Method and system for automatic alignment of optical path of laser interferometer

Abstract

The application relates to the optical technical field, in particular to a light path automatic alignment method and system of a laser interferometer. The method comprises the following steps: S1: a light source generates a double-frequency light beam, and the double-frequency light beam is incident to a light beam adjusting module; S2: the light beam adjusting module receives the double-frequency light beam and transmits the double-frequency light beam to an interference mirror group, the light beam adjusting module comprises m light beam adjusting units, m is an integer greater than or equal to 1; the light beam adjusting unit comprises an optical element, a first adjusting element and a second adjusting element; S3: the interference mirror group makes the double-frequency light beam form reference light and measurement light respectively, and transmits the reference light and the measurement light to a signal conversion module; S4: the signal conversion module converts the reference light and the measurement light into an optical interference fringe electrical signal; S5: an interference contrast generation device receives the optical interference fringe electrical signal and generates an interference contrast value; and S6: a control module executes a scanning alignment process. In this way, the automatic high-precision alignment of the light path can be realized.

Description

Technical Field

[0001] This application relates to the field of optical technology, and in particular to an automatic optical path alignment method and system for a laser interferometer. Background Technology

[0002] In the field of semiconductor precision equipment, laser interferometers are widely used for three-dimensional attitude calibration and real-time control of precision mechanical components. They can also be used to achieve precise measurement of key parameters such as material surface shape detection, air refractive index measurement, and precision displacement monitoring. The working principle of a laser interferometer is based on the optical interference effect. By establishing the correspondence between the measured physical quantity and the interference phase, the interference phase signal is obtained. Then, by analyzing the interference phase signal, the required information about the measured physical quantity can be obtained.

[0003] However, several challenges are typically encountered in the engineering practice of laser interferometers: First, to achieve optimal measurement accuracy and range, precise alignment of the optical path is required during assembly and adjustment. Second, even after initial adjustment, the optical path may gradually deviate from its optimal alignment after a period of operation due to factors such as ambient temperature fluctuations, air pressure changes, or structural stress creep, thus affecting the normal operation and measurement reliability of the equipment. Third, while traditional methods relying on manual adjustment can achieve alignment accuracy to some extent, they are time-consuming and labor-intensive, especially in complex equipment or vacuum environments where manual maintenance is difficult. Summary of the Invention

[0004] This application provides an automatic optical path alignment method and system for a laser interferometer. This method uses the optical interference contrast signal as a feedback signal to achieve automatic alignment of the laser interferometer, thereby improving the automatic alignment accuracy of the optical path, reducing maintenance costs, and enhancing the environmental adaptability of the alignment process, thus solving the aforementioned pain points in the installation and commissioning of laser interferometers.

[0005] In a first aspect, embodiments of this application provide an automatic optical path alignment method for a laser interferometer. This method is applied to an automatic optical path alignment system, which includes a light source, a beam adjustment module, an interferometer mirror group, a signal conversion module, an interference contrast generation device, and a control module. The method includes:

[0006] S1: The light source generates a dual-frequency beam and incident the dual-frequency beam onto the beam adjustment module. The dual-frequency beam includes a first frequency light and a second frequency light.

[0007] S2: The beam adjustment module receives the dual-frequency beam and sends the dual-frequency beam to the interferometer group. The beam adjustment module includes m beam adjustment units, where m is an integer greater than or equal to 1. Each beam adjustment unit includes an optical element, a first adjustment element, and a second adjustment element. The parameter values ​​of the first adjustment element and the second adjustment element are used to determine the positions of the dual-frequency beam in the first direction and the second direction after passing through the optical element, respectively. The first direction is perpendicular to the second direction.

[0008] S3: The interferometer group enables the first frequency light and the second frequency light to form the reference light and the measurement light respectively, and sends the reference light and the measurement light to the signal conversion module.

[0009] S4: The signal conversion module converts the reference light and the measurement light into electrical signals of optical interference fringes.

[0010] S5: The interference contrast generation device receives the electrical signal of the optical interference fringes and generates the interference contrast value of the reference light and the measurement light.

[0011] S6: The control module executes the scanning alignment process; the scanning alignment process includes m unit scanning alignment processes executed separately, the kth unit scanning alignment process corresponds to the kth beam adjustment unit, k=1, 2, ..., m.

[0012] The scanning alignment process for the kth unit includes: fixing the parameter value of the second adjustment element of the kth beam adjustment unit and the parameter values ​​of the remaining beam adjustment units; adjusting the parameter value of the first adjustment element of the kth beam adjustment unit; and acquiring the interference contrast value generated by the interference contrast generation device in real time to form a first interference contrast value group; and resetting the parameter value of the first adjustment element of the kth beam adjustment unit to the parameter value of the first adjustment element of the kth beam adjustment unit corresponding to the maximum interference contrast value in the first interference contrast value group; fixing the parameter value of the first adjustment element of the kth beam adjustment unit and the parameter values ​​of the remaining beam adjustment units; adjusting the parameter value of the second adjustment element of the kth beam adjustment unit; and acquiring the interference contrast value generated by the interference contrast generation device in real time to form a second interference contrast value group; and resetting the parameter value of the second adjustment element of the kth beam adjustment unit to the parameter value of the second adjustment element of the kth beam adjustment unit corresponding to the maximum interference contrast value in the second interference contrast value group.

[0013] Thus, this method can improve the assembly and adjustment efficiency of laser interferometers, automatically maintain the alignment accuracy of laser interferometers during use, and ensure the long-term stability of laser interferometers. In addition, this method can also overcome the limitations of maintenance operations caused by limited maintenance space and vacuum environment, thereby realizing automatic optical path alignment of laser interferometers.

[0014] It should be noted that before the interference contrast generation device generates the interference contrast value, an initial state confirmation step of the optical path can be included. Specifically, the interference contrast generation device needs to be able to detect a valid interference signal, meaning that the reference light and the measurement light need to overlap spatially, so that the interference contrast value is typically between 0 and 1, for example, 0.2, 0.5, or 1, etc. This indicates that the optical path is in an initial state where automatic alignment adjustment can be performed, allowing subsequent scanning alignment procedures to continue. If the interference contrast value is not within the range of 0 to 1 or no valid interference signal is detected, it indicates that the reference light and the measurement light may be completely separated, requiring manual or other methods to perform rough alignment first, so that the two beams spatially overlap.

[0015] Additionally, it should be noted that in the embodiments of this application, fixing the parameter values ​​of one or more adjustment elements can mean keeping the current parameter value of the adjustment element unchanged, or locking it in its current state so that it does not change with the adjustment actions of other adjustment elements. This will not be repeated below. Furthermore, in the above-mentioned k-th unit scanning alignment process, the remaining beam adjustment units refer to other beam adjustment units besides the k-th beam adjustment unit.

[0016] Furthermore, it should be noted that in the embodiments of this application, resetting the parameter value to the parameter value of the adjustment element corresponding to the maximum interference contrast value in the corresponding interference contrast value group means adjusting or restoring the current parameter value of the adjustment element to the parameter value corresponding to the maximum interference contrast value recorded in the interference contrast value group, so that the beam adjustment unit is in the optimal optical path alignment position under this operation, which will not be repeated below.

[0017] It is understood that in S6 above, all the adjustment elements can be scanned one by one. For example, when scanning each adjustment element, the interference contrast value corresponding to each scanning position of the adjustment element can be recorded simultaneously, and the adjustment element can be reset to the position corresponding to the maximum interference contrast value after the scan is completed. Then, the next adjustment element can be scanned until all adjustment elements have been scanned and reset.

[0018] In one possible implementation of the first aspect, if m is greater than or equal to 2, the following steps are also included:

[0019] S7: The control module obtains the interference contrast value generated by the interference contrast generating device in real time. If the interference contrast value is greater than or equal to the first preset threshold, it is determined that the optical path is automatically aligned. Otherwise, S8 is executed.

[0020] S8: The control module executes the joint alignment process and ends the automatic optical path alignment. The joint alignment process includes executing the first direction alignment process and the second direction alignment process on the preset beam adjustment unit group respectively. The preset beam adjustment unit group includes at least two beam adjustment units.

[0021] The first direction alignment process includes: with the parameter values ​​of each second adjustment element of the preset beam adjustment unit group and the parameter values ​​of the remaining beam adjustment units in the beam adjustment module fixed, the parameter values ​​of each first adjustment element of the preset beam adjustment unit group are combined and adjusted to obtain the interference contrast value generated by the interference contrast generation device in real time to form a third interference contrast value group, and the parameter values ​​of each first adjustment element of the preset beam adjustment unit group are reset to the parameter values ​​of each first adjustment element of the preset beam adjustment unit group corresponding to the maximum interference contrast value in the third interference contrast value group, and then proceeding to the second direction alignment process.

[0022] The second direction alignment process includes: with the parameter values ​​of each first adjustment element in the preset beam adjustment unit group and the parameter values ​​of the remaining beam adjustment units in the beam adjustment module fixed, the parameter values ​​of each second adjustment element in the preset beam adjustment unit group are combined and adjusted to obtain the interference contrast value generated by the interference contrast generation device in real time to form a fourth interference contrast value group, and the parameter values ​​of each second adjustment element in the preset beam adjustment unit group are reset to the parameter values ​​of each second adjustment element in the preset beam adjustment unit group corresponding to the maximum interference contrast value in the fourth interference contrast value group.

[0023] In some embodiments of this application, the first preset threshold can be set to any suitable value according to the system noise level and accuracy requirements. It can be set arbitrarily, for example, to 80% to 98% of the theoretical maximum value of the interference contrast (i.e., 1). For example, the first preset threshold can be 0.8, 0.85, 0.9, 0.95, or 0.98, etc.

[0024] It is understood that in step S8 above, the control module 50 can use a joint adjustment alignment (or combined scanning) process to coordinately adjust the preset beam adjustment unit group. Specifically, the first adjustment element of each beam adjustment unit in the preset beam adjustment unit group can be synchronously adjusted first, and then the second adjustment element of each beam adjustment unit in the preset beam adjustment unit group can be synchronously adjusted to ensure that the interference contrast value after each round of combined adjustment continuously increases or remains constant. This completes the joint adjustment alignment process of the entire optical path.

[0025] In the first direction alignment process, the third interference contrast value group can refer to a set of data formed by a series of interference contrast values ​​acquired in real time during the process of the control module combining and adjusting the parameter values ​​of the first adjustment elements of the preset beam adjustment unit group (e.g., alternating fine adjustment, synchronous fine adjustment, or adjustment according to a specific sequence) while fixing the parameter values ​​of each second adjustment element of the preset beam adjustment unit group and the remaining beam adjustment units.

[0026] Similarly, in the second direction alignment process, the fourth interference contrast value group can refer to: a set of data formed by a series of interference contrast values ​​acquired in real time during the process of adjusting the parameter values ​​of the second adjustment elements of the preset beam adjustment unit group in a similar combination, while fixing the parameter values ​​of the first adjustment elements of the preset beam adjustment unit group and the parameter values ​​of the other beam adjustment units.

