Small-angle measuring instrument and measuring method

Abstract

The invention discloses a small-angle measuring instrument and a measuring method.The small-angle measuring instrument comprises a bridge frame and a height adjusting mechanism, a reflecting mirror is fixed to one end of the bridge frame, the height adjusting mechanism is used for supporting the bridge frame and adjusting and measuring the height of the bridge frame, and the small-angle measuring instrument specifically comprises a lifting structure, an optical pyramid fixed to the bridge frame and a double-frequency laser interferometer; the bridge is erected on the lifting structure, the double-frequency laser interferometer is used for measuring the offset of the optical pyramid caused by height adjustment of the bridge, the offset of the optical pyramid far away from one side of the reflector is zero as a reference during measurement, and the height of the bridge on the side of the reflector is adjusted through the lifting structure. The reflector can reflect a laser beam emitted by the first interferometer to the to-be-measured element, interference fringes are not generated after the laser beam is received by the first interferometer, and the wedge angle and the deviation angle of the to-be-measured element are calculated by obtaining the offset of the optical pyramid in the vertical direction. According to the invention, the angle precision generated by the small angle is improved, and the small angle measurement with higher efficiency and reliability is realized.

Description

Technical Field

[0001] This invention relates to the field of optical measurement technology, and in particular to a small-angle measuring instrument and measurement method. Background Technology

[0002] A small angle measuring instrument is a geometric measuring instrument used to generate standard minute angles, with a range of 0′ to 40′. Currently used small angle measuring instruments typically use two fixed-axis rods with a fixed axial distance on a ribbed worktable, equipped with corresponding optical meters. Adjusting the tilt of the worktable reproduces the standard angle. The rod spacing *l* is generally 500 mm, and the small angle *a* generated by the instrument is essentially produced by the tangent *h* (millimeters) of 500 mm, i.e., *a* = arctan(h / l). Therefore, the accuracy of the height value *h* and the accuracy of the rod spacing *l* are the two most important specifications of this small angle measuring instrument.

[0003] Taking the measurement of the wedge angle of an optical protractor as an example, most small angle measuring instruments use gauge blocks as the method of generating tilt angles. Therefore, different sizes of gauge blocks are required for measurement, and the reproduced angles are discrete and discontinuous. It is difficult to handle the measurement of some special angles. Moreover, the operation steps of this small angle measuring instrument are also very complicated, and the readings are not intuitive. In many cases, multiple gauge blocks need to be combined for measurement and repeated measurements are required, which increases the cumbersomeness of subsequent data processing and greatly restricts the efficiency and quality of optical protractor testing. Summary of the Invention

[0004] Purpose of the invention: The purpose of this invention is to provide a small angle measuring instrument and method to improve the accuracy of small angle measurements and achieve more efficient and reliable small angle measurements.

[0005] Technical Solution: To achieve the above objectives, the present invention provides a small angle measuring instrument, comprising a cable tray and a height adjustment mechanism. A reflector is fixed at one end of the cable tray. The height adjustment mechanism comprises two sets for supporting the cable tray and adjusting and measuring the height of the cable tray in the vertical direction. The height adjustment mechanism includes a lifting structure, an optical bevel fixed on the upper surface of the cable tray, and a dual-frequency laser interferometer. The cable tray is mounted on the lifting structure, and the dual-frequency laser interferometer is used to measure the offset of the optical bevel caused by the height adjustment of the cable tray.

[0006] Preferably, the lifting structure includes an electric lifting platform and a piezoelectric nanopositioning platform, wherein the piezoelectric nanopositioning platform is mounted on the electric lifting platform.

[0007] Preferably, the bridge is mounted on a piezoelectric nanopositioning stage via a cylindrical support.

[0008] Preferably, it also includes a base, on which the height adjustment mechanism is mounted, wherein the dual-frequency laser interferometer is mounted above the optical pyramid via a support plate fixed to the base.

[0009] The present invention describes a measurement method for a small-angle measuring instrument. Using zero offset of the optical cone on the side furthest from the reflector as a reference, the height of the bridge on the side where the reflector is located is adjusted via a lifting structure so that the reflector can reflect the laser beam from the first interferometer directed at the element under test. The goal is to ensure that no interference fringes are generated after the first interferometer receives the laser beam. A dual-frequency laser interferometer is used to obtain the vertical offset h of the optical cone, and then the deflection angle α = arctan(h / l) of the element under test is calculated, with the wedge angle θ = α / (n-1), where l is the central axis distance between the two sets of optical cones, and n is the refractive index of the material of the element under test.

[0010] Preferably, the element under test includes an optical angle gauge or an autocollimator.

