WO2024065898A1 - 一种基于空间成像系统的高精度光斑测试系统及方法 - Google Patents

一种基于空间成像系统的高精度光斑测试系统及方法 Download PDF

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WO2024065898A1
WO2024065898A1 PCT/CN2022/126157 CN2022126157W WO2024065898A1 WO 2024065898 A1 WO2024065898 A1 WO 2024065898A1 CN 2022126157 W CN2022126157 W CN 2022126157W WO 2024065898 A1 WO2024065898 A1 WO 2024065898A1
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lens
beam splitter
sample
image
light
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PCT/CN2022/126157
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English (en)
French (fr)
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陈力锋
胡紫阳
颜扬捷
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江苏铌奥光电科技有限公司
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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
    • G01B11/00—Measuring arrangements characterised by the use of optical techniques
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
    • G01B11/00—Measuring arrangements characterised by the use of optical techniques
    • G01B11/26—Measuring arrangements characterised by the use of optical techniques for measuring angles or tapers; for testing the alignment of axes
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01M—TESTING STATIC OR DYNAMIC BALANCE OF MACHINES OR STRUCTURES; TESTING OF STRUCTURES OR APPARATUS, NOT OTHERWISE PROVIDED FOR
    • G01M11/00—Testing of optical apparatus; Testing structures by optical methods not otherwise provided for
    • G01M11/02—Testing optical properties
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01M—TESTING STATIC OR DYNAMIC BALANCE OF MACHINES OR STRUCTURES; TESTING OF STRUCTURES OR APPARATUS, NOT OTHERWISE PROVIDED FOR
    • G01M11/00—Testing of optical apparatus; Testing structures by optical methods not otherwise provided for
    • G01M11/02—Testing optical properties
    • G01M11/0207—Details of measuring devices
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B27/00—Optical systems or apparatus not provided for by any of the groups G02B1/00 - G02B26/00, G02B30/00
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B27/00—Optical systems or apparatus not provided for by any of the groups G02B1/00 - G02B26/00, G02B30/00
    • G02B27/48—Laser speckle optics

Definitions

  • the present invention belongs to the technical field of optics and optical communications, and in particular relates to a high-precision spot testing system and method for a space imaging system.
  • the actual exit spot size has no direct relationship with the size of the exit end face, which means that the exact size of the exit spot cannot be determined simply by observing the near-field spot and the end face, and there is currently a lack of accurate measurement solutions.
  • the present invention provides a high-precision spot testing system and method based on a spatial imaging system, which is widely applicable to measuring the spot size of micron-scale light-emitting elements.
  • a high-precision spot testing method based on a space imaging system comprises the following steps:
  • Step 1 Choose appropriate parameters
  • a high-power objective lens, a Fourier lens and an imaging lens are selected whose parameters satisfy 2f 0 tan(sin -1 NA)f C /f F ⁇ L X , 2f 0 tan(sin -1 NA)f C /f F ⁇ L Y , wherein f O is the equivalent focal length of the high-power objective lens, NA is the numerical aperture of the high-power objective lens, f C is the focal length of the imaging lens, f F is the focal length of the Fourier lens, L X is the horizontal size of the CCD camera, and L Y is the vertical size of the CCD camera, so that the maximum diameter of the image on the back focal plane of the objective lens is limited within the receiving range of the CCD; the real image magnification (f C ⁇ f F )/(f I ⁇ f O ) makes the projected area of the sample to be measured on the CCD after magnification smaller than the CCD area;
  • Step 2 Install and calibrate the test system
  • a test system is constructed, wherein the optical fiber is connected to the light source, the light source focusing lens and the beam splitter are arranged in sequence from near to far on the optical path introduced by the optical fiber, the high-magnification objective lens and the six-axis stage are arranged in the reflected light path of the beam splitter, the Fourier lens, the secondary focusing lens, the imaging lens, the variable neutral density filter, and the CCD camera are arranged in sequence from near to far on the transmitted light path of the beam splitter, and the CCD camera is connected to the computer; the silver reflector is loaded onto the six-axis stage, and the direction of the optical path is in the order of the optical fiber, the light source focusing lens, the beam splitter, the high-magnification objective lens, the silver reflector, the high-magnification objective lens, the beam splitter, the Fourier lens, the secondary focusing lens, the imaging lens, the variable neutral density filter, and the CCD camera; the distance between the stage and the objective lens is adjusted so that the image presented by the computer is a
  • a test system is constructed, in which a Fourier lens is not provided; an optical fiber is connected to a light source, a light source focusing lens and a beam splitter are arranged in sequence from near to far on the optical path introduced by the optical fiber, a high-magnification objective lens and a six-axis stage are arranged in the reflected optical path of the beam splitter, an imaging lens, a variable neutral density filter, and a CCD camera are arranged in sequence from near to far on the transmitted optical path of the beam splitter, and the CCD camera is connected to a computer; a silver reflector is loaded onto the six-axis stage, and the optical path direction is in the order of optical fiber, light source focusing lens, beam splitter, high-magnification objective lens, silver reflector, high-magnification objective lens, beam splitter, imaging lens, variable neutral density filter, and CCD camera; the distance between the stage and the objective lens is adjusted so that the image presented by the computer is a focused image on the surface of the reflector; a Fourier lens is
  • the sample to be tested is loaded onto the sample stage, and the test system is built.
  • the optical fiber is connected to the light source.
  • the light source focusing lens, Kohler lens, and beam splitter are arranged in sequence from near to far on the optical path introduced by the optical fiber.
  • the high-magnification objective lens and the six-axis stage are arranged in the reflected light path of the beam splitter.
  • the Fourier lens, secondary focusing lens, imaging lens, variable neutral density filter, and CCD camera are arranged in sequence from near to far on the transmitted light path of the beam splitter.
  • the variable diaphragm is arranged between the Fourier lens and the secondary focusing lens. The light path passes through the aperture on the variable diaphragm, and the CCD camera is connected to the computer.
  • the direction of the light path is in the order of the optical fiber, the light source focusing lens, the Kohler lens, the beam splitter, the high-magnification objective lens, the sample to be tested, the high-magnification objective lens, the beam splitter, the Fourier lens, the variable diaphragm, the secondary focusing lens, the imaging lens, the variable neutral density filter, and the CCD camera.
  • the method comprises the following steps: placing an image lens, a variable neutral density filter, and a CCD camera in the order of: adjusting the distance between the stage and the objective lens so that the image presented by the computer is a real image reflected from the sample surface; locating the vicinity of the light-emitting portion of the sample through the real image of the reflection; making the sample self-luminous, removing the beam splitter in the light path, and changing the direction of the light path to the sample to be tested, a high-magnification objective lens, a Fourier lens, a variable aperture, a secondary focusing lens, an imaging lens, a variable neutral density filter, and a CCD camera; further moving the sample so that the position of the light spot seen by the CCD camera is centered and focused; changing the size of the variable aperture so that the imaging range is limited to only the vicinity of the light spot; removing the secondary focusing lens, and adjusting the variable neutral density filter so that the maximum brightness of the image obtained by the computer is the same as that of the calibration image; recording the image and measuring the
  • the sample to be tested is loaded onto the sample stage, and the Fourier lens is not set at this time;
  • the optical fiber is connected to the light source, and the light source focusing lens and the beam splitter are arranged in sequence from near to far on the optical path introduced by the optical fiber, the high-magnification objective lens and the six-axis stage are arranged in the reflected light path of the beam splitter, the imaging lens, the variable neutral density filter, and the CCD camera are arranged in sequence from near to far on the transmitted light path of the beam splitter, and the CCD camera is connected to the computer;
  • the direction of the light path is in the order of the optical fiber, the light source focusing lens, the beam splitter, the high-magnification objective lens, the sample to be tested, the high-magnification objective lens, the beam splitter, the imaging lens, the variable neutral density filter, and the CCD camera.
