Multi-mode laser interferometry signal processing system

Abstract

The application provides a multi-mode laser interference signal processing system, which comprises a laser signal transceiver, a single-mode optical fiber and a phase card; the laser signal transceiver is used for receiving a multi-mode laser interference signal output by an interferometer; the laser signal transceiver is also used for converting the multi-mode laser interference signal into a single-mode laser communication signal; the single-mode optical fiber has a first end and a second end; the first end is connected to the laser signal transceiver, and the second end is connected to the phase card; the single-mode optical fiber is used for transmitting the single-mode laser communication signal to the phase card; and the phase card is used for calculating a phase change amount contained in the single-mode laser communication signal into a displacement change amount. The application effectively avoids the problem that the displacement measurement result has an error due to the phase error caused by the disturbance of the optical fiber, and obviously improves the accuracy of the displacement measurement result.

Description

Technical Field

[0001] This invention relates to the field of grating measurement technology, and more specifically, to a multi-mode laser interferometric signal processing system. Background Technology

[0002] High-precision displacement measurement technology is the foundation of modern ultra-precision machining technology, directly determining the processing accuracy and manufacturing level of products, and is widely used in fields such as semiconductor device manufacturing. Grating interferometers and laser interferometers are commonly used for high-precision displacement measurement. The multi-mode laser interference signal output by a grating interferometer or laser interferometer contains phase changes. These phase changes are the time fraction of the angular frequency change caused by the Doppler shift phenomenon during the interferometer's operation. Simultaneously, the Doppler shift contains information about the moving velocity of the target or the interferometer. Related technologies can establish a linear relationship between phase and displacement by integrating the Doppler shift results through a phase signal processing system, and by subdividing and counting the phase values, displacement measurement can be achieved.

[0003] However, related technologies require the use of multimode optical fibers to transmit the multimode laser interference signals output by the interferometer over long distances to a digital signal processing device. The displacement measurement results are then obtained by processing these signals. However, during the long-distance transmission of the multimode laser interference signals, due to the characteristics of multimode optical fibers, the transmission paths of different modes of laser signals (pulses) within the multimode fiber are inconsistent when disturbances occur. Laser signals propagating along the axis travel the fastest, while those traveling at the total internal reflection angle travel the slowest. This results in differences in the arrival times of simultaneously emitted laser signals of different modes at the digital signal processing device; this phenomenon is called modal dispersion. Modal dispersion reflects the broadening of laser pulses propagating along the multimode fiber, leading to pulse overlap and intersymbol interference (ISI), thus causing transmission errors and signal distortion. These errors are called fiber perturbation phase errors, ultimately resulting in significant errors in the displacement measurement results output by the digital signal processing device. Therefore, how to effectively avoid errors in displacement measurement results caused by fiber perturbation phase errors has become a pressing technical problem and a key research focus for those skilled in the art. Summary of the Invention

[0004] To address the problem of displacement measurement errors caused by fiber optic perturbation phase errors in existing technologies, this invention provides a multi-mode laser interferometry signal processing system to reduce or even avoid displacement measurement errors caused by fiber optic perturbation phase errors.

[0005] To achieve the above-mentioned technical objectives, the present invention provides a multi-mode laser interferometric signal processing system, including a laser signal transceiver, a single-mode optical fiber, and a phase card; the laser signal transceiver is used to receive multi-mode laser interferometric signals output by an interferometer; the laser signal transceiver is also used to convert the multi-mode laser interferometric signals into single-mode laser communication signals; the single-mode optical fiber has a first end and a second end; the first end is connected to the laser signal transceiver, and the second end is connected to the phase card; the single-mode optical fiber is used to transmit the single-mode laser communication signals to the phase card; the phase card is used to calculate the phase change contained in the single-mode laser communication signals as a displacement change.

[0006] Based on the above technical solution, this invention first converts the multi-mode laser interference signal output by the interferometer into a single-mode laser communication signal. Then, the single-mode laser communication signal is transmitted from the laser signal transceiver to the phase card via a single-mode optical fiber for processing. It can be seen that the multi-mode laser interference signal processing system provided by this invention transmits only one mode of laser signal through a single-mode optical fiber, effectively avoiding the problem of mode dispersion, thereby avoiding the problem of inter-symbol interference. This significantly improves the quality of the laser signal received by the phase card and effectively avoids the problem of displacement measurement errors caused by fiber perturbation phase errors. Therefore, this invention can significantly improve the accuracy of displacement measurement results.

