Light beam direction change detection system and method based on PSD

Abstract

The invention discloses a PSD-based light beam direction change detection system and method in the technical field of intelligent detection, and the system comprises a light beam sensing module which is installed on the surface of an optical flat plate through a translation and lifting adjustment mechanism, a laser which is installed on the surface of the optical flat plate through an adjustable clamp, and a light beam detection module which is installed on the surface of the optical flat plate through an adjustable clamp. The reflector is fixed on the surface of a to-be-detected platform, the optical flat plate is fixed on the surface of the air floating platform, a PSD position sensitive detector in the light beam sensing module is electrically connected with a software processing end through a driving circuit, and a light beam emitted by the laser is reflected by the reflector to enter the PSD position sensitive detector in the light beam sensing module. The software processing end calculates the vibration angles of the platform to be detected in the vertical direction, the horizontal direction and the two-dimensional direction by collecting the change data of the light spot position in the PSD position sensitive detector. According to the invention, the vibration of an object can be rapidly measured, data recording can be carried out, and the change of reflected light beam pointing caused by various micro-vibrations of the optical reflector can be detected.

Description

Technical Field

[0001] The present invention relates to a PSD-based light beam pointing change detection system and method, belonging to the technical field of intelligent detection. Background Art

[0002] Currently, the degree of vibration of an object is determined by detecting the change in surface angle caused by the vibration. The main methods include using a portable digital laser vibrometer (PDV) and a Sony stacked lens (RS-CMOS) for detection.

[0003] PDV detection utilizes the Doppler effect, using the modulation of the speed of transmitted light by a vibrating object. Using an algorithm, it infers the object's velocity, converting it into relative displacement. This displacement is then converted into an angular change using a mathematical formula. The RS-CMOS method, on the other hand, leverages the principle of similar triangles and uses RS-CMOS position sensing devices to derive the relative displacement of the vibrating object. This is then converted into an angular change using a mathematical formula. However, both methods suffer from the following issues: they are prohibitively expensive, computationally complex, and unsuitable for mass production. Summary of the Invention

[0004] The purpose of the present invention is to overcome the shortcomings of the existing technology and provide a PSD-based light beam pointing change detection system and method for detecting the vibration angle and other data of an object during vibration. It has the advantages of low cost, simple operation, and suitability for long-term and long-distance detection and recording.

[0005] To achieve the above object, the present invention is implemented by adopting the following technical solutions:

[0006] In the first aspect, the present invention provides a PSD-based beam pointing change detection system, comprising a beam sensing module mounted on the surface of an optical plate through a translation and lifting adjustment mechanism, a laser mounted on the surface of the optical plate through an adjustable clamp, and a reflector fixed on the surface of a platform to be detected, wherein the optical plate is fixed on the surface of an air-floating platform, the PSD position sensitive detector in the beam sensing module is electrically connected to a software processing end through a driving circuit, the beam emitted by the laser is reflected by the reflector and enters the PSD position sensitive detector in the beam sensing module, and the software processing end calculates the vibration angles of the platform to be detected in the vertical, horizontal and two-dimensional directions by collecting change data of the light spot position in the PSD position sensitive detector.

[0007] Furthermore, the translation and lifting adjustment mechanism includes a lifting platform and a translation platform, the light beam sensing module is installed on the lifting platform, the lifting platform is installed on the translation platform, the translation platform is fixedly installed on the optical plate, and the light beam sensing module can move and adjust in the vertical and horizontal directions respectively under the adjustment of the lifting platform and the translation platform.

[0008] Furthermore, the beam sensing module includes a telephoto lens and a PSD position sensitive detector chip. The telephoto lens has a diameter of 80 mm and a focal length of 500 mm. The PSD position sensitive detector chip is fixed at the focus of the telephoto lens. The PSD position sensitive detector chip is a two-dimensional detector chip with a target surface size of 20*20 mm and a response wavelength range of 300-1100 nm.

[0009] Furthermore, the light source wavelength of the laser is within the wavelength response range of the PSD position sensitive detector chip, and the laser divergence angle is less than 1 mrad, and the maximum output power of the laser is less than the damage threshold of the PSD position sensitive detector chip.

