A fiber-optic horizontal angle indicating device based on the principle of autocollimation and a method thereof

Abstract

The application discloses a fiber type horizontal angle indicating device based on a self-collimation principle and a method thereof, and relates to the technical field of horizontal angle indication.The device comprises a light source, a fiber weight module, a light intensity receiving module and a frame.The light source emits a space light which is coupled into the fiber weight module.The fiber weight module converts the direction of the incident light into a vertical downward direction and emits the light to a measured object.The measured object reversely couples the incident light into the fiber weight module.The fiber weight module emits the incident light to the light intensity receiving module.The light intensity receiving module converts the incident light into an electric signal.The frame is used for suspending the fiber weight module.The application is suitable for the installation and debugging process of high-end manufacturing equipment, measuring instruments and scientific test equipment, and provides high-sensitivity horizontal angle indication for the adjustment requirement of the spatial posture of a sensitive element and the high-precision level of the ground.

Description

Technical Field

[0001] This invention relates to the field of horizontal angle indication technology. Background Technology

[0002] Currently, absolute horizontal angle indication is usually achieved using three methods: level, electronic level, and horizontal liquid surface.

[0003] Among them, the level uses the principle of buoyancy to move vertically upwards, indicating the horizontal angle by measuring the offset position of the bubble in the sealed liquid. It has a simple structure, small size, and low cost, and has been widely integrated into instruments and tools. However, the level bubble or level ruler relies on visual judgment to determine whether it is level, and its accuracy is heavily dependent on the inspector. Moreover, the sensitivity of the instrument is limited, and it is difficult to exceed 0.01 mm / m (10 μrad).

[0004] Electronic levels utilize capacitive or inductive principles. The change in angle of a suspended sensitive element under gravity causes a change in electrical quantity, which in turn indicates the horizontal angle. The sensitivity of electronic levels is typically as low as 0.001 mm / m / μrad, meeting the general precision requirements of scientific research and industrial production.

[0005] In particular, researchers have proposed a photoelectric level, such as the PSD-based high-accuracy digital level proposed by Yuan Hongxing et al. of Nanjing University of Science and Technology [Journal of Instrumentation, 20(5), 517-518+544].

[0006] This level uses a suspended semiconductor laser with a counterweight as its light source. A two-dimensional PSD is placed on the surface to be measured to receive the position of the laser spot on the PSD surface, and the horizontal angle is reflected based on spatial geometry. Limited by the sensitivity of PSD devices at the time (1998) of only 10 μm, this method only achieved an accuracy of 9.25″, approximately 45 μrad. The key to this method is the optical axis parallel to the direction of gravity, which serves as the reference for measuring the horizontal angle. Gravity acts on the entire structure formed by the semiconductor laser and the counterweight, with its center of mass and a thin line forming a vertical line parallel to the direction of gravity. The shortcomings of this method are that the parallelism between the vertical line and the optical axis requires high-precision machining and adjustment between the counterweight and the thin line, and the machining and adjustment accuracy directly affects the direction of the optical axis. Furthermore, the large divergence angle of the semiconductor laser affects the PSD measurement accuracy, and adding collimating lenses and other optical path components increases the complexity of the device and introduces machining and adjustment errors. Therefore, this method still has certain problems.

[0007] The horizontal liquid surface method is currently the most accurate method for indicating horizontal angles. This method utilizes the center of the fluid in the container to form a horizontal reflective surface, indicating the horizontal angle through the principle of self-collimation. The advantage of this method lies in utilizing the fluid's fluidity, but it also increases system complexity. The ideal method is to use an open container, allowing light to be reflected directly from the liquid surface without passing through other devices. Currently, the best known reflective liquid is mercury, but mercury vapor is highly toxic to operators. Alternatively, special silicone oil can be used, but regardless of the liquid used, open containers inevitably experience spillage and evaporation, affecting usability. Another method is to use a closed container, but the manufacturing precision of the container window, such as flatness and parallelism, as well as liquid contamination of the inner surface, will affect measurement accuracy. For example, Jingsyan Torng et al. proposed a biaxial photoelectric horizontal measurement method based on a floating plane mirror on the liquid surface. Similarly, the scheme of setting the reflective plane on the upper surface of the liquid as a floating sphere also suffers from the above problems and requires consideration of spill prevention design, making the optomechanical structure more complex.

[0008] Another method, such as patent document CN1177240C published on November 24, 2004, discloses a method for processing fiber microlenses with center self-alignment function. This method involves suspending a plumb bob near the end of the fiber, with the fiber passing through the central micro-hole of the plumb bob, exposing a small portion of the fiber end and clamping it firmly, thus achieving center alignment function. However, it cannot guarantee that the center of mass of the plumb bob is collinear with the optical axis of the fiber, and therefore cannot guarantee the accuracy of the measurement. Summary of the Invention

[0009] This invention solves the problems of low accuracy and complex structure of existing absolute horizontal angle indication methods.