  • the method comprises the following steps: adjusting the distance between the stage and the objective lens so that the image presented on the computer is a real image reflected from the sample surface; locating the vicinity of the light-emitting part of the sample through the real image of the reflection; making the sample self-luminous, removing the beam splitter in the light path, and changing the direction of the light path to the sample to be tested, the high-magnification objective lens, the imaging lens, the variable neutral density filter, and the CCD camera; further moving the sample so that the position of the light spot seen by the CCD camera is centered and focused; adding a Fourier lens between the beam splitter and the imaging lens; adjusting the variable neutral density filter so that the maximum brightness of the image obtained by the computer is the same as that of the calibration image; recording the image and measuring the width of the image at the brightness 1/e 2 in the horizontal direction and in the vertical direction, which is X 2 pixels and Y 2 pixels respectively;
  • the horizontal divergence angle of the sample is calculated to be:
  • the corresponding horizontal diameter of the Gaussian spot is
  • the vertical divergence angle is
  • the corresponding vertical diameter of the Gaussian spot is
  • the method further comprises the following step: measuring the far-field image size of the sample to be tested according to the intensity distribution diagram of the Fourier image of the sample.
  • the present invention also provides a high-precision spot test system based on a space imaging system, including a broadband light source, an optical fiber, a light source focusing lens, a beam splitter, a high-magnification objective lens, a six-axis stage, a Fourier lens, an imaging lens, a variable neutral density filter, a CCD camera, and a computer;
  • the broadband light source is connected to the optical fiber, the light source focusing lens and the beam splitter are arranged in sequence from near to far on the optical path introduced by the optical fiber, the high-magnification objective lens and the six-axis stage are arranged in the reflected light path of the beam splitter, the Fourier lens, the imaging lens, the variable neutral density filter, and the CCD camera are arranged in sequence from near to far on the transmitted light path of the beam splitter, and the CCD camera is connected to the computer;
  • the optical fiber introduces the light of the broadband light source into the system; the light source focusing lens is used to collimate the light emitted by the broadband light source via the optical fiber; the beam splitter is used to merge the reflected light path and the transmitted light path into one path in front of the objective lens; the high-magnification objective lens is used to collect light from all emission directions of the sample to be tested; the six-axis stage is used to load the sample to be tested; the Fourier lens is used to focus the rear focal plane image behind the objective lens, perform optical Fourier transform on the near-field light spot, and obtain the corresponding far-field image; the imaging lens is used to enable a focused real image to be formed on the CCD camera; the variable neutral density filter is used to reduce the amount of light passing through; and the computer is used to receive the CCD camera imaging and process it.
  • it also includes a Kohler lens, a variable aperture and a secondary focusing lens;
  • the Kohler lens is arranged between the light source focusing lens and the beam splitter, the variable iris and the secondary focusing lens are arranged between the Fourier lens and the imaging lens, and are located on the transmission light path of the beam splitter, wherein the variable iris is located at the overlap of the rear focus of the Fourier lens and the front focus of the secondary focusing lens, and the transmission light path passes through the aperture on the variable iris;
  • the Kohler lens is used to form a Kohler illumination system in front of the objective lens to increase the illumination range of the objective lens; the variable diaphragm is used to filter out stray light; the secondary focusing lens is used to focus the rear focal plane image of the Fourier lens, and to realize the wavefront at the position of the variable diaphragm, so as to facilitate the adjustment of the filtering range.
  • the light source focusing lens, Kohler lens, Fourier lens, secondary focusing lens and imaging lens are all aspherical lenses, the lenses should be coated with anti-reflection films of corresponding wavelengths on both sides, and the lens diameter should be not less than 1 inch and not more than 2 inches; the parameters of the high-magnification objective lens, Fourier lens and imaging lens should satisfy 2f 0 tan(sin -1 NA)f C /f F ⁇ L X ,2f 0 tan(sin -1 NA)f C /f F ⁇ L Y , where Lx and Ly are the horizontal and vertical dimensions of the CCD, respectively.
  • the parameter to be measured of the sample to be measured is divergence angle ⁇ sin -1 NA.
  • the beam splitter is a thin film beam splitter or a body beam splitter, and the beam splitter is coated with anti-reflection films of corresponding wavelengths on both sides, and the splitting ratio is 50:50. Its function is to merge the reflected light path and the transmitted light path into one path in front of the objective lens.
  • the magnification M of the high-power objective lens is not less than 40 times, the numerical aperture NA is not less than 0.5 and less than 1, and the surface should be coated with an anti-reflection film of the corresponding wavelength.
  • variable aperture range of the variable iris is 0.1 mm to 10 mm, and its function is to filter out stray light through spatial filtering to improve the test signal-to-noise ratio.
  • the broadband light source is a halogen lamp with a wavelength covering visible light to near infrared;
  • the optical fiber is usually a multimode optical fiber with a diameter less than 1 mm;
  • the variable neutral density filter has a variable range of neutral density from 0.1 to 4.
  • the present invention measures the far-field divergence angle of the light spot emitted by the device to be tested and derives the precise Gaussian spot size, thereby solving the problems of large errors in the light spot measurement results and complex measuring instruments (using the method of moving a robotic arm) due to the inability to accurately locate the waist position of the Gaussian beam.
  • the test system of the present invention has a high degree of freedom and a large measurement range. It can meet the characteristics of the sample to be tested by adjusting the corresponding measurement parameters.
  • the measured spot size range covers from sub-millimeter to sub-micrometer, and the wavelength range covers visible light to near-infrared band, which is far superior to existing technical means.
  • the present invention is widely applicable to the spot measurement of micron-scale light-emitting elements, and its applicable scope covers active optical devices such as lasers and superluminescent diodes, and passive optical devices such as optical fibers, optical waveguides, and optical chips.
  • the measurement error is within 5%, and it has broad application value in optical-related scientific research and engineering development.
  • FIG1 is a schematic diagram of an optical path component in a high-precision spot testing system based on a spatial imaging system provided by the present invention.
  • FIG. 2 is a schematic diagram of optical path parameters in a high-precision spot testing system based on a spatial imaging system provided by the present invention.
  • FIG3 is a schematic diagram of a Fourier image obtained on a CCD by reflecting light from a silver reflector obtained by system calibration before testing of the present invention, wherein X1 and Y1 correspond to 1/ e2 widths in the horizontal and vertical directions of the image, respectively.
  • FIG. 4 is a schematic diagram of a real image of a sample (shown as a small mode field optical fiber) obtained on a CCD by reflected light during sample testing of the present invention.
  • FIG5 is a schematic diagram of a Fourier image obtained by the present invention when testing a sample (shown as a small mode field optical fiber) on a CCD through self-luminescence, where X2 and Y2 correspond to the 1/ e2 width of the image in the horizontal and vertical directions, respectively.
  • FIG6 is a schematic diagram of the intensity distribution (horizontal or vertical) of the Fourier image of the sample (reflector and small mode field optical fiber) obtained during sample testing of the present invention, through which the far-field image size of the sample to be tested can be accurately measured.
  • 1-broad-spectrum light source 2-optical fiber, 3-light source focusing lens, 4-Köhler lens, 5-beam splitter, 6-high-magnification objective lens, 7-sample, 8-six-axis stage, 9-Fourier lens, 10-variable aperture, 11-secondary focusing lens, 12-imaging lens, 13-variable neutral density filter, 14-CCD camera, 15-computer, f S -focal length of light source focusing lens, f K -focal length of Köhler lens, f F -focal length of Fourier lens, f I -focal length of secondary focusing lens, f C -focal length of imaging lens, D 1 -arbitrary distance greater than 0, D 2 -arbitrary distance greater than 0.
  • the present invention provides a high-precision spot test system based on a spatial imaging system.
  • the test object in this example is a small mode field optical fiber, and the system structure includes: a wide-spectrum light source 1, an optical fiber 2, a light source focusing lens 3, a Kohler lens 4, a beam splitter 5, a high-magnification objective lens 6, a six-axis stage 8, a Fourier lens 9, a variable aperture 10, a secondary focusing lens 11, an imaging lens 12, a variable neutral density filter 13, a CCD camera 14, and a computer 15.
  • the system applies corresponding test logic methods to achieve overall testing.
  • the broadband light source is a halogen lamp with a wavelength covering visible light to near infrared (300 nanometers to 2 micrometers).
  • the broadband light source is used as a light source for calibrating the system and as an illumination source for measuring samples.