[0010] Furthermore, the center height of the laser, the center height of the reflector and the center height of the beam sensing module are consistent.

[0011] In a second aspect, the present invention provides a method for detecting light beam pointing changes based on a PSD, based on the above-mentioned light beam pointing change detection system based on a PSD, comprising:

[0012] Fix the reflector on the surface of the platform to be tested;

[0013] Start the laser, adjust the adjustable clamp and the translation and lifting adjustment mechanism so that the light spot is reflected by the reflector at the center of the PSD position sensitive detector chip in the beam sensing module;

[0014] At the software processing end, the change data of the light spot position in the PSD position sensitive detector is collected to calculate the vibration angle of the platform to be detected in the vertical, horizontal and two-dimensional directions.

[0015] Furthermore, the vibration angles of the platform to be tested in the vertical, horizontal and two-dimensional directions are:

[0016]

[0017] Where Δθ x is the horizontal vibration angle, Δθ y is the vertical vibration angle, Δθ r is the vibration angle in the two-dimensional direction, ΔX is the horizontal displacement difference of the light spot on the PSD, ΔY is the vertical displacement difference of the light spot on the PSD, and f' is the focal length of the lens.

[0018] Furthermore, the software processing end collects the change data of the light spot position in the PSD position sensitive detector to calculate the vibration angles of the platform to be detected in the vertical, horizontal and two-dimensional directions. The software processing end also includes: when the light spot moves out of the PSD position sensitive detector chip, the software processing end records the last valid point (X1, Y1) of the light spot and the point (X2, Y2) where the light spot re-enters, and calculates the horizontal and vertical displacement differences on the PSD position sensitive detector chip during the light spot movement out period in combination with the horizontal and vertical time domain compensation functions, thereby calculating the horizontal and vertical vibration angles and the two-dimensional vibration angles of the light spot when it moves out of the PSD:

[0019]

[0020] Where: is the horizontal vibration angle of the light spot moving out of the PSD stage, is the vertical vibration angle of the light spot when it moves out of the PSD stage, is the vibration angle of the light spot in the two-dimensional direction when it moves out of the PSD stage, f' is the focal length of the lens, is the horizontal displacement difference on the PSD position sensitive detector chip during the light spot moving out period, is the vertical displacement difference on the PSD position sensitive detector chip during the light spot moving out period, φ(t), are the time domain compensation functions in the horizontal and vertical directions respectively.

[0021] Furthermore, the calculation expressions of the horizontal and vertical time domain compensation functions are:

[0022]

[0023] Where: x is the equivalent damping coefficient in the horizontal direction, ω x is the natural angular frequency of horizontal vibration, φ x is the horizontal phase offset angle, ξ y is the equivalent damping coefficient in the vertical direction, ω y is the natural angular frequency of vertical vibration, φ y is the vertical phase offset angle.

[0024] Furthermore, the calculation expressions of the equivalent damping coefficients in the horizontal and vertical directions are:

[0025]

[0026] Where: x n 、y n are the horizontal and vertical displacement amplitudes of the nth vibration cycle, respectively, and N is the number of attenuation cycles;

[0027] The calculation expressions of the horizontal and vertical vibration natural angular frequencies are:

[0028]

[0029] Where: T x 、T y are the horizontal and vertical vibration periods respectively;

[0030] The calculation expressions of the horizontal and vertical phase offset angles are:

[0031]

[0032] Where: X(t0) is the horizontal displacement of the light spot when it moves out of the PSD, is the horizontal velocity at the moment when the displacement disappears, Y(t0) is the vertical displacement of the light spot when it moves out of the PSD, is the vertical velocity at the moment when the displacement disappears.

[0033] Compared with the prior art, the present invention has the following beneficial effects:

[0034] 1. The PSD-based beam pointing change detection system and method provided by the present invention can quickly measure the magnitude of an object's vibration and record the data. This allows for detecting changes in the reflected beam's pointing direction caused by various micro-vibrations of an optical reflector. This system is low-cost and suitable for large-scale, long-term, and long-distance detection and recording.