[0010] To achieve the above objectives, the present invention provides the following solution:

[0011] This invention provides a fiber optic horizontal angle indicator based on the self-collimation principle. The device includes a light source, a fiber optic counterweight module, a light intensity receiving module, and a frame.

[0012] The light source emits a beam of spatial light, which is coupled into the fiber optic weight module. The fiber optic weight module converts the direction of the incident light to vertically downward and emits it onto the surface of the object under test. The object under test reflects the incident light and then couples it back into the fiber optic weight module. The fiber optic weight module transmits the incident light to the light intensity receiving module, which converts the incident light into an electrical signal.

[0013] The frame is used to suspend the fiber optic weight module.

[0014] Furthermore, in a preferred embodiment, the aforementioned fiber optic counterweight module includes an optical fiber and a counterweight.

[0015] One end of the optical fiber is fixed to the upper frame of the frame, and the other end of the optical fiber is connected to the counterweight.

[0016] The optical fiber is used to receive spatial light and, under the action of the weight, converts the direction of the spatial light to vertically downward; at the same time, it receives the reflected light from the object under test and transmits it to the light intensity receiving module.

[0017] Furthermore, in a preferred embodiment, the optical fiber is implemented using any one of single-mode fiber, single-mode polarization-maintaining fiber, and multimode fiber.

[0018] Furthermore, in a preferred embodiment, the above-described device further includes a beam-splitting element;

[0019] The light source emits spatial light to the beam splitter, which couples the received spatial light into the fiber optic counterweight module and receives the return light from the fiber optic counterweight module, and transmits the return light to the light intensity receiving module.

[0020] Furthermore, in a preferred embodiment, the aforementioned beam splitter is implemented using a space optical element or a fiber optic element.

[0021] Furthermore, in a preferred embodiment, the aforementioned beam splitting element is implemented using any one of a non-polarizing beam splitting prism, a polarizing beam splitting prism with a quarter-wave plate, a 1x2 fiber beam splitter, and a circulator.

[0022] Furthermore, in a preferred embodiment, the above-described device further includes a reflector;

[0023] The reflector is fixed to the object under test and is used to receive the light emitted by the fiber optic weight module and reflect the incident light, and to couple the reflected light back to the fiber optic weight module.

[0024] Furthermore, in a preferred embodiment, the upper surface of the aforementioned reflector is a highly flat and highly reflective surface.

[0025] Furthermore, in a preferred embodiment, the upper surface of the aforementioned reflector may also be a high-reflectivity surface, and the lower surface has a high degree of parallelism with the upper surface;

[0026] The lower end of the aforementioned reflector can also be a three-point contact support with adjustable shape and height.

[0027] This invention also provides a fiber optic horizontal angle indication method based on the self-collimation principle. The method is implemented based on a fiber optic horizontal angle indication device based on the self-collimation principle described in any one of the preceding claims. The method is as follows:

[0028] Step 1: Use a fiber optic weight module to change the beam propagation direction to vertically downward and incident on the surface of the object to be tested or on the aforementioned reflector placed on the surface of the object to be tested.

[0029] Step 2: The object under test or a reflector placed on the surface of the object under test causes the incident beam to return and couple into the fiber optic counterweight module;

[0030] Step 3: The fiber optic weight module transmits the light beam to the light intensity receiving module. By adjusting the angle of the object under test, the object is considered horizontal when the light intensity received by the light intensity receiving module reaches its maximum value.

[0031] The beneficial effects of this invention are as follows:

[0032] 1. This invention provides a fiber optic horizontal angle indicating device based on the self-collimation principle. It uses an optical fiber as the connecting line for the weight, with gravity acting directly on the fiber's optical axis, straightening it and pointing it perpendicularly to the Earth's center, serving as a reference for high-precision horizontal angle measurement. The device utilizes reflection from the object being measured to form a self-collimated optical path, achieving high-precision horizontal angle indication. This avoids the problems of low accuracy and complex structure inherent in existing absolute horizontal angle indicating methods. Furthermore, this invention has high sensitivity, making it particularly suitable for high-precision horizontal angle indication applications with sensitivity below μrad.

[0033] This invention overcomes the biases of existing technologies:

[0034] This invention breaks with the conventional approach of using lasers as the reference for horizontal angle measurement, which requires a separate reference beam component in the horizontal angle indicating device. Instead, this invention proposes a new fiber optic horizontal angle indicating device based on the self-collimation principle, which can achieve horizontal angle indication without the need for a separate reference beam component, thus overcoming the bias of the prior art.

[0035] Furthermore, compared with the prior art, the present invention eliminates the component that generates the reference light, but still achieves horizontal indication and the indication result is more accurate. Therefore, it is an invention that saves on elements.

