An angle deflection detection device

Abstract

The utility model provides an angle deflection detection device relates to position detection technical field, including light source, reflector, concave reflection grating, transmission grating, photoelectric detector. Light source is used for producing light beam, reflector is used for coupling detection object's pivot, and will light beam reflect to concave reflection grating, produce the reflection light of light intensity periodic change with the rotation of pivot, transmission grating is different with the period of concave reflection grating, sets up on the light path of reflection light, carries out phase modulation to reflection light, and projects the projection with moire fringe on photoelectric detector, photoelectric detector is used for detecting the light intensity change of moire fringe, obtains the rotation angle of pivot. The utility model provides an angle deflection detection device can reduce the influence of temperature to detection accuracy, and reduces the rotational inertia, improves detection accuracy.

Description

Technical Field

[0001] This utility model relates to the field of position detection technology, and in particular to an angle deflection detection device. Background Technology

[0002] In industrial processing, laser processing is a method that uses a laser beam to scan and process an object. Precise positioning of the laser beam is crucial during the process. Currently, galvanometers are generally used to reflect and scan the laser beam. The principle of the galvanometer is to control the beam by rotating an external reflector driven by a motor shaft. To precisely control the beam's landing point during processing, precise control of the motor shaft's rotation angle in real time is necessary. Existing technology typically uses a current meter scanner. The current meter couples the motor shaft to a variable capacitor, detecting the rotation angle by measuring the value of the variable capacitor. This method is highly susceptible to temperature variations and has a large moment of inertia, significantly impacting the precision control of the motor shaft during high-speed, real-time movement. Utility Model Content

[0003] To address the problems in the background art, this utility model aims to provide an angle deflection detection device that reduces the influence of temperature on detection accuracy and reduces rotational inertia, thereby improving detection accuracy.

[0004] To solve the above-mentioned technical problems, the present invention adopts the following technical solution:

[0005] An angle deflection detection device includes a light source, a reflector, a concave reflective grating, a transmission grating, and a photodetector.

[0006] The light source is used to generate a light beam; the reflector is used to couple the rotating shaft of the object being detected and reflect the light beam onto the concave reflective grating, generating reflected light whose intensity changes periodically with the rotation of the shaft; the transmission grating has a different period from the concave reflective grating and is placed in the optical path of the reflected light to modulate the phase of the reflected light and project a projection with moiré fringes onto the photodetector; the photodetector is used to detect the intensity change of the moiré fringes to obtain the rotation angle of the shaft.

[0007] Furthermore, with the rotation axis as the Y-axis, the reflector is parallel to the Y-axis; on the XZ plane, the projection of the beam passes through the axis of rotation along the Z-axis direction, the center of the concave reflective grating is concentric with the rotation axis, and the beam is focused at the focal point of the concave reflective grating.

[0008] Furthermore, the projection of the light beam onto the YZ plane has a preset angle with the Z-axis.

[0009] Furthermore, the wavelength of the light source is λ; the reflecting surface of the concave reflection grating has a grating structure with a period of P1; the transmission grating is a phase grating with a period of P2 distribution, and for incident light with an incident wavelength of λ, the maximum optical path difference in any region is λ / 4.

[0010] Furthermore, the distance Z1 between the concave reflection grating and the transmission grating satisfies Z1=m*(P1 2 / λ), m is a positive integer; the distance Z2 between the transmission grating and the photodetector satisfies Z2=n*(P1 2 / λ)=k*(P2 2 / λ), where n and k are positive integers.

[0011] Furthermore, the projection period is P3; the photodetector includes periodic incremental light-receiving units with a period of P3.

[0012] Furthermore, a non-reflective zero-position signal mark is set at the center of the concave reflective grating, and the width P4 of the zero-position signal mark satisfies P4 = t * P1, where t is a positive integer greater than 1; the photodetector also includes an absolute light-receiving unit coupled in the incremental light-receiving unit.

[0013] Furthermore, the absolute light-receiving unit includes four detection elements B1 to B4 arranged side by side, each with a width of 1 / 2 * P4.

