Testing device and testing method for measuring reflection characteristics of material surface based on bidirectional reflection distribution function

Abstract

The invention provides a testing device and a testing method for measuring reflection characteristics of a material surface based on a bidirectional reflection distribution function. A to-be-detected sample is arranged in the middle of a sample bearing table, detection light generated by a light source system in the device irradiates the surface of a material, and after the detection light is reflected by the surface of the to-be-detected sample, a data acquisition system controls a photoelectric detector to rotate to different zenith angles and azimuth angles to complete data acquisition; by adjusting any incident angle, zenith angle and azimuth angle, the surface reflection light radiation brightness value of the to-be-measured sample in the whole 2pi space range is obtained, calculation is carried out according to the collected data and the calculation formula of the bidirectional reflection distribution function, and finally the surface reflection characteristics of the to-be-measured sample are obtained.

Description

Technical Field

[0001] The present invention relates to the field of measuring material reflected light distribution characteristics, and in particular to a testing device and a testing method for measuring material surface reflection characteristics based on a bidirectional reflection distribution function. Background Art

[0002] Inertial sensors are the core payload of space gravitational wave detection. Gravitational wave detection uses the test mass of the inertial sensor as a reference for light reflection and satellite positioning, and requires strict control of acceleration interference noise. Since the test mass is in an isolated and suspended state inside the inertial sensor, it accumulates charge due to particle radiation. The charge carried by the test mass will be affected by electrostatic force and Lorentz force. As the charge accumulates, these noises will inevitably affect the scientific detection of gravitational waves, so it is necessary to control the charge of the test mass. The inertial sensor charge management system is based on the photoelectric effect. It controls the ultraviolet light irradiation on the surface of the inertial sensor to control the photoelectrons to deviate from or be incident on the test mass, thereby realizing the charge control of the test mass. It is one of the important components of the drag-free control of the satellite platform. According to the UV discharge control principle, the surface of the inertial sensor material is gold-plated. Parameters such as light absorption and reflectivity of the gold-plated surface have an important influence on charge management.

[0003] In optics, the reflection of light by a surface is generally divided into two categories, namely specular reflection and diffuse reflection. However, in reality, there are no absolute specular reflection surfaces or absolute diffuse reflection surfaces. Therefore, it is necessary to find a parameter that can reasonably describe various reflection conditions. In the study of the scattering properties of material surfaces, the bidirectional reflectance distribution function (BRDF) is used to characterize the surface reflection properties of materials. It is a basic optical property of materials that is only related to the properties of the material surface itself.

[0004] Bidirectional reflectance distribution function (BRDF) is a physical quantity used to describe the scattering characteristics of an object surface, describing the distribution of the reflection spectrum of the material surface in the 2π space under different incident directions. It is defined as: the ratio between the micro-increment of the incident surface irradiance in a specific direction and the increment of the reflected radiation brightness in the direction caused by it:

[0005]

[0006] The calculation formula is:

[0007]

[0008] Where the subscripts (i, r) denote incident and divergent; Ωr is the solid angle at which the scattered radiation is measured; and cos(θi) is a correction factor used to adjust the illuminated area to its apparent size when viewed from the scattered direction. Relative to the surface normal are the azimuth and zenith angles; Lr represents the angle relative to the incident direction The corresponding reflection direction The radiation brightness; Lo represents the incident direction The incident light radiance under .

[0009] The BRDF of gold-plated materials characterizes their inherent properties. By measuring the BRDF value of the gold-plated material surface, the distribution of scattered light in the 2π space under UV light can be obtained. The scattering characteristics are used to describe the propagation and diffusion path of incident stray light on the surface of optical components, and are the basis for accurate stray light simulation analysis.

[0010] There are two methods for measuring BRDF: absolute measurement and relative measurement. The absolute measurement method refers to the measurement without any reference standard according to the definition of BRDF, that is, the incident irradiance and reflected radiance are measured by a radiometer and a luminance meter respectively, and the ratio of the two is the BRDF. Summary of the invention

[0011] The present invention provides an absolute measurement device based on bidirectional reflection distribution function. The device accurately measures the bidirectional reflection distribution function values ​​of different material surfaces by adjusting the incident angle, the emission zenith angle and the azimuth angle. The device has a simple structure and a simple and easy-to-operate electromechanical control system. The entire measuring device includes an illumination system, a detection system, a mechanical motion system and a data processing system. During the measurement process, the control software of the mechanical motion system is integrated into a control interface through the interface software, and the entire measurement process of the experiment is automatically controlled by a computer, so that the experiment is easy, fast and accurate to operate.