[0036] Furthermore, the present invention eliminates the component that generates the reference ray, which simplifies the structure and reduces the difficulty of processing and assembly.

[0037] Furthermore, since there is no component that generates a reference ray in this invention, the measurement principle is completely different from that of existing devices with reference rays. Therefore, this invention is an invention with a different concept from the prior art.

[0038] Furthermore, when connecting the weight to the optical fiber, it is crucial to ensure that the center of mass of the weight is collinear with the optical axis of the fiber, and that the fixing method does not cause deformation of the light. To address this issue, this invention sets the weight as a rotating structure and, based on the principle of center of gravity compensation, adds mass blocks to create a new, more uniform, and controllable mass distribution area around the fiber weight. This minimizes the offset between the line of action of gravity passing through the weight's center of gravity and the optical fiber axis. Simultaneously, by rationally distributing the mass blocks in a ring at different positions according to the actual center of gravity offset and controlling their embedding distance, the sum of the torques generated by these counterweights can balance the torques caused by the center of gravity offset, thereby gradually pulling the center of gravity back to the center of the optical axis. This ensures that the center of mass of the weight is collinear with the optical axis of the fiber, making the emitted light completely perpendicular to the horizontal plane. At the same time, the optical fiber is bonded to the weight without affecting the optical fiber.

[0039] 2. Existing high-accuracy digital levels using PSDs employ a semiconductor laser and a counterweight as a single unit. The center of mass of the counterweight and a thin string form a vertical line parallel to the direction of gravity, creating an optical axis parallel to the direction of gravity, which serves as a reference for horizontal angle measurement. However, achieving parallelism between the vertical line and the optical axis requires high-precision machining and adjustment between the counterweight and the thin string, and this precision directly affects the direction of the optical axis. This invention provides a fiber-optic horizontal angle indicating device based on the self-collimation principle. A weight is fixed to the end of the fiber optic cable to straighten the optical axis and make it vertically downwards towards the Earth's center, forming a ray of light parallel to the direction of gravity, serving as a reference for high-precision horizontal angle indication. Although both methods use a suspension scheme, their "suspension" differs fundamentally. The high-accuracy digital level using PSDs applies gravity to the center of mass of the laser, straightening the thin string suspending the laser, ensuring the laser light is vertically downwards. This scheme requires that the suspension point and centroid of the thin line be collinear with the laser's optical axis, i.e., the suspension point and centroid pass through the reverse extension of the laser's optical axis. Since the laser contains light-emitting diodes or chips, driver circuit boards, heat dissipation structures, and even optical components and fans, its centroid is difficult to estimate, thus requiring high-precision assembly and adjustment. The technical solution adopted in this invention only involves the optical fiber and a counterweight. Gravity acts on the centroid of the counterweight, straightening the optical fiber. The counterweight can be a rotating body precision-machined, with uniform material and ideal centroid; gravity directly straightens the optical fiber's optical axis, eliminating the need for high-precision assembly and adjustment between the thin line and the optical axis. Furthermore, apart from the counterweight, no other components are installed at the end of the optical fiber in this scheme, thus avoiding the impact of non-ideal assembly and adjustment of multiple components on measurement accuracy. This solves the problem in existing high-accuracy digital levels constructed using PSDs where the high-precision machining and assembly accuracy between the counterweight and the thin line affects the optical axis direction.

[0040] This invention is applicable to the installation and commissioning of high-end manufacturing equipment, measuring instruments, and scientific experimental equipment, providing a highly sensitive horizontal angle indication to meet the adjustment requirements of the spatial attitude of sensitive components and the high precision level of the ground. Attached Figure Description

[0041] Figure 1 This is a schematic diagram of a fiber optic horizontal angle indicator based on the self-collimation principle, as described in Embodiment 1.

[0042] Figure 2 This is a schematic diagram of the structure of a fiber optic horizontal angle indicator based on the self-collimation principle as described in Embodiment 2.

[0043] Figure 3 This is a schematic diagram of the fiber optic horizontal angle indicator device with added beam splitting element as described in Embodiment 4;

[0044] Figure 4 This is a schematic diagram of the fiber optic horizontal angle indicator device with added reflector as described in Embodiment 7.

[0045] Figure 5 This is a schematic diagram of the structure of the counterweight described in Embodiment 2;

[0046] Figure 6 This is a schematic diagram of the center of gravity of the counterweight in the three directions of the x, y, and z axes in the spatial coordinate system as described in Embodiment 2.

[0047] Figure 7 This is a cross-sectional view of the fiber optic counterweight as described in Embodiment 2;

[0048] Figure 8 This is a schematic diagram of the structure described in Embodiment 2, which uses a mass block for center of gravity adjustment and compensation.