[0035] 2. The present invention constructs a time-domain compensation function of the vibration trajectory through the dynamic correlation of data such as the vibration period and the horizontal displacement of the light spot at the moment it moves out of the PSD. It calculates the horizontal and vertical displacement differences on the PSD position sensitive detector chip during the light spot movement period, and finally obtains the horizontal and vertical vibration angles of the micro-vibration platform in the stage when the light spot moves out of the PSD, which solves the data fault problem of the traditional detection system and ensures the timing integrity of vibration monitoring. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] The accompanying drawings, which constitute part of the present invention, are intended to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are intended to explain the present invention and do not constitute an undue limitation of the present invention. In the accompanying drawings:

[0037] Figure 1 A schematic structural diagram of a PSD-based light beam pointing change detection system provided in Example 1 of the present invention;

[0038] Figure 2 A schematic diagram of the optical path of a PSD-based light beam pointing change detection system provided in Example 1 of the present invention;

[0039] Figure 3 A test diagram of a PSD-based light beam pointing change detection system provided in Example 1 of the present invention;

[0040] Figure 4 This is a schematic diagram of the interior of a beam sensing module of a PSD-based beam pointing change detection system provided in Example 1 of the present invention;

[0041] Figure 5 Schematic diagram of the displacement change of the light beam on the PSD chip of a PSD-based light beam pointing change detection system provided in Example 1 of the present invention.

[0042] In the figure: 1. Laser; 2. Adjustable clamp; 3. Reflector; 4. Beam sensing module; 5. Lifting platform; 6. Translation platform; 7. Optical plate; 8. Air floating platform; 9. Micro-vibration platform. DETAILED DESCRIPTION

[0043] The present invention will be described in detail below with reference to the accompanying drawings and in combination with embodiments. It should be noted that, in the absence of conflict, the embodiments and features of the embodiments of the present invention can be combined with each other.

[0044] The following detailed description is an exemplary description and is intended to provide further detailed description of the present invention. Unless otherwise indicated, all technical terms used in the present invention have the same meaning as those generally understood by those skilled in the art to which the present invention belongs. The terms used in the present invention are only for describing specific embodiments and are not intended to limit the exemplary embodiments according to the present invention.

[0045] Example 1:

[0046] See also Figure 1 A PSD-based beam pointing change detection system, used to measure the vibration magnitude of an object and record data, includes: a laser 1, an adjustable clamp 2, a reflector 3, a beam sensing module 4, a lifting platform 5, a translation stage 6, an optical plate 7, an air-floating platform 8, and a micro-vibration platform 9. The laser 1 is used to generate a stable, fine laser beam; the adjustable clamp 2 is used to clamp the laser 1 and adjust the position of the light spot; the reflector 3 is fixed to the micro-vibration platform 9; the beam sensing module 4 is mounted on the lifting platform 5, which is used to adjust the initial vertical position of the light spot; the lifting platform 5 is fixed to the translation stage 6 and can perform precise horizontal movement with the translation stage 6. The lifting platform 5 and the translation stage 6 are used to adjust the initial position of the light spot of the reflected light beam incident on the beam sensing module 4; the translation stage 6 is mounted on the optical plate 7, which is fixed to the air-floating platform 8 to avoid interference caused by external vibrations and inaccurate measurement results.

[0047] The beam sensing module 4 includes a telephoto lens and a PSD position-sensitive detector chip. The telephoto lens has a diameter of 80mm and a focal length of 500mm. The PSD position-sensitive detector chip is fixed at the focus of the telephoto lens and electrically connected to the software processing end. It is used to accurately measure the position of the light spot on the PSD after the reflected light beam of the fine laser beam passes through the optical reflector. The PSD position-sensitive detector chip is a two-dimensional detector chip with a target surface size of 20*20mm and a response wavelength range of 300-1100nm. It is recommended to use a maximum range of ±8mm, a resolution of 1um, a linear accuracy of ±10um, an ideal linear measurement range of ±3mm, and a linear accuracy of 0.002mm within the ideal linear range.