[0014] Furthermore, the absolute light-receiving unit is located in the middle of the incremental light-receiving unit, and there is a gap between it and the incremental light-receiving unit that is greater than or equal to 1 / 2*P4.

[0015] Furthermore, the light source is a collimated light source.

[0016] Compared with the prior art, the beneficial effects of this utility model are:

[0017] This invention couples a reflector to the axis of rotation of the object being detected, allowing the detection beam to be reflected by the reflector and then irradiated onto a concave reflective grating. This enables the detection beam to carry rotational angular information, and the grating further generates moiré fringes. The amplification effect of the moiré fringes converts minute angular deflections into clear projected phase changes, thus achieving extremely high detection sensitivity and accuracy. This invention reduces the impact of environmental interference such as temperature changes on the detection results through optical measurement. Furthermore, its compact structure, with the rotating part consisting only of a lightweight reflector, significantly reduces the additional rotational inertia, providing crucial support for precise control of the axis under real-time high-speed motion. This results in significant benefits such as high precision, high stability, and rapid dynamic response. Attached Figure Description

[0018] Figure 1 This is an optical path diagram of the angle deflection detection device in an embodiment of this utility model;

[0019] Figure 2 This is a schematic diagram of the shape of the concave reflective grating in an embodiment of this utility model;

[0020] Figure 3 This is a schematic diagram of the shape of the transmission grating in an embodiment of this utility model;

[0021] Figure 4 This is a schematic diagram of the projection shape in an embodiment of this utility model;

[0022] Figure 5 This is an enlarged schematic diagram of the concave-convex total reflection structure of the concave-convex reflective grating in the embodiment of this utility model;

[0023] Figure 6 This is an enlarged schematic diagram of the semi-transparent and semi-reflective structure of the concave reflective grating in this embodiment of the present invention;

[0024] Figure 7 This is a schematic diagram of the incremental light-receiving unit in an embodiment of the present invention;

[0025] Figure 8 This is a schematic diagram of the output signal of the incremental light receiving unit in an embodiment of this utility model;

[0026] Figure 9 This is a schematic diagram of the structure of the zero-position signal marker in an embodiment of this utility model;

[0027] Figure 10 This is a schematic diagram of the projection shape corresponding to the zero-position signal mark in an embodiment of this utility model;

[0028] Figure 11 This is a schematic diagram of the photodetector in an embodiment of the present invention;

[0029] Figure 12 This is a schematic diagram illustrating the reference zero-position signal detection principle in an embodiment of this utility model.

[0030] Wherein, 1: light source; 2: mirror; 3: concave reflective grating; 4: transmission grating; 5: photodetector; 6: rotating shaft; 7: projection; 8: incremental light receiving unit; 9: zero position signal mark; 10: absolute light receiving unit; 11: interval. Detailed Implementation

[0031] It should be understood that the specific embodiments described herein are merely illustrative of the present invention and are not intended to limit the present invention.

[0032] The technical solutions of the present utility model will be clearly and completely described below with reference to the accompanying drawings of the embodiments. Obviously, the described embodiments are only some embodiments of the present utility model, and not all embodiments. Based on the embodiments of the present utility model, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the protection scope of the present utility model.

[0033] It should be noted that all directional indicators (such as up, down, left, right, front, back, etc.) in this utility model embodiment are only used to explain the relative positional relationship and movement of each component in a certain specific posture (as shown in the figure). If the specific posture changes, the directional indicator will also change accordingly. The connection can be a direct connection or an indirect connection.

[0034] Furthermore, the technical solutions of the various embodiments can be combined with each other, but this must be based on the ability of those skilled in the art to implement them. When the combination of technical solutions is contradictory or cannot be implemented, it should be considered that such combination of technical solutions does not exist and is not within the scope of protection claimed by this utility model.

[0035] One embodiment of this utility model provides an angle deflection detection device, such as... Figure 1 The diagram shown is an optical path diagram of the angle deflection detection device provided in this embodiment. The angle deflection detection device provided in this embodiment includes a light source 1, a reflector 2, a concave reflective grating 3, a transmission grating 4, and a photodetector 5.

