CN206063128U - A kind of compound speckle noise reduction system of angle of full tunnel modulating-coding - Google Patents

Abstract

The utility model discloses an angle composite speckle noise reduction system with full-channel modulation and encoding, which comprises a low-coherence broadband light source, a circulator, an optical fiber coupler, a reference arm, a sample arm, a spectrometer and a processing unit module; wherein: the reference arm consists of The first polarization controller, the first collimating lens, focusing lens and plane mirror; the sample arm is composed of the second polarization controller, the second collimating lens, the orthogonal scanning device and the objective lens; the spectrometer is composed of the third collimating lens , diffraction grating, Fourier lens and high-speed line array camera; the composite sample structure image obtained by using the utility model with multiple spatial angles has reduced speckle noise, improved image quality, and more detailed information in the structure diagram. clear.

Description

An Angular Composite Speckle Noise Reduction System Based on Full-Channel Modulation and Coding

technical field

The utility model relates to an optical coherence tomography (Optical Coherence Tomography, OCT), in particular to an angle composite speckle noise reduction system with full-channel modulation and coding.

Background technique

OCT technology is an imaging technology widely used in the biomedical field to detect the microstructure of biological tissues, with the advantages of non-invasiveness, high speed and high resolution. OCT technology uses the detected light intensity changes of backscattered light from biological samples to obtain reflection information inside the sample and reconstruct the tomographic structure image of the sample. Due to low coherence interferometric detection, OCT imaging suffers from speckle noise. Speckle noise arises from the effect of the coherent addition of columns of light waves with random phase distribution. The existence of speckle noise will lead to the degradation of the quality of the obtained image, the reduction of the signal-to-noise ratio, and the blurring of the image details that can reflect the structural characteristics of the sample. Therefore, it is necessary to take effective methods to reduce speckle noise and improve image signal-to-noise ratio in OCT imaging.

Speckle noise reduction can be achieved by compound averaging multiple independent OCT images with uncorrelated speckle noise patterns. Based on this concept, four main approaches such as frequency diversity, polarization diversity, spatial diversity and angle diversity have emerged. Multiple sub-images with independent speckle patterns coded by different incident angles of the probe beam are acquired and compounded and averaged to achieve speckle noise reduction based on angle compounding. Iftimia et al. proposed an OCT speckle reduction method based on optical path encoding angle compounding. In this method, a small piece of optical glass is placed in the detection beam path of the sample arm to realize the optical path encoding of different incident angles of the detection beam. However, in order to obtain multiple angle-resolved OCT sub-images to improve the degree of speckle noise reduction in this method, a longer imaging range is required, which is difficult to achieve in the usual spectral domain OCT system. Later, Wang et al. proposed an easy-to-implement method for suppressing speckle noise based on angle compounding of B-scan Doppler frequency shift coding. This method changes the geometric setting of the sample arm in the traditional spectral domain OCT, so that the entire detection beam is shifted to one side of the center of the rotation axis of the scanning mirror, thereby introducing a positive or negative modulation frequency to make the conjugate term of the transverse B-scan modulation spectrum differentiate. By dividing the transverse scanning modulation spectrum, sub-spectra of different frequencies are obtained, and the encoding of different incident angles of the detection beam is realized. However, due to the special beam setting of the sample arm in this method, only a narrow modulation spectrum of half-channel (only positive or negative frequency components) is used to realize angle encoding in the spatial frequency domain, which limits the range of modulation spectrum segmentation. number to meet the appropriate reduced lateral resolution due to segmentation. In addition, in order to obtain the Doppler frequency shift and completely distinguish the conjugate overlapping transverse modulation spectrum, it is necessary to ensure a sufficiently high transverse sampling rate in one B-scan, which limits the imaging speed of the system.

