Device and method for measuring two-dimensional single-wavelength radiance of LSP light source

Abstract

The invention provides a device and a method for measuring the two-dimensional single-wavelength radiance of an LSP (Label Switched Path) light source. The device is characterized in that a light beam emitted by a measured light source passes through a band-pass optical filter, passes through a front-end lens assembly, and is reflected and transmitted by a beam splitting cube; the reflected light beam is converged to a first photosensitive element through a neutral density optical filter, and two-dimensional intensity information of the measured light source is recorded; a transmission light beam is converged to a field diaphragm assembly, a light beam transmitted by the field diaphragm assembly is converged to a photoelectric detector through a rear-end lens assembly, and radiation flux information of the detected light source is recorded; and the light beam reflected by the field diaphragm assembly is reflected by the beam splitting cube and then is converged to the second photosensitive element through the observation lens assembly, so that focusing and alignment of the measured light source are realized. According to the invention, the measurement requirement of the two-dimensional single-wavelength radiation brightness of ultra-small and high-brightness light sources such as LSP light sources can be effectively met.

Description

Technical Field

[0001] This invention relates to the field of improving the measurement of two-dimensional spatial radiance of LSP (Laser-sustained Plasma) light sources, and particularly to a device and method for measuring the two-dimensional single-wavelength radiance of LSP light sources. Background Technology

[0002] Traditional radiance measurement devices consist of a monochromator and a front-end optical path structure, such as... Figure 1 As shown, the front-end optical path structure includes a field stop, a concave mirror, and a reflecting mirror, which enter the interior of the monochromator with different object image ratios and solid angles.

[0003] The tested light source and the standard light source passed through Figure 1 The optical imaging system of the measurement device shown is generally of the transmission or reflection type. The image is projected onto the slit of the monochromator. A computer controls the rotation angle of the grating inside the monochromator to measure the spectral response values ​​at different wavelengths. The radiance of the light source under test is calculated using the radiance of a known standard light source. However, existing radiance measurement devices are only suitable for measuring the single-point broadband radiance of light sources such as tungsten ribbon lamps (large emitting area). The size of the field stop determines the low spatial resolution of the radiance measurement.

[0004] In addition, existing measurement devices typically place the field stop in front of the incident optical system and the size of the field stop is on the order of mm. This is not suitable for the characteristics of LSP light sources (radial half-width less than 200μm). The emitting area of ​​the LSP light source cannot completely fill the sampling field stop of the existing measurement device, resulting in inconsistent comparison conditions and measurement errors. Summary of the Invention

[0005] A brief overview of the invention is given below to provide a basic understanding of certain aspects of it. It should be understood that this overview is not an exhaustive summary of the invention. It is not intended to identify key or essential parts of the invention, nor is it intended to limit the scope of the invention. Its purpose is merely to present certain concepts in a simplified form as a prelude to the more detailed description that follows.

[0006] In view of this, in order to solve the above problems, the present invention proposes a measurement device and method for two-dimensional single-wavelength radiance of LSP light source, so as to realize the measurement of two-dimensional spatial radiance data of LSP.

[0007] This invention provides a measurement device for two-dimensional single-wavelength radiance of an LSP light source, comprising:

[0008] Bandpass filter, beam splitter cube, neutral density filter, front lens assembly, rear lens assembly, observation lens assembly, first photosensitive element, second photosensitive element, photodetector, and field stop assembly;

[0009] The light beam emitted by the light source under test passes through the bandpass filter and forms narrowband light;

[0010] The narrowband light passes through the front-end lens assembly and is reflected and transmitted through the beam splitter cube to form a reflected beam and a transmitted beam.

[0011] The reflected light beam is focused onto the first photosensitive element through the neutral density filter to record the two-dimensional intensity information of the light source under test;

[0012] The transmitted light beam is converged to the field stop assembly, and the light beam transmitted through the field stop assembly is converged to the photodetector through the rear lens assembly to record the radiant flux information of the light source under test.

[0013] The transmitted light beam is converged to the field stop assembly. The light beam reflected by the field stop assembly is reflected by the beam splitter cube and then converged to the second photosensitive element by the observation lens assembly, thereby achieving focusing and alignment of the light source under test.

[0014] Preferably, the front-end lens assembly includes: a first lens and a second lens arranged sequentially along the beam propagation direction; the light source under test is located at twice the effective focal length of the front-end lens assembly; the field stop assembly is located at twice the effective focal length of the front-end lens assembly; and the first photosensitive element is located at twice the effective focal length of the front-end lens assembly.

[0015] Preferably, the rear lens assembly includes: a third lens and a fourth lens arranged sequentially along the beam propagation direction; the field stop assembly is located at twice the effective focal length of the rear lens assembly; and the photodetector is located at twice the effective focal length of the rear lens assembly.

[0016] Preferably, the observation lens assembly includes a fifth lens and a sixth lens arranged sequentially along the beam propagation direction, the field stop assembly is located at twice the effective focal length of the observation lens assembly, and the second photosensitive element is located at twice the effective focal length of the observation lens assembly.

[0017] Preferably, the field stop assembly includes: a focusing panel, and one or more field stops.

[0018] Preferably, the apparatus further includes: a standard halogen lamp light source, a standard LSP light source, a one-dimensional translation stage, a two-dimensional translation stage, and a three-dimensional displacement stage. The standard halogen lamp light source, the standard LSP light source, and the light source under test are disposed on the one-dimensional translation stage and move with the one-dimensional translation stage. The field-of-view aperture assembly is disposed on the two-dimensional translation stage and moves with the two-dimensional translation stage. The measuring device for the two-dimensional single-wavelength radiance of the LSP light source is disposed on the three-dimensional displacement stage and moves with the three-dimensional translation stage. The standard halogen lamp light source is a standard radiance light source used to calibrate the transfer coefficients of different field-of-view apertures, and the standard LSP light source is a tunable standard radiance light source used to calibrate the correlation coefficient in the linear function between the gray value of the photosensitive element and the radiance.

[0019] On the other hand, the present invention also provides a method for measuring the two-dimensional single-wavelength radiance of an LSP light source, comprising:

[0020] The light beam emitted by the light source under test is passed through a bandpass filter to form narrowband light;

[0021] The narrowband light passes through the front-end lens assembly and is reflected and transmitted through the beam splitter cube to form a reflected beam and a transmitted beam.

