A contact-assisted positioning laser interferometry system

Abstract

The present invention belongs to the field of precision measurement technology, and specifically relates to a contact-type auxiliary positioning laser interferometer measurement system, comprising a light source, a measuring head, a motion component and a reference system component; the present invention can significantly increase the moving distance of the measuring head, realize the measurement of large-diameter surfaces, and realize the morphology measurement of special surfaces such as aspheric surfaces, step surfaces, diffraction surfaces, and free-form surfaces, and the measurement results do not require field of view splicing, and the measurement efficiency is high; at the same time, through the contact-type reference measuring head auxiliary positioning mode, the error introduced by mechanical movement is compensated, and high-precision error compensation can be achieved, especially the compensation of micro-displacement and large-range moving distance accuracy, so that the measurement result is more accurate.

Description

Technical Field

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

[0002] Non-contact profile measurement technology has received increasing attention, and the principle of optical interference is the most widely used method for non-contact measurement. In this field, single-wavelength interference measurement has the highest accuracy, but there will be phase ambiguity problems when measuring steps and step differences, the measurement accuracy cannot exceed λ / 2, and the measurement range is small. The measurement range of white light interference microscopy technology is larger than that of a single wavelength, but the measurement efficiency is low. The size and inclination of the measured surface are relatively small, and its applicability to the measurement of large-aperture and large-angle surfaces is poor. If the entire surface is to be measured, field of view splicing is required. The measurement accuracy of laser interferometric phase-shifting microscopy measurement technology is higher than that of white light interferometry technology, but 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. Summary of the invention

[0003] In view of this, the present invention proposes a contact-assisted positioning multi-wavelength laser interferometer measurement system, in which a reference system component for measuring displacement based on interference technology reflects the relative displacement of a measuring head, eliminates the mechanical error of a mechanical device that drives the measuring head to move, and increases the measurement accuracy to the nanometer level. The system accuracy, measurement distance and flexibility are also greatly improved.

[0004] In order to achieve the above technical objectives, the specific technical solutions adopted by the present invention are:

[0005] A contact-type auxiliary positioning laser interferometric measurement system, comprising: a light source, a measuring head, a motion component and a reference system component;

[0006] The light source is used to generate monochromatic light;

[0007] The reference system assembly comprises a reference surface and a reference measuring head; the reference measuring head and one of the reference surface form a position reference for the measuring head;

[0008] The 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;

[0009] At least one of the measuring head and the reference measuring head is a contact measuring head;

[0010] The contact measuring head irradiates the stylus with the monochromatic light, receives the monochromatic light reflected by the stylus, and causes the monochromatic light reflected by the stylus to interfere with a portion of the monochromatic light incident on the measuring head;

[0011] During measurement, the end of the stylus contacts the reference surface or the object to be measured, and the stylus moves up and down along with the surface shape of the reference surface or the object to be measured;

[0012] 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;

[0013] The contact type measuring head comprises:

[0014] A first light transmission port, connected to the light source and the computing module;

[0015] A first collimating lens is arranged on the outgoing light path of the first light transmission port, and the optical axis is coaxial with the first light transmission port;

[0016] A first beam splitter is arranged on the outgoing light path of the first collimating lens, and the angle between the reflecting surface and the optical axis of the first collimating lens is 45°;

[0017] a reflector, arranged on an outgoing optical path of the monochromatic light reflected from the first collimating lens by the first beam splitter, and arranged parallel to the optical axis of the first collimating lens;

[0018] The contact pin is arranged on the optical path of the transmitted light of the first beam splitter.

[0019] Furthermore, the parallel light transmitted by the beam splitter reaches the stylus and is reflected by the stylus to reach the first light transmission port, and the monochromatic light forms the measuring light; the parallel light reflected by the reflector to the first beam splitter and reaches the first light transmission port forms the reference light;

[0020] The measuring light and the reference light interfere with each other to form the interference fringes.

[0021] Furthermore, the contact type measuring head further comprises a posture sensing optical path; the posture sensing optical path senses the posture of the stylus.

