Multi-conjugate optical structure BRDF scanner based on galvanometer

Abstract

The invention provides a multi-conjugate optical structure BRDF scanner based on a galvanometer, which does not need a complex mechanical structure to drive a detector and a sample to move or rotate so as to generate changes of relative positions to detect scattered light rays at different angles, but adopts an area array detector to detect scattered light energy so as to detect scattered light rays at different angles. The area array detector is placed at the conjugate position of a first image plane formed by modulation of an objective lens group, so that the corresponding relation between each pixel and scattered light of different zenith angles and azimuth angles of a sample reflection space can be obtained; in other words, the steps of step-by-step movement and single-point measurement of the mechanical assembly are removed, and the detection efficiency of the instrument is greatly improved; meanwhile, the whole system is easy to carry and convenient to operate, is suitable for being used in an external environment, and can be aligned with an outdoor object at various angles for measurement.

Description

Technical Field

[0001] The present invention belongs to the technical field of optical radiation measurement, and particularly relates to a multi-conjugate optical structure BRDF scanner based on a galvanometer mirror. Background Art

[0002] The bidirectional reflectance distribution function (BRDF) is one of the important means to characterize the scattering characteristics of the surface of a component. It can accurately describe the spatial backscattering characteristics of the target surface, and its definition is the ratio of the outgoing radiance to the incident irradiance.

[0003] Traditional goniometers can measure the surface scattering properties at almost any combination of incident and outgoing viewing angles by scanning the incident and outgoing angle rays. For example, patent CN201510738039.8. This type of device requires complex instruments such as motors, turntables, or robotic arms to drive the light source, sample, or detector to translate and rotate in three-dimensional space to form a measurement combination of incident light and scattered light corresponding one-to-one at different relative positions. Measuring the BRDF value in the reflection hemisphere space requires the mechanical components to move step by step and single-point measurement. Limited by the above sampling method, at a higher sampling density, there are problems of slow measurement speed and low measurement efficiency. Another existing BRDF measuring instrument based on an area array detector, the disclosed patents are CN202310982576.1 and CN202211107038.X. It uses a large-aperture mirror to collect the scattered light in the spherical space and an area array detector to receive the light rays at different scattering angles. This type of system can measure all the scattered light in the near hemisphere space at one time under a single beam incidence. The disadvantage is that the alignment difficulty of the optical components including the mirror is relatively high.

[0004] Traditional BRDF goniometers require complex mechanical structures to drive the light source, sample, and detector to move or rotate, so as to generate changes in relative positions to obtain combinations of incident light and scattered light at different angles. Measuring the BRDF value in the reflection hemisphere space requires the mechanical components to move step by step and single-point measurement. For example, CN201510738039.8, limited by the above sampling method, at a higher sampling density, there are problems of slow measurement speed and low measurement efficiency. In view of this, the problem to be solved by the present invention is how to improve the measurement speed and measurement efficiency of BRDF measuring instruments.

[0005] Another BRDF measuring instrument based on an area array detector, the disclosed patents are CN202310982576.1 and CN202211107038.X. This type of system uses a large-aperture mirror to collect the scattered light in the spherical space, emphasizes the accuracy of placing the optical components at the focal position of the mirror, and any tolerance or vibration will affect the measurement accuracy of this type of system. The disadvantages of this type of system are relatively large alignment difficulty and high maintenance cost. Summary of the Invention

[0006] To solve the above problems, the present invention provides a galvanometer-based multi-conjugate optical structure BRDF scanner, which is simple and compact in system, stable in structure, and low in alignment difficulty.

