A non-contact auxiliary positioning laser interferometry system

Abstract

The present invention belongs to the field of high-precision measurement technology, and specifically relates to a non-contact auxiliary positioning laser interferometer measurement system, including a light source for generating monochromatic light of at least two different wavelengths, a measuring head based on the interferometric measurement surface, and a reference system component built based on the interferometric measurement. By using monochromatic light of at least two colors as interference light, and using a reference measuring head and a reference surface as a position reference for the measuring head, the measurement accuracy of the interferometric measurement system can reach the nanometer level, and it is also beneficial to the large-range movement of the measuring head. The present invention is suitable for the measurement of large-caliber and large-angle surfaces, and solves the defects of traditional contact or non-contact measurement systems that the measurement accuracy is restricted by mechanical movement and the white light interferometric measurement range is small.

Description

Technical Field

[0001] The invention belongs to the technical field of high-precision measurement, and in particular relates to a non-contact auxiliary positioning laser interference measurement system. Background Art

[0002] With the rapid development of science and technology, the requirements for the size or shape accuracy of the finishing or super finishing of parts or components in optics, semiconductor electronics, precision engineering, astronomy and aerospace engineering are getting higher and higher, and the requirements for microstructure surface topography measurement systems are also getting higher and higher. According to the different measurement accuracy and range, it can be divided into precision measurement (0.5~0.05μm), ultra-precision measurement (0.05~0.005μm), and nanometer precision measurement (5~0.05nm).

[0003] In traditional contact measurement technology, the stylus tip directly contacts the test surface during measurement. When measuring the test surface profile of soft materials (such as film, aluminum, etc.), the stylus tip will inevitably damage the test surface, making the measurement unable to meet the requirements. For the test surface profile measurement of hard materials (such as bullets, shells, etc.), although the measurement can be achieved, more or less scratches and other damage will be left on the test surface.

[0004] At present, the research on non-contact surface profile measurement technology has received more and more attention. The technology based on the principle of optical interference is the most widely used method for non-contact measurement. Among the interference measurement technologies, the single-wavelength interference measurement technology has the highest measurement accuracy, but this technology has the problem of phase ambiguity when measuring steps, step differences and other morphologies. The measurement range cannot exceed λ / 2, and the measurement range is small. The measurement range of white light interference microscopy technology is larger than that of single-wavelength interference measurement technology, but the measurement efficiency is low, and the measurement accuracy is seriously affected by the phase shift accuracy of the PZT (piezoelectric ceramic driver) module. In addition, due to the limitations of structure and principle, the size and inclination of the measured surface are relatively small, and the measurement applicability of large-diameter and large-angle surface shapes is poor. If the entire surface shape is to be measured, field of view splicing is required. The splicing accuracy and mechanical movement accuracy will affect the measurement accuracy of the final surface shape. Therefore, affected by the PZT phase shift accuracy, image splicing accuracy, mechanical axis movement accuracy, etc., the measurement accuracy of large-diameter, large-angle, step surface, and free-form surface still needs to be further improved. The measurement accuracy of laser interferometry phase-shifting microscopy is higher than that of white light interferometry, but its measurement range is limited, and it is difficult to measure surfaces with large inclination angles and step differences. When measuring large-aperture surfaces, the measurement accuracy is restricted by the mechanical movement accuracy, and the mechanical axis errors are mostly in the micron range.

[0005] With the rapid development of optical precision machining, the application of special surface shapes from small to large (such as 1mm~900mm, or other calibers), small to large angle surface shapes (such as 0~90°), aspheric surface, step surface, etc. is becoming more and more extensive, such as high-end cameras, video cameras, various optical measuring instruments, mobile phone lenses, aerospace optical components, etc. At present, the market demand for highly flexible and high-precision measuring instruments is becoming more and more widespread.

[0006] The use of multi-wavelength (≥2 wavelengths) interferometric measurement technology, through the equivalent wavelength method, and with the help of certain auxiliary means, can overcome the difficulties of single-wavelength absolute interferometric length measurement and greatly increase the measurement range. In addition, combined with phase modulation technology, good measurement accuracy can still be ensured within a larger measurement range.