[0049] Among them, 1-light source, 2-fiber optic counterweight module, 21-fiber optic cable, 22-counterweight, 210-splitter element, 3-light intensity receiving module, 4-frame, 5-reflector. Detailed Implementation

[0050] The specific embodiments of the present invention will be further described in detail below with reference to the accompanying drawings and examples. The following examples will help those skilled in the art to further understand the present invention, but do not limit the present invention in any way. It should be noted that those skilled in the art can make several changes and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention.

[0051] Implementation Method 1. See [link / reference] Figure 1This embodiment describes a fiber optic horizontal angle indicator based on the self-collimation principle. The device includes a light source 1, a fiber optic counterweight module 2, a light intensity receiving module 3, and a frame 4.

[0052] The light source 1 emits a beam of spatial light, which is coupled into the fiber optic weight module 2. The fiber optic weight module 2 converts the direction of the incident light to vertically downward and emits it onto the surface of the object to be tested. The object to be tested reflects the incident light and then couples it back into the fiber optic weight module 2. The fiber optic weight module 2 emits the incident light into the light intensity receiving module 3, which converts the incident light into an electrical signal.

[0053] The frame 4 is used to suspend the fiber optic weight module 2.

[0054] In practical applications, this implementation method, such as Figure 1 As shown, light source 1 emits a beam of spatial light, which is coupled into the fiber optic weight module 2. The fiber optic weight module 2 converts the direction of the incident light to vertically downward, forming a spatial optical axis parallel to the direction of gravity, serving as a reference for high-precision horizontal angle indication. The vertically downward light emitted from the fiber optic weight module 2 is incident on the surface of the object under test. The object under test reflects the incident light, which is then coupled back into the fiber optic weight module 2. That is, when the reflective surface of the object under test is perpendicular to the optical axis, a self-collimating structure is formed, and the reflected Gaussian beam returns along the incident optical axis. At this time, the light intensity coupled into the fiber is at its maximum, serving as the zero point for high-precision horizontal angle indication. The fiber optic weight module 2 transmits the returned light to the light intensity receiving module 3. The light intensity receiving module 3 converts the received light intensity into an electrical signal. That is, while adjusting the angle of the object under test, the position of the horizontal angle indicated by the maximum light intensity can be obtained by observing the electrical signal of the light intensity receiving module. The frame 4 is used to suspend the fiber optic weight module 2, so that the direction of the fiber optic weight module 2 is vertically downward. That is, one end of the fiber optic weight module 2 is fixed on the frame and the other end is suspended in the air. Under the action of gravity, the direction of the spatial light emitted by the light source is converted to vertically downward, forming a spatial optical axis parallel to the direction of gravity, which solves the problems of low accuracy and complex structure of the existing absolute horizontal angle indication method.

[0055] This embodiment provides a fiber optic horizontal angle indicating device based on the self-collimation principle. A light source couples spatial light into a fiber optic weight module. Under the action of a frame, the fiber optic weight module converts the direction of the incident light to vertically downward, forming a spatial optical axis parallel to the direction of gravity, serving as a reference for horizontal angle measurement. Spatial light emitted from the fiber optic weight module is incident on the surface of the object being measured. The object reflects the incident light, which is then coupled back into the fiber optic weight module. When the object is horizontal, a self-collimation structure is formed, at which point the light intensity coupled into the fiber is at its maximum, serving as the zero point for high-precision horizontal angle indication. The fiber optic weight module then transmits the returned light to a light intensity receiving module, which converts the received light intensity into an electrical signal. Thus, the position of the horizontal angle indicated by the maximum light intensity can be obtained through the light intensity receiving module. This solves the problems of low accuracy and complex structure in existing absolute horizontal angle indicating methods.

[0056] Implementation Method 2. See also Figure 2 , Figures 5 to 8 This embodiment is described by way of example of the fiber optic counterweight module 2 in a fiber optic horizontal angle indicator device based on the self-collimation principle described in Embodiment 1. One end of the fiber optic 21 is fixed on the upper frame of the frame 4, and the other end of the fiber optic 21 is connected to the counterweight 22.

[0057] The optical fiber 21 is used to receive spatial light, and under the action of the weight 22, it converts the direction of the spatial light to vertically downward and emits it. At the same time, it receives the return light reflected back from the object under test, and then transmits the return light to the light intensity receiving module 3.