[0027] Since there are peak values ​​(such as maximum values ​​or local optimum values) in both the third and fourth interference contrast value groups, the optimal parameter combination of each adjustment element in the preset beam adjustment unit group corresponding to the peak value can be locked. This allows the preset beam adjustment unit group to be reset to the optimal cooperative posture in that direction, thereby improving the spatial overlap of the dual-frequency beams and further improving the interference contrast value.

[0028] As described above, by combining scanning alignment with joint alignment, a progressive alignment process can be implemented, which can further eliminate coupling errors or residual deviations between multiple beam adjustment units on the basis of the initial alignment of a single beam adjustment unit, thereby achieving global optimization alignment of the optical path and improving the final interference contrast and system alignment accuracy.

[0029] In one possible implementation of the first aspect, the preset beam adjustment unit group includes the two beam adjustment units closest to the interference contrast generating device; each beam adjustment unit in the preset beam adjustment unit group includes: a first adjustment element and a second adjustment element.

[0030] Thus, by coordinating the two beam adjustment units closest to the interference contrast generation device, residual angular deviations and positional offsets in the optical path can be further corrected on the basis of initial alignment by single-axis scanning, achieving local fine calibration of the beam direction. At the same time, since only two beam adjustment units at key positions are selected for combined optimization, the problem of low efficiency that may occur when coordinating more units can be avoided, thereby improving adjustment efficiency and accuracy.

[0031] In one possible implementation of the first aspect, in the nth beam adjustment unit, the current parameter value and parameter value step size of the first adjustment element are respectively and n=1, 2, ..., m; the first direction alignment process further includes:

[0032] S811: The control module executes the first joint regulation factor identification process.

[0033] The first coordination factor identification process includes: recording the current parameter values ​​of the two first adjustment elements of the preset beam adjustment unit group. and and the current interference contrast value generated by the interference contrast generation device. ; and set the parameter value step size of the two first adjustment elements of the preset beam adjustment unit group respectively. With the parameter values ​​of each second adjustment element in the preset beam adjustment unit group and the parameter values ​​of the remaining beam adjustment units in the beam adjustment module fixed, the parameter values ​​of the two first adjustment elements in the preset beam adjustment unit group are respectively adjusted to ( ),in,( , The first coordination factor is defined as (+1,+1), which includes the following combinations: (+1,-1), (+1,-1), (-1,+1), and (-1,-1). The interference contrast values ​​generated by the interference contrast generation device corresponding to each combination of the first coordination factor are acquired in real time. , , and ,in, , , , and Form the fifth set of interference contrast values; if the maximum value in the fifth set of interference contrast values... Then The corresponding first coordination factor is used as the first target coordination factor. ), then proceed to S812; if The parameter values ​​of the two first adjustment elements of the preset beam adjustment unit group are reset to ( , ), thus ending the first direction alignment process.

[0034] S812: The control module executes the first optimization process.

[0035] The first optimization process includes: adjusting the parameter values ​​of the two first adjustment elements of the preset beam adjustment unit group to ( ),in, The number of steps, and in During the process of incrementing by 1 sequentially, each step is acquired and recorded in real time. The parameter value combination corresponds to the interference contrast value generated by the interference contrast generation device. This is done to form the sixth interference contrast value group, and to reset the parameter values ​​of each first adjustment element in the preset beam adjustment unit group to the maximum interference contrast value in the sixth interference contrast value group. The parameter values ​​of each first adjustment element in the corresponding preset beam adjustment unit group;

[0036] S813: Switch to the second direction alignment process.

[0037] It is understandable that this first coordination factor identification process can quickly identify the optimal coordinated adjustment direction that increases the interference contrast value. Specifically, through the preceding parameter values... and By selecting four representative directions (i.e., the four combinations of the first tuning factor) around the target and making tentative adjustments, and comparing the interference contrast response in each direction, it is possible to effectively determine whether there is a region with a better parameter combination. In this way, invalid fine scanning in directions with no obvious gain can be avoided. If the interference contrast values ​​in all four directions do not exceed the current value, it indicates that the current position may have reached a local optimum, and therefore the adjustment in that direction can be terminated.

[0038] It should be noted that, in At this point, the first direction alignment process ends, and the fifth interference contrast value group obtained in S811 becomes the third interference contrast value group obtained above.

[0039] The fifth set of interference contrast values ​​refers to the data set formed by the control module recording the interference contrast values ​​of the two first adjustment elements of the preset beam adjustment unit group at their current parameter values ​​during the first coordination factor identification process, and the real-time acquisition of interference contrast values ​​when the parameter value combination is adjusted to the corresponding position according to the four combinations of the first coordination factor. Therefore, the maximum value in the fifth set of interference contrast values ​​can be used as the basis for determining the optimal coordinated adjustment direction.

[0040] Thus, by introducing a joint adjustment factor for directional prediction, the correct adjustment direction can be quickly screened in the early stages of combined adjustment, thereby improving the efficiency of the joint adjustment alignment process.

[0041] The sixth interference contrast value group can refer to the asynchronous values ​​recorded synchronously when the control module gradually changes the parameter values ​​of the two first adjustment elements of the preset beam adjustment unit group at a preset step size during the continuous stepping process along the direction indicated by the first target modulation factor. The data set formed by the corresponding interference contrast values. Therefore, the peak value in this sixth interference contrast value set can be used as the basis for determining the optimal parameter combination in the first direction.

[0042] It should be noted that, in At this time, the sixth interference contrast value group obtained in S812 is used as the third interference contrast value group obtained above.

[0043] It can be understood that the first optimization process is a continuous adjustment process along this direction, based on the first joint adjustment factor identification process. Specifically, by increasing the number of steps... Starting from 1 and increasing sequentially, the parameter value combination of the two first adjustment elements can be continuously changed along the direction indicated by the first target adjustment factor, and the changing trend of the interference contrast value can be monitored in real time to form a sixth interference contrast value group that reflects the distribution characteristics of interference contrast in that direction.

[0044] Thus, by performing a continuous stepping process along the optimal direction after identification, the optimal parameter combination in the first direction can be precisely locked, avoiding problems such as insufficient accuracy due to excessive step size or insufficient sampling points. Simultaneously, this process dynamically determines the optimal position by recording changes in interference contrast values ​​in real time to prevent over-adjustment. Furthermore, by using the optimized state in the first direction as the initial condition for optimization in the second direction, decoupling and sequential optimization of the two adjustment directions can be achieved, reducing the complexity of simultaneous adjustment of multiple variables and improving the efficiency and accuracy of optical path alignment.

[0045] In one possible implementation of the first aspect, in step S812, the maximum value of the interference contrast value in the sixth interference contrast value group is obtained. The method is: when At that time, Steps No more additions will be made.

[0046] This criterion can be used to identify local maxima (i.e., peak points) in the sixth set of interference contrast values. Specifically, when the... The interference contrast value of the first step is less than that of the second step. The value of the step, and the first The value of the step is greater than the first step. When the value of the step is given, it indicates the number of steps. The current step position represents the optimal point along that step direction; continuing to adjust along this direction will cause a decrease in the interference contrast value. Therefore, the process can be stopped promptly when a peak feature is detected, thereby improving optical path alignment efficiency and avoiding unnecessary resource waste.

[0047] Thus, by introducing this peak detection step, timely termination can be achieved in the first optimization process to quickly lock in the optimal parameter combination, thereby improving the convergence speed and adjustment efficiency of optical path alignment. Simultaneously, this step can effectively prevent over-driving of the adjustment elements or excessive swaying of the mechanical structure, extending the lifespan of the beam adjustment unit. Furthermore, by using this peak point as a reset reference, it can be ensured that the two first adjustment elements are precisely reset to the optimal cooperative posture in this direction, thereby achieving local optimization of interference contrast in the first direction.

[0048] In one possible implementation of the first aspect, in the nth beam adjustment unit, the current parameter value and parameter value step size of the second adjustment element are respectively and The second-direction alignment process further includes:

[0049] S821: The control module executes the second joint regulation factor identification process.

[0050] The second coordination factor identification process includes: recording the current parameter values ​​of the two second adjustment elements of the preset beam adjustment unit group. and and the current interference contrast value generated by the interference contrast generation device. ; and set the parameter value step size of the two second adjustment elements of the preset beam adjustment unit group respectively. With the parameter values ​​of each first adjustment element in the preset beam adjustment unit group and the parameter values ​​of the remaining beam adjustment units in the beam adjustment module fixed, the parameter values ​​of the two second adjustment elements in the preset beam adjustment unit group are adjusted to ( ),in,( The second coordination factor is defined as (+1,+1), which includes the following combinations: (+1,-1), (+1,-1), (-1,+1), and (-1,-1). The interference contrast values ​​generated by the interference contrast generator corresponding to each combination of the second coordination factor are acquired in real time. , , and ,in, , , , and Form the seventh set of interference contrast values; if the maximum value in the seventh set of interference contrast values... Then The corresponding second coordination factor is used as the second objective coordination factor. , ), then proceed to S822; if Reset the parameter values ​​of the two second adjustment elements of the preset beam adjustment unit group to ( , ), thus ending the second-direction alignment process.

[0051] S822: The control module executes the second optimization process.

[0052] The second optimization process includes: adjusting the parameter values ​​of the two second adjustment elements of the preset beam adjustment unit to ( ),in, The number of steps, and in During the process of incrementing by 1 sequentially, each step is acquired and recorded in real time. The interference contrast generated by the interference contrast generation device corresponds to the combination of parameter values. This forms the eighth interference contrast value group, and resets the parameter values ​​of each second adjustment element in the preset beam adjustment unit group to the maximum interference contrast value in the eighth interference contrast value group. The parameter values ​​of each second adjustment element in the corresponding preset beam adjustment unit group.

[0053] It should be noted that, in At this point, the second direction alignment process ends, and the seventh interference contrast value group obtained in S821 is used as the fourth interference contrast value group obtained above.

[0054] The seventh set of interference contrast values ​​can be described with reference to the description of the fifth set of interference contrast values, and will not be repeated here.

[0055] Similarly to step S811 above, by introducing a joint adjustment factor for directional prediction, the correct adjustment direction can be quickly screened in the early stage of combined adjustment, thereby improving the efficiency of the joint adjustment alignment process.

[0056] The eighth interference contrast value group can be referred to the description of the sixth interference contrast value group above, and will not be repeated here.

[0057] It should be noted that, in At this time, the eighth interference contrast value group obtained in S822 is used as the fourth interference contrast value group obtained above.

[0058] Thus, by continuously stepping along the optimal direction after identification, the optimal parameter combination in the second direction can be precisely locked, avoiding problems such as insufficient accuracy due to excessive step size or insufficient sampling points. Simultaneously, this process dynamically determines the optimal position by recording changes in interference contrast values ​​in real time to prevent over-adjustment.

[0059] In one possible implementation of the first aspect, in step S822, the maximum value of the interference contrast in the eighth interference contrast value group is obtained. The method is: when At that time, Steps No more additions will be made.

[0060] This criterion can be used to identify local maxima (i.e., peak points) in the sixth set of interference contrast values. Specifically, when the... The interference contrast value of the first step is less than that of the second step. The value of the step, and the first The value of the step is greater than the first step. When the value of the step is given, it indicates the number of steps. The current step position represents the optimal point along that step direction; continuing to adjust along this direction will cause a decrease in the interference contrast value. Therefore, the process can be stopped promptly when a peak feature is detected, thereby improving optical path alignment efficiency and avoiding unnecessary resource waste.

