Light beam attenuation coefficient measurement technology based on white light interference

Abstract

The invention relates to a light beam attenuation coefficient 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 and a light switch control unit are included. The measurement of the light beam attenuation coefficient follows the white light interference technology, and the influence of background light and stray light is overcome. The polarization 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 beam attenuation coefficient of the measured medium can be obtained. The light beam attenuation coefficient of the wide-spectrum light source is measured, and the narrow-band band-stop optical filter is combined, so that the narrow-band spectrum light beam attenuation coefficient corresponding to the narrow-band band-stop optical filter can be obtained.

Description

Technical Field

[0001] The present invention relates to a light beam attenuation coefficient measurement technology based on white light interference, and more specifically to a method for applying white light interference to light beam attenuation coefficient measurement. Background Art

[0002] The beam attenuation coefficient of light in a medium is an inherent optical property of the medium. When a parallel beam of light is transmitted in a homogeneous medium, the transmission characteristics satisfy the Lambert-Beer law: F ( l ) = F 0 × e -μ(λ)l , (1) in, F 0 is the initial luminous flux, l is the wavelength of light, l is the medium length, F is the luminous flux after passing through the medium, m is the beam attenuation coefficient of the medium, also known as the linear attenuation coefficient 。

[0003] According to formula 1, F / F 0 is the transmittance of the medium. l = 1 meter, T = F / F 0 = e -μ The transparency of the medium. In photometry, the transparency of the medium has nothing to do with the external light intensity, but only with the beam attenuation coefficient of the light in the medium. m It is an inherent optical property. Currently, it is difficult to overcome the influence of background light and stray light in the measurement of beam attenuation coefficient.

[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 a wide 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 light beam attenuation coefficient measurement technology based on white light interference 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, 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.

[0009] The measuring light path is composed of a measuring light emitting lens and a measuring light receiving lens, which are coaxial. The measuring light emitting lens collimates the initial measuring light into a parallel beam, which is then irradiated into the measured medium. The output of the measuring light receiving lens is the transmitted light of the measured medium. The distance between the measuring light emitting lens and the measuring light receiving lens is the measuring arm length.

[0010] The length-adjustable reference light path is composed of a reference light emitting lens and a reference light receiving lens on the same optical axis; the reference light emitting lens collimates the initial reference light into a parallel beam, which is then received by the reference light receiving lens, and the reference light receiving lens outputs the reference light; 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 is less than the measuring arm length, and the upper limit of the reference arm length is greater than the measuring arm length.

[0011] The transmitted light of the measured medium is divided into horizontally polarized measurement light and vertically polarized measurement light after passing through the measurement light polarization beam splitter; the reference light is divided into horizontally polarized reference light and vertically polarized reference light after passing through the reference light polarization beam splitter.

[0012] The horizontally polarized measurement light and the horizontally polarized reference light are input into the horizontal polarization optical combiner to obtain horizontally polarized coherent light. The vertically polarized measurement light and the vertically polarized reference light are input into the vertical polarization optical combiner to obtain vertically polarized coherent light. The horizontally polarized coherent light and the vertically polarized coherent light are input into the polarization switch.

[0013] 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; and the control unit is responsible for controlling the entire measurement, adjusting the reference arm length by controlling the reference arm length adjustment unit and selecting to output horizontally polarized coherent light or vertically polarized coherent light by controlling the polarization switch.

[0014] Fixed measuring light emitting lens and measuring light receiving lens, corresponding to the measuring arm length LAccording to the measurement process of white light interferometry, the reference arm length is adjusted from the lower limit to the upper limit to measure the corresponding interference fringes. The maximum value of the interference fringe envelope is proportional to the luminous flux after passing through the medium. According to the Lambert-Beer law, it can be obtained: F 1 = F 0 × e -μL (2) Change the position of the measuring light receiving lens and determine the new measuring arm length L +Δ L 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 are measured. From the maximum value of the interference fringe envelope, according to the Lambert-Beer law, we can obtain: F 2 = F 0 × e -μ(L+ΔL) . (3) According to equations (2) and (3), the beam attenuation coefficient of the measured medium can be calculated: m : m = ln( F 1 / F 2 ) / Δ L . (4) The polarization switch is controlled to select the output of horizontally polarized coherent light or vertically polarized coherent light. According to the measurement process of formula 4, the attenuation coefficient of the horizontally polarized or vertically polarized light beam of the measured medium can be obtained.