[0012] The technical solution of the present invention is as follows:

[0013] A measuring device based on bidirectional reflectance function distribution, an illumination system, a photomultiplier tube, a measuring electromechanical system, a control system and a data processing system;

[0014] The lighting system comprises an optical fiber, a light source and a light outlet, wherein the input end of the optical fiber is connected to the light source, the output end of the optical fiber is connected to the light outlet, and the light outlet is used to emit light emitted by the light source at different light incident angles;

[0015] The photomultiplier tube is used to convert the light emitted by the optical fiber into an electrical signal and send it to the data processing system;

[0016] The measuring electromechanical system includes a first stepper motor, a second stepper motor, a third stepper motor, a fourth stepper motor and a sample carrier; the sample carrier is used to place the sample to be measured and the sample carrier can be lifted and lowered; the first stepper motor is used to adjust the vertical plane position of the photomultiplier tube to adjust the reflection zenith angle; the second stepper motor is used to adjust the horizontal plane position of the photomultiplier tube to adjust the reflection azimuth angle; the fourth stepper motor is used to adjust the incident angle of the light emitted by the optical fiber; the third stepper motor provides power for the lifting and lowering of the sample carrier;

[0017] The data processing system is composed of an oscilloscope, which is used to amplify the received electrical signal and display it on the oscilloscope;

[0018] The control system is used to control the rotation of the first stepper motor, the second stepper motor and the fourth stepper motor in the measuring electromechanical system, thereby controlling the changes of the reflection zenith angle, the reflection azimuth angle and the light incident angle.

[0019] As a preferred embodiment of the present invention, the measuring electromechanical system also includes a first cantilever beam and a second cantilever beam; the light source is arranged in the middle part of the first cantilever arm, the fourth stepper motor is transmission-connected to the first cantilever arm, and the fourth stepper motor controls the rotation of the first cantilever arm to adjust the incident angle; the sample carrier is used to place the sample to be measured and the sample carrier can be raised and lowered; the second cantilever beam includes a horizontal rod and a vertical rod, one end of the horizontal rod is connected to a gear plate mounted on the sample carrier, the gear plate can rotate around the sample carrier, and the other end of the horizontal rod is vertically fixed to the vertical rod; a first stepper motor is arranged on the vertical rod; the second stepper motor is meshed with the gear plate through gears, and the second stepper motor is used to provide horizontal rotation power for the second cantilever beam to adjust the reflection azimuth angle; the first stepper motor controls the rotation of the photomultiplier tube to adjust the reflection zenith angle.

[0020] A displacement platform is also provided between the first stepper motor and the photomultiplier tube, and the displacement platform is used to adjust the distance between the photomultiplier tube and the sample supporting platform.

[0021] As a preferred solution of the present invention, the sampling angle interval of the reflection azimuth angle and the reflection zenith angle can be set arbitrarily, and the speed of the stepper motor can also be set arbitrarily to achieve all-round measurement coverage.

[0022] The present invention also provides a measurement method using the above-mentioned measurement device, comprising the following steps:

[0023] 1) placing the installed measuring device in a dark box, starting the lighting system to provide the required incident light; controlling the rotation of the first stepper motor, the second stepper motor and the fourth stepper motor in the measuring electromechanical system by the control system, thereby adjusting the incident angle, the reflection azimuth angle and the reflection zenith angle, so that the incident light is directly received by the photomultiplier tube without reflection, reading the electrical signal sent by the photomultiplier tube by an oscilloscope and converting it into a corresponding radiation brightness value, and recording the original incident light radiation brightness value;

[0024] 2) placing a standard diffuse reflection sample on the sample carrier and placing the entire device in a dark box, adjusting the incident angle, reflection azimuth angle, and zenith angle through the control system, and recording the values ​​of the oscilloscope at different incident angles, reflection zenith angles, and azimuth angles;

[0025] 3) Place the sample to be tested on the sample carrier and clamp it with a sample clamp, then place the entire device in a dark box, fix the incident light angle and the reflection zenith angle, change the reflection azimuth angle through the second stepper motor, record the oscilloscope voltage value and convert it into the corresponding reflected light radiation brightness value;

[0026] 4) changing the reflection zenith angle by the first stepper motor, repeating the operation of step 3), and measuring the reflected light radiation brightness value under the fixed incident light angle within the entire 2π space range; the 2π space is the space range covered by a hemisphere with the surface of the sample to be measured as the center and the distance from the optical fiber output end to the surface of the sample to be measured as the radius;

[0027] 5) The incident angle of the light source is changed by the fourth stepper motor, and the operations of steps 3) and 4) are repeated to measure the radiation brightness value of the reflected light at different incident angles, and finally the surface reflection characteristics of the sample to be tested are obtained by calculating the calculation formula of the bidirectional reflection distribution function.

