Volume scattering function measurement technology based on white light interference

Abstract

The invention relates to a volume scattering function measurement technology based on white light interference. A broadband spectrum light source, a color filter, an optical beam splitter, a measurement light path, a length-adjustable reference light path, a measured medium, a polarization beam splitter, an optical beam combiner, a polarization light switch, a photoelectric detector, a signal acquisition and processing unit, a control unit, a reference arm length adjusting unit and a light switch control unit are included. According to the definition of a volume scattering function, a single sensor can be adopted to measure volume scattering intensities at different angles in sequence along a circular trajectory; a plurality of sensors can also be adopted and arranged along a circular trajectory to measure volume scattering intensities at different angles. The measurement of the volume scattering function follows the white light interference technology, and the influence of background light and stray light is overcome. The polarized light switch is controlled to selectively output the horizontal polarization coherent light or the vertical polarization coherent light, and the horizontal polarization or vertical polarization body scattering function of the measured medium can be obtained. A narrow-band spectrum volume scattering function corresponding to a narrow-band band-stop optical filter can be obtained by measuring the volume scattering function of the wide-spectrum light source and combining the narrow-band band-stop optical filter.

Description

Technical Field

[0001] The present invention relates to a volume scattering function measurement technology based on white light interferometry, and more specifically to a method for applying white light interferometry to volume scattering function measurement. Background Art

[0002] Volumetric Scattering Function β ( i )) describes the angular distribution of light scattered by a scattering body in a medium and is an intrinsic optical parameter of the medium. The mathematical definition of the volume scattering function is a scattering volume in the medium. V At the scattering angle i The second derivative of the scattered flux in the direction with respect to the scattering volume and the scattering solid angle and the incident irradiance E The ratio, unit is m −1 sr −1 , , (1) In formula 1, i is the scattering angle, l is the wavelength of light, L represents the scattered light path, that is, the distance between the scatterer and the detector, Φ represents the incident radiation flux, Ω represents the scattering solid angle, E is the incident irradiance, the scatterer volume V With scattering angle i Change and change. β ( i ) will change with the wavelength of Φ l change.

[0003] According to the definition of volume scattering function, the volume scattering function can be measured by using a single sensor along a circular trajectory ( L The volume scattering intensity at different angles can be measured sequentially using the same sensor. Alternatively, multiple sensors can be arranged along a circular trajectory to measure the volume scattering intensity at different angles. Currently, it is difficult to overcome the influence of background light and stray light in the measurement of volume scattering function.

[0004] White light interferometry technology is based on optical interferometers, such as the Michelson interferometer and the Mach–Zehnder interferometer. It has two main characteristics: the light source is broad-spectrum (white light); and the length of the reference arm needs to be dynamically adjusted.

[0005] Because the light source is broadband, interference fringes only appear when the reference and measurement arms are nearly equal in length, meaning all frequencies in the broadband source are nearly coherent. For a constant reference light intensity, the maximum value of the interference fringe envelope is proportional to the intensity of the measurement light. Summary of the Invention

[0006] The purpose of the present invention is to provide a volume scattering function measurement technology based on white light interferometry to solve the problems raised in the above background technology.

[0007] The present invention includes a wide-spectrum light source, a color filter, an optical beam splitter, a measuring optical path, a length-adjustable reference optical path, a measured medium, a polarization beam splitter, an optical beam combiner, a polarization light switch, a photodetector, a signal acquisition and processing unit, a control unit, a reference arm length adjustment unit, and an optical switch control unit.

[0008] The output light of the wide spectrum light source passes through a color filter and is then split into two paths by an optical beam splitter, one path being the initial measurement light and the other being the initial reference light; the initial measurement light is incident on the measurement light path; the initial reference light is incident on the length-adjustable reference light path.

[0009] The measuring light path is composed of a measuring light emitting lens and a measuring light receiving lens. The measuring light emitting lens collimates the initial measuring light into a parallel measuring beam and then irradiates it into the measured medium. The measuring light receiving lens receives scattered light from the measured medium at a fixed angle. The output of the measuring light receiving lens is a measuring light signal.