[0007] However, the traditional multi-wavelength interference measurement technology still has the following problems: First, the multi-wavelength interference microscopy measurement technology uses a combination of white light source and bandpass filter to obtain monochromatic coherent light. During measurement, the filter wheel needs to be rotated in sequence to collect signals of different wavelengths. The measurement efficiency is low, and it is difficult to measure large-aperture and large-angle surfaces. In addition, the coherence and stability of the light source are not as good as those of the laser light source, and the long-term stability of the measurement accuracy is restricted. Second, in order to achieve the measurement of large-aperture, large-angle and special surface shapes, the measuring head needs to move, but when the measuring head moves driven by the mechanical axis, the mechanical axis movement error will be introduced (the mechanical axis movement error is usually in the micron level or even higher. For nanometer precision measuring instruments, the error is too large), which affects the accuracy of the final measurement result. Third, the flexibility of traditional single measurement products is not enough. It is difficult to take into account the measurement of small-aperture, large-aperture, small-angle, large-angle, large-step difference and other surface shapes at the same time, and the product has a limited scope of application. Summary of the invention

[0008] In view of this, the present invention proposes a non-contact auxiliary positioning laser interferometer measurement system, which uses monochromatic light of at least two colors as interference light, and uses a reference measuring head and a reference surface as the position reference of the measuring head, so that the measurement accuracy of the interferometer measurement system can reach the nanometer level, and at the same time is beneficial to the large-range movement of the measuring head. The present invention is suitable for the measurement of large-caliber and large-angle surfaces, and solves the defects of the traditional contact or non-contact measurement system that the measurement accuracy is restricted by mechanical movement and the white light interferometer measurement range is small.

[0009] In order to achieve the above technical objectives, the specific technical solutions adopted by the present invention are:

[0010] A non-contact auxiliary positioning laser interferometry measurement system, comprising:

[0011] a light source for generating monochromatic light of at least two different wavelengths;

[0012] A measuring head, which irradiates the object to be measured with monochromatic light of at least two different wavelengths based on the light source, receives the monochromatic light reflected by the object to be measured, and causes the monochromatic light reflected by the object to be measured to interfere with a portion of the monochromatic light incident on the measuring head;

[0013] A motion component drives the measuring head and / or the measured object to move so that the measured area of ​​the measured object is within the detection range of the measuring head;

[0014] A reference system component includes a reference surface and a reference measuring head; the reference measuring head and one of the reference surfaces form a position reference for the measuring head; the reference measuring head receives the monochromatic light reflected by the reference surface based on the monochromatic light of the light source irradiating the reference surface, so that the monochromatic light reflected by the reference surface interferes with a portion of the monochromatic light incident on the reference measuring head.

[0015] Furthermore, the interference measurement system also includes a calculation module; the calculation module determines the relative displacement information between the measuring head and the reference surface based on the change pattern of the interference fringes generated by the reference measuring head; and determines the surface shape of the object to be measured based on the change pattern of the interference fringes generated by the measuring head when the relative position of the measuring head and the object to be measured changes, the position reference and the relative displacement information.

[0016] Further, at least one of the measuring head and the reference measuring head is configured to include:

[0017] A light transmission port, connecting the light source and the computing module;

[0018] A collimating lens, refracting the incident light from the light transmission port into parallel light;

[0019] A beam splitter, transmitting a portion of the parallel light and reflecting another portion of the parallel light along the original path;

[0020] Wherein: the parallel light transmitted by the beam splitter reaches the measured object and the monochromatic light reflected by the measured object back to the beam splitter forms the measuring light, and the parallel light reflected by the beam splitter along the original path forms the reference light;

[0021] The measuring head further comprises a phase modulation module, and the phase modulation module is used to adjust the optical path difference between the measuring light and the reference light.

[0022] Furthermore, the measuring head also includes a focusing lens; the focusing lens is arranged between the beam splitter and the object to be measured, and the optical axis is parallel to the optical path of the parallel light.

[0023] Furthermore, the phase modulation module adjusts the optical path difference between the measurement light and the reference light based on adjusting the distance between the beam splitter and the collimating lens.

[0024] Further, the reference measurement head irradiates the reference surface based on at least two monochromatic lights of the light source.

[0025] Further, the motion assembly includes a first mechanical arm, a second mechanical arm, a first rotating part and a second rotating part;

[0026] The measuring head is mounted on the first rotating part, and the first rotating part drives the measuring head to rotate along the first rotating axis;

[0027] The first mechanical arm drives the first rotating part to perform a transverse axis movement, and the second mechanical arm drives the second rotating part to perform a longitudinal axis movement perpendicular to the transverse axis movement;

[0028] The object to be measured is mounted on the second rotating part, and the second rotating part drives the object to be measured to rotate along the second rotating axis.

[0029] Further, the reference system assembly includes three groups of reference surfaces and three groups of reference measuring heads corresponding to the three groups of reference surfaces respectively;

[0030] The two groups of reference surfaces are plane mirrors, one group of the plane mirrors is arranged perpendicular to the horizontal axis, and the other group of the plane mirrors is arranged perpendicular to the longitudinal axis;

[0031] Another set of reference surfaces is a curved mirror.

[0032] Furthermore, the laser interferometry system also includes a support frame, and the motion component is installed on the support frame.

[0033] Furthermore, the two groups of plane mirrors are fixed on the supporting frame; and the curved mirror is fixedly arranged relative to the axis of the first rotating shaft or the first mechanical arm.