[0036] Light source 1 is used to generate a light beam; mirror 2 is used to couple the rotating shaft 6 of the object being detected and reflect the light beam onto the concave reflective grating 3, generating reflected light whose intensity changes periodically with the rotation of the rotating shaft 6; the transmission grating 4 has a different period from the concave reflective grating 3 and is set in the optical path of the reflected light to perform phase modulation on the reflected light and project a projection with moiré fringes onto the photodetector 5; the photodetector 5 is used to detect the intensity change of the moiré fringes and obtain the rotation angle of the rotating shaft 6.

[0037] In this system, the light source 1 can be either an LD or an LED, provided that the light intensity emitted by the light source 1 has a stable distribution. Preferably, the light beam emitted by the light source 1 can be modulated by a collimating lens and a focusing cylindrical lens, so that the modulated light beam is focused on the focal point of the concave reflective grating 3. The reflected light formed after passing through the concave reflective grating 3 can be transmitted backward in a collimated state. The reflector 2 is coupled to the rotation axis 6 of the object being detected and rotates with the rotation axis 6. The object being detected is generally a motor. The reflector 2 reflects the light beam onto the concave reflective grating 3, so that the direction of the light beam changes with the angle of the rotation axis 6. Due to the diffraction characteristics of the concave reflective grating 3, the reflected light will change linearly with the rotation axis 6, thus carrying angle information. The transmission grating 4 performs secondary phase modulation on the reflected light, forming a projection with moiré fringes on the photodetector 5. The angle information is also reflected in the intensity change of the moiré fringes. The photodetector 5 analyzes the changes in light intensity of the moiré fringes to deduce the rotation angle of the rotating shaft 6, thereby achieving angle measurement. The moiré fringes have an amplification effect, which can convert minute angle changes into obvious fringe movements, thus improving detection sensitivity.

[0038] In summary, this embodiment couples the reflector 2 to the rotating shaft 6 of the object being detected, allowing the detection beam to be reflected by the reflector 2 and then irradiated onto the concave reflective grating 3. This enables the detection beam to carry rotational angle information. Furthermore, the grating generates moiré fringes, and the amplification effect of the moiré fringes converts minute angular deflections into clear projected phase changes, thereby achieving extremely high detection sensitivity and accuracy. This embodiment reduces the impact of environmental interference such as temperature changes on the detection results through optical measurement. Moreover, its compact structure, with the rotating part consisting only of a lightweight reflector 2, significantly reduces the additional rotational inertia, providing crucial support for the precise control of the rotating shaft 6 under real-time high-speed motion. This achieves the significant benefits of high precision, high stability, and rapid dynamic response.

[0039] In this embodiment, the rotating shaft 6 is the Y-axis, and the reflector 2 is parallel to the Y-axis; the projection of the light beam on the XZ plane passes through the axis of the rotating shaft 6 along the Z-axis direction, the center of the concave reflective grating 3 is concentric with the rotating shaft 6, and the light beam is focused at the focal point of the concave reflective grating 3.

[0040] The concave reflective grating 3 has a cylindrical working surface, with its center coaxial with the rotating shaft 6, and the optical axis of the light beam passes through the axis of the rotating shaft 6. When the rotating shaft 6 rotates, the reflector 2 deflects, but the light beam always points to the center of the concave reflective grating 3, ensuring that the angle change of the light beam incident on the concave reflective grating 3 is linearly related to the angle of the rotating shaft 6, reducing optical aberrations, and making the phase change of the reflected light from the concave reflective grating 3 more directly reflect the angle of the rotating shaft 6, thus reducing nonlinear errors. The focal point of the concave reflective grating 3 is located at half its radius. The light beam is focused at this focal point, enabling the reflected light after passing through the concave reflective grating 3 to be transmitted backward in a collimated state, improving detection accuracy.

[0041] In this embodiment, the projection of the light beam onto the YZ plane has a preset angle with the Z-axis.