[0022] The transmitted light beam is focused onto the field stop assembly. The light beam reflected by the focusing panel of the field stop assembly is reflected by the beam splitter cube and then focused onto the second photosensitive element by the observation lens assembly.

[0023] Adjust the distance and position of the light source under test relative to the front lens assembly so that the light beam reflected by the focusing panel of the field stop assembly from the light source under test is imaged on the second photosensitive element to meet the constraint conditions, thereby achieving preliminary focusing and alignment of the light source under test.

[0024] Move the field stop assembly so that the beam transmitted by the beam splitter cube converges to the field stop of the field stop assembly. The beam transmitted through the field stop is then converged to the photodetector by the rear lens assembly.

[0025] Adjust the distance and position of the light source under test relative to the front lens assembly to make the photodetector reach the maximum response value, thereby achieving precise focusing and alignment of the light source under test;

[0026] The reflected light beam is focused onto the first photosensitive element through a neutral density filter, and the two-dimensional intensity information of the light source under test is recorded. Based on the linear relationship between the gray value of the first photosensitive element and the radiance, the two-dimensional single-wavelength radiance of the light source under test is obtained.

[0027] Preferably, the method further includes, prior to:

[0028] The light beam emitted by a standard halogen lamp light source passes through the bandpass filter to form halogen narrowband light;

[0029] The halogen narrowband light is passed through the front lens assembly, and the beam transmitted from the beam splitter cube is converged to the focusing panel of the field stop assembly.

[0030] The light beam reflected by the focusing panel is reflected by the beam splitter cube, and then converged by the observation lens assembly to the second photosensitive element.

[0031] Adjusting the distance and position of the standard halogen lamp light source relative to the front lens assembly, so that the light beam reflected by the standard halogen lamp light source through the focusing panel forms an image on the second photosensitive element that meets the constraint conditions, thereby achieving focusing and alignment of the standard halogen lamp light source;

[0032] Move the field stop assembly to converge the beam transmitted by the beam splitter cube to the field stop of the field stop assembly;

[0033] The light beam transmitted through the field stop is focused by the rear lens assembly onto the photodetector to record the radiant flux information of the standard halogen lamp light source.

[0034] Based on the radiant flux information and the radiant brightness information of the standard halogen lamp light source, the transfer coefficients of different field stops in the field stop assembly are determined.

[0035] Preferably, the method further includes, prior to:

[0036] The light beam emitted by the standard LSP light source passes through an adjustable step neutral density filter and then through the bandpass filter to form LSP narrowband light;

[0037] The LSP narrowband light passes through the front-end lens assembly and is reflected and transmitted through the beam splitter cube to form a reflected beam and a transmitted beam.

[0038] The transmitted light beam is focused onto the field stop assembly. The light beam reflected by the focusing panel of the field stop assembly is reflected by the beam splitter cube and then focused onto the second photosensitive element by the observation lens assembly.

[0039] Adjust the distance and position of the standard LSP light source relative to the front lens assembly so that the light beam reflected by the standard LSP light source through the focusing panel images the second photosensitive element to meet the constraint conditions, thereby achieving the initial focusing and alignment of the standard LSP light source.

[0040] Move the field stop assembly to converge the beam transmitted by the split cube to the field stop of the field stop assembly;

[0041] The light beam transmitted through the field stop is focused onto the photodetector by the rear lens assembly;

[0042] Adjust the distance and position of the standard LSP light source relative to the front-end lens assembly to enable the photodetector to reach its maximum response value, achieve precise focusing and alignment of the standard LSP light source, and record the radiant flux information of the standard LSP light source.

[0043] Based on the transfer coefficient of the field stop, the single-point single-wavelength radiance of the standard LSP light source is obtained.

[0044] The reflected light beam is focused onto the first photosensitive element through the neutral density filter to record the two-dimensional intensity information of the standard LSP light source.

[0045] Preferably, the method further includes:

[0046] Calculate the single-point, single-wavelength radiance information of the measured light source based on the transfer coefficient and the radiant flux information of the measured light source: L 被测 =KV 被测 ;

[0047]

[0048] L 卤素 It is the radiant value of a standard halogen lamp light source at the center wavelength λ of the bandpass filter; V 卤素 It is the response value of a standard halogen lamp light source within the passband of the bandpass filter; L 被测 V is the radiance value of the light source being measured at the center wavelength λ of the bandpass filter; 被测 It is the response value of the measured light source within the passband of the bandpass filter; S 大 It is used to measure the area of ​​the large field-of-view aperture of a standard halogen lamp light source; S 小 It is used to measure the area of ​​a small field-of-view aperture of the light source under test, wherein the response value is the current or voltage value received by the photodetector, which is proportional to the radiant flux of the light beam transmitted through the field-of-view aperture and the subsequent lens assembly; the passband range is related to the center wavelength λ and bandwidth λ of the bandpass filter. FWHM related.

[0049] Preferably, the method further includes:

[0050] By combining the standard LSP light source with an adjustable stepped neutral density filter, a tunable standard radiance light source is constructed. The maximum average gray value and corresponding radiance within the corresponding field stop region are recorded in the two-dimensional intensity information at different transmittance levels. This yields the gray value DN and radiance L of the first photosensitive element. c The linear relationship satisfied is:

[0051]

[0052] Where t is the exposure time of the image sensor; G is the gain coefficient of the image sensor; η is the quantum efficiency of the photosensitive element; k is the linearity coefficient of the optical system; L c A is the radiance at the center wavelength of the bandpass filter; E is the pixel area of ​​the image sensor; c It is the photon energy at the center wavelength of the bandpass filter; DN (digital number) is the gray value of the photosensitive element; DN dark It is the dark noise of the image sensor, λ FWHM It is the bandwidth of the bandpass filter.

[0053] The present invention provides a device and method for measuring the two-dimensional single-wavelength radiance of an LSP light source. By utilizing the two-dimensional intensity information of the LSP light source under test and the linear function of the gray value and radiance of the first photosensitive element, the two-dimensional single-wavelength radiance of the LSP light source under test can be obtained. This enables the measurement of the two-dimensional single-wavelength radiance of the LSP light source, effectively meeting the measurement requirements of two-dimensional single-wavelength radiance of ultra-small, high-brightness light sources such as LSP light sources, and also achieving accurate interception of light source intensity, thus avoiding measurement errors.

