Calibration method and system for p-polarization state and s-polarization state transmittance in focused beam measurement system

Abstract

This invention discloses a method and system for calibrating the transmittance of P-polarized and S-polarized states in a clustered focal spot measurement system. This addresses the technical problem in existing technologies where inconsistencies in the transmittance of P-polarized and S-polarized states in the optical path of the clustered focal spot measurement lead to significant errors in the final measurement results. This invention first uniformly emits P-polarized light at two locations, then uniformly emits S-polarized light. Next, it measures the power of the corresponding polarization states at four different locations, thereby obtaining the transmittance of each polarization state and completing the calibration of the P-polarized and S-polarized state transmittance in the measurement system. The calibration results of this invention can compensate for the differences in transmittance between P and S polarization states, achieving accurate measurement of the clustered focal spot and enabling accurate determination of the true morphology of the clustered focal spot in high-power laser physics experiments.

Description

Technical Field

[0001] This invention relates to a method and system for calibrating transmittance under different optical polarization states, specifically to a method and system for calibrating transmittance under P-polarization and S-polarization states in a cluster focal spot measurement system. Background Technology

[0002] In the NIF laser device, the terminal optical components are designed as a 2×2 arrangement of four beams. After the beams are focused to the focal point, the spot at the focal point is a combined spot of the four laser beams. The optical elements in the beam cluster are independent of each other, and the beams propagate independently in space. Furthermore, the four laser beams contain two polarization states: P-polarization and S-polarization.

[0003] Chinese patent CN111912354 B discloses a method and system for measuring high-power laser beam far-field combined focal spot. For example... Figure 1 As shown, the measurement system of this invention includes multiple absorbers (15), a sampling mirror group, a collimating negative lens group (14), a first attenuator group, a magnifying lens group, a second attenuator group, and a CCD; the sampling mirror group includes sampling mirror II and sampling mirror I, which are arranged sequentially along the optical path of the measured focal spot and have light-passing holes in their centers respectively; sampling mirror II and sampling mirror I are both parabolic mirrors, and their concave surfaces face each other; the collimating negative lens group is used to reduce and collimate the sampled beam; the first attenuator group includes at least two attenuators, and the angle between the normal of each attenuator and the beam is θ, 10° < θ < 20°; the magnifying lens group is used to magnify the attenuated beam; the second attenuator group includes a wheel attenuator and a fixed attenuator (13); the CCD is used to acquire the image of the magnified beam; the position of the measured focal spot in the focal spot measurement system is the position of the target point (11). The optical elements included in the measurement system of this invention have different transmittance or reflectance for P-polarized and S-polarized states. In particular, the difference in transmittance or reflectance between P-polarized and S-polarized states is even greater for the uncoated sampling element and the attenuation plate placed at an angle to the optical axis. The overall cumulative difference between the various optical elements is not negligible.

[0004] In summary, the difference in transmittance of different polarization states in the clustered focal spot measurement system will lead to differences in the energy distribution of the clustered focal spot at the image plane, thus resulting in differences in the true morphology of the clustered focal spot and causing a large error in the measurement results. Therefore, it is necessary to calibrate the transmittance of the P-polarization state and the S-polarization state in the clustered focal spot measurement system in order to compensate for this transmittance difference and achieve the goal of accurately measuring the clustered focal spot. Summary of the Invention

[0005] The purpose of this invention is to solve the technical problem in the prior art that the measurement result of the final clustered focal spot is greatly erroneous due to the inconsistency of the transmittance of the P-polarization state and the S-polarization state in the optical path of the clustered focal spot measurement. The invention provides a method and system for calibrating the transmittance of the P-polarization state and the S-polarization state in the clustered focal spot measurement system.

[0006] The method for calibrating transmittance of P-polarization and S-polarization states in a cluster focal spot measurement system is unique in that...

[0007] Step 1: Focus the first P-polarized laser at the target position and dock it with the first section of the measurement system from the target position to the attenuator on the left side in the cluster focal spot measurement system.

