CN111528799B - Method for improving dynamic range of sweep frequency light source optical coherence tomography system - Google Patents
Method for improving dynamic range of sweep frequency light source optical coherence tomography system Download PDFInfo
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Abstract
The invention discloses a method for improving the dynamic range of a swept-source optical coherence tomography (SSOCT) system. The method provided by the invention compensates the attenuation signal caused by the transmission of the OCT signal in the biological tissue, thereby compressing the detection range of the OCT, keeping higher contrast ratio of the OCT image in the penetration range and enhancing the depth imaging capability of the OCT system. According to the embodiment of the invention, the characteristic that the depth information in the SSOCT signal is coded by the signal frequency is utilized, and different frequencies of the interference signal are amplified by different gains. The method can effectively improve the dynamic range of the system, increase the contrast ratio, improve the resolution capability of the deep tissue micro structure and is beneficial to the popularization and application of the OCT technology in clinical medical imaging.
Description
Technical Field
The invention relates to the technical field of biomedical optical imaging, in particular to a method for improving the dynamic range of a sweep frequency light source optical coherence tomography system.
Background
The Optical Coherence Tomography (OCT) is a very potential optical imaging means that is rapidly developed in recent years, and based on the ultrashort characteristic of the interference length of broad spectrum light, the OCT can perform coherent detection on backscattered light in a tissue, thereby realizing two-dimensional or three-dimensional tomographic imaging of biological tissues. Compared with the traditional medical imaging means OCT technology, the method has the advantages of no radiation, non-contact and high resolution, and the resolution can reach 5-15 mu m. Therefore, the OCT technology is very suitable for being applied to the medical imaging field, wherein the OCT technology becomes a standard means in the diagnosis and treatment of ophthalmic diseases, and is also widely applied to the endoscopic imaging field of cardiovascular, respiratory tract, digestive tract and the like in combination with an endoscope. The OCT technology is currently developed from time domain OCT (tdoct) based on mechanical scanning to frequency domain OCT (fdoct) based on spectral decoding, and the imaging speed is greatly improved, while the frequency domain OCT can be divided into spectral domain OCT (sdoct) for resolving a spectrum from a probe end and swept-source OCT (sscoct) for resolving a spectrum from a light source end according to a spectral decoding method, wherein the sscoct for realizing frequency scanning with the swept-source OCT can realize higher imaging speed and imaging range, and has a compact structure, so that the OCT can be widely applied.
The optical wave is used as a detection signal carrier, so that the advantages of high resolution, non-contact, no ionizing radiation and the like of the OCT technology are given, but due to absorption and scattering, the light intensity is rapidly reduced along with the depth by an e index when light is transmitted in a biological tissue, the signal intensity is rapidly reduced along with the depth in an imaging range, and therefore the problem of insufficient dynamic range is brought, and in addition, the contrast is also rapidly reduced along with the depth, so that the application and the development of the OCT technology are restricted.
Disclosure of Invention
The embodiment of the invention aims to provide a method for improving the dynamic range of a swept-source optical coherence tomography system, which compensates OCT signals at different depths, makes up the difference of the signals at different depths, and increases the size of the minimum detectable signal, thereby improving the dynamic range, the imaging quality and the contrast of the system.
In order to achieve the above object, an embodiment of the present invention provides a method for increasing a dynamic range of a swept-source optical coherence tomography system, including the following steps:
outputting wide-spectrum light with frequency scanned along with time through a sweep light source, and providing a corresponding trigger signal and a clock signal;
controlling the mechanical scanning of a coherent imaging system according to a trigger signal and a clock signal provided by the sweep frequency light source, receiving an electric signal obtained by the conversion of a subsequent frequency-dependent detection system, and then sending a corresponding feedback signal;
transmitting the wide-spectrum light to the surface of a sample for scanning, receiving back scattering light returned from the sample and reference light, and simultaneously interfering to generate coherent light;
and detecting the coherent light, converting the coherent light into an electric signal, adjusting the gain amplitude of different frequency components according to the frequency of the electric signal, ensuring the signal amplitudes of different depths to be at the same level, analyzing and processing the compensated signal, and simultaneously imaging in real time.