[0011] Preferably, when the cable tray is horizontal, the lifting structure, optical pyramid, and dual-frequency laser interferometer in the height adjustment mechanism are coaxial.

[0012] Beneficial effects: The present invention has the following advantages: 1. The present invention combines the dual lifting mechanism drive with laser interference closed-loop feedback to realize continuous, high-precision generation and active control of small angles; 2. The present invention is a non-contact measurement, which avoids the errors caused by contact measurement and improves the reliability of measurement; 3. It eliminates the need for manual assembly of gauge blocks and complex readings, greatly simplifies the operation process and improves detection efficiency. Attached Figure Description

[0013] Figure 1 This is a schematic diagram of the three-dimensional structure of a small angle measuring instrument;

[0014] Figure 2 This is a front view of a small angle measuring instrument;

[0015] Figure 3 Here is a diagram showing the technical parameters of the small angle measuring instrument;

[0016] Figure 4 This is a comparison chart of the measurement results of the present invention and existing small angle measuring instruments. Detailed Implementation

[0017] The technical solution of the present invention will be described in detail below with reference to the embodiments and accompanying drawings.

[0018] like Figure 1 , 2As shown, the apparatus includes a measuring platform 10, a small angle measuring instrument, a first interferometer 9, and an optical angle gauge 8, all placed on the measuring platform 10. The small angle measuring instrument includes a base 1, two sets of height adjustment mechanisms, and a cable tray 5, which is supported by the two sets of height adjustment mechanisms. The two sets of height adjustment mechanisms are standard small angle generators, which, through coordinated adjustment, can precisely control the angle of the cable tray 5. A reflector 7 is fixed on the cable tray 5 near the optical angle gauge 8.

[0019] When the cable tray 5 is placed horizontally and the optical angle gauge 8 is not placed, the reflector 7 can reflect the laser beam emitted by the first interferometer 9 back along its original path. At this time, the number of interference fringes in the first interferometer 9 is zero. The laser beam emitted by the first interferometer 9 passes through the optical angle gauge 8 and hits the reflector 7. Since the optical angle gauge 8 has a small wedge angle θ, the beam will produce a fixed deflection angle α after transmission. Subsequently, this deflected beam hits the reflector 7 on the small angle measuring instrument, returns along its original path after reflection, passes through the optical angle gauge 8 again, and is received by the first interferometer 9. A certain number of interference fringes are generated due to the deflection angle. The small angle measuring instrument of the present invention uses a height adjustment mechanism to adjust the angle of the cable tray 5 so that the number of interference fringes obtained by the first interferometer 9 is zero again. By obtaining the adjustment parameters of the height adjustment mechanism, the deflection angle of the optical angle gauge 8 and the wedge angle of the gauge itself are calculated to realize the small angle measurement of the optical angle gauge 8.

[0020] The height adjustment mechanism includes an electric lifting platform 2, a piezoelectric nano-positioning stage 3, a support plate, and a dual-frequency laser interferometer 4. The dual-frequency laser interferometer 4 is mounted on the base via the support plate. The electric lifting platform 2 is installed on the base, and the piezoelectric nano-positioning stage 3 is installed on the electric lifting platform 2. Both the electric lifting platform 2 and the piezoelectric nano-positioning stage 3 achieve vertical lifting. The electric lifting platform 2 has a large adjustment range but low adjustment precision, while the piezoelectric nano-positioning stage 3 has a small adjustment range but high adjustment precision. The combination of the two achieves a wide range and high precision height adjustment for the cable tray 5. The electric lifting platform 2, the piezoelectric nano-positioning stage 3, and the dual-frequency laser interferometer 4 are coaxial.

[0021] The bridge 5 is symmetrically placed on two sets of piezoelectric nanopositioning stages 3 via cylinders on both sides. An optical pyramid 6 is mounted on the upper surface of the bridge 5, and the optical pyramid 6 is located directly below the dual-frequency laser interferometer 4. The dual-frequency laser interferometer 4 emits a laser beam that hits the optical pyramid 6. The optical pyramid 6 can cause the beam to return along its original path. When the optical pyramid 6 is deflected, the dual-frequency laser interferometer 4 obtains the amount of vertical displacement of the optical pyramid 6 after receiving the returned beam.

[0022] In the initial state before the optical angle gauge 8 is measured, the bridge 5 is placed horizontally, the offset of the optical cones of the two sets of height adjustment mechanisms is 0, and the number of interference fringes on the first interferometer 9 is zero.