[0008] Step 2: Simultaneously measure the light spot at position A in the parallel beam segment of the first P-polarized laser and the light spot at position B between the target point and the absorber on the left side of the focused spot measurement system. The power of the light spot at position A is denoted as W. 11 The power of the light spot at position B is denoted as W2;

[0009] Step 3: Simultaneously measure the light spot at position A and the light spot at position C, located between the collimating negative lens group and the attenuator on the left side of the cluster focal spot measurement system. The power at position A is recorded as W. 12 The power at position C is denoted as W. 31 ;

[0010] Step 4: Remove the first P-polarized laser from the first measurement system, and dock the second P-polarized laser at position C with the second measurement system after the attenuator on the left and the attenuator is fixed.

[0011] Step 5: Simultaneously measure the light spot at position C and the light spot at position D on the output optical path of the second P-polarized laser, and obtain the power at position C, denoted as W. 32 The power at position D is denoted as W. 41 ;

[0012] Step 6: Simultaneously measure the beam spot at position E and position D, the convergence point of the beam located behind the fixed attenuator in the beam convergence measurement system. Record the power at position E as W5 and the power at position D as W. 42 ;

[0013] Step 7: Calculate the transmittance T of the first measurement system. Px1 =(W 31 ×W 11 ) / (W2×W 12 The transmittance T of the second measurement system Px2 =(W5×W 41 ) / (W 32 ×W42 );

[0014] Step 8: Calculate the P-polarization state transmittance coefficient of the cluster focal spot measurement system:

[0015] T p =T Px1 ×T Px2 ;

[0016] Step 9: Replace the first P-polarized laser and the second P-polarized laser with the first S-polarized laser and the second S-polarized laser, and repeat steps 1-8 above to obtain the S-polarized transmittance coefficient T of the cluster focal spot measurement system. S =T Sx1 ×T Sx2 .

[0017] Furthermore, the first P-polarized laser in step 1 or the first S-polarized laser in step 9 is emitted by the first light source module;

[0018] The first light source module is located to the left of the target point;

[0019] The first light source module includes a first standard light source, a first aperture stop, and a converging objective lens;

[0020] The first aperture and the converging objective are arranged sequentially along the outgoing light path of the first standard light source, and the converging objective focuses the outgoing light from the first standard light source onto the target point.

[0021] Position A is located between the first aperture stop and the converging objective lens.

[0022] Furthermore, step 2 is implemented in the following manner:

[0023] The first measurement module is connected to the optical path at position A, and the second measurement module is connected to the optical path at position B. The first measurement module scans according to the light spot distribution at position A, and the second measurement module scans according to the light spot distribution at position B, and the light spot power at positions A and B is measured simultaneously.

[0024] After the measurement is completed, remove the second measurement module at position B from the optical path.

[0025] Furthermore, step 3 is implemented in the following manner:

[0026] The third measurement module is connected to the optical path at position C. While the first measurement module is performing measurement, the third measurement module scans according to the light spot distribution at position C and simultaneously measures the light spot power at positions A and C.

[0027] After the measurement is completed, remove the first and third measurement modules from the optical path.

[0028] Furthermore, the second P-polarized laser in step 4 or the second S-polarized laser in step 9 is emitted by the second light source module;

[0029] The second light source module is located below position C;

[0030] The second light source module includes a second standard light source, a second aperture, a first reflector, and a second reflector;

[0031] The second aperture and the first reflector are arranged sequentially along the direction of the outgoing light path of the second standard light source;

[0032] The angle between the incident ray and the reflected ray of the first reflector is a right angle;

[0033] The second reflector is located on the reflected light path of the first reflector;

[0034] The angle between the incident ray and the reflected ray of the second reflector is a right angle;

[0035] The position D is located between the second aperture and the first reflector.

[0036] Furthermore, step 5 is implemented in the following manner:

[0037] The third measurement module is connected to the optical path at position C, and the fourth measurement module is connected to the optical path at position D. The third measurement module scans according to the light spot distribution at position C, and the fourth measurement module scans according to the light spot distribution at position D, simultaneously measuring the light spot power at positions C and D.

[0038] After the measurement is completed, remove the third measurement module at position C from the optical path.

[0039] Furthermore, step 6 is implemented in the following manner:

[0040] The power meter at position E receives the beam converged at position E, and the fourth measurement module scans according to the beam distribution trajectory at position D, simultaneously measuring the beam power at positions D and E.