[0061] Thus, by introducing this peak detection step, timely termination can be achieved in the second optimization process to quickly lock in the optimal parameter combination, thereby improving the convergence speed and adjustment efficiency of optical path alignment. Simultaneously, this step effectively prevents over-driving of the adjustment elements or excessive swaying of the mechanical structure, extending the lifespan of the beam adjustment unit. Furthermore, by using this peak point as a reset reference, it can be ensured that the two second adjustment elements are precisely reset to their optimal cooperative posture in this direction, thereby achieving local optimization of interference contrast in the second direction.

[0062] In one possible implementation of the first aspect, the polarization directions of the first frequency light and the second frequency light are orthogonal; the interference contrast value is positively correlated with the spatial overlap between the reference light and the measurement light; wherein, the formula for calculating the interference contrast value is: ,in, The maximum value of the electrical signal in the optical interference fringes. This represents the minimum value of the electrical signal in the optical interference fringes.

[0063] Since the frequency difference of the dual-frequency beam is fixed, its maximum value is taken in each period of the cosine function. minimum value Through formula The interference contrast value can be obtained by , where V is the abbreviation for Visibility.

[0064] In this way, by converting the spatial overlap of the dual-frequency beams into a quantifiable interference contrast value, the control module can monitor and control the optical path alignment status in real time, and provide feedback for the adjustment or reset of the adjustment elements in the subsequent scanning alignment process, thereby realizing the automated judgment and precise control of the optical path alignment.

[0065] In some embodiments of this application, the interference contrast generating device can also perform low-noise amplification and operational amplification on the electrical signal corresponding to the interference optical signal to ensure that the electrical signal has a suitable signal-to-noise ratio and amplitude. After the electrical signal is appropriately amplified by the interference contrast generating device, the electrical signal corresponding to the interference optical signal can form optical interference fringes within the interference contrast generating device.

[0066] In one possible implementation of the first aspect, the beam adjustment unit is a piezoelectric reflector, the first adjustment element is a first piezoelectric screw, the second adjustment element is a second piezoelectric screw, and the optical element is a reflector; the first and second piezoelectric screws determine the positions of the dual-frequency beam in the first and second directions after passing through the reflector by controlling the tilt angle of the reflector; the parameter value of the first adjustment element is the amount of extension and retraction displacement of the first piezoelectric screw relative to the initial length, and the parameter value of the second adjustment element is the amount of extension and retraction displacement of the second piezoelectric screw relative to the initial length, where the initial length is the natural length of the piezoelectric screw when it is not energized.

[0067] Thus, by adjusting the extension and retraction displacement of the first and second piezoelectric screws, the tilt angle of the reflector relative to the initial posture can be changed, causing the incident dual-frequency beam to be deflected along the first and second directions after reflection, thereby precisely controlling the landing point of the beam on the target plane and realizing the control and adjustment of the beam direction.

[0068] In one possible implementation of the first aspect, the signal conversion module includes: an interference unit and a photoelectric conversion unit; step S4 further includes:

[0069] S41: The interference unit receives the reference light and the measurement light, interferes with the reference light and the measurement light to generate an optical interference light field, and sends the optical interference light field to the photoelectric conversion unit.

[0070] S42: The photoelectric conversion unit converts the optical interference light field into an optical interference fringe electrical signal and sends it to the interference contrast generation device.

[0071] Secondly, this application also provides an automatic optical path alignment system, which includes a light source, a beam adjustment module, an interferometer group, a signal conversion module, an interference contrast generation device, and a control module; wherein: the light source is used to generate a dual-frequency beam and incident the dual-frequency beam onto the beam adjustment module, the dual-frequency beam including a first frequency light and a second frequency light; the beam adjustment module is used to receive the dual-frequency beam and send the dual-frequency beam to the interferometer group, wherein the beam adjustment module includes m beam adjustment units, where m is an integer greater than or equal to 1; each beam adjustment unit includes an optical element, a first adjustment element, and a second adjustment element, the parameter values ​​of the first adjustment element and the second adjustment element being used to determine the optical path alignment of the dual-frequency beam. The optical element is positioned in a first direction and a second direction, with the first direction perpendicular to the second direction. An interferometer group is used to form a reference beam and a measurement beam from the first and second frequency beams, respectively, and sends the reference beam and measurement beam to the signal conversion module. The signal conversion module converts the reference beam and measurement beam into optical interference fringe electrical signals. An interference contrast generating device receives the optical interference fringe electrical signals and generates interference contrast values ​​for the reference beam and measurement beam. A control module acquires the interference contrast values ​​generated by the interference contrast generating device and controls the first and / or second adjusting elements of the beam adjustment module to adjust the position of the optical element in the first and / or second directions based on the interference contrast values.

[0072] In one possible implementation of the second aspect, the beam adjustment unit is a piezoelectric reflector, the first adjustment element is a first piezoelectric screw, the second adjustment element is a second piezoelectric screw, and the optical element is a reflector; the first and second piezoelectric screws determine the positions of the dual-frequency beam in the first and second directions after passing through the reflector by controlling the tilt angle of the reflector; the parameter value of the first adjustment element is the amount of extension and retraction displacement of the first piezoelectric screw relative to the initial length, and the parameter value of the second adjustment element is the amount of extension and retraction displacement of the second piezoelectric screw relative to the initial length, where the initial length is the natural length of the piezoelectric screw when it is not energized.

[0073] In one possible implementation of the second aspect, the polarization directions of the first frequency light and the second frequency light are orthogonal; the signal conversion module includes an interference unit and a photoelectric conversion unit; wherein, the interference unit is used to receive the reference light and the measurement light, and interfere the reference light and the measurement light to generate an optical interference light field; the photoelectric conversion unit is used to convert the optical interference light field into an optical interference fringe electrical signal and send it to the interference contrast generation device.

[0074] The specific implementation and beneficial effects of the second aspect described above can be referred to the description of the first aspect and any embodiment of the first aspect, and will not be repeated here. Attached Figure Description

[0075] Figure 1A schematic diagram of an automatic optical path alignment system for a laser interferometer provided in this application embodiment;

[0076] Figure 2 A schematic flowchart illustrating an automatic optical path alignment method for a laser interferometer provided in this application embodiment;

[0077] Figure 3 A schematic diagram of another automatic optical path alignment system for a laser interferometer provided in this application embodiment;

[0078] Figure 4 This is a schematic diagram of the structure of a beam adjustment unit provided in an embodiment of this application;

[0079] Figure 5 A schematic flowchart illustrating another automatic optical path alignment method for a laser interferometer provided in this application embodiment;

[0080] Figure 6 A schematic diagram of the curve of an interference optical signal changing over time, provided as an embodiment of this application;

[0081] Figure 7 A schematic diagram of the structure of another automatic optical path alignment system for a laser interferometer provided in this application embodiment;

[0082] Figure 8 A flowchart illustrating another automatic optical path alignment method for a laser interferometer provided in this application embodiment;

[0083] Figure 9 A schematic flowchart illustrating another automatic optical path alignment method for a laser interferometer provided in this application embodiment;

[0084] Figure 10 This is a flowchart illustrating an automatic optical path alignment method for a laser interferometer, provided as an embodiment of this application.

[0085] Explanation of reference numerals in the attached figures:

[0086] 100 - Automatic optical alignment system; 10 - Light source; 20 - Beam adjustment module; 21 - First beam adjustment unit; 22 - Second beam adjustment unit; 30 - Interference mirror group; 40 - Interference contrast generation device; 50 - Control module; 60 - Signal conversion module;

[0087] 211-First optical element; 212-First first adjustment element; 213-First second adjustment element; 214-First frame; 221-Second optical element; 222-Second first adjustment element; 223-Second second adjustment element; 224-Second frame; 31-Polarizing beam splitter; 32-First waveplate; 33-Second waveplate; 34-Corner cone; 35-Mirror under test; 51-Control unit; 52-Drive unit; 61-Interference unit; 611-Polarizer; 612-Coupled; 613-Fiber optic cable; 62-Photoelectric conversion unit;

[0088] 2141 - Fixed end of the frame; 2142 - Movable end of the frame; O1 - Fulcrum; 215 - Traction spring;

[0089] 521 - Communication subunit; 522 - High voltage drive subunit. Detailed Implementation

[0090] The following specific embodiments illustrate the implementation of this application. Those skilled in the art can easily understand other advantages and effects of this application from the content disclosed in this specification. Although the description of this application will be presented in conjunction with some embodiments, this does not mean that the features of this application are limited to this embodiment. On the contrary, the purpose of describing the application in conjunction with embodiments is to cover other options or modifications that may be derived based on the claims of this application. To provide a thorough understanding of this application, many exemplary details will be included in the following description. This application may also be implemented without using these details. Furthermore, to avoid confusion or obscuring the focus of this application, some specific details will be omitted in the description. It should be noted that, unless otherwise specified, the embodiments and features in the embodiments of this application can be combined with each other.

[0091] It should be noted that in this specification, similar reference numerals and letters in the following figures indicate similar items. Therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures.

[0092] The following explains the terminology that may appear in the embodiments of this application.

[0093] In the description of the embodiments of this application, "and / or" is merely a way of describing the relationship between associated objects, indicating that there can be three relationships. For example, A and / or B can represent three situations: A exists alone, A and B exist simultaneously, and B exists alone. In addition, the character " / " in this document generally indicates that the associated objects before and after are in an "or" relationship. When there are multiple associated objects, it can represent choosing one, choosing two, or choosing all.

[0094] In the description of the embodiments of this application, it should be noted that the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing the embodiments of this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the embodiments of this application.

[0095] Furthermore, it should be understood that in this application specification and the appended claims, the terms "first," "second," "third," etc., are used only for distinguishing descriptions and should not be construed as indicating or implying relative importance, nor are they used to describe a specific order or sequence.

[0096] In the description of the embodiments of this application, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in the embodiments of this application based on the specific circumstances.

[0097] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the implementation methods of this application will be further described in detail below with reference to the accompanying drawings.

[0098] Currently, to achieve optimal measurement accuracy with laser interferometers, precise alignment of the optical path is required during manual assembly and adjustment. However, manual adjustment is inefficient, costly, time-consuming, and highly dependent on the expertise of the personnel involved, making it difficult to meet the stability requirements of optical path alignment. Furthermore, since laser interferometers are often embedded in systems such as semiconductor measurement equipment, lithography machines, or precision displacement stages, they often face space constraints or vacuum environments, making subsequent manual maintenance extremely inconvenient or even impossible, thus hindering the long-term stable operation of the laser interferometer equipment.

[0099] In addition, current methods for optical path alignment usually rely on beam angle signals to determine whether the optical paths overlap. This method only detects angle values, but it is difficult to reflect the optical path difference and coherence of the beam.

[0100] To address the issue that beam angle signals cannot characterize optical path difference and coherence, some current solutions employ position-sensitive detectors to record the position of the light spot and achieve optical path alignment and reset. However, this position is not an absolute reference and is prone to shift due to environmental fluctuations, support stress, and other factors, resulting in poor accuracy improvement.