[0022] Furthermore, the posture sensing optical path includes:

[0023] A second light transmission port, used for emitting detection light;

[0024] A second collimating lens is arranged on the outgoing light path of the second light transmission port, and the optical axis is coaxial with the second light transmission port;

[0025] A second beam splitter is arranged on the outgoing light path of the second collimating lens, and the angle between the reflecting surface and the optical axis of the second collimating lens is 45°;

[0026] A first focusing lens is arranged on an outgoing light path of the detection light reflected from the second beam splitter by the second beam splitter;

[0027] A first detector is arranged on the outgoing light path of the first focusing lens;

[0028] A third beam splitter is arranged on the transmission output light path of the second beam splitter; the angle between the reflective surface and the optical axis of the first collimating lens is 45°;

[0029] A second focusing lens is arranged on an outgoing light path of the detection light reflected by the second beam splitter from the second collimating lens;

[0030] A third detector is arranged on the outgoing light path of the second focusing lens;

[0031] Wherein: the reflective surface is arranged on the reflected outgoing light path of the third beam splitter; the first detector and the second detector sense the posture change of the stylus based on the change of the light intensity and / or the change of the light position of the received detection light.

[0032] Furthermore, the stylus is a T-shaped stylus, the top of which is a plane reflective surface, and the bottom of which is a probe; the plane reflective surface is perpendicular to the axis of the probe.

[0033] Furthermore, the planar reflecting surface is parallel to the optical axis of the second focusing lens and is arranged on an outgoing optical path of the reflected light of the third beam splitter.

[0034] Furthermore, the interference measurement system also includes an actuator; the actuator adjusts the contact measurement head based on the sensing result of the posture sensing optical path so that the central axis of the probe is parallel to or coincides with the optical axis of the first collimating lens.

[0035] Furthermore, the first detector is a four-quadrant position detector for sensing changes in the light spot position; and the second detector is used to detect light intensity.

[0036] By adopting the above technical solution, the present invention can bring the following beneficial effects:

[0037] The present invention adopts a reference system component based on interference technology to measure the displacement to react to the relative displacement of the measuring head, thereby eliminating the mechanical error of the mechanical device driving the measuring head to move, and improving the measurement accuracy to nanometer level.

[0038] The contact measuring head of the present invention can significantly increase the moving distance of the measuring head and realize the measurement of large-diameter surface shapes;

[0039] The reference system established by the present invention makes it unnecessary to stitch the fields of view for the measurement results, and the measurement efficiency is high. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] 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.

[0041] Figure 1 It is a structural schematic diagram of a contact-type auxiliary positioning laser interferometry measurement system in a specific implementation manner of the present invention;

[0042] Figure 2 It is a structural schematic diagram of another contact-type auxiliary positioning laser interferometry measurement system in a specific embodiment of the present invention;

[0043] Figure 3 A schematic diagram of the external profile of a contact type measuring head in a specific embodiment of the present invention;

[0044] Figure 4 It is a schematic diagram of the internal structure of the contact type measuring head in a specific embodiment of the present invention;

[0045] Figure 5 This is a schematic diagram of the internal structure of a measuring head in a specific embodiment of the present invention;

[0046] Figure 6 It is a schematic diagram of the internal structure of another measuring head in a specific embodiment of the present invention;

[0047] Wherein: 1. Support frame; 2. First reference measuring head; 3. First reference surface; 4. Third reference surface; 5. Second reference surface; 6. Second reference measuring head; 7. First mechanical arm; 8. Third reference measuring head; 9. First rotating shaft; 10. Second mechanical arm; 11. Measuring head; 12. Object to be measured; 13. Second rotating shaft; 14. Light source; 15. Detector module; 16. Signal line; 17. Calculation module; 18. Translation stage; 19. Stylus; 20. First lens barrel; 21. Second lens barrel; 22. First light transmission port; 23. First detector; 24. The third lens barrel; 25. The second light transmission port; 26. The second detector; 27. The stylus support module; 28. The third beam splitter; 29. ​​Incident light ray one; 30. The reflector; 31. Reflected light ray one; 32. The first collimating lens; 33. The first beam splitter; 34. The first focusing lens; 35. The second collimating lens; 36. The second beam splitter; 37. The second focusing lens; 38. The third focusing lens; 39. The PZT module; 40. The optical fiber; 41. The incident light ray two; 42. Reflected light ray two; 43. The optical fiber end face; 44. The third collimating lens. DETAILED DESCRIPTION

[0048] The embodiments of the present disclosure are described in detail below with reference to the accompanying drawings.