[0015] After measuring the beam attenuation coefficient of the measured medium corresponding to the wide-spectrum light source, a narrow-band rejection filter is added to the color filter and the beam attenuation coefficient of the measured medium is measured again according to the measurement process of Formula 4. By subtracting the two beam attenuation coefficients, the beam attenuation coefficient of the measured medium corresponding to the spectrum of the narrow-band rejection filter can be obtained. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings required for the embodiments. Obviously, the drawings described below are only some embodiments of the present invention.

[0017] Figure 1 , the principle diagram of the measurement of beam attenuation coefficient based on white light interference of the present invention Figure 2 , the white light interference fringe pattern of the present invention Figure 3 , 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 transmitting lens, 8. Reference light receiving lens, 9. Reference light, 10. Reference arm length adjustment unit, 11. Reference arm length, 12. Measurement light transmitting lens, 13. Measurement light receiving lens, 14. Light transmitted through the measured medium, 15. Measurement arm length, 16. Reference light polarization beam splitter, 17. Horizontally polarized reference light, 18. Vertically polarized reference light, 19. Measurement light polarization beam splitter, 20. Horizontally polarized measurement light, 21. Vertically polarized measurement light, 22. Horizontally polarized optical beam combiner, 23. Vertically polarized optical beam combiner, 24. Horizontally polarized coherent light, 25. Vertically polarized coherent light, 26. Polarization switch, 27. Photodetector, 28. Signal acquisition and processing unit, 29. Control unit, 30. Optical switch control unit, 31. Measuring arm length is L The maximum value of the white light interference fringe envelope corresponding to 32. The measuring arm length is L+ΔL 33. Spectrum of a broadband light source, 34. Spectrum of a narrowband rejection filter. DETAILED DESCRIPTION

[0018] The present invention aims to provide a beam attenuation coefficient 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.

[0019] The measurement principle of the beam attenuation coefficient based on white light interference of the present invention is as follows: Figure 1 shown.

[0020] The output light of the wide spectrum light source (1) passes through a color filter (2) to obtain an initial signal light (3), which is then split into two paths by an optical beam splitter (4), one path being an initial reference light (5) and the other being an initial measurement light (6).

[0021] The measuring light path is composed of a measuring light emitting lens (12) and a measuring light receiving lens (13) on the same optical axis. The initial measuring light (6) is collimated into a parallel measuring light beam by the measuring light emitting lens (12) and then irradiated into the measured medium. The output of the measuring light receiving lens (13) is the transmitted light (14) of the measured medium. The distance between the measuring light emitting lens (12) and the measuring light receiving lens (13) is the measuring arm length (15).

[0022] The length-adjustable reference light path is composed of a reference light emitting lens (7) and a reference light receiving lens (8) on the same optical axis; the reference light emitting lens (7) collimates the initial reference light (5) into a parallel light beam, which is then received by the reference light receiving lens (8), and the reference light receiving lens outputs the reference light (9); the distance between the reference light emitting lens (7) and the reference light receiving lens (8) is the reference arm length (11); the reference arm length adjustment unit (10) is used to adjust the reference arm length (11); the lower limit of the reference arm length (11) is less than the measuring arm length (15), and the upper limit of the reference arm length (11) is greater than the measuring arm length (15).

[0023] The transmitted light (14) of the measured medium is split into horizontally polarized measuring light (20) and vertically polarized measuring light (21) after passing through a measuring light polarization beam splitter (19); the reference light (9) is split into horizontally polarized reference light (17) and vertically polarized reference light (18) after passing through a reference light polarization beam splitter (16).

[0024] The horizontally polarized measurement light (20) and the horizontally polarized reference light (17) are input into a horizontally polarized optical beam combiner (22) to obtain horizontally polarized coherent light (24); the vertically polarized measurement light (21) and the vertically polarized reference light (18) are input into a vertically polarized optical beam combiner (23) to obtain vertically polarized coherent light (25). The horizontally polarized coherent light (24) and the vertically polarized coherent light (25) are input into a polarization switch (26).

[0025] The photodetector (27) converts the optical signal output by the polarization light switch (26) into a corresponding electrical signal; the signal acquisition and processing unit (28) acquires and processes the electrical signal; the control unit (29) is responsible for controlling the entire measurement, and adjusts the reference arm length (11) through the reference arm length adjustment unit (10); and the polarization light switch (26) is controlled by the optical switch control unit (30) to select the output of horizontally polarized coherent light (24) or vertically polarized coherent light (25).

[0026] The white light interference fringe pattern of the present invention is as follows Figure 2 shown.

[0027] The measuring light emitting lens (12) and the measuring light receiving lens (13) are fixed, and the corresponding measuring arm length (15) is equal to LAccording to the measurement process of white light interferometry, the reference arm length (11) is adjusted from the lower limit to the upper limit, and the corresponding interference fringes can be measured; the maximum value (31) of the interference fringes envelope is proportional to the light flux after passing through the medium, so the formula (2) can be obtained. F 1 .