[0034] By adopting the above technical solution, the present invention can bring the following beneficial effects:

[0035] 1) The present invention adopts a non-contact auxiliary positioning interference measurement system. First, it can significantly increase the moving distance of the measuring head and realize the measurement of large-diameter surfaces. Second, the measuring head has high flexibility in adjusting its position and posture, and can realize the morphology measurement of special surfaces such as aspheric surfaces, step surfaces, diffraction surfaces, free-form surfaces, etc., and can meet the measurement of large-angle surfaces, such as 90° inclination. Third, the measurement results do not require field of view splicing, and the measurement efficiency is high. Fourth, a single device can meet the application of various scenarios, such as the measurement of surfaces with different calibers and different inclination angles.

[0036] 2) The present invention adopts a non-contact interferometric reference measuring head to compensate for the error introduced by the mechanical movement of the moving component, which can achieve high-precision error compensation, especially compensation for the accuracy of a large range of moving distances, making the measurement results more accurate. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] In order to more clearly illustrate the technical solutions of the embodiments of the present disclosure, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present disclosure. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0038] Figure 1 A schematic diagram of an implementation of a non-contact auxiliary positioning laser interferometry measurement system of the present invention;

[0039] Figure 2 It is a schematic diagram of another embodiment of a non-contact auxiliary positioning laser interferometry measurement system of the present invention;

[0040] Figure 3 It is a schematic diagram of another embodiment of a non-contact auxiliary positioning laser interferometry measurement system of the present invention;

[0041] Figure 4 It is a schematic diagram of another embodiment of a non-contact auxiliary positioning laser interferometry measurement system of the present invention;

[0042] Figure 5 It is a schematic diagram of the internal structure of the measuring head in a specific embodiment of the present invention;

[0043] Figure 6 It is a schematic diagram of the internal structure of a reference measuring head in a specific implementation manner of the present invention;

[0044] Figure 7 It is a schematic diagram of the internal structure of another reference measuring head in a specific embodiment of the present invention;

[0045] Figure 8 A schematic diagram of a phase adjustment method of a converging light measuring head in a specific embodiment of the present invention;

[0046] Fig. 9 It is a schematic diagram of another phase adjustment method of the converging light measuring head in a specific embodiment of the present invention;

[0047] Fig.10 A schematic diagram of a phase adjustment method of a collimated light measuring head in a specific embodiment of the present invention;

[0048] Fig.11 It is a schematic diagram of another phase adjustment method of the collimated light measuring head in a specific embodiment of the present invention;

[0049] Wherein: 1. support frame; 2. first reference surface; 3. second reference surface; 4. first mechanical arm; 5. second reference measuring head; 6. fixing block; 7. third reference measuring head; 8. third reference surface; 9. first reference measuring head; 10. second mechanical arm; 11. first rotating shaft; 12. measuring head; 13. second rotating shaft; 14. measured object; 15. signal transmission line; 16. calculation module; 17. light source; 18. detector module; 19. rotating arm; 20. translation stage; 21. light transmission port; 22. incident light; 23. reflected light; 24. collimating lens; 25. PZT module; 26. spectroscope; 27. focusing lens; 29. ​​measuring head housing; 30. optical fiber protective housing; 31. optical fiber; 33. fastening screw; 34. base; 35. adapter plate; 36. light guide housing; 37. flat lens. DETAILED DESCRIPTION

[0050] The embodiments of the present disclosure are described in detail below with reference to the accompanying drawings.

[0051] The following describes the embodiments of the present disclosure through specific examples, and those skilled in the art can easily understand other advantages and effects of the present disclosure from the contents disclosed in this specification. Obviously, the described embodiments are only a part of the embodiments of the present disclosure, rather than all of the embodiments. The present disclosure can also be implemented or applied through other different specific embodiments, and the details in this specification can also be modified or changed in various ways based on different viewpoints and applications without departing from the spirit of the present disclosure. It should be noted that the following embodiments and features in the embodiments can be combined with each other without conflict. Based on the embodiments in the present disclosure, all other embodiments obtained by ordinary technicians in the field without making creative work are within the scope of protection of the present disclosure.

[0052] It should be noted that various aspects of the embodiments within the scope of the appended claims are described below. It should be apparent that the aspects described herein can be embodied in a wide variety of forms, and any specific structure and / or function described herein is merely illustrative. Based on the present disclosure, it should be understood by those skilled in the art that an aspect described herein can be implemented independently of any other aspect, and two or more of these aspects can be combined in various ways. For example, any number of aspects described herein can be used to implement the device and / or practice the method. In addition, other structures and / or functionalities other than one or more of the aspects described herein can be used to implement this device and / or practice this method.

[0053] It should also be noted that the illustrations provided in the following embodiments are only schematic illustrations of the basic concept of the present disclosure. The drawings only show components related to the present disclosure rather than being drawn according to the number, shape and size of components in actual implementation. In actual implementation, the type, quantity and proportion of each component may be changed arbitrarily, and the component layout may also be more complicated.