  • the optical fiber is a multimode optical fiber with a diameter of 200 microns (usually less than 1 mm).
  • the optical fiber introduces light from a broad-spectrum light source into the system and serves as the starting point of the entire optical path.
  • the light source focusing lens 3, the Kohler lens 4, the Fourier lens 9, the secondary focusing lens 11 and the imaging lens 12 are all aspherical lenses, the wavelength of the anti-reflection film on both sides of the lens is 1050-1700 nanometers (400-700 nanometers or 650-1050 nanometers can also be selected), and the lens diameter is 1 inch (preferably not less than 1 inch and not more than 2 inches).
  • the light source focusing lens 3 is used to collimate the light emitted by the wide-spectrum light source through the optical fiber.
  • the Kohler lens 4 is used to form a Kohler illumination system in front of the objective lens to increase the objective lens Illumination range, convenient for finding samples.
  • the Fourier lens 9 is used to focus the rear focal plane image behind the objective lens, perform optical Fourier transform on the near-field light spot, and obtain the corresponding far-field image.
  • the secondary focusing lens 11 is used to focus the rear focal plane image of the Fourier lens 9, and to image the wavefront at the position of the variable aperture, so as to facilitate the adjustment of the filtering range.
  • the imaging lens is used to enable a focused real image to be formed on the CCD.
  • the above focal lengths are only examples, and the focal lengths of the above lenses can be selected according to needs.
  • the beam splitter 5 should be a thin film beam splitter or a body beam splitter, and the double sides should be coated with a 1200 nm to 1600 nm anti-reflection film.
  • the beam splitter has a splitting ratio of 50:50, and its function is to merge the reflected light path and the transmitted light path into one path in front of the objective lens.
  • the function of the high-power objective lens 6 is to utilize its high NA characteristics to collect as much light as possible from all emission directions of the sample to be tested, and to focus the light at a specific angle to the corresponding position of the back focal plane of the objective lens through optical Fourier transformation, so that the position-light intensity distribution diagram of the near-field image is transformed into the angle-light intensity distribution diagram of the far-field image, thereby achieving the purpose of analyzing the divergence angle of the light spot.
  • the magnification M of the high-power objective lens 6 should be no less than 40 times, the numerical aperture NA should be no less than 0.5 and less than 1, and the surface should be plated with an anti-reflection film of the corresponding wavelength (400-700 nanometers or 650-1050 nanometers or 1050-1700 nanometers).
  • the six-axis stage 8 is used to load the sample to be tested, and its six-axis degrees of freedom correspond to the vertical and rotational coordinate axes in the Cartesian coordinate system.
  • the fine-tuning accuracy of the linear direction and rotational direction of the stage is not less than 1 micron/scale and 1 minute/scale respectively.
  • the sample to be tested is a small mode field optical fiber, and the parameters to be tested are defined as the divergence angle ⁇ sin -1 NA and the working center wavelength is ⁇ .
  • the variable aperture 10 has an aperture range of 0.1 mm to 10 mm, and its function is to filter out stray light through spatial filtering to improve the test signal-to-noise ratio.
  • the variable aperture 10 is located at the overlap of the rear focus of the Fourier lens and the front focus of the secondary focusing lens.
  • variable neutral density filter 13 has a variable neutral density ranging from 0.1 to 4. Its function is to reduce the amount of light passing through, to prevent the CCD camera 14 from being damaged due to receiving too high energy, and to uniformize the brightness of the image.
  • the CCD camera is used to capture the near-field image and far-field image of the sample to be tested.
  • the computer 15 is connected to the CCD camera 14 and can be installed with control and image capture software adapted to the CCD camera, and can output images for later data processing.
  • the present invention also provides a high-precision spot testing method based on a space imaging system, comprising the following steps:
  • Step 1 Choose appropriate parameters
  • the parameter selection of high-magnification objective lens, Fourier lens and imaging lens should satisfy 2fOtan (sin - 1NA) fC / fF ⁇ LX , 2fOtan (sin - 1NA) fC / fF ⁇ LY .
  • the purpose is to limit the maximum diameter of the image on the rear focal plane of the objective lens to the receiving range of the CCD.
  • ( fC ⁇ fF )/( fI ⁇ fO ) is the real image magnification.
  • the projection area of the sample to be measured on the CCD after magnification should be smaller than the CCD area.
  • Step 2 Install and calibrate the test system
  • the system is built as shown in FIG1, and the positions of the optical components are arranged as shown in FIG2. At this time, the Kohler lens 4 is not set.
  • the optical fiber 2 is connected to the light source to introduce the light of the light source into the system.
  • the light source focusing lens 3 and the beam splitter 5 are arranged in sequence from near to far on the optical path introduced by the optical fiber.
  • the high-magnification objective lens 6 and the six-axis stage 8 are arranged in the reflected light path of the beam splitter 5.
  • the Fourier lens 9, the secondary focusing lens 11, the imaging lens 12, the variable neutral density filter 13, and the CCD camera 14 are arranged in sequence from near to far on the transmitted light path of the beam splitter 5.
  • the CCD camera 14 is connected to the computer.
  • the silver reflector is loaded onto the six-axis stage 8. Turn on the light source. As shown in FIG2, the direction of the light path is in the order of the optical fiber 2, the light source focusing lens 3, the beam splitter 5, the high-magnification objective lens 6, the silver reflector, the high-magnification objective lens 6, the beam splitter 5, the Fourier lens 9, the secondary focusing lens 11, the imaging lens 12, the variable neutral density filter 13, and the CCD camera 14.
  • the distance between the stage and the objective lens is adjusted so that the image presented by the computer is a focused image on the reflector surface; the secondary focusing lens 11 is removed; the variable neutral density filter 13 is adjusted so that the maximum brightness of the image obtained by the computer is close to saturation, as shown in FIG3 ; the image is recorded and the widths in the horizontal and vertical directions at the image brightness 1/e 2 are measured to be X 1 pixel and Y 1 pixel, respectively.
  • the purpose of system calibration before testing is to determine the maximum range of divergence angle test X1 and Y1, and to calculate and determine the angle accuracy per pixel sin -1 (NA/X 1 ) and sin -1 (NA/Y 1 ).
  • the optical fiber 2 is connected to the light source to introduce the light from the light source into the system.
  • the light source focusing lens 3, the Kohler lens 4, and the beam splitter 5 are arranged in sequence from near to far on the optical path introduced by the optical fiber.
  • the high-magnification objective lens 6 and the six-axis stage 8 are arranged in the reflected light path of the beam splitter 5.
  • the Fourier lens 9, the secondary focusing lens 11, the imaging lens 12, the variable neutral density filter 13, and the CCD camera 14 are arranged in sequence from near to far on the transmitted light path of the beam splitter 5.
  • the variable aperture 10 is arranged between the Fourier lens 9 and the secondary focusing lens 11.
  • the light path passes through the aperture on the variable aperture 10.
  • the CCD camera 14 is connected to a computer. As shown in FIG2 , the direction of the light path follows the order of optical fiber 2, light source focusing lens 3, Kohler lens 4, beam splitter 5, high-magnification objective lens 6, sample to be measured 7, high-magnification objective lens 6, beam splitter 5, Fourier lens 9, variable aperture 10, secondary focusing lens 11, imaging lens 12, variable neutral density filter 13, and CCD camera 14.
  • the horizontal divergence angle of the sample is calculated to be:
  • the corresponding horizontal diameter of the Gaussian spot is
  • the vertical divergence angle is
  • the corresponding vertical diameter of the Gaussian spot is
  • the intensity distribution (horizontal or vertical) of the Fourier image of the sample obtained by taking a photo with a CCD camera is shown in FIG6 . This figure can be used to accurately measure the far-field image size of the sample to be tested.
  • the high-precision spot test system based on the spatial imaging system can be simplified in structure, and the structure includes: a wide-spectrum light source 1, an optical fiber 2, a light source focusing lens 3, a beam splitter 5, a high-magnification objective lens 6, a six-axis stage 8, a Fourier lens 9, an imaging lens 12, a variable neutral density filter 13, a CCD camera 14, and a computer 15.