Further, the transmitting the wide spectrum light to the surface of the sample for scanning, and receiving the back scattered light returned from the sample and the reference light to interfere simultaneously to generate coherent light, specifically:
splitting the broad spectrum light by 90:10 coupling to transmit 90% of the light to the sample arm and 10% of the light to the reference arm;
focusing light on the reference arm onto a reflector to obtain reference light;
mechanically scanning the light on the sample arm and focusing the light on a sample to obtain back scattered light;
and carrying out 50:50 coupling coherence on the reference light and the backscattered light to generate coherent light containing sample structure information.
As a preferred embodiment of the present invention, the present invention further provides an apparatus for increasing a dynamic range of a swept-source optical coherence tomography system, including: the device comprises a sweep frequency light source module, a control module, a coherent imaging module and a frequency dependence detection module;
the frequency sweeping light source module is used for outputting wide spectrum light with frequency scanned along with time through a frequency sweeping light source and providing corresponding trigger signals and clock signals;
the control module is used for controlling the mechanical scanning of the coherent imaging system according to the trigger signal and the clock signal provided by the sweep frequency light source, receiving the electric signal converted by the subsequent frequency-dependent detection system and then sending a corresponding feedback signal;
the coherent imaging module is used for transmitting the wide-spectrum light to the surface of a sample for scanning, receiving back scattering light returned from the sample and reference light, and simultaneously interfering to generate coherent light;
the frequency-dependent detection module is used for detecting the coherent light and converting the coherent light into an electric signal, adjusting the gain amplitude of different frequency components according to the frequency of the electric signal, ensuring the signal amplitudes of different depths to be at the same level, analyzing and processing the compensated signal, and simultaneously imaging in real time.
Further, the coherent imaging module comprises a conduction unit, a reference light acquisition unit, a sample light acquisition unit and a processing unit;
the conduction unit is used for conducting 90:10 coupling light splitting on the broad spectrum light so as to conduct 90% of the light to the sample arm and conduct 10% of the light to the reference arm;
the reference light acquisition unit is used for focusing light on the reference arm on a reflector to obtain reference light;
the sample light acquisition unit is used for mechanically scanning the light on the sample arm and focusing the light on the sample to obtain back scattering light;
and the processing unit is used for performing 50:50 coupling coherence on the reference light and the back scattering light to generate coherent light containing sample structure information.
Another embodiment of the present invention further provides an apparatus for improving the dynamic range of a swept-source optical coherence tomography system, including a processor, a memory, and a computer program stored in the memory and configured to be executed by the processor, where the processor executes the computer program to implement the method for improving the dynamic range of a swept-source optical coherence tomography system according to the above-mentioned embodiment of the present invention.
Another embodiment of the present invention further provides a computer-readable storage medium, where the computer-readable storage medium includes a stored computer program, where when the computer program runs, the apparatus on which the computer-readable storage medium is located is controlled to execute the method for improving the dynamic range of the swept-source optical coherence tomography system according to the above embodiment of the present invention.
The embodiment of the invention has the following beneficial effects:
the invention provides a method for improving the dynamic range of a sweep frequency light source optical coherence tomography system, which comprises the steps of outputting wide spectrum light with frequency scanned along with time by a sweep frequency light source, and providing a corresponding trigger signal and a clock signal; controlling the mechanical scanning of a coherent imaging system according to a trigger signal and a clock signal provided by the sweep frequency light source, receiving an electric signal obtained by the conversion of a subsequent frequency-dependent detection system, and then sending a corresponding feedback signal; transmitting the wide-spectrum light to the surface of a sample for scanning, receiving back scattering light returned from the sample and reference light, and simultaneously interfering to generate coherent light; and detecting the coherent light, converting the coherent light into an electric signal, adjusting the gain amplitude of different frequency components according to the frequency of the electric signal, ensuring the signal amplitudes of different depths to be at the same level, analyzing and processing the compensated signal, and simultaneously imaging in real time. By adopting the embodiment provided by the invention, the OCT signals at different depths are compensated, so that the difference of the signals at different depths is compensated, and the minimum detectable signal size is increased, thereby improving the dynamic range, the imaging quality and the contrast of the system.