[0007] In one or more embodiments of the present invention, the laser signal transceiver includes a first photoelectric conversion device, a power amplification device, and an electro-optical conversion device connected in sequence; the first photoelectric conversion device is used to receive the multi-mode laser interference signal output by the interferometer and to convert the multi-mode laser interference signal into a first current signal; the first photoelectric conversion device is also used to transmit the first current signal to the power amplification device; the power amplification device is used to amplify the first current signal to obtain a second current signal; the electro-optical conversion device is used to convert the second current signal into the single-mode laser communication signal.

[0008] Based on the improved technical solution described above, this embodiment can also perform photoelectric conversion, power amplification, and electro-optical conversion on multi-mode laser interference signals. Thus, while converting multi-mode laser interference signals into single-mode laser communication signals, the power amplification ensures that the single-mode laser communication signals have sufficient intensity, effectively avoiding problems such as the weakening of laser signal intensity during the conversion of multi-mode laser interference signals into single-mode laser communication signals.

[0009] In one or more embodiments of the present invention, the phase card includes a second photoelectric conversion device, an analog-to-digital conversion device, and a digital signal processing device connected in sequence; the second photoelectric conversion device is used to receive the single-mode laser communication signal and to convert the single-mode laser communication signal into an analog signal; the analog-to-digital conversion device is used to convert the analog signal into a digital signal; the digital signal processing device is used to perform calculations on the digital signal to calculate the phase change amount contained in the single-mode laser communication signal into a displacement change amount.

[0010] Based on the improved technical solution described above, this embodiment can also perform photoelectric conversion, analog-to-digital conversion, and calculation processing on single-mode laser communication signals. By converting single-mode laser communication signals into digital signals for processing, the accuracy and reliability of displacement change calculation results can be guaranteed.

[0011] In one or more embodiments of the present invention, the digital signal processing device includes a mixing module, a filtering module, a phase calculation module, an unwinding module, and a phase conversion module connected in sequence; the mixing module is used to perform mixing processing on the digital signal; the filtering module is used to perform filtering processing on the digital signal after mixing processing; the phase calculation module is used to perform phase calculation processing on the digital signal after filtering processing to obtain the phase value at the current moment; the unwinding module is used to perform unwinding processing on the phase value at the current moment to obtain the phase change amount; and the phase conversion module is used to convert the phase change amount into the displacement change amount.

[0012] Based on the improved technical solution described above, the embodiments of the present invention can effectively convert the phase change value caused by the Doppler frequency shift containing displacement information into the displacement change value by performing frequency mixing, filtering, phase calculation, unwinding and conversion processing on the digital signal, which greatly improves the measurement accuracy.

[0013] In one or more embodiments of the present invention, the phase card further includes a voltage amplification device disposed between the second photoelectric conversion device and the analog-to-digital conversion device; the voltage amplification device is used to amplify the analog signal; the analog-to-digital conversion device is used to convert the analog signal after voltage amplification into a digital signal.

[0014] Based on the improved technical solution described above, this embodiment also amplifies the analog signal before performing analog-to-digital conversion, effectively improving the strength of the analog signal to avoid problems such as insufficient analog signal strength obtained by the second photoelectric conversion device through conversion of single-mode laser communication signal.

[0015] In one or more embodiments of the present invention, the laser signal transceiver further includes a filtering device and a noise reduction device sequentially disposed between the power amplification device and the electro-optical conversion device; the filtering device is used to filter the second current signal; the noise reduction device is used to reduce the noise of the second current signal after the filtering process; and the electro-optical conversion device is used to convert the second current signal after the noise reduction process into the single-mode laser communication signal.

[0016] Based on the improved technical solution described above, this embodiment can filter and denoise the second current signal before converting it into a single-mode laser communication signal, thereby removing noise from the second current signal and retaining the useful signal in the second current signal. This enables the conversion of the useful signal in the second current signal into a single-mode laser communication signal, ensuring the accuracy of the signal. It can be seen that the signal quality of the single-mode laser communication signal to be transmitted in this embodiment is better.