[0007] A galvanometer-based multi-conjugate optical structure BRDF scanner includes objective lens group 1, objective lens group 2, lens 3, non-polarizing beam splitter prism 4, focusing lens group 5, focusing lens group 6, galvanometer 7, laser light source 8, and area array detector 9. Among them, objective lens group 1, objective lens group 2, relay lens group 3, non-polarizing beam splitter prism 4, focusing lens group 5, focusing lens group 6, and area array detector 9 are sequentially placed on the same optical axis along the optical path to form a measurement optical path; objective lens group 1, objective lens group 2, relay lens group 3, non-polarizing beam splitter prism 4, galvanometer 7, and laser light source 8 are sequentially placed in order, and the optical axis is deflected by 90° at the non-polarizing beam splitter prism 4 and the galvanometer 7 to form an illumination optical path;

[0008] The measured sample 11 is placed at the left focal plane of the objective lens group 1. The light beam emitted by the laser light source 8 is incident on the measured sample 11 through the illumination optical path, and the light reflected by the measured sample 11 is incident on the area array detector 9 through the measurement optical path for testing the scattering characteristics of the surface of the measured sample 11.

[0009] Furthermore, the calculation method of the bidirectional reflectance distribution function BRDF at any pixel corresponding to the surface of the measured sample 11 on the area array detector 9 is as follows:

[0010]

[0011] Where P s is the power of the light reflected by the measured sample 11, Ω s is the solid angle of the light reflected by the measured sample 11, P i is the optical power incident on the current pixel of the area array detector 9, and θ s is the angle of the light reflected by the measured sample 11.

[0012] Furthermore, the calculation method of the solid angle Ω s of the light reflected by the measured sample 11 corresponding to a single pixel on the area array detector 9 is:

[0013]

[0014] Where θ is the zenith angle of the light reflected by the measured sample 11, is the azimuth angle of the light reflected by the measured sample 11, θ1 and θ2 are the upper and lower limits of the zenith angle integration corresponding to a single pixel respectively, and They are respectively the upper and lower limits of the azimuth integration corresponding to a single pixel.

[0015] Furthermore, turn on the laser light source 8 so that the parallel light beam emitted by it passes through the illumination optical path and hits the surface of the sample to be measured 11. Control the deflection angle of the mirror surface of the galvanometer 7 through a computer program, and continuously change the angle of the light incident on the surface of the sample to be measured 11 until the 0° - 70° backscattering hemisphere space formed on the surface of the sample to be measured 11 is traversed. Finally, obtain the bidirectional reflectance distribution function BRDF of the near-hemisphere sampling angle of the sample to be measured 11 at continuously changing incident angles, and obtain the scattering characteristics of the surface of the sample to be measured 11.

[0016] Furthermore, the total focusing lens group composed of the focusing lens group lens 5 and the focusing lens group lens 6 converges the light beam onto the area array detector 9 located at the focal length of the total focusing lens group. Scattered light rays in different directions finally form light spots at different positions on the area array detector 9.

[0017] At the same time, there is a corresponding relationship between the energy detected by any pixel on the area array detector 9 and the light beam in the corresponding scattering direction and scattering solid angle. Then, under the condition of a fixed measurement angular resolution, the entire bidirectional reflectance distribution function BRDF of a single incidence can be obtained.

[0018] Furthermore, the galvanometer 7 is placed at an angle of 45° with the optical axis of the relay lens group lens 3 in the initial state. When it is necessary to change the angle of the laser light source 8 incident on the surface of the sample to be measured 11, control the direction of the reflected light at the galvanometer 7 by rotating the mirror surface of the galvanometer 7 in one-dimensional direction, and then the non-polarizing beam splitter 4 reflects the reflected light from the galvanometer 7 into the coaxial optical path of the measurement optical path and the illumination optical path.

[0019] Furthermore, the relative position between the relay lens group lens 3 and the pupil of the galvanometer 7 is: the pupil of the galvanometer 7 is located on the focal plane of the relay lens group lens 3, so that all the principal rays of the converging light beams emitted by the relay lens group lens 3 are parallel to the optical axis, presenting an image-side telecentric optical path structure.

[0020] Furthermore, the lens 3 converges the light beams of each field of view onto the primary image plane 10; the relative position relationship between the total objective lens group composed of the objective lens group lens 1 and the objective lens group lens 2 and the primary image plane 10 is: the primary image plane 10 is located on the right focal plane of the total objective lens group, and the pupil of the galvanometer 7 and the primary image plane 10 are conjugate, so that reflected light rays at different angles will converge at different positions on the primary image plane 10, and then are modulated by the total objective lens group into parallel light beams emitted at different angles.