[0048] The wavelength of laser 1 light source should be within the wavelength response range of the PSD position sensitive detector chip, the laser divergence angle should be less than 1mrad, and the maximum output power of laser 1 should be less than the damage threshold of the PSD position sensitive detector chip;

[0049] The center height of the laser 1, the center height of the reflector 3 and the center height of the beam sensing module 4 are consistent;

[0050] Please refer to Figure 2-5 This embodiment provides a method for detecting beam pointing changes based on PSD, comprising the following steps:

[0051] Step 1: Install the laser 1, adjustable holder 2, beam sensing module 4, lifting platform 5, translation platform 6, optical plate 7, and air floating platform 8 according to the measurement height to complete the construction of the measurement device;

[0052] Step 2: Fix the reflector 3 on the micro-vibration platform 9;

[0053] Step 3: Turn on the power of the laser 1, and adjust the adjustable holder 2, the lifting platform 5, and the translation stage 6 so that the light spot is reflected by the reflector 3 at the center of the PSD position sensitive detector chip in the beam sensing module 4;

[0054] Step 4: When the micro-vibration platform vibrates, it causes the reflector 3 to vibrate, causing the direction of the reflected light beam to change, thereby changing the position of the light spot incident on the PSD position-sensitive detector. The software processing end collects and calculates the light spot position change data to accurately measure the change in the reflected light beam's direction. Specifically, click Align on the software processing end, mark the current position of the light spot as the zero point, and calculate the relative position change between the light spot and the zero point to accurately measure the change in the reflected light beam's direction. Set an appropriate sampling frequency on the software processing end, turn on the micro-vibration platform 9, and use the software processing end to measure and record the position change of the light spot on the PSD until the entire measurement process is complete.

[0055] The software processing end is based on LabVIEW software programming. It can obtain the two-dimensional position coordinates (x, y) of the light spot according to the serial communication protocol of the PSD, calculate the displacement of the light spot in the horizontal and vertical directions (△x, △y), and then convert it into the pointing coordinates of the light beam (△θx, △θy). This can achieve accurate measurement of the change in the pointing direction of the reflected light beam. The data processing algorithm is as follows:

[0056] In the paraxial optical path of geometric optics, it is known that:

[0057]

[0058] Where y' is the image height, f' is the focal length of the lens, and according to the law of reflection of light, when light is reflected, the angle of incidence is equal to the angle of reflection. The above formula can be approximated as follows:

[0059]

[0060] Where Δθ x is the horizontal vibration angle, ΔX is the horizontal displacement difference of the light spot on the PSD;

[0061] Similarly, the angle of the light spot vibration in the vertical direction is:

[0062]

[0063] Where Δθ y is the vertical vibration angle, ΔY is the vertical displacement difference of the light spot on the PSD;

[0064] The angle of the light spot vibration in the two-dimensional direction is:

[0065]

[0066] Where Δθ r is the vibration angle in the two-dimensional direction, and Δr is the two-dimensional displacement difference of the light spot on the PSD.

[0067] It should be noted that during the vibration process, the amplitude may exceed the PSD detection range. When the light spot moves out of the PSD position sensitive detector chip, the software processing end records the last valid point of the light spot (X1, Y1) and the point where the light spot re-enters (X2, Y2). Combined with the horizontal and vertical time domain compensation functions, the horizontal and vertical displacement differences on the PSD position sensitive detector chip during the light spot movement period are calculated. The horizontal and vertical vibration angles of the light spot during the stage of moving out of the PSD, as well as the vibration angle in the two-dimensional direction, are calculated:

[0068]

[0069] Where: is the horizontal vibration angle of the light spot moving out of the PSD stage, is the vertical vibration angle of the light spot when it moves out of the PSD stage, is the vibration angle of the light spot in the two-dimensional direction when it moves out of the PSD stage, is the horizontal displacement difference on the PSD position sensitive detector chip during the light spot moving out period, is the vertical displacement difference on the PSD position sensitive detector chip during the light spot moving out period, and its expression is:

[0070]

[0071] Where: φ(t), are the time domain compensation functions in the horizontal and vertical directions respectively, and the expressions are:

[0072]

[0073] Where: x is the equivalent damping coefficient in the horizontal direction, ω x is the natural angular frequency of horizontal vibration, φ x is the horizontal phase offset angle, ξ y is the equivalent damping coefficient in the vertical direction, ω y is the natural angular frequency of vertical vibration, φ y is the vertical phase offset angle. According to the motion trajectory of the light spot in the effective detection area, the dynamic parameters are extracted by analyzing the vibration waveform characteristics. The calculation formula is as follows:

[0074] 1. Equivalent damping coefficient in horizontal and vertical directions

[0075]

[0076] Where: x n 、y n are the horizontal and vertical displacement amplitudes of the nth vibration cycle respectively; N is the number of attenuation cycles, usually 3-5 complete cycles.