Contents of the invention

Aiming at the deficiencies of the prior art, the utility model proposes an angle composite speckle noise reduction system with full-channel modulation and coding

An angle compound speckle noise reduction system with full-channel modulation and encoding, including a low-coherence broadband light source, a circulator, a fiber coupler, a reference arm, a sample arm, a spectrometer, and a processing unit module; wherein: the reference arm is controlled by a first polarization controller , a first collimator lens, a focusing lens and a plane mirror; the sample arm is made up of a second polarization controller, a second collimator lens, an orthogonal scanning device and an objective lens; the spectrometer is made up of a third collimator lens, a diffraction grating, a Fourier Composed of Liye lens and high-speed line scan camera;

The low-coherence broadband light source of the system enters the light from the first input port on one side of the fiber coupler after passing through the circulator; the first output port on the other side of the fiber coupler is connected to the first polarization controller of the reference arm, The first polarization controller is connected with the first collimator lens of the reference arm; the focus lens of the reference arm is on the same optical path as the first collimator lens of the reference arm, and the back focal plane of the plane reflector coincides with the focus lens; the fiber coupler The second output port on the other side is connected with the second polarization controller of the sample arm, and the second polarization controller is connected with the second collimator lens of the sample arm; the exit light path optical axis of the second collimator lens Through the center of the rotation axis of the first scanning mirror, the center of the rotation axis of the second scanning mirror and the center of the objective lens in the orthogonal scanning device in sequence, the sample to be measured is placed at the rear focal plane of the objective lens; the other output port of the circulator is connected with the third alignment of the spectrometer The straight lens is connected, and on the exit light path of the third collimator lens, a diffraction grating is placed according to the principle of grating diffraction, the Fourier lens is placed on the exit light path of the grating, and the pixel surface of the high-speed line scan camera is placed on the Fourier lens At the rear focal plane of the line scan camera; the processing unit module is connected behind the line scan camera;

The light emitted by the low-coherence broadband light source of the system enters the fiber coupler after passing through the circulator. A beam of light enters the sample arm, and after being collimated, scanned and focused, it irradiates the sample to be measured; the orthogonal scanning device in the sample arm realizes the three-dimensional imaging scanning of the sample to be measured; the light reflected by the plane mirror in the reference arm The light and the backscattered light of the sample in the sample arm interfere at the fiber coupler. The interference beam output by the fiber coupler passes through the spectrometer and is collected and processed by the processing unit module. The central wavelength of the low-coherence broadband light source is 1325nm, half The high full width is 100nm.

Compared with background technology, the beneficial effect that the utility model has is:

The composite sample structure image obtained by using the utility model has reduced speckle noise, improved image quality, and clearer detail information in the structure image.

Description of drawings

Figure 1 is a schematic diagram of the sample arm detection beam scanning in the OCT system;

Fig. 2 is a schematic diagram of the imaging system of the present invention.

detailed description

Below in conjunction with accompanying drawing and embodiment example the utility model is described further.

Fig. 1 is a schematic diagram of scanning of the detection beam of the sample arm in the OCT system. The schematic diagram of Fig. 1 will be described in detail below.

In the sample arm of the OCT system, the effective diameter of the probe beam (ie, label ①) irradiated on the collimating objective lens (ie, label ④) should be as large as possible to obtain a higher system imaging lateral resolution. When the collimated beam irradiates the center of the rotation axis of the scanning mirror on the sample arm (ie, label ②), the positions of different widths of the beam from the center of the rotation axis (ie, label ③) correspond to the offset ±δ. The offset will introduce the modulation frequency f _m , so that the transverse scanning spectrum in the spatial frequency domain is modulated. The modulation frequency f _m is linearly proportional to the offset δ, namely:

f _m =2kδω/π,

Where: ω is the rotational angular velocity of the scanning mirror. It can be seen from the geometry of the optical path of the sample arm that different offsets correspond to different incident angles θ of the probe beam. Therefore, in the transverse scanning modulation spectrum of all channels, different modulation frequencies can encode different incident angles of the probe beam, and k represents the wave number.