[0010] The measuring light path takes the geometric center of the measured medium as the center of the circle, the measuring light emitting lens is located at a fixed position on the circumference; the measuring light receiving lens is located at different positions on the circumference; the optical axis of the measuring light receiving lens and the optical axis of the measuring light emitting lens determine the plane where the measuring light path is located; the angle between the optical axis of the measuring light receiving lens and the optical axis of the measuring light emitting lens is the scattering angle of the volume scattering function i ; The circumference diameter is the length of the measuring arm.

[0011] The length-adjustable reference optical path comprises a reference light emitting lens and a reference light receiving lens. The reference light emitting lens collimates the initial reference light into a parallel reference beam, which is then received by the reference light receiving lens. The distance between the reference light emitting lens and the reference light receiving lens is the reference arm length. A reference arm length adjustment unit is used to adjust the reference arm length. The lower limit of the reference arm length adjustment range is less than the measurement arm length, and the upper limit of the reference arm length adjustment range is greater than the measurement arm length. The reference light receiving lens outputs a reference light signal.

[0012] After passing through the polarization beam splitter, the measurement light signal is split into horizontally polarized measurement light and vertically polarized measurement light; after passing through the polarization beam splitter, the reference light signal is split into horizontally polarized reference light and vertically polarized reference light.

[0013] The horizontally polarized measurement light and the horizontally polarized reference light are input into the optical beam combiner to obtain horizontally polarized coherent light. The vertically polarized measurement light and the vertically polarized reference light are input into the optical beam combiner to obtain vertically polarized coherent light. The horizontally polarized coherent light and the vertically polarized coherent light are input into the polarization switch.

[0014] The photodetector converts the optical signal output by the polarization light switch into a corresponding electrical signal; the signal acquisition and processing unit acquires and processes the electrical signal; the control unit is responsible for controlling the entire measurement, adjusting the reference arm length through the reference arm length adjustment unit, and controlling the polarization light switch through the optical switch control unit to select the output of horizontally polarized coherent light or vertically polarized coherent light.

[0015] Fixed measurement light emission lens to determine scattering angle i According to the measurement process of white light interferometry, the reference arm length is adjusted from the lower limit to the upper limit, and the corresponding interference fringes can be measured; the maximum value of the interference fringe envelope is proportional to the scattering angle i The volume scattering intensity of the scattering angle is measured in turn. i The volume scattering intensity of the sample can be calculated according to formula 1. β ( i ).

[0016] The polarization switch is controlled to select the output of horizontally polarized coherent light or vertically polarized coherent light. According to the above measurement process, the horizontally polarized or vertically polarized volume scattering function of the measured medium can be obtained.

[0017] Volume scattering function of a broad spectrum light source β ( i ) After the measurement, a narrow band-stop filter is added to the color filter and the volume scattering function is measured again. β ( i ). By subtracting the two volume scattering functions, we can get the narrowband spectral volume scattering function corresponding to the narrowband band-stop filter. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention.