[0077] 2. Horizontal and vertical vibration natural angular frequency

[0078]

[0079] Where: T x 、T y are the horizontal and vertical vibration periods respectively.

[0080] 3. Horizontal and vertical phase offset angles

[0081]

[0082] Where: X(t0) is the horizontal displacement of the light spot at the moment it moves out of the PSD; is the horizontal velocity at the moment when the displacement disappears; Y(t0) is the vertical displacement of the light spot when it moves out of the PSD; is the vertical velocity at the moment when the displacement disappears.

[0083] In summary, when the light spot exceeds the PSD detection range, the above scheme constructs a time-domain compensation function of the vibration trajectory through the dynamic correlation of data such as the vibration period and the horizontal displacement at the moment the light spot moves out of the PSD. This function is used to calculate the horizontal and vertical displacement differences on the PSD position-sensitive detector chip during the light spot movement period. Finally, the horizontal and vertical vibration angles of the micro-vibration platform and the vibration angle in the two-dimensional direction are obtained when the light spot moves out of the PSD. This solves the data gap problem of the traditional detection system and ensures the temporal integrity of vibration monitoring.

[0084] The PSD-based beam pointing change detection system provided by the present invention features simple equipment, low cost, long-distance detection capability, ease of operation, and high accuracy. It can rapidly measure the magnitude of an object's vibration and record the data, with a measurement range of ±0.916°, an accuracy of 0.00023°, and a repeatability of ±0.00011°. The present invention also provides a method for detecting small-angle changes in the reflected beam's pointing direction caused by various micro-vibrations in an optical reflector. This method offers the advantages of low cost and suitability for large-scale, long-term, and long-distance detection and recording.

[0085] It is understood from common technical knowledge that the present invention may be implemented by other embodiments that do not depart from its spirit or essential features. Therefore, the embodiments disclosed above are, in all respects, merely illustrative and not exclusive. All modifications within the scope of the present invention or equivalent to the scope of the present invention are intended to be encompassed by the present invention.

[0086] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit it. Although the present invention has been described in detail with reference to the above embodiments, ordinary technicians in the field should understand that the specific implementation methods of the present invention can still be modified or replaced by equivalents. Any modification or equivalent replacement that does not depart from the spirit and scope of the present invention should be covered by the scope of protection of the claims of the present invention.

Claims

1. A beam pointing change detection system based on PSD, characterized in that: The invention comprises a light beam sensing module (4) mounted on the surface of an optical plate (7) through a translation and lifting adjustment mechanism, a laser (1) mounted on the surface of the optical plate (7) through an adjustable clamp (2), and a reflector (3) fixed on the surface of a platform to be detected. The optical plate (7) is fixed on the surface of an air-floating platform (8). A PSD position sensitive detector in the light beam sensing module (4) is electrically connected to a software processing end through a driving circuit. A light beam emitted by the laser (1) is reflected by the reflector (3) and enters the PSD position sensitive detector in the light beam sensing module (4). The software processing end calculates the vibration angle of the platform to be detected in the vertical, horizontal and two-dimensional directions by collecting data on the change of the light spot position in the PSD position sensitive detector.

2. The PSD-based beam pointing change detection system according to claim 1, wherein: The translation and lifting adjustment mechanism comprises a lifting platform (5) and a translation platform (6), the light beam sensing module (4) is installed on the lifting platform (5), the lifting platform (5) is installed on the translation platform (6), the translation platform (6) and the optical plate (7) are fixedly installed, and the light beam sensing module (4) can be moved and adjusted in the vertical and horizontal directions respectively under the adjustment of the lifting platform (5) and the translation platform (6).

3. The PSD-based beam pointing change detection system according to claim 1, wherein: The light beam sensing module (4) comprises a telephoto lens and a PSD position sensitive detector chip, wherein the telephoto lens has a diameter of 80 mm and a focal length of 500 mm, and the PSD position sensitive detector chip is fixed at the focus of the telephoto lens. The PSD position sensitive detector chip is a two-dimensional detector chip, with a target surface size of 20*20 mm and a response wavelength range of 300-1100 nm.