[0021] Further, the relay lens group lens 3 modulates each light beam into a parallel light beam, which is incident on the pupil of the focusing lens group lens 5 through the non-polarizing beam splitter prism 4. The pupil of the focusing lens group lens 5 is located at the right focal length of the relay lens group lens 3 and on the left surface of the focusing lens group lens 5, so that the principal rays of the parallel light beams in all directions intersect at the center of the left surface of the focusing lens group lens 5.

[0022] Further, the left surface of the objective lens group lens 1, the left surface of the objective lens group lens 2, the right surface of the lens 3, and the right surface of the focusing lens group lens 6 are all 8th-order even aspherical surfaces, and the surfaces of the remaining lenses are all spherical surfaces.

[0023] Beneficial effects:

[0024] 1. The present invention provides a galvanometer-based multi-conjugate optical structure BRDF scanner, which does not require a complex mechanical structure to drive the detector and the sample to move or rotate, so as to produce a relative position change to detect scattered light at different angles. Instead, it uses a matrix detector to detect the scattered light energy. By placing the matrix detector at the conjugate position of the first image plane formed by the modulation of the objective lens group, the corresponding relationship between each pixel and the scattered light of different zenith angles and azimuth angles in the sample reflection space can be obtained. That is to say, the present invention eliminates the steps of gradually moving the mechanical components and single-point measurement, greatly improving the detection efficiency of the instrument. At the same time, the whole system is easy to carry, convenient to operate, suitable for the external environment, and can be aligned with outdoor objects at various angles for measurement.

[0025] 2. The present invention provides a galvanometer-based multi-conjugate optical structure BRDF scanner. The matrix detector is conjugate to the primary image plane formed by the modulation of the objective lens group, and the entrance pupil of the focusing lens group / the pupil of the galvanometer are respectively conjugate to the plane of the sample to be measured. These three pairs of conjugate optical paths partially coincide in the left measurement optical path of the beam splitter, which not only makes the system more compact, but also enables the objective lens group and the subsequent lens group to be spliced together according to the primary image plane, facilitating the alignment and detection of the objective lens group and the subsequent lens group, and at the same time facilitating maintenance. Description of the drawings

[0026] Figure 1 It is a schematic diagram of the illumination optical path provided by the present invention.

[0027] Figure 2 It is a schematic diagram of the measurement optical path provided by the present invention.

[0028] Figure 3 It is a schematic diagram of the conjugate optical path provided by the present invention.

[0029] Among them, 1 - objective lens group lens, 2 - objective lens group lens, 3 - lens, 4 - non - polarized beam splitter prism, 5 - focusing lens group lens, 6 - focusing lens group lens, 7 - galvanometer, 8 - laser light source, 9 - area array detector, 10 - primary image plane, 11 - sample surface, 12 - galvanometer pupil, 13 - focusing lens group pupil. Detailed implementation manners

[0030] In order to enable those skilled in the art to better understand the solution of this application, the technical solutions in the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings in the embodiments of this application.

[0031] Referring to FIGS. 1, 2, and 3, the present invention provides a compact BRDF scanner with a multi - conjugate optical structure. The system components include objective lens group lenses 1 and 2, lens 3, non - polarized beam splitter prism 4, focusing lens group lenses 5 and 6, galvanometer 7, laser light source 8, and area array detector 9.

[0032] In the above example, the BRDF measurement device can measure the scattered outgoing light with zenith angles from 0° to 70° and azimuth angles from 0° to 360° in the reflection hemisphere space of the sample surface, and can simultaneously scan the incident light with zenith angles from 0° to 70°.

[0033] The BRDF measurement device is composed of an illumination optical path and a measurement optical path. Among them, the co - axial objective lens group lenses 1 and 2, relay lens group lens 3, non - polarized beam splitter prism 4, focusing lens group lenses 5 and 6, and area array detector 9 are sequentially placed on the same optical axis along the optical path to form the measurement optical path. The co - axial objective lens group lenses 1 and 2, relay lens group lens 3, non - polarized beam splitter prism 4, galvanometer 7, and laser light source 8 are sequentially placed in order, and the optical axis is deflected by 90° at the non - polarized beam splitter prism 4 and galvanometer 7 to form the illumination optical path.