[0054] Additionally, in the following description, specific details are provided to facilitate a thorough understanding of the examples. However, it will be understood by those skilled in the art that the aspects described may be practiced without these specific details.

[0055] In one embodiment of the present invention, a non-contact auxiliary positioning laser interferometry system is provided, such as Figure 1 or 2 or 3 or 4, including:

[0056] The light source 17 is used to generate at least two monochromatic lights of different wavelengths; the light source 17 of this embodiment is a laser light source 17; the monochromatic lights are at least two;

[0057] The measuring head 12 irradiates the measured object 14 with monochromatic lights of at least two different wavelengths based on the light source 17, receives the monochromatic light reflected by the measured object 14, and causes the monochromatic light reflected by the measured object 14 to interfere with a part of the monochromatic light incident on the measuring head 12;

[0058] The motion component drives the measuring head 12 and / or the measured object to move so that the measured area of ​​the measured object 14 is within the detection range of the measuring head 12; the specific structure of the motion component of this embodiment is not limited here, and its movement is driven by mechanical movement;

[0059] The reference system assembly includes a reference surface and a reference measuring head; one of the reference measuring surface and the reference measuring head moves with the measuring head 12, and the other forms a position reference; the reference measuring head irradiates the reference surface with monochromatic light from the light source 17, receives the monochromatic light reflected by the reference surface, and causes the monochromatic light reflected by the reference surface to interfere with a part of the monochromatic light incident on the reference measuring head;

[0060] The detector module 18 receives the interference light sent back by the measuring head 12 and the reference measuring head and converts it into interference fringes;

[0061] The calculation module determines the relative displacement information between the measuring head 12 and the reference surface based on the change law of the interference fringes generated by the reference measuring head; and determines the surface shape of the object 14 to be measured based on the change law of the interference fringes generated by the measuring head 12 when the relative position of the measuring head 12 and the object 14 to be measured changes, the position reference and the relative displacement information.

[0062] When the measuring head 12 measures the surface shapes of different types of objects (especially large-diameter and large-angle surfaces), it needs to use motion components (such as linear translation table 20, rotation table, etc.) because it needs linear movement or rotational movement. At this time, mechanical axis error will be introduced. As the displacement distance increases, the introduced measurement error will also increase. This embodiment uses a non-contact interferometric reference measuring head to compensate for the error introduced by mechanical movement, thereby achieving high-precision error compensation, especially compensation for the accuracy of a large range of moving distances, so that the measurement results are more accurate.

[0063] The reference surface of this embodiment is preferably a mirror surface or other reflective surface with very small roughness as an ideal surface.

[0064] In this embodiment, one of the reference measuring heads or reference surfaces moves or rotates coaxially with the measuring head 12 in a fixed relative position, and the other reference measuring head or reference surface is fixed somewhere in the laser interferometer measurement system to form a position reference for the movement of the measuring head 12.

[0065] In this embodiment, the number of reference system components is at least equal to the number of moving dimensions of the measuring head 12. When the movement of the measuring head 12 includes pitch movement, it is also necessary to add reference system components for responding to the pitch change of the measuring head 12.

[0066] The detector module 18 and the calculation module of this embodiment adopt a conventional combination that can analyze interference fringes and calculate surface shapes, which is not limited here.

[0067] This embodiment abandons the traditional mechanical positioning and adopts a new position reference system based on interference measurement accuracy, which greatly improves the positioning accuracy of the measuring head 12, with an accuracy higher than λ / 2, and realizes nanometer precision measurement (5~0.05nm).

[0068] In this embodiment, at least one of the measuring head 12 and the reference measuring head is configured to include:

[0069] A light transmission port 21, connected to the light source 17 and the measurement system;

[0070] The collimating lens 24 refracts the incident light 22 of the light transmission port 21 into parallel light;

[0071] The beam splitter 26 transmits part of the parallel light and reflects part of the original path;

[0072] Wherein: the parallel light transmitted by the beam splitter 26 reaches the object 14 to be measured and is reflected by the object 14 back to the beam splitter 26 as the optical travel measurement light, and the parallel light reflected by the beam splitter 26 along the original path forms the reference light;

[0073] The measuring head 12 further includes a phase modulation module, which is used to adjust the optical path difference between the measuring light and the reference light. The phase modulation module of this embodiment adjusts the optical path difference between the measuring light and the reference light based on adjusting the distance between the beam splitter 26 and the collimating lens 24 .

[0074] The measuring head 12 and the reference measuring head of this embodiment may adopt the same structure.

[0075] In some embodiments, the measuring head 12 further includes a focusing lens 27 ; the focusing lens 27 is disposed between the beam splitter 26 and the object to be measured 14 , and the optical axis is parallel to the optical path of the parallel light.