[0019] Figure 1 , the principle diagram of the volume scattering function measurement based on white light interferometry of the present invention Figure 2 , the white light interference fringe pattern of the present invention Figure 3 , Schematic diagram of the multi-detector fixed measurement optical path of the present invention Figure 4 , Spectral characteristics of the wide spectrum light source and narrow band stop filter of the present invention Figure: 1. Broad-spectrum light source, 2. Color filter, 3. Initial signal light, 4. Optical beam splitter, 5. Initial reference light, 6. Initial measurement light, 7. Reference light emitting lens, 8. Reference light receiving lens, 9. Reference light signal, 10. Reference arm length adjustment unit, 11. Reference arm length, 12. Measurement light emitting lens, 13. Measurement light receiving lens, scattering angle i =0°, 14. Measured medium, 15. Scattered light from the measured medium, 16. Geometric center of the measured medium, 17. Measured optical path circumference, 18. Measured optical path circumference radius R , 19. Measure the optical signal, 20. Measure the light receiving lens, scattering angle i ≠0º, 21. Scattering angle i , 22. Reference light polarization beam splitter, 23. Measurement light polarization beam splitter, 24. Horizontally polarized reference light, 25. Vertically polarized reference light, 26. Horizontally polarized measurement light, 27. Vertically polarized measurement light, 28. Horizontally polarized optical beam combiner, 29. Vertically polarized optical beam combiner, 30. Horizontally polarized coherent light, 31. Vertically polarized coherent light, 32. Polarization switch, 33. Photodetector, 34. Signal acquisition and processing unit, 35. Control unit, 36. Optical switch control unit, 37. Maximum value of the white light interference fringe envelope, 38. Output optical signals of multiple fixed detectors, 39. Multi-way optical switch, 40. Spectrum of a wide-spectrum light source, 41. Spectrum of a narrow-band rejection filter. DETAILED DESCRIPTION

[0020] The present invention aims to provide a volume scattering function measurement technique based on white light interferometry to address technical problems in related fields. To further clarify the technical problems and technical solutions to be solved by the present invention, the present invention is further described below in conjunction with the accompanying drawings and examples. It should be understood that the specific embodiments described herein are intended only to illustrate the present invention and are not intended to limit the present invention.

[0021] The volume scattering function measurement principle based on white light interferometry of the present invention is as follows: Figure 1 shown.

[0022] A wide spectrum light source (1) obtains an initial signal light (3) through a color filter (2), which is then split into an initial reference light (5) and an initial measurement light (6) by an optical beam splitter (4). The initial reference light (5) passes through a reference light emitting lens (7), is collimated into parallel light, and is then received by a reference light receiving lens (8) as a reference light signal (9). The distance between the reference light emitting lens (7) and the reference light receiving lens (8) is a reference arm length (11). Along the direction of the reference light signal (9), a reference arm length adjustment unit (10) moves the position of the reference light emitting lens (7) or the reference light receiving lens (8) to adjust the reference arm length (11). The lower limit of the reference arm length (11) is less than the measurement arm length, and the upper limit of the reference arm length (11) is greater than the measurement arm length.

[0023] The initial measurement light (6) passes through the measurement light emitting lens (12) and is collimated into parallel light. The light is then irradiated into the measured medium (14). The measurement light receiving lens (13) receives the scattered light (15) of the measured medium at a specific angle. The measurement light receiving lens (13) outputs the measured light signal (19).

[0024] The measuring light path is centered at the geometric center (16) of the measured medium. The measuring light emitting lens (12) and the measuring light receiving lens (13) are located on the measuring light path circumference (17). The measuring light emitting lens (12) is fixed on the measuring light path circumference (17). On the plane where the measuring light path circumference (17) is located, the angle between the optical axis of the measuring light receiving lens (13) and the optical axis of the measuring light emitting lens (12) is the scattering angle of the volume scattering function. i (21). Measure the scattering angle corresponding to the light receiving lens (13) i (21)=0º, measure the scattering angle corresponding to the light receiving lens (20) i (21)≠0°. The measuring arm length is equal to twice the radius of the measuring optical path. R (18).

[0025] The reference light signal (9) is split into a horizontally polarized reference light (24) and a vertically polarized reference light (25) after passing through the reference light polarization beam splitter (22). The measurement light signal (19) is split into a horizontally polarized measurement light (26) and a vertically polarized measurement light (27) after passing through the measurement light polarization beam splitter (22).

[0026] The horizontally polarized measurement light (26) and the horizontally polarized reference light (24) pass through a horizontally polarized optical beam combiner (28) to obtain horizontally polarized coherent light (30); the vertically polarized measurement light (27) and the vertically polarized reference light (25) pass through a vertically polarized optical beam combiner (29) to obtain vertically polarized coherent light (31). The horizontally polarized coherent light (30) and the vertically polarized coherent light (31) are input into a polarization switch (32).