[0017] In one or more embodiments of the present invention, the number of multi-mode laser interference signals is multiple, and the multi-mode laser interference signals include multiple laser signals with the same polarization direction but different incident angles. The present invention can process multi-mode laser interference signals simultaneously with high processing efficiency.

[0018] In one or more embodiments of the present invention, the single-mode laser communication signal and the multi-mode laser interference signal have the same frequency characteristics. The present invention, by using single-mode laser communication information with the same frequency characteristics as the multi-mode laser interference signal, can better reflect the laser signal output by the interferometer. Since the single-mode laser communication signal and the multi-mode laser interference signal in this embodiment have the same frequency characteristics, the present invention also helps to reduce the computational load during the solution process.

[0019] In one or more embodiments of the present invention, the distance between the interferometer and the laser signal transceiver is less than the length of the single-mode optical fiber. The present invention enables long-distance transmission of single-mode laser communication signals via single-mode optical fiber, ensuring the stability of the laser signal during long-distance transmission.

[0020] In one or more embodiments of the present invention, the interferometer is a grating interferometer mounted on the workpiece stage of a lithography machine. Compared with conventional technology, the present invention provides a signal processing system for a grating interferometer on a lithography machine workpiece stage, achieving ultra-precision displacement measurement.

[0021] The beneficial effects of this invention include: First, the multi-mode laser interference signal output by the interferometer is converted into a single-mode laser communication signal using a laser signal transceiver. Then, the single-mode laser communication signal is transmitted from the laser signal transceiver to the phase card via a single-mode fiber for processing. It is evident that the multi-mode laser interference signal processing system in this invention transmits only one mode of laser signal via a single-mode fiber. Single-mode fiber has advantages such as strong anti-interference capability and suitability for long-distance laser signal transmission. Therefore, this invention effectively avoids the problem of mode dispersion, thereby avoiding inter-symbol interference. Compared to conventional methods of transmitting laser signals via multi-mode fiber, this invention significantly improves the quality of the laser signal and effectively avoids errors in displacement measurement results caused by fiber perturbation phase errors. Therefore, this invention significantly improves the measurement accuracy and precision of displacement measurement results. Attached Figure Description

[0022] Figure 1 A schematic diagram of the structure of a multimode laser interferometric signal processing system according to one or more embodiments of the present invention is shown.

[0023] Figure 2 A schematic diagram of the structure of a laser signal transceiver according to one or more embodiments of the present invention is shown.

[0024] Figure 3 A schematic diagram of the phase card structure composition in one or more embodiments of the present invention is shown.

[0025] Figure 4 A detailed structural schematic diagram of a multimode laser interferometric signal processing system according to one or more embodiments of the present invention is shown.

[0026] Figure 5 A schematic diagram of the application scenario layout of the multi-mode laser interferometric signal processing system according to one or more embodiments of the present invention is shown.

[0027] In the picture,

[0028] 100. Laser signal transceiver; 101. First photoelectric conversion device; 102. Power amplifier device; 103. Electro-optical conversion device.

[0029] 200. Single-mode fiber.

[0030] 300. Phase card; 301. Second photoelectric conversion device; 302. Analog-to-digital conversion device; 303. Digital signal processing device.

[0031] 3030, Mixing module; 3031, Filtering module; 3032, Phase calculation module; 3033, Unwinding module.

[0032] 400, First power supply; 500, Second power supply; 600, Workpiece stage; 700, Chassis. Detailed Implementation

[0033] The multi-mode laser interferometry signal processing system of the present invention will be explained and described in detail below with reference to the accompanying drawings.

[0034] like Figure 1 As shown, one or more embodiments of the present invention can provide a multimode laser interferometric signal processing system, which may include, but is not limited to, a laser signal transceiver 100, a single-mode optical fiber 200, and a phase card 300.

[0035] The laser signal transceiver 100 is used to receive multi-mode laser interference signals output by the interferometer; the laser signal transceiver 100 is also used to convert multi-mode laser interference signals into single-mode laser communication signals; it can be seen that the laser signal transceiver 100 is located at the beginning of the entire signal processing system.