[0041] After the measurement is completed, remove the fourth measurement module at position D from the optical path.

[0042] Furthermore, the first measurement module and the fourth measurement module have the same structure, both including a compensation mirror, a beam splitter, a first lens and a first power meter arranged sequentially along the optical path;

[0043] The angle between the incident and reflected rays of the beam splitter is a right angle. The first lens is located within the beam range of the reflected rays of the beam splitter, and the first power meter is located at the convergence point of the beam after it is converged by the first lens.

[0044] Furthermore, the second and third measurement modules have the same structure, both including a second lens and a second power meter arranged sequentially along the optical path;

[0045] The second power meter of the second measurement module is located at the convergence point of the beam after it has been focused by the second lens.

[0046] Furthermore, this invention also provides a transmittance calibration system for the P-polarization state and the S-polarization state in a cluster focal spot measurement system.

[0047] It includes a first measurement module set at position A, a second measurement module set at position B, a third measurement module set at position C, a fourth measurement module set at position D, a first light source module set to the left of the target point, and a second light source module set below position C;

[0048] The first measurement module and the fourth measurement module have the same structure, both including a compensation mirror, a beam splitter, a first lens and a first power meter arranged sequentially along the optical path; the angle between the incident light and the reflected light of the beam splitter is a right angle, the first lens is located within the beam range of the reflected light of the beam splitter, and the first power meter is located at the convergence point of the beam after being converged by the first lens.

[0049] The second and third measurement modules have the same structure, both including a second lens and a second power meter arranged sequentially along the optical path; the second power meter of the second measurement module is located at the convergence point of the beam after it is converged by the second lens;

[0050] The first light source module includes a first standard light source, a first aperture, and a converging objective lens; the first aperture and the converging objective lens are arranged sequentially along the outgoing light path of the first standard light source, and the converging objective lens converges the outgoing light from the first standard light source at the target position;

[0051] The second light source module includes a second standard light source, a second aperture, a first reflector, and a second reflector; the second aperture and the first reflector are arranged sequentially along the outgoing light path of the second standard light source; the angle between the incident ray and the reflected ray of the first reflector is a right angle; the second reflector is located on the reflected light path of the first reflector; the angle between the incident ray and the reflected ray of the second reflector is a right angle.

[0052] Furthermore, two-dimensional translation stages are respectively set at positions A, B, C and D. The first measurement module, the second measurement module, the third measurement module and the fourth measurement module are respectively set on the four two-dimensional translation stages to facilitate access to the optical path or to perform scanning measurement according to the light spot distribution.

[0053] The second light source module is set on a one-dimensional translation stage. The reflected light from the second reflector in the second light source module is driven to enter or exit the second measurement system by the one-dimensional translation stage.

[0054] The beneficial effects of this invention are:

[0055] This invention enables the calibration of the transmittance of P and S polarization states in a clustered focal spot measurement system, avoiding the difference in energy distribution of the clustered focal spot at the image plane caused by the difference in transmittance of P and S polarization states in the clustered focal spot measurement system. It facilitates the compensation of the difference in transmittance of P and S polarization states, so as to achieve the purpose of accurately measuring the clustered focal spot, thereby enabling accurate judgment of the true morphology of the technical focal spot in high-power laser physics experiments. Attached Figure Description

[0056] Figure 1 This is a diagram of a cluster focal spot measurement system;

[0057] Figure 2 This is a calibration principle diagram of the transmittance calibration method and system for P-polarization state and S-polarization state in the cluster focal spot measurement system of the present invention.

[0058] In the picture:

[0059] 1-Clustered focal spot measurement system, 11-Target point, 12-Attenuator, 13-Fixed attenuator, 14-Collimating negative lens group, 15-Absorption plate;

[0060] 2-First light source module, 21-First standard light source, 22-First aperture stop, 23-Converging objective lens;

[0061] 3-Second light source module, 31-Second standard light source, 32-Second aperture, 33-First reflector, 34-Second reflector;

[0062] 4-Power meter;

[0063] 5-First measurement module, 51-Compensation mirror, 52-Beam splitter, 53-First lens, 54-First power meter;

[0064] 6-Second measurement module, 61-Second lens, 62-Second power meter;

[0065] 7-Third Measurement Module;

[0066] 8-Fourth Measurement Module. Detailed Implementation

[0067] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments.

