMENT OF MECHANICAL VIBRATIONS OR ULTRASONIC, SONIC OR INFRASONIC WAVES
    • G01H9/00—Measuring mechanical vibrations or ultrasonic, sonic or infrasonic waves by using radiation-sensitive means, e.g. optical means

Definitions

  • This disclosure relates to a vibration sensor that irradiates an object with laser light and measures the vibration of the object using the speckle pattern that occurs in the reflected and scattered light.
  • Patent Document 1 discloses a technology for measuring the vibration of an object by irradiating the rough surface of the object with laser light and capturing the displacement of the resulting speckle pattern with a two-dimensional camera.
  • Non-Patent Document 1 proposes a device that measures acoustic vibrations of an object by imaging the speckle pattern generated by irradiating it with laser light using a line scan camera.
  • the purpose of this disclosure is to provide a vibration sensor that can optimize accuracy and measurement range according to the magnitude of vibration of an object.
  • the vibration sensor disclosed herein comprises a light-projecting unit having a laser light source and a light-projecting optical system that projects the laser light emitted from the laser light source as a spot onto an object; a light-receiving unit having an image sensor and a light-receiving optical system that focuses the reflected and scattered light of the laser light irradiated on the object onto the image sensor; and an image processing device that calculates the amount of movement between frames of a speckle pattern generated in the reflected and scattered light received by the image sensor and measures the vibration of the object based on the amount of movement, wherein the light-receiving optical system includes an imaging lens and is focused on a virtual plane between the object and the light-receiving optical system on the object side where the object exists, which is closer to the light-receiving optical system than the object, and the light-receiving optical system is configured so that the absolute value of the angle formed by a first ray included in the ray bundle incident on the outermost part of the light-re
  • the vibration sensor disclosed herein can optimize accuracy and measurement range to match the magnitude of the vibration of the object.
  • FIG. 1A is a schematic perspective view showing the configuration and main light rays of a vibration sensor according to embodiment 1, and FIG. 1B is a front view showing a linear spot formed on an object by laser light.
  • 1A is a schematic plan view showing the configuration of the light-projecting section and the main light rays of the vibration sensor of embodiment 1
  • FIG. 1B is a schematic plan view showing the configuration of the light-projecting section and the main light rays of the vibration sensor of embodiment 1.
  • 1A is a schematic side view showing the configuration of the light receiving section and the main light rays of the vibration sensor of embodiment 1
  • FIG. 1B is a schematic plan view showing the configuration of the light receiving section and the main light rays of the vibration sensor of embodiment 1.
  • 10A to 10C are diagrams illustrating design examples in which the light receiving unit includes a wide-angle lens.
  • 10A to 10C are diagrams showing design examples in which the light receiving unit includes a telecentric lens.
  • 10A to 10D are diagrams showing design examples in which the light receiving section includes a hyperchromatic lens.
  • 10A and 10B are diagrams illustrating examples of speckle patterns on an area sensor when the light receiving unit includes a wide-angle lens.
  • 10A to 10D are diagrams showing design examples in which the light receiving unit includes a lens that is slightly out of strict telecentricity.
  • 9A and 9B are schematic plan views showing vibration of an object
  • FIGS. 9C and 9D are diagrams showing the movement of a speckle pattern caused by the vibration of the object shown in FIGS.
  • FIG. 10 is a diagram showing an example of a one-dimensional speckle pattern waveform that moves due to vibration.
  • 10A and 10B are diagrams illustrating an example of a process for calculating the vibration amount of a speckle pattern from waveform matching.
  • 10A and 10B are diagrams illustrating an example of a process for calculating the vibration amount of a speckle pattern from waveform matching.
  • 4A and 4B are diagrams illustrating the configuration of a light receiving section and main light rays (optical paths) when zoomed in on the vibration sensor according to the first embodiment.
  • FIG. 2 is a diagram illustrating an example of a hardware configuration of the vibration sensor according to the first embodiment.
  • 10A is a schematic perspective view showing the configuration and main light rays of a vibration sensor according to embodiment 2
  • FIG. 10B is a front view showing a circular spot formed on an object by laser light.
  • 10A, 10B, and 10C are a perspective view, a plan view, and a side view showing the configuration of a light receiving unit and main light rays of a vibration sensor according to a second embodiment.
  • 10A, 10B, and 10C are a perspective view, a plan view, and a side view showing the configuration of a light receiving unit and main light rays of a vibration sensor according to a second embodiment.
  • 10A, 10B, and 10C are a perspective view, a plan view, and a side view showing the configuration of a light receiving unit and main light rays of a vibration sensor according to a third embodiment.
  • 10A, 10B, and 10C are a perspective view, a plan view, and a side view showing the configuration of a light receiving unit and main light rays of a vibration sensor according to a third embodiment.
  • 10A is a schematic perspective view showing the configuration and main light rays of a vibration sensor according to embodiment 4
  • FIG. 10B is a front view showing a linear spot formed on an object by laser light.
  • FIG. 10 is a schematic plan view showing the configuration of a vibration sensor according to a fourth embodiment and main light rays.
  • 10A is a schematic side view showing the configuration of the light-emitting section and the main light rays of the vibration sensor of embodiment 4, and FIG. 10B is a schematic plan view showing the configuration of the light-emitting section and the main light rays of the vibration sensor of embodiment 4.
  • 10A is a schematic side view showing the configuration of the light receiving section and the main light rays of the vibration sensor of embodiment 4, and
  • FIG. 10B is a schematic plan view showing the configuration of the light receiving section and the main light rays of the vibration sensor of embodiment 4.
  • 10A to 10C are diagrams showing the overlap of the light receiving surface of the line sensor and the image of the speckle pattern (image of the line-shaped spot).
  • 10 is a schematic plan view showing image displacement when the distance changes in the vibration sensor according to the fourth embodiment.
  • FIG. 10A to 10D are schematic plan views showing image shifts when the distance changes in the vibration sensor according to the third embodiment.
  • vibration sensors according to embodiments will be described with reference to the drawings.
  • the following embodiments are merely examples, and it is possible to combine and modify the embodiments as appropriate.
  • similar components are designated by the same reference numerals in each drawing.
  • FIG. 1A is a schematic perspective view showing the configuration and main light beams of a vibration sensor 1 according to the first embodiment.
  • FIG. 1B is a front view showing a spot 91 formed by a laser beam irradiated onto an object 90, which is the target of vibration sensing.
  • the vibration sensor 1 is a device that irradiates the object 90 (rough surface) with laser beam and measures the vibration of the object 90 using a speckle pattern generated in the reflected and scattered light.
  • the vibration sensor 1 includes a light-projecting unit 10 that irradiates the object 90 with laser beam, a light-receiving unit 40 that receives the reflected and scattered light generated by the object 90 irradiated with the laser beam, and an image processing device 70 that serves as an information processing device that detects vibrations based on a detection signal output from the light-receiving unit 40.
  • the light-projecting unit 10 and the light-receiving unit 40 are housed within a light-projecting and light-receiving head 5 (e.g., within a single housing).
  • the figure shows the coordinate axes of an X'YZ' Cartesian coordinate system as a first coordinate system used to explain the light-projecting unit 10.
  • the figure also shows the coordinate axes of an XYZ Cartesian coordinate system as a second coordinate system used to explain the light-receiving unit 40, the target object 90, and the observation surface 92.
  • the central ray of the laser light emitted from the light-projecting unit 10 is parallel to the Z' axis
  • the central ray of the light received by the light-receiving unit 40 is parallel to the Z axis.
  • the Y axis is the coordinate axis normal to a plane containing the Z' axis and the Z axis.
  • the X' axis is the coordinate axis perpendicular to both the Y axis and the Z' axis.
  • the X axis is the coordinate axis perpendicular to both the Y axis and the Z axis.
  • the light-projecting unit 10 has a laser light source 20 and a light-projecting optical system 30 that projects the laser light emitted from the laser light source 20 onto the object 90 as a circular spot 91.