  • the system applies the corresponding test logic method to realize the overall test. That is, the Kohler lens 4, the variable aperture 10, and the secondary focusing lens 11 in the system are removed, and the construction method of the remaining components is still referred to Figures 1 and 2.
  • the simplified system can also measure the size of the spot, but the difficulty of finding the target increases due to the removal of the Kohler lens, and the measurement process will be disturbed by stray light, and the operation difficulty and measurement error are greatly increased compared with the test system with all components.
  • the present invention provides a spot test method based on a simplified high-precision spot test system, wherein steps 1 and 4 are the same as steps 1 and 4 in the aforementioned high-precision spot test method based on a spatial imaging system, and steps 2 and 3 are as follows:
  • Step 2 Install and calibrate the test system
  • the system is built as shown in FIG1, and the positions of the optical elements are arranged as shown in FIG2. At this time, the Kohler lens 4, the Fourier lens 9, the variable aperture 10, and the secondary focusing lens 11 are not set.
  • the optical fiber 2 is connected to the light source to introduce the light of the light source into the system.
  • the light source focusing lens 3 and the beam splitter 5 are arranged in sequence from near to far on the optical path introduced by the optical fiber.
  • the high-magnification objective lens 6 and the six-axis stage 8 are arranged in the reflected light path of the beam splitter 5.
  • the imaging lens 12, the variable neutral density filter 13, and the CCD camera 14 are arranged in sequence from near to far on the transmitted light path of the beam splitter 5.
  • the CCD camera 14 is connected to the computer.
  • the silver reflector is loaded onto the six-axis stage 8. Turn on the light source. As shown in FIG2, the direction of the light path is in the order of the optical fiber 2, the light source focusing lens 3, the beam splitter 5, the high-magnification objective lens 6, the silver reflector, the high-magnification objective lens 6, the beam splitter 5, the imaging lens 12, the variable neutral density filter 13, and the CCD camera 14.
  • the distance between the stage and the objective lens is adjusted so that the image presented by the computer is a focused image of the reflector surface; the Fourier lens 9 is added between the beam splitter and the imaging lens; the variable neutral density filter 13 is adjusted so that the maximum brightness of the image obtained by the computer is close to saturation; the image is recorded and the width of the image in the horizontal direction and the vertical direction at the brightness of 1/e- 2 is measured to be X 1 pixel and Y 1 pixel respectively.
  • the purpose of system calibration before testing is to determine the maximum range of divergence angle test X1 and Y1, and to calculate and determine the angle accuracy per pixel sin -1 (NA/X 1 ) and sin -1 (NA/Y 1 ).
  • the small mode field optical fiber of the sample 7 to be tested is loaded onto the sample stage.
  • the Kohler lens 4, the variable aperture 10, the secondary focusing lens 11, and the Fourier lens 9 are not set.
  • the optical fiber 2 is connected to the light source, and the light of the light source is introduced into the system.
  • the light source focusing lens 3 and the beam splitter 5 are arranged in sequence from near to far on the optical path introduced by the optical fiber.
  • the high-magnification objective lens 6 and the six-axis stage 8 are arranged in the reflected light path of the beam splitter 5.