[0034] The specific implementation manners of the illumination optical path and the measurement optical path are as described below, and the features are applicable to both of them.

[0035] The specific implementation manner of the illumination optical path is as described below. By making some modifications to the features of this specific solution, other implementation manners can be obtained.

[0036] Referring to Figure 1 , the laser emitted by the laser light source 8 propagates towards the center of the mirror surface of the galvanometer 7. The laser light source 8 is a Gaussian beam.

[0037] Referring to Figure 1 , the galvanometer 7 is placed at an angle of 45° with the optical axis of the lens 3 in the initial state. When the incident angle needs to be changed, the direction of the reflected light is controlled by rotating the mirror surface of the galvanometer in one - dimensional direction.

[0038] As shown in Figure 1As shown, the reflected light from the galvanometer mirror 7 by the non-polarizing beam splitter 4 is reflected into the coaxial optical path of the measurement optical path and the illumination optical path.

[0039] As Figure 1 shown, the lens 3 converges the light beams of each field of view onto the primary image plane 10. The relative position between the lens 3 and the pupil of the galvanometer mirror 7 is: the pupil of the galvanometer mirror 7 is located on the focal plane of the lens 3. Therefore, the chief rays of all the converging light beams emerging from the lens 3 are parallel to the optical axis, presenting an image-side telecentric optical path structure.

[0040] See Figure 1 , the relative position relationship between the objective lens group composed of the objective lens group lens 1 and the objective lens group lens 2 and the primary image plane 10 is: the primary image plane 10 is located on the right focal plane of the objective lens group. Due to the conjugate relationship between the pupil of the galvanometer mirror 7 and the primary image plane 10, the reflected light at different angles will converge at different positions on the primary image plane, and then be modulated by the objective lens group into parallel light beams emerging at different angles.

[0041] See Figure 1 , the sample surface 11 is placed at the front focal plane of the objective lens group. Since the chief rays of all the converging light beams emerging from the lens 3 are parallel to the optical axis, the form of the objective lens group optical path in the illumination optical path presents an object-side telecentric optical path. Therefore, the parallel light beams emerging at different angles all illuminate the same area on the sample surface, and this area can be regarded as the exit pupil of the illumination optical path.

[0042] In this embodiment, the shape of this area is circular, centered on the optical axis, and the diameter is set to 1.2 mm. Finally, the switching of the incident light at various angles on the sample surface is realized.

[0043] The specific implementation of the measurement optical path is as described below. By making some modifications to the features of this specific scheme, other implementation manners can be obtained.

[0044] See Figure 2 , the incident light incident on the sample surface 11 is scattered into scattered light rays in different directions. The circular area with a diameter of 1.5 mm centered on the optical axis of the sample surface 11 is regarded as the entrance pupil of the measurement optical path. This range includes the exit pupil of the illumination optical path described in the illumination optical path example. Therefore, the above-mentioned scattered light rays can be regarded as parallel light beams in various directions emerging within the range of the illumination optical path exit pupil.

[0045] See Figure 2 , the objective lens group composed of the objective lens group lens 1 and the objective lens group lens 2 converges the scattered light rays onto the primary image plane 10. All the structural features of the optical components follow the illumination optical path example. Therefore, the chief rays of the light beams converging on the primary image plane 10 are all parallel to the optical axis.

[0046] See Figure 2, the lens 3 modulates each light beam into a parallel light beam, which is incident on the pupil of the focusing lens group through the non-polarizing beam splitter prism 4. The pupil of the focusing lens group is located at the right focal length of the lens 3 and on the left surface of the focusing lens group lens 5. Therefore, the chief rays of the parallel light beams in all directions intersect at the center of the left surface of the focusing lens group lens 5.

[0047] See Figure 2 , the focusing lens group composed of the focusing lens group lens 5 and the focusing lens group lens 6 converges the light beam on the area array detector 9 located at the focal length of the focusing lens group. The scattered light rays in different directions finally form light spots at different positions on the detector.