  • the light-receiving unit 40 has an area sensor 50 (also called a "two-dimensional area sensor” or “area camera”) as an imaging sensor, and a light-receiving optical system 60 that focuses the reflected and scattered light of the laser light irradiated onto the object 90 onto the area sensor 50 (i.e., onto the light-receiving surface of the area sensor 50).
  • the image processing device 70 calculates the amount of movement (i.e., shift amount) between frames of the speckle pattern generated in the reflected and scattered light received by the area sensor 50, and estimates (i.e., calculates) the vibration of the object 90 based on this amount of movement.
  • the amount of movement i.e., shift amount
  • the light-projecting unit 10 and the light-receiving unit 40 are arranged so that the first optical axis 11, which is the optical axis of the light-projecting unit 10, and the second optical axis 41, which is the optical axis of the light-receiving unit 40, intersect on the target object 90.
  • the light-projecting unit 10 and the light-receiving unit 40 are arranged side by side in the same direction as the first direction (X direction).
  • the optical axis of the light-projecting unit 10 may be the axis of the laser light emitted from the light-projecting unit 10.
  • the optical axis of the light-receiving unit 40 may be the axis of the reflected and scattered light that can be received by the line sensor 50.
  • the projection optical system 30 includes a collimating lens 31 as a lens through which the laser light passes, and a spot changing mechanism 35 that changes the size of the spot 91 on the object 90.
  • the spot changing mechanism 35 includes a distance adjustment mechanism that can adjust the distance Lc between the light emitting point of the laser light source 20 and the collimating lens 31.
  • the image processing device 70 uses the spot changing mechanism 35 to change the size of the spot 91 on the object 90 based on the measured vibrations.
  • Figure 2(A) is a schematic plan view (i.e., a view of the light-projecting unit 10 in the -Y direction) showing the configuration and main light rays of the light-projecting unit 10 of the vibration sensor 1 according to embodiment 1.
  • Figure 2(B) is a schematic plan view (i.e., a view of the light-projecting unit 10 in the -Y direction) showing the configuration and main light rays of the light-projecting unit 10 of the vibration sensor 1.
  • the light projection unit 10 has a laser light source 20, a collimator lens 31, and a spot changing mechanism 35 that can adjust the distance Lc between the light emission point of the laser light source 20 and the collimator lens 31.
  • Figure 2(A) shows a case where the distance Lc is small, in which case the diameter W of the circular spot 91 on the object 90 is large.
  • Figure 2(B) shows a case where the distance Lc is large, in which case the diameter W of the circular spot 91 on the object 90 is small.
  • the diameter W of the circular spot 91 on the object 90 increases, and as the collimator lens 31 becomes farther from the light emission point of the laser light source 20, the diameter W of the circular spot 91 on the object 90 decreases.
  • Figure 3(A) is a schematic side view (i.e., a view of the light receiving unit 40 in the X direction) showing the configuration and main light rays of the light receiving unit 40 of the vibration sensor 1 according to embodiment 1.
  • Figure 3(B) is a schematic plan view (i.e., a view of the light receiving unit 40 in the -Y direction) showing the configuration and main light rays of the light receiving unit 40 of the vibration sensor 1.
  • the light receiving unit 40 has an area sensor 50 as an imaging sensor and a light receiving optical system 60.
  • the light receiving optical system 60 is composed of an imaging lens 61 and an aperture 69, and is an object-side telecentric optical system or a hyper-tric optical system.
  • Figure 1 shows a configuration in which an aperture 69 is located between the area sensor 50 and one imaging lens 61, which is the simplest configuration for realizing an object-side telecentric optical system. However, in actual lens designs, an object-side telecentric optical system is realized with multiple lens combinations and apertures.
  • Figures 3 (A) and (B) show an example in which the light receiving optical system 60 is a hyper-tric optical system.
  • An object-side telecentric optical system is an optical system in which the chief rays 96a to 96d from each image height traveling from the lens toward the object are parallel to the optical axis (i.e., the second optical axis 41). Specifically, it is an optical system in which chief rays 96a to 96d (shown in Figures 5(A) to 5(C) described below) from each image height directed from the lens to the object are parallel to the extent that they do not intersect with the optical axis within the range of the distance from the light-receiving optical system 60 to the object 90.
  • a hypertropic optical system is a special optical system in which chief rays 96a to 96d ( Figures 5(A) to 5(C)) from each image height directed from the lens to the object converge toward the optical axis (i.e., the second optical axis 41). Specifically, it is an optical system in which chief rays 96a to 96d ( Figures 5(A) to 5(C)) from each image height directed from the lens to the object converge toward the optical axis within the range of the distance from the light-receiving optical system 60 to the object 90.
  • the object side refers to the side on which the object 90 exists as viewed from the light receiving optical system 60.
  • the light receiving optical system 60 forms a focus on a virtual plane that is closer to the light receiving optical system 60 than the object 90 between the object 90 and the light receiving optical system 60 on the object side.
  • the light receiving optical system 60 is configured so that an object-side focal plane that forms an image on the area sensor 50 exists at a position that is closer to the light receiving optical system 60 than the object 90 between the object 90 and the light receiving optical system 60 on the object side.
  • the light receiving optical system 60 is preferably a lens (optical system) that is telecentric on the object side or a lens (optical system) that is nearly telecentric on the object side.
  • the light receiving unit 40 is configured so that the absolute value
  • the first optical axis 11 of the light-projecting unit 10 and the second optical axis 41 of the light-receiving unit 40 intersect on the target object 90.
  • the vibration sensor 1 has a mechanism for adjusting the direction of the first optical axis 11 of the light-projecting unit 10 (i.e., the direction of the central ray of the laser light emitted from the light-projecting unit 10) or the direction of the second optical axis 41 of the light-receiving unit 40 so that they intersect even if the distance to the target object 90 changes.
  • the surface of the object 90 is rough, and the light reflected and scattered by the object 90 from the circular spot 91 irradiated by the light projector 10 generates a speckle pattern throughout the entire space.
  • the image of the speckle pattern generated in this space is acquired by the light receiver 40 (i.e., the image is formed on the light receiving surface of the area sensor 50 of the light receiver 40).
  • the position where the speckle pattern image is acquired is the speckle pattern observation plane 92.
  • the observation plane 92 is an example of a virtual plane where the light receiving optical system 60 focuses at a position closer to the light receiving optical system 60 than the object 90 between the object 90 and the light receiving optical system 60 on the object side.
  • the plane conjugate with the light receiving surface of the area sensor 50 is not the object 90, but a virtual plane at a distance L in front of the light receiving optical system 60; this virtual plane is called the speckle pattern observation plane 92.
  • the distance between the speckle pattern observation plane 92 and the object 90 is L.
  • the light receiving unit 40 does not acquire an image of the circular spot 91 on the object 90, but rather an image of the circular spot 91 that is defocused by a large distance L.
  • the image information acquired by the area sensor 50 is sent to the image processing device 70, where the vibration amount of the speckle pattern is calculated using an algorithm described below.
  • the light receiving optical system 60 of the light receiving unit 40 be an object-side telecentric optical system.
  • the light receiving optical system 60 of the light receiving unit 40 may be a hyper-telecentric optical system. The reason for this will be explained using design examples of the light receiving unit 40 in Figures 4(A) to 4(C), Figures 5(A) to 5(C), and Figures 6(A) to 6(D).
  • Figures 4(A) to (C), Figures 5(A) to (C), and Figures 6(A) to (D) image points P0, P1, P2, and P3 for the ray tracing simulation are placed on the area sensor 50, and rays are traced from there in the opposite direction to the original direction of the rays.
  • Figures 4(A), 5(A), and 6(A) show ray bundles 95a to 95d from the area sensor 50 to a plane 94 on the object 90.
  • Figures 4(B), 5(B), and 6(B) show only the chief rays 96a to 95d of the ray bundles 95a to 95d in Figures 4(A), 5(A), and 6(A).