[0028] Compared with the prior art, the present invention has the following beneficial effects:

[0029] The invention is equipped with a reducer when the motor rotates, and can realize accurate control of the rotation angle with an accuracy of up to 1° while realizing the illumination zenith angle of 0-180°, the reflection azimuth angle of 0-360°, and the reflection zenith angle of 0-180° without dead angle rotation. At the same time, a high-power wide-spectrum output light source and a wide-detection range photomultiplier tube are used to comprehensively measure the bidirectional reflection distribution of different samples at different light wavelengths. At the same time, the device is also equipped with a dark box, which can avoid the influence of external stray light to the greatest extent during measurement. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 It is a schematic diagram of the bidirectional reflectance function measuring device of the present invention.

[0031] Figure 2 This is the control interface operation diagram.

[0032] Among them: 1. photomultiplier tube, 2. displacement platform, 3. first stepper motor, 4. first reducer, 5. sample carrier, 6. second stepper motor, 7. third stepper motor, 8. tripod support frame, 9. second reducer, 10. fourth stepper motor, 11. light outlet, 12. optical fiber, 13. light source. DETAILED DESCRIPTION

[0033] The technical solutions in the embodiments of the present invention will be described clearly and completely below in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative work are within the scope of protection of the present invention.

[0034] like Figure 1 As shown, the present invention provides a measuring device for measuring the reflective characteristics of a material surface based on a bidirectional reflectance distribution function, comprising a base, a support column, an illumination system, a photomultiplier tube 1, a measuring electromechanical system, a control system and a data processing system;

[0035] Two support columns are fixed on the base and a space for setting up a measuring electromechanical system is reserved between the two support columns; the measuring electromechanical system includes a first cantilever beam, a second cantilever beam, a first stepper motor 3, a second stepper motor 6, a third stepper motor 7, a fourth stepper motor 10, a displacement platform 2, a first reducer 4, a second reducer 9, a triangular support frame 8 and a sample carrier 5; the second stepper motor 6, the third stepper motor 7 and the sample carrier 5 are all fixed on the base, the sample carrier 5 is used to place the sample to be tested and the sample carrier can be lifted and lowered; the second cantilever beam includes a horizontal rod and a vertical rod, one end of the horizontal rod is connected to a gear sleeved on the sample carrier 5 The wheel and gear plate can rotate around the sample carrier 5, and the other end of the horizontal rod is vertically fixed to the vertical rod; the first stepper motor 3 is arranged on the vertical rod; the second stepper motor 6 is meshed with the gear plate through the gear, and the second stepper motor 6 is used to provide the second cantilever beam with power for horizontal rotation, so as to adjust the reflection azimuth; the third stepper motor 7 is connected with the sample carrier 5 in a transmission manner, and the third stepper motor 7 provides power for the lifting of the sample carrier 5; the first reducer 4 is fixed on the upper end of the second stepper motor, and the first reducer 4 can reduce the rotation speed of the fourth stepper motor 10, so as to realize the high-precision rotation of the first cantilever arm in the horizontal direction, so as to realize the precise control of the incident zenith angle. The second reducer 9 is fixed by the triangular support frame 8, and the second reducer 9 can reduce the rotation speed of the second and third stepper motors 7, so as to realize the high-precision rotation of the second cantilever beam wall in the horizontal and vertical directions, so as to realize the precise control of the reflection azimuth angle and the zenith angle.

[0036] A first stepper motor 3 is fixed on the first reducer 4, a displacement platform 2 is arranged on the first stepper motor 3, and a photomultiplier tube 1 is fixed on the displacement platform 2; the photomultiplier tube 1 is used to convert the light reflection signal into an electrical signal and send it to the data processing system; the first cantilever beam is hinged at the upper ends of the two supporting columns, and a fourth stepper motor 10 is arranged at the hinge between the first cantilever beam and one of the supporting columns, and the rotation of the first cantilever beam is adjusted by the fourth stepper motor 10.