  • the imaging lens 12, the variable neutral density filter 13, and the CCD camera 14 are arranged in sequence from near to far on the transmitted light path of the beam splitter 5.
  • the CCD camera 14 is connected to the computer.
  • the direction of the optical path is in the order of the optical fiber 2, the light source focusing lens 3, the beam splitter 5, the high-magnification objective lens 6, the sample 7 to be tested, the high-magnification objective lens 6, the beam splitter 5, the imaging lens 12, the variable neutral density filter 13, and the CCD camera 14.

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Abstract

一种基于空间成像系统的高精度光斑测试系统及方法，系统包括：宽谱光源（1）、光纤（2）、光源聚焦透镜（3）、科勒透镜（4）、分束器（5）、高倍率物镜（6）、样品（7）、六轴载物台（8）、傅里叶透镜（9）、可变光阑（10）、二次聚焦透镜（11）、成像透镜（12）、可变中性密度滤光片（13）、CCD相机（14）、计算机（15）。测试时将样品（7）放置在六轴载台上（8），首先利用宽谱照明光对样品（7）成反射实像的方法寻找出光口，然后再通过傅里叶成像将样品（7）自身发光光斑的远场像投射到CCD相机（14）上，最后对图像进行数据处理得到样品光斑发散角后推算出光斑尺寸。该系统和方法适用于微米尺度的发光元件的光斑测量，测量误差在5％以内，且测试波长可覆盖可见光至近红外波段。

Description

一种基于空间成像系统的高精度光斑测试系统及方法 技术领域
本发明属于光学及光通信技术领域，具体涉及一种于空间成像系统的高精度光斑测试系统及方法。
背景技术
近年来，5G通信的发展带动了光通信技术快速升级，挑战也随之而来，尤其是在能耗性能比方面矛盾突出。光通信中，一部分能量损耗来源于光交换界面处。这是由于光在不同材料介质中的模场大小不同，使得出射光斑在能量交换时模式不匹配，一部分光变成杂散光，导致耦合效率低，进而增加了系统能耗并降低通信的信噪比。如果能够精确测量结构的出射光斑将会对通过工程设计进一步提高光界面的耦合效率有极大的帮助。但在现有技术中，出射光斑的大小很难精确获取，究其缘由，通常由两方面原因造成：
一方面，设计的结构出射光斑与制备得到的结构出射光斑因为材料、工艺、环境等原因存在差异。
另一方面，实际的出射光斑尺寸与出射端面的尺寸没有直接关系，这就意味着仅仅通过观察近场光斑和端面无法确定出射光斑的精确尺寸，而目前尚缺乏精确的测量方案。
发明内容
为解决上述问题，本发明提供一种基于空间成像系统的高精度光 斑测试系统及方法，广泛适用于测量微米尺度的发光元件的光斑尺寸。
为达到上述目的，本发明的技术方案如下：
一种基于空间成像系统的高精度光斑测试方法，包括如下步骤：
步骤1，选择合适的参数
选择参数满足2f 0tan(sin -1NA)f C/f F<L X,2f 0tan(sin -1NA)f C/f F<L Y的高倍率物镜、傅里叶透镜和成像透镜，其中，f O为高倍率物镜的等效焦距，NA为高倍率物镜的数值孔径，f C为成像透镜的焦距，f F为傅里叶透镜的焦距，L X为CCD相机的水平尺寸，L Y为CCD相机的竖直尺寸，使物镜后焦面像最大直径限制在CCD接收范围内；实像放大倍率(f C·f F)/(f I·f O)使得待测样品通过放大后在CCD上的投影面积小于CCD面积；
步骤2，安装并校准测试系统
当系统包含科勒透镜、可变光阑、二次聚焦透镜时，包括如下过程：
搭建测试系统，光纤与光源连接，光源聚焦透镜、分束器由近到远依次设置在光纤引入的光路上，高倍率物镜和六轴载物台设置在分束器的反射光路上，傅里叶透镜、二次聚焦透镜、成像透镜、可变中性密度滤光片、CCD相机由近及远依次设置在分束器的透射光路上，CCD相机与计算机连接；将银制反射镜装载到六轴载物台，光路方向按照光纤、光源聚焦透镜、分束器、高倍率物镜、银制反射镜、高倍率物镜、分束器、傅里叶透镜、二次聚焦透镜、成像透镜、可变中性 密度滤光片、CCD相机的顺序；调整载物台与物镜间距使计算机呈现图像为反射镜表面聚焦图像；移除二次聚焦透镜；调整可变中性密度滤光片，使计算机得到的图像亮度最大值接近饱和；记录图像并测量图像亮度1/e 2处水平方向和垂直方向的宽度分别为X 1像素和Y 1像素；
当系统不包含科勒透镜、可变光阑、二次聚焦透镜时，包括如下过程：
搭建测试系统，此时不设置傅里叶透镜；将光纤与光源连接，光源聚焦透镜、分束器由近到远依次设置在光纤引入的光路上，高倍率物镜和六轴载物台设置在分束器的反射光路上，成像透镜、可变中性密度滤光片、CCD相机由近及远依次设置在分束器的透射光路上，CCD相机与计算机连接；将银制反射镜装载到六轴载物台，光路方向按照光纤、光源聚焦透镜、分束器、高倍率物镜、银制反射镜、高倍率物镜、分束器、成像透镜、可变中性密度滤光片、CCD相机的顺序；调整载物台与物镜间距使计算机呈现图像为反射镜表面聚焦图像；将傅里叶透镜添加至分束器与成像透镜之间；调整可变中性密度滤光片，使计算机得到的图像亮度最大值接近饱和；记录图像并测量图像亮度1/e 2处水平方向和垂直方向的宽度分别为X 1像素和Y 1像素；
步骤3，测试样品
当系统包含科勒透镜、可变光阑、二次聚焦透镜时，包括如下过程：
将待测样品装载到样品台，搭建测试系统，将光纤与光源连接，光源聚焦透镜、科勒透镜、分束器由近到远依次设置在光纤引入的光 路上，高倍率物镜和六轴载物台设置在分束器的反射光路上，傅里叶透镜、二次聚焦透镜、成像透镜、可变中性密度滤光片、CCD相机由近及远依次设置在分束器的透射光路上，可变光阑设置在傅里叶透镜、二次聚焦透镜之间，光路穿过可变光阑上的孔隙，CCD相机与计算机连接；光路方向按照光纤、光源聚焦透镜、科勒透镜、分束器、高倍率物镜、待测样品、高倍率物镜、分束器、傅里叶透镜、可变光阑、二次聚焦透镜、成像透镜、可变中性密度滤光片、CCD相机的顺序；调整载物台与物镜间距使计算机呈现图像为样品表面反射实像图像；通过反射实像图定位样品出光部位附近；使样品自发光，移除光路中的分束器，光路方向变为待测样品、高倍率物镜、傅里叶透镜、可变光阑、二次聚焦透镜、成像透镜、可变中性密度滤光片、CCD相机；进一步移动样品使CCD相机所见光斑位置居中并且聚焦；改变可变光阑大小使成像范围局限至仅光斑附近；移除二次聚焦透镜，调整可变中性密度滤光片，使计算机得到的图像亮度最大值与校准图像相同；记录图像并测量图像亮度1/e 2处水平方向和垂直方向的宽度分别为X 2像素和Y 2像素；
当系统不包含科勒透镜、可变光阑、二次聚焦透镜时，包括如下过程：
将待测样品装载到样品台，此时不设置傅里叶透镜；将光纤与光源连接，光源聚焦透镜、分束器由近到远依次设置在光纤引入的光路上，高倍率物镜和六轴载物台设置在分束器的反射光路上，成像透镜、可变中性密度滤光片、CCD相机由近及远依次设置在分束器的透射光 路上，CCD相机与计算机连接；光路方向按照光纤、光源聚焦透镜、分束器、高倍率物镜、待测样品、高倍率物镜、分束器、成像透镜、可变中性密度滤光片、CCD相机的顺序；调整载物台与物镜间距使计算机呈现图像为样品表面反射实像图像；通过反射实像图定位样品出光部位附近；使样品自发光，移除光路中的分束器，光路方向变为待测样品、高倍率物镜、成像透镜、可变中性密度滤光片、CCD相机；进一步移动样品使CCD相机所见光斑位置居中并且聚焦；将傅里叶透镜添加至分束器与成像透镜之间；调整可变中性密度滤光片，使计算机得到的图像亮度最大值与校准图像相同；记录图像并测量图像亮度1/e 2处水平方向和垂直方向的宽度分别为X 2像素和Y 2像素；
步骤4，数据处理
通过比较校准数据与参测数据，计算得到样品的水平方向发散角为