[0076] In this embodiment, for the object 14 with a large curvature, the measuring head 12 can use a converging light spot (i.e., reduce the diameter of the light spot) to measure its shape, which can reduce the loss rate of reflected light and improve the lateral resolution during surface measurement.

[0077] In this embodiment, if Figure 5 As shown, the measuring principle of the measuring head 12 with a focused light spot is as follows: the incident light 22 enters through the signal light transmission port 21, is collimated by the collimating lens 24, and after the incident light 22 is split by the beam splitter 26, part of the light is reflected as the reference light, and part of the light is transmitted, converged on the measured object 14 through the focusing lens 27, and then reflected as the measuring light. The reference light and the measuring light meet at the beam splitter 26 and interfere, and the reflected light 23 is detected by the detector module 18. In order to realize phase modulation, the PZT module 25 (phase modulation module) drives the beam splitter 26 to move up and down, so that the optical path difference between the reference light and the measuring light changes, realizing phase modulation, and realizing high-precision morphology measurement through phase shifting. The reflected light 23 is a phase-modulated interference signal. The fringe change pattern of the interference signal reflects the position change between the object 14 to be measured and the measuring head 12. After being substituted into the reference system formed by the reference system components and subsequent data processing (such as initial phase extraction, surface shape fitting, etc.), the surface shape of the object 14 to be measured can be calculated.

[0078] Similarly, in some embodiments, the reference measuring head can also choose whether to use a convergent light spot. If the reference surface is a plane, the parallel light spot of the above embodiment can be used. If the reference surface is a curved surface, the convergent light spot of this embodiment can also be used. The reference measuring head can also choose to irradiate at least two monochromatic lights based on the light source on the reference surface to further improve the positioning accuracy.

[0079] In one embodiment, the motion assembly includes a first mechanical arm 4, a second mechanical arm 10, a first rotating part, and a second rotating part;

[0080] The first mechanical arm 4 drives the first rotating part to perform a transverse axis movement, and the second mechanical arm 10 drives the second rotating part to perform a longitudinal axis movement perpendicular to the transverse axis movement;

[0081] The measuring head 12 is mounted on the first rotating part and rotates along a first rotating axis 11 which is perpendicular to both the horizontal axis and the vertical axis.

[0082] The object to be measured is mounted on the second rotating part and rotates along a second rotating axis 13 which is perpendicular to both the horizontal axis and the vertical axis.

[0083] In this embodiment, the horizontal axis corresponds to the X-axis in space, and the vertical axis corresponds to the Y-axis in space.

[0084] In this embodiment, the reference system assembly includes three groups of reference surfaces and three groups of reference measuring heads corresponding to the three groups of reference surfaces respectively;

[0085] The two groups of reference surfaces are plane mirrors, one group of plane mirrors is arranged perpendicular to the horizontal axis, and the other group of plane mirrors is arranged perpendicular to the vertical axis;

[0086] Another set of reference surfaces is a curved mirror, which cooperates with the third reference measuring head 7 to compensate for the disturbance error of the measuring head 12 in the direction of the optical axis. For example, if the measuring head 12 has displacement fluctuations along the optical axis, the third reference measuring head 7 can monitor the error and then deduct the error from the measurement result of the measuring head 12, thereby achieving the compensation effect.

[0087] The laser interferometer measurement system further comprises a support frame 1 , on which the motion components are mounted.

[0088] The two sets of plane mirrors are both fixed on the supporting frame 1 ; the curved mirror is fixedly arranged relative to the axis of the first rotating shaft 11 or the first mechanical arm 4 .

[0089] like Figure 1-4 As shown, the motion dimension of the measuring head 12 of this embodiment is two-dimensional + rotation, and two sets of reference system components for calibrating the two-dimensional motion distance and one set of reference system components for calibrating the rotation pitch are provided. Among them, the reference system components for calibrating the two-dimensional running distance use a plane mirror as a reference surface, that is, the first reference measuring head 9 and the second reference measuring head 5 are used to detect the motion distance of the measuring head 12 driven by the second mechanical arm 10 and the first mechanical arm 4 in the optical axis direction. The reference system components for calibrating the rotation motion pitch include a third reference surface 8 and a third reference measuring head 7 that cooperate with each other.