[0049] 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.

[0050] 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.

[0051] 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.

[0052] 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.

[0053] In one embodiment of the present invention, a contact-assisted positioning laser interferometry system is provided, such as Figure 1 , 2 The components shown include: a light source 14, a measuring head 11, a motion component and a reference system component;

[0054] The light source 14 is used to generate monochromatic light of at least two different wavelengths;

[0055] The reference system assembly 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 11;

[0056] The motion component drives the measuring head 11 and / or the object to be measured to move so that the measured area of ​​the object to be measured 12 is within the detection range of the measuring head 11;

[0057] At least one of the measuring head 11 and the reference measuring head is a contact measuring head;

[0058] The contact measuring head irradiates the monochromatic light of the light source 14 on the stylus 19, receives the monochromatic light reflected by the stylus 19, and causes the monochromatic light reflected by the stylus 19 to interfere with a part of the monochromatic light incident into the contact measuring head;

[0059] During measurement, the end of the stylus 19 contacts the reference surface or the object 12 to be measured, and the stylus 19 moves up and down along with the surface shape of the reference surface or the object 12 to be measured.

[0060] In this embodiment, the light source 14 is a laser light source 14, and there are at least two groups of monochromatic lights. The light can be transmitted to the measuring head 11 or the reference measuring head based on the optical fiber 40 or other methods. The measuring head 11 selects the wavelength combination of the two groups of monochromatic lights according to the needs.

[0061] In this embodiment, one of the reference surface and the reference measuring head moves with the measuring head 11, and the other forms a position reference; during the measurement process, a three-dimensional coordinate system is established based on the position reference; when the measuring head 11 moves in the three-dimensional coordinate system, the position change between the reference measuring head and the reference surface sensed by the reference measuring head is brought into this three-dimensional coordinate system, so that the measuring head 11 can be accurately positioned.

[0062] The basic principle of the contact measuring head of this embodiment is: based on the optical components inside the contact measuring head, the monochromatic light is first split, a part of the split light is reflected to the receiving port through the probe, and a part is reflected back to the same receiving port through mirror reflection; the two parts of light have an optical path difference, and after being received by the receiving port, the two parts of light interfere with each other to generate interference fringes, and the displacement distance of the stylus 19 can be calculated according to the change law of the interference fringes. The accuracy of this measurement method is higher than λ / 2, and nanometer precision measurement (5~0.05nm) is achieved.

[0063] At the same time, the measuring head 11 of this embodiment can adopt a non-contact measuring head, based on the monochromatic light of the light source 14 irradiating the object to be measured 12, receiving the monochromatic light reflected by the object to be measured 12, so that the monochromatic light reflected by the object to be measured 12 interferes with a part of the monochromatic light incident on the object to be measured 12; and the non-contact measuring head uses at least two monochromatic lights to measure the relative displacement between the measuring head 11 and the object to be measured 12.

[0064] The interference measurement system of this embodiment also includes a calculation module 17; the calculation module 17 determines the relative displacement information between the measuring head 11 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 12 to be measured based on the change pattern of the interference fringes generated by the measuring head 11 when the relative position of the measuring head 11 and the object 12 to be measured changes, the position reference and the relative displacement information.

[0065] When the measuring head 11 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 18, 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 can compensate for the error introduced by mechanical movement through the calculation result of the contact interferometric reference measuring head, and can achieve high-precision error compensation, especially compensation for the accuracy of a large range of moving distances, so that the measurement result is more accurate.