[0028] Changing the position of the measuring light receiving lens (13) corresponds to a measuring arm length (15) equal to L +Δ L According to the measurement process of white light interferometry, the reference arm length (11) is adjusted from the lower limit to the upper limit, and the corresponding interference fringes and the corresponding interference fringes envelope maximum value (32) are measured, so that the formula (3) can be obtained. F 2 .

[0029] According to formula 4, the beam attenuation coefficient of the medium can be calculated m .

[0030] The polarization switch (26) is controlled to select the output of the horizontally polarized coherent light (24) or the vertically polarized coherent light (25). According to the measurement process of formula 4, the attenuation coefficient of the horizontally polarized or vertically polarized light beam of the measured medium can be obtained.

[0031] The spectral characteristics of the wide spectrum light source and narrow band rejection filter of the present invention are shown in FIG. Figure 3 shown.

[0032] The comprehensive spectral characteristics of the wide-spectrum light source (1) and the color filter (2) are (33), and the spectral characteristics of the narrow-band stop filter are (34).

[0033] Measure the attenuation coefficient of the measured medium corresponding to the wide spectrum light source (1) m Then, a narrow-band rejection filter is added to the color filter. According to the measurement process of formula 4, the beam attenuation coefficient of the measured medium is obtained again. m ; Subtracting the two beam attenuation coefficients can obtain the beam attenuation coefficient of the measured medium corresponding to the spectrum of the narrow-band rejection filter. m .

[0034] 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 beam attenuation coefficient measurement technology 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, and an optical switch control unit. The output light of the broad 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 measuring light path is composed of a measuring light emitting lens and a measuring light receiving lens on the same optical axis; the measuring light emitting lens collimates the initial measuring light into a parallel beam, which is then irradiated into the measured medium; the output of the measuring light receiving lens is the transmitted light of the measured medium; the distance between the measuring light emitting lens and the measuring light receiving lens is the measuring arm length; The length-adjustable reference light path is composed of a reference light emitting lens and a reference light receiving lens on the same optical axis; the reference light emitting lens collimates the initial reference light into a parallel beam, which is then received by the reference light receiving lens, and the reference light receiving lens outputs the reference light; 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 is smaller than the measuring arm length, and the upper limit of the reference arm length is larger than the measuring arm length; The transmitted light of the measured medium passes through the measuring light polarization beam splitter and is split into horizontally polarized measuring light and vertically polarized measuring light; the reference light passes through the reference light polarization beam splitter and 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 horizontally polarized optical beam combiner to obtain horizontally polarized coherent light; the vertically polarized measurement light and the vertically polarized reference light are input into the vertically polarized 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 by controlling the reference arm length adjustment unit, and selecting to output horizontally polarized coherent light or vertically polarized coherent light by controlling the polarization switch; Fixed measuring light emitting lens and measuring light receiving lens, corresponding to the measuring arm length L According to the measurement process of white light interferometry, the reference arm length is adjusted from the lower limit to the upper limit to measure the corresponding interference fringes. The maximum value of the interference fringe envelope is proportional to the luminous flux after passing through the medium. According to the Lambert-Beer law, it can be obtained: Φ 1 = Φ 0 × e -μL ； (1) in, Φ 0 is the initial luminous flux, Φ 1 is the luminous flux after passing through the medium, L is the medium length, μ is the beam attenuation coefficient of the medium, also known as the linear attenuation coefficient; change the position of the measuring light receiving lens to determine the new measuring arm length L +Δ L 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 are measured. From the maximum value of the interference fringe envelope, according to the Lambert-Beer law, we can obtain: Φ 2 = Φ 0 × e -μ(L+ΔL) ， (2) According to equations (1) and (2), the beam attenuation coefficient of the measured medium can be calculated: μ : μ = ln( Φ 1 / Φ 2 ) / D L (3)。 2. The light beam attenuation coefficient measurement technology based on white light interferometry described in claim 1 is 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 measurement process of formula 3, the horizontally polarized or vertically polarized light beam attenuation coefficient of the measured medium can be obtained.

3. The light beam attenuation coefficient measurement technology based on white light interferometry described in claim 1 is characterized in that after measuring the light beam attenuation coefficient of the measured medium corresponding to the wide-spectrum light source, a narrow-band rejection filter is added to the color filter, and the light beam attenuation coefficient of the measured medium is measured again according to the measurement process of Formula 3; by subtracting the two light beam attenuation coefficients, the light beam attenuation coefficient of the measured medium corresponding to the spectrum of the narrow-band rejection filter can be obtained.

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