[0036] like Figure 2 As shown, the laser signal transceiver 100 provided in at least one embodiment of the present invention has a modular structure. Specifically, the laser signal transceiver 100 includes a first photoelectric conversion device 101, a power amplifier device 102, and an electro-optical conversion device 103 connected in sequence. That is, the input of the power amplifier device 102 is connected to the first photoelectric conversion device 101, and the output of the power amplifier device 102 is connected to the electro-optical conversion device 103. In this embodiment, the first photoelectric conversion device 101 is specifically a receiver optical subassembly (ROSA), the power amplifier device 102 is specifically a power amplifier (PA), and the electro-optical conversion device 103 is specifically a transmitter optical subassembly (TOSA).

[0037] The first photoelectric conversion device 101 is used to receive the multi-mode laser interference signal output by the interferometer, and to convert the multi-mode laser interference signal into a first current signal. The first photoelectric conversion device 101 serves as the laser signal input terminal; the first photoelectric conversion device 101 is also used to transmit the first current signal to the power amplifier device 102. Combined with... Figure 2As shown, the first photoelectric conversion device 101 in this embodiment is a Receiver Optical Subassembly (ROSA). The core device of the ROSA in this embodiment is a PIN photodiode or an avalanche photodiode. The photodiode or avalanche photodiode used can receive the laser interference signal with a preset wavelength emitted by the interferometer, that is, the frequency response range of the photodiode or avalanche photodiode used includes the frequency range of the laser interference signal. The main function of the ROSA core device is to convert the received optical signal into an electrical signal, which is an analog signal. Among them, the multi-mode laser interference signal represents multiple modes of laser signal.

[0038] In an optional embodiment of the present invention, there are multiple multi-mode laser interference signals, and each multi-mode laser interference signal includes multiple laser signals with the same polarization direction but different incident angles. That is, the polarization direction of the multiple laser signals may be the same, but the incident angles may be different.

[0039] Combination Figure 2 As shown, the multi-mode laser interference signal output by the interferometer in this embodiment of the invention may include two sets of laser signals with the same frequency but different phases. Each set of laser signals is a multi-mode laser interference signal, which includes a reference light signal and a measurement light signal.

[0040] The power amplifier 102 is used to amplify the first current signal to obtain the second current signal. The power amplifier 102 is a power amplifier (PA), whose main function is to amplify the signal, thereby amplifying the power of the preamplifier circuit to drive the postamplifier circuit or load.

[0041] The electro-optical converter 103 is used to convert the second current signal into a single-mode laser communication signal, which is also a type of laser signal. Therefore, the electro-optical converter 103 serves as the laser signal output terminal. The electro-optical converter 103 is a Transmitter Optical Subassembly (TOSA). In this embodiment, the core device of the TOSA is a semiconductor light-emitting diode or a laser diode. The main function of the TOSA is to convert the electrical signal into a single-mode laser communication signal and to emit the single-mode laser communication signal. In this embodiment, the wavelength of the laser signal output by the semiconductor light-emitting diode or laser diode corresponds to the wavelength of the response signal of the second photoelectric conversion device 301 in the phase card 300 described later.

[0042] In summary, in this embodiment, the multi-mode laser interference signal output by the grating interferometer is used to form a laser signal transceiver 100. The multi-mode laser interference signal first enters a first photoelectric conversion device 101. The photodiode in the first photoelectric conversion device 101 converts the optical signal (multi-mode laser interference signal) into a first current signal (analog signal). Before entering the electro-optical conversion device 103, the first current signal is amplified by a power amplifier device 102. This power amplification may include, but is not limited to, current amplification and / or voltage amplification. The power amplifier device 102 is used to increase the output power of the signal while ensuring that the signal is not distorted. Then, the amplified first current signal is restored to a laser signal by the electro-optical conversion device 103, thus obtaining a single-mode laser communication signal to be transmitted through a single-mode optical fiber.

[0043] In one or more embodiments of the present invention, the single-mode laser communication signal and the multi-mode laser interference signal have the same frequency characteristics.

[0044] In one or more preferred embodiments of the present invention, the laser signal transceiver 100 further includes a filtering device and a noise reduction device sequentially disposed between the power amplification device 102 and the electro-optical conversion device 103; wherein, the filtering device is used to filter the second current signal, the noise reduction device is used to reduce the noise of the filtered second current signal, and the electro-optical conversion device 103 is used to convert the noise-reduced second current signal into a single-mode laser communication signal.