[0101] To address the technical problems of poor optical path alignment accuracy and difficult maintenance in laser interferometers, this application provides an automatic optical path alignment method for laser interferometers. This method involves incident a dual-frequency beam onto an interferometer group via a beam adjustment module. After interference by the interferometer group, the beam is converted into an optical interference fringe electrical signal by a signal conversion module and sent to an interference contrast generation device. This device then generates an interference contrast value in real time. A control module adjusts the adjustment elements in the beam adjustment module based on this value, thereby changing the spatial overlap of the dual-frequency beam as it exits the beam adjustment module, guiding the beam towards the optimal alignment state. This method improves the assembly and adjustment efficiency of the laser interferometer and automatically maintains its alignment accuracy during use, ensuring long-term stability. Furthermore, this method overcomes the limitations imposed by limited maintenance space and vacuum environments on maintenance operations, thus achieving automatic optical path alignment of the laser interferometer. The embodiments of this application are further described below with reference to the accompanying drawings.

[0102] Figure 1 This application provides a schematic diagram of the structure of an automatic optical path alignment system for a laser interferometer. Figure 2 This application provides a flowchart illustrating an automatic optical path alignment method for a laser interferometer. Figure 2 The method shown can be applied to Figure 1 The structure shown will not be described again below.

[0103] refer to Figure 1 In some embodiments of this application, the automatic optical path alignment system 100 may include a light source 10, a beam adjustment module 20, an interferometer mirror group 30, an interference contrast generation device 40, a signal conversion module 60, and a control module 50. The beam adjustment module 20 may include m beam adjustment units, where m is an integer greater than or equal to 1. For example, in... Figure 1 In this context, m is 2, meaning there are two beam adjustment units, which can be a first beam adjustment unit 21 and a second beam adjustment unit 22. It should be noted that in other embodiments, the beam adjustment module 20 may have other numbers of beam adjustment units, such as 1, 3, or 4, etc., and this application does not impose any limitations on this.

[0104] It should be noted that in the structural drawings of any optical path automatic alignment system in this application, the connecting lines with arrows represent the propagation path of the light beam between different structures, and the arrows indicate the propagation direction of the light beam; the connecting lines without arrows represent electrical connections or other connection methods for realizing signal transmission, so as to distinguish the optical path from other control signal paths.

[0105] refer to Figure 2and combined Figure 1 The automatic optical path alignment method may include the following steps:

[0106] S1: The light source 10 generates a dual-frequency beam and directs the dual-frequency beam onto the beam adjustment module 20. The dual-frequency beam includes a first frequency light and a second frequency light.

[0107] In some embodiments of this application, the light source 10 is a dual-frequency laser light source. A dual-frequency beam refers to a laser beam output by the light source 10 containing two different frequencies. The first frequency light and the second frequency light share the same optical path, and their frequency difference, initial phase difference, and polarization directions are orthogonal, or their polarization directions are perpendicular to each other. For example, the polarization directions of the first frequency light and the second frequency light can be horizontal polarization (P-polarization) and vertical polarization (S-polarization), or vice versa.

[0108] In some embodiments of this application, the beam adjustment module 20 adjusts the direction of the dual-frequency beam. Specifically, the beam adjustment module 20 can adjust the spatial overlap of the first frequency light and the second frequency light when they exit the beam adjustment module 20. This spatial overlap is positively correlated with the interference contrast value of the first frequency light and the second frequency light. Since the interference contrast value directly reflects the optical path difference matching degree and coherence state of the dual-frequency beam, and the optical path difference matching degree and coherence state determine the alignment accuracy of the dual-frequency beam, the beam adjustment module 20 can improve the alignment accuracy of the dual-frequency beam by optimizing the spatial overlap.

[0109] The following is combined with Figure 3 and Figure 4 An exemplary structure of the beam adjustment module 20 is described below.

[0110] Figure 3 This application provides a schematic diagram of the structure of another automatic optical path alignment system for a laser interferometer. Figure 4 A schematic diagram of the structure of a beam adjustment unit provided in this application is shown. Figure 3 for Figure 1 A specific exemplary structural diagram; Figure 4 Therefore Figure 1 The structure of the beam adjustment unit is described using the first beam adjustment unit 21 as an example. It can be understood that the structure of other beam adjustment units in the beam adjustment module 20 can also be referred to. Figure 4 They will not be described in detail below.

[0111] refer to Figure 3In the beam adjustment module 20, each beam adjustment unit may include an optical element, a first adjustment element, and a second adjustment element. The parameter values ​​of the first adjustment element and the second adjustment element are used to determine the positions of the dual-frequency beam generated by the light source 10 in the first direction and the second direction after passing through the optical element, respectively. The first direction is perpendicular to the second direction.

[0112] For ease of explanation, in the following description, the width direction of each beam adjustment unit is defined as the x-axis direction, the length direction as the y-axis direction, and the thickness direction as the z-axis direction. The x-axis, y-axis, and z-axis directions can be perpendicular to each other.

[0113] The first direction can be the pitch direction (i.e., the angle in the yz plane) of rotation around the x-axis, and the second direction can be the azimuth direction (i.e., the angle in the xz plane) of rotation around the y-axis; or conversely, the first direction can be the azimuth direction of rotation around the y-axis, and the second direction can be the pitch direction of rotation around the x-axis. Alternatively, one of the first and second directions corresponds to lateral (horizontal direction, i.e., xz plane) adjustment, and the other corresponds to longitudinal (vertical direction, i.e., yz plane) adjustment.

[0114] For example, in Figure 3 In the control module 50, there are four ports, namely X1, Y1, X2 and Y2. Ports X1 and Y1 are used to control the parameter values ​​of the first adjustment element and the second adjustment element of the first beam adjustment unit, respectively; ports X2 and Y2 are used to control the parameter values ​​of the first adjustment element and the second adjustment element of the second beam adjustment unit, respectively.

[0115] It is understood that the perpendicularity in this application is not absolute perpendicularity. Approximate perpendicularity due to processing and assembly errors, such as an angle of 89° between two structural features, is also within the scope of mutual perpendicularity in this application. Similarly, the parallelism in this application is not absolute parallelism. Approximate parallelism due to processing and assembly errors, such as an angle of 1° between two structural features, is also within the scope of mutual parallelism in this application. The limitations on mutual parallelism and mutual perpendicularity will not be repeated below.

[0116] In some embodiments of this application, reference is made to Figure 3 and Figure 4 The beam adjustment module 20 can be a piezoelectric mirror assembly, and correspondingly, each beam adjustment unit is a piezoelectric mirror. For example, Figure 3 In the first beam adjustment unit 21, there are a first optical element 211, a first first adjustment element 212, a first second adjustment element 213 and a first frame 214; wherein, the first frame 214 is used to fix or support the first optical element 211, the first first adjustment element 212 and the first second adjustment element 213.

[0117] In some embodiments of this application, reference continues to be made to Figure 4 The first adjusting element 212 is a first piezoelectric screw, the first second adjusting element 213 is a first second piezoelectric screw, and the first optical element 211 is a reflector, such as a high-reflectivity mirror. The first and second piezoelectric screws determine the positions of the dual-frequency beam in the first and second directions after passing through the reflector by controlling the tilt angle of the reflector. The parameter value of the first adjusting element is the extension / retraction displacement of the first piezoelectric screw relative to its initial length, and the parameter value of the second adjusting element is the extension / retraction displacement of the second piezoelectric screw relative to its initial length, where the initial length is the natural length of the piezoelectric screw when not energized.

[0118] Thus, by adjusting the extension and retraction displacement of the first and second piezoelectric screws, the tilt angle of the reflector relative to the initial posture can be changed, causing the incident dual-frequency beam to be deflected along the first and second directions after reflection, thereby precisely controlling the landing point of the beam on the target plane and realizing the control and adjustment of the beam direction.

[0119] In some embodiments of this application, reference continues to be made to Figure 4 The first frame 214 includes a fixed end 2141 and a movable end 2142. The first beam adjustment unit 21 may further include a fulcrum O1 located at the movable end 2142, serving as the rotational swing center of the movable end 2142. The fixed end 2141 is used for fixed connection to an external support structure, and the movable end 2142 is used to carry the first optical element 211 and is configured to swing around the fulcrum O1 to change the tilt angle of the reflector.

[0120] The first beam adjustment unit 21 may also include a traction spring 215, which provides a restoring force when the piezoelectric screw retracts, pulling the movable end 2142 of the frame back to its initial position to ensure that the movable end 2142 of the frame maintains reliable contact with the end face of the piezoelectric screw.

[0121] In some embodiments of this application, reference continues to be made to Figure 3 The second beam adjustment unit 22 includes a second optical element 221, a second first adjustment element 222, a second second adjustment element 223, and a second frame 224. The specific structures of the second optical element 221, the second first adjustment element 222, the second second adjustment element 223, and the second frame 224 are the same as or similar to those of the first optical element 211, the first first adjustment element 212, the first second adjustment element 213, and the first frame 214, and can be referred to the contents of the above embodiments, which will not be repeated here.

[0122] In this way, the first beam adjustment unit 21 and the second beam adjustment unit 22 can adjust the direction of the dual-frequency beam in turn, thereby gradually reducing the lateral and longitudinal positional deviations of the dual-frequency beam and gradually increasing the spatial overlap between the first frequency light and the second frequency light.

[0123] In other embodiments of this application, the beam adjustment module 20 can be a piezoelectric stage, which may include a stage and m optical elements disposed on the stage. Each optical element is provided with a corresponding first adjustment element and a second adjustment element. The parameter values ​​of the first adjustment element and the second adjustment element are used to determine the positions of the dual-frequency beam generated by the light source 10 in the first direction and the second direction after passing through the optical element, respectively. The specific contents of the first adjustment element and the second adjustment element can be referred to the description of the above embodiments, and will not be repeated here.

[0124] It should be noted that in other embodiments, the beam adjustment module 20 may have other structures, and this application does not limit this.

[0125] S2: The beam adjustment module 20 receives the dual-frequency beam and sends the dual-frequency beam to the interferometer group 30.

[0126] In some embodiments of this application, each beam adjustment unit in the beam adjustment module 20 sequentially adjusts the direction of the dual-frequency beam, and then guides the adjusted dual-frequency beam to the interferometer group 30.

[0127] S3: The interferometer group 30 enables the first frequency light and the second frequency light to form the reference light and the measurement light respectively, and sends the reference light and the measurement light to the signal conversion module 60.