Drawings
FIG. 1 is a schematic flow chart diagram illustrating one embodiment of a method for improving the dynamic range of a swept-source optical coherence tomography system provided by the present invention;
FIG. 2 is a schematic structural diagram of an embodiment of the apparatus for improving the dynamic range of a swept-source optical coherence tomography system provided by the present invention;
FIG. 3 is a detailed optical path diagram for improving the dynamic range of a swept-source optical coherence tomography system provided by the present invention;
FIG. 4 is a schematic diagram of a frequency dependent detection circuit according to the present invention;
FIG. 5 is a schematic diagram of another configuration of the frequency dependent detection circuit provided by the present invention;
FIG. 6 is a comparison of uncompensated sample OCT signal light provided by the present invention and the gain curve of the frequency dependent detection circuit in the ideal case;
figure 7 is a graph of compensated OCT signal amplitude provided by the present invention;
FIG. 8 is a schematic diagram of a high-pass filter circuit-based frequency-dependent detection circuit according to the present invention;
fig. 9 is another schematic diagram of a frequency-dependent detection circuit according to the present invention.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
Example 1:
referring to fig. 1, fig. 1 is a flowchart illustrating a method for increasing a dynamic range of a swept-source optical coherence tomography system according to an embodiment of the present invention. As shown in fig. 1, the method includes steps S1 to S4, which are as follows:
s1, outputting wide spectrum light with frequency scanned along with time by a sweep light source, and providing corresponding trigger signals and clock signals;
s2, controlling the mechanical scanning of the coherent imaging system according to the trigger signal and the clock signal provided by the sweep frequency light source, receiving the electric signal converted by the subsequent frequency-dependent detection system, and then sending a corresponding feedback signal;
s3, transmitting the wide spectrum light to the surface of a sample for scanning, and receiving back scattering light returned from the sample and reference light to generate coherent light by interference;
in this embodiment of the present invention, the step S3 specifically includes: splitting the broad spectrum light by 90:10 coupling to transmit 90% of the light to the sample arm and 10% of the light to the reference arm; focusing light on the reference arm onto a reflector to obtain reference light; mechanically scanning the light on the sample arm and focusing the light on a sample to obtain back scattered light; and carrying out 50:50 coupling coherence on the reference light and the backscattered light to generate coherent light containing sample structure information.
And S4, detecting the coherent light and converting the coherent light into an electric signal, adjusting the gain amplitude of different frequency components according to the frequency of the electric signal, ensuring the signal amplitudes of different depths to be at the same level, analyzing and processing the compensated signal, and simultaneously imaging in real time.
It should be noted that, after the coherent signal is detected and converted into an electrical signal, the attenuation conditions of signals with different frequencies in the sample are calculated, and a feedback signal is provided according to the signal attenuation trend, so as to adjust the gain conditions of different frequency components, thereby ensuring that the signal amplitudes at different depths in the sample are close to each other, and compressing the signal range.
According to the characteristic that different frequencies of signals in the swept-source OCT system correspond to different depths of a sample, different gains are provided for different frequency components of interference signals. The attenuation conditions of samples with different optical properties on optical signals are not consistent, a specific gain curve can be obtained according to the attenuation condition of signal light in the sample, and an OCT system firstly measures the attenuation curve of the optical signals in tissues in advance under the uncompensated condition and then dynamically adjusts gains with different frequencies according to the attenuation curve. The embodiment provided by the invention can dynamically adjust the signal gain aiming at different samples, and ensure that the signal amplitudes at different depths are at the same level. By the method, the dynamic range of the OCT system can be greatly improved, the contrast at different depths of the OCT image is stored at a higher level, the whole OCT image is clearer, the depth imaging capability of the OCT system is enhanced, the micro structure of deep tissues can be clearly displayed, the situation that the whole OCT image cannot be observed due to low contrast is avoided, the method has great significance for application in clinical medicine, enough tissue information can be provided for doctors, the basis is provided for diagnosis of diseases, and the method is favorable for accurately assisting doctors in detecting the diseases and performing operation.
Example 2:
referring to fig. 2, fig. 2 is a schematic structural diagram of an embodiment of an apparatus for increasing a dynamic range of a swept-source optical coherence tomography system, as shown in fig. 2, the apparatus includes a swept-source module, a control module, a coherent imaging module, and a frequency-dependent detection module;
the frequency sweeping light source module is used for outputting wide spectrum light with frequency scanned along with time through a frequency sweeping light source and providing corresponding trigger signals and clock signals;
the control module is used for controlling the mechanical scanning of the coherent imaging system according to the trigger signal and the clock signal provided by the sweep frequency light source, receiving the electric signal converted by the subsequent frequency-dependent detection system and then sending a corresponding feedback signal;
the coherent imaging module is used for transmitting the wide-spectrum light to the surface of a sample for scanning, receiving back scattering light returned from the sample and reference light, and simultaneously interfering to generate coherent light;
the frequency-dependent detection module is used for detecting the coherent light and converting the coherent light into an electric signal, adjusting the gain amplitude of different frequency components according to the frequency of the electric signal, ensuring the signal amplitudes of different depths to be at the same level, analyzing and processing the compensated signal, and simultaneously imaging in real time.
