CN110772217A - A method for improving the signal-to-noise ratio of a Brillouin elastography system with an interferometric optical path - Google Patents

Abstract

The invention provides a method for improving the signal-to-noise ratio of a Brillouin elastic imaging system by an interference-type optical path. The method adopts a frequency-sweeping F-P interferometer and a photon receiver to form a spectrometer system, and a computer generates a driver program to control the frequency-sweeping type. The synchronous operation of the F‑P interferometer and the photon receiver enables high-precision scanning and acquisition of the Brillouin scattering signal excited by the 532nm laser in biological tissues. The combination of the two can greatly improve the elasticity of Brillouin scattering. Signal-to-noise ratio for spectral information extraction in imaging systems. The advantages of the present invention are: the principle of interference cancellation of the reference optical path in the Michelson interferometer is adopted, the background noise is suppressed by the destructive interference of the elastic component in the scattered light, and the swept frequency F-P interferometer and the photon receiver are combined at the same time. The spectrometer system is formed, which improves the signal-to-noise ratio of the Brillouin scattering system, improves the detection spectral resolution, and increases the practical applicability of the Brillouin scattering spectral elastography technology.

Description

A method for improving the signal-to-noise ratio of a Brillouin elastography system with an interferometric optical path

technical field

The invention relates to a method for improving the signal-to-noise ratio of a Brillouin elasticity imaging system, in particular to a method for improving the signal-to-noise ratio of a Brillouin elasticity imaging system by an interference type optical path.

Background technique

Brillouin scattering elastography to detect the bulk elastic modulus of ophthalmic biological tissues has broad application prospects in the diagnosis, treatment and prevention of ophthalmic clinical diseases (myopia, keratoconus, etc.), but there are still some technical limitations, mainly Because the spectral resolution of the detection system is low, the Brillouin frequency shift signal cannot be extracted with high precision from the strong background noise of specular reflection and Rayleigh scattering; in addition, most of the existing Brillouin scattering imaging technologies use virtual phase Controlled array spectrometer (VIPA) is used to detect Brillouin scattering frequency-shifted signals, but its detection accuracy and scanning time need to be improved, and there are certain limitations in clinical application.

Since the spectral frequency shift signal of Brillouin scattering represents the acousto-optic effect at the molecular level, and different biomechanical properties have different effects on the frequency shift signal of Brillouin scattering, Brillouin scattering spectral imaging technology is used to detect biological The elastic properties of tissue have higher resolution, but the mainstream technical means is to use virtual phased array spectrometer (VIPA) to scan and detect Brillouin scattering spectral signals. The spectral resolution and detection time of this method need to be improved. , Brillouin scattering signals cannot be detected with high precision for biological tissues that are prone to complex components of strong specular reflection and Rayleigh scattering.

SUMMARY OF THE INVENTION

The purpose of the present invention is to provide a method for improving the signal-to-noise ratio of a Brillouin elastography system with an interference-type optical path, which mainly suppresses the elastic scattering of specular reflection and Rayleigh scattering by cancelling interference of a reference beam in a Michelson interferometer. Then, a spectrometer composed of a swept-frequency F-P interferometer and a photon receiver is used to collect and process the Brillouin scattering spectrum of the sample to obtain a spectral detection result with a high signal-to-noise ratio. The physical relationship between the bulk elastic moduli of the samples is calculated to obtain the bulk elastic moduli of the sample to be tested.

The invention adopts the canceling interference of the reference beam in the Michelson interferometer to suppress the elastic scattering noise of specular reflection and Rayleigh scattering, and then uses the swept frequency F-P interferometer to scan the Brillouin scattering spectrum, and then uses the photon receiver to scan the Brillouin scattering spectrum. The high-precision acquisition and processing of spectral signals is realized, and the frequency shift signal of Brillouin scattering spectrum is obtained by processing on the computer, and then the bulk elastic modulus of the sample to be tested can be calculated. , treatment and prevention have important reference value and broad application prospects.