[0128] In some embodiments of this application, reference continues to be made to Figure 1 and Figure 3The interferometer group 30 can be a single-axis or multi-axis interferometer. In this embodiment, a single-axis Michelson interferometer is used as an example. That is, the interferometer group 30 includes a polarizing beam splitter 31 (PBS), a first waveplate 32, a second waveplate 33, a corner cube mirror 34, and a test mirror 35. Among them, the polarizing beam splitter 31 serves as a beam splitting element, used to separate the incident dual-frequency beam into a first frequency light (such as horizontally polarized light f1) and a second frequency light (such as vertically polarized light f2) for transmission, and guides them to the measurement optical path and the reference optical path, respectively. The first waveplate 32 and the second waveplate 33 are both quarter-wave plates (WP), respectively set in the measurement optical path and the reference optical path, used to transmit the beam to achieve round-trip phase modulation of the beam. The corner cube mirror 34 is set in the reference optical path, used to reflect the second frequency light back to the polarizing beam splitter 31, ensuring that the second frequency light returns to the polarizing beam splitter 31 along the original path to form the reference light. The test mirror 35 is a reflector, with its reflecting surface placed parallel to the output surface of the interferometer group 30. It is used to reflect the first frequency light back to the polarization beam splitter 31 to form the measurement light. The first frequency light reflected by the test mirror 35 and the second frequency light reflected by the cornerstone mirror 34 converge at the polarization beam splitter 31, and are finally output from the output end of the interferometer group 30 to form the reference light and the measurement light. The reference light and the measurement light are then sent to the signal conversion module 60. The reference light and the measurement light are typically spatially misaligned when not precisely adjusted by the beam adjustment module 20.

[0129] In some other embodiments of this application, the cornerstone 34 may also be replaced by a reflector.

[0130] S4: Signal conversion module 60 converts the reference light and measurement light into optical interference fringe electrical signals.

[0131] In some embodiments of this application, reference continues to be made to Figure 3 The signal conversion module 60 may include an interference unit 61 and a photoelectric conversion unit 62.

[0132] Figure 5 A flowchart illustrating another automatic optical path alignment method provided in this application is shown, wherein, Figure 5 for Figure 2 An exemplary specific process for step S4.

[0133] Step S4 may further include the following steps:

[0134] S41: Interference unit 61 receives reference light and measurement light, interferes with the reference light and measurement light to generate an optical interference light field, and sends the optical interference light field to photoelectric conversion unit 62.

[0135] S42: The photoelectric conversion unit 62 converts the optical interference light field into an optical interference fringe electrical signal and sends it to the interference contrast generation device 40.

[0136] In some embodiments of this application, reference continues to be made to Figure 3 The interference unit 61 may include a polarizer 611, a coupler 612, and an optical fiber 613, and the photoelectric conversion unit 62 includes a photodetector. The reference light and measurement light output from the output end of the interference mirror group 30 first pass through the polarizer 611. The polarizer 611 may include a polarizer. The optical axis of the polarizer may be set at a 45° angle with the polarization direction of the reference light and measurement light output from the output end of the interference mirror group 30, thereby converting the reference light and measurement light with orthogonal polarization directions into the same polarization direction, so as to generate a stable interference effect in the beam overlap region, and then generate an optical interference light field. Subsequently, the coupler 612 efficiently collects the optical interference light field.

[0137] In some embodiments of this application, the coupler 612 may include a coupling lens; wherein the coupling lens couples the optical interference light field into the optical fiber 613, and transmits the optical interference light field to the photoelectric conversion unit 62 through the optical fiber 613, and converts it into an optical interference fringe electrical signal for the interference contrast generation device 40 to analyze.

[0138] It should be noted that in other embodiments, the interference mirror group 30 may also adopt other structures, and this application does not impose any restrictions on the specific structure of the interference mirror group 30.

[0139] In some other embodiments, the interaction between the coupler 612 and the optical fiber 613 in the interference unit can be directly achieved using spatial light. The reference light and the measurement light enter the photoelectric conversion unit 62 directly in the form of spatial light after passing through the polarizer 611. If a change in the optical path direction is required during this process, an optical mirror can be used between the polarizer 611 and the photoelectric conversion unit 62 to change the direction of the light.

[0140] S5: The interference contrast generating device 40 receives the optical interference fringe electrical signal and generates the interference contrast value of the reference light and the measurement light.

[0141] In some embodiments of this application, the polarization directions of the first frequency light and the second frequency light are orthogonal, and the interference contrast value is positively correlated with the spatial overlap of the reference light and the measurement light; wherein, the formula for calculating the interference contrast value is: ,in, The maximum value of the electrical signal in the optical interference fringes. This represents the minimum value of the electrical signal in the optical interference fringes.

[0142] Figure 6This paper presents a schematic diagram illustrating the time-varying curve of an optical interference fringe electrical signal provided in this application. The optical interference fringe electrical signal I exhibits a cosine variation with time t.

[0143] In some embodiments of this application, the interference contrast generating device 40 can also perform low-noise amplification and operational amplification of the optical interference fringe electrical signal to ensure that the electrical signal has a suitable signal-to-noise ratio and amplitude. After the interference contrast generating device 40 performs appropriate amplification on the optical interference fringe electrical signal, the optical interference fringe electrical signal satisfies the following conditions: Figure 6 The graph shown is a curve.

[0144] Since the frequency difference of the dual-frequency beam is fixed, the maximum value of the optical interference fringe electrical signal is taken in each period of the cosine function. minimum value Through formula The interference contrast value can be obtained by , where V is the abbreviation for Visibility.

[0145] In this way, by converting the spatial overlap of the dual-frequency beams into a quantifiable interference contrast value, the control module 50 can monitor and control the optical path alignment status in real time, and provide feedback for the adjustment or reset of the adjustment elements in the subsequent scanning alignment process, thereby realizing the automated judgment and precise control of the optical path alignment.

[0146] S6: Control module 50 executes the scanning alignment process; the scanning alignment process includes m unit scanning alignment processes executed separately, the kth unit scanning alignment process corresponds to the kth beam adjustment unit, k=1, 2, ..., m.

[0147] The scanning alignment process for the kth unit includes: fixing the parameter value of the second adjustment element of the kth beam adjustment unit and the parameter values ​​of the remaining beam adjustment units; adjusting the parameter value of the first adjustment element of the kth beam adjustment unit; and acquiring the interference contrast value generated by the interference contrast generation device in real time to form a first interference contrast value group; and resetting the parameter value of the first adjustment element of the kth beam adjustment unit to the parameter value of the first adjustment element of the kth beam adjustment unit corresponding to the maximum interference contrast value in the first interference contrast value group; fixing the parameter value of the first adjustment element of the kth beam adjustment unit and the parameter values ​​of the remaining beam adjustment units; adjusting the parameter value of the second adjustment element of the kth beam adjustment unit; and acquiring the interference contrast value generated by the interference contrast generation device 40 in real time to form a second interference contrast value group; and resetting the parameter value of the second adjustment element of the kth beam adjustment unit to the parameter value of the second adjustment element of the kth beam adjustment unit corresponding to the maximum interference contrast value in the second interference contrast value group.

[0148] It should be noted that before the interference contrast generation device 40 generates the interference contrast value, an initial state confirmation step of the optical path can be included. Specifically, the interference contrast generation device 40 needs to be able to detect a valid interference signal, that is, the reference light and the measurement light need to have a spatial overlap, so that the interference contrast value is usually between 0 and 1, for example, 0.2, 0.5, or 1, etc. In this case, the optical path can be considered to be in an initial state where automatic alignment adjustment can be performed, and the subsequent scanning alignment process can continue. If the interference contrast value is not within the range of 0 to 1 or no valid interference signal is detected, it indicates that the reference light and the measurement light may be completely separated, and manual or other methods are required to perform rough alignment first, so that the two beams spatially overlap.

[0149] Additionally, it should be noted that in the embodiments of this application, fixing the parameter values ​​of one or more adjustment elements can mean keeping the current parameter value of the adjustment element unchanged, or locking it in its current state so that it does not change with the adjustment actions of other adjustment elements. This will not be repeated below. Furthermore, in the above-mentioned k-th unit scanning alignment process, the remaining beam adjustment units refer to other beam adjustment units besides the k-th beam adjustment unit.

[0150] Furthermore, it should be noted that in the embodiments of this application, resetting the parameter value to the parameter value of the adjustment element corresponding to the maximum interference contrast value in the corresponding interference contrast value group means adjusting or restoring the current parameter value of the adjustment element to the parameter value corresponding to the maximum interference contrast value recorded in the interference contrast value group, so that the beam adjustment unit is in the optimal optical path alignment position under this operation, which will not be repeated below.

[0151] Specifically, in S6, the control module 50 may include at least 2m drive channels, each channel being used to drive an adjustment element (e.g., a piezoelectric screw) to control its extension or retraction. For example, each channel may be responsible for driving the adjustment in one adjustment direction (e.g., an axis), thus enabling the beam adjustment unit to oscillate under the drive of the control module 50, thereby causing a change in the interference contrast value due to the deflection of the optical path.

[0152] In the scanning alignment process of the kth unit, the first interference contrast value group can refer to the data set or data sequence formed by the control module 50 continuously controlling and adjusting the parameter value of the first adjustment element during the adjustment of the first adjustment element of the kth beam adjustment unit, and synchronously recording the interference contrast value corresponding to each parameter value. Similarly, the second interference contrast value group can refer to the data set formed by adjusting the parameter value of the second adjustment element in a similar manner after fixing the parameter value of the first adjustment element of the kth beam adjustment unit, and synchronously recording the interference contrast value corresponding to each parameter value.

[0153] The first and second interference contrast value sets contain a maximum value (or peak value). Therefore, the parameter values ​​of the first and second adjustment elements corresponding to this peak value can be locked. This maximum value can be obtained, for example, through an inflection point identification method. That is, when both the preceding and following values ​​of a certain interference contrast value are less than the current value, the current value can be determined to be the maximum value. In this way, the parameter values ​​of the first and second adjustment elements corresponding to this peak value can be locked, thereby resetting the beam adjustment unit to its optimal orientation in that direction. This ensures that the spatial overlap of the dual-frequency beams reaches or approaches optimal, thereby ensuring that the optical path is in or near optimal alignment.

[0154] It is understood that in S6 above, all the adjustment elements (e.g., piezoelectric screws) can be scanned one by one. For example, when scanning each adjustment element, the interference contrast value corresponding to each scanning position of the adjustment element can be recorded simultaneously, and the adjustment element can be reset to the position corresponding to the maximum interference contrast value after the scan is completed. Then, the next adjustment element can be scanned until all adjustment elements have been scanned and reset.

[0155] In the k-th unit scanning alignment process, fixing the parameter value of the first adjustment element of the k-th beam adjustment unit means locking the parameter value of the first adjustment element to the value after being reset in the aforementioned steps (i.e., the parameter value corresponding to the maximum interference contrast value in the first interference contrast value group), so that it remains unchanged in the subsequent adjustment of the second adjustment element, thereby ensuring that the optimal alignment state in the first direction is not destroyed and achieving decoupling optimization of the two adjustment directions.

[0156] Thus, by using interference contrast values ​​as feedback information, automated closed-loop adjustment of the beam direction can be achieved, completing optical path alignment without manual intervention. This improves assembly efficiency and reduces reliance on operator expertise. Furthermore, it enables remote automatic alignment in scenarios where manual maintenance is difficult, such as space-constrained or vacuum environments, enhancing system maintainability.

[0157] In some embodiments of this application, reference continues to be made to Figure 3 The control module 50 may include a control unit 51 and a drive unit 52. The control unit 51 may generate control commands (such as adjustment commands required for scanning alignment or joint adjustment alignment processes) and send the control commands to the drive unit 52; the drive unit 52 may receive the control commands sent by the control unit 51 and convert the control commands into drive signals that can drive the various adjustment elements (such as piezoelectric screws) in the beam adjustment module 20 to move.