In an embodiment of the present invention, the coherent imaging module includes a conduction unit, a reference light acquisition unit, a sample light acquisition unit, and a processing unit;
the conduction unit is used for conducting 90:10 coupling light splitting on the broad spectrum light so as to conduct 90% of the light to the sample arm and conduct 10% of the light to the reference arm; the reference light acquisition unit is used for focusing light on the reference arm on a reflector to obtain reference light; the sample light acquisition unit is used for mechanically scanning the light on the sample arm and focusing the light on the sample to obtain back scattering light; and the processing unit is used for performing 50:50 coupling coherence on the reference light and the back scattering light to generate coherent light containing sample structure information.
Example 3:
referring to fig. 3, fig. 3 is a specific optical path diagram for improving the dynamic range of the swept-source optical coherence tomography system provided by the present invention, which includes a computer control system 101, a swept-source 102, a 90:10 fiber coupler 21, a circulator 22, a collimator 23, a lens 24, a mirror 25, a sample 26, a lens 27, a galvanometer scanning system 28, a circulator 29, a 50:50 coupler 30, a balanced photodetector 31, a frequency-dependent detection circuit 32, and a data acquisition card 33.
The specific steps for compensating the signal attenuation along with the depth of the swept-source OCT system are as follows:
the trigger and clock signals are provided by a swept source 102, the swept source 102 emits a broad spectrum of light at a frequency swept over time, which is split by a 90:10 coupler 21, with 90% of the light entering the sample arm and 10% of the light entering the reference arm. The light of the reference arm passes through the 1 port of the circulator 22, is output from the 2 port, is focused on the reflecting mirror 25 through the collimator 23 and the lens 24, enters from the 2 port after reflection, and is output from the 3 port. The light of the sample arm passes through the 1 port of the circulator 29 and is output from the 2 port, the scanning galvanometer 28 performs mechanical scanning, the light is focused on the sample 26 by the lens 27, and the sample light returns in the original path and enters the 2 port of the circulator 29 and is output from the 3 port.
The reference light and the sample light are coherent at a 50:50 coupler 30, the coherent light containing sample structure information is output to an input end of a balanced photoelectric detector 31, converted into an electric signal, collected by a data acquisition card 33 after passing through a frequency-dependent detection circuit 32, transmitted to a computer control system 101, pre-measured under the condition of no compensation to obtain an attenuation curve of the signal light in the sample, and fed back to the frequency-dependent detection circuit to control the gain of the frequency-dependent detection circuit to be adjusted to an ideal state along with a frequency change curve, so that the intensity of the signal reflected back at each depth is ensured to be on the same level, and the computer control system 101 analyzes and processes the compensated signal and performs real-time imaging.
Example 4:
referring to fig. 4, fig. 4 is a schematic structural diagram of a frequency-dependent detection circuit according to the present invention, which is an operational amplifier circuit including resistors 35, 37, and 38, an operational amplifier 34, and a magnetic bead 36, wherein the magnetic bead 36 is an electronic component with high resistivity and magnetic permeability, which is equivalent to a resistor and an inductor connected in series, and both the resistance and the inductance change with frequency, and the magnetic bead exhibits resistance at high frequency. After the OCT signal is converted into a voltage signal by the photodetector, the voltage signal is input to the non-inverting input terminal of the operational amplifier 34, and the output voltage is fed back to the inverting input terminal of the operational amplifier through the resistor 37 and the magnetic bead 36, and the input voltage v can be obtained according to the virtual short and virtual break characteristics of the operational amplifieriAnd an output voltage voThe relationship between: v. ofo＝(1+RFB/R2)viWherein R isFBAs impedance of magnetic bead, R2Is the resistance of resistor 37. Because the beads 36 are resistive to RFBRising with signal frequencyTherefore, the amplification gain of the amplification circuit will increase with frequency, with higher signal frequency and higher gain. The parameters of the magnetic beads 36 can be adjusted according to actual conditions to obtain a required curve of gain variation with frequency, so that the amplitudes of different frequency components in the OCT signal can be maintained at the same level.