[0068] In this embodiment, "up," "down," "left," and "right" are all indicated by the appendix. Figure 2 The direction within the paper is used as a reference, where XZ are the coordinates within the paper, and Y is perpendicular to the paper and outwards.

[0069] like Figure 2 The diagram shown is a schematic of the transmittance calibration method and system for P-polarization and S-polarization states in the cluster focal spot measurement system of the present invention.

[0070] In the clustered focal spot measurement system 1, the first measurement system extends from the target point 11 to the attenuator 12 on the left, and the second measurement system extends from the attenuator 12 on the left to the fixed attenuator 13. Position A is located in the parallel beam segment of the first P-polarized laser, position B is located between the target point 11 and the absorber 15 on the left in the clustered focal spot measurement system 1, position C is located between the collimating negative lens group 14 and the attenuator 12 on the left in the clustered focal spot measurement system 1, position D is located in the output beam path of the second P-polarized laser, and position E is located at the beam convergence point after the fixed attenuator 13.

[0071] This invention provides a transmittance calibration system for P-polarization and S-polarization states in a cluster focal spot measurement system.

[0072] It includes a first measurement module 5 set at position A, a second measurement module 6 set at position B, a third measurement module 7 set at position C, a fourth measurement module 8 set at position D, a first light source module 2 set to the left of target point 11, and a second light source module 3 set below position C;

[0073] The first measurement module 5 and the fourth measurement module 8 have the same structure, both including a compensation mirror 51, a beam splitter 52, a first lens 53 and a first power meter 54 arranged sequentially along the optical path; the angle between the incident light and the reflected light of the beam splitter 52 is a right angle, the first lens 53 is located within the beam range of the reflected light of the beam splitter 52, and the first power meter 54 is located at the convergence point of the beam after being converged by the first lens 53;

[0074] The second measurement module 6 and the third measurement module 7 have the same structure, both including a second lens 61 and a second power meter 62 arranged sequentially along the optical path; the second power meter 62 of the second measurement module 6 is located at the convergence point of the beam after being converged by the second lens 61;

[0075] The first light source module 2 includes a first standard aperture 21, a first aperture 22, and a converging objective lens 23; the first aperture 22 and the converging objective lens 23 are arranged sequentially along the outgoing light path of the first standard light source 21, and the converging objective lens 23 converges the outgoing light from the first standard light source 21 to the target point 11.

[0076] The second light source module 3 includes a second standard light source 31, a second aperture 32, a first reflector 33, and a second reflector 34; the second aperture 32 and the first reflector 33 are arranged sequentially along the outgoing light path of the second standard light source 31; the angle between the incident light and the reflected light of the first reflector 33 is a right angle; the second reflector 34 is located on the reflected light path of the first reflector 33; the angle between the incident light and the reflected light of the second reflector 34 is a right angle.

[0077] Furthermore, two-dimensional translation stages are respectively set at positions A, B, C and D. The first measurement module 5, the second measurement module 6, the third measurement module 7 and the fourth measurement module 8 are respectively set on the four two-dimensional translation stages to facilitate access to the optical path or to perform scanning measurement according to the light spot distribution.

[0078] The second light source module 3 is set on a one-dimensional translation stage. The reflected light from the second reflector 34 in the second light source module 3 is driven to enter or exit the second measurement system by the one-dimensional translation stage.

[0079] The transmittance calibration method for P-polarization state and S-polarization state in the cluster focal spot measurement system of the present invention is performed according to the following steps:

[0080] Step 1: Focus the first P-polarized laser emitted from the first light source module 2 onto the target point 11 and complete the docking with the first measurement system.