[0066] In this embodiment, the number of reference system components is at least equal to the moving dimension of the measuring head 11. When the movement of the measuring head 11 includes pitch movement, it is also necessary to add reference system components for responding to the pitch change of the measuring head 11.

[0067] In one embodiment, Figure 3As shown, the contact measuring head includes:

[0068] A first light transmission port 22 connected to the light source 14 and the computing module 17;

[0069] A first collimating lens 32 is disposed on the outgoing light path of the first light transmission port 22, and the optical axis is coaxial with the first light transmission port 22;

[0070] The first beam splitter 33 is arranged on the outgoing light path of the first collimating lens 32, and the angle between the reflecting surface and the optical axis of the first collimating lens 32 is 45°;

[0071] The reflector 30 is arranged on the outgoing light path of the monochromatic light transmitted from the first collimating lens 32 and reflected by the first beam splitter 33, and is arranged parallel to the optical axis of the first collimating lens 32;

[0072] The contact pin 19 is disposed on the optical path of the transmitted light of the first beam splitter 33 .

[0073] In this embodiment, the first light transmission port 22 transmits a group of monochromatic light divergently, and the combination of the first collimating lens 32, the first beam splitter 33, the reflector 30 and the stylus 19 can complete the functions of the above-mentioned embodiment, which is not limited here. In this embodiment, the parallel light transmitted by the beam splitter reaches the stylus 19 and the monochromatic light reflected by the stylus 19 to reach the first light transmission port 22 forms the measurement light; the parallel light reflected by the reflector 30 to the first beam splitter 33 and reaches the first light transmission port 22 forms the reference light;

[0074] Interference occurs between the measurement light and the reference light due to the optical path difference.

[0075] When the stylus 19 slides along the surface of the measured object 12 or the reference surface, the optical path between the stylus 19 and the first light transmission port 22 changes, while the optical path between the reflector 30 and the first light transmission port 22 remains unchanged, that is, the above-mentioned optical path difference changes, and the measuring light received from the first light transmission port 22 and the reference light produce constantly changing interference fringes after passing through the grating.

[0076] In one embodiment, the contact measurement head further includes a posture sensing optical path; the posture sensing optical path senses the posture of the stylus 19 .

[0077] The attitude sensing optical path includes:

[0078] The second light transmission port 25 is used to emit detection light;

[0079] A second collimating lens 35 is disposed on the outgoing light path of the second light transmission port 25, and the optical axis is coaxial with the second light transmission port 25;

[0080] The second beam splitter 36 is arranged on the outgoing light path of the second collimating lens 35, and the angle between the reflecting surface and the optical axis of the second collimating lens 35 is 45°;

[0081] The first focusing lens 34 is arranged on the outgoing light path of the detection light reflected from the second beam splitter 36 by the second beam splitter 36;

[0082] The first detector 23 is arranged on the outgoing light path of the first focusing lens 34;

[0083] The third beam splitter 28 is arranged on the transmission outgoing light path of the second beam splitter 36; the angle between the reflective surface and the optical axis of the first collimating lens 32 is 45°;

[0084] A second focusing lens 37 is arranged on the outgoing light path of the detection light reflected by the second beam splitter 36 from the second collimating lens 35;

[0085] A second detector is arranged on the outgoing light path of the second focusing lens 37;

[0086] Wherein: the reflective surface is arranged on the reflected outgoing light path of the third beam splitter 28; the first detector 23 and the second detector 26 sense the posture change of the stylus 19 and / or the change of the incident light intensity of the light transmission port 25 based on the change of the light intensity and / or the change of the light position of the received detection light.

[0087] In one embodiment, the second detector 26 is used to monitor the change of the intensity of the incident light at the light transmission port 25, and maintain the intensity of the incident light in a stable range through servo control.