[0058] In practical applications, this implementation method, such as Figure 2 As shown, frame 4 is used to suspend fiber optic weight module 2. One end of fiber optic 21 is fixed to any side of frame 4, while weight 22 is fixed to the other end of fiber optic 21. This makes the direction of fiber optic 21 vertically downward, pointing towards the center of the earth, under the action of weight 22 and frame 4. That is, the weight at the end of fiber optic 21 straightens the optical axis of fiber optic 21 and makes it vertically downward, pointing towards the center of the earth. The spatial optical axis emitted by it serves as the reference for high-precision horizontal angle indication. Spatial light emitted by light source 1 is coupled into the upper end of fiber optic 21. Weight 22 is connected to the lower end of fiber optic 21. The light beam emitted from the lower end of fiber optic 21 is incident on the surface of the object to be measured and is reflected. The light beam returning from the object to be measured is coupled into fiber optic 21 from the lower end and then emitted from the upper end of fiber optic 21 to light intensity receiving module 3. Light intensity receiving module 3 converts the incident light into an electrical signal, and the maximum light intensity indicated by the electrical signal indicates the horizontal angle position.

[0059] This embodiment provides a fiber optic horizontal angle indicator based on the self-collimation principle. The fiber optic weight module 2 is connected to the frame 4 via fiber optic cable 21. The fiber optic end face from the connection point between the fiber and the frame to the weight side is the key part for horizontal angle indication. The spatial beams of the light source 1 and the light intensity receiving module 3 are coupled to the fiber optic cable 21 through the upper end, i.e., the "free end" ignoring gravity. Therefore, the light source 1 can be directly connected to the frame 4 or not; similarly, the light intensity receiving module 3 can be directly connected to the frame 4 or not. Furthermore, the connections between the light source 1, the light intensity receiving module 3, and the frame 4 are independent. This avoids the heat generated by the light source and the light intensity receiving module affecting certain high-precision application environments. In practical applications, the connection between the fiber optic cable 21 and the frame 4 can be non-adjustable or adjustable. The height of the frame 4 can be non-adjustable or adjustable. The light source 1 and the light intensity receiving module 3 can be two independently operating photoelectric modules, or two parts of a shared power circuit within the same photoelectric module. The fiber optic weight 2 is connected to the frame 4 only through fiber optic cable 21, while the weight 22 has no other physical connection besides fiber optic cable 21. Since any physical connection, including fields such as magnetic fields and electric fields, will exert a force, the absence of any other physical connection besides fiber optic cable 21 ensures that no other forces influence the weight. That is, the weight is affected by two forces: gravity acting vertically downwards and air buoyancy acting vertically upwards. The tension in the fiber optic cable is opposite to these two forces, and its direction must be vertically upwards, ensuring the verticality of the fiber optic cable and its optical axis.

[0060] In application, the weight 22 has a through hole for inserting the optical fiber 21 and connecting to the lower end of the optical fiber 21, i.e., the "working end" straightened by gravity. Specifically, it can be connected to the sheath, cladding, or outer wall of the fiber core of the optical fiber 21. The center of mass of the weight 22 coincides with the axis of the portion of the optical fiber 21 inserted into the through hole. The center of mass of the weight 22 can be adjustable. The frame 4 can be placed on the object to be measured or on the ground next to the object. The frame 4 can be equipped with vibration isolation devices to isolate the optical fiber weight from interference by ground vibrations.

[0061] The connection between optical fiber 21 and counterweight 22 is achieved by adhesive bonding, which avoids generating lateral forces that affect the light output of the optical fiber and also avoids introducing complex connection mechanisms.

[0062] Gravity's vertical downward force is a recognized natural phenomenon and a common benchmark for various principles in the field of horizontal angle measurement. However, compared to existing suspended horizontal angle measurement technologies, this implementation method directly utilizes optical fiber as the suspension rope, reducing the impact of the suspended object on measurement accuracy through the simplest structure of the optical fiber and the weight, and the bonding method.

[0063] In this embodiment, to ensure that the center of mass of the weight is collinear with the optical axis of the optical fiber, the weight is configured as a rotating body structure, such as... Figure 5As shown, since the weight is made of a single material, there may be subtle density variations during manufacturing; that is, the material density is not absolutely uniform but spatially dependent. Furthermore, the weight is a toroidal body of revolution, and its outer cylindrical profile and inner hole are not ideal cylindrical surfaces, and their positions are not absolutely coaxial. Therefore, the actual center of gravity of the weight is necessarily not on its ideal axis. Figure 6 As shown, for a cylindrical hammer, this embodiment focuses on the x, y, and z axes in the spatial coordinate system. For objects with continuously distributed mass, this embodiment uses integration to calculate the position of the center of gravity.

[0064]

[0065] in, Coordinates representing the center of gravity, For position Density at that location It is a volumetric infinitesimal element.