[0081] Step 2: Simultaneously measure the light spot at position A and the light spot at position B, and obtain the light spot power at position A, denoted as W. 11 The power of the light spot at position B is denoted as W2;

[0082] The specific implementation method is as follows:

[0083] The first measurement module 5 is connected to the optical path at position A by a two-dimensional electric translation stage (capable of moving in the X and Y directions), and the second measurement module 6 is connected to the optical path at position B by a two-dimensional electric translation stage. The first measurement module 5 is driven by the two-dimensional electric translation stage to scan according to the light spot distribution trajectory at position A, and the second measurement module 6 is driven by the two-dimensional electric translation stage to scan according to the light spot distribution trajectory at position B, so as to simultaneously measure the light spot power at positions A and B.

[0084] After the measurement is completed, the second measurement module 6 at position B is removed from the optical path using a two-dimensional electric translation stage.

[0085] Step 3: Simultaneously measure the light spot at position A and position C, and obtain the power at position A, denoted as W. 12 The power at position C is denoted as W. 31 ;

[0086] The specific implementation method is as follows:

[0087] The third measurement module 7 is connected to the optical path at position C by a two-dimensional electric translation stage set at position C. When the first measurement module 5 is performing measurement, the third measurement module 7 is driven by the two-dimensional electric translation stage to scan according to the light spot distribution trajectory at position C, and the light spot power at positions A and C is measured simultaneously.

[0088] After the measurement is completed, the first measurement module 5 and the third measurement module 7 are removed from the optical path by a two-dimensional electric translation stage;

[0089] Step 4: Remove the first P-polarized laser from the measurement system, and use a one-dimensional electric translation stage (which can only move in the X direction) set at position C to dock the second P-polarized laser with the second section of the measurement system at position C;

[0090] Step 5: Simultaneously measure the light spot at position C and position D, and record the power at position C as W. 32 The power at position D is denoted as W. 41 ;

[0091] The specific implementation method is as follows:

[0092] The third measurement module 7 is connected to the optical path at position C by a two-dimensional electric translation stage, and the fourth measurement module 8 is connected to the optical path at position D by a two-dimensional electric translation stage set at position D. The third measurement module 7 is driven by the two-dimensional electric translation stage to scan according to the light spot distribution at position C, and the fourth measurement module 8 is driven by the two-dimensional electric translation stage to scan according to the light spot distribution at position D, and the light spot power at positions C and D is measured simultaneously.

[0093] After the measurement is completed, the third measurement module 7 at position C is removed from the optical path by a two-dimensional electric translation stage.

[0094] Step 6: Simultaneously measure the light spot at position E and position D, and record the power at position E as W5 and the power at position D as W. 42 ;

[0095] The specific implementation method is as follows:

[0096] The power meter 4 at position E directly receives the beam focused at position E. The electric translation stage at position D drives the fourth measurement module 8 to scan according to the beam distribution trajectory at position D, and simultaneously measures the beam power at positions D and E.

[0097] After the measurement is completed, remove the fourth measurement module 8 at position D from the optical path;

[0098] Step 7: Calculate the transmittance T of the first measurement system. Px1 =(W31 / W 12 ) / (W2 / W 11 ) = (W 31 ×W 11 ) / (W2×W 12 The transmittance T of the second measurement system Px2 =(W5 / W 42 ) / (W 32 / W 41 ) = (W5 × W 41 ) / (W 32 ×W 42 );

[0099] Step 8: Calculate the P-polarization state transmittance coefficient T of the measurement system. p =T Px1 ×T Px2 ;

[0100] Step 9: Replace the first P-polarized laser and the second P-polarized laser with the first S-polarized laser and the second S-polarized laser, and repeat steps 1-8 above to obtain the S-polarized transmittance coefficient T of the measurement system. S =T Sx1 ×T Sx2 ;

[0101] Through the above steps, this invention can calibrate the transmittance of each light path in the P and S polarization states of the clustered focal spot measurement system 1. This avoids the difference in transmittance of different polarization states of light in the measurement system, which would lead to differences in the energy distribution of the clustered focal spot at the image plane position, thus causing differences in the true morphology of the clustered focal spot and resulting in a large error in the measurement results of the clustered focal spot. This error directly affects the judgment of the morphology of the clustered focal spot in high-power laser physics experiments.