[0054] These and other advantages of the invention will become more apparent from the following detailed description of the preferred embodiments of the invention in conjunction with the accompanying drawings. Attached Figure Description

[0055] The present invention can be better understood by referring to the description given below in conjunction with the accompanying drawings, in which the same or similar reference numerals are used throughout the drawings to denote the same or similar parts. These drawings, together with the following detailed description, are incorporated in and form part of this specification, and are used to further illustrate preferred embodiments of the invention and explain the principles and advantages of the invention. In the drawings:

[0056] Figure 1 This is a schematic diagram of a conventional spectral radiance device;

[0057] Figure 2 This is a schematic diagram illustrating the structure of the measurement device for two-dimensional single-wavelength radiance of an LSP light source according to the present invention;

[0058] Figure 3 This is a schematic diagram illustrating the field stop assembly H1 of the present invention;

[0059] Figure 4 This is a flowchart illustrating the method for measuring the two-dimensional single-wavelength radiance of an LSP light source according to the present invention;

[0060] Figure 5This shows the two-dimensional radiance of the LSP light source under test at a wavelength of 440 nm according to the present invention;

[0061] Figure 6 This is a graph showing the relationship between the maximum average gray value and its radiance within the corresponding field stop region of the standard LSP light source image acquired by the first photosensitive element under different exposure time conditions according to the present invention.

[0062] In the attached diagram: F1: bandpass filter; L1: first lens; L2: second lens; S1: beam splitter cube; H1: field stop assembly; L3: third lens; L4: fourth lens; F2: neutral density filter; PD: photodetector; L5: fifth lens; L6: sixth lens; F3: variable step neutral density filter.

[0063] Those skilled in the art will understand that the elements in the accompanying drawings are shown for simplicity and clarity only, and are not necessarily drawn to scale. For example, the dimensions of some elements in the drawings may be enlarged relative to other elements to aid in understanding the embodiments of the invention. Detailed Implementation

[0064] Exemplary embodiments of the invention will be described below with reference to the accompanying drawings. For clarity and brevity, not all features of actual implementations are described in the specification. However, it should be understood that many implementation-specific decisions must be made in the development of any such actual embodiment to achieve the developer's specific goals, such as complying with constraints related to the system and business, and these constraints may vary depending on the implementation. Furthermore, it should be understood that while development work can be very complex and time-consuming, such development work is merely a routine task for those skilled in the art who benefit from this disclosure.

[0065] It should also be noted that, in order to avoid obscuring the invention with unnecessary details, only the device structure closely related to the solution according to the invention is shown in the accompanying drawings, while other details that are not closely related to the invention are omitted.

[0066] Laser-sustained plasma (LSP) light sources, characterized by high brightness, broad spectrum, and high stability, are widely used in fields such as material characterization, meteorological analysis and measurement, and optical sensor detection. The radiance of a light source, as an important physical quantity in radiometrics, specifically reflects the characteristics of the light source.

[0067] Traditional measuring devices can only measure a single point in the light-emitting area of ​​a light source. To achieve two-dimensional spatial radiance measurement, the sampling area of ​​the light source under test needs to be changed by altering the field of view aperture. This is difficult to operate and has low spatial resolution (on the order of millimeters), making it difficult to meet the two-dimensional radiance measurement requirements of LSP light sources.

[0068] Therefore, the two-dimensional single-wavelength radiance measurement device for LSP light sources in this embodiment of the invention is particularly important. The measurement device achieves two-dimensional single-wavelength radiance measurement by combining an image sensing element, such as a CCD (Charge Coupled Device) camera or a CMOS (Complementary Metal-Oxide-Semiconductor) camera, with a high-sensitivity PD (Photoelectric Detector) suitable for detecting weak light signals.

[0069] Furthermore, based on the two-dimensional spatial radiance data of LSP, and through optical emission spectroscopy diagnostic techniques, parameters of the electron temperature and electron density of the plasma can be obtained, which is of great significance for the study of LSP light sources.

[0070] like Figure 2 As shown, this embodiment of the invention provides a measurement device for two-dimensional single-wavelength radiance of an LSP light source, comprising:

[0071] Bandpass filter F1, beam splitter S1, neutral density filter F2, front lens assembly, rear lens assembly, observation lens assembly, first photosensitive element C1, second photosensitive element C2, photodetector PD, and field stop assembly H1;

[0072] The light beam emitted by the light source under test passes through the bandpass filter F1 and forms narrowband light;

[0073] The narrowband light passes through the front-end lens assembly and is reflected and transmitted by the beam splitter S1 to form a reflected beam and a transmitted beam.

[0074] The reflected light beam is converged to the first photosensitive element C1 through the neutral density filter F2 to record the two-dimensional intensity information of the light source under test;

[0075] The transmitted light beam is converged to the field stop assembly H1, and the light beam transmitted through the field stop assembly H1 is converged to the photodetector PD through the rear lens assembly to record the radiant flux information of the light source under test.

[0076] The transmitted light beam is converged to the field stop assembly H1. The light beam reflected by the field stop assembly H1 is reflected by the beam splitter S1 and then converged to the second photosensitive element C2 by the observation lens assembly, thereby achieving focusing and alignment of the light source under test.

[0077] In this embodiment of the invention, the front-end lens assembly includes: a first lens L1 and a second lens L2 arranged sequentially along the beam propagation direction; the light source under test is located at twice the effective focal length of the front-end lens assembly; the field stop assembly H1 is located at twice the effective focal length of the front-end lens assembly; and the first photosensitive element C1 is located at twice the effective focal length of the front-end lens assembly.

[0078] In this embodiment of the invention, the rear-end lens assembly includes: a third lens L3 and a fourth lens L4 arranged sequentially along the beam propagation direction; the field stop assembly H1 is located at twice the effective focal length of the rear-end lens assembly; and the photodetector PD is located at twice the effective focal length of the rear-end lens assembly.