  • Figures 4(C), 5(C), and 6(C) are enlarged views of the views from the area sensor 50 to the speckle pattern observation surface 92 in Figures 4(A), 5(A), and 6(A).
  • the focal length f of the imaging lens 61 is 6.5 mm
  • the X coordinate values of image points P0 to P3 are 0 mm, 1 mm, 2 mm, and 4 mm, respectively.
  • the light-receiving surface of the area sensor 50 is assumed to be 8 mm x 8 mm in size.
  • Image point P3 is the outermost image point (farthest from the optical axis).
  • the aperture diameter of the diaphragm 69 is 1.6 mm.
  • the diaphragm 69 plays an important role in determining the numerical aperture NA of the ray bundle that can be captured on the object side.
  • the degree of divergence of the chief ray on the object side can be changed, making it possible to configure an object-side telecentric optical system or a hypercentric optical system.
  • the chief rays that pass through the center of the diaphragm are designated 96a to 96d.
  • the width (diameter W) of the circular spot 91 irradiated onto the object 90 from the light projector 10 is 6 mm.
  • Figures 4(A) to (C) show an example in which the light receiving optical system 60 of the light receiving unit 40 is a wide-angle lens.
  • the position of the aperture 69 is the same as the position of the imaging lens 61.
  • the respective light beams 95a to 95d emitted from image points P0, P1, P2, and P3 are focused on the speckle pattern observation surface 92.
  • Chief rays 96b to 96d, excluding chief ray 96a traveling on the second optical axis 41, are incident on the speckle pattern observation surface 92 at an angle and each travel in a downward rightward direction (positive direction), as represented by the angle ⁇ in Figure 4(C).
  • each chief ray 96a to 96d is widely spread on the plane 94 on the object 90, as shown in Figure 4(B).
  • each of the light beams 95a-95d also spreads around the chief rays 96a-96d after passing through the speckle pattern observation surface 92.
  • the diffused light source emitted from the circular spot 91 is read.
  • the light beams 95b-95d do not overlap with the circular spot 91, so the light beams emitted from the circular spot 91 reach only the area inside the image point P1 on the area sensor 50.
  • the light-receiving unit 40 shown in FIGS. 4A to 4C is not suitable for vibration sensing.
  • Figures 5(A) to (C) show an example in which the light-receiving optical system 60 of the light-receiving unit 40 is an object-side telecentric optical system.
  • the light-receiving optical system 60 becomes an object-side telecentric optical system.
  • Figure 5(C) shows the simulated ray bundles 95a to 95d emanating from image points P0 to P3 into directions parallel to the optical axis (second optical axis 41 in the Z direction), with their chief rays 96a to 96d focused on the speckle pattern observation surface 92.
  • the chief rays 96a to 96d that pass through the speckle pattern observation surface 92 propagate parallel to the optical axis, as shown in Figure 5(B). Therefore, even if the distance L between the plane 94 on the object 90 and the observation plane 92 of the speckle pattern is large, the width in the X direction of the group of chief rays (i.e., the group of chief rays 96a to 96d) does not change. Therefore, as shown in FIG. 5A , even if the distance L is large, the amount of overlap deviation of the light beams 95a to 95d on the plane 94 does not change, and all of the light beams 95a to 95d overlap with the circular spot 91.
  • the light receiving optical system 60 which is an object-side telecentric optical system, is focused on a speckle pattern observation surface 92 located between the object 90 and the light receiving optical system 60 on the object side, where the object 90 exists, and is closer to the light receiving optical system 60 than the object 90.
  • This is an example of a light receiving optical system configured so that the absolute value of the angle formed by the light ray (first light ray) included in the light ray bundle 95d incident on the outermost part of the light receiving surface of the area sensor 50 and the optical axis of the light receiving unit 40 is smaller than the cone half angle of the light ray bundle on the object side 92, which is determined by the numerical aperture of the light receiving optical system 60.
  • Figures 6(A) to (D) show an example where the light receiving optical system 60 of the light receiving unit 40 is a hypertric optical system on the object side.
  • the light receiving unit 40 becomes a hypertric optical system.
  • Figure 6(C) where simulated ray bundles 95a to 95d emanating from image points P0 to P3 are converted by the imaging lens 61 so that their chief rays 96a to 96d are directed toward the optical axis, and focus at the speckle pattern observation plane 92.
  • a system in which the inclination of the chief rays 96a to 96d toward the optical axis in this way is called a hypertric optical system.
  • chief rays 96a to 96d that pass through speckle pattern observation surface 92 intersect at point Q, which is located between speckle pattern observation surface 92 and object 90 and is closer to speckle pattern observation surface 92 than to object 90, and then diverge from each other. Therefore, in the case shown in FIG. 6A, ray bundles 95a to 95d completely overlap at point Q, with a slight deviation in overlap at plane 94. However, in the case of FIG. 6A, all ray bundles 95a to 95d include a circular spot 91 on plane 94.
  • the speckle pattern appears across the entire light-receiving surface of area sensor 50.
  • an image with a sufficiently large number of pixels can be obtained to measure the amount of movement of the speckle pattern, making it suitable for vibration sensing.
  • the light receiving optical system 60 which is a hyperoptic optical system on the object side, is focused on a speckle pattern observation surface 92 located between the object 90 and the light receiving optical system 60 on the object side where the object 90 exists, closer to the light receiving optical system 60 than the object 90.
  • a hypertric optical system when the distance L to the object 90 is short, the overlap of the light beams 95a to 95d is large and the speckle pattern appears over the entire surface.
  • the distance L is very large compared to the degree of inclination of the chief rays 96a to 96d, the overlap of the light beams 95a to 95d becomes small and the outline of the speckle pattern may become smaller than the size of the area sensor 50. Therefore, a hypertric optical system is an effective optical system for an object 90 that is close to the object 90.
  • light beam 97 is the outermost light beam of light beam 95d in the direction from image point P3 toward image point P0 (-X direction).
  • light beam 97 becomes the innermost light beam of light beam 95d as shown in FIG. 8D.
  • light beam 97 becomes the light beam of light beam 95d that exists furthest in the +X direction in the direction from image point P0 toward image point P3 (+X direction).
  • the condition for the reflected and scattered light of circular spot 91 to reach point P3 is that light beam 97 is located above the lower end of circular spot 91 on plane 94.
  • a necessary condition for this is that the light ray 97 must be at least angled upward, and this is expressed by the following equation (2) using the angle ⁇ that the chief ray 96d makes with the optical axis.
  • the light-receiving optical system 60 which is not completely telecentric on the object side, focuses the speckle pattern observation surface 92 at a position closer to the light-receiving optical system 60 than the object 90 is between the object 90 and the light-receiving optical system 60 on the object side, which is the side on which the object 90 exists, and is an example of a light-receiving optical system configured so that the absolute value of the angle formed by the light ray (first light ray) included in the light ray bundle 95d incident on the outermost side of the light-receiving surface of the area sensor 50 and the optical axis of the light-receiving unit 40 is smaller than the cone half angle of the light ray bundle on the object side 92, which is determined by the numerical aperture of the light-receiving optical system 60.
  • ⁇ is half the angle of view of the light receiving unit 40.
  • FIGS. 8A to 8D show the same explanation as in the cases of FIGS. 8A to 8D.
  • the angle ⁇ that the chief ray 96d makes with the optical axis is defined to be a negative value.
  • FIG. 6D shows a ray diagram extracting only the optical path of the ray bundle 95d emanating from point P3.
  • ⁇ NA the cone half angle of the ray bundle 95d on the object side
  • ⁇ NA >
  • the light receiving unit 40 in order to generate a speckle pattern over the entire light receiving surface of the area sensor 50, it is desirable to satisfy the following condition (A1) or (A2).
  • the light receiving unit 40 is an object-side telecentric optical system.