[0158] Figure 7 A schematic diagram of the structure of another automatic optical path alignment system for a laser interferometer provided in this application is shown. Among them, Figure 7 for Figure 3 A schematic diagram of a specific structure.

[0159] In some embodiments of this application, reference is made to Figure 7 The drive unit 52 includes a communication subunit 521 and a high-voltage drive subunit 522. The communication subunit 521 can receive control commands sent by the control unit 51 and can transmit the control commands to the high-voltage drive subunit 522. The high-voltage drive subunit 522 can generate corresponding high-voltage drive signals according to the control commands received by the communication subunit 521, and drive the various adjustment elements in the beam adjustment module 20 (such as the first adjustment element 212, the second adjustment element 213, the first adjustment element 222, and the second adjustment element 223 corresponding to the drive ports X1, Y1, X2, and Y2) through the high-voltage signals, thereby realizing automatic adjustment of the beam direction.

[0160] Figure 8 A flowchart illustrating another automatic optical path alignment method provided in this application is shown, wherein, Figure 8 exist Figure 2 Steps S7 and S8 have been added to the basic model.

[0161] In some embodiments of this application, reference is made to Figure 8 If m is greater than or equal to 2, then the following steps may also be included:

[0162] S7: The control module 50 acquires the interference contrast value generated by the interference contrast generating device 40 in real time. If the interference contrast value is greater than or equal to the first preset threshold, it is determined that the optical path is automatically aligned. Otherwise, S8 is executed.

[0163] In some embodiments of this application, the first preset threshold can be set to any suitable value according to the system noise level and accuracy requirements. It can be set arbitrarily, for example, to 80% to 98% of the theoretical maximum value of the interference contrast (i.e., 1). For example, the first preset threshold can be 0.8, 0.85, 0.9, 0.95, or 0.98, etc.

[0164] S8: The control module 50 executes the joint adjustment alignment process and ends the automatic optical path alignment. The joint adjustment alignment process includes executing the S81 first direction alignment process and the S82 second direction alignment process on the preset beam adjustment unit group respectively. The preset beam adjustment unit group includes at least two beam adjustment units.

[0165] S81 includes: under the condition that the parameter values ​​of each second adjustment element of the preset beam adjustment unit group and the parameter values ​​of the remaining beam adjustment units in the beam adjustment module are fixed, the parameter values ​​of each first adjustment element of the preset beam adjustment unit group are combined and adjusted to obtain the interference contrast value generated by the interference contrast generation device 40 in real time to form a third interference contrast value group, and the parameter values ​​of each first adjustment element of the preset beam adjustment unit group are reset to the parameter values ​​of each first adjustment element of the preset beam adjustment unit group corresponding to the maximum interference contrast value in the third interference contrast value group, and then the process is switched to the second direction alignment process.

[0166] S82 includes: under the condition that the parameter values ​​of each first adjustment element of the preset beam adjustment unit group and the parameter values ​​of the remaining beam adjustment units in the beam adjustment module are fixed, the parameter values ​​of each second adjustment element of the preset beam adjustment unit group are combined and adjusted to obtain the interference contrast value generated by the interference contrast generation device 40 in real time to form a fourth interference contrast value group, and the parameter values ​​of each second adjustment element of the preset beam adjustment unit group are reset to the parameter values ​​of each second adjustment element of the preset beam adjustment unit group when the interference contrast value in the fourth interference contrast value group is the largest.

[0167] It is understood that in step S8 above, the control module 50 can use a joint adjustment alignment (or combined scanning) process to coordinately adjust the preset beam adjustment unit group. Specifically, the first adjustment element of each beam adjustment unit in the preset beam adjustment unit group can be synchronously adjusted first, and then the second adjustment element of each beam adjustment unit in the preset beam adjustment unit group can be synchronously adjusted to ensure that the interference contrast value after each round of combined adjustment continuously increases or remains constant. This completes the joint adjustment alignment process of the entire optical path.

[0168] In the first direction alignment process, the third interference contrast value group can refer to: a set of data formed by a series of interference contrast values ​​acquired in real time during the process of the control module 50 combining and adjusting the parameter values ​​of the first adjustment elements of the preset beam adjustment unit group (e.g., alternating fine adjustment, synchronous fine adjustment, or adjustment according to a specific sequence) while fixing the parameter values ​​of each second adjustment element of the preset beam adjustment unit group and the remaining beam adjustment units.

[0169] Similarly, in the second direction alignment process, the fourth interference contrast value group can refer to: a set of data formed by a series of interference contrast values ​​acquired in real time during the process of adjusting the parameter values ​​of the second adjustment elements of the preset beam adjustment unit group in a similar combination, while fixing the parameter values ​​of the first adjustment elements of the preset beam adjustment unit group and the parameter values ​​of the other beam adjustment units.

[0170] Since there are peak values ​​(such as maximum values ​​or local optimum values) in both the third and fourth interference contrast value groups, the optimal parameter combination of each adjustment element in the preset beam adjustment unit group corresponding to the peak value can be locked. This allows the preset beam adjustment unit group to be reset to the optimal cooperative posture in that direction, thereby improving the spatial overlap of the dual-frequency beams and further improving the interference contrast value.

[0171] As described above, by combining scanning alignment with joint alignment, a progressive alignment process can be implemented, which can further eliminate coupling errors or residual deviations between multiple beam adjustment units on the basis of the initial alignment of a single beam adjustment unit, thereby achieving global optimization alignment of the optical path and improving the final interference contrast and system alignment accuracy.

[0172] In some embodiments of this application, the preset beam adjustment unit group in step S8 may include the two beam adjustment units closest to the interference contrast generating device 40; each beam adjustment unit in the preset beam adjustment unit group includes: a first adjustment element and a second adjustment element.

[0173] Thus, by coordinating the two beam adjustment units closest to the interference contrast generating device 40, the residual angular deviation and positional offset in the optical path can be further corrected on the basis of the initial alignment by single-axis scanning, thereby achieving local fine calibration of the beam direction. At the same time, since only two beam adjustment units at key positions are selected for combined optimization, the problem of low efficiency that may occur when coordinating more units can be avoided, thereby improving adjustment efficiency and adjustment accuracy.

[0174] Figure 9 A flowchart illustrating another automatic optical path alignment method provided in this application is shown, wherein, Figure 9 This is an exemplary specific process for step S81.

[0175] In some embodiments of this application, reference is made to Figure 9 In the nth beam adjustment unit, the current parameter value and parameter value step size of the first adjustment element are respectively and n=1, 2, ..., m; the first direction alignment process in step S81 may further include:

[0176] S811: Control module 50 executes the first joint modulation factor identification process.

[0177] The first coordination factor identification process includes: recording the current parameter values ​​of the two first adjustment elements of the preset beam adjustment unit group. and and the current interference contrast value generated by the interference contrast generation device. ; and set the parameter value step size of the two first adjustment elements of the preset beam adjustment unit group respectively. With the parameter values ​​of each second adjustment element in the preset beam adjustment unit group and the parameter values ​​of the remaining beam adjustment units in the beam adjustment module fixed, the parameter values ​​of the two first adjustment elements in the preset beam adjustment unit group are respectively adjusted to ( ),in,( , The first coordination factor is defined as (+1,+1), which includes the following combinations: (+1,-1), (+1,-1), (-1,+1), and (-1,-1). The interference contrast values ​​generated by the interference contrast generation device corresponding to each combination of the first coordination factor are acquired in real time. , , and ,in, , , , and Form the fifth set of interference contrast values; if the maximum value in the fifth set of interference contrast values... Then The corresponding first coordination factor is used as the first target coordination factor. ), then proceed to S812; if The parameter values ​​of the two first adjustment elements of the preset beam adjustment unit group are reset to ( , ), thus ending the first direction alignment process.

[0178] It is understandable that this first coordination factor identification process can quickly identify the optimal coordinated adjustment direction that increases the interference contrast value. Specifically, through the preceding parameter values... and By selecting four representative directions (i.e., the four combinations of the first tuning factor) around the target and making tentative adjustments, and comparing the interference contrast response in each direction, it is possible to effectively determine whether there is a region with a better parameter combination. In this way, invalid fine scanning in directions with no obvious gain can be avoided. If the interference contrast values ​​in all four directions do not exceed the current value, it indicates that the current position may have reached a local optimum, and therefore the adjustment in that direction can be terminated.

[0179] It should be noted that, in When the first direction alignment process ends, the fifth interference contrast value group obtained in S811 is used as the third interference contrast value group obtained in S81 above.

[0180] The fifth set of interference contrast values ​​refers to the set of data formed by the control module 50 recording the interference contrast values ​​of the two first adjustment elements of the preset beam adjustment unit group at the current parameter values ​​during the first coordination factor identification process, and the interference contrast values ​​acquired in real time when the parameter value combination is adjusted to the corresponding position according to the above four combinations of the first coordination factor. Therefore, the maximum value in the fifth set of interference contrast values ​​can be used as the basis for determining the optimal coordinated adjustment direction.

[0181] Thus, by introducing a joint adjustment factor for directional prediction, the correct adjustment direction can be quickly screened in the early stages of combined adjustment, thereby improving the efficiency of the joint adjustment alignment process.

[0182] S812: Control module 50 executes the first optimization process.

[0183] The first optimization process includes: adjusting the parameter values ​​of the two first adjustment elements of the preset beam adjustment unit group to ( ),in, The number of steps, and in During the process of incrementing by 1 sequentially, each step is acquired and recorded in real time. The parameter value combination corresponds to the interference contrast value generated by the interference contrast generation device. This is done to form the sixth interference contrast value group, and to reset the parameter values ​​of each first adjustment element in the preset beam adjustment unit group to the maximum interference contrast value in the sixth interference contrast value group. The parameter values ​​of each first adjustment element in the corresponding preset beam adjustment unit group.

[0184] The sixth interference contrast value group can refer to the asynchronous values ​​recorded synchronously when the control module 50 gradually changes the parameter values ​​of the two first adjustment elements of the preset beam adjustment unit group with a preset step size during the continuous stepping process along the direction indicated by the first target modulation factor. The data set formed by the corresponding interference contrast values. Therefore, the peak value in this sixth interference contrast value set can be used as the basis for determining the optimal parameter combination in the first direction.

[0185] It should be noted that, in At this time, the sixth interference contrast value group obtained in S812 is used as the third interference contrast value group obtained in S81 above.

[0186] In some embodiments of this application, the final number of steps in step S812 can be the number of steps corresponding to obtaining the maximum value plus 1. That is, if the maximum value of the interference contrast value in the sixth interference contrast value group is detected at step i, the actual total number of steps executed can be i+1, so as to ensure the integrity verification of the peak judgment condition and record the trend change after the peak, thereby more accurately confirming the peak position.

[0187] S813: Switch to the second direction alignment process.