[0027] The photodetector (33) converts the optical signal output by the polarization light switch (32) into a corresponding electrical signal; the signal acquisition and processing unit (34) acquires and processes the electrical signal; the control unit (35) is responsible for controlling the entire measurement, adjusting the reference arm length (11) through the reference arm length adjustment unit (10), and controlling the polarization light switch (32) to select the output of horizontally polarized coherent light or vertically polarized coherent light through the optical switch control unit (36).

[0028] The white light interference fringe pattern of the present invention is as follows Figure 2 shown.

[0029] This embodiment uses a single sensor to obtain the volume scattering function of the measured medium through rotation measurement. β ( i ).

[0030] Fixed measurement light receiving lens position, such as Figure 1 In (13), the corresponding scattering angle i =0º, according to the measurement process of white light interferometry, adjust the reference arm length (11) from the lower limit to the upper limit, and measure the corresponding interference fringe pattern, as shown in Figure 2 As shown. The maximum value of the envelope (37) is proportional to i =0° Volume scattering intensity β (0).

[0031] Rotate the measuring light receiving lens along the measuring light path circumference (17) to the position (20), corresponding to the scattering angle i (21). Repeat the above measurement process to obtain β ( i ). By analogy, we can get the volume scattering intensity at any angle from 0 to 2π, and thus get the volume scattering function β ( i ).

[0032] The principle of the multi-detector fixed measurement optical path of the present invention is as follows Figure 3 shown.

[0033] The present invention can also use a multi-detector fixed optical path to realize the volume scattering function of the measured medium β ( i ) measurement.

[0034] Along the circumference of the measuring optical path (17) at different scattering angles iMultiple measuring light receiving lenses (38) are placed at the same time. The outputs of the multiple measuring light receiving lenses (38) are selected by a multi-way optical switch (39). The output of the multi-way optical switch (39) is the measuring light signal (19). According to the measurement process of the white light interferometry technology, the volume scattering intensity of each measuring light receiving lens (38) corresponding to the scattering angle is measured in turn, thereby obtaining the volume scattering function of the measured medium. β ( i ).

[0035] The polarization switch (32) is controlled to select the output of horizontally polarized coherent light (30) or vertically polarized coherent light (31). According to the measurement process of the above embodiment, the horizontally polarized or vertically polarized volume scattering function of the measured medium can be obtained. β ( i ).

[0036] The spectral characteristics of the wide spectrum light source and narrow band rejection filter of the present invention are shown in FIG. Figure 4 shown.

[0037] The comprehensive spectral characteristic of the wide-spectrum light source (1) and the color filter (2) is (40), and the spectral characteristic of the narrow-band stop filter is (41).

[0038] The scattering function of the measured medium corresponding to the wide spectrum light source (1) is measured β ( i ), a narrow band-stop filter with spectral characteristics (41) is superimposed on the color filter (2). According to the previous measurement process, the volume scattering function of the measured medium is obtained again. β ( i ); twice volume scattering function β ( i ) can be subtracted to obtain the volume scattering function of the measured medium corresponding to the spectrum of the narrow-band rejection filter. β ( i ).

[0039] It is obvious to those skilled in the art that the present invention is not limited to the details of the above exemplary embodiments, and that the present invention can be implemented in other specific forms without departing from the spirit or basic characteristics of the present invention. Those skilled in the art should consider the specification as a whole, and the technical solutions in the various embodiments can also be appropriately combined to form other implementation methods that can be understood by those skilled in the art.