  • the light receiving unit 40 is an optical system that is slightly shifted from an object-side telecentric optical system (i.e., an optical system that is close to an object-side telecentric optical system).
  • an object-side hypercentric optical system is a light receiving optical system that satisfies condition (A2).
  • FIGS. 9A and 9B are schematic plan views (i.e., views of the light receiving unit 40 viewed in the ⁇ Y direction) showing the configuration of the light receiving unit 40 of the vibration sensor 1 according to the first embodiment, the main light rays, and the displacement (e.g., vibration) of the object 90.
  • FIGS. 9A and 9B show the displacement due to the vibration of the object 90.
  • FIGS. 9C and 9D are diagrams showing the movement on the observation plane 92 of the speckle pattern generated by the vibration of the object 90 shown in FIGS. 9A and 9B, respectively.
  • the speckle pattern observed on the observation surface 92 is a random granular pattern, as shown in Figures 9(C) and (D), for example.
  • the speckle pattern observed on the observation surface 92 of the speckle pattern is shown in Figure 9(C).
  • the light receiving optical system 60 causes the area sensor 50 to acquire the two-dimensional image of Figure 9(C).
  • the object 90 vibrates, it not only vibrates in the Z direction at the laser irradiation position, but may also vibrate angularly in the angular direction.
  • Angular vibration modes include vibrations in all directions within the XY plane, but the direction of vibration is considered to be constant.
  • Figure 9(B) shows the optical path of the light receiving system when the object 90 is tilted around the Y axis by a tilt angle ⁇ .
  • the optical path is almost the same as in Figure 9(A), but the speckle pattern image acquired by the area sensor 50 is the image in Figure 9(C) shifted by ⁇ X in the X direction, as shown in Figure 9(D).
  • Figures 9(C) and (D) due to the vibration of the object 90, the image acquired by the area sensor 50 is displaced (vibrates) only in the X direction.
  • Figure 10 is a diagram showing an example of a one-dimensional speckle pattern waveform that moves due to vibration.
  • Wave (a) and wave (b) in Figure 10 are one-dimensional waveforms corresponding to the profile on cross-sectional line 96 in Figures 9 (C) and (D), and are one-dimensional cross-sectional waveforms of the output image of area sensor 50.
  • wave (a) shifts in the X direction by an amount ⁇ X, as in wave (b), due to the tilt angle ⁇ (angle change) of object 90.
  • the amount of movement in the X direction of the signal waveform acquired by area sensor 50 is calculated for each frame, and by accumulating this amount of movement, a vibration waveform corresponding to the angle change due to vibration can be obtained.
  • ⁇ Algorithm for extracting displacement from successive speckle pattern images> To calculate the shift amount of the signal waveform, for example, waveform matching processing is used. As shown in FIG. 10 , ideally, a waveform is obtained that is shifted by a shift amount ⁇ X in the X direction while maintaining the waveform shape.
  • Several methods are known for calculating the shift amount ⁇ X from these two waveforms. For example, the sum of absolute values of differences for each pixel (SAD) or the sum of squared differences (SSD) of differences for each pixel can be calculated as the similarity, and the shift amount ⁇ X can be calculated from the calculated similarity.
  • the pixel pitch is, for example, a value within a range of approximately 5 ⁇ m to 2 ⁇ m, but is not limited thereto.
  • similarity is calculated using SAD is described as an example.
  • the similarity RSAD (x) is calculated using the following equation (4).
  • the similarity RSAD (x) is calculated by calculating the similarity between the luminance value fa(i) in the pixel range from pixel number i min to i max and the luminance value fb(i+x) at a position obtained by shifting the luminance value fb(i) by an unknown quantity x.
  • the similarity RSAD (x) is calculated by changing x, and the shift amount ⁇ X is the value of x that results in the smallest similarity RSAD (x), as shown in the following equation (5).
  • FIGS. 11A and 11B, and FIGS. 12A and 12B are diagrams illustrating an example process for calculating the vibration amount of a speckle pattern from waveform matching.
  • This method determines the shift amount ⁇ X, which is the amount of movement between consecutive image frames. This is performed for all consecutive frames.
  • FIG. 11B shows an example of calculating the shift amount ⁇ X for the first 50 frames. The shift amount ⁇ X is the amount of image movement between adjacent frames.
  • the shift amount from the (n-1)th frame to the nth frame is defined as ⁇ Xn . Then, the amount of movement X(n) from the initial position in the nth frame is obtained by integrating the amount of movement between frames, as shown in the following equation (6).
  • Figure 7(A) shows an example of the amount of movement X(n) from the initial position in the nth frame. If it were vibration, the data would be distributed above and below the zero line on the vertical axis, but actual data contains a low-frequency offset, as shown here. The offset is thought to be due to the accumulation of errors when calculating the amount of movement in the speckle pattern image, and the gradual movement of the irradiation position of the linear spot 91a on the object 90. To subtract this offset, for example, a process can be performed to remove low-frequency components using a high-pass filter.
  • Figure 7(B) shows the data in Figure 7(A) after applying a high-pass filter, and this is the vibration signal we are looking for.
  • the inter-frame shift amount ⁇ X obtained by calculating the minimum value of R SAD (x) will contain a large error when the tilt angle ⁇ is large.
  • the waveform obtained by equation (6) will be proportional to the amount of vibration of the object 90 .
  • the light receiving unit is neither an object-side telecentric optical system nor an object-side hypercentric optical system, nor an optical system close to an object-side telecentric optical system. Therefore, the outer shape of the speckle pattern acquired by the area sensor 50 is small relative to the area sensor 50, as illustrated in FIG. 7 . Therefore, even if the amount of movement of the speckle pattern is calculated based on Equation (4), the number of pixels is insufficient, resulting in poor image matching accuracy. Furthermore, if the shift amount ⁇ X between consecutive frames is large, ⁇ X exceeds the outer size of the speckle pattern, making image pattern matching impossible. In other words, with the conventional method, the outer size of the speckle pattern that can be acquired is not large enough, making it impossible to perform vibration measurement with sufficiently high accuracy and a sufficiently wide measurement range.
  • the light receiving unit 40 of the vibration sensor in the first embodiment is an object-side telecentric optical system, an object-side hypercentric optical system, or an optical system slightly shifted from an object-side telecentric optical system (an optical system close to an object-side telecentric optical system), and can generate a speckle pattern image over the entire light receiving surface of the area sensor 50. Therefore, it is possible to obtain an image with a width sufficiently large relative to the shift amount ⁇ X of the speckle pattern. This can improve the accuracy of the vibration sensor 1 and also expand the vibration measurement range.
  • Figures 13A and 13B show optical path diagrams in which three image points are placed on the area sensor 50 and light rays are traced from there in the opposite direction to the normal direction in order to show the range in which the light receiving unit 40 can capture an image of a speckle pattern.
  • the light receiving unit 40 can transfer the speckle pattern that appears within the range of field of view width X2a on the speckle pattern observation surface 92 onto the area sensor 50 at a reduction magnification of 1.
  • the field of view width X2b on the observation surface 92 of the speckle pattern imaged by the area sensor 50 is twice the field of view width X2a.
  • the vibration sensor 1 can reconstruct sound from the vibration.
  • the vibration sensor 1 is a sound reconstruction device and is called a laser microphone.
  • the audible range used in everyday conversation is approximately 4 kHz.
  • the minimum frame rate required for the line sensor 50a based on the sampling theorem is twice that, at 8 kHz.
  • a faster frame rate is required to accurately acquire vibration waveforms even when the vibration amplitude is large. Therefore, it is desirable for the line sensor 50a to have a frame rate of 20 kHz to 40 kHz.
  • the exposure time of the line sensor 50a cannot be longer than the frame period, as the frame rate increases, the exposure time becomes shorter (i.e., the image becomes darker).
  • the light receiving efficiency is improved, allowing the frame rate to be improved and allowing the device to be used as a laser microphone to reconstruct sounds that require a high frame rate.