[0088] In this embodiment, in order to ensure the accuracy of measurement, the stylus 19 needs to make an up-and-down movement only perpendicular to the optical axis of the first collimating lens 32 or coincident with the optical axis of the first collimating lens 32. During the detection process, the stylus 19 will produce a movement inclined to the direction of the optical axis of the first collimating lens 32 due to external interference. In this embodiment, the first detector 23 is a four-quadrant position detector for sensing the change of the light spot position; the second detector 26 is used to detect the light intensity. First, the results detected by the first detector 23 and the second detector 26 of the stylus 19 under the ideal position condition are recorded and recorded. When the posture of the stylus 19 changes, the change of the posture of the stylus 19 can be obtained by comparing and calculating the change between the detection light received by the two detectors with the above results.

[0089] In one embodiment, the contact pin 19 is a T-shaped contact pin 19 with a flat reflective surface on the top and a probe on the bottom.

[0090] In one embodiment, the plane reflective surface is perpendicular to the axis of the probe and is disposed on the outgoing optical path of the reflected light of the third beam splitter 28 .

[0091] In one embodiment, the planar reflecting surface is parallel to the optical axis of the second focusing lens 37 .

[0092] In one embodiment, the interferometric measurement system further includes an actuator; the actuator adjusts the contact measurement head based on the posture sensing optical path so that the central axis of the probe is parallel to or coincides with the optical axis of the first collimating lens 32 .

[0093] The first detector 23 is a four-quadrant position detector.

[0094] like Figure 3 , 4 As shown, the first collimating lens 32, the first beam splitter 33, the third beam splitter 28, the stylus 19 support module and the stylus 19 of this embodiment are all installed in the first lens barrel 20; the reflector 30 of this embodiment is installed in the second lens barrel 21; the second collimating lens 35, the second beam splitter 36, the first detector 23, the first focusing lens 34 and the second focusing lens 37 are installed in the third lens barrel 24.

[0095] In one embodiment, Figure 1 , 2 As shown, the motion assembly includes a first mechanical arm 7, a second mechanical arm 10, a first rotating part and a second rotating part;

[0096] The measuring head 11 is mounted on the first rotating part, and the first rotating part drives the measuring head 11 to rotate along the first rotating shaft 9;

[0097] The first mechanical arm 7 drives the rotating part to perform a transverse axis movement, and the second mechanical arm 10 drives the rotating part to perform a longitudinal axis movement perpendicular to the transverse axis movement;

[0098] The object to be measured is mounted on the second rotating part, and the second rotating part drives the object to be measured 12 to rotate along the second rotating axis.

[0099] In such Figure 1In the embodiment shown, the principle of the contact-assisted positioning multi-wavelength laser interferometry measurement system is: the multi-wavelength (≥2 wavelengths) monochromatic light emitted by the light source 14 (the light source module includes a plurality of monochromatic lights, and within the visible light or infrared light wavelength range, the monochromatic lights of different wavelengths can be freely combined and output through the control system) is transmitted to the measuring head 11 and the first reference measuring head 2, the second reference measuring head 6, and the third reference measuring head 8 via the signal line 16 (the signal line includes optical fibers and wires that can transmit optical signals and electrical signals, and the schematic diagram is simplified). When the reference measuring head is a contact measuring head, only one set of monochromatic light is used, and a part of the monochromatic light is incident. The light is reflected back through the reference surface (reference surface: that is, the mirror surface (with very small roughness), which can be approximately regarded as an ideal surface and will not introduce significant measurement errors) in the measuring head and serves as the reference light. Another part of the incident light is reflected back through the object to be measured 12 or the first reference surface 3, the stylus 19, and the second reference surface 5 and serves as the measuring light. The reference light and the measuring light interfere with each other after they meet, and the interference signal is transmitted to the detector module 15 through the signal line 16. The collected signal is initially processed by the control system and then transmitted to the calculation module 17. Further processing is completed in the calculation module 17 to obtain the deviation data of the three-dimensional morphology of the object to be measured 12, and the data is displayed.

[0100] Measuring head 11: used to measure the three-dimensional shape of the object 12 to be measured;

[0101] The first reference measuring head 2, the second reference measuring head 6, and the third reference measuring head 8 are used to measure the displacement distance of the mechanical axis and accurately locate the position of the measuring head 11 or the object 12 to be measured in space. The measured data can be used to compensate for the error introduced when the mechanical axis moves.