[0066] In practical applications, material density often requires complex testing methods to determine, and calculating the micro-elements at various points is quite tedious. This embodiment provides a simple and effective compensation method, specifically:

[0067] The principle of center of gravity compensation is employed to minimize the offset between the line of action of gravity passing through the center of gravity of the weight and the fiber optic axis. Assuming a geodetic coordinate system exists in space, with the z-axis parallel to the direction of gravity, and the fiber optic axis coinciding with the z-axis, it is desirable for the center of gravity to be at any position along the z-axis. Due to factors such as material inhomogeneity, cylindricity errors, and internal hole position errors, it is difficult for the center of gravity of a directly machined weight to be at its geometric center; therefore, center of gravity compensation is necessary. Since the position of the center of gravity along the z-axis does not affect the effectiveness of this invention, the compensation process can be simplified to a planar problem, such as... Figure 7 As shown, a cross-sectional view of the fiber optic counterweight is directly presented. The origin of the coordinate system is at the center of the fiber axis, i.e., the desired center of gravity. The x-axis and y-axis are defined as two mutually perpendicular directions passing through the origin. Multiple uniformly distributed mass blocks with adjustable axial directions are used for center of gravity adjustment and compensation. One typical implementation example is... Figure 8 As shown, mass blocks 1, 2, and 3 are evenly distributed in a ring at different positions along the axial direction of the fiber optic counterweight.

[0068] Let the mass of the fiber optic weight be... The masses of the newly added mass blocks 1, 2, and 3 are respectively... , and And the distance from the centroid of the optical axis is , and The original center of gravity deviated from the center of the optical axis by a distance of 1 / 3. In the x, y coordinate system of the fiber optic counterweight profile, the position coordinates of the centroids of the three newly added mass blocks can be simplified as follows: , and The original center of gravity was .

[0069] The components of the resultant torque generated by the newly added mass block on the x-axis and y-axis are:

[0070]

[0071]

[0072] The new center of gravity coordinates of the fiber optic weight after the addition of the new mass block This can be expressed by the following formula:

[0073]

[0074]

[0075] The new centroid coordinates are at a distance from the center of the optical axis (i.e., the origin). It can be represented as:

[0076]

[0077] As can be seen, due to the ring-shaped distribution of the newly added mass blocks, the overall center of gravity is affected by the newly added, position-adjustable mass blocks. The overall center of gravity can be adjusted to coincide with the desired optical axis, or the deviation value can be kept from affecting the implementation effect of the present invention.

[0078] In practice, the precise location of the center of gravity of a fiber optic counterweight structure is difficult to determine, requiring gradual approximation to obtain a reasonable mass and distribution. Specifically, with a certain level of machining accuracy, the center of gravity offset is relatively small. The evenly distributed holes can be designed as threaded holes, using screws or threaded structures. The holes and mass blocks are considered as an adjustment unit (containing at least two or more adjustment units, and they are non-coaxial). Simple yet effective fine-tuning is achieved by changing the position of homogeneous counterweights of different masses. That is, based on the principle of torque balance, let the mass be... The distance from the mass block to the desired center of gravity is The torque generated by the mass block at its center of gravity is:

[0079]

[0080] From this formula, it can be seen that when the mass is constant, embedding a mass block near the desired center of gravity will result in a lever arm... Shorter, generating torque A smaller mass has a weaker effect on correcting the center of gravity; however, embedding a mass block at a position far from the desired center of gravity increases the lever arm. The longer the length, the more torque it generates. It is relatively large, and has a strong corrective effect on the center of gravity. At the same time, the mass... Larger mass blocks have a stronger effect on correcting the center of gravity. By rationally distributing mass blocks in a ring at different positions according to the actual center of gravity offset and controlling the embedding distance, the sum of the torques generated by these counterweights can balance the torques caused by the center of gravity offset, thereby gradually pulling the center of gravity back to the position of the optical axis center.

[0081] Finally, after adjusting with screws, a torque analysis can be performed again to verify whether the center of gravity has been correctly adjusted. Torque balance means that the sum of the torques in all directions is zero. Simultaneously, dynamic tests, such as rotation or tilting, can be used to check stability and balance. If the center of gravity is not in the expected position, i.e., it is offset from the fiber optic axis, then additional or repositioned counterweight screws are needed.

[0082] Implementation Method 3. This implementation method is an example of the optical fiber 21 in the optical fiber horizontal angle indicator device based on the self-collimation principle described in Implementation Method 2. The optical fiber 21 is implemented using any one of single-mode optical fiber, single-mode polarization-maintaining optical fiber, and multimode optical fiber.

[0083] Implementation Method Four. See also Figure 3 This embodiment is described in the first embodiment, which is based on a fiber optic horizontal angle indicator based on the self-collimation principle, with the addition of a beam splitter element 210.

[0084] The light source 1 emits spatial light to the beam splitter 210. The beam splitter 210 is used to couple the incident light into the fiber optic counterweight module 2, and also to receive the incident light from the fiber optic counterweight module 2 and couple the incident light into the light intensity receiving module 3.