Claims

1. A volume scattering function measurement technique based on white light interferometry, characterized by: It consists of a wide-spectrum light source, a color filter, an optical beam splitter, a measuring optical path, a length-adjustable reference optical path, a measured medium, a polarization beam splitter, an optical beam combiner, a polarization switch, a photodetector, a signal acquisition and processing unit, a control unit, a reference arm length adjustment unit, and an optical switch control unit. The output light of the wide spectrum light source is divided into two paths by an optical beam splitter after passing through a color filter, one path being the initial measurement light and the other being the initial reference light; the initial measurement light is incident on the measurement light path; the initial reference light is incident on the length-adjustable reference light path; The measuring light path is composed of a measuring light emitting lens and a measuring light receiving lens. The measuring light emitting lens collimates the initial measuring light into a parallel measuring beam and then irradiates it into the measured medium. The measuring light receiving lens receives the scattered light of the measured medium at a fixed angle. The output of the measuring light receiving lens is a measuring light signal. The measuring light path takes the geometric center of the measured medium as the center of the circle, the measuring light emitting lens is located at a fixed position on the circumference; the measuring light receiving lens is located at different positions on the circumference; the optical axis of the measuring light receiving lens and the optical axis of the measuring light emitting lens determine the plane where the measuring light path is located; the angle between the optical axis of the measuring light receiving lens and the optical axis of the measuring light emitting lens is the scattering angle of the volume scattering function θ ;The circumference diameter is the length of the measuring arm; The length-adjustable reference light path is composed of a reference light emitting lens and a reference light receiving lens. The reference light emitting lens collimates the initial reference light into a parallel reference beam, which is then received by the reference light receiving lens. The distance between the reference light emitting lens and the reference light receiving lens is the reference arm length. The reference arm length adjustment unit is used to adjust the reference arm length; the lower limit of the reference arm length adjustment range is less than the measuring arm length, and the upper limit of the reference arm length adjustment range is greater than the measuring arm length; the reference light receiving lens outputs a reference light signal; After passing through the polarization beam splitter, the measurement light signal is split into horizontally polarized measurement light and vertically polarized measurement light; after passing through the polarization beam splitter, the reference light signal is split into horizontally polarized reference light and vertically polarized reference light; The horizontally polarized measurement light and the horizontally polarized reference light are input into the optical beam combiner to obtain horizontally polarized coherent light; the vertically polarized measurement light and the vertically polarized reference light are input into the optical beam combiner to obtain vertically polarized coherent light; the horizontally polarized coherent light and the vertically polarized coherent light are input into the polarization switch; The photodetector converts the optical signal output by the polarization switch into a corresponding electrical signal; the signal acquisition and processing unit acquires and processes the electrical signal; the control unit is responsible for controlling the entire measurement, adjusting the reference arm length through the reference arm length adjustment unit, and controlling the polarization switch through the optical switch control unit to select the output of horizontally polarized coherent light or vertically polarized coherent light; Fixed measurement light emission lens to determine scattering angle θ According to the measurement process of white light interferometry, the reference arm length is adjusted from the lower limit to the upper limit, and the corresponding interference fringes can be measured; the maximum value of the interference fringe envelope is proportional to the scattering angle θ The volume scattering intensity of Measure different scattering angles in sequence θ The volume scattering intensity of the sample can be calculated according to the definition of the volume scattering function (1): β(θ) , ， (1) In formula 1, θ is the scattering angle, λ is the wavelength of light, L represents the scattered light path, that is, the distance between the scatterer and the detector, Φ represents the incident radiation flux, Ω represents the scattering solid angle, E is the incident irradiance, the volume of the scatterer V With scattering angle θ Change and change.

2. The volume scattering function measurement technology based on white light interferometry according to claim 1, characterized in that: The polarization switch is controlled to select the output of horizontally polarized coherent light or vertically polarized coherent light. According to the above measurement process, the horizontally polarized or vertically polarized volume scattering function of the measured medium can be obtained.

3. The volume scattering function measurement technology based on white light interferometry according to claim 1, characterized in that: Volume scattering function of a broad spectrum light source β(θ) After the measurement, a narrow band-stop filter is added to the color filter and the volume scattering function is measured again. β(θ) ; By subtracting the two volume scattering functions, we can get the narrowband spectral volume scattering function corresponding to the narrowband band-stop filter.

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