[0048] In this implementation, the area array detector 9 is selected as a color area array CMOS.

[0049] In this implementation, see Figure 2 , the left surface of the objective lens group lens 1, the left surface of the objective lens group lens 2, the right surface of the lens 3, and the right surface of the focusing lens group lens 6 are all 8th-order even aspherical surfaces, and the surfaces of the remaining lenses are all spherical surfaces.

[0050] The general expression of the 8th-order aspherical surface is:

[0051]

[0052] In the formula, z is the surface vector height, c is the surface curvature, k is the conic coefficient, and is the coefficient of the i-th term in the polynomial. When designing the system within the innovative scope of the present invention, the specific values of each coefficient can be arbitrarily set by those skilled in the art.

[0053] On the other hand, based on the above BRDF scanner, this application proposes an example of a measurement method. The specific process is as follows:

[0054] See Figure 3 , place the sample to be measured 11 at the left focal plane of the objective lens group to ensure that the entrance pupil of the measurement optical path covers the surface area of the sample to be measured;

[0055] See Figure 3 , turn on the laser 8 so that the parallel light beam emitted by it hits the surface of the sample to be measured through the illumination optical path. Control the deflection angle of the galvanometer mirror 7 through a computer program, so as to control the incident light beam angle, and scan the incident angle from 0° to 70° in the backscattering hemisphere space. The lower limit of the sampling interval is limited by the minimum deflection angle of the galvanometer.

[0056] In the case of a single incident angle, the light beam scattered from the surface of the sample is collected by the numerical aperture NA objective lens group of the large optical system in the front group, and through the optical path propagation path shown in the above example, the scattered light beams in different directions in the backscattering space hemisphere direction converge at different positions of the area array detector 9. Therefore, there is a corresponding relationship between the energy detected by a certain pixel on the detector and the light beam in a certain scattering direction and scattering solid angle. Under the condition of a fixed measurement angular resolution, all the scattered BRDF values of a single incident can be obtained, and by scanning the continuous incident angles, the scattering characteristics of the object surface can be measured.

[0057] The calculation method of the bidirectional reflectance distribution function BRDF at any pixel corresponding to the surface of the measured sample 11 on the area array detector 9 is as follows:

[0058]

[0059] Among them, P s is the power of the light ray reflected by the measured sample 11, Ω s is the solid angle of the light ray reflected by the measured sample 11, P i is the optical power incident on the current pixel of the area array detector 9, θ s is the angle of the light ray reflected by the measured sample 11.

[0060] The measurement system of the present invention can, under the conditions of knowing the pixel size, imaging height, distortion size and galvanometer deflection angle of the detector, combine the optical parameters of each component of the measurement instrument system to calculate the scattering light angle and scattering solid angle corresponding to each pixel, so as to obtain all the parameters required for calculating the BRDF.

[0061] The calculation formulas for the scattering angle and solid angle corresponding to a single pixel are mainly derived from the following two formulas:

[0062] y distorted = k·tan(θ)·f

[0063]

[0064] Among them, y distorted is the image height affected by distortion, k is the distortion factor, θ is the scattering angle (zenith angle), f is the focal length of the optical system, Ω S is the scattering space solid angle corresponding to a single pixel, θ and are the zenith angle and azimuth angle respectively, θ1, θ2, and are the integration domains of the angles corresponding to the pixel. The specific calculation process is not difficult, but it will consume a large amount of space. In order to make the present invention concise and clear, it is not elaborated in the present invention.

[0065] By calculating in the above manner, the present invention can obtain the scattering angle direction and the solid angle occupied corresponding to each pixel in the imaging area of the sample. Then, based on the light intensity values obtained on the entire detector, the bidirectional reflectance distribution function of the sample to be measured at nearly hemispherical sampling angles under continuously varying incident angles can be obtained at one time.

[0066] In summary, the present invention provides a galvanometer-based multi-conjugate optical structure BRDF scanner. Referring to Figure 3 , the illumination optical path coincides with the detection optical path and is split into two light paths by a beam splitter. The two optical paths jointly satisfy the following conjugate relationships: the detector 9 is conjugate to the image plane 10 formed by the modulation of the objective lens group, and the entrance pupil 13 of the focusing lens group / the pupil 12 of the galvanometer are respectively conjugate to the sample plane 11. These three pairs of conjugate optical paths partially coincide in the left-side optical path part of the beam splitter 4, making the system more compact.