[0085] In practical applications, this implementation method, such as Figure 3 As shown, spatial light emitted from light source 1 is coupled into the upper end of optical fiber 21 through beam splitter 210. A weight 22 is connected to the lower end of optical fiber 21. The beam emitted from the lower end of optical fiber 21 enters the object under test. The beam returning from the object under test is coupled back into the optical fiber from the lower end of optical fiber 21. Spatial light emitted from the upper end of the optical fiber passes back through beam splitter 210 and is finally transmitted to light intensity receiving module 3. Beam splitter 210 transforms optical fiber 21 from a two-port element to a three-port element, which facilitates the coupling of spatial light into optical fiber 21 and the transmission of return light from optical fiber 21 to light intensity receiving module 3.

[0086] Implementation Method 5. This implementation method is an example of the beam splitting element 210 in the fiber optic horizontal angle indicator based on the self-collimation principle described in Implementation Method 4. The beam splitting element 210 is implemented using a spatial optical element or a fiber optic element.

[0087] In practical applications, the beam splitter 210 can be a space optical element or an optical fiber element; when it is an optical fiber element, the beam splitter 210 is an optical fiber element that is connected to the optical fiber 21 via a flange or integrated via optical fiber welding.

[0088] Implementation Method Six. This implementation method illustrates the beam splitting element 210 in a fiber optic horizontal angle indicator based on the self-collimation principle described in Implementation Method Four. The beam splitting element 210 is implemented using any one of the following: a non-polarizing beam splitting prism, a polarizing beam splitting prism with a quarter-wave plate, a 1x2 fiber beam splitter, and a circulator.

[0089] In practical applications, the beam splitter 210 can be any one of the following: a non-polarizing beam splitter prism, a polarizing beam splitter prism with a quarter-wave plate, a 1x2 fiber beam splitter, and a circulator. Correspondingly, the light source 1 can emit spatial light or be an integrated pigtail with light directly output from the optical fiber. When the beam splitter 210 is an optical fiber element, the integrated pigtail light source 1 can be connected to the beam splitter 210 via an optical fiber flange or direct fusion splicing.

[0090] Implementation Method Seven. See also Figure 4 This embodiment is based on the fiber optic horizontal angle indicator based on the self-collimation principle described in Embodiment 1, with the addition of a reflector 5. The reflector 5 is placed on the object to be measured and is used to receive the light emitted by the fiber optic weight module 2 and to couple the incident light back to the fiber optic weight module 2.

[0091] In practical applications, the spatial light emitted by the light source 1 is coupled into the upper end of the optical fiber 21, and the weight 22 is connected to the lower end of the optical fiber 21. The light beam emitted from the lower end of the optical fiber 21 is incident on the reflector 5 placed on the surface of the object to be measured. The light beam returning from the reflector 5 is coupled back into the optical fiber 21 from the lower end, and then emitted from the upper end of the optical fiber 21 to the light intensity receiving module 3. The reflector 5 can be used when the upper surface of the object to be measured is a non-high reflectivity plane.

[0092] Implementation Method 8. This implementation method is an example of the reflector 5 in the fiber optic horizontal angle indicator based on the self-collimation principle described in Implementation Method 7. The upper and lower surfaces of the reflector 5 are both parallel plates with high flatness and high parallelism.

[0093] In practical applications, when the object to be measured is a plane, such as a transmissive plane, a diffuse reflection plane, or a low reflectivity plane, the substrate of the reflector 5 can be a parallel plate with high flatness and high parallelism on both the upper and lower surfaces.

[0094] Implementation Method Nine. This implementation method is an example of the reflector 5 in the fiber optic horizontal angle indicator device based on the self-collimation principle described in Implementation Method Seven. The upper surface of the reflector 5 can also be a high reflectivity surface.

[0095] The lower end of the reflector 5 can also be a three-point contact support with adjustable shape and height.

[0096] In practical applications, the upper surface of the reflector 5 is a high-reflectivity surface, and the lower surface of the reflector 5 directly contacts the object under test or is fitted with a fixed-height support foot that makes three-point contact with the object under test. When the object under test is non-planar, the base shape of the reflector 5 can be a shape that fits the object under test, or it can be a three-point contact support foot whose height can be adjusted according to the shape of the object under test.

[0097] Implementation Method 10. This implementation method provides a fiber optic horizontal angle indication method based on the self-collimation principle. The method is implemented based on a fiber optic horizontal angle indication device based on the self-collimation principle described in any one of Implementation Methods 1 to 10. The method is as follows:

[0098] Step 1: Use a fiber optic weight module to change the beam propagation direction to vertically downward and incident on the surface of the object to be tested or the aforementioned reflector placed on the surface of the object to be tested.

[0099] Step 2: The object under test or a reflector placed on the surface of the object under test causes the incident beam to return and couple into the fiber optic counterweight module;

[0100] Step 3: The fiber optic weight module transmits the light beam to the light intensity receiving module. By adjusting the angle of the object under test, the object is considered horizontal when the light intensity received by the light intensity receiving module reaches its maximum value.