Figure PCTCN2022126157-appb-000001
对应高斯光斑水平直径为
Figure PCTCN2022126157-appb-000002
垂直方向发散角为
Figure PCTCN2022126157-appb-000003
对应高斯光斑垂直直径为
Figure PCTCN2022126157-appb-000004
进一步的，还包括如下步骤：根据样品傅里叶图像的强度分布图测量待测样品的远场像尺寸。
本发明还提供了一种基于空间成像系统的高精度光斑测试系统，包括宽谱光源、光纤、光源聚焦透镜、分束器、高倍率物镜、六轴载物台、傅里叶透镜、成像透镜、可变中性密度滤光片、CCD相机、计算机；
所述宽谱光源与光纤连接，所述光源聚焦透镜、分束器由近到远 依次设置在光纤引入的光路上，高倍率物镜和六轴载物台设置在分束器的反射光路上，傅里叶透镜、成像透镜、可变中性密度滤光片、CCD相机由近及远依次设置在分束器的透射光路上，CCD相机与计算机连接；
所述光纤将宽谱光源的光引入系统；所述光源聚焦透镜用于对宽谱光源经由光纤发出的光进行准直；所述分束器用于将反射光路与透射光路在物镜前合并为一路；所述高倍率物镜用于收集待测样品所有发射方向上的光；所述六轴载物台用于装载待测样品；所述傅里叶透镜用于对物镜后方的后焦面像聚焦，将近场光斑进行光学傅里叶变换，得到与之对应的远场图像；所述成像透镜用于使CCD相机上能成聚焦实像；所述可变中性密度滤光片用于降低通光量；所述计算机用于接收CCD相机成像并进行处理。
进一步的，还包括科勒透镜、可变光阑和二次聚焦透镜；
所述科勒透镜设置在光源聚焦透镜和分束器之间，所述可变光阑、二次聚焦透镜设置在傅里叶透镜与成像透镜之间，位于分束器的透射光路上，其中可变光阑位于傅里叶透镜的后焦点与二次聚焦透镜的前焦点的重合处，所述透射光路穿过可变光阑上的孔隙；
所述科勒透镜用于在物镜前组成科勒照明系统增大物镜照明范围；所述可变光阑用于滤除杂散光；所述二次聚焦透镜用于对傅里叶透镜的后焦面像聚焦，将可变光阑所在位置的波阵面实像化，方便调整滤波范围。
进一步的，所述光源聚焦透镜、科勒透镜、傅里叶透镜、二次聚 焦透镜和成像透镜均为非球面透镜，透镜应双面镀对应波长的增透膜，透镜直径不小于1英寸且不大于2英寸；高倍率物镜、傅里叶透镜和成像透镜的参数应满足2f 0tan(sin -1NA)f C/f F<L X,2f 0tan(sin -1NA)f C/f F<L Y，其中Lx和Ly分别为CCD的横向与纵向尺寸。
进一步的，所述待测样品的待测参数为发散角θ<sin -1NA。
进一步的，所述分束器为薄膜分束器或体分束器，分束器双面镀对应波长的增透膜，分光比为50:50，作用是将反射光路与透射光路在物镜前合并为一路。
进一步的，所述高倍率物镜的放大倍率M不小于40倍，数值孔径NA不小于0.5且小于1，表面应镀对应波长的增透膜。
进一步的，所述可变光阑孔径可变范围为0.1毫米到10毫米，其作用是通过空间滤波的方式滤除杂散光提高测试信噪比。
进一步的，所述宽谱光源为卤素灯，波长覆盖可见光至近红外；所述光纤通常为多模光纤，其直径小于1毫米；所述可变中性密度滤光片中性密度可变范围为0.1到4。
本发明的有益效果为：
1.本发明通过测量待测器件发射光斑的远场发散角，推导出精确的高斯光斑尺寸，解决了以往由于无法准确定位高斯光束束腰位置导致光斑测量结果误差较大、测量仪器复杂(利用机械臂移动的方法)等问题。
2.本发明测试系统拥有高自由度和大测量范围，可以通过调整相应测量参数满足待测样品特征，所测量光斑尺寸范围覆盖从亚毫米至亚微 米，波长范围覆盖可见光至近红外波段，远超现有技术手段。
3.本发明广泛适用于微米尺度的发光元件的光斑测量，可适用范围涵盖有源光器件如激光器、超辐射发光二极管，无源光器件如光纤、光波导、光芯片，测量误差在5％以内，对光学相关的科学研究和工程研发都具有广泛应用价值。
附图说明
图1为本发明提供的提供一种基于空间成像系统的高精度光斑测试系统中光路组件示意图。
图2为本发明提供的提供一种基于空间成像系统的高精度光斑测试系统中光路参数示意图。
图3是本发明测试前系统校准得到银质反射镜通过反射光在CCD上得到傅里叶图像的示意图，X 1和Y 1分别对应图像水平方向和垂直方向的1/e 2宽度。
图4是本发明在样品测试时得到样品(图示为小模场光纤)通过反射光在CCD上得到的实像示意图。
图5是本发明在样品测试时得到样品(图示为小模场光纤)通过自发光在CCD上得到傅里叶图像的示意图，X 2和Y 2分别对应图像水平方向和垂直方向的1/e 2宽度。
图6是本发明在样品测试时得到样品(反射镜和小模场光纤)傅里叶图像的强度分布(水平或垂直)示意图，通过此图可以精确测量待测样品的远场像尺寸。
附图标记说明：
1-宽谱光源、2-光纤、3-光源聚焦透镜、4-科勒透镜、5-分束器、6-高倍率物镜、7-样品、8-六轴载物台、9-傅里叶透镜、10-可变光阑、11-二次聚焦透镜、12-成像透镜、13-可变中性密度滤光片、14-CCD相机、15-计算机、f S-光源聚焦透镜的焦距、f K-科勒透镜的焦距、f F-傅里叶透镜的焦距、f I-二次聚焦透镜的焦距、f C-成像透镜的焦距、D 1-大于0的任意距离、D 2-大于0的任意距离。
具体实施方式
以下将结合具体实施例对本发明提供的技术方案进行详细说明，应理解下述具体实施方式仅用于说明本发明而不用于限制本发明的范围。
如图1-2所示，本发明提供一种基于空间成像系统的高精度光斑测试系统。本例针对的测试对象是小模场光纤，系统结构包括：宽谱光源1、光纤2、光源聚焦透镜3、科勒透镜4、分束器5、高倍率物镜6、六轴载物台8、傅里叶透镜9、可变光阑10、二次聚焦透镜11、成像透镜12、可变中性密度滤光片13、CCD相机14、计算机15。系统应用相应的测试逻辑方法实现整体测试。
具体地说，本例中宽谱光源为卤素灯，波长覆盖可见光至近红外(300纳米～2微米)，宽谱光源为作为校准系统时的发光光源以及测量样品时的照明光源。
光纤为多模光纤，直径为200微米(通常应小于1毫米)，光纤 将宽谱光源的光引入系统，作为整个光路的起点。
光源聚焦透镜3、科勒透镜4、傅里叶透镜9、二次聚焦透镜11和成像透镜12均为非球面透镜，透镜双面镀增透膜的波长为1050～1700纳米(还可选择(400～700纳米或650～1050纳米)，透镜直径为1英寸(以不小于1英寸且不大于2英寸为宜)。光源聚焦透镜3用于对宽谱光源经由光纤发出的光进行准直。科勒透镜4用于在物镜前组成科勒照明系统，增大物镜照明范围，方便寻找样品。傅里叶透镜9用于对物镜后方的后焦面像聚焦，将近场光斑进行光学傅里叶变换，得到与之对应的远场图像。二次聚焦透镜11用于对傅里叶透镜9的后焦面像聚焦，将可变光阑所在位置的波阵面实像化，方便调整滤波范围。成像透镜用于使CCD上能成聚焦实像。本例中，光源聚焦透镜3、科勒透镜4、傅里叶透镜9、二次聚焦透镜11和成像透镜12的焦距为f S＝50毫米、f K＝200毫米、f F＝150毫米、f I＝50毫米、f C＝300毫米。上述焦距仅作为示例，可以根据需求选择上述透镜的焦距。
分束器5应采用薄膜分束器或体分束器，并且双面镀1200纳米～1600纳米的增透膜，本例中分束器分光比为50:50，作用是将反射光路与透射光路在物镜前合并为一路。
高倍率物镜6的作用是利用其高NA的特点，尽可能收集待测样品所有发射方向上的光，并通过光学傅里叶变换将特定角度的光聚焦到物镜的后焦面对应位置上，使近场像的位置-光强分布图转变成远场像的角度-光强分布图，从而达到分析光斑发散角的目的。高倍率 物镜6的放大倍率M应不小于40倍，数值孔径NA不小于0.5且小于1，表面应镀对应波长(400～700纳米或650～1050纳米或1050～1700纳米)的增透膜。本例中，高倍率物镜6的放大倍率为40倍，等效焦距为f O＝2毫米，数值孔径NA为0.5，表面镀1050～1700纳米的增透膜。
六轴载物台8用于装载待测样品，其六轴自由度对应笛卡尔坐标系中的垂直和旋转坐标轴，载物台的直线方向和旋转方向微调精度分别不低于1微米/刻度和1分/刻度。
本例中待测样品为小模场光纤，待测参数定义为发散角θ<sin -1NA，工作中心波长为λ。
可变光阑10其孔径可变范围为0.1毫米到10毫米，其作用是通过空间滤波的方式滤除杂散光提高测试信噪比。在安装测试系统时，可变光阑10位于傅里叶透镜的后焦点与二次聚焦透镜的前焦点的重合处。
可变中性密度滤光片13其中性密度可变范围为0.1到4。其作用是用于降低通光量，避免CCD相机14因为接收过高能量而损坏，并均一化图像的亮度。