[0042] In this design, the projection of the light beam onto the YZ plane has a preset angle with the Z-axis, meaning the beam is incident obliquely onto the reflector 2. This facilitates the placement of the light source 1 and the photodetector 5, preventing interference between them. The focal points of the rotating shaft 6 and the concave reflective grating 3 are both elongated. In this embodiment, the angle cannot be too large or too small, ensuring the detection beam propagates completely within the optical path. The incident and reflected light can be separated, eliminating the need for beam splitting components or structures and simplifying the angle deflection detection device.

[0043] like Figures 2 to 4 The diagram shown is a schematic representation of the grating and projection in this embodiment. In this embodiment, the wavelength of the light source 1 is λ.

[0044] The concave reflective grating 3 has a grating structure with a period of P1 on its reflective surface.

[0045] The transmission grating 4 is a phase grating with a periodic P2 distribution. For incident light with an incident wavelength of λ, the maximum optical path difference in any region is λ / 4.

[0046] The concave reflection grating 3 has a periodic phase grating structure on its inner surface, which does not cause a loss of reflected light intensity but simply introduces phase modulation. This grating structure can be a concave-convex total reflection structure, such as... Figure 5 The diagram shown is an enlarged schematic of the concave-convex total reflection structure of the concave-convex reflective grating in this embodiment. For incident light with an incident wavelength of λ, the maximum optical path difference in any region is λ / 2, and the modulation phase magnitude is determined by the depth difference h between the concave and convex surfaces of the total reflection structure. This embodiment further controls the maximum optical path difference of the concave reflective grating 3, ensuring that the phase change of the reflected light is uniform and continuous during reflection, reducing scattering and aberrations, and enabling the reflected light to form a high-quality wavefront, laying the foundation for subsequent modulation. This grating structure can also be a semi-transparent, semi-reflective structure, such as... Figure 6As shown, this is an enlarged schematic diagram of the semi-transparent and semi-reflective structure of the concave reflective grating in another embodiment. For incident light with an incident wavelength of λ, after reflection by the semi-transparent and semi-reflective structure, a brightness and darkness intensity distribution with a period of P1 can be formed. The maximum optical path difference of the transmission grating 4 is λ / 4. As a phase grating, the transmission grating 4 finely modulates the reflected light, avoiding excessive phase jumps, which helps to generate high-contrast moiré fringes with clear fringe edges, making it easy for the photodetector 5 to accurately capture phase changes.

[0047] In this embodiment, the distance Z1 between the concave reflective grating 3 and the transmittance grating 4 satisfies Z1=m*(P1 2 / λ), where m is a positive integer.

[0048] The distance Z2 between the transmission grating 4 and the photodetector 5 satisfies Z2=n*(P1) 2 / λ)=k*(P2 2 / λ), where n and k are positive integers.

[0049] The distance between the concave reflection grating 3 and the transmission grating 4 is the optical path distance. When this distance is Z1, the Talbot effect is generated, enabling the reflected light to have a good imaging effect on the transmission grating 4. Preferably, m = 1. The distance Z2 between the transmission grating 4 and the photodetector 5 needs to satisfy two conditions simultaneously: an integer multiple of n times the Talbot distance based on the period P1 of the concave reflection grating 3, and an integer multiple of k times the Talbot distance based on the period P2 of the transmission grating 4 itself. This ensures that a clear image of the periodic grating structure can be obtained at both the transmission grating 4 and the photodetector 5, which are two key positions. The moiré fringe signal received by the detector has a high intensity, low background noise, and clear edges, which greatly facilitates subsequent phase extraction and calculation, and improves the angle detection resolution and accuracy of the entire system. This embodiment restricts the position of each optical element and optimizes the optical path layout. At a specific Talbot distance, the tolerance of the grating image pair to defocus and small deviations is relatively high, which can relax the tolerance of mechanical assembly, reduce the difficulty and cost of precision assembly, improve the product yield, and enhance the reliability and robustness of the system.

[0050] like Figure 7 As shown, this is a schematic diagram of the photodetector in this embodiment. In this embodiment, the period of projection 7 is P3; the photodetector 5 includes a periodic incremental light-receiving unit 8 with a period of P3.