[0102] The first reference measuring head 2 is used to compensate for the mechanical error generated when the second robot arm 10 (capable of horizontal reciprocating motion) moves horizontally.

[0103] The second reference measuring head 6 is used to compensate for the mechanical error of the first mechanical arm 7 (which can perform vertical reciprocating motion) during vertical movement.

[0104] The third reference measuring head 8 is used to compensate for the mechanical error generated when the first rotating shaft 9 (which can perform rotational motion) rotates.

[0105] Error compensation: 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, optical means are required to accurately locate the spatial position of the object), and subtracts or adds this value to the measurement data of the measuring head 11 (or performs other calculations).

[0106] Among them, the third reference surface 4 and the measuring head 11 are fixed on the first mechanical arm 7 and rotate around the first rotating shaft 9 to realize the three-dimensional surface scanning measurement of the object to be measured 12. The first rotating shaft 9 will generate mechanical disturbance during rotation, thereby generating measurement error. In order to compensate for the error, a contact-type auxiliary positioning third reference measuring head 8 is used to compensate for the error. The stylus 19 of the third reference measuring head 8 contacts the third reference surface 4. When the third reference surface 4 vibrates mechanically during rotation, the stylus 19 will capture the vibration displacement. The captured vibration signal will be further processed and can be used to compensate for the vibration error introduced when the first rotating shaft 9 rotates.

[0107] The principle of contact-assisted positioning of the third reference measuring head 8 is as follows: Figure 3 , 4 As shown, Figure 3 is the outline of the stylus reference measuring head, Figure 4 The internal structure diagram is shown in FIG. 1 . The monochromatic light emitted by the light source 14 is transmitted to the first light transmission port 22 via the signal line 16. The incident light 29 is converted into parallel light by the first collimating lens 32 and then split by the first beam splitter 33. A part of the light is reflected and irradiated to the reflector 30 and then returned. The reflected light 31 is used as the reference light. A part of the light is transmitted and irradiated to the third beam splitter 28. After transmission, it further irradiates the top of the stylus 19. The stylus 19 is T-shaped, and the top has a high reflectivity for the incident light. After being reflected by the stylus 19, the reflected light is used as the measuring light. The measuring light and the reflected light 31 are the same. Encounter emission interference, because the stylus 19 can move up and down, when the third reference plane 4 moves up and down (when the third reference plane 4 rotates around the first rotation axis 9, mechanical disturbance will appear, and this disturbance is directly related to the measurement accuracy of the measuring head 11 and needs to be compensated), the stylus 19 also moves up and down, resulting in a change in the optical path difference between the measuring light and the reflected light 31, and then by analyzing the interference signal, the slight displacement of the third reference plane 4 can be obtained, and the vibration of the measuring head 11 can be further determined. After compensating for the vibration error, the precise position of the measuring head 11 can be obtained.