As shown in FIG. 2 , an angular composite speckle noise reduction system with full-channel modulation and coding includes a low-coherence broadband light source 1, a circulator 2, a fiber coupler 3, a reference arm, a sample arm, a spectrometer, and a processing unit module 17; Wherein: the reference arm is composed of the first polarization controller 4, the first collimating lens 5, the focusing lens 6 and the plane mirror 7; the sample arm is composed of the second polarization controller 8, the second collimating lens 9, and an orthogonal scanning device 10 and objective lens 11 are made up; Spectrograph is made up of the 3rd collimating lens 13, diffraction grating 14, Fourier lens 15 and high-speed line scan camera 16;

After the low-coherence broadband light source 1 of the system passes through the circulator 2, one output port of the circulator 2 is connected to the first input port on one side of the fiber coupler 3; the first output port on the other side of the fiber coupler 3 is connected to the reference The first polarization controller 4 of the arm is connected, and the first polarization controller 4 is connected with the first collimator lens 5 of the reference arm; the focusing lens 6 of the reference arm is on the same optical path as the first collimator lens 5 of the reference arm, The plane mirror 7 coincides with the back focal plane of the focusing lens 6; the second output port on the other side of the fiber coupler 3 is connected to the second polarization controller 8 of the sample arm, and the second polarization controller 8 is connected to the sample The second collimating lens 9 of the arm is connected; the exit light path optical axis of the second collimating lens 9 passes through the center of the first scanning mirror rotation axis in the orthogonal scanning device 10, the second scanning mirror rotation axis center and the center of the objective lens 11 successively, The sample 12 to be measured is placed at the rear focal plane of the objective lens 11; another output port of the circulator 2 is connected with the third collimating lens 13 of the spectrometer, and on the outgoing light path of the third collimating lens 13, according to the grating diffraction principle Diffraction grating 14 is placed, Fourier lens 15 is placed on the outgoing light path of the grating, and the pixel surface of high-speed line array camera 16 is placed at the rear focal plane of Fourier lens 15; Line array camera 16 is followed by processing unit module 17 , the central wavelength of the laser light source is 1325nm, and the full width at half maximum is 100nm.

The light emitted by the low-coherence broadband light source 1 of the system enters the fiber coupler 3 after passing through the circulator 2. The emitted light of the fiber coupler 3 is divided into two beams: one beam enters the reference arm, and after being collimated and focused, it irradiates the plane Reflector 7; another beam of light enters the sample arm, and is irradiated on the tested sample 12 after being collimated, scanned and focused; the orthogonal scanning device 10 in the sample arm realizes the three-dimensional imaging scanning of the tested sample 12; by reference The light reflected back by the plane reflector 7 in the arm interferes with the backscattered light of the measured sample 12 in the sample arm at the optical fiber coupler 3, and the interference beam output by the optical fiber coupler 3 passes through the spectrometer (13-16). The processing unit module 17 collects and processes.

Claims (1)

1. An angle compound speckle noise reduction system with full-channel modulation and encoding, including a low-coherence broadband light source, a circulator, a fiber coupler, a reference arm, a sample arm, a spectrometer, and a processing unit module; wherein: the reference arm consists of a first polarization The controller, the first collimating lens, the focusing lens and the plane reflector; the sample arm is composed of the second polarization controller, the second collimating lens, the orthogonal scanning device and the objective lens; the spectrometer is composed of the third collimating lens, the diffraction grating , Fourier lens and high-speed line-scan camera; It is characterized in that: the low-coherence broadband light source of the system enters the light from the first input end on one side of the fiber coupler after passing through the circulator; the first output end on the other side of the fiber coupler and the first polarization control of the reference arm The device is connected, the first polarization controller is connected with the first collimating lens of the reference arm; the focusing lens of the reference arm is on the same optical path as the first collimating lens of the reference arm, and the back focal plane of the plane reflector coincides with the focusing lens; The second output port on the other side of the fiber coupler is connected with the second polarization controller of the sample arm, and the second polarization controller is connected with the second collimator lens of the sample arm; the outlet of the second collimator lens The optical axis of the beam path passes through the center of the rotation axis of the first scanning mirror, the center of the rotation axis of the second scanning mirror and the center of the objective lens in sequence in the orthogonal scanning device, and the sample to be measured is placed at the rear focal plane of the objective lens; the other output port of the circulator is connected with the spectrometer The third collimating lens is connected to the third collimating lens. On the outgoing light path of the third collimating lens, a diffraction grating is placed according to the grating diffraction principle. The Fourier lens is placed on the outgoing light path of the grating, and the pixel surface of the high-speed line scan camera is placed on the At the rear focal plane of the Fourier lens; the processing unit module is connected behind the line array camera, the central wavelength of the low-coherence broadband light source is 1325nm, and the full width at half maximum is 100nm.