[0079] In this embodiment of the invention, the observation lens assembly includes a fifth lens L5 and a sixth lens L6 arranged sequentially along the beam propagation direction; the field stop assembly H1 is located at twice the effective focal length of the observation lens assembly; and the second photosensitive element C2 is located at twice the effective focal length of the observation lens assembly.

[0080] In the embodiments of the present invention, the equivalent object distance or equivalent image distance at twice the effective focal length has taken into account the effect of medium refraction.

[0081] like Figure 2 As shown, the neutral density filter F2 is disposed on the transmission path of the reflected light beam between the beam splitter S1 and the first photosensitive element C1.

[0082] In this embodiment of the invention, a neutral density filter F2 is used to reduce the irradiance incident on the first photosensitive element C1, so as to avoid excessive irradiance incident on the first photosensitive element C1, which could lead to saturation or damage to the first photosensitive element C1.

[0083] like Figure 3 As shown, the field stop assembly H1 includes: a focusing panel, and one or more field stops.

[0084] In this embodiment of the invention, the device further includes: a standard halogen lamp light source, a standard LSP light source, a one-dimensional translation stage, a two-dimensional translation stage, and a three-dimensional displacement stage. The standard halogen lamp light source, the standard LSP light source, and the light source under test are disposed on the one-dimensional translation stage and move with the one-dimensional translation stage in the X direction. The field-of-view aperture assembly H1 is disposed on the two-dimensional translation stage and moves with the two-dimensional translation stage in the XZ direction. The two-dimensional translation stage can be moved at the micrometer level by computer control. The measuring device for the two-dimensional single-wavelength radiance of the LSP light source is disposed on the three-dimensional displacement stage and moves at the micrometer level in the XYZ directions with the three-dimensional translation stage, thereby realizing the change of distance and position of the standard halogen lamp light source, the standard LSP light source, and the light source under test relative to the front-end lens assembly. The standard halogen lamp light source is a standard radiance light source for calibrating the transfer coefficient of different field-of-view apertures, and the standard LSP light source is a tunable standard radiance light source for calibrating the correlation coefficient in the linear function between the gray value of the photosensitive element and the radiance.

[0085] In this embodiment of the invention, the light source under test passes through a front-end lens assembly consisting of a bandpass filter F1, a first lens L1, and a second lens L2. A beam of light reflected by a beam splitter S1 passes through a neutral density filter F2 and is imaged onto a first photosensitive element C1, thus recording the two-dimensional intensity information of the light source under test. Another beam of light passes through the beam splitter S1 and is imaged onto a field-view aperture assembly H1 (H1 includes a focusing panel and a field-view aperture, wherein the parameters of the field-view aperture can be 1 mm and 25 μm). The image on the field-view aperture assembly H1 is reflected by the beam splitter S1 and passes through an observation lens assembly consisting of a fifth lens L5 and a sixth lens L6, and is imaged onto a second photosensitive element C2, thus achieving focusing and alignment. The light passing through the field-view aperture assembly H1 passes through a rear-end lens assembly consisting of a third lens L3 and a fourth lens L4, and the radiant flux is received by a photodetector PD.

[0086] Among them, the standard halogen lamp light source refers to the standard radiance light source, which is a standard light source used for calibrating and standardizing radiance. Its purpose is to provide a traceable, stable, and known radiance value benchmark. It has characteristics such as high radiant energy, good surface uniformity, and excellent angular characteristics (Lambertian properties). The standard LSP light source refers to the tunable standard radiance light source, which is a standard light source used for calibrating the correlation coefficient in the linear function between the gray value of an image sensor pixel and radiance. Its purpose is to provide a radiance benchmark with high radiance, adjustability, traceability, and stability.

[0087] like Figure 4 As shown, embodiments of the present invention also provide a method for measuring the two-dimensional single-wavelength radiance of an LSP light source, including:

[0088] The light beam emitted by the light source under test is passed through a bandpass filter to form narrowband light;

[0089] The narrowband light passes through the front-end lens assembly and is reflected and transmitted through the beam splitter cube to form a reflected beam and a transmitted beam.

[0090] The transmitted light beam is focused onto the field stop assembly. The light beam reflected by the focusing panel of the field stop assembly is reflected by the beam splitter cube and then focused onto the second photosensitive element by the observation lens assembly.

[0091] Adjust the distance and position of the light source under test relative to the front lens assembly so that the light beam reflected by the focusing panel of the field stop assembly from the light source under test is imaged on the second photosensitive element to meet the constraint conditions, thereby achieving preliminary focusing and alignment of the light source under test.

[0092] Move the field stop assembly so that the beam transmitted by the beam splitter cube converges to the field stop of the field stop assembly. The beam transmitted through the field stop is then converged to the photodetector by the rear lens assembly.

[0093] Adjust the distance and position of the light source under test relative to the front lens assembly to make the photodetector reach the maximum response value, thereby achieving precise focusing and alignment of the light source under test;

[0094] The reflected light beam is focused onto the first photosensitive element through a neutral density filter, and the two-dimensional intensity information of the light source under test is recorded. Based on the linear relationship between the gray value of the first photosensitive element and the radiance, the two-dimensional single-wavelength radiance of the light source under test is obtained.

[0095] In this embodiment of the invention, the method further includes the following steps before the above method:

[0096] The light beam emitted by a standard halogen lamp light source passes through the bandpass filter to form halogen narrowband light;

[0097] The halogen narrowband light is passed through the front lens assembly, and the beam transmitted from the beam splitter cube is converged to the focusing panel of the field stop assembly.

[0098] The light beam reflected by the focusing panel is reflected by the beam splitter cube, and then converged by the observation lens assembly to the second photosensitive element.

[0099] Adjusting the distance and position of the standard halogen lamp light source relative to the front lens assembly, so that the light beam reflected by the standard halogen lamp light source through the focusing panel forms an image on the second photosensitive element that meets the constraint conditions, thereby achieving focusing and alignment of the standard halogen lamp light source;

[0100] Move the field stop assembly to converge the beam transmitted by the beam splitter cube to the field stop of the field stop assembly;

[0101] The light beam transmitted through the field stop is focused by the rear lens assembly onto the photodetector to record the radiant flux information of the standard halogen lamp light source.

[0102] Based on the radiant flux information and the radiant brightness information of the standard halogen lamp light source, the transfer coefficients of different field stops in the field stop assembly are determined.