The interference of light in the Michelson interferometer is based on the principle of coherent superposition of electromagnetic fields, which stipulates that the total amplitude E(r, t) of two beams of equal frequency ω at a point r in space is equal to the vector sum _of the relevant amplitudes E1 and _E2 , therefore

where _φ1 and φ2 are the phases of the _two beams. Therefore, the time-averaged electrical energy density or intensity at point r is expressed as:

The phase difference Δφ=φ ₂ -φ ₁ can be expressed as the optical path difference Δz of the two beams of light as

λ represents the wavelength of light. When the axial amplitudes of the two beams are equal, the total intensity detected is

m是一个整数。Assuming that the two beams of light are coherent in time and space, the above equation means that destructive interference occurs at

m is an integer.

The experimental detection device using this method includes a power-adjustable 532nm CW laser, a 50:50 beam splitter, a mirror 1, a focusing objective lens, a three-dimensional moving lift table, an optical compensator, a mirror 2, piezoelectric ceramics, a convex lens 1, a pinhole Filter, convex lens 2, aperture diaphragm, convex lens 3, swept frequency F-P interferometer, convex lens 4, single-mode fiber, photon receiver, computer.

The specific process of the above imaging method is that a power-adjustable continuous laser emits a laser beam with a wavelength of 532 nm, and after passing through a 50:50 beam splitter, it is divided into two beams that are perpendicular to each other and have a power ratio of 1:1. After the sample light is emitted by the mirror, it is focused by the focusing objective lens and incident on the sample to be tested on the three-dimensional displacement platform, and the Brillouin scattering spectrum is excited, and then focused by the focusing objective lens and then propagated along the original optical path to the 50:50 beam splitter; The reference light is incident on the second mirror after passing through the compensator. The mirror is controlled by piezoelectric ceramics to move axially. The reflected light returns to the beam splitter along the original optical path and interferes with the sample light. The second mirror controlled by piezoelectric ceramics moves axially to modulate the phase of the reference light, and the compensator modulates the amplitude of the reference light to suppress elastically scattered light (specular scattering and Rayleigh scattering) in the interference spectrum. Sexual inhibition.

In the present invention, the piezoelectric ceramic (08) is used to drive the reflector (07) to complete the phase modulation of the reference light, so as to match the phases of specular reflection and Rayleigh scattering in the sample light.

In the present invention, a compensator is used to modulate the amplitude of the reference light, so as to match the amplitude of the elastic scattering light in the sample light, so as to destructively interfere with the elastic scattering noise of specular reflection and Rayleigh scattering in the sample light and the reference light. .

Further, a power-tunable CW laser 01 with an output wavelength of 532 nm is used to generate Brillouin scattering signals, and a swept-frequency F-P interferometer and a photon receiver together form a spectrometer system.

Working principle: The interference light is focused by the convex lens to the vacuum filter to filter out the stray light, the outgoing light is incident at the focus of the convex lens 1, and becomes parallel light after passing through the convex lens 1, and is spatially filtered through the aperture diaphragm to improve the signal-to-noise ratio. Then, it is focused and incident into the swept-frequency F-P interferometer placed at the second focal point of the convex lens. The swept-frequency F-P interferometer is controlled by a computer to generate a driver to scan the optical signal. Its free spectral range is 10GHz, and the spectrum The resolution is 67MHz. The outgoing light of the F-P interferometer is incident at the focal point of the convex lens 3 and focused on the single-mode fiber by the convex lens 3, and then transmitted into the signal receiving end of the photon receiver. Receive the light signal, complete the acquisition and processing of the Brillouin scattering signal after background suppression, and then complete the corresponding spectral data processing and Brillouin frequency shift calculation in the computer.

The advantages of the present invention lie in that a spectrometer system is formed by using a swept-frequency F-P interferometer and a photon receiver, which improves the spectral resolution of the Brillouin scattering system, improves the detection speed, reduces the overall detection time, and increases the Brillouin scattering rate. Clinical operability of scattering spectral elastography techniques.