[0037] The lighting system includes an optical fiber, a light source, and a light outlet. The input end of the optical fiber is connected to the light source, and the output end of the optical fiber is connected to the light outlet. The light outlet is used to emit light emitted by the light source at different light incident angles. The light outlet is arranged in the middle of the first cantilever arm. The displacement platform 2 is connected to the first stepper motor 3 and the photomultiplier tube 1 is fixed on the displacement platform 2. The first stepper motor 3 controls the rotation of the photomultiplier tube 1 to adjust the reflection zenith angle. The fourth stepper motor 10 controls the rotation of the incident angle.

[0038] The photomultiplier tube 1 is used to convert the light reflection signal into an electrical signal and send it to the data processing system; the data processing system is composed of an oscilloscope, which is used to amplify the received electrical signal and display it on the oscilloscope; the control system is used to control the rotation of the first stepper motor 3, the second stepper motor 6, the third stepper motor 7 and the fourth stepper motor 10 in the measuring electromechanical system, thereby controlling the changes in the reflection zenith angle, the reflection azimuth angle and the light incident angle.

[0039] The method for measuring by the absolute measuring device of the bidirectional reflectance distribution function of the present invention comprises the following steps:

[0040] 1) The ultraviolet light source optical fiber is arranged on the first cantilever arm of the measuring electromechanical system, and the photomultiplier tube 1 is placed on the second cantilever arm of the measuring electromechanical system; the photomultiplier tube 1 is connected to the oscilloscope, the optical fiber is connected to the ultraviolet light source, and then the entire absolute measurement device is placed in a dark box;

[0041] 2) adjusting the incident angle, reflection azimuth angle and zenith angle through the control system so that the light source is directly received by the photomultiplier tube 1 without reflection, taking the electrical signal sent by the photomultiplier tube 1 through the oscilloscope and converting it into the corresponding radiation brightness value; recording the original incident light radiation brightness value;

[0042] 3) After placing the standard diffuse reflection sample on the sample support platform 5, the entire device is placed in a dark box to record the oscilloscope values ​​at different incident angles, reflection zenith angles, and azimuth angles;

[0043] 4) Place the sample on the sample stage and clamp it with a sample clamp, then place the entire device in a dark box, fix the incident light angle to 15°, fix the reflection zenith angle to 15°, change the azimuth angle through the second stepper motor 6, the step value can be changed according to the measurement requirements, the minimum step angle can reach 1°, and the range is set to 0° to 180°, record the oscilloscope voltage value and convert it into the corresponding reflected light radiation brightness value;

[0044] 5) Change the reflection zenith angle to 30°, repeat the above operation 4), and continue to adjust the reflection zenith angle by the first stepper motor 3, with a step value of 15° and a range of 0° to 90°, so as to expand the measurement range to the entire 2π space range;

[0045] 6) Change the incident angle by the fourth stepper motor 10, the step value is 15°, the range is 0°~90°, repeat the operations of steps 3) and 4), measure the radiation brightness value under different incident angles, and finally calculate the BRDF value of the sample to be tested to obtain the surface reflection characteristics of the sample to be tested.

[0046] like Figure 2 In a specific embodiment of the present invention, the control system is regulated through a visual control interface, and during the control process:

[0047] The rotating motor is the first stepper motor, which is used to control the reflection azimuth angle;

[0048] The photo motor is the second stepper motor, which is used to control the reflection zenith angle;

[0049] The lamp stand motor is the fourth stepper motor, which is used to control the incident zenith angle;

[0050] The carrier motor is the third stepper motor, which is used to control the movement of the sample stage.

[0051] Among them, in the position setting, the range of the second stepper motor and the fourth stepper motor is -90°—90°; the range of the first stepper motor is -180°—180°; and the range of the third stepper motor is -10cm—10cm.

[0052] In speed setting, the range of the first, second, and fourth stepper motors is 0° / sec - 180° / sec; the range of the third stepper motor is 1cm / sec - 10cm / sec.

[0053] Jog control: Set the motor speed to achieve precise step position changes in the forward and reverse directions, and accurately see the real-time speed and position of the motor;

[0054] Continuous control: Set the motor position and speed to achieve precise position changes in the forward and reverse directions, and change speed, and accurately see the real-time position of the motor;

[0055] Set origin: Set different starting points for changes according to needs.