Example 5:
referring to fig. 5, fig. 5 is another structural schematic diagram of the frequency-dependent detection circuit according to the present invention, which is an operational amplifier circuit including resistors 40, 42,43, and 44, an operational amplifier 39, and an inductor 41. After the OCT signal is converted into a voltage signal by a photodetector, the voltage signal is input to the non-inverting input terminal of the operational amplifier 39, and the output voltage is fed back to the inverting input terminal of the operational amplifier through the resistors 42 and 43 and the inductor 41, similar to the circuit of embodiment 4, the magnetic bead 36 is replaced by one resistor 42 and inductor 41, and when the frequency of the signal increases, the impedance of the inductor increases as the frequency increases according to the frequency response characteristic of the inductor, that is, the resistance of the feedback terminal is increased by this design, and the gain of the amplifier circuit increases with the frequency. The parameters of the inductor 41 can be adjusted according to actual conditions to obtain a required gain-frequency variation curve, so that the amplitudes of different frequency components in the OCT signal can be kept at the same level.
It should be noted that fig. 4 and fig. 5 are basic structural diagrams of an amplifier, which are not limited to this circuit structure, and other amplifier circuit structures may be adopted in practical applications, and the impedance of the feedback end may also be changed with frequency by using other circuit structures.
Example 6:
referring to fig. 6, fig. 6 is a graph showing the uncompensated OCT signal light according to the present invention and the gain curve of the frequency-dependent detection circuit under ideal conditions, and as shown in a curve 47 of fig. 6, the light reflected from each interface of the sample 45 shows several peaks in the OCT signal, and due to absorption and scattering in the sample, the signal intensity decays in an e-exponential manner, and the amplitude difference between the deep signal and the surface signal is too large. The curve 46 shown in fig. 6 is a gain curve for the frequency dependent detection circuit, the gain increasing with frequency.
Example 7:
referring to fig. 7, fig. 7 is a graph of compensated OCT signal amplitude provided by the present invention, and fig. 7 shows a compensated OCT signal amplitude curve 48, where the attenuation of the signal in the sample is compensated, the signal amplitudes at various depths are compensated to similar levels, the contrast of the OCT signal is improved in the imaging range, and the signals at the depths can be displayed more clearly.
Example 8:
referring to fig. 8, fig. 8 is a schematic structural diagram of a frequency-dependent detection circuit based on a high-pass filter circuit according to the present invention, and the frequency-dependent detection circuit shown in fig. 8 is a high-pass filter circuit including resistors 49, 51, 53, an operational amplifier 50, and a capacitor 52. After the OCT signal is converted into a voltage signal by the photodetector, the voltage signal is input to the inverting input terminal of the operational amplifier 50 through the resistor 53 and the capacitor 52, and the output voltage is fed back to the inverting input terminal of the operational amplifier through the resistor 51. The amplitude-frequency characteristic of the filter circuit is controlled by adjusting the parameters of the high-pass filter circuit, so that the frequency range of a transition band between a pass band and a stop band of the filter is prolonged, and the frequency band is ensured to contain the signal frequency of the OCT system. Therefore, the insertion loss of the filter circuit in a certain frequency range is reduced along with the frequency, the low-frequency component of the OCT signal is greatly suppressed, the high-frequency component is suppressed less, and the amplitudes of different frequency components in the OCT signal are kept at similar levels.
It should be noted that fig. 8 is a schematic structural diagram of a high-pass filter circuit, which is not limited to this circuit structure, and other filter circuit structures may be adopted in practical applications to implement the change of insertion loss with frequency.
Example 9:
referring to fig. 9, fig. 9 is another structural schematic diagram of a frequency-dependent detection circuit according to the present invention, which adjusts the amplitudes of different frequency components by a dual-channel method, and includes a beam splitter 54, a low pass filter 56, a beam combiner 57, and a high pass filter 59. After an OCT signal is converted into a voltage signal by a photoelectric detector, the OCT signal is divided into two paths by a beam splitter, the weaker path is transmitted to a low-pass filter 56, the stronger path is transmitted to a high-pass filter 59, the output signal is recombined to one path by the beam combiner, at the moment, a low-frequency component with smaller amplitude is obtained in one path of the low-pass filter 56, and a high-frequency component with larger amplitude is obtained in one path of the high-pass filter 57, so that the amplitudes of different frequency components in the OCT signal can be controlled, the beam splitting proportion of the beam splitter and the parameters of the low-pass filter and the high-pass filter are adjusted according to the attenuation condition of the signal in a sample, and the amplitudes of the low-frequency component and the high-frequency component of the combined signal can be kept at a similar level.