[0108] In addition, in order to accurately measure the three-dimensional morphology of the object 12 to be measured, the measuring head 11 needs to rotate around the first rotating shaft 9, and the optical axis of the measuring head 11 must always be parallel to or coincide with the normal of the surface shape of the object 12 at different positions to be measured. In order to improve the measurement accuracy, the axis of the stylus 19 is required to be always in the vertical direction. However, in the actual measurement process, the stylus 19 may be deflected by the friction of the rotation of the third reference surface 4, resulting in a measurement error of the stylus 19. In order to compensate for the error, it is necessary to compensate through servo adjustment, that is, when the stylus 19 deflects, the system can monitor the deflection angle and then feed it back to the actuator of the third reference measuring head 8, which will drive the third reference measuring head 8 to move in the horizontal direction. When the axis of the stylus 19 is in the vertical direction, the actuator stops moving. Through the servo mechanism, the stylus 19 can accurately measure the vertical displacement of the third reference surface 4 during rotation, and then calculate the displacement of the measuring head 11 along the axial direction through a functional relationship, so that the axial error of the measuring head 11 during rotation can be compensated in real time. The specific principle is as follows: the monochromatic light emitted by the light source 14 is transmitted to the second light transmission port through the signal line 16, and then enters the second beam splitter 36 after being collimated by the second collimating lens 35. A part of the light is reflected and detected by the second detector 26. This signal is called the reference signal. By detecting the size of the signal, the size of the incident light intensity can be monitored in real time, and then fed back to the light source controller for regulation, so that the incident light intensity is always stable in a steady-state range. Another part of the light is transmitted and irradiated onto the third beam splitter 28, and then irradiated onto the top of the stylus 19 after reflection. If the third reference surface 4 is an arc surface, theoretically, the stylus 19 will always maintain a vertical posture. When the measuring head 11 rotates, the stylus 19 may rotate slightly due to the friction force, causing the top of the stylus 19 to tilt. The light reflected from the top of the stylus 19 is reflected by the third beam splitter 28, and further reflected by the second beam splitter 36. After passing through the first focusing lens 34, it is irradiated onto the first detector 23. The first detector 23 is a four-quadrant position detector. When the stylus 19 rotates, the light spot irradiates The position where the light hits the first detector 23 will change. There is a direct relationship between the change in the position of the light spot and the change in the angle. By calculating the position of the light spot on the first detector 23, the angle value can be obtained, so that the rotation angle of the stylus 19 can be monitored in real time, and then fed back to the actuator of the third reference measuring head 8. The actuator acts (i.e., drives the third reference measuring head 8 to move in the direction of the deflection of the stylus 19, so that the axis of the third reference measuring head 8 coincides with the axis of the stylus 19), so that the axis of the third reference measuring head 8 always coincides with the axis of the stylus 19, thereby eliminating the measurement deviation caused by the rotation of the stylus 19.

[0109] In order to measure the three-dimensional shape of the object 12 to be measured, since the measuring head 11 needs to move in a large range in the horizontal and vertical directions, the first mechanical arm 7 (vertical movement) and the second mechanical arm 10 (horizontal movement) will introduce positioning errors during the movement. In order to compensate for the errors, two reference measuring heads are used, namely the first reference measuring head 2 and the second reference measuring head 6. The first reference surface 3 is fixed on the second mechanical arm 10, and the second reference surface 5 is fixed on the first mechanical arm 7. The first reference measuring head 2 and the second reference measuring head 6 can measure the horizontal and vertical movement distances of the measuring head 11 in real time, so as to accurately assist in locating the position of the measuring head 11 in space. The first reference measuring head 2, the second reference measuring head 6 and the measuring head 11 can adopt a non-contact measuring head structure, such as Figure 5 As shown, the measuring head 11 can adopt a focusing measuring head. The multi-wavelength monochromatic light emitted by the light source 14 is transmitted to the optical fiber 40 through the signal line 16. A part of the incident light 41 is reflected by the optical fiber end face 43 and used as the reference light. A part of the transmitted light is focused by the third focusing lens 38 and irradiated on the measured object 12. After being reflected by the measured object, it is used as the measuring light. The reference light and the measuring light meet and interfere. The PZT module 39 drives the optical fiber 40 to reciprocate, so that the optical path difference between the reference light and the measuring light changes, thereby realizing phase shift measurement. After the interference signal is subsequently processed and analyzed, the three-dimensional morphology information of the measured object 12 is inverted. In addition, as Figure 6 As shown, for the first reference measuring head 2 and the second reference measuring head 6, a collimating measuring head may be used, and a third collimating lens 44 may be used to collimate the light.

[0110] In such Figure 2 In the illustrated embodiment, the first reference measuring head 2 and the second reference measuring head 6 are installed on the measuring platform. At this time, the measuring head 11 only needs to rotate around the first rotating axis 9 in space, and the second rotating axis 13 drives the measured object 12 to rotate, thereby realizing the measurement of the entire surface topography. The translation stage 18 can drive the measured object 12 to move in the horizontal and vertical directions, and the first reference measuring head 2 and the second reference measuring head 6 are used to compensate for the vertical and horizontal mechanical movement errors respectively. The first reference surface 3 and the second reference surface 5 are fixed, and the first reference measuring head 2 and the second reference measuring head 6 can move with the translation stage 18.