[0056] In a specific embodiment of the present invention, the control method of the absolute measurement device of the bidirectional reflectance distribution function of the present invention is specifically:

[0057] 1) operating a control system, controlling the positions of the first cantilever arm, the horizontal bar and the numerical bar of the second cantilever arm and the stage by controlling four motors, so as to achieve an incident zenith angle of 0°, a reflection azimuth angle of 0°, and a reflection zenith angle of 0°; the stage and the first cantilever arm and the second cantilever arm are coaxial in the horizontal direction;

[0058] 2) placing the ultraviolet light source optical fiber on the first cantilever arm of the measuring electromechanical system, and placing the photomultiplier tube on the second cantilever arm of the measuring electromechanical system; connecting the photomultiplier tube to an oscilloscope, connecting the optical fiber to the ultraviolet light source, and then placing the entire absolute measurement device in a dark box;

[0059] 3) operating the control system, using continuous control to set the fourth stepper motor position to 90°, the speed to 10° / s, so that the incident zenith angle is 90°, and also using continuous control to set the third stepper motor position to -90°, the speed to 10° / s, and the reflection zenith angle to -90°; so that the light source is directly incident on the radio and television multiplier tube without passing through the sample, and the oscilloscope value is recorded. In a specific embodiment of one side of the present invention, the data are shown in Table 1;

[0060] Table 1. Optical power measured by incident light directly incident (μw)

[0061]

[0062] 4) Repeat step 1) to achieve an incident zenith angle of 45°, a reflection azimuth angle of 0°, and a reflection zenith angle of 0°;

[0063] 5) Open the darkroom, place the sample on the sample stage and then close the darkroom;

[0064] 6) Operate the control system, fix the incident light angle to 45°, fix the reflection zenith angle to 0°, set the second stepper motor position setting to 15°, and the speed setting to 10° / s, so as to achieve a step value of 15°, and record the values ​​of the reflection azimuth angles of 0°, 15°, 30°, 45°, 60°, 75°, and 90° on the oscilloscope in sequence;

[0065] 7) Operate the control system, fix the incident light angle to 45°, fix the reflection zenith angle to 15°, and then repeat the above step 6) to record the values ​​on the oscilloscope in sequence;

[0066] 8) Operate the control system, fix the incident light angle at 45°, and sequentially fix the reflection zenith angle at 30°, 45°, 60°, 75°, and 90°, and repeat steps 6) and 7);

[0067] 9) The obtained oscilloscope values ​​are recorded in sequence. In a specific embodiment of one side of the present invention, the data are shown in Table 2. The radiant brightness value and the radiant brightness value of the incident light at each azimuth angle are obtained by the linear characteristics of the photomultiplier tube, and then the reflection characteristics of the material surface are obtained according to the BRDF calculation formula.

[0068] Table 2. Optical power values ​​measured on 1 / 4 hemisphere (μw)

[0069]

[0070] The above-mentioned embodiments only express several implementation methods of the present invention, and the description is relatively specific and detailed, but it cannot be understood as limiting the scope of the present invention. For ordinary technicians in this field, several modifications and improvements can be made without departing from the concept of the present invention, which all belong to the protection scope of the present invention.

Claims

1. A measuring device for measuring the surface reflection characteristics of a material based on a bidirectional reflection distribution function, characterized in that: include: Lighting system, photomultiplier tube, measurement electromechanical system, control system and data processing system; The lighting system comprises an optical fiber, a light source and a light outlet, wherein the input end of the optical fiber is connected to the light source, the output end of the optical fiber is connected to the light outlet, and the light outlet is used to emit light emitted by the light source at different light incident angles; The photomultiplier tube is used to convert the light emitted by the optical fiber into an electrical signal and send it to the data processing system; The measuring electromechanical system comprises a first stepper motor, a second stepper motor, a third stepper motor, a fourth stepper motor and a sample carrier; the sample carrier is used to place the sample to be measured and the sample carrier can be raised and lowered; the first stepper motor is used to adjust the vertical plane position of the photomultiplier tube to adjust the reflection zenith angle; the second stepper motor is used to adjust the horizontal plane position of the photomultiplier tube to adjust the reflection azimuth angle; the fourth stepper motor is used to adjust the incident angle of the light emitted by the optical fiber; The third stepper motor provides power for the lifting and lowering of the sample carrier; The data processing system is composed of an oscilloscope, which is used to amplify the received electrical signal and display it on the oscilloscope; The control system is used to control the rotation of the first stepper motor, the second stepper motor and the fourth stepper motor in the measuring electromechanical system, thereby controlling the changes of the reflection zenith angle, the reflection azimuth angle and the light incident angle.