[0188] It can be understood that the first optimization process is a continuous adjustment process along this direction, based on the first joint adjustment factor identification process. Specifically, by increasing the number of steps... Starting from 1 and increasing sequentially, the parameter value combination of the two first adjustment elements can be continuously changed along the direction indicated by the first target adjustment factor, and the changing trend of the interference contrast value can be monitored in real time to form a sixth interference contrast value group that reflects the distribution characteristics of interference contrast in that direction.

[0189] Thus, by performing a continuous stepping process along the optimal direction after identification, the optimal parameter combination in the first direction can be precisely locked, avoiding problems such as insufficient accuracy due to excessive step size or insufficient sampling points. Simultaneously, this process dynamically determines the optimal position by recording changes in interference contrast values ​​in real time to prevent over-adjustment. Furthermore, by using the optimized state in the first direction as the initial condition for optimization in the second direction, decoupling and sequential optimization of the two adjustment directions can be achieved, reducing the complexity of simultaneous adjustment of multiple variables and improving the efficiency and accuracy of optical path alignment.

[0190] In some embodiments of this application, in step S812, the maximum value of the interference contrast value in the sixth interference contrast value group is obtained. The method can be: when At that time, Steps No more additions will be made.

[0191] This criterion can be used to identify local maxima (i.e., peak points) in the sixth set of interference contrast values. Specifically, when the... The interference contrast value of the first step is less than that of the second step. The value of the step, and the first The value of the step is greater than the first step. When the value of the step is given, it indicates the number of steps. The current step position represents the optimal point along that step direction; continuing to adjust along this direction will cause a decrease in the interference contrast value. Therefore, the process can be stopped promptly when a peak feature is detected, thereby improving optical path alignment efficiency and avoiding unnecessary resource waste.

[0192] Thus, by introducing this peak detection step, timely termination can be achieved in the first optimization process to quickly lock in the optimal parameter combination, thereby improving the convergence speed and adjustment efficiency of optical path alignment. Simultaneously, this step can effectively prevent over-driving of the adjustment elements or excessive swaying of the mechanical structure, extending the lifespan of the beam adjustment unit. Furthermore, by using this peak point as a reset reference, it can be ensured that the two first adjustment elements are precisely reset to the optimal cooperative posture in this direction, thereby achieving local optimization of interference contrast in the first direction.

[0193] Figure 10 A flowchart illustrating another automatic optical path alignment method provided in this application is shown, wherein, Figure 10 This is an exemplary specific process for step S82.

[0194] It should be noted that since steps S81 and S82 in this application are similar in process architecture and adjustment logic (for example, both can include a joint debugging factor identification process and an optimization process), the following embodiments regarding step S82 can be understood with reference to the relevant description of step S81. To avoid redundancy, the details are not repeated here, but this application is not limited thereto. In other embodiments, steps S81 and S82 can also adopt different processes. For example, the execution order of the two can be adjusted (e.g., the second direction alignment process can be executed first, followed by the first direction alignment process), or different step size setting strategies can be adopted, or they can be executed alternately and iteratively (e.g., the first direction is adjusted by one step, then the second direction is adjusted by one step, and so on). These will not be elaborated here.

[0195] In some embodiments of this application, reference is made to Figure 10 In the nth beam adjustment unit, the current parameter value and parameter step size of the second adjustment element are respectively and The second-direction alignment process in step S82 may further include:

[0196] S821: Control module 50 executes the second joint regulation factor identification process.

[0197] The second coordination factor identification process includes: recording the current parameter values ​​of the two second adjustment elements of the preset beam adjustment unit group. and and the current interference contrast value generated by the interference contrast generation device. ; and set the parameter value step size of the two second adjustment elements of the preset beam adjustment unit group respectively. With the parameter values ​​of each first adjustment element in the preset beam adjustment unit group and the parameter values ​​of the remaining beam adjustment units in the beam adjustment module fixed, the parameter values ​​of the two second adjustment elements in the preset beam adjustment unit group are adjusted to ( ),in,( The second coordination factor is defined as (+1,+1), which includes the following combinations: (+1,-1), (+1,-1), (-1,+1), and (-1,-1). The interference contrast values ​​generated by the interference contrast generator corresponding to each combination of the second coordination factor are acquired in real time. , , and ,in, , , , and Form the seventh set of interference contrast values; if the maximum value in the seventh set of interference contrast values... Then The corresponding second coordination factor is used as the second objective coordination factor. , ), then proceed to S822; if Reset the parameter values ​​of the two second adjustment elements of the preset beam adjustment unit group to ( , ), thus ending the second-direction alignment process.

[0198] It should be noted that, in At this point, the second direction alignment process ends, and the seventh interference contrast value group obtained in S821 becomes the fourth interference contrast value group obtained in S82 above.

[0199] The seventh set of interference contrast values ​​can be described with reference to the description of the fifth set of interference contrast values, and will not be repeated here.

[0200] Similarly to step S811 above, by introducing a joint adjustment factor for directional prediction, the correct adjustment direction can be quickly screened in the early stage of combined adjustment, thereby improving the efficiency of the joint adjustment alignment process.

[0201] S822: Control module 50 executes the second optimization process.

[0202] The second optimization process includes: adjusting the parameter values ​​of the two second adjustment elements of the preset beam adjustment unit to ( ),in, The number of steps, and in During the process of incrementing by 1 sequentially, each step is acquired and recorded in real time. The interference contrast generated by the interference contrast generation device corresponds to the combination of parameter values. This forms the eighth interference contrast value group, and resets the parameter values ​​of each second adjustment element in the preset beam adjustment unit group to the maximum interference contrast value in the eighth interference contrast value group. The parameter values ​​of each second adjustment element in the corresponding preset beam adjustment unit group.

[0203] The eighth interference contrast value group can be referred to the description of the sixth interference contrast value group above, and will not be repeated here.

[0204] It should be noted that, in At this time, the eighth interference contrast value group obtained in S822 is used as the fourth interference contrast value group obtained in S82 above.

[0205] In some embodiments of this application, the final number of steps in step S822 can be the number of steps corresponding to obtaining the maximum value plus 1. That is, if the maximum value of the interference contrast value in the eighth interference contrast value group is detected at step j, the actual total number of steps executed can be j+1, so as to ensure the integrity verification of the peak judgment condition and record the trend change after the peak, thereby more accurately confirming the peak position.

[0206] Thus, by continuously stepping along the optimal direction after identification, the optimal parameter combination in the second direction can be precisely locked, avoiding problems such as insufficient accuracy due to excessive step size or insufficient sampling points. Simultaneously, this process dynamically determines the optimal position by recording changes in interference contrast values ​​in real time to prevent over-adjustment.

[0207] In some embodiments of this application, in step S822, the maximum value of the interference contrast in the eighth interference contrast value group is obtained. The method is: when At that time, Steps No more additions will be made.

[0208] Thus, by introducing this peak detection step, timely termination can be achieved in the second optimization process to quickly lock in the optimal parameter combination, thereby improving the convergence speed and adjustment efficiency of optical path alignment. Simultaneously, this step effectively prevents over-driving of the adjustment elements or excessive swaying of the mechanical structure, extending the lifespan of the beam adjustment unit. Furthermore, by using this peak point as a reset reference, it can be ensured that the two second adjustment elements are precisely reset to their optimal cooperative posture in this direction, thereby achieving local optimization of interference contrast in the second direction.

[0209] In some embodiments of this application, an automatic optical path alignment system is also provided. The system includes a light source, a beam adjustment module, an interferometer group, a signal conversion module, an interference contrast generation device, and a control module. The specific structure of the automatic optical path alignment system of this application can be referred to the description of any of the above embodiments, and will not be repeated here.

[0210] It is understood that the automatic optical path alignment system provided in this application embodiment can be applied to laser interferometers to achieve automated and precise adjustment of beam pointing and closed-loop control of optical path alignment, thereby improving the assembly efficiency, environmental adaptability, and long-term stability of the laser interferometer. Furthermore, this laser interferometer can be applied to semiconductor metrology equipment, lithography machines, precision displacement stages, vacuum environment measurement systems, or other precision instruments requiring high-precision displacement or attitude measurement, enabling high-precision real-time monitoring and feedback control of key process parameters (such as material surface morphology, air refractive index, precision displacement, three-dimensional attitude, etc.).

[0211] Although this application has been illustrated and described with reference to certain preferred embodiments thereof, those skilled in the art should understand that various changes in form and detail may be made thereto without departing from the spirit and scope of this application.

Claims

1. An automatic optical path alignment method for a laser interferometer, characterized in that, An automatic optical path alignment system is applied, the system comprising a light source, a beam adjustment module, an interferometer group, a signal conversion module, an interference contrast generation device, and a control module; the method includes: S1: The light source generates a dual-frequency beam and incident the dual-frequency beam onto the beam adjustment module. The dual-frequency beam includes a first frequency light and a second frequency light. S2: The beam adjustment module receives the dual-frequency beam and sends the dual-frequency beam to the interferometer group. The beam adjustment module includes m beam adjustment units, where m is an integer greater than or equal to 1. Each beam adjustment unit includes an optical element, a first adjustment element, and a second adjustment element. The parameter values ​​of the first adjustment element and the second adjustment element are used to determine the positions of the dual-frequency beam in the first direction and the second direction after passing through the optical element, respectively. The first direction is perpendicular to the second direction. S3: The interference mirror group causes the first frequency light and the second frequency light to form a reference light and a measurement light, respectively, and sends the reference light and the measurement light to the signal conversion module; S4: The signal conversion module converts the reference light and the measurement light into optical interference fringe electrical signals; S5: The interference contrast generating device receives the optical interference fringe electrical signal and generates the interference contrast value of the reference light and the measurement light; S6: The control module executes the scanning alignment process; The scanning alignment process includes m unit scanning alignment processes executed separately, where the kth unit scanning alignment process corresponds to the kth beam adjustment unit, and k = 1, 2, ..., m; The scanning alignment process for the kth unit includes: The parameter values ​​of the second adjustment element of the kth beam adjustment unit and the parameter values ​​of the remaining beam adjustment units are fixed. The parameter value of the first adjustment element of the kth beam adjustment unit is adjusted, and the interference contrast value generated by the interference contrast generation device is acquired in real time to form a first interference contrast value group. The parameter value of the first adjustment element of the kth beam adjustment unit is reset to the parameter value of the first adjustment element of the kth beam adjustment unit corresponding to the maximum interference contrast value in the first interference contrast value group. The parameter values ​​of the first adjustment element of the kth beam adjustment unit and the parameter values ​​of the remaining beam adjustment units are fixed. The parameter value of the second adjustment element of the kth beam adjustment unit is adjusted, and the interference contrast value generated by the interference contrast generation device is acquired in real time to form a second interference contrast value group. The parameter value of the second adjustment element of the kth beam adjustment unit is reset to the parameter value of the second adjustment element of the kth beam adjustment unit corresponding to the maximum interference contrast value in the second interference contrast value group.