  • the laser microphone can remotely measure only the vibrations at the point on the object where the laser is irradiated, without passing through air compression waves, it can obtain the necessary sound information even in noisy environments.
  • FIG 14 is a diagram showing an example of the hardware configuration of the image processing device 70 of the vibration sensor 1.
  • the image processing device 70 has a processor 101, memory 102, storage device 103, and interface 104.
  • the image processing device 70 may be a computer.
  • the processor 101 is a CPU (Central Processing Unit) or the like.
  • the memory 102 is, for example, a volatile semiconductor memory such as RAM (Random Access Memory).
  • the storage device 103 is a non-volatile storage device such as a hard disk drive (HDD) or solid state drive (SSD).
  • a detection signal from the area sensor 50, which serves as an imaging sensor, is input to the interface 104.
  • HDD hard disk drive
  • SSD solid state drive
  • Each function of the image processing device 70 may be realized by a processing circuit.
  • the processing circuit may be dedicated hardware, or may be a processor 101 that executes a program stored in memory 102.
  • the processor 101 may be any of a processing device, arithmetic unit, microprocessor, microcomputer, and DSP (Digital Signal Processor).
  • the processing circuit may be, for example, a single circuit, a composite circuit, a programmed processor, a parallel programmed processor, an ASIC (Application Specific Integrated Circuit), an FPGA (Field-Programmable Gate Array), or any combination of these.
  • ASIC Application Specific Integrated Circuit
  • FPGA Field-Programmable Gate Array
  • the processing circuit is a processor 101
  • the program is realized by software, firmware, or a combination of software and firmware.
  • Software and firmware are written as programs and stored in memory 102.
  • the processor 101 can realize the functions of the image processing device 70 shown in FIG. 1 by reading and executing the programs stored in memory 102.
  • Fig. 15(A) is a schematic perspective view showing the configuration and main light rays of a vibration sensor 2 according to embodiment 2.
  • Fig. 15(B) is a front view showing a circular spot 91 formed on an object 90 by laser light.
  • the light-projecting unit 10 of the vibration sensor 2 is the same as that shown in Fig. 2.
  • the light-receiving unit 40a is provided with a cylindrical lens 62 for collecting light, which has a concave surface in the Y direction, in front of (upstream of) the imaging lens 61.
  • the imaging sensor is not an area sensor 50, but a line sensor 50a extending in the X direction.
  • Figures 16(A), (B), and (C) are a perspective view, a plan view (i.e., a view of the light receiving unit 40a when viewed in the -Y direction), and a side view (i.e., a view of the light receiving unit 40a when viewed in the X direction) showing the configuration and main light rays of the light receiving unit 40a of the vibration sensor 2 according to embodiment 2.
  • Figures 17(A), (B), and (C) are a perspective view, a plan view (i.e., a view of the light receiving unit 40a when viewed in the -Y direction), and a side view (i.e., a view of the light receiving unit 40a when viewed in the X direction) showing the configuration and main light rays of the light receiving unit 40a of the vibration sensor 2 according to embodiment 2.
  • the imaging lens 61a is an axially symmetric lens, and, as in the case of Figure 3, forms an object-side hyperchromatic optical system together with the aperture 69.
  • the imaging lens 61a, aperture 69, and cylindrical lens 62 together form the light receiving optical system 60.
  • the light receiving optical system 60 and line sensor 50a together form the light receiving unit 40a.
  • the focusing cylindrical lens 62 does not have a light focusing effect, so as in the case of Figure 3 (B), the focus is on the speckle pattern observation surface 92. That is, in the X direction, the plane conjugate with the plane of the line sensor 50a is not the object 90, but the speckle pattern observation surface 92, which is a distance Ls in front of the imaging lens 61a. The distance between the speckle pattern observation surface 92 and the object 90 is L. In the X direction, the light receiving unit 40a does not acquire an image of the circular spot 91 on the object 90, but rather an image of the circular spot 91 that is significantly defocused by the distance L.
  • the one-dimensional image information acquired by the line sensor 50a is sent to the image processing device 70, which calculates the vibration amount of the speckle pattern.
  • the focal point is a circular spot 91 on the object 90 due to the action of the condensing cylindrical lens 62.
  • the focal length of the concave cylindrical lens 62 is ⁇ f cyl
  • the distance from the cylindrical lens 62 to the speckle pattern observation surface 92 is L cyl .
  • L cyl is approximately equal to
  • L cyl is adjusted using the position adjustment mechanism 36 that adjusts the position of the cylindrical lens 62 in the Z direction in accordance with the distance L, so that the focus is on the object 90 in the Y direction.
  • the one-dimensional waveform of the speckle pattern acquired by line sensor 50a is similar to the waveform in Figure 10 in embodiment 1. Therefore, the same algorithm as in embodiment 1 can be used to detect changes in the speckle pattern waveform that shifts in the X direction.
  • Vibration sensor 2 in embodiment 2 differs from vibration sensor 1 in embodiment 1 in that it can detect only the X-direction vibration component of the vibration angle components of object 90.
  • the zoom magnification can be changed appropriately each time during the measurement process in accordance with the magnitude of vibration.
  • the combination of the axially symmetric imaging lens 61a and aperture 69 allows the transfer magnification to be changed while still satisfying the condition of object-side hyper-constriction.
  • the position adjustment mechanism 36 is fine-tuned so that the focus is always on the object 90 even when the zoom magnification of the imaging lens 61a is changed. This ensures that maximum light-gathering effect is always achieved in the Y direction as well.
  • the zoom magnification can be reduced to expand the measurement range, and when vibration is small, the zoom magnification can be increased to improve accuracy.
  • line sensor 50a has a smaller pixel count than area sensor 50, and high frame rate products are readily available. Therefore, embodiment 2 has the advantage of being able to measure vibrations at higher speeds than embodiment 1.
  • the frame rate of line sensor 50a is, for example, 3 kHz, but is not limited to this.
  • the line sensor 50a extends in the X direction, but this has the following advantage.
  • the circular spot 91 emitted by the light-projecting unit 10 and the second optical axis 41 of the light-receiving unit 40a shift in the X direction.
  • the line sensor 50a extends within the plane spanned by the first optical axis 11 of the laser from the light-projecting unit 10 and the second optical axis 41 of the light-receiving unit 40a.
  • the light-receiving unit 40a is an optical system that is focused on the object 90 in the Y direction, but is significantly out of focus from the object 90 in the X direction. Therefore, even if the position is slightly shifted in the X direction, light can reach the line sensor 50a, and the speckle pattern can be captured by the line sensor 50a.
  • the extension direction of the line sensor 50a does not have to be the X direction; vibration measurement is possible as long as the extension direction of the line sensor 50a coincides with the direction in which the cylindrical lens 62, which has a concave surface, has no curvature.
  • embodiment 2 is the same as embodiment 1.
  • Third Embodiment 18A, 18B, and 18C are a perspective view, a plan view (i.e., a view of the light receiving unit 40b in the -Y direction), and a side view (i.e., a view of the light receiving unit 40b in the X direction) showing the configuration and main light rays of the light receiving unit 40a of the vibration sensor 3 according to the third embodiment.
  • 19A, 19B, and 19C are a perspective view, a plan view (i.e., a view of the light receiving unit 40b in the -Y direction), and a side view (i.e., a view of the light receiving unit 40b in the X direction) showing the configuration and main light rays of the light receiving unit 40b of the vibration sensor 3 according to the third embodiment.
  • the vibration sensor 3 for vibration sensing in the third embodiment is obtained by replacing the light receiving unit 40a in FIG. 15 of the second embodiment with the light receiving unit 40b in FIGS. 18A to 18C and 19A to 19C.
  • the light projecting unit 10 is the same as that shown in FIG. 2, and projects a circular spot 91 onto the object 90 .
  • the light receiving unit 40b is provided with a cylindrical lens 62a having a convex surface in the X direction in front of the axially symmetric imaging lens 61.