[0103] In this embodiment of the invention, the method further includes: calculating the radiance information of the light source under test based on the transfer coefficient and the radiant flux information of the light source under test: L 被测 =K 0.025 V 被测 ;

[0104]

[0105] L 卤素 It is the radiant value of a standard halogen lamp light source at the center wavelength λ of the bandpass filter; V 卤素 It is the response value of a standard halogen lamp light source within the passband of the bandpass filter; L 被测 V is the radiance value of the light source being measured at the center wavelength λ of the bandpass filter; 被测 S1 is the response value of the light source under test within the passband of the bandpass filter, and S2 is the area of ​​the 1mm diameter field stop used to measure the standard halogen lamp light source; S 0.025 It is used to measure the area of ​​a 25μm diameter field stop of the light source under test, wherein the response value is the current or voltage value received by the photodetector, which is proportional to the radiant flux of the light beam transmitted through the field stop and the rear lens assembly; the passband range is related to the center wavelength λ and bandwidth λ of the bandpass filter. FWHM related.

[0106] In this embodiment of the invention, the method further includes, prior to:

[0107] The light beam emitted by the standard LSP light source passes through an adjustable step neutral density filter and then through the bandpass filter to form LSP narrowband light;

[0108] The LSP narrowband light passes through the front-end lens assembly and is reflected and transmitted through the beam splitter cube to form a reflected beam and a transmitted beam.

[0109] The transmitted light beam is focused onto the field stop assembly. The light beam reflected by the focusing panel of the field stop assembly is reflected by the beam splitter cube and then focused onto the second photosensitive element by the observation lens assembly.

[0110] Adjust the distance and position of the standard LSP light source relative to the front lens assembly so that the light beam reflected by the standard LSP light source through the focusing panel images the second photosensitive element to meet the constraint conditions, thereby achieving the initial focusing and alignment of the standard LSP light source.

[0111] Move the field stop assembly to converge the beam transmitted by the split cube to the field stop of the field stop assembly;

[0112] The light beam transmitted through the field stop is focused onto the photodetector by the rear lens assembly;

[0113] Adjust the distance and position of the standard LSP light source relative to the front-end lens assembly to enable the photodetector to reach its maximum response value, achieve precise focusing and alignment of the standard LSP light source, and record the radiant flux information of the standard LSP light source.

[0114] Based on the transfer coefficient of the field stop, the single-point single-wavelength radiance of the standard LSP light source is obtained.

[0115] The reflected light beam is focused onto the first photosensitive element through the neutral density filter to record the two-dimensional intensity information of the standard LSP light source.

[0116] In this embodiment of the invention, the method further includes:

[0117] By combining the standard LSP light source with an adjustable stepped neutral density filter, a tunable standard radiance light source is constructed. The maximum average gray value and corresponding radiance within the corresponding field stop region are recorded in the two-dimensional intensity information at different transmittance levels. This yields the gray value DN and radiance L of the first photosensitive element. c The linear relationship satisfied is:

[0118]

[0119] Where t is the exposure time of the image sensor; G is the gain coefficient of the image sensor; η is the quantum efficiency of the photosensitive element; k is the linearity coefficient of the optical system; L c A is the radiance at the center wavelength of the bandpass filter; E is the pixel area of ​​the image sensor; c It is the photon energy at the center wavelength of the bandpass filter; DN (digital number) is the grayscale value of the photosensitive element; DN dark It is the dark noise of the image sensor, λ FWHM It is the bandwidth of the bandpass filter.

[0120] In this embodiment of the invention, the transfer coefficient K of different field stops is determined by measuring the radiant flux information of a standard halogen lamp light source. The specific process includes:

[0121] In this embodiment of the invention, the selected standard halogen lamp light source is a halogen lamp whose output is scattered by the ground glass of the collimation system. Its radiance value at the center wavelength of the bandpass filter can be traced back to its source. A crosshair is installed at the front end of the standard halogen lamp light source output. A three-dimensional translation stage is moved to adjust the distance and position of the standard halogen lamp light source relative to the front lens assembly, moving the standard halogen lamp light source to near twice the effective focal length of the front lens assembly (the equivalent object distance has taken into account the influence of medium refraction). Through the second photosensitive element C2, the image of the standard halogen lamp light source on the focusing panel of the field stop assembly H1 is observed, and the distance and position of the standard halogen lamp light source and the front lens assembly are finely adjusted until the standard halogen lamp light source forms an image that meets the constraint conditions through the center of the focusing panel of the field stop assembly H1 (so that the crosshair forms a clear image on the second photosensitive element C2, and the intersection of the crosshair is located at the center of the photosensitive element), thus realizing the focusing and alignment of the standard halogen lamp light source. Then remove the crosshairs at the front end of the standard halogen lamp light source, and then move the field stop assembly H1 so that the center of the 1mm diameter field stop is located at the center of the photosensitive element. The beam of light projected onto the field stop is focused onto the photodetector PD by the rear lens assembly. The light radiation collected by the photodetector PD is converted by photoelectric conversion and read by the galvanometer.

[0122] When it is not possible to directly measure the transfer coefficient corresponding to a field stop with a diameter of 25μm, the transfer coefficient K1 of a field stop with a diameter of 1mm can be measured, as shown in the following formula:

[0123]

[0124] Among them, L 卤素 Let V1 be the radiance of a standard halogen lamp light source at the center wavelength of the bandpass filter, and V2 be the response value received by the photodetector after the standard halogen lamp light source passes through a 1mm diameter field stop and the rear lens assembly consisting of lenses L3 and L4. According to the radiance formula L = Φ / AΩ, the transfer coefficient K corresponding to a 25μm diameter field stop is calculated without changing the solid angle and only altering the field stop size. 0.025 The following relationship will be satisfied

[0125]

[0126] Where S1 is the area of ​​a field stop with a diameter of 1 mm; S 0.025 It is the area of ​​the field stop with a diameter of 25μm.