[0101] In practical applications, this embodiment uses a fiber optic weight module to direct the spatial light vertically downwards onto the surface of the object under test, using an optical axis parallel to the direction of gravity as the reference for high-precision horizontal angle indication. The object under test reflects the incident light and couples it back into the fiber optic weight module; that is, when the reflective surface of the object is perpendicular to the optical axis, a self-collimating structure is formed, and the reflected Gaussian beam returns along the incident optical axis. At this point, the light intensity coupled into the fiber is at its maximum, serving as the zero point for high-precision horizontal angle indication. The fiber optic weight module transmits the returned light to a light intensity receiving module. The light intensity receiving module converts the received returned light intensity into an electrical signal; that is, the position of the horizontal angle indicated by the maximum light intensity can be obtained by observing the electrical signal.

[0102] The above description is merely an embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of the claims of the present invention.

Claims

1. A fiber optic horizontal angle indicating device based on the self-collimation principle, characterized in that, The device includes a light source (1), an optical fiber weight module (2), a light intensity receiving module (3), and a frame (4). The light source (1) emits a beam of spatial light, which is coupled into the fiber optic weight module (2). The fiber optic weight module (2) converts the direction of the incident light to vertically downward and emits it to the surface of the object to be tested. The object to be tested reflects the incident light and then couples it back to the fiber optic weight module (2). The fiber optic weight module (2) emits the incident light to the light intensity receiving module (3). The light intensity receiving module (3) converts the incident light into an electrical signal. The frame (4) is used to suspend the fiber optic weight module (2).

2. The fiber optic horizontal angle indicating device based on the self-collimation principle according to claim 1, characterized in that, The fiber optic counterweight module (2) includes an optical fiber (21) and a counterweight (22). One end of the optical fiber (21) is fixed to the upper frame of the frame (4), and the other end of the optical fiber (21) is connected to the counterweight (22). The optical fiber (21) is used to receive spatial light and, under the action of the weight (22), converts the direction of the spatial light to vertically downward. At the same time, it receives the reflected light from the object under test and transmits it to the light intensity receiving module (3).

3. The fiber optic horizontal angle indicating device based on the self-collimation principle according to claim 2, characterized in that, The optical fiber (21) is implemented using any one of single-mode optical fiber, single-mode polarization-maintaining optical fiber and multimode optical fiber.

4. The fiber optic horizontal angle indicating device based on the self-collimation principle according to claim 1, characterized in that, The device also includes a beam splitter (210). The light source (1) emits spatial light to the beam splitter (210), which is used to couple the received spatial light into the fiber optic weight module (2), and also to receive the return light from the fiber optic weight module (2) and transmit the return light to the light intensity receiving module (3).

5. A fiber optic horizontal angle indicating device based on the self-collimation principle according to claim 4, characterized in that, The beam splitter (210) is implemented using space optical elements or fiber optic elements.

6. A fiber optic horizontal angle indicating device based on the self-collimation principle according to claim 4, characterized in that, The beam splitting element (210) is implemented using any one of the following: a non-polarizing beam splitting prism, a polarizing beam splitting prism with a quarter-wave plate, a 1x2 fiber beam splitter, and a circulator.

7. A fiber optic horizontal angle indicating device based on the self-collimation principle according to claim 1, characterized in that, The device also includes a reflector (5); The reflector (5) is fixed on the object to be tested and is used to receive the light emitted by the fiber optic weight module (2) and reflect the incident light, and is used to couple the reflected light back to the fiber optic weight module (2).

8. A fiber optic horizontal angle indicating device based on the self-collimation principle according to claim 7, characterized in that, The upper surface of the reflector (5) is a highly reflective surface with high flatness.

9. A fiber optic horizontal angle indicating device based on the self-collimation principle according to claim 7, characterized in that, The upper surface of the reflector (5) is a high reflectivity surface, and the lower surface has a high degree of parallelism with the upper surface; The lower end of the reflector (5) is a three-point contact support with adjustable shape and height.

10. A fiber optic horizontal angle indication method based on the self-collimation principle, characterized in that, The method is implemented based on a fiber optic horizontal angle indicating device based on the self-collimation principle as described in any one of claims 1-9, and the method is as follows: Step 1: Use the fiber optic weight module (2) to change the beam propagation direction to vertical downward and incident on the surface of the object to be measured or on the reflector placed on the surface of the object to be measured. Step 2: The object under test or a reflector placed on the surface of the object under test causes the incident beam to return and couple into the fiber optic counterweight module (2); Step 3: The fiber optic weight module (2) transmits the light beam to the light intensity receiving module (3). By adjusting the angle of the object to be measured, the object is considered horizontal when the light intensity received by the light intensity receiving module (3) reaches its maximum value.

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