CCD相机14为特定波长优化，其工作范围为900纳米至2000纳米，动态范围大于30dB，分辨率为水平X像素*垂直Y像素，应大于300*200，本例中分辨率为400*300，CCD尺寸为L X*L Y＝12毫米*9毫米。CCD相机用于捕获待测样品的近场像和远场像。
计算机15与CCD相机14连接，可安装适配CCD相机的控制和图 像捕获软件，能够输出用于后期数据处理的图像。
本发明还提供了一种基于空间成像系统的高精度光斑测试方法，包括如下步骤：
步骤1，选择合适的参数
高倍率物镜、傅里叶透镜和成像透镜的参数选择应满足2f Otan(sin -1NA)f C/f F<L X,2f Otan(sin -1NA)f C/f F<L Y，其目的是使物镜后焦面像最大直径限制在CCD接收范围内；(f C·f F)/(f I·f O)为实像放大倍率，应使待测样品通过放大后在CCD上的投影面积小于CCD面积。
步骤2，安装并校准测试系统
如附图1所示搭建系统，并按附图2所示各光学元件位置摆放，此时不设置科勒透镜4。光纤2与光源连接，将光源的光引入系统，光源聚焦透镜3、分束器5由近到远依次设置在光纤引入的光路上，高倍率物镜6和六轴载物台8设置在分束器5的反射光路上，傅里叶透镜9、二次聚焦透镜11、成像透镜12、可变中性密度滤光片13、CCD相机14由近及远依次设置在分束器5的透射光路上，CCD相机14与计算机连接。将银制反射镜装载到六轴载物台8。打开光源，如图2所示，光路方向按照光纤2、光源聚焦透镜3、分束器5、高倍率物镜6、银制反射镜、高倍率物镜6、分束器5、傅里叶透镜9、二次聚焦透镜11、成像透镜12、可变中性密度滤光片13、CCD相机14的顺序。调整载物台与物镜间距使计算机呈现图像为反射镜表面聚焦图像；移除二次聚焦透镜11；调整可变中性密度滤光片13，使计算 机得到的图像亮度最大值接近饱和，如图3所示；记录图像并测量图像亮度1/e 2处水平方向和垂直方向的宽度分别为X 1像素和Y 1像素。
测试前系统校准的目的是确定发散角测试最大范围X1和Y1，以及计算并确定每像素角度精度sin -1(NA/X 1)和sin -1(NA/Y 1)。
步骤3，测试样品
将待测样品7小模场光纤装载到样品台，如附图1所示搭建系统，光纤2与光源连接，将光源的光引入系统，光源聚焦透镜3、科勒透镜4、分束器5由近到远依次设置在光纤引入的光路上，高倍率物镜6和六轴载物台8设置在分束器5的反射光路上，傅里叶透镜9、二次聚焦透镜11、成像透镜12、可变中性密度滤光片13、CCD相机14由近及远依次设置在分束器5的透射光路上，可变光阑10设置在傅里叶透镜9、二次聚焦透镜11之间，光路穿过可变光阑10上的孔隙，CCD相机14与计算机连接。如图2所示，光路方向按照光纤2、光源聚焦透镜3、科勒透镜4、分束器5、高倍率物镜6、待测样品7、高倍率物镜6、分束器5、傅里叶透镜9、可变光阑10、二次聚焦透镜11、成像透镜12、可变中性密度滤光片13、CCD相机14的顺序。调整载物台与物镜间距使计算机呈现图像为样品表面反射实像图像；通过反射实像图定位样品出光部位附近，如图4所示；使样品自发光，移除光路中的分束器5(可采用折叠型分束器，只需折叠该分束器即可达到将其从光路中移除的效果)，光路方向变为待测样品7、高倍率物镜6、傅里叶透镜9、可变光阑10、二次聚焦透镜11、成像透镜12、可变中性密度滤光片13、CCD相机14；进一步移动样品使CCD 相机所见光斑位置居中并且聚焦；改变可变光阑大小使成像范围局限至仅光斑附近；移除二次聚焦透镜11，调整可变中性密度滤光片，使计算机得到的图像亮度最大值与校准图像相同；记录图像并测量图像亮度1/e 2处水平方向和垂直方向的宽度分别为X 2像素和Y 2像素，如图5所示。
步骤4，数据处理
通过比较校准数据与参测数据，计算得到样品的水平方向发散角为
Figure PCTCN2022126157-appb-000005
对应高斯光斑水平直径为
Figure PCTCN2022126157-appb-000006
垂直方向发散角为
Figure PCTCN2022126157-appb-000007
对应高斯光斑垂直直径为
Figure PCTCN2022126157-appb-000008
通过CCD相机拍照获得样品傅里叶图像的强度分布(水平或垂直)如图6所示，通过此图可以精确测量待测样品的远场像尺寸。
通过反复试验，前述的基于空间成像系统的高精度光斑测试系统在结构上可以进行精简，结构包括：宽谱光源1、光纤2、光源聚焦透镜3、分束器5、高倍率物镜6、六轴载物台8、傅里叶透镜9、成像透镜12、可变中性密度滤光片13、CCD相机14、计算机15。系统应用相应的测试逻辑方法实现整体测试。即去除系统中的科勒透镜4、可变光阑10、二次聚焦透镜11，其余各部件搭建方式依然参照图1和图2。精简后的系统也能够测量出光斑的大小，但因去除了科勒透镜寻找目标的难度增加，且测量过程中会受到杂散光的干扰，操作难度和测量误差均较具有全部组件的测试系统有较大增加。
基于精简的高精度光斑测试系统，相应的测试方法也有所简化。 具体的，本发明提供了基于精简的高精度光斑测试系统的光斑测试方法，其步骤1和4与前述基于空间成像系统的高精度光斑测试方法中的步骤1和4相同，步骤2和3如下：
步骤2，安装并校准测试系统
如附图1所示搭建系统，并按附图2所示各光学元件位置摆放，此时不设置科勒透镜4、傅里叶透镜9、可变光阑10、二次聚焦透镜11。光纤2与光源连接，将光源的光引入系统，光源聚焦透镜3、分束器5由近到远依次设置在光纤引入的光路上，高倍率物镜6和六轴载物台8设置在分束器5的反射光路上，成像透镜12、可变中性密度滤光片13、CCD相机14由近及远依次设置在分束器5的透射光路上，CCD相机14与计算机连接。将银制反射镜装载到六轴载物台8。打开光源，如图2所示，光路方向按照光纤2、光源聚焦透镜3、分束器5、高倍率物镜6、银制反射镜、高倍率物镜6、分束器5、成像透镜12、可变中性密度滤光片13、CCD相机14的顺序。调整载物台与物镜间距使计算机呈现图像为反射镜表面聚焦图像；将傅里叶透镜9添加至分束器与成像透镜之间；调整可变中性密度滤光片13，使计算机得到的图像亮度最大值接近饱和；记录图像并测量图像亮度1/e- 2处水平方向和垂直方向的宽度分别为X 1像素和Y 1像素。
测试前系统校准的目的是确定发散角测试最大范围X1和Y1，以及计算并确定每像素角度精度sin -1(NA/X 1)和sin -1(NA/Y 1)。
步骤3，测试样品
将待测样品7小模场光纤装载到样品台，此时不设置科勒透镜4、 可变光阑10、二次聚焦透镜11、傅里叶透镜9，光纤2与光源连接，将光源的光引入系统，光源聚焦透镜3、分束器5由近到远依次设置在光纤引入的光路上，高倍率物镜6和六轴载物台8设置在分束器5的反射光路上，成像透镜12、可变中性密度滤光片13、CCD相机14由近及远依次设置在分束器5的透射光路上，CCD相机14与计算机连接。如图2所示，光路方向按照光纤2、光源聚焦透镜3、分束器5、高倍率物镜6、待测样品7、高倍率物镜6、分束器5、成像透镜12、可变中性密度滤光片13、CCD相机14的顺序。调整载物台与物镜间距使计算机呈现图像为样品表面反射实像图像；通过反射实像图定位样品出光部位附近；使样品自发光，并移除光路中的分束器5(可采用折叠型分束器，只需折叠该分束器即可达到将其从光路中移除的效果)，光路方向变为待测样品7、高倍率物镜6、成像透镜12、可变中性密度滤光片13、CCD相机14；进一步移动样品使CCD相机所见光斑位置居中并且聚焦；将傅里叶透镜9添加至分束器与成像透镜之间；调整可变中性密度滤光片，使计算机得到的图像亮度最大值与校准图像相同；记录图像并测量图像亮度1/e 2处水平方向和垂直方向的宽度分别为X 2像素和Y 2像素，如图5所示。
需要说明的是，以上内容仅仅说明了本发明的技术思想，不能以此限定本发明的保护范围，对于本技术领域的普通技术人员来说，在不脱离本发明原理的前提下，还可以做出若干改进和润饰，这些改进和润饰均落入本发明权利要求书的保护范围之内。

Claims (10)

  1. 一种基于空间成像系统的高精度光斑测试方法，其特征在于，包括如下步骤：
    步骤1，选择合适的参数
    选择参数满足2f Otan(sin -1NA)f C/f F<L X,2f Otan(sin -1NA)f C/f F<L Y的高倍率物镜、傅里叶透镜和成像透镜，其中，f O为高倍率物镜的等效焦距，NA为高倍率物镜的数值孔径，f C为成像透镜的焦距，f F为傅里叶透镜的焦距，L X为CCD相机的水平尺寸，L Y为CCD相机的竖直尺寸，使物镜后焦面像最大直径限制在CCD接收范围内；实像放大倍率(f C·f F)/(f I·f O)使得待测样品通过放大后在CCD上的投影面积小于CCD面积；