Description of drawings

FIG. 1 is a schematic diagram of the present invention.

As shown in Figure 1: Power-adjustable 532nm CW laser (01), 50:50 beam splitter (02), 532nm mirror one (03), focusing objective lens (04), three-dimensional mobile lift table (05), optical compensator ( 06), mirror two (07), piezoelectric ceramics (08), convex lens one (09), pinhole filter (10), convex lens two (11), aperture diaphragm (12), convex lens three (13) , swept frequency F-P interferometer (14), convex lens four (15), single-mode optical fiber (16), photon receiver (17), computer (18).

Detailed ways

A method for improving the signal-to-noise ratio of a Brillouin elastography system by an interference-type optical path, the specific implementation is that a power-adjustable 532nm continuous laser 01 emits a laser beam with a wavelength of 532nm, which is divided into two by a 50:50 beam splitter 02. Two beams of light which are perpendicular to each other and have a power ratio of 1:1, wherein the sample light is emitted by the reflector 1 (03) and then focused by the focusing objective lens (04) to the sample to be tested on the three-dimensional displacement platform (05), and excites the sample to be tested. The Brillouin scattering spectrum is then focused by the focusing objective lens (04) and then propagated along the original optical path to the 50:50 beam splitter (02). The reflector is controlled by the piezoelectric ceramic (08) to move axially, the reflected light returns to the beam splitter (02) along the original optical path, and interferes with the sample light, and the entire reference optical path is used to adjust the various parts of the system signal receiving optical path Coaxiality of optical components. The second mirror (07) controlled by the piezoelectric ceramic (08) moves axially to modulate the phase of the reference light, and the compensator (06) modulates the amplitude of the reference light, so as to realize the elastic scattering light in the interference spectrum ( destructive suppression of specular and Rayleigh scattering).

The interference light is focused by the convex lens (09) to the vacuum filter (10) to filter out the stray light, the outgoing light is incident at the focal point of the convex lens (11), becomes parallel light after passing through the convex lens (11), and passes through the aperture diaphragm (12) performing spatial filtering to improve the signal-to-noise ratio, and then focusing and incident through the second convex lens (13) into the swept-frequency F-P interferometer (14) placed at the focus of the second convex lens (13), and the swept-frequency F-P interferometer (14) ) is controlled by the computer (18) to generate a driver program to scan the optical signal, the outgoing light is incident at the focal point of the convex lens three (15) and is focused to the single-mode fiber (16) by the convex lens three (15), and then transmitted into the single-mode fiber (16). The signal receiving end of the photon receiver (17), the photon receiver (17) is controlled by the computer (18) to generate a driver program of matching sweep frequency F-P to receive the optical signal, and complete the acquisition and processing of the Brillouin scattering signal after background suppression , and then the corresponding spectral frequency shift results can be obtained on the computer (18).

The invention relates to a method for improving the signal-to-noise ratio of a Brillouin elastic imaging system by an interference-type optical path, which is characterized in that specular reflection and Rayleigh scattering in the Brillouin system are suppressed based on the cancelling interference of a reference beam in a Michelson interferometer. The elastic scattered light can reduce the background noise of the Brillouin spectrum, thereby improving the overall signal-to-noise ratio of the Brillouin elastography system.

The invention relates to a method for improving the signal-to-noise ratio of a Brillouin elastic imaging system by an interference type optical path. Scanning detection of the Brillouin scattering frequency shift signal of the sample, and then obtaining the bulk elastic modulus of the sample.

The invention relates to a method for improving the signal-to-noise ratio of a Brillouin elastic imaging system by an interference-type optical path, which is characterized in that a power-adjustable 532nm continuous laser 01, a 50:50 beam splitter 02, a 532nm reflecting mirror 03, and a focusing objective lens 04 are used , 3D mobile lifting platform 05, optical compensator 06, mirror two 07, piezoelectric ceramics 08, convex lens one 09, pinhole filter 10, convex lens two 11, pinhole aperture 12, convex lens three 13, frequency sweep F-P interference Instrument 14, convex lens four 15, single-mode optical fiber 16, photon receiver 17, computer 18 experimental device.