[0045] The single-mode optical fiber 200 used in this invention is used to connect the laser signal transceiver 100 and the phase card 300 for long-distance transmission of laser signals. It is understood that the single-mode optical fiber 200 is a communication optical fiber used to transmit a single mode of optical signal.

[0046] The single-mode optical fiber 200 provided in this embodiment has a first end and a second end, i.e., the two ends of the single-mode optical fiber 200. The first end is connected to the laser signal transceiver 100, and the second end is connected to the phase card 300. The single-mode optical fiber 200 is used to transmit single-mode laser communication signals to the phase card 300. This single-mode optical fiber 200 has advantages such as strong anti-interference capability, and is suitable for transmitting single-mode laser communication signals from the laser signal transceiver 100 to the phase card 300. In at least one embodiment of the present invention, the distance between the interferometer and the laser signal transceiver 100 is less than the length of the single-mode optical fiber 200, thereby achieving the purpose of long-distance transmission of laser signals.

[0047] The phase card 300 can be used to convert the phase change contained in a single-mode laser communication signal into a displacement change. The purpose is to convert the phase change value of the laser signal into a displacement change value. It can be seen that the phase card 300 of the present invention is located at the end of the entire multi-mode laser interferometric signal processing system.

[0048] like Figure 3 As shown, the phase card 300 in at least one embodiment of the present invention includes a second photoelectric conversion device 301, an analog-to-digital conversion device 302, and a digital signal processing device 303 connected in sequence, and the second photoelectric conversion device 301, the analog-to-digital conversion device 302, and the digital signal processing device 303 can be integrated into one unit. Specifically, the second photoelectric conversion device 301 in this embodiment is a Receiver Optical Subassembly (ROSA). The core device of the ROSA in this embodiment is a PIN photodiode or an avalanche photodiode. The main function of the ROSA is to convert optical signals into electrical signals, which are analog signals. The analog-to-digital conversion device 302 can specifically be an analog-to-digital converter (A / D). On the hardware side, the analog-to-digital converter in this embodiment can be implemented through an ADC (Analog to Digital Converter) chip. The digital signal processing device 303 can specifically be an FPGA (Field Programmable Gate Array) digital signal processor used to process digital signals.

[0049] The second photoelectric conversion device 301 serves as the laser signal input terminal. The second photoelectric conversion device 301 is used to receive single-mode laser communication signals and to convert single-mode laser communication signals into analog signals.

[0050] The analog-to-digital converter 302 is used to convert analog signals into digital signals. In specific implementation, the analog-to-digital converter 302 in this embodiment is an ADC chip, and the sampling frequency of the ADC chip is greater than the frequency of the analog signal. The sampling bit width of the ADC chip in this embodiment can be determined according to the actual application scenario, so as to meet the accuracy requirements of the sampling signal and the electronic subdivision requirements of the digital signal processing device 303.

[0051] The digital signal processing device 303 receives the digital signal output by the analog-to-digital converter 302. The digital signal processing device 303 is used to perform calculations on the digital signal to convert the phase change contained in the single-mode laser communication signal into a displacement change.

[0052] Therefore, the interferometer of the present invention outputs a multi-mode laser interference signal. After the multi-mode laser interference signal is processed by the laser signal transceiver 100 through optical-to-electric conversion, power amplification, and electro-to-optical conversion, the multi-mode laser interference signal is converted into a single-mode laser communication signal. The single-mode laser communication signal is then transmitted over a long distance to the phase card 300 through the single-mode fiber 200. The phase card 300 performs photoelectric conversion and analog-to-digital conversion on the single-mode laser communication signal to obtain a digital signal. The digital signal is then sent to the FPGA digital signal processor for calculation to obtain the displacement result.

[0053] In at least one preferred embodiment of the present invention, the phase card 300 further includes a voltage amplification device disposed between the second photoelectric conversion device 301 and the analog-to-digital conversion device 302.

[0054] The voltage amplification device is used to amplify the voltage of the analog signal; the analog-to-digital converter 302 is used to convert the amplified analog signal into a digital signal. In a specific implementation, a current-to-voltage converter may also be included between the second photoelectric conversion device 301 and the voltage amplification device, thereby converting the current-form electrical signal output by the second photoelectric conversion device 301 into a voltage-form electrical signal for signal amplification.