[0067] Compared with the patent CN202310982576.1, the present system does not require the complex and expensive alignment and detection processes of large-aperture and small-curvature mirrors. The primary image plane generated by the objective lens group of the present system at the rear focal plane enables the objective lens group and the subsequent lens group to be spliced together according to the primary image plane, which is beneficial to the alignment and detection of the objective lens group and the subsequent lens group, and is also convenient for maintenance.

[0068] Secondly, compared with other similar systems, the present invention does not require a complex mechanical structure to drive the light source and the sample to move or rotate to generate relative position changes to obtain incident light at different angles. Instead, a galvanometer assembly is introduced into the system, and the incident light direction is adjusted by controlling the rotation of the galvanometer in a two-dimensional plane to traverse the 0-70° reflection space zenith angle to achieve the scanning effect. This setting also reduces the volume and weight of the instrument and lowers the cost.

[0069] Finally, as described above, the present invention does not require a complex mechanical structure to drive the detector and the sample to move or rotate to generate relative position changes to detect scattered light at different angles. Instead, a area array detector is used to detect the scattered light energy. By placing the area array detector at the conjugate position of the first image plane formed by the modulation of the objective lens group, the corresponding relationship between each pixel and the scattered light at different zenith angles and azimuth angles in the sample reflection space can be obtained. That is to say, the present invention removes the steps of the mechanical component moving step by step and single-point measurement, greatly improving the detection efficiency of the instrument and being applicable to outdoor environments.

[0070] Of course, the present invention may have other various embodiments. Without departing from the spirit and essence of the present invention, those skilled in the art can certainly make various corresponding changes and deformations according to the present invention. However, these corresponding changes and deformations should all fall within the protection scope of the appended claims of the present invention.

Claims

1. A multi-conjugate optical structure BRDF scanner based on a galvanometer, characterized in that: The invention comprises an objective lens group (1), an objective lens group (2), a lens (3), a non-polarized beam splitter prism (4), a focusing lens group lens (5), a focusing lens group lens (6), a galvanometer (7), a laser light source (8) and a surface array detector (9); wherein the objective lens group (1), the objective lens group (2), the relay lens group (3), the non-polarized beam splitter prism (4), the focusing lens group lens (5), the focusing lens group lens (6) and the surface array detector (9) are sequentially placed on the same optical axis along the optical path to form a measurement optical path; the objective lens group (1), the objective lens group (2), the relay lens group (3), the non-polarized beam splitter prism (4), the galvanometer (7) and the laser light source (8) are sequentially placed, and the optical axis is folded 90 degrees at the non-polarized beam splitter prism (4) and the galvanometer (7) to form an illumination optical path; The sample to be tested (11) is placed at the left focal plane of the objective lens group (1), the light beam emitted by the laser light source (8) is incident on the sample to be tested (11) through the illumination light path, and the light reflected by the sample to be tested (11) is incident on the area array detector (9) through the measurement light path to perform a scattering characteristic test on the surface of the sample to be tested (11).

2. A multi-conjugate optical structure BRDF scanner based on a galvanometer as claimed in claim 1, characterized in that: The calculation method of the bidirectional reflectance distribution function BRDF of the surface of the sample (11) under test at any corresponding pixel on the array detector (9) is as follows: Among them, P s is the power of the light reflected by the sample (11), Ω s is the solid angle of the light reflected by the sample (11), P i is the light power incident on the current pixel of the array detector (9), θ s is the angle of the light reflected by the sample (11) being tested.

3. A multi-conjugate optical structure BRDF scanner based on a galvanometer as claimed in claim 2, characterized in that: The solid angle Ω of the light reflected by the sample (11) under test corresponding to a single pixel on the array detector (9) s The calculation method is: Wherein, θ is the zenith angle of the light reflected by the sample (11) under test, is the azimuth angle of the light reflected by the sample (11) under test, θ1 and θ2 are the upper and lower limits of the zenith angle integral corresponding to a single pixel, and They are respectively the upper and lower limits of the azimuth integral corresponding to a single pixel.