The invention relates to a method for improving the signal-to-noise ratio of a Brillouin elastic imaging system by an interference type optical path. The photon receivers together form a spectrometer system to achieve high-precision scanning detection of Brillouin scattering frequency-shifted signals.

Not limited to this, any changes or substitutions that are not thought of through creative work should be covered within the protection scope of the present invention. Therefore, the protection scope of the present invention should be based on the protection scope defined by the claims.

Claims (3)

1. a method for improving the signal-to-noise ratio of Brillouin elastography system by an interference type optical path, it is characterized in that, the concrete process of this interference type Brillouin scattering elastography is: the power-adjustable continuous laser (01) emits a wavelength of The 532nm laser beam, after passing through the 50:50 beam splitter (02), is divided into two beams that are perpendicular to each other and have a power ratio of 1:1. The sample light is emitted by mirror one (03) and then focused. The objective lens (04) focuses the sample to be tested incident on the three-dimensional displacement platform (05) to excite the Brillouin scattering spectrum, which is then focused by the focusing objective lens (04) and then propagates along the original optical path to the 50:50 beam splitter (02) The reference light is incident on the second mirror (07) after passing through the optical compensator (06). The mirror is controlled by the piezoelectric ceramic (08) to move axially, and the reflected light returns to the beam splitter (08) along the original optical path. 02), it interferes with the sample light, and the mirror two (07) controlled by the piezoelectric ceramics (08) moves axially to modulate the phase of the reference light, and the optical compensator (06) adjusts the amplitude of the reference light. Modulation to achieve the destructive suppression of the elastically scattered light in the interference spectrum, that is, specular scattering and Rayleigh scattering, the interference light is focused by the convex lens (09) to the vacuum filter (10) to filter out the stray light, and the outgoing light is in the convex lens one (11). ) is incident at the focal point of the 1st convex lens (11) and becomes parallel light after passing through the first aperture diaphragm (12) for spatial filtering to improve the signal-to-noise ratio. 13) In the swept-frequency F-P interferometer (14) at the focal point, the swept-frequency F-P interferometer (14) is controlled by the computer (18) to generate a driver program for scanning the optical signal, and the outgoing light is in the convex lens three (15) The light is incident at the focal point and is focused to the single-mode fiber (16) by the convex lens three (15), and then transmitted into the signal receiving end of the photon receiver (17), and the photon receiver (17) is controlled by the computer (18) to generate a matching frequency sweep The driver program of the F-P is used to receive the light signal, complete the acquisition and processing of the Brillouin scattering signal after background suppression, and then the corresponding spectral frequency shift result can be obtained by calculation on the computer (18). 2. The method for improving the signal-to-noise ratio of a Brillouin elastography system by an interferometric optical path as claimed in claim 1, wherein the experimental detection device for implementing the method comprises a power-adjustable 532nm continuous laser (01), a 50 : 50 beam splitter (02), 532nm mirror one (03), focusing objective lens (04), 3D mobile lift table (05), optical compensator (06), mirror two (07), piezoelectric ceramics (08) , convex lens one (09), pinhole filter (10), convex lens two (11), aperture diaphragm (12), convex lens three (13), swept frequency F-P interferometer (14), convex lens four (15), Single mode fiber (16), photon receiver (17), computer (18). 3. The method for improving the signal-to-noise ratio of a Brillouin elastography system by an interference-type optical path as claimed in claim 1, characterized in that: a swept-frequency F-P interferometer (14) is used to scan and receive Brillouin scattering signals , the spectral resolution of the swept-frequency F-P interferometer (14) is 67MHz, the free spectral range is 10GHz, the photon receiver (17) is used to collect and process the Brillouin scattering signal, and the computer (18) completes the Brillouin scattering frequency shift calculation.