In summary, the method for improving the dynamic range of the swept-source optical coherence tomography system provided by the invention compresses the detection range of the OCT by compensating the attenuation signal caused by the propagation of the OCT signal in the biological tissue, keeps higher contrast of the OCT image in the penetration range, and enhances the depth imaging capability of the OCT system. According to the embodiment of the invention, the characteristic that the depth information in the SSOCT signal is coded by the signal frequency is utilized, and different frequencies of the interference signal are amplified by different gains. The method can effectively improve the dynamic range of the system, increase the contrast ratio, improve the resolution capability of the deep tissue micro structure and is beneficial to the popularization and application of the OCT technology in clinical medical imaging.
The invention provides equipment for improving the dynamic range of a swept-frequency light source optical coherence tomography system. The apparatus comprises: a processor, a memory, and a computer program stored in the memory and executable on the processor. The processor, when executing the computer program, implements the steps in each of the above-described method embodiments for increasing the dynamic range of a swept-source optical coherence tomography system, such as steps S1-S4 shown in fig. 1.
The Processor may be a Central Processing Unit (CPU), other general purpose Processor, a Digital Signal Processor (DSP), an Application Specific Integrated Circuit (ASIC), an off-the-shelf Programmable Gate Array (FPGA) or other Programmable logic device, discrete Gate or transistor logic, discrete hardware components, etc. The general purpose processor may be a microprocessor or the processor may be any conventional processor or the like, the processor being the control center of the apparatus for increasing the dynamic range of a swept-source optical coherence tomography system, and various interfaces and lines connecting the various parts of the entire apparatus for increasing the dynamic range of a swept-source optical coherence tomography system.
The memory can be used for storing the computer program and/or the module, and the processor can realize various functions of the device for improving the dynamic range of the swept-source optical coherence tomography system by operating or executing the computer program and/or the module stored in the memory and calling the data stored in the memory. The memory may mainly include a storage program area and a storage data area, wherein the storage program area may store an operating system, an application program required by at least one function (such as a sound playing function, an image playing function, etc.), and the like; the storage data area may store data created according to a program, and the like. In addition, the memory may include high speed random access memory, and may also include non-volatile memory, such as a hard disk, a memory, a plug-in hard disk, a Smart Media Card (SMC), a Secure Digital (SD) Card, a Flash memory Card (Flash Card), at least one magnetic disk storage device, a Flash memory device, or other volatile solid state storage device.
Wherein, the device integrated module/unit for improving the dynamic range of the swept-source optical coherence tomography system can be stored in a computer readable storage medium if the module/unit is realized in the form of a software functional unit and sold or used as an independent product. Based on such understanding, all or part of the flow of the method according to the embodiments of the present invention may also be implemented by a computer program, which may be stored in a computer-readable storage medium, and when the computer program is executed by a processor, the steps of the method embodiments may be implemented. Wherein the computer program comprises computer program code, which may be in the form of source code, object code, an executable file or some intermediate form, etc. The computer-readable medium may include: any entity or device capable of carrying the computer program code, recording medium, usb disk, removable hard disk, magnetic disk, optical disk, computer Memory, Read-Only Memory (ROM), Random Access Memory (RAM), electrical carrier wave signals, telecommunications signals, software distribution medium, and the like.
It should be noted that the above-described device embodiments are merely illustrative, where the units described as separate parts may or may not be physically separate, and the parts displayed as units may or may not be physical units, may be located in one place, or may be distributed on multiple network units. Some or all of the modules may be selected according to actual needs to achieve the purpose of the solution of the present embodiment. In addition, in the drawings of the embodiment of the apparatus provided by the present invention, the connection relationship between the modules indicates that there is a communication connection between them, and may be specifically implemented as one or more communication buses or signal lines. One of ordinary skill in the art can understand and implement it without inventive effort.
While the foregoing is directed to the preferred embodiment of the present invention, it will be understood by those skilled in the art that various changes and modifications may be made without departing from the spirit and scope of the invention.