[0102] Specifically, the first P-polarized laser in step 1 or the first S-polarized laser in step 9 is emitted by the first light source module 2; the first light source module 2 is located to the left of the target point 11; the first light source module 2 includes a first standard light source 21, a first aperture 22 and a converging objective lens 23; the first aperture 22 and the converging objective lens 23 are arranged sequentially along the parallel beam emitted from the first standard light source 21, and the converging objective lens 23 converges the emitted light from the first standard light source 21 to the target point 11; position A is located between the first aperture 22 and the converging objective lens 23.

[0103] Specifically, the second P-polarized laser in step 4 or the second S-polarized laser in step 9 is emitted by the second light source module 3; the second light source module 3 is located below position C; the second light source module 3 includes a second standard light source 31, a second aperture 32, a first reflector 33, and a second reflector 34; the second aperture 32 and the first reflector 33 are arranged sequentially along the direction of the parallel beam emitted from the second standard light source 31; the angle between the incident ray and the reflected ray of the first reflector 33 is a right angle; the second reflector 34 is located on the reflected light path of the first reflector 33; the angle between the incident ray and the reflected ray of the second reflector 34 is a right angle; the reflected beam of the second reflector 34 can be connected to the second measurement system for subsequent calibration using a one-dimensional electric translation stage, and position D is located between the second aperture 32 and the first reflector 33.

[0104] Specifically, the first measurement module 5 and the fourth measurement module 8 have the same structure, both including a compensation mirror 51, a beam splitter 52, a first lens 53, and a first power meter 54. The compensation mirror 51 and the beam splitter 52 are arranged sequentially along the optical path. The addition of the compensation mirror 51 between the beam splitters 52 ensures that the output optical axis remains unchanged. The angle between the incident light and the reflected light of the beam splitter 52 is a right angle. The first lens 53 is located within the beam range of the reflected light of the beam splitter 52. The converging light of the first lens 53 enters the first power meter 54, and the convergence point is at the entrance position of the first power meter 54. The parallel light emitted from the first standard light source 21 enters the first power meter 54 after being reflected by the beam splitter 52 of the first measurement module 5. The parallel light emitted from the first standard light source 21 is coupled to the target point 11 after being transmitted through the beam splitter 52 for subsequent calibration.

[0105] Specifically, the second measurement module 6 and the third measurement module 7 have the same structure, both including a second lens 61 and a second power meter 62 arranged sequentially along the optical path; the second power meter 62 is located at the convergence point of the beam after being converged by the second lens 61.

Claims

1. A method for calibrating the transmittance of P-polarization state and S-polarization state in a clustered focal spot measurement system. The clustered focal spot measurement system (1) includes multiple absorbers (15), a sampling mirror group, a collimating negative lens group (14), a first attenuator group, a magnifying lens group, a second attenuator group, and a CCD. The first attenuator group includes at least two attenuators. The second attenuator group includes a wheel attenuator and a fixed attenuator (13). The position of the clustered focal spot to be measured in the clustered focal spot measurement system (1) is the position of the target point (11). The target point (11), the absorber (15) on the left, the sampling mirror group, the absorber (15) on the right, the collimating negative lens group (14), the first attenuator group, the magnifying lens group, the second attenuator group, and the CCD are arranged from left to right along the optical path transmission direction. In the cluster focal spot measurement system (1), the first measurement system is from the target point (11) to the attenuator (12) on the left, and the second measurement system is from the attenuator (12) on the left to the fixed attenuator (13). Position A is located in the parallel beam segment of the first P-polarized laser, position B is located between the target point (11) in the cluster focal spot measurement system (1) and the absorber (15) on the left in the cluster focal spot measurement system (1), position C is located between the collimating negative lens group (14) in the cluster focal spot measurement system (1) and the attenuator (12) on the left, position D is located in the output light path of the second P-polarized laser, and position E is located at the beam convergence point after the fixed attenuator (13). Its features are: Step 1: Focus the first P-polarized laser at the target point (11) and dock it with the first section of the measurement system in the cluster focal spot measurement system (1) before the attenuator (12) on the left. Step 2, synchronously measure the light spot at position A of the parallel light beam segment of the first P-polarization state laser and the light spot between the target point (11) in the focal spot measurement system (1) and the absorbing sheet (15) on the left side of the focal spot measurement system (1) at position B, and the light spot power at position A is recorded as W 11 , and the light spot power at position B is recorded as W2; Step 3: Simultaneously measure the light spot at position A and the light spot at position C, located between the collimating negative lens group (14) and the attenuator (12) on the left side in the cluster focal spot measurement system (1), and obtain the power at position A, denoted as W. 12 The power at position C is denoted as W. 31 ; Step 4: Remove the first P-polarized laser from the first measurement system and dock the second P-polarized laser at position C with the second measurement system after the attenuator (12) on the left and the fixed attenuator (13). Step 5: Simultaneously measure the light spot at position C and the light spot at position D on the output optical path of the second P-polarized laser, and obtain the power at position C, denoted as W. 32 The power at position D is denoted as W. 41 ; Step 6: Simultaneously measure the beam spot at position E and position D, which are located behind the fixed attenuator (13) in the beam convergence point of the beam-focusing system (1). The power at position E is denoted as W5, and the power at position D is denoted as W. 42 ; Step 7: Calculate the transmittance T of the first measurement system. Px1 =(W 31 ×W 11 ) / (W2×W 12 The transmittance T of the second measurement system Px2 =(W5×W 41 ) / (W 32 ×W 42 ); Step 8: Calculate the P-polarization state transmittance coefficient of the cluster focal spot measurement system (1): T p =T Px1 ×T Px2 ; Step 9: Replace the first P-polarized laser and the second P-polarized laser with the first S-polarized laser and the second S-polarized laser, and repeat steps 1-8 above to obtain the S-polarized transmittance coefficient T of the cluster focal spot measurement system (1). S =T Sx1 ×T Sx2 .

