CN213957153U - OCT system sensitivity measuring device - Google Patents
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- CN213957153U CN213957153U CN202023196483.7U CN202023196483U CN213957153U CN 213957153 U CN213957153 U CN 213957153U CN 202023196483 U CN202023196483 U CN 202023196483U CN 213957153 U CN213957153 U CN 213957153U
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- G01M—TESTING STATIC OR DYNAMIC BALANCE OF MACHINES OR STRUCTURES; TESTING OF STRUCTURES OR APPARATUS, NOT OTHERWISE PROVIDED FOR
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Abstract
The application discloses OCT system sensitivity measuring device, including OCT system and measuring mechanism, measuring mechanism includes sampling arm and sample thing, sampling arm includes variable optical attenuator and fiber lens, just variable optical attenuator, fiber lens and sample thing are coaxial, OCT system with the first end of variable optical attenuator is connected, the second end of variable optical attenuator with fiber lens is connected. The device can conveniently adjust the attenuation in the sampling arm, ensures the high quality of a sampling optical signal, can directly measure the system noise by using the OCT system, can simply, conveniently and accurately obtain the sensitivity of the whole OCT system, does not need an expensive light beam analyzer and an Optical Spectrum Analyzer (OSA), comprises the optical receiver noise of the OCT system, and is very suitable for being used in actual production.
Description
Technical Field
The application relates to the technical field of optical interference tomography, in particular to an OCT system sensitivity measuring device.
Background
Optical interference tomography (OCT) is a biomedical imaging technique similar to ultrasound. The method obtains a cross-section image and a three-dimensional image of a biological tissue by measuring back scattered light or reflected light of a sample, has the advantages of non-invasion, high resolution, in-vivo imaging and the like, and is widely applied to clinical diagnosis and research of ophthalmology, dermatology, cardiovascular medicine and the like at present.
Early OCT systems were dominated by time-domain OCT. In order to increase the imaging speed of OCT systems, researchers have proposed frequency domain OCT systems. Frequency domain OCT has higher sensitivity than time domain OCT. The sensitivity reflects the ability of the OCT system to detect weak signals. The higher the sensitivity is, the stronger the system has the capability of detecting weak signals, and the larger the imaging depth of the sample is, so that more structural information of the sample can be obtained. Therefore, it is important to test the sensitivity of the OCT system.
The sensitivity of an optical interference tomography system refers to the maximum attenuation of an optical signal that can be allowed by the sample arm of the optical interference tomography system. What affects the sensitivity of an optical interference tomography system is the intensity of the received optical signal, which depends on the output optical power of the light source and the optical path attenuation, and the system noise, which comes from the light source, the passive optical path and the light reception. The common imaging system mainly depends on the optical structure of the imaging lens, the endoscopic OCT realizes high-sensitivity light coherent reception by returning light signals collected by the fiber lens to an interferometer to perform interference beat frequency with reference light, the balance detection is adopted to remove direct current signals, the photoelectric conversion efficiency is improved, the photoelectric conversion is completed, images are reconstructed, and the light transmission performance has direct influence on the OCT imaging quality. As with optical communication transmission links, the noise of OCT optical transmission links comes from 3 points: the light source noise (quantum noise and mode noise RIN, light path noise MPI, detector thermal noise, the sweep frequency OCT light source adopts a single-mode laser with extremely low noise, the mode noise of the extremely low RIN is less than 120dBc/Hz and can be ignored, only shot noise (quantum noise) exists, the MPI noise is reduced through controlling the connection point of the light path, the high-quality light coherent receiving and balanced detection are realized, the MPI noise and the receiver thermal noise can be reduced to be lower than the light source quantum noise, the quantum limit transmission is realized, and the SS-OCT system can realize the sensitivity of about 120dB approaching the theoretical quantum limit transmission at the wavelength of 1310 nm.
The effective dynamic range of the optical receiver is only 30-40 dB, and the sensitivity range of 120dB is measured, so that a fixed attenuation must be introduced, an optical signal is exhausted to the optimal receiving dynamic range of the receiver in advance, then the signal-to-noise ratio of