4. The PSD-based beam pointing change detection system according to claim 1, wherein: The light source wavelength of the laser (1) is within the wavelength response range of a PSD position sensitive detector chip, and the laser divergence angle is less than 1 mrad. The maximum output power of the laser (1) is less than the damage threshold of the PSD position sensitive detector chip.

5. The PSD-based beam pointing change detection system according to claim 1, wherein: The center height of the laser (1), the center height of the reflector (3), and the center height of the light beam sensing module (4) are consistent.

6. A method for detecting beam pointing changes based on PSD, characterized in that: A PSD-based beam pointing change detection system according to claim 1, comprising: Fixing the reflector (3) on the surface of the platform to be detected; Starting the laser (1), adjusting the adjustable holder (2) and the translation and lifting adjustment mechanism so that the light spot is reflected by the reflector (3) at the center position of the PSD position sensitive detector chip in the beam sensing module (4); At the software processing end, the change data of the light spot position in the PSD position sensitive detector is collected to calculate the vibration angle of the platform to be detected in the vertical, horizontal and two-dimensional directions.

7. The PSD-based beam pointing change detection system according to claim 6, wherein: The vibration angles of the platform to be tested in the vertical, horizontal and two-dimensional directions are: Where Δθ x is the horizontal vibration angle, Δθ y is the vertical vibration angle, Δθ r is the vibration angle in the two-dimensional direction, ΔX is the horizontal displacement difference of the light spot on the PSD, ΔY is the vertical displacement difference of the light spot on the PSD, and f' is the focal length of the lens.

8. The PSD-based beam pointing change detection system according to claim 6, wherein: The software processing end collects the change data of the light spot position in the PSD position sensitive detector to calculate the vibration angles of the platform to be detected in the vertical, horizontal and two-dimensional directions. The software processing end also includes: when the light spot moves out of the PSD position sensitive detector chip, the software processing end records the last valid point (X1, Y1) of the light spot and the point where the light spot re-enters (X2, Y2), and combines the horizontal and vertical time domain compensation functions to calculate the horizontal and vertical displacement differences on the PSD position sensitive detector chip during the light spot movement period, thereby calculating the horizontal and vertical vibration angles and the two-dimensional vibration angles of the light spot when it moves out of the PSD: Where: is the horizontal vibration angle of the light spot moving out of the PSD stage, is the vertical vibration angle of the light spot when it moves out of the PSD stage, is the vibration angle of the light spot in the two-dimensional direction when it moves out of the PSD stage, f' is the focal length of the lens, is the horizontal displacement difference on the PSD position sensitive detector chip during the light spot moving out period, is the vertical displacement difference on the PSD position sensitive detector chip during the light spot moving out period, φ(t), are the time domain compensation functions in the horizontal and vertical directions respectively.

9. The PSD-based beam pointing change detection system according to claim 8, wherein: The calculation expressions of the horizontal and vertical time domain compensation functions are: Where: x is the equivalent damping coefficient in the horizontal direction, ω x is the natural angular frequency of horizontal vibration, φ x is the horizontal phase offset angle, ξ y is the equivalent damping coefficient in the vertical direction, ω y is the vertical vibration natural angular frequency, φ y is the vertical phase offset angle.

10. The PSD-based beam pointing change detection system according to claim 9, wherein: The calculation expressions of the equivalent damping coefficients in the horizontal and vertical directions are: Where: x n 、y n are the horizontal and vertical displacement amplitudes of the nth vibration cycle, respectively, and N is the number of attenuation cycles; The calculation expressions of the horizontal and vertical vibration natural angular frequencies are: Where: T x 、T y are the horizontal and vertical vibration periods respectively; The calculation expressions of the horizontal and vertical phase offset angles are: Where: X(t0) is the horizontal displacement of the light spot when it moves out of the PSD, is the horizontal velocity at the moment when the displacement disappears, Y(t0) is the vertical displacement of the light spot when it moves out of the PSD, is the vertical velocity at the moment when the displacement disappears.

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