[0051] In this context, P3 is the period of the moiré fringe projection 7 formed on the surface of the photodetector 5, which is an optical period generated by the combined effect of the period P1 of the concave reflective grating 3 and the period P2 of the transmission grating 4. The incremental light-receiving unit 8 on the photodetector 5 has a period of P3, and its photosensitive units are arranged with a specific period P3, similar to an incremental optical encoder. This is used to detect the periodic changes in light intensity during the movement of the moiré fringes, with each period corresponding to a small angular increment. When both the photosensitive period of the photodetector 5 and the optical period of the moiré fringes are P3, it means that the bright or dark band of each moiré fringe will completely cover a corresponding set of photosensitive units, maximizing the collection of signal light energy and suppressing noise. Figure 8 The diagram shows the output signal of the photodetector. When the rotating shaft 6 rotates at a constant speed, the photodetector 5 reads the light intensity changes of these moiré fringes and performs photoelectric conversion based on a four-step phase shift, outputting two orthogonal differential signals S1 and S2. Since the number of periodic changes of the orthogonal signals is linearly positively correlated with the rotation angle of the rotating shaft 6, after actual calibration, the orthogonal differential signals can be used for counting and subdivision to achieve the measurement of any rotation angle.

[0052] like Figure 9 , 10 The diagram shown illustrates the structure and corresponding projection shape of the zero-position signal marker in this embodiment. In this embodiment, a non-reflective zero-position signal marker 9 is provided at the center of the concave reflective grating 3. The width P4 of the zero-position signal marker 9 satisfies P4 = t * P1, where t is a positive integer greater than 1. Figure 11 As shown, the photodetector 5 also includes an absolute light-receiving unit 10 coupled in the incremental light-receiving unit 8.

[0053] The non-reflective zero-position signal marker 9, serving as the absolute position reference for the zero position, is positioned at the center of the concave reflective grating 3. This non-reflective position creates a identifiable signal gap within the periodic moiré fringes. The width of the zero-position signal marker 9 is significantly larger than the period of the concave reflective grating 3, ensuring a sufficiently long physical distance to generate a complete, noise-free signal abrupt change when the light beam sweeps across the zero position, making the zero-position signal clearly discernible. Furthermore, setting its width to an integer multiple of P1 helps align the boundary of the zero-position marker with the periodic structure of the grating, avoiding complex edge diffraction effects that could interfere with the normal moiré fringe signal. The absolute light-receiving unit 10 in the photodetector 5 detects changes in the center position signal corresponding to the zero-position signal marker 9 and works in conjunction with the incremental light-receiving unit 8 to further improve detection accuracy.

[0054] In this embodiment, the absolute light-receiving unit 10 includes four detection elements B1 to B4 arranged side by side, and the width of each detection element is 1 / 2*P4.

[0055] The absolute light-receiving unit 10 includes four independent detection elements arranged side-by-side, labeled B1, B2, B3, and B4. The width of each detection element is half the width P4 of the zero-position signal marker 9. When the projected light intensity of the zero-position marker has not swept across the B1-B4 region, the PD light intensity of the four signals fluctuates near the DC bias. As the projected light intensity of the zero-position marker gradually sweeps across the B1-B4 region, the intensity changes of the four signals exhibit a triangular distribution, first decreasing and then increasing. We perform mathematical operations on the four signals, defining A1 = (B3 + B4 - B1 - B2) and A2 = (B1 + B4 - B2 - B3). The intensity distribution changes with the rotation angle of the shaft 6 as follows: Figure 12 As shown, Figure 12 This is a schematic diagram of the reference zero-point signal detection principle in this embodiment. By defining the reference zero point Z-ref position as the position corresponding to the maximum value of A1 in the single period P1 region corresponding to the zero-crossing center of A2, the unique zero point position is confirmed in the entire scanning range. Regardless of the forward or reverse rotation of axis 6, the zero point position is unique and fixed, thereby improving the accuracy of real-time measurement.

[0056] In this embodiment, the absolute light-receiving unit 10 is disposed in the middle of the incremental light-receiving unit 8, and a gap 11 greater than or equal to 1 / 2*P4 is provided between it and the incremental light-receiving unit 8.