[0127] In this embodiment of the invention, the single-point, single-wavelength radiance of the light source under test is calculated based on the transfer coefficient and the radiant flux information of the light source under test:

[0128] L 被测 =K 0.025 V 被测

[0129] V 被测 It is the response value of the measured light source within the passband of the bandpass filter; L 被测 K is the radiance value of the light source being measured at the center wavelength λ of the bandpass filter; 0.025 It is used to measure the transfer coefficient of a 25μm diameter field stop of the light source under test. The response value is the current or voltage value received by the photodetector, which is proportional to the radiant flux of the light beam transmitted through the field stop and the subsequent lens assembly. The passband range is related to the center wavelength λ and bandwidth λ of the bandpass filter. FWHM related.

[0130] In this embodiment of the invention, the correlation coefficient in the linear function between the radiance and grayscale value of the first photosensitive element is calibrated by measuring the radiance and two-dimensional grayscale image of a standard LSP light source at different transmittances. The specific process includes:

[0131] exist Figure 2 In the two-dimensional single-wavelength radiance measurement device for an LSP light source shown, adjustable step neutral density filters with different transmittances are placed in front of a standard LSP light source. The three-dimensional translation stage is moved to adjust... Figure 2 The distance and position of the standard LSP light source relative to the front-end lens assembly are adjusted so that the intensity center of the standard LSP light source spot is located at the center of the second photosensitive element C2. Under a preset exposure time, the maximum grayscale of the standard LSP light source spot will not increase and will remain unsaturated, i.e., it will not exceed the bit depth of the second photosensitive element C2 (typically 8-bit or 12-bit). At this point, the light spot is "spindle-shaped," achieving initial focusing and alignment of the standard LSP light source (also applicable to constraints on the light source under test). Moving the field-of-view aperture assembly to a 25μm field-of-view aperture further adjusts the distance and position of the standard LSP light source relative to the front-end lens assembly, allowing the photodetector to reach its maximum response value, achieving precise focusing and alignment of the standard LSP light source. Based on the maximum response value of the photodetector and the transfer coefficient K of the 25μm diameter field-of-view aperture... 0.025The single-point, single-wavelength radiance of a standard LSP light source paired with adjustable step neutral density filters of varying transmittance was obtained. Two-dimensional intensity information of the standard LSP light source was acquired using the first photosensitive element C1 (the maximum grayscale value reached unsaturated and was within 90% of the maximum bit depth of the photosensitive element). The maximum average grayscale value within the corresponding field stop region in the standard LSP light source image was calculated using software.

[0132] The grayscale value of the first photosensitive element C1 and the radiance of the light source under test satisfy the following relationship:

[0133]

[0134] Where t is the exposure time of the image sensor; G is the gain coefficient of the image sensor; η is the quantum efficiency of the photosensitive element; k is the linearity coefficient of the optical system; L c A is the radiance at the center wavelength of the bandpass filter; E is the pixel area of ​​the image sensor; c It is the photon energy at the center wavelength of the bandpass filter; DN (digital number) is the grayscale value of the photosensitive element; DN dark It is the dark noise of the image sensor, λ FWHM It is the bandwidth of the bandpass filter.

[0135] Wherein, the camera exposure time t and the gain coefficient G are known or obtainable quantities. The maximum average gray value DN in the corresponding field stop region of the image of a standard LSP light source with different radiance is fitted with the product GtL of the corresponding radiance and camera parameters. c The unknown quantity DN can be obtained. dark and ηAkλ FWHM / E c Given the camera parameters, we can then obtain a linear function expression between the grayscale value and radiance of the photosensitive element C1.

[0136] In this embodiment of the invention, the two-dimensional single-wavelength radiance of the light source under test is calculated based on the linear function and the two-dimensional intensity information of the light source under test.

[0137] In this embodiment of the invention, a neutral density filter F2 is used to reduce the irradiance of the LSP light source incident on the target surface of the first photosensitive element C1 (which may also be an image sensor), thereby preventing saturation or damage.

[0138] In this embodiment of the invention, an adjustable step neutral density filter F3 with different transmittance is selected and fixed at the light output port of a standard LSP light source to simulate a tunable standard radiance light source in order to calibrate the correlation coefficient in the linear function.

[0139] The measurement device and method for two-dimensional single-wavelength radiance of LSP light sources provided in this invention provides an important experimental basis for the study of internal electronic parameters of plasma based on optical emission spectroscopy diagnosis. By combining the two-dimensional intensity information of LSP light sources obtained by image sensing elements with a single-point single-wavelength radiance measurement system, the two-dimensional single-wavelength radiance of LSP light sources can be measured. This not only effectively meets the measurement requirements for two-dimensional single-wavelength radiance of ultra-small, high-brightness light sources such as LSP light sources, but also achieves accurate interception of light source intensity, avoiding measurement errors.

[0140] Example

[0141] Combination Figure 5 and Figure 6 This embodiment describes the process of measuring radiance using the aforementioned measurement device and method for two-dimensional single-wavelength radiance of LSP light sources:

[0142] In this embodiment, L1 and L2 are both achromatic lenses with an effective focal length of 200mm, L3 and L4 are both achromatic lenses with an effective focal length of 30mm, and L5 and L6 are both achromatic lenses with an effective focal length of 100mm. The diameter of all lenses in this embodiment is 1 inch, and S1 is a semi-transparent, semi-reflective (R / T = 50:50) beam-splitting cubic lens. In this embodiment, the barrel wall of the front surface of lens L1 is an aperture stop, which limits the maximum aperture of light emitted from a point on the optical axis. Therefore, the constraint of the measuring device on the solid angle of the measured light source is mainly determined by the effective focal length of the front lens assembly composed of lenses L1 and L2 and the width of the barrel wall fixing lens L1.

[0143] In other embodiments, if the diameters and focal lengths of L1 and L2 are inconsistent, the solid angle of the measuring device relative to the measured light source is determined by the spatial position and size of the incident pupil in the front-end lens assembly composed of the bandpass filter F1, the beam splitter cube S1, and the L1 and L2 lenses. Furthermore, the object-side NA (numerical aperture) of the front-end lens assembly composed of the L1 and L2 lenses is kept as small as possible to minimize the shift in the passband range of the bandpass filter caused by different incident angles.

[0144] In this embodiment, the aperture stop of the rear lens assembly composed of lenses L3 and L4 is located on the barrel wall of the front surface of lens L3. Therefore, the effective focal length of lens L3 is less than that of lens L2.