2. A device for measuring the surface reflection characteristics of a material using a bidirectional reflectance distribution function according to claim 1, characterized in that: The measuring electromechanical system also includes a first cantilever beam and a second cantilever beam; the light source is arranged in the middle part of the first cantilever arm, the fourth stepper motor is transmission-connected to the first cantilever arm, and the fourth stepper motor controls the rotation of the first cantilever arm to adjust the incident angle; the sample carrier is used to place the sample to be measured and the sample carrier can be lifted and lowered; the second cantilever beam includes a horizontal rod and a vertical rod, one end of the horizontal rod is connected to a gear plate mounted on the sample carrier, the gear plate can rotate around the sample carrier, and the other end of the horizontal rod is vertically fixed to the vertical rod; a first stepper motor is arranged on the vertical rod; the second stepper motor is meshed with the gear plate through a gear, and the second stepper motor is used to provide horizontal rotation power for the second cantilever beam to adjust the reflection azimuth angle; the first stepper motor controls the rotation of the photomultiplier tube to adjust the reflection zenith angle.

3. A device for measuring the surface reflection characteristics of a material using a bidirectional reflectance distribution function according to claim 2, characterized in that: A displacement platform is also provided between the first stepper motor and the photomultiplier tube, and the displacement platform is used to adjust the distance between the photomultiplier tube and the sample supporting platform.

4. The device for measuring the surface reflection characteristics of a material using a bidirectional reflectance distribution function according to claim 1, characterized in that: The first cantilever beam and the second cantilever beam are constructed of aluminum alloy profiles.

5. The device for measuring the reflectivity of a material surface using a bidirectional reflectance distribution function according to claim 1, characterized in that: The light source is an ultraviolet light source.

6. The device for measuring the reflective characteristics of a material surface using a bidirectional reflectance distribution function according to claim 1, characterized in that: The axis for adjusting the reflection zenith angle and the axis for adjusting the incident angle of light are in the same horizontal plane.

7. The device for measuring the surface reflection characteristics of a material using a bidirectional reflectance distribution function according to claim 1, characterized in that: The sampling angle interval of the reflection azimuth angle and the reflection zenith angle can be set arbitrarily, and the stepper motor speed can also be set arbitrarily to achieve all-round measurement coverage.

8. A measuring method using the measuring device according to claim 1, characterized in that: The following steps are involved: 1) placing the installed measuring device in a dark box, starting the lighting system to provide the required incident light; controlling the rotation of the first stepper motor, the second stepper motor and the fourth stepper motor in the measuring electromechanical system by the control system, thereby adjusting the incident angle, the reflection azimuth angle and the reflection zenith angle, so that the incident light is directly received by the photomultiplier tube without reflection, reading the electrical signal sent by the photomultiplier tube by an oscilloscope and converting it into a corresponding radiation brightness value, and recording the original incident light radiation brightness value; 2) placing a standard diffuse reflection sample on the sample carrier and placing the entire device in a dark box, adjusting the incident angle, reflection azimuth angle, and zenith angle through the control system, and recording the values ​​of the oscilloscope at different incident angles, reflection zenith angles, and azimuth angles; 3) Place the sample to be tested on the sample carrier and clamp it with a sample clamp, then place the entire device in a dark box, fix the incident light angle and the reflection zenith angle, change the reflection azimuth angle through the second stepper motor, record the oscilloscope voltage value and convert it into the corresponding reflected light radiation brightness value; 4) changing the reflection zenith angle by the first stepper motor, repeating the operation of step 3), and measuring the reflected light radiation brightness value under the fixed incident light angle within the entire 2π space range; the 2π space is the space range covered by a hemisphere with the surface of the sample to be measured as the center and the distance from the optical fiber output end to the surface of the sample to be measured as the radius; 5) The incident angle of the light source is changed by the fourth stepper motor, and the operations of steps 3) and 4) are repeated to measure the radiation brightness value of the reflected light at different incident angles, and finally the surface reflection characteristics of the sample to be tested are obtained by calculating the calculation formula of the bidirectional reflection distribution function.

9. The measuring method according to claim 8, characterized in that: The step angles of the first stepper motor, the second stepper motor and the fourth stepper motor can be changed according to the measurement requirements, and the minimum step angle can reach 1°; the step ranges of the first stepper motor and the fourth stepper motor are both 0° to 90°, and the step range of the second stepper motor is 0° to 180°.

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