  • the imaging lens 61 and the cylindrical lens 62a constitute the light receiving optical system 60.
  • a line sensor 50a is installed as the imaging sensor, rather than an area sensor 50.
  • the light rays shown in Figures 18 (A) to (C) and Figures 19 (A) to (C) are virtual light rays propagating in the reverse direction from the line sensor 50a. In other words, these figures show light rays that can reach the line sensor 50a.
  • This wide-angle imaging lens 61 alone is not telecentric on the object side, and as explained in embodiment 1 using Figure 7, it is not possible to obtain a speckle pattern image (one-dimensional waveform) with a sufficiently large outer width on the line sensor 50a.
  • Ls 100 [mm]
  • Embodiment 3 differs from embodiment 2 in the method of optical alignment.
  • the light receiving unit 40b In the Y direction, the light receiving unit 40b must be focused on the object 90. Because the cylindrical lens 62a does not have a refractive effect in the Y direction, the focus adjustment mechanism of the imaging lens 61 can be used (for example, by turning the focus adjustment ring) to focus on a circular spot 91 on the object 90. Then, the position adjustment mechanism 36, which moves the position of the cylindrical lens 62a in the optical axis direction (i.e., the Z direction), can be used to adjust the spacing Ls so that the lens is telecentric in the X direction. Because the focus is at the distant distance L in the Y direction, the focus is set at a position close to the cylindrical lens 62a in the X direction, which becomes the observation plane 92 for the speckle pattern.
  • the field of view width X2b of Figure 19(B) on the speckle pattern observation surface 92 is twice the field of view width X2a of Figure 18(B). Therefore, as with the explanation given in embodiment 2, in the X direction in which the shift amount of the speckle pattern waveform is measured, the width for observing the speckle pattern waveform is doubled, and the measurable amplitude is doubled.
  • the focus of the imaging lens 61 is fine-tuned so that the focus is always on the object 90 even when the zoom magnification of the imaging lens 61 is changed. This ensures that maximum light-gathering effect is always achieved in the Y direction as well.
  • the zoom magnification can be reduced to expand the measurement range, and when vibration is small, the zoom magnification can be increased to improve accuracy.
  • the imaging lens 61 equipped with a zoom function as in embodiment 3 is small and inexpensive. Therefore, a vibration sensor 3 that is smaller than the light receiving unit 40 in embodiment 1 can be obtained.
  • embodiment 3 also has the advantage of being able to measure vibrations at higher speeds than embodiment 1.
  • the line sensor 50a extends in the X direction, but this has the following advantage.
  • the circular spot 91 emitted by the light-projecting unit 10 and the second optical axis 41 of the light-receiving unit 40b are shifted in the X direction.
  • the line sensor 50a extends within the plane defined by the first optical axis 11 of the laser from the light-projecting unit 10 and the second optical axis 41 of the light-receiving unit 40b.
  • the light-receiving unit 40b is an optical system that is focused on the object 90 in the Y direction, but is significantly out of focus from the object 90 in the X direction. Therefore, even if the position is slightly shifted in the X direction, light can reach the line sensor 50a, and the speckle pattern can be captured by the line sensor 50a.
  • the extension direction of the line sensor 50a does not have to be the X direction; vibration measurement is possible as long as the extension direction of the line sensor 50a coincides with the direction of curvature of the cylindrical lens 62a, which has a convex surface.
  • embodiment 3 is the same as embodiment 1 or 2.
  • FIG. 20A is a schematic perspective view showing the configuration and main light beams of a vibration sensor 4 according to the fourth embodiment.
  • FIG. 20B is a front view showing a linear spot 91a formed by laser light irradiated onto an object 90, which is the target of vibration sensing.
  • FIG. 21 is a schematic plan view (i.e., a view of the light-projecting unit 10a and the light-receiving unit 40a in the -Y direction) showing the configuration and main light beams of the vibration sensor 4 according to the fourth embodiment.
  • the vibration sensor 4 detects vibration of the object 90 by irradiating the object 90 (rough surface) with laser light and observing the reflected and scattered light.
  • the vibration sensor 4 includes a light-projecting unit 10a that irradiates the object 90 with laser light, a light-receiving unit 40a that receives the reflected and scattered light generated by the object 90 irradiated with the laser light, and an image processing device 70 as an information processing device that detects vibrations based on a detection signal output from the light-receiving unit 40a.
  • the light projecting unit 10a and the light receiving unit 40a are housed in the light projecting/receiving head 5 (for example, in a single housing).
  • the figure shows the coordinate axes of an X'YZ' Cartesian coordinate system as a first coordinate system used to explain the light-projecting unit 10a.
  • the figure also shows the coordinate axes of an XYZ Cartesian coordinate system as a second coordinate system used to explain the light-receiving unit 40a, the target object 90, and the observation surface 92.
  • the central ray of the laser light emitted from the light-projecting unit 10a is parallel to the Z' axis
  • the central ray of the light received by the light-receiving unit 40a is parallel to the Z axis.
  • the Y axis is the coordinate axis normal to a plane containing the Z' axis and the Z axis.
  • the X' axis is the coordinate axis perpendicular to both the Y axis and the Z' axis.
  • the X axis is the coordinate axis perpendicular to both the Y axis and the Z axis.
  • the light-projecting unit 10a has a laser light source 20 and a light-projecting optical system 30a that projects the laser light emitted from the laser light source 20 onto the object 90 as a line spot 91a.
  • the light-receiving unit 40a has a line sensor 50a and a light-receiving optical system 60a that focuses the reflected and scattered light of the laser light irradiated onto the object 90 onto the line sensor 50a (i.e., onto the light-receiving surface of the line sensor 50a).
  • the image processing device 70 calculates the amount of movement between frames of the speckle pattern generated in the reflected and scattered light received by the line sensor 50a, and estimates (i.e., calculates) the vibration of the object 90 based on this amount of movement.
  • the light-projecting unit 10a and the light-receiving unit 40a are arranged so that the first optical axis 11, which is the optical axis of the light-projecting unit 10a, and the second optical axis 41, which is the optical axis of the light-receiving unit 40a, intersect on the target object 90.
  • the light-projecting unit 10a and the light-receiving unit 40a are arranged so that the first direction (X direction) in which the line sensor 50a extends (i.e., the light-receiving surface of the line sensor 50a extends) is the same as the direction in which the linear spot 91a extends.
  • the optical axis of the light-projecting unit 10 may be the axis of the laser light emitted from the light-projecting unit 10. Furthermore, the optical axis of the light-receiving unit 40 may be the axis of the reflected and scattered light that can be received by the line sensor 50.
  • the light receiving optical system 60a is asymmetric in the X direction, which is a first direction, and in the Y direction, which is a second direction perpendicular to the X direction (i.e., axially asymmetric about the X and Y axes).
  • the X direction which is the longitudinal direction of the line sensor 50a (i.e., the longitudinal direction of the light receiving surface of the line sensor 50a)
  • the image of the object 90 i.e., image 93 of the linear spot 91a
  • the light receiving optical system 60a is not focused on the light receiving surface of the line sensor 50a.
  • the image of the object 90 i.e., image 93 of the linear spot 91a
  • the light receiving optical system 60a is focused on the light receiving surface of the line sensor 50a.
  • the light-projecting unit 10a and the light-receiving unit 40a are arranged side by side in the X direction (or X' direction). It is also preferable that the light-projecting optical system 30a includes a spot changing mechanism 35 that changes the size of the linear spot 91a in the X direction.
  • the projection optical system 30a includes an X-direction beam width conversion element 34, which is a set of two cylindrical lenses 32, 33 that form the linear spot 91a.
  • the projection optical system 30a includes a concave cylindrical lens 32 as an asymmetric optical system.
  • the X-direction beam width conversion element 34 is an optical system (e.g., a lens or lens group) that can change the X-direction width (length Bx) of the laser light emitted from the laser light source 20.