[0090] like Figure 1-4As shown, this embodiment includes three groups of reference measuring heads. Multiple monochromatic lights emitted by a light source 17 (the light source module includes multiple monochromatic lights. Within the visible light or infrared light wavelength range, the monochromatic lights of different wavelengths can be freely combined and outputted through a control system) are transmitted to the measuring head 12 and the first reference measuring head 9, the second reference measuring head 5, and the third reference measuring head 7 through a signal transmission line 15 (the signal line includes optical fibers and wires that can transmit optical signals and electrical signals, and the schematic diagram is simplified). A part of the incident light is returned through the beam splitter 26 in the measuring head, and another part of the incident light is reflected and returned through the object to be measured 14 or the first reference plane 2, the second reference plane 3, and the third reference plane 8. The two parts of light meet at the beam splitter 26 and interfere. The interference signal is transmitted to the detector module 18 through the signal transmission line 15. The signal collected by the detector module 18 is transmitted to the calculation module 16 after being preliminarily processed by itself. Further processing is completed in the calculation module 16 to obtain the deviation data of the three-dimensional morphology of the object to be measured 14, and the calculation module 16 can display the data.

[0091] The first reference measuring head 9, the second reference measuring head 5 and the third reference measuring head 7 of this embodiment are used to measure the displacement distance of the mechanical axis and accurately locate the position of the measuring head 12 or the object 14 to be measured in space. The measured data can be used to compensate for the error introduced when the first rotating shaft 11 moves.

[0092] The second reference measuring head 5 is used to compensate for the mechanical error of the first mechanical arm 4 (which can perform vertical reciprocating motion) during vertical movement.

[0093] The third reference measuring head 7 compensates for the mechanical error generated when the first rotating shaft 11 rotates, that is, compensates for the disturbance error of the measuring head 12 in the direction of the optical axis. For example, if the measuring head 12 has displacement fluctuations along the optical axis, the third reference measuring head 7 can monitor the error and then deduct the error from the measurement result of the measuring head 12 to achieve the compensation effect.

[0094] The first reference measuring head 9 is used to compensate for the mechanical error generated when the second mechanical arm 10 (capable of horizontal reciprocating motion) moves horizontally.

[0095] The reference measuring head measures the mechanical axis displacement distance (because the mechanical axis displacement accuracy is low and the spatial position of the object is not accurately positioned, the optical means in this embodiment is used to accurately position the spatial position of the object), and subtracts or adds this value to the measurement data of the measuring head 12, so that the laser interferometer measurement system with a mechanical coordinate reference system can obtain nanometer-level precision measurement results.

[0096] In this embodiment, the third reference surface 8 and the measuring head 12 are fixed together, connected by the first rotating shaft 11, and fixed on the first mechanical arm 4. The third reference surface 8 and the measuring head 12 are driven to rotate by the first rotating shaft 11, and the surface shape of the measured object 14 can be measured. The second reference measuring head 5 is fixed on the first mechanical arm 4, and can move vertically back and forth on the first mechanical arm 4. The second reference measuring head 5 can measure the vertical moving distance of the first mechanical arm 4 in real time, assist in positioning the vertical moving distance of the measuring head 12, and compensate for the mechanical error when the first mechanical arm 4 moves. The third reference surface 8 of this embodiment is a curved surface, which is convenient for being within the measuring range of the third reference measuring head 7 when rotating around the first rotating shaft 11. The third reference surface 8 of this embodiment can form the reference reference coordinate of the measuring head alone, or it can form the reference coordinate of the measuring head after positioning based on the reference coordinate formed by the first reference surface 2 and the second reference surface 3.

[0097] In addition, the second reference measuring head 5 and the third reference measuring head 7 are fixed on the first mechanical arm 4 through the fixing block 6, and the second reference measuring head 5 and the third reference measuring head 7 are installed on the same mechanical axis. In actual measurement, the distance between the third reference measuring head 7 and the third reference surface 8 is fixed (can be calibrated in advance). When the measuring head 12 and the third reference surface 8 are rotated for measurement, due to the existence of mechanical disturbance, the distance between the third reference measuring head 7 and the third reference surface 8 will change slightly, and this change will directly affect the measurement accuracy of the system. Therefore, it is necessary to deduct the measurement data of the third reference measuring head 7 from the measurement data of the measuring head 12 to compensate for the error introduced during mechanical rotation.

[0098] Finally, the first reference measuring head 9 is fixed on the second robotic arm 10, and the second robotic arm 10 can drive the first reference measuring head 9 to move in the horizontal direction. The first reference measuring head 9 is combined with the first reference surface 2 to realize the horizontal positioning of the measuring head 12 and compensate for the mechanical error introduced when the second robotic arm 10 moves in the horizontal direction.

[0099] In one embodiment, Figure 4 As shown, the first reference measuring head 9 and the second reference measuring head 5 are fixed on the third reference surface 8, and the third reference surface is fixed on the first robotic arm 4; the third reference measuring head 7 and the measuring head 12 are installed on the first rotating shaft 11. The third reference surface 8 of this embodiment is an annular surface, which encloses the motion range of the third reference measuring head 7. The rest of the working principles are similar to the above-mentioned embodiments.