Claims (6)
1. A method for improving the dynamic range of a swept-source optical coherence tomography system is characterized by comprising the following steps:
outputting wide-spectrum light with frequency scanned along with time through a sweep light source, and providing a corresponding trigger signal and a clock signal;
controlling the mechanical scanning of a coherent imaging system according to a trigger signal and a clock signal provided by the sweep frequency light source, receiving an electric signal obtained by the conversion of a subsequent frequency-dependent detection system, and then sending a corresponding feedback signal;
transmitting the wide-spectrum light to the surface of a sample for scanning, receiving back scattering light returned from the sample and reference light, and simultaneously interfering to generate coherent light;
detecting the coherent light and converting the coherent light into an electric signal, adjusting the gain amplitude of different frequency components according to the frequency of the electric signal, ensuring the signal amplitudes of different depths to be at the same level, analyzing and processing the compensated signal, and simultaneously imaging in real time; wherein, the adjusting the gain amplitudes of different frequency components according to the frequency of the electrical signal specifically comprises: and calculating the attenuation amplitude of the signals with different frequencies in the sample, and providing a feedback signal according to the signal attenuation trend so as to adjust the gain amplitude of the components with different frequencies.
2. A method for increasing the dynamic range of a swept-source optical coherence tomography system as claimed in claim 1, wherein the broad spectrum light is transmitted to the surface of the sample for scanning, and the back scattered light and the reference light returned from the sample are received and interfered at the same time to generate coherent light, specifically:
splitting the broad spectrum light by 90:10 coupling to transmit 90% of the light to the sample arm and 10% of the light to the reference arm;
focusing light on the reference arm onto a reflector to obtain reference light;
mechanically scanning the light on the sample arm and focusing the light on a sample to obtain back scattered light;
and carrying out 50:50 coupling coherence on the reference light and the backscattered light to generate coherent light containing sample structure information.
3. An apparatus for increasing the dynamic range of a swept-source optical coherence tomography system, comprising: the device comprises a sweep frequency light source module, a control module, a coherent imaging module and a frequency dependence detection module;
the frequency sweeping light source module is used for outputting wide spectrum light with frequency scanned along with time through a frequency sweeping light source and providing corresponding trigger signals and clock signals;
the control module is used for controlling the mechanical scanning of the coherent imaging system according to the trigger signal and the clock signal provided by the sweep frequency light source, receiving the electric signal converted by the subsequent frequency-dependent detection system and then sending a corresponding feedback signal;
the coherent imaging module is used for transmitting the wide-spectrum light to the surface of a sample for scanning, receiving back scattering light returned from the sample and reference light, and simultaneously interfering to generate coherent light;
the frequency-dependent detection module is used for detecting the coherent light and converting the coherent light into an electric signal, adjusting the gain amplitude of different frequency components according to the frequency of the electric signal, ensuring the signal amplitudes of different depths to be at the same level, analyzing and processing the compensated signal, and simultaneously imaging in real time; wherein, the adjusting the gain amplitudes of different frequency components according to the frequency of the electrical signal specifically comprises: and calculating the attenuation amplitude of the signals with different frequencies in the sample, and providing a feedback signal according to the signal attenuation trend so as to adjust the gain amplitude of the components with different frequencies.
4. A device for increasing the dynamic range of a swept-source optical coherence tomography system as claimed in claim 3, wherein the coherent imaging module comprises a conduction unit, a reference light acquisition unit, a sample light acquisition unit and a processing unit;
the conduction unit is used for conducting 90:10 coupling light splitting on the broad spectrum light so as to conduct 90% of the light to the sample arm and conduct 10% of the light to the reference arm;
the reference light acquisition unit is used for focusing light on the reference arm on a reflector to obtain reference light;
the sample light acquisition unit is used for mechanically scanning the light on the sample arm and focusing the light on the sample to obtain back scattering light;
and the processing unit is used for performing 50:50 coupling coherence on the reference light and the back scattering light to generate coherent light containing sample structure information.
5. An apparatus for increasing the dynamic range of a swept-source optical coherence tomography system, comprising a processor, a memory, and a computer program stored in the memory and configured to be executed by the processor, the processor when executing the computer program implementing the method for increasing the dynamic range of a swept-source optical coherence tomography system as claimed in any one of claims 1 to 2.
6. A computer-readable storage medium, comprising a stored computer program, wherein the computer program when executed controls an apparatus in which the computer-readable storage medium is located to perform the method for improving dynamic range of a swept-source optical coherence tomography system as claimed in any one of claims 1 to 2.
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