[0111] 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 contact-assisted positioning laser interferometry system, characterized in that: include: Light source, measuring head, motion components and reference system components; The light source is used to generate monochromatic light; The reference system assembly 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 motion component drives the measuring head and / or the object to be measured to move so that the measured area of ​​the object to be measured is within the detection range of the measuring head; At least one of the measuring head and the reference measuring head is a contact measuring head; The contact measuring head receives the monochromatic light reflected by the stylus based on the monochromatic light irradiating the stylus, so that the monochromatic light reflected by the stylus interferes with a part of the monochromatic light incident into the contact measuring head; During measurement, the end of the stylus contacts the reference surface or the object to be measured, and the stylus moves up and down along with the surface shape of the reference surface or the object to be measured; 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; The contact type measuring head comprises: A first light transmission port, connected to the light source and the computing module; A first collimating lens is arranged on the outgoing light path of the first light transmission port, and the optical axis is coaxial with the first light transmission port; A first beam splitter is arranged on the outgoing light path of the first collimating lens, and the angle between the reflecting surface and the optical axis of the first collimating lens is 45°; a reflector, arranged on an outgoing optical path of the monochromatic light reflected from the first collimating lens by the first beam splitter, and arranged parallel to the optical axis of the first collimating lens; The contact pin is arranged on the optical path of the transmitted light of the first beam splitter.

2. The interferometric measurement system according to claim 1, characterized in that The parallel light transmitted by the beam splitter reaches the stylus and is reflected by the stylus to reach the first light transmission port, and the monochromatic light forms the measuring light; the parallel light reflected by the reflector to the first beam splitter and reaches the first light transmission port forms the reference light; The measuring light and the reference light interfere with each other to form the interference fringes.

3. The interferometric measurement system according to claim 1, characterized in that: The contact type measuring head further comprises a posture sensing optical path; the posture sensing optical path senses the posture of the stylus.

4. The interferometric measurement system according to claim 3, characterized in that: The posture sensing optical path includes: A second light transmission port, used for emitting detection light; A second collimating lens is arranged on the outgoing light path of the second light transmission port, and the optical axis is coaxial with the second light transmission port; A second beam splitter is arranged on the outgoing light path of the second collimating lens, and the angle between the reflecting surface and the optical axis of the second collimating lens is 45°; A first focusing lens is arranged on an outgoing light path of the detection light reflected from the second beam splitter by the second beam splitter; A first detector is arranged on the outgoing light path of the first focusing lens; A third beam splitter is arranged on the transmission output light path of the second beam splitter; the angle between the reflective surface and the optical axis of the first collimating lens is 45°; A second focusing lens is arranged on an outgoing light path of the detection light reflected by the second beam splitter from the second collimating lens; A third detector is arranged on the outgoing light path of the second focusing lens; Wherein: the reflective surface is arranged on the reflected outgoing light path of the third beam splitter; the first detector and the second detector sense the posture change of the stylus based on the change of the light intensity and / or the change of the light position of the received detection light.

5. The interferometric measurement system according to claim 4, characterized in that: The stylus is a T-shaped stylus, the top of which is a plane reflective surface, and the bottom of which is a probe; the plane reflective surface is perpendicular to the axis of the probe.

6. The interferometric measurement system according to claim 5, characterized in that: The plane reflecting surface is parallel to the optical axis of the second focusing lens and is arranged on the outgoing optical path of the reflected light of the third beam splitter.

7. The interferometric measurement system according to claim 5, characterized in that: The interferometric measurement system further includes an actuator; the actuator adjusts the contact measurement head based on the sensing result of the posture sensing optical path so that the central axis of the probe is parallel to or coincides with the optical axis of the first collimating lens.

8. The interferometric measurement system according to claim 4, characterized in that: The first detector is a four-quadrant position detector used to sense changes in the light spot position; the second detector is used to detect light intensity.

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