[0100] In order to complete the measurement of the surface shape of the measured object 14, the measuring head 12 needs to move vertically, horizontally and rotationally, and the measured object 14 needs to rotate, driven by the second rotating shaft 13. The first reference measuring head 9, the second reference measuring head 5, and the third reference measuring head 7 are mainly used to assist in locating the position of the measuring head 12 in space and compensate for the mechanical axis error. The system can realize the measurement of small, medium and large diameter surfaces (such as 1mm~900mm, etc., or other diameters), as well as the measurement of large inclination surfaces (such as 0~90°, etc.). It is recommended that the first reference measuring head 9, the second reference measuring head 5, and the third reference measuring head 7 be installed with the central axis passing through the center position of the first rotating shaft 11. According to the Abbe principle, the measurement accuracy of this configuration is higher. In addition, the measurement scanning mode of the system for the measured object 14 may include spiral scanning, equidistant scanning, custom scanning mode, etc.

[0101] like Figure 5 As shown, the measuring principle of the measuring head 12 is as follows: the incident light 22 enters through the signal light transmission port 21, is collimated by the collimating lens 24, and after the incident light 22 is split by the beam splitter 26, part of the light is reflected as the reference light, and part of the light is transmitted, and converged on the measured object 14 through the focusing lens 27, and then reflected as the measuring light. The reference light and the measuring light meet at the beam splitter 26 and interfere, and the reflected light 23 is detected by the detector module 18. In order to achieve phase modulation, the PZT module 25 drives the beam splitter 26 to move up and down, so that the optical path difference between the reference light and the measuring light changes, and phase modulation is achieved. High-precision morphology measurement can be achieved through phase shifting. The reflected light 23 is a phase-modulated signal. After the modulated signal is subjected to subsequent data processing (such as initial phase extraction, surface shape fitting, etc.), the measured surface shape error can be calculated.

[0102] like Figure 6 As shown, the second reference measuring head 5 adopts the same structure as the measuring head 12. Because the third reference surface 8 has a certain curvature, in order to improve the utilization rate of the reflected light, a focusing optical path structure is adopted.

[0103] like Figure 7 As shown, the first reference measuring head 9 and the third reference measuring head 7 adopt a collimated structure. Because the first reference plane 2 and the second reference plane 3 are planes, and the system has a large horizontal and vertical moving distance (such as 1mm~900mm, or other distances), it is more advantageous to use parallel light measurement.

[0104] The present invention has two embodiments of the measuring head. Figure 8The first structure is shown. The incident light 22 enters the measuring head from the optical fiber 31 and is emitted through the end face. Part of the light is reflected by the beam splitter 26 as the reference light, and part of the light is transmitted. After passing through the focusing lens 27, it is focused on the measured object 14 and then reflected. The reflected light 23 is used as the measuring light. The reference light and the measuring light interfere with each other after they meet. The phase shift modulation principle is: the PZT module 25 is fixed to the base 34, the focusing lens 27 is fixed to the base 34, the base 34 and the optical fiber protective housing 30 are fixed together by fastening screws 33 (or other fixing methods), the optical fiber protective housing 30 and the optical fiber 31 are fixed together, and the PZT module 25 drives the base 34 and the optical fiber protective housing 30 to move back and forth, thereby changing the optical path difference between the reference light and the measuring light to achieve phase modulation.

[0105] Fig. 9 The above structure has been partially modified, and the base 34 has been divided into two parts, namely an adapter plate 35 and a light guide housing 36. The light guide housing 36 is fixed to the probe housing 29, and the adapter plate 35 is fixed to the optical fiber protection housing 30. The PZT module 25 drives the adapter plate 35 and the optical fiber protection housing 30 to move back and forth, thereby changing the optical path difference between the reference light and the measurement light to achieve phase modulation.

[0106] like Fig.10 , 11 As shown, in Figure 8 , 9 Based on the above, some structural modifications have been made. There are two structures in total: Fig.10 Yes Figure 8 The structure of the invention is modified by changing the focusing lens 27 to a flat lens 37, so that the outgoing light is a collimated light beam. Fig.11 Yes Figure 8 The structure of the invention is modified by changing the focusing lens 27 to a flat lens 37, so that the outgoing light is a collimated light beam.

[0107] In one embodiment, Figure 2 As shown, it is a schematic diagram of an implementation method of a non-contact auxiliary positioning laser interferometer measurement system. The spatial position relationship between the second reference measuring head 5 and the measuring head 12 has changed. The third reference surface 8 is fixed on the first mechanical arm 4. The second reference measuring head 5 and the measuring head 12 are fixed on the rotating arm 19. The rotating arm 19 can rotate around the first rotating shaft 11. The second reference measuring head 5 and the measuring head 12 always perform co-optical axis (or mechanical axis) measurement. This matching mode can effectively compensate for the mechanical disturbance introduced in the optical axis direction when the first rotating shaft 11 rotates, because the disturbance has a serious interference on the measurement accuracy of the measuring head 12. The reference coordinate system of this embodiment is directly established based on the reference surface with a fixed position, and accuracy compensation can be performed.