[0055] Compared to existing technologies, the multi-mode laser interferometric signal processing system provided in this invention transmits single-mode laser communication signals over long distances via single-mode fiber. Leveraging the characteristic that single-mode fiber transmits only one mode of laser signal, the laser signal is unaffected by fiber disturbances and insensitive to fiber bending. This invention effectively avoids intermodal dispersion. Compared to multimode fiber transmission, the single-mode fiber transmission performance in this invention is significantly superior. Therefore, the multi-mode laser interferometric signal processing system provided by this invention can largely suppress fiber disturbance errors caused by laser signals during long-distance transmission, thereby meeting the requirements for higher precision measurements.

[0056] like Figure 3 As shown, the digital signal processing device 303 of the preferred embodiment of the present invention includes a mixer module 3030, a filter module 3031, a phase calculation module 3032, an unwinding module 3033, and a phase conversion module (not shown in the figure) connected in sequence.

[0057] The mixer module 3030 is used for mixing digital signals; the specific mixing process can be selected from relevant solutions as needed, for example... Figure 3 The mixing process shown is performed using a sine signal (sin) and / or a cosine signal (cos), and will not be described again in the embodiments of the present invention.

[0058] The filtering module 3031 is used to filter the digital signal after the mixing process;

[0059] The phase calculation module 3032 is used to perform phase calculation on the filtered digital signal to obtain the phase value at the current moment. In this embodiment, the phase calculation module 3032 is specifically a Cordic (coordinate rotation digital computer) calculation module. The Cordic calculation module can be used to convert the amplitude of the digital signal into the phase value of the signal, for example, to obtain a sawtooth waveform with a periodic change of -π to +π. The specific process of Cordic calculation can be selected from relevant schemes as needed, and will not be described in detail in this embodiment.

[0060] The unwinding module 3033 is used to unwind the phase value at the current moment to obtain the phase change. The unwinding module 3033 can be implemented using the unwrap module in the FPGA digital signal processor. For example, the unwrap module can accumulate all the obtained signal phase values ​​and use the accumulated result to represent the phase change. The specific working process of the unwrap module can be selected from relevant solutions as needed, and will not be elaborated further in this embodiment.

[0061] The phase conversion module is used to convert phase changes into displacement changes. This phase conversion module can be integrated into the unwinding module depending on the specific requirements; therefore, it is not shown in the figure in this embodiment.

[0062] In addition, the digital signal processing device 303 of this embodiment may also include a subtraction processing module disposed after the unwinding module 3033. The subtraction processing module can be used to eliminate the error in the measurement optical signal by subtracting the reference optical signal from the measurement optical signal.

[0063] like Figure 4 As shown, the multi-mode laser interferometric signal processing system provided in at least one embodiment of the present invention further includes, but is not limited to, a first power supply 400 and a second power supply 500. The first power supply 400 can be connected to the laser signal transceiver 100 and is used to supply power to the laser signal transceiver 100. The second power supply 500 can be connected to the phase card 300 and is used to supply power to the phase card 300.

[0064] like Figure 5 As shown, the multi-mode laser interferometric signal processing system provided by this invention can be applied to the field of lithography technology. The interferometer is specifically a grating interferometer (not shown in the figure) mounted on the workpiece stage 600 of the lithography machine. Of course, the interferometer in the optional embodiments of this invention can also be a laser interferometer. Figure 5A schematic diagram of the application scenario layout of a multi-mode laser interferometric signal processing system is provided. A laser transceiver 100 can be mounted on the workpiece stage 600 of a lithography machine. The multi-mode laser interference signal output from the grating interferometer is directly transmitted to the laser transceiver 100 after short-distance transmission. After processing, it is transmitted over a long distance to a phase card 300 via a single-mode optical fiber 200. The two ends of the single-mode optical fiber 200 are connected to the laser transceiver 100 and the phase card 300, respectively, and the single-mode optical fiber 200 is used for long-distance laser signal transmission. The phase card 300 is housed within a chassis 700, which is located away from the aforementioned workpiece stage 600 of the lithography machine. It can be seen that the multi-mode laser interferometric signal processing system provided by this invention effectively avoids the direct long-distance transmission of the multi-mode laser interference signal output from the grating interferometer. Instead, it converts the signal into a single-mode laser communication signal before long-distance transmission, thereby suppressing fiber optic disturbance errors caused by workpiece stage vibration and environmental interference during transmission, and thus improving displacement measurement accuracy.