    步骤2，安装并校准测试系统
    当系统包含科勒透镜、可变光阑、二次聚焦透镜时，包括如下过程：
    搭建测试系统，将光纤与光源连接，光源聚焦透镜、分束器由近到远依次设置在光纤引入的光路上，高倍率物镜和六轴载物台设置在分束器的反射光路上，傅里叶透镜、二次聚焦透镜、成像透镜、可变中性密度滤光片、CCD相机由近及远依次设置在分束器的透射光路上，CCD相机与计算机连接；将银制反射镜装载到六轴载物台，光路方向按照光纤、光源聚焦透镜、分束器、高倍率物镜、银制反射镜、高倍率物镜、分束器、傅里叶透镜、二次聚焦透镜、成像透镜、可变中性密度滤光片、CCD相机的顺序；调整载物台与物镜间距使计算机呈现 图像为反射镜表面聚焦图像；移除二次聚焦透镜；调整可变中性密度滤光片，使计算机得到的图像亮度最大值接近饱和；记录图像并测量图像亮度1/e 2处水平方向和垂直方向的宽度分别为X 1像素和Y 1像素；
    当系统不包含科勒透镜、可变光阑、二次聚焦透镜时，包括如下过程：
    搭建测试系统，此时不设置傅里叶透镜；将光纤与光源连接，光源聚焦透镜、分束器由近到远依次设置在光纤引入的光路上，高倍率物镜和六轴载物台设置在分束器的反射光路上，成像透镜、可变中性密度滤光片、CCD相机由近及远依次设置在分束器的透射光路上，CCD相机与计算机连接；将银制反射镜装载到六轴载物台，光路方向按照光纤、光源聚焦透镜、分束器、高倍率物镜、银制反射镜、高倍率物镜、分束器、成像透镜、可变中性密度滤光片、CCD相机的顺序；调整载物台与物镜间距使计算机呈现图像为反射镜表面聚焦图像；将傅里叶透镜添加至分束器与成像透镜之间；调整可变中性密度滤光片，使计算机得到的图像亮度最大值接近饱和；记录图像并测量图像亮度1/e 2处水平方向和垂直方向的宽度分别为X 1像素和Y 1像素；
    步骤3，测试样品
    当系统包含科勒透镜、可变光阑、二次聚焦透镜时，包括如下过程：
    将待测样品装载到样品台，搭建测试系统，将光纤与光源连接，光源聚焦透镜、科勒透镜、分束器由近到远依次设置在光纤引入的光路上，高倍率物镜和六轴载物台设置在分束器的反射光路上，傅里叶 透镜、二次聚焦透镜、成像透镜、可变中性密度滤光片、CCD相机由近及远依次设置在分束器的透射光路上，可变光阑设置在傅里叶透镜、二次聚焦透镜之间，光路穿过可变光阑上的孔隙，CCD相机与计算机连接；光路方向按照光纤、光源聚焦透镜、科勒透镜、分束器、高倍率物镜、待测样品、高倍率物镜、分束器、傅里叶透镜、可变光阑、二次聚焦透镜、成像透镜、可变中性密度滤光片、CCD相机的顺序；调整载物台与物镜间距使计算机呈现图像为样品表面反射实像图像；通过反射实像图定位样品出光部位附近；使样品自发光，移除光路中的分束器，光路方向变为待测样品、高倍率物镜、傅里叶透镜、可变光阑、二次聚焦透镜、成像透镜、可变中性密度滤光片、CCD相机；进一步移动样品使CCD相机所见光斑位置居中并且聚焦；改变可变光阑大小使成像范围局限至仅光斑附近；移除二次聚焦透镜，调整可变中性密度滤光片，使计算机得到的图像亮度最大值与校准图像相同；记录图像并测量图像亮度1/e 2处水平方向和垂直方向的宽度分别为X 2像素和Y 2像素；
    当系统不包含科勒透镜、可变光阑、二次聚焦透镜时，包括如下过程：
    将待测样品装载到样品台，此时不设置傅里叶透镜；将光纤与光源连接，光源聚焦透镜、分束器由近到远依次设置在光纤引入的光路上，高倍率物镜和六轴载物台设置在分束器的反射光路上，成像透镜、可变中性密度滤光片、CCD相机由近及远依次设置在分束器的透射光路上，CCD相机与计算机连接；光路方向按照光纤、光源聚焦透镜、 分束器、高倍率物镜、待测样品、高倍率物镜、分束器、成像透镜、可变中性密度滤光片、CCD相机的顺序；调整载物台与物镜间距使计算机呈现图像为样品表面反射实像图像；通过反射实像图定位样品出光部位附近；使样品自发光，移除光路中的分束器，光路方向变为待测样品、高倍率物镜、成像透镜、可变中性密度滤光片、CCD相机；进一步移动样品使CCD相机所见光斑位置居中并且聚焦；将傅里叶透镜添加至分束器与成像透镜之间；调整可变中性密度滤光片，使计算机得到的图像亮度最大值与校准图像相同；记录图像并测量图像亮度1/e 2处水平方向和垂直方向的宽度分别为X 2像素和Y 2像素；
    步骤4，数据处理
    通过比较校准数据与参测数据，计算得到样品的水平方向发散角为
    Figure PCTCN2022126157-appb-100001
    对应高斯光斑水平直径为
    Figure PCTCN2022126157-appb-100002
    垂直方向发散角为
    Figure PCTCN2022126157-appb-100003
    对应高斯光斑垂直直径为
    Figure PCTCN2022126157-appb-100004
  2. 根据权利要求1所述的基于空间成像系统的高精度光斑测试方法，其特征在于，还包括如下步骤：根据样品傅里叶图像的强度分布图测量待测样品的远场像尺寸。
  3. 基于空间成像系统的高精度光斑测试系统，其特征在于，包括宽谱光源、光纤、光源聚焦透镜、分束器、高倍率物镜、六轴载物台、傅里叶透镜、成像透镜、可变中性密度滤光片、CCD相机、计算机；
    所述宽谱光源与光纤连接，所述光源聚焦透镜、分束器由近到远依次设置在光纤引入的光路上，高倍率物镜和六轴载物台设置在分束 器的反射光路上，傅里叶透镜、成像透镜、可变中性密度滤光片、CCD相机由近及远依次设置在分束器的透射光路上，CCD相机与计算机连接；
    所述光纤将宽谱光源的光引入系统；所述光源聚焦透镜用于对宽谱光源经由光纤发出的光进行准直；所述分束器用于将反射光路与透射光路在物镜前合并为一路；所述高倍率物镜用于收集待测样品所有发射方向上的光；所述六轴载物台用于装载待测样品；所述傅里叶透镜用于对物镜后方的后焦面像聚焦，将近场光斑进行光学傅里叶变换，得到与之对应的远场图像；所述成像透镜用于使CCD相机上能成聚焦实像；所述可变中性密度滤光片用于降低通光量；所述计算机用于接收CCD相机成像并进行处理。
  4. 根据权利要求3所述的基于空间成像系统的高精度光斑测试系统，其特征在于，还包括科勒透镜、可变光阑和二次聚焦透镜；
    所述科勒透镜设置在光源聚焦透镜和分束器之间，所述可变光阑、二次聚焦透镜设置在傅里叶透镜与成像透镜之间，位于分束器的透射光路上，其中可变光阑位于傅里叶透镜的后焦点与二次聚焦透镜的前焦点的重合处，所述透射光路穿过可变光阑上的孔隙；
    所述科勒透镜用于在物镜前组成科勒照明系统增大物镜照明范围；所述可变光阑用于滤除杂散光；所述二次聚焦透镜用于对傅里叶透镜的后焦面像聚焦，将可变光阑所在位置的波阵面实像化，方便调整滤波范围。
  5. 根据权利要求3或4所述的基于空间成像系统的高精度光斑测试 系统，其特征在于，所述光源聚焦透镜、科勒透镜、傅里叶透镜、二次聚焦透镜和成像透镜均为非球面透镜，透镜应双面镀对应波长的增透膜，透镜直径不小于1英寸；高倍率物镜、傅里叶透镜和成像透镜的参数应满足2f Otan(sin -1NA)f C/f F<L X,2f Otan(sin -1NA)f C/f F<L Y，其中Lx和Ly分别为CCD的横向与纵向尺寸。
  6. 根据权利要求3或4所述的基于空间成像系统的高精度光斑测试系统，其特征在于，所述待测样品的待测参数为发散角θ<sin -1NA。
  7. 根据权利要求3或4所述的基于空间成像系统的高精度光斑测试系统，其特征在于，所述分束器为薄膜分束器或体分束器，分束器双面镀对应波长的增透膜，分光比为50:50。
  8. 根据权利要求3或4所述的基于空间成像系统的高精度光斑测试系统，其特征在于，所述高倍率物镜的放大倍率M不小于40倍，数值孔径NA不小于0.5且小于1，表面镀对应波长的增透膜。
  9. 根据权利要求4所述的基于空间成像系统的高精度光斑测试系统，其特征在于，所述可变光阑孔径可变范围为0.1毫米到10毫米。
  10. 根据权利要求3或4所述的基于空间成像系统的高精度光斑测试系统，其特征在于，所述宽谱光源为卤素灯，波长覆盖可见光至近红外；所述光纤通常为多模光纤，其直径小于1毫米；所述可变中性密度滤光片中性密度可变范围为0.1到4。
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