2. The method according to claim 1, characterized in that, If m is greater than or equal to 2, then the following steps are also included: S7: The control module acquires the interference contrast value generated by the interference contrast generating device in real time. If the interference contrast value is greater than or equal to the first preset threshold, it determines that the optical path is automatically aligned; otherwise, it executes S8. S8: The control module executes the joint debugging and alignment process, and ends the automatic optical path alignment; The joint alignment process includes performing a first direction alignment process and a second direction alignment process on a preset beam adjustment unit group, wherein the preset beam adjustment unit group includes at least two beam adjustment units. The first alignment process includes: With the parameter values ​​of each second adjustment element in the preset beam adjustment unit group and the parameter values ​​of the remaining beam adjustment units in the beam adjustment module fixed, the parameter values ​​of each first adjustment element in the preset beam adjustment unit group are combined and adjusted to obtain the interference contrast value generated by the interference contrast generation device in real time, so as to form a third interference contrast value group. The parameter values ​​of each first adjustment element in the preset beam adjustment unit group are then reset to the parameter values ​​of each first adjustment element in the preset beam adjustment unit group corresponding to the maximum interference contrast value in the third interference contrast value group, and the process is switched to the second direction alignment process. The second-direction alignment process includes: With the parameter values ​​of each first adjustment element in the preset beam adjustment unit group and the parameter values ​​of the remaining beam adjustment units in the beam adjustment module fixed, the parameter values ​​of each second adjustment element in the preset beam adjustment unit group are combined and adjusted to obtain the interference contrast value generated by the interference contrast generation device in real time, so as to form a fourth interference contrast value group, and the parameter values ​​of each second adjustment element in the preset beam adjustment unit group are reset to the parameter values ​​of each second adjustment element in the preset beam adjustment unit group corresponding to the maximum interference contrast value in the fourth interference contrast value group.

3. The method according to claim 2, characterized in that, The preset beam adjustment unit group includes the two beam adjustment units closest to the interference contrast generating device; each beam adjustment unit in the preset beam adjustment unit group includes: a first adjustment element and a second adjustment element.

4. The method according to claim 3, characterized in that, In the nth beam adjustment unit, the current parameter value and parameter value step size of the first adjustment element are respectively and n = 1, 2, ..., m; The first orientation alignment process further includes: S811: The control module executes the first coordination factor identification process, which includes: Record the current parameter values ​​of the two first adjustment elements of the preset beam adjustment unit group. and and the current interference contrast value generated by the interference contrast generation device. ; and respectively set the parameter value step size of the two first adjustment elements of the preset beam adjustment unit group. ; With the parameter values ​​of each of the second adjustment elements in the preset beam adjustment unit group and the parameter values ​​of the remaining beam adjustment units in the beam adjustment module fixed, the parameter values ​​of the two first adjustment elements in the preset beam adjustment unit group are respectively adjusted to ( ),in,( , The first coordination factor is defined as (+1,+1), which includes the following combinations: (+1,-1), (+1,-1), (-1,+1), and (-1,-1). The interference contrast values ​​generated by the interference contrast generation device corresponding to each combination of the first coordination factor are acquired in real time. , , and ,in, , , , and Forming the fifth set of interference contrast values; If the maximum value in the fifth interference contrast value group Then The corresponding first joint modulation factor is used as the first target joint modulation factor. ), then proceed to S812; if The parameter values ​​of the two first adjustment elements of the preset beam adjustment unit group are reset to ( , ), thus ending the first direction alignment process; S812: The control module executes a first optimization process, the first optimization process including: The parameter values ​​of the two first adjustment elements of the preset beam adjustment unit group are combined and adjusted to ( ),in, The number of steps, and in During the process of incrementing by 1 sequentially, each step is acquired and recorded in real time. The parameter value combination corresponds to the interference contrast value generated by the interference contrast generating device. This is done to form a sixth interference contrast value group, and the parameter values ​​of each of the first adjustment elements in the preset beam adjustment unit group are reset to the maximum interference contrast value in the sixth interference contrast value group. The parameter values ​​of each of the first adjustment elements in the corresponding preset beam adjustment unit group; S813: Switch to the second direction alignment process.

5. The method according to claim 4, characterized in that, In step S812, the maximum value of the interference contrast value in the sixth interference contrast value group is obtained. The method is as follows: when At that time, Steps No more additions will be made.

6. The method according to claim 4, characterized in that, In the nth beam adjustment unit, the current parameter value and parameter value step size of the second adjustment element are respectively and ; The second-direction alignment process further includes: S821: The control module executes the second integration factor identification process, which includes: Record the current parameter values ​​of the two second adjustment elements of the preset beam adjustment unit group. and and the current interference contrast value generated by the interference contrast generation device. ; and respectively set the parameter value step size of the two second adjustment elements of the preset beam adjustment unit group. ; With the parameter values ​​of each of the first adjustment elements in the preset beam adjustment unit group and the parameter values ​​of the remaining beam adjustment units in the beam adjustment module fixed, the parameter values ​​of the two second adjustment elements in the preset beam adjustment unit group are respectively adjusted to ( ),in,( The second coordination factor is defined as (+1,+1), which includes the following combinations: (+1,-1), (+1,-1), (-1,+1), and (-1,-1). The interference contrast values ​​generated by the interference contrast generation device corresponding to each combination of the second coordination factor are acquired in real time. , , and ,in, , , , and The seventh set of interference contrast values ​​is formed; If the maximum value in the seventh interference contrast value group Then The corresponding second coordination factor is used as the second target coordination factor. , ), then proceed to S822; if The parameter values ​​of the two second adjustment elements of the preset beam adjustment unit group are reset to ( , ), thus ending the second direction alignment process; S822: The control module executes a second optimization process, the second optimization process including: The parameter values ​​of the two second adjustment elements of the preset beam adjustment unit are combined and adjusted to ( ),in, The number of steps, and in During the process of incrementing by 1 sequentially, each step is acquired and recorded in real time. The interference contrast generated by the interference contrast generating device corresponds to the combination of the parameter values. This forms the eighth interference contrast value group, and resets the parameter values ​​of each of the second adjustment elements in the preset beam adjustment unit group to the maximum interference contrast value in the eighth interference contrast value group. The parameter values ​​of each of the second adjustment elements in the corresponding preset beam adjustment unit group.

7. The method according to claim 6, characterized in that, In step S822, the maximum value of the interference contrast in the eighth interference contrast value group is obtained. The method is as follows: when At that time, Steps No more additions will be made.

8. The method according to claim 1, characterized in that, The polarization directions of the first frequency light and the second frequency light are orthogonal. The interference contrast value is positively correlated with the spatial overlap between the reference light and the measurement light; The formula for calculating the interference contrast value is as follows: ,in, The maximum value of the electrical signal of the optical interference fringes. This is the minimum value of the electrical signal of the optical interference fringes.

9. The method according to any one of claims 1 to 8, characterized in that, The beam adjustment unit is a piezoelectric reflector, the first adjustment element is a first piezoelectric screw, the second adjustment element is a second piezoelectric screw, and the optical element is a reflector; The first piezoelectric screw and the second piezoelectric screw determine the position of the dual-frequency beam in the first direction and the second direction after passing through the reflector by controlling the tilt angle of the reflector; The parameter value of the first adjusting element is the amount of extension and retraction displacement of the first piezoelectric screw relative to the initial length, and the parameter value of the second adjusting element is the amount of extension and retraction displacement of the second piezoelectric screw relative to the initial length, wherein the initial length is the natural length of the piezoelectric screw when it is not energized.

10. The method according to any one of claims 1 to 8, characterized in that, The signal conversion module includes: an interference unit and a photoelectric conversion unit; Step S4 further includes: S41: The interference unit receives the reference light and the measurement light, interferes with the reference light and the measurement light to generate an optical interference light field, and sends the optical interference light field to the photoelectric conversion unit; S42: The photoelectric conversion unit converts the optical interference light field into the optical interference fringe electrical signal and sends it to the interference contrast generation device.

11. An automatic optical path alignment system, characterized in that, It includes a light source, a beam adjustment module, an interferometer group, a signal conversion module, an interference contrast generation device, and a control module; among which: The light source is used to generate a dual-frequency beam and to incident the dual-frequency beam onto the beam adjustment module. The dual-frequency beam includes a first frequency light and a second frequency light. The beam adjustment module is used to receive the dual-frequency beam and send the dual-frequency beam to the interferometer group. The beam adjustment module includes m beam adjustment units, where m is an integer greater than or equal to 1. Each beam adjustment unit includes an optical element, a first adjustment element, and a second adjustment element. The parameter values ​​of the first adjustment element and the second adjustment element are used to determine the positions of the dual-frequency beam in a first direction and a second direction after passing through the optical element, respectively. The first direction is perpendicular to the second direction. The interferometer array is used to make the first frequency light and the second frequency light form a reference light and a measurement light, respectively, and to send the reference light and the measurement light to the signal conversion module; The signal conversion module is used to convert the reference light and the measurement light into optical interference fringe electrical signals; The interference contrast generating device is used to receive the optical interference fringe electrical signal and generate the interference contrast value of the reference light and the measurement light; The control module is used to execute the scanning alignment process; The scanning alignment process includes m unit scanning alignment processes executed separately, where the kth unit scanning alignment process corresponds to the kth beam adjustment unit, and k = 1, 2, ..., m; The scanning alignment process for the kth unit includes: The parameter values ​​of the second adjustment element of the kth beam adjustment unit and the parameter values ​​of the remaining beam adjustment units are fixed. The parameter value of the first adjustment element of the kth beam adjustment unit is adjusted, and the interference contrast value generated by the interference contrast generation device is acquired in real time to form a first interference contrast value group. The parameter value of the first adjustment element of the kth beam adjustment unit is reset to the parameter value of the first adjustment element of the kth beam adjustment unit corresponding to the maximum interference contrast value in the first interference contrast value group. The parameter values ​​of the first adjustment element of the kth beam adjustment unit and the parameter values ​​of the remaining beam adjustment units are fixed. The parameter value of the second adjustment element of the kth beam adjustment unit is adjusted, and the interference contrast value generated by the interference contrast generation device is acquired in real time to form a second interference contrast value group. The parameter value of the second adjustment element of the kth beam adjustment unit is reset to the parameter value of the second adjustment element of the kth beam adjustment unit corresponding to the maximum interference contrast value in the second interference contrast value group.

12. The system according to claim 11, characterized in that, The beam adjustment unit is a piezoelectric reflector, the first adjustment element is a first piezoelectric screw, the second adjustment element is a second piezoelectric screw, and the optical element is a reflector; The first piezoelectric screw and the second piezoelectric screw determine the position of the dual-frequency beam in the first direction and the second direction after passing through the reflector by controlling the tilt angle of the reflector; The parameter value of the first adjusting element is the amount of extension and retraction displacement of the first piezoelectric screw relative to the initial length, and the parameter value of the second adjusting element is the amount of extension and retraction displacement of the second piezoelectric screw relative to the initial length, wherein the initial length is the natural length of the piezoelectric screw when it is not energized.

13. The system according to claim 11, characterized in that, The polarization directions of the first frequency light and the second frequency light are orthogonal; the signal conversion module includes an interference unit and a photoelectric conversion unit; wherein... The interference unit is used to receive the reference light and the measurement light, and interfere the reference light and the measurement light to generate an optical interference light field; the photoelectric conversion unit is used to convert the optical interference light field into the optical interference fringe electrical signal, and send it to the interference contrast generating device.

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