[0065] In the description of this specification, the references to terms such as "this embodiment," "an embodiment," "some embodiments," "example," "specific example," or "some examples," etc., refer to specific features, structures, materials, or characteristics described in connection with that embodiment or example, which are included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0066] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this invention, "a plurality of" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0067] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," "counterclockwise," "axial," "radial," and "circumferential" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing this invention and simplifying the description, and are not intended to 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 this invention.

[0068] In this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," "linking," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; 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; they can refer to the internal communication of two components or the interaction between two components, unless otherwise explicitly limited. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0069] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and simple improvements made on the substantive content of the present invention should be included within the protection scope of the present invention.

Claims

1. A multi-mode laser interferometry signal processing system, characterized by, Includes laser signal transceivers, single-mode optical fibers, and phase cards; The laser signal transceiver is used to receive multi-mode laser interference signals output by the interferometer; the laser signal transceiver is also used to convert the multi-mode laser interference signals into single-mode laser communication signals. The single-mode optical fiber has a first end and a second end; the first end is connected to the laser signal transceiver, and the second end is connected to the phase card; the single-mode optical fiber is used to transmit the single-mode laser communication signal to the phase card. The phase card is used to convert the phase change contained in the single-mode laser communication signal into a displacement change. The laser signal transceiver includes a first photoelectric conversion device, a power amplifier device, and an electro-optical conversion device connected in sequence. The first photoelectric conversion device is used to receive the multi-mode laser interference signal output by the interferometer, and to convert the multi-mode laser interference signal into a first current signal; the first photoelectric conversion device is also used to transmit the first current signal to the power amplifier device. The power amplifier is used to amplify the first current signal to obtain a second current signal. The electro-optical conversion device is used to convert the second current signal into the single-mode laser communication signal.

2. The multi-mode laser interferometry signal processing system of claim 1, wherein, The phase card includes a second photoelectric conversion device, an analog-to-digital conversion device, and a digital signal processing device connected in sequence. The second photoelectric conversion device is used to receive the single-mode laser communication signal and to convert the single-mode laser communication signal into an analog signal; The analog-to-digital converter is used to convert the analog signal into a digital signal; The digital signal processing device is used to decode the digital signal to convert the phase change contained in the single-mode laser communication signal into a displacement change.

3. The multi-mode laser interferometry signal processing system of claim 2, wherein, The digital signal processing device includes a mixer module, a filter module, a phase calculation module, a dewinding module, and a phase conversion module connected in sequence. The mixing module is used to perform mixing processing on the digital signal; The filtering module is used to filter the digital signal after the mixing process. The phase calculation module is used to perform phase calculation on the filtered digital signal to obtain the phase value at the current moment. The unwinding module is used to unwind the phase value at the current moment to obtain the phase change amount; The phase conversion module is used to convert the phase change into the displacement change.

4. The multi-mode laser interferometry signal processing system of claim 2, wherein, The phase card also includes a voltage amplification device disposed between the second photoelectric conversion device and the analog-to-digital conversion device; The voltage amplification device is used to amplify the voltage of the analog signal; The analog-to-digital converter is used to convert the analog signal after voltage amplification into a digital signal.

5. The multi-mode laser interferometry signal processing system of claim 1, wherein, The laser signal transceiver also includes a filter and a noise reduction device arranged sequentially between the power amplifier and the electro-optical converter. The filtering device is used to filter the second current signal; The noise reduction device is used to reduce the noise of the second current signal after the filtering process. The electro-optical conversion device is configured to convert the second current signal after the noise reduction processing into the single-mode laser communication signal.

6. The multi-mode laser interferometry signal processing system of claim 1, wherein, The multi-mode laser interference signal includes multiple laser signals with consistent polarization directions and inconsistent incident angles.

7. The multi-mode laser interferometry signal processing system of claim 1, wherein, The single-mode laser communication signal has the same frequency characteristics as the multi-mode laser interference signal.

8. The multi-mode laser interferometry signal processing system of claim 1, wherein, The distance between the interferometer and the laser transceiver is less than the length of a single-mode optical fiber.

9. The multi-mode laser interferometry signal processing system of any of claims 1 to 8, wherein, The interferometer is a grating interferometer arranged on a workpiece table of a lithography machine.

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