[0023] After an optical angle gauge 8 is added between the reflector 7 and the first interferometer 9, a certain number of interference fringes are generated on the first interferometer 9 due to the deflection angle. At this time, the electric lifting platform 2 and the piezoelectric nano-positioning platform 3 of the two height adjustment mechanisms work together to adjust the optical cone offset of the left height adjustment mechanism (the side away from the optical cone 6) so that the optical cone offset of the other height adjustment mechanism is always kept at 0, while the optical cone offset of the other height adjustment mechanism is offset by a height of h (that is, the pitch angle of the bridge 5 is changed). The generation of this offset makes the number of interference fringes formed on the first interferometer 9 by the light reflected back by the reflector 7 return to zero.

[0024] Based on the offset h and the distance l between the central axes of the two sets of height adjustment mechanisms (i.e., the distance between the central axes of the two sets of optical cones 6), the pitch angle α of the bridge frame 5 is obtained, α = arctan(h / l). Based on the pitch angle α, the deflection angle and wedge angle of the optical angle gauge 8 are calculated, where the deflection angle is α and the wedge angle is θ = α / (n-1), and n is the refractive index of the material of the optical angle gauge 8.

[0025] Preferably, by extending the distance l between the central axes of the two sets of height adjustment mechanisms, such as 1000mm, the present invention can obtain a larger optical cone displacement 6 under the same θ condition compared with the existing small angle measuring instrument, thereby achieving more precise control feedback to the generation of small angles.

[0026] This invention transforms contact measurement into non-contact measurement through the synergistic effect of a dual-frequency laser interferometer 4, an optical pyramid 6, an electric lifting platform 2, and a piezoelectric nano-positioning stage 3. It also improves the accuracy of small-angle adjustment and measurement, while making adjustment more convenient, stable, repeatable, and continuous.

[0027] Preferably, the base 1 and the bridge 5 can be made of marble, which has a low coefficient of linear expansion, which can further reduce errors in a stable temperature and humidity laboratory, while ensuring that the calibrated axial spacing can be kept within the error range.

[0028] like Figure 3 The figures shown are the technical parameters of each component in the small angle measuring instrument described in this invention. Figure 4 As shown, in Figure 3 The results of the comparison between the measurement accuracy and measurement efficiency of the small angle measuring instrument under the technical parameters and existing small angle measuring instruments are presented by [the relevant authority / organization]. Figure 4 It can be seen that the present invention is more operable in terms of contact form and operation mode, and the measurement accuracy of the present invention is significantly improved within the same measurement range.

Claims

1. A small angle measuring instrument, characterized in that, The system includes a cable tray (5) and a height adjustment mechanism. One end of the cable tray (5) is fixed with a reflector (7). The height adjustment mechanism includes two sets, which are used to support the cable tray (5) and adjust and measure the height of the cable tray (5) in the vertical direction. The height adjustment mechanism includes a lifting structure, an optical pyramid (6) fixed on the upper surface of the cable tray (5), and a dual-frequency laser interferometer (4). The cable tray (5) is mounted on the lifting structure. The dual-frequency laser interferometer (4) is used to measure the offset of the optical pyramid (6) caused by the height adjustment of the cable tray (5).

2. The small angle measuring instrument according to claim 1, characterized in that, The lifting structure includes an electric lifting platform (2) and a piezoelectric nanopositioning platform (3), wherein the piezoelectric nanopositioning platform (3) is installed on the electric lifting platform (2).

3. The small angle measuring instrument according to claim 2, characterized in that, The bridge (5) is mounted on the piezoelectric nanopositioning stage (3) via a cylindrical support.

4. The small angle measuring instrument according to claim 1, characterized in that, It also includes a base (1), on which the height adjustment mechanism is mounted, wherein the dual-frequency laser interferometer (4) is mounted above the optical pyramid (6) via a support plate fixed to the base (1).

5. A measurement method applied to the small angle measuring instrument of claim 1, characterized in that, Using the zero offset of the optical pyramid (6) on the side away from the reflector (7) as a reference, the height of the bridge on the side where the reflector (7) is located is adjusted by the lifting structure so that the reflector (7) can reflect the laser beam that the first interferometer (9) hits the element under test. The goal is that no interference fringes are generated after the first interferometer (9) receives the laser beam. The offset h of the optical pyramid (6) in the vertical direction is obtained by the dual-frequency laser interferometer (4). Then, the deflection angle of the element under test is calculated as ɑ=arctan(h / l), and the wedge angle is θ=ɑ / (n-1), where l is the center axis distance between the two sets of optical pyramids (6) and n is the refractive index of the material of the element under test.

6. The measurement method according to claim 1, characterized in that, The component under test includes an optical angle gauge or an autocollimator.

7. The measurement method according to claim 1, characterized in that, When the cable tray (5) is horizontal, the lifting structure, optical pyramid (6), and dual-frequency laser interferometer (4) in the height adjustment mechanism are coaxial.

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