2. The method for calibrating transmittance of P-polarization state and S-polarization state in the cluster focal spot measurement system according to claim 1, characterized in that: The first P-polarized laser in step 1 or the first S-polarized laser in step 9 is emitted by the first light source module (2); The first light source module (2) is located to the left of the target point (11); The first light source module (2) includes a first standard light source (21), a first aperture (22), and a converging objective lens (23); The first aperture (22) and the converging objective (23) are arranged sequentially along the outgoing light path of the first standard light source (21), and the converging objective (23) converges the outgoing light of the first standard light source (21) at the target point (11). Position A is located between the first aperture (22) and the converging objective (23).

3. The method for calibrating the transmittance of the P-polarization state and the S-polarization state in the cluster focal spot measurement system according to claim 2, characterized in that, Step 2 shall be implemented in the following manner: The first measurement module (5) is connected to the optical path at position A, and the second measurement module (6) is connected to the optical path at position B. The first measurement module (5) scans according to the light spot distribution at position A, and the second measurement module (6) scans according to the light spot distribution at position B, and the light spot power at positions A and B is measured simultaneously. After the measurement is completed, the second measurement module (6) at position B is removed from the optical path.

4. The method for calibrating the transmittance of the P-polarization state and the S-polarization state in the cluster focal spot measurement system according to claim 3, characterized in that: Step 3 shall be implemented in the following manner: The third measurement module (7) is connected to the optical path at position C. When the first measurement module (5) is performing measurement, the third measurement module (7) scans according to the light spot distribution at position C and simultaneously measures the light spot power at positions A and C. After the measurement is completed, the first measurement module (5) and the third measurement module (7) are removed from the optical path.

5. The method for calibrating the transmittance of the P-polarization state and the S-polarization state in the cluster focal spot measurement system according to claim 4, characterized in that: The second P-polarized laser in step 4 or the second S-polarized laser in step 9 is emitted by the second light source module (3); The second light source module (3) is located below position C; The second light source module (3) includes a second standard light source (31), a second aperture (32), a first reflector (33), and a second reflector (34); The second aperture (32) and the first reflector (33) are arranged sequentially along the outgoing light path of the second standard light source (31); The angle between the incident ray and the reflected ray of the first reflector (33) is a right angle; The second reflector (34) is located on the reflected light path of the first reflector (33); The angle between the incident ray and the reflected ray of the second reflector (34) is a right angle; The D position is located between the second aperture (32) and the first reflector (33).