4. A multi-conjugate optical structure BRDF scanner based on a galvanometer as claimed in claim 3, characterized in that: The laser light source (8) is turned on so that the parallel light beam it emits hits the surface of the sample to be tested (11) through the illumination light path. The deflection angle of the mirror surface of the galvanometer (7) is controlled by a computer program to continuously change the angle of the light incident on the surface of the sample to be tested (11) until the light traverses the 0° to 70° backscattering hemispherical space formed by the surface of the sample to be tested (11). Finally, the bidirectional reflectance distribution function BRDF of the near hemispherical sampling angle of the sample to be tested (11) under the continuously changing incident angle is obtained, and the scattering characteristics of the surface of the sample to be tested (11) are obtained.

5. The multi-conjugate optical structure BRDF scanner based on a galvanometer as claimed in claim 1, characterized in that: A total focusing lens group consisting of a focusing lens group lens (5) and a focusing lens group lens (6) converges the light beam onto a surface array detector (9) located at the focal length of the total focusing lens group, and scattered light beams in different directions eventually form light spots at different positions of the surface array detector (9); At the same time, there is a corresponding relationship between the energy detected by any pixel on the planar array detector (9) and the light beam corresponding to the scattering direction and scattering solid angle, so under the condition of fixed measurement angular resolution, the entire bidirectional reflection distribution function BRDF of a single incidence can be obtained.

6. The multi-conjugate optical structure BRDF scanner based on a galvanometer as claimed in claim 1, characterized in that: In an initial state, the galvanometer (7) is placed at 45 degrees to the optical axis of the relay lens group lens (3). When it is necessary to change the angle at which the laser light source (8) is incident on the surface of the sample (11) to be measured, the direction of the reflected light at the galvanometer (7) is controlled by controlling the mirror surface of the galvanometer (7) to rotate in a one-dimensional direction, and then the non-polarizing beam splitter (4) reflects the reflected light from the galvanometer (7) into a coaxial light path of the measuring light path and the illumination light path.

7. The multi-conjugate optical structure BRDF scanner based on a galvanometer as claimed in claim 1, characterized in that: The relative positions of the relay lens group lens (3) and the pupil of the galvanometer mirror (7) are as follows: the pupil of the galvanometer mirror (7) is located on the focal plane of the relay lens group lens (3), so that the main rays of all convergent light beams emitted by the relay lens group lens (3) are parallel to the optical axis, presenting an image-side telecentric optical path structure.

8. The multi-conjugate optical structure BRDF scanner based on a galvanometer as claimed in claim 1, characterized in that: The lens (3) converges each field light beam on a primary image plane (10); the relative position relationship between the total objective lens group composed of the objective lens group lens (1) and the objective lens group lens (2) and the primary image plane (10) is as follows: the primary image plane (10) is located on the right focal plane of the total objective lens group, and the pupil of the galvanometer (7) is in a conjugate relationship with the primary image plane (10), so that reflected light at different angles converges at different positions of the primary image plane (10), and is then modulated by the total objective lens group into parallel light beams emitted at different angles.

9. The multi-conjugate optical structure BRDF scanner based on a galvanometer as claimed in claim 1, characterized in that: The relay lens group (3) modulates each light beam into a parallel light beam, which is incident on the pupil of the focusing lens group (5) through the non-polarization beam splitter prism (4). The pupil of the focusing lens group (5) is located at the right focal length of the relay lens group (3) and on the left surface of the focusing lens group (5), so that the main rays of the parallel light beams in each direction intersect at the center of the left surface of the focusing lens group (5).

10. The multi-conjugate optical structure BRDF scanner based on a galvanometer as claimed in claim 1, characterized in that: The left side surface of the objective lens group lens (1), the left side surface of the objective lens group lens (2), the right side surface of the lens (3) and the right side surface of the focusing lens group lens (6) are all 8th-order even-order aspheric surfaces, and the remaining lens surfaces are all spherical surfaces.

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