  • the light projecting unit 10a also has a collimating lens 31.
  • the spot changing mechanism 35 which changes the size of the linear spot 91a in the Y direction, is a mechanism for adjusting (e.g., manually) the distance Lc between the light emitting point of the laser light source 20 and the collimating lens 31.
  • Figure 22(A) is a schematic side view (i.e., a view of the light-projecting unit 10a viewed in the X' direction) showing the configuration and main light rays of the light-projecting unit 10a of the vibration sensor 4 according to embodiment 4.
  • Figure 22(B) is a schematic plan view (i.e., a view of the light-projecting unit 10a viewed in the -Y direction) showing the configuration and main light rays of the light-projecting unit 10a of the vibration sensor 4.
  • the first optical axis 11 of the light-projecting unit 10a and the second optical axis 41 of the light-receiving unit 40a intersect on the object 90. It is desirable to provide a mechanism for adjusting the direction of the first optical axis 11 of the light-projecting unit 10a or the direction of the second optical axis 41 of the light-receiving unit 40a so that the first optical axis 11 of the light-projecting unit 10a and the second optical axis 41 of the light-receiving unit 40a intersect even if the distance from the vibration sensor 4 to the object 90 changes.
  • Figures 22(A) and (B) show a beam emitted from a single point on the laser light source 20.
  • the laser light source 20 is, for example, a semiconductor laser.
  • the beam (laser light) emitted from the semiconductor laser has a divergence.
  • the beam is converted into a roughly parallel beam by the collimating lens 31.
  • the parallel beam is then converted into a beam that diverges in the X' direction by the X-direction beam width conversion element 34, which serves as a beam width conversion unit installed downstream of the collimating lens 31, and is irradiated onto a distant object 90 as a linear spot 91a extending in the X direction.
  • the collimating lens 31 is finely adjusted back and forth in the optical axis direction (i.e., the Z' direction) using the spot changing mechanism 35, thereby adjusting the Y-direction width of the linear spot 91a on the object 90 to be minimized.
  • the beam is focused in the Y direction on the object 90, which is located a finite distance from the laser light source 20.
  • the target object 90 is assumed to be located at a distance ranging from several tens of centimeters to approximately 10 meters from the vibration sensor 4.
  • an example of the configuration of the X-direction beam width conversion element 34 has a cylindrical lens 32 which is a concave lens and a cylindrical lens 33 which is a convex lens.
  • 2 in the X direction.
  • the width of the light beam can be converted into a collimated beam of any width.
  • the light is focused at a finite position in the Y direction, so the light beam emitted from the collimator lens 31 is not collimated light but a weakly converging light beam, and the lens spacing at which the collimated light is emitted is slightly different from the value described above.
  • the X-direction beam width conversion element 34 can make the beam width in the X' direction on the object 90 (i.e., length Bx) different from the length in the Y direction (i.e., make it axially asymmetric).
  • the laser light irradiated on the object 90 is focused in the Y direction to form a linear spot 91a with length Bx in the X direction.
  • Figure 23(A) is a schematic side view (i.e., a view of the light receiving unit 40a in the X direction) showing the configuration and main light rays of the light receiving unit 40a of the vibration sensor 4 in embodiment 4.
  • Figure 23(B) is a schematic plan view (i.e., a view of the light receiving unit 40a in the -Y direction) showing the configuration and main light rays of the light receiving unit 40a of the vibration sensor 4.
  • the light receiving unit 40a has a line sensor 50a, an imaging lens 61a, and a cylindrical lens 62.
  • the imaging lens 61a, the aperture 69, and the cylindrical lens 62 constitute the light receiving optical system 60a.
  • the imaging lens 61a is an object-side telecentric optical system or a hyper-telecentric optical system.
  • Figures 23(A) and (B) show an example in which the imaging lens 61a is an object-side telecentric optical system.
  • An object-side telecentric optical system is an optical system in which chief rays 96a-96d from each image height directed from the lens to the object are parallel to the second optical axis 41.
  • a hypercentric optical system is a special optical system in which chief rays 96a-96d from each image height directed from the lens to the object converge toward the second optical axis 41.
  • the surface of the object 90 is rough, and the reflected and scattered light from the linear spot 91a generates a speckle pattern throughout the entire space.
  • the points at both ends of the light receiving surface of the line sensor 50a in the X direction are P1 and P3, and the central point is P2.
  • Figures 23(A) and (B) depict the light rays that are reflected and scattered on the object 90 and reach points P1, P2, and P3.
  • the imaging lens 61a of the light receiving unit 40a focuses the speckle pattern on the observation surface 92.
  • the speckle pattern that appears on the observation surface 92 is transferred to the light receiving surface of the line sensor 50a.
  • the focal position on the object side in the Y direction can be moved from the observation surface 92 to the target object 90 that is located far away.
  • the focal length of the cylindrical lens 62 is f62
  • the distance between the cylindrical lens 62 and the observation surface 92 is L62 .
  • f62 -50 mm.
  • L62
  • 50 mm
  • the focus will be at infinity in the Y direction. If L62 is made slightly larger than 50 mm, the focus can be adjusted to a point closer than infinity.
  • the focus in the Y direction is adjusted on the object 90 using a spot position adjustment mechanism 64 that adjusts the Z direction position of the cylindrical lens 62 depending on the distance to the object 90.
  • the line sensor 50a and the object 90 are at conjugate positions in the Y direction. Therefore, light reflected and scattered from the object 90 is efficiently propagated in the Y direction to the line sensor 50a.
  • an image 93 of the linear spot 91a narrow in the Y direction is irradiated onto the line sensor 50.
  • This allows reflected and scattered light from the object 90 to be efficiently transmitted to the line sensor 50, making it possible to function as a vibration sensor even with weak laser light. If the spot irradiated onto the object 90 is circular and wide in the Y direction, only a wide beam can be focused onto the line sensor 50 in the Y direction, resulting in a large amount of light leaking outside the line sensor 50.
  • Figures 24(A) to (C) show the overlap of the light receiving surface of line sensor 50a and the speckle pattern.
  • the image 93 of the linear spot 91a of object 90 on the surface of line sensor 50a has a narrow width in the Y direction.
  • the reflected scattered light is focused on the light receiving surface of line sensor 50a in the Y direction.
  • Figures 24(A) to (C) show an example of the image 93 of the linear spot 91a projected onto the surface of line sensor 50a. In this way, the image 93 of the linear spot 91a has a narrow width in the Y direction and is elongated in the X direction.
  • the image 93 of the linear spot 91a has a brightness distribution in the X direction depending on the X-direction length Bx of the linear spot 91a.
  • Figure 24 (A) shows a state in which the light receiving surface of the line sensor 50a and the image 93 of the linear spot 91a overlap, and in this state, in embodiment 4, the vibration sensor 4 can operate normally.
  • An example of a spot position adjustment mechanism 63 is a moving stage for finely adjusting the cylindrical lens 62 in the Y direction. If the position of the light ray incident from the center of the cylindrical lens 62 is shifted in the Y direction, the beam's emission direction will be deflected. Therefore, by finely adjusting the cylindrical lens 62 in the Y direction, the position of the beam focused by the imaging lens 61a can be shifted in the Y direction. In other words, the state of Figure 24(B) can be adjusted to the state of Figure 24(A).
  • the spot position adjustment mechanism 63 can be adjusted so that the image 93 of the linear spot 91a can be received by the line sensor 50a.
  • a spot rotation adjustment mechanism 65 is a rotation stage for fine-tuning the cylindrical lens 62 around the Z axis.
  • the image 93 of the linear spot 91a rotates within the XY plane.
  • the method for adjusting the position of the image 93 of the linear spot 91a is not limited to the above example.
  • the image 93 of the linear spot 91a can be moved in the Y direction on the light receiving surface of the line sensor 50a.
  • a stage can be provided that shifts the line sensor 50a in the Y direction relative to the imaging lens 61a.