[0145] In other embodiments, if the specifications of the L1, L2, L3, and L4 lenses are not the same, the limiting condition is that the image-side aperture angle limited by the exit pupil of the front lens assembly composed of the bandpass filter F1, the beam splitter cube S1, and the L1 and L2 lenses should be smaller than the object-side aperture angle limited by the entrance pupil of the rear lens assembly composed of the L3 and L4 lenses.

[0146] In this embodiment, twice the effective focal length of the L5 and L6 lens groups is greater than the reflected optical path length inside the beam splitter cube. Furthermore, the object-side numerical aperture (NA) of the observation lens assembly composed of the L5 and L6 lenses is maximized to increase the amount of light entering the image sensor.

[0147] As described above, the relationship between the single-point, single-wavelength radiance of the standard LSP light source obtained by the measuring device and the gray value collected by the first photosensitive element C1.

[0148]

[0149] According to the above formula, it can be seen that in other parameters (ηAkλ) FWHM / E c At a given time, the product of the image sensor's grayscale value (DN) and the radiance at a specific wavelength (the center wavelength of the bandpass filter), the image sensor's gain coefficient, and the exposure time (GtL) is... c They satisfy a linear relationship.

[0150] The measurement device in this embodiment uses an interference-type narrowband filter with a center wavelength of 440nm and a full width at half maximum (FWHM) of 10nm, and the gain coefficient G of the first photosensitive element C1 is 1.

[0151] The correlation coefficient in the linear function is calibrated, thereby enabling the transfer of single-point single-wavelength radiance to two-dimensional single-wavelength radiance.

[0152] This embodiment uses a standard LSP light source as the calibration light source, and employs adjustable step neutral density filters F3 with different transmittance (T = 90%, 80%, 70%, 60%, 50%, 40%, 30%, 20%, 10%, 5%) and the case without filters to simulate light sources with different radiance. The maximum single-point, single-wavelength radiance of the standard LSP light source and the plasma image acquired by the first photosensitive element C1 are obtained using this measuring device. The maximum average gray value within the corresponding field-of-view aperture area is calculated from the plasma image. Figure 6 Data points in A. Figure 6In B, 6C, and 6D, the horizontal axis represents the product of radiance and exposure time as the independent variable, and the vertical axis represents the image sensor response value (grayscale value) at the corresponding exposure time. Under different exposure times, the coefficients of the labeled fitted linear function are approximately the same, and R0... 2 It is approximately 1, where R 2 R is used to describe the degree of agreement between experimental data and the fitted function. 2 The closer the value is to 1, the higher the degree of agreement. 2 The closer the correlation coefficient is to 0, the lower the degree of agreement. This demonstrates that the above formula can be used to calibrate the correlation coefficient.

[0153] It should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", and "outer" 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 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 this application.

[0154] 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 one or more of that feature. In the description of this application, "multiple" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0155] In this application, unless otherwise expressly 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 direct connection or an indirect connection through an intermediate medium. Those skilled in the art can understand the specific meaning of the above terms in this application according to the specific circumstances.

[0156] Obviously, those skilled in the art can make various modifications and variations to this application without departing from the spirit and scope of this application. Therefore, if such modifications and variations fall within the scope of the claims of this application and their equivalents, this application also intends to include such modifications and variations.

[0157] Although the invention has been described with reference to a limited number of embodiments, those skilled in the art will understand from the foregoing description that other embodiments are conceivable within the scope of the invention described herein. Furthermore, it should be noted that the language used in this specification has been chosen primarily for readability and instructional purposes, and not for the purpose of interpreting or limiting the subject matter of the invention. Therefore, many modifications and variations will be apparent to those skilled in the art without departing from the scope and spirit of the appended claims. The disclosure of the invention is illustrative and not restrictive, and the scope of the invention is defined by the appended claims.

Claims

1. A device for measuring the two-dimensional single-wavelength radiance of an LSP light source, characterized in that it comprises: Comprise: Band-pass filter, beam splitting cube, neutral density filter, front-end lens assembly, rear-end lens assembly, observation lens assembly, first photosensitive element, second photosensitive element, photodetector and field stop assembly; The light beam emitted by the measured light source passes through the band-pass filter to form narrow-band light; The narrow-band light passes through the front-end lens assembly and is reflected and transmitted by the beam splitting cube to form reflected light beam and transmitted light beam; The reflected light beam passes through the neutral density filter and converges to the first photosensitive element to record the two-dimensional intensity information of the measured light source; The transmitted light beam converges to the field stop assembly, and the light beam transmitted by the field stop assembly converges to the photodetector through the rear-end lens assembly to record the radiant flux information of the measured light source; The transmitted light beam converges to the field stop assembly, and the light beam reflected by the field stop assembly is reflected by the beam splitting cube and then converges to the second photosensitive element through the observation lens assembly to realize focusing and alignment of the measured light source.

2. The apparatus of claim 1, wherein, The front-end lens assembly comprises a first lens and a second lens arranged in sequence along the light beam propagation direction, and the measured light source is arranged at twice the effective focal length of the front-end lens assembly; the field stop assembly is arranged at twice the effective focal length of the front-end lens assembly; the first photosensitive element is arranged at twice the effective focal length of the front-end lens assembly.

3. The apparatus of claim 1 or 2, wherein, The rear-end lens assembly comprises a third lens and a fourth lens arranged in sequence along the light beam propagation direction, and the field stop assembly is arranged at twice the effective focal length of the rear-end lens assembly; the photodetector is arranged at twice the effective focal length of the rear-end lens assembly.

4. The apparatus of claim 3, wherein, The observation lens assembly comprises a fifth lens and a sixth lens arranged in sequence along the light beam propagation direction, and the field stop assembly is arranged at twice the effective focal length of the observation lens assembly; the second photosensitive element is arranged at twice the effective focal length of the observation lens assembly.

5. The apparatus of claim 1, wherein, The field stop assembly comprises a focusing panel and one or more field stops.

6. The apparatus of claim 1, wherein, Also include: Standard halogen lamp light source, standard LSP light source, one-dimensional translation stage, two-dimensional translation stage and three-dimensional displacement stage, the standard halogen lamp light source, the standard LSP light source and the measured light source are arranged on the one-dimensional translation stage and move with the one-dimensional translation stage; the field stop assembly is arranged on the two-dimensional translation stage and moves with the two-dimensional translation stage; the two-dimensional single-wavelength radiant luminance measurement device facing the LSP light source is arranged on the three-dimensional displacement stage and moves with the three-dimensional translation stage; wherein the standard halogen lamp light source is a standard radiant luminance light source for calibrating different field stop transfer coefficients, and the standard LSP light source is a tunable standard radiant luminance light source for calibrating the correlation coefficient in the linear function between the gray value of the photosensitive element and the radiant luminance.