6. The method for calibrating the transmittance of the P-polarization state and the S-polarization state in the cluster focal spot measurement system according to claim 5, characterized in that, Step 5 shall be implemented in the following manner: The third measurement module (7) is connected to the optical path at position C, and the fourth measurement module (8) is connected to the optical path at position D. The third measurement module (7) scans according to the light spot distribution at position C, and the fourth measurement module (8) scans according to the light spot distribution at position D, simultaneously measuring the light spot power at positions C and D. After the measurement is completed, the third measurement module (7) at position C is removed from the optical path.

7. The method for calibrating transmittance of P-polarization state and S-polarization state in the cluster focal spot measurement system according to claim 6, characterized in that, Step 6 shall be implemented in the following manner: The power meter (4) at position E receives the beam converged at position E, and the fourth measurement module (8) scans according to the beam distribution trajectory at position D, and simultaneously measures the beam power at positions D and E. After the measurement is completed, the fourth measurement module (8) at position D is removed from the optical path.

8. The method for calibrating the transmittance of the P-polarization state and the S-polarization state in the cluster focal spot measurement system according to claim 7, characterized in that: The first measurement module (5) and the fourth measurement module (8) have the same structure, both including a compensation mirror (51), a beam splitter (52), a first lens (53) and a first power meter (54) arranged sequentially along the optical path; The angle between the incident and reflected rays of the beam splitter (52) is a right angle. The first lens (53) is located within the beam range of the reflected rays of the beam splitter (52). The first power meter (54) is located at the convergence point of the beam after it is converged by the first lens (53).

9. The method for calibrating transmittance of P-polarization state and S-polarization state in the cluster focal spot measurement system according to claim 7, characterized in that: The second measurement module (6) and the third measurement module (7) have the same structure, both including a second lens (61) and a second power meter (62) arranged sequentially along the optical path; The second power meter (62) of the second measurement module (6) is located at the convergence point of the beam after it is focused by the second lens (61).

10. A transmittance calibration system for P-polarization and S-polarization states in a clustered focal spot measurement system, used to implement the transmittance calibration method for P-polarization and S-polarization states in the clustered focal spot measurement system as described in claim 7, characterized in that: It includes a first measurement module (5) set at position A, a second measurement module (6) set at position B, a third measurement module (7) set at position C, a fourth measurement module (8) set at position D, a first light source module (2) set to the left of the target point (11), and a second light source module (3) set below position C; The first measurement module (5) and the fourth measurement module (8) have the same structure, both including a compensation mirror (51), a beam splitter (52), a first lens (53) and a first power meter (54) arranged sequentially along the optical path; the angle between the incident light and the reflected light of the beam splitter (52) is a right angle, the first lens (53) is located within the beam range of the reflected light of the beam splitter (52), and the first power meter (54) is located at the convergence point of the beam after being converged by the first lens (53); The second measurement module (6) and the third measurement module (7) have the same structure, both including a second lens (61) and a second power meter (62) arranged sequentially along the optical path; the second power meter (62) of the second measurement module (6) is located at the convergence point of the beam after being converged by the second lens (61); The first light source module (2) includes a first standard light source (21), a first aperture (22) and a converging objective (23); the first aperture (22) and the converging objective (23) are arranged sequentially along the outgoing light path of the first standard light source (21), and the converging objective (23) converges the outgoing light of the first standard light source (21) at the target point (11); The second light source module (3) includes a second standard light source (31), a second aperture (32), a first reflector (33), and a second reflector (34); the second aperture (32) and the first reflector (33) are arranged sequentially along the outgoing light path of the second standard light source (31); the angle between the incident light and the reflected light of the first reflector (33) is a right angle; the second reflector (34) is located on the reflected light path of the first reflector (33); the angle between the incident light and the reflected light of the second reflector (34) is a right angle. Furthermore, two-dimensional translation stages are respectively set at positions A, B, C and D. The first measurement module (5), the second measurement module (6), the third measurement module (7) and the fourth measurement module (8) are respectively set on the four two-dimensional translation stages to facilitate access to the optical path or to perform scanning measurement according to the light spot distribution. The second light source module (3) is set on a one-dimensional translation stage. The reflected light from the second reflector (34) in the second light source module (3) is driven to enter or exit the second measurement system by the one-dimensional translation stage.

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