[0057] The zero-position marker is located at the center of the concave reflective grating 3, and its projection onto the photodetector 5 is also located in the central region of the photodetector 5. The absolute light-receiving unit 10 is located in the middle of the incremental light-receiving unit 8, which can ensure the repeatability accuracy of the absolute zero position. A gap is set between the absolute light-receiving unit 10 and the incremental light-receiving unit 8 to effectively prevent photoelectric signal crosstalk and ensure the quality of the incremental signal.

[0058] In this embodiment, light source 1 is a collimated light source.

[0059] By replacing light source 1 with a collimated light source that has a larger output projection, the collimating lens can be further eliminated. This structure has a smaller spatial structure and a smaller moment of inertia, which can further improve the upper limit of scanning speed and accuracy. At the same time, it can further reduce the space of the detection equipment and make it suitable for smaller working environments.

[0060] The above description is only a preferred embodiment of the present utility model and does not limit the patent scope of the present utility model. Any equivalent structural or procedural transformations made based on the content of the present utility model specification and drawings, or direct or indirect applications in other related technical fields, are similarly included within the patent protection scope of the present utility model.

Claims

1. An angle deflection detection device, characterized in that, Includes a light source (1), a mirror (2), a concave reflective grating (3), a transmission grating (4), and a photodetector (5); The light source (1) is used to generate a light beam; the reflector (2) is used to couple the rotating shaft (6) of the object being detected and reflect the light beam onto the concave reflective grating (3) to generate reflected light whose intensity changes periodically with the rotation of the rotating shaft (6); the transmission grating (4) has a different period from the concave reflective grating (3), is set in the optical path of the reflected light, performs phase modulation on the reflected light, and projects a projection (7) with moiré fringes onto the photodetector (5); the photodetector (5) is used to detect the intensity change of the moiré fringes and obtain the rotation angle of the rotating shaft (6).

2. The angle deflection detection device according to claim 1, characterized in that, With the rotating shaft (6) as the Y-axis, the reflector (2) is parallel to the Y-axis; on the XZ plane, the projection of the light beam passes through the axis of the rotating shaft (6) along the Z-axis direction, the center of the concave reflective grating (3) is concentric with the rotating shaft (6), and the light beam is focused at the focal point of the concave reflective grating (3).

3. The angle deflection detection device according to claim 2, characterized in that, The projection of the light beam onto the YZ plane has a preset angle with the Z-axis.

4. The angle deflection detection device according to claim 1, characterized in that, The wavelength of the light source (1) is λ; The concave reflective grating (3) has a grating structure with a period of P1 on its reflective surface; The transmission grating (4) is a phase grating with a periodic distribution of P2. For incident light with an incident wavelength of λ, the maximum optical path difference in any region is λ / 4.

5. The angle deflection detection device according to claim 4, characterized in that, The distance Z1 between the concave reflective grating (3) and the transmission grating (4) satisfies m is a positive integer; The distance Z2 between the transmission grating (4) and the photodetector (5) satisfies n and k are positive integers.

6. The angle deflection detection device according to claim 4, characterized in that, The period of the projection (7) is P3; the photodetector (5) includes a periodic incremental light-receiving unit (8) with a period of P3.

7. The angle deflection detection device according to claim 6, characterized in that, The concave reflective grating (3) has a non-reflective zero-position signal mark (9) at its center, and the width P4 of the zero-position signal mark (9) satisfies t is a positive integer greater than 1; the photodetector (5) also includes an absolute light-receiving unit (10) coupled in the incremental light-receiving unit (8).

8. The angle deflection detection device according to claim 7, characterized in that, The absolute light-receiving unit (10) includes four detection elements B1 to B4 arranged side by side, each detection element having a width of [missing information]. .

9. The angle deflection detection device according to claim 8, characterized in that, The absolute light-receiving unit (10) is disposed in the middle of the incremental light-receiving unit (8), and a distance greater than or equal to the distance between it and the incremental light-receiving unit (8) is provided. The interval (11).

10. The angle deflection detection device according to claim 1, characterized in that, The light source (1) is a collimated light source.

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