7. A method for measuring the two-dimensional single-wavelength radiance of an LSP light source, characterized in that, Comprise: Make the light beam emitted by the measured light source pass through the band-pass filter to form narrow-band light; Make the narrow-band light pass through the front-end lens assembly and be reflected and transmitted by the beam splitting cube to form reflected light beam and transmitted light beam; The transmitted light beam is converged to the field stop assembly, the light beam reflected by the focusing panel of the field stop assembly is reflected by the beam splitting cube again, and then converged to the second photosensitive element through the observation lens assembly; The distance and position of the measured light source relative to the front lens assembly are adjusted so that the light beam reflected by the focusing panel of the field stop assembly on the second photosensitive element forms an image satisfying a constraint condition, thereby achieving preliminary focusing and alignment of the measured light source; The field stop assembly is moved, and the light beam transmitted by the beam splitting cube is converged to the field stop of the field stop assembly, and the light beam transmitted by the field stop is converged to the photodetector through the rear lens assembly; The distance and position of the measured light source relative to the front lens assembly are adjusted so that the photodetector reaches a maximum response value, thereby achieving accurate focusing and alignment of the measured light source; The reflected light beam is converged to the first photosensitive element through the neutral density filter, and two-dimensional intensity information of the measured light source is recorded, and two-dimensional single-wavelength radiant brightness of the measured light source is obtained according to a linear relationship between a gray value of the first photosensitive element and radiant brightness.

8. The method of claim 7, wherein, The method further comprises the following steps: The light beam emitted by the standard halogen lamp source passes through the band-pass filter to form halogen narrow-band light; The halogen narrow-band light passes through the front lens assembly, and the light beam transmitted by the beam splitting cube is converged to the focusing panel of the field stop assembly; The light beam reflected by the focusing panel passes through the beam splitting cube again, and then converges to the second photosensitive element through the observation lens assembly; The distance and position of the standard halogen lamp source relative to the front lens assembly are adjusted so that the light beam reflected by the focusing panel on the second photosensitive element forms an image satisfying a constraint condition, thereby achieving focusing and alignment of the standard halogen lamp source; The field stop assembly is moved, and the light beam transmitted by the beam splitting cube is converged to the field stop of the field stop assembly; The light beam transmitted by the field stop passes through the rear lens assembly and converges to the photodetector, and radiant flux information of the standard halogen lamp source is recorded; The transfer coefficients of different field stops in the field stop assembly are determined according to the radiant flux information and radiant brightness information of the standard halogen lamp source.

9. The method of claim 8, wherein, The method further comprises the following steps: The light beam emitted by the standard LSP light source passes through the adjustable step neutral density filter and the band-pass filter to form LSP narrow-band light; The LSP narrow-band light passes through the front lens assembly and is reflected and transmitted by the beam splitting cube to form reflected light beam and transmitted light beam; The transmitted light beam is converged to the field stop assembly, the light beam reflected by the focusing panel of the field stop assembly is reflected by the beam splitting cube again, and then converges to the second photosensitive element through the observation lens assembly; The distance and position of the standard LSP light source relative to the front lens assembly are adjusted so that the light beam reflected by the focusing panel on the second photosensitive element forms an image satisfying a constraint condition, thereby achieving preliminary focusing and alignment of the standard LSP light source; moving the field stop assembly to make the light beams transmitted by the beam splitting cube converge to the field stop of the field stop assembly; making the light beams transmitted by the field stop converge to the photodetector through the rear end lens assembly; adjusting the distance and position of the standard LSP light source relative to the front end lens assembly to make the photodetector reach the maximum response value, realizing accurate focusing and alignment of the standard LSP light source, and recording the radiant flux information of the standard LSP light source; obtaining the single-point single-wavelength radiant luminance of the standard LSP light source according to the transfer coefficient of the field stop; making the reflected light beams converge to the first photosensitive element through the neutral density filter, and recording the two-dimensional intensity information of the standard LSP light source.

10. The method of claim 8, wherein, Further comprising: calculating the measured light source single-point single-wavelength radiant luminance information L according to the transfer coefficient and the radiant flux information of the measured light source 被测 = KV 被测 ; wherein L 卤素 is the radiation luminance value of the standard halogen lamp light source corresponding to the center wavelength λ of the band-pass filter; V 卤素 is the response value of the standard halogen lamp light source corresponding to the passband range of the band-pass filter; L 被测 is the radiation luminance value of the measured light source corresponding to the center wavelength λ of the band-pass filter; V 被测 is the response value of the measured light source corresponding to the passband range of the band-pass filter; S 大 is the area of the large field stop for measuring the standard halogen lamp light source; S 小 is the area of the small field stop for measuring the measured light source, wherein the response value is the current value or voltage value received by the photodetector, which is directly proportional to the radiant flux value of the light beam passing through the rear-end lens assembly after being transmitted through the field stop; the passband range is related to the center wavelength λ and the bandwidth λ FWHM of the band-pass filter.

11. The method of claim 9, wherein, Further comprising: The standard LSP light source is combined with an adjustable step neutral density filter to build a tunable standard radiation brightness light source, and the maximum average gray value in the corresponding field stop area and the corresponding radiation brightness in the two-dimensional intensity information under different transmittances are recorded to obtain the first photosensitive element gray value DN and the radiation brightness L c The linear relationship is satisfied: where t is the exposure time of the image sensor; G is the gain coefficient of the image sensor; η is the quantum efficiency of the light-sensitive element; k is the linear coefficient of the optical system; L c is the radiance at the center wavelength of the band-pass filter; A is the area of the image sensor pixel; E c is the photon energy at the center wavelength of the band-pass filter; DN is the gray value of the light-sensitive element; DN dark is the dark noise of the image sensor, λ FWHM is the bandwidth of the band-pass filter.

Images