  • the method of spot rotation adjustment is not limited to the above example.
  • a mechanism may be provided that rotates the entire light receiving unit 40a around the Z axis.
  • a rotation stage may be provided that rotates the line sensor 50a around the Z axis relative to the imaging lens 61a.
  • the typical magnitude s a ' of the waveform of the speckle pattern is expressed as follows with respect to the shift amount ⁇ X between successive frames during vibration: 0.1 ⁇ s a ′ ⁇
  • the spot changing mechanism 35 is used to adjust the position of the collimator lens 31 in the Z-axis direction, thereby adjusting the size of the circular spot 91.
  • the spot changing mechanism 35 is not used, and the beam width adjusting mechanism 38 provided in the X-direction beam width converting element 34 can be used.
  • the beam width adjusting mechanism 38 provided in the X-direction beam width converting element 34 is an example of a spot changing mechanism.
  • the vibration sensor 4 according to the fourth embodiment, the linear spot 91a of the laser light emitted from the light-projecting unit 10a is focused in the Y direction on the object 90, and the light-receiving unit 40a is used to focus the reflected and scattered light of the linear spot 91a on the object 90 only in the Y direction and receive it with the line sensor 50a, thereby making it possible to receive light more efficiently than with conventional technology. Therefore, even when a laser light with a low power is used, it is possible to quickly acquire the one-dimensional waveform of the speckle pattern and detect vibrations.
  • the size of the linear spot 91a of the light projecting unit 10a on the object 90 can be changed only in the extension direction, which allows the size of the speckle pattern waveform received by the line sensor 50a to be changed. This allows the size of the speckle pattern to be optimized according to the magnitude of the vibration, improving the accuracy of vibration detection.
  • the size of the speckle pattern can be changed without changing the width of the line-shaped beam in the focusing direction. Because the size of the speckle pattern can be changed without changing the width of the line-shaped beam in the focusing direction, there is little loss of light intensity.
  • the non-axisymmetric optical system of the light receiving unit 40a includes a concave cylindrical lens, the size of the speckle pattern can be changed without changing the width of the line-shaped beam in the focusing direction.
  • the extension direction of the image 93 of the linear spot 91a i.e., the third direction in which the linear spot extends
  • the extension direction of the line sensor 50a are both the X direction, but the extension directions do not necessarily have to be the X direction as long as both extension directions are facing the same direction.
  • the extension direction is the X direction, there are the following advantages.
  • Figure 25 is a schematic plan view showing image shifts when the distance changes in the vibration sensor 4 according to embodiment 4.
  • Figures 26 (A) to (D) are schematic plan views showing image shifts when the distance changes in the vibration sensor 4 according to embodiment 4.
  • the extension direction of the image 93 of the linear spot 91a and the extension direction of the light receiving surface of the line sensor 50a are both the X direction.
  • embodiment 4 is the same as any of embodiments 1 to 3.
  • Vibration sensor 5: Light-emitting/receiving head, 10, 10a: Light-emitting unit, 11: First optical axis, 20: Laser light source, 30: Light-emitting optical system, 31: Collimating lens, 32: Cylindrical lens, 33: Cylindrical lens, 34: X-direction beam width conversion element, 35: Spot adjustment mechanism, 36: Position adjustment mechanism, 38: Beam width adjustment mechanism, 40, 40a, 40b: Light-receiving unit, 41: Second optical axis, 50: Area sensor (imaging sensor) , 50a line sensor (imaging sensor), 60, 60a light receiving optical system, 61, 61a imaging lens, 62 cylindrical lens, 63, 64 spot position adjustment mechanism, 65 spot rotation adjustment mechanism, 69 aperture, 70 image processing device, 90 object, 91 spot, 91a line spot, 92 observation surface, 93 spot image, X first direction, Y second direction, ⁇ tilt angle, ⁇ X shift amount (movement amount).

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  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Length Measuring Devices By Optical Means (AREA)

Abstract

L'invention concerne un capteur de vibrations (1) comprenant une unité de projection de lumière (10) qui comprend une source de lumière laser (20) et un système optique de projection de lumière (30) qui projette une lumière laser sur une cible (90), une unité de réception de lumière (40) qui comprend un capteur de formation d'image (50) et un système optique de réception de lumière (60) qui condense, sur le capteur de formation d'image (50), une lumière réfléchie et diffusée de la lumière laser émise au niveau de la cible, et un dispositif de traitement des images (70) qui calcule une quantité de mouvement, entre des trames, d'un motif de granularité généré dans la lumière réfléchie et diffusée reçue par le capteur de formation d'image (50), et mesure une vibration de la cible (90) sur la base de la quantité de mouvement : le système optique de projection de lumière (30) comprenant une lentille de formation d'image, et est focalisé sur un plan virtuel qui se trouve sur le côté objet et est plus proche que la cible, entre la cible (90) et le système optique de réception de lumière ; et le système optique de réception de lumière étant conçu de telle sorte que la valeur absolue (|ψ|) d'un angle (ψ) formé par un faisceau lumineux (96d) incident sur le côté le plus à l'extérieur d'une surface de réception de lumière du capteur de formation d'image (50) et un axe optique (41) de l'unité de réception de lumière est inférieure au demi-angle de cône (θNA) du flux de faisceau lumineux sur le côté objet, déterminé par l'ouverture numérique (NA) de la lentille de formation d'image.
PCT/JP2024/029141 2024-08-16 2024-08-16 Capteur de vibrations Pending WO2026038352A1 (fr)

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PCT/JP2024/029141 WO2026038352A1 (fr) 2024-08-16 2024-08-16 Capteur de vibrations

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PCT/JP2024/029141 WO2026038352A1 (fr) 2024-08-16 2024-08-16 Capteur de vibrations

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WO2026038352A1 true WO2026038352A1 (fr) 2026-02-19

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Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2001133320A (ja) * 1999-11-01 2001-05-18 Mitsubishi Heavy Ind Ltd 振動計測装置
JP4324507B2 (ja) * 2004-04-20 2009-09-02 浄史 松田 振動計測装置
JP2018503106A (ja) * 2014-12-27 2018-02-01 ガーディアン オプティカル テクノロジーズ リミテッドＧｕａｒｄｉａｎ Ｏｐｔｉｃａｌ Ｔｅｃｈｎｏｌｏｇｉｅｓ Ｌｔｄ． 表面振動を検出するためのシステムおよび方法
WO2023114535A1 (fr) * 2021-12-17 2023-06-22 Carnegie Mellon University Système, procédé et produit programme d'ordinateur pour la détection de vibration optique
JP7317794B2 (ja) * 2017-07-12 2023-07-31 ジェンテックス コーポレイション 環境から情報を取得するシステムおよび方法
CN116818081A (zh) * 2023-05-30 2023-09-29 厦门大学 一种收发一体非接触式激光散斑振动测量系统和方法

Patent Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2001133320A (ja) * 1999-11-01 2001-05-18 Mitsubishi Heavy Ind Ltd 振動計測装置
JP4324507B2 (ja) * 2004-04-20 2009-09-02 浄史 松田 振動計測装置
JP2018503106A (ja) * 2014-12-27 2018-02-01 ガーディアン オプティカル テクノロジーズ リミテッドＧｕａｒｄｉａｎ Ｏｐｔｉｃａｌ Ｔｅｃｈｎｏｌｏｇｉｅｓ Ｌｔｄ． 表面振動を検出するためのシステムおよび方法
JP7317794B2 (ja) * 2017-07-12 2023-07-31 ジェンテックス コーポレイション 環境から情報を取得するシステムおよび方法
WO2023114535A1 (fr) * 2021-12-17 2023-06-22 Carnegie Mellon University Système, procédé et produit programme d'ordinateur pour la détection de vibration optique
CN116818081A (zh) * 2023-05-30 2023-09-29 厦门大学 一种收发一体非接触式激光散斑振动测量系统和方法

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