[0108] In one embodiment, Figure 3As shown, it is a schematic diagram of another implementation method of a non-contact auxiliary positioning laser interferometer measurement system. The first reference measuring head 9 and the third reference measuring head 7 are fixed on the bottom measuring platform, so that the measuring head 12 only needs to make a rotational movement, and the translation platform 20 can perform vertical and horizontal reciprocating movements. The first reference measuring head 9 and the third reference measuring head 7 assist in locating the spatial position of the object to be measured 14 and perform error compensation.

[0109] The above is only a specific implementation of the present disclosure, but the protection scope of the present disclosure is not limited thereto. Any changes or substitutions that can be easily thought of by a person skilled in the art within the technical scope disclosed in the present disclosure should be included in the protection scope of the present disclosure. Therefore, the protection scope of the present disclosure should be based on the protection scope of the claims.

Claims

1. A non-contact auxiliary positioning laser interferometry measurement system, characterized in that: include: a light source for generating monochromatic light of at least two different wavelengths; A measuring head, which irradiates the object to be measured with monochromatic light of at least two different wavelengths based on the light source, receives the monochromatic light reflected by the object to be measured, and causes the monochromatic light reflected by the object to be measured to interfere with a portion of the monochromatic light incident on the measuring head; A motion component drives the measuring head and / or the measured object to move so that the measured area of ​​the measured object is within the detection range of the measuring head; A reference system assembly, comprising a reference surface and a reference measuring head; the reference measuring head and one of the reference surfaces form a position reference for the measuring head; The reference measuring head irradiates the reference surface with the monochromatic light of the light source, receives the monochromatic light reflected by the reference surface, and causes the monochromatic light reflected by the reference surface to interfere with a portion of the monochromatic light incident on the reference measuring head; The interferometric measurement system further includes a calculation module; the calculation module determines the relative displacement information between the measuring head and the reference surface based on the variation law of the interference fringes generated by the reference measuring head; and determines the surface shape of the measured object based on the variation law of the interference fringes generated by the measuring head when the relative position between the measuring head and the measured object changes, the position reference and the relative displacement information; At least one of the measuring head and the reference measuring head is configured to include: A light transmission port, connecting the light source and the computing module; A collimating lens, refracting the incident light from the light transmission port into parallel light; A beam splitter, transmitting a portion of the parallel light and reflecting another portion of the parallel light along the original path; Wherein: the parallel light transmitted by the beam splitter reaches the measured object and the monochromatic light reflected by the measured object back to the beam splitter forms the measuring light, and the parallel light reflected by the beam splitter along the original path forms the reference light; The measuring head further comprises a phase modulation module, and the phase modulation module is used to adjust the optical path difference between the measuring light and the reference light.

2. The interferometric measurement system according to claim 1, characterized in that: The measuring head further comprises a focusing lens; the focusing lens is arranged between the beam splitter and the object to be measured, and the optical axis of the focusing lens is parallel to the optical path of the parallel light.

3. The interferometric measurement system according to claim 1, characterized in that: The phase modulation module adjusts the optical path difference between the measurement light and the reference light based on adjusting the distance between the beam splitter and the collimating lens.

4. The interferometric measurement system according to claim 1, characterized in that: The reference measuring head irradiates the reference surface based on at least two monochromatic lights of the light source.

5. The interferometric measurement system according to claim 1, characterized in that: The motion assembly includes a first mechanical arm, a second mechanical arm, a first rotating part and a second rotating part; The measuring head is mounted on the first rotating part, and the first rotating part drives the measuring head to rotate along the first rotating axis; The first mechanical arm drives the first rotating part to perform a transverse axis movement, and the second mechanical arm drives the second rotating part to perform a longitudinal axis movement perpendicular to the transverse axis movement; The object to be measured is mounted on the second rotating part, and the second rotating part drives the object to be measured to rotate along the second rotating axis.

6. The interferometric measurement system according to claim 5, characterized in that: The reference system assembly includes three groups of reference surfaces and three groups of reference measuring heads corresponding to the three groups of reference surfaces respectively; The two groups of reference surfaces are plane mirrors, one group of the plane mirrors is arranged perpendicular to the horizontal axis, and the other group of the plane mirrors is arranged perpendicular to the longitudinal axis; Another set of reference surfaces is a curved mirror.

7. The interferometric measurement system according to claim 6, characterized in that: The laser interferometry system further comprises a supporting frame, and the motion assembly is mounted on the supporting frame.

8. The interferometric measurement system according to claim 7, characterized in that: The two groups of plane mirrors are both fixed on the supporting frame; the curved mirror is fixedly arranged relative to the axis of the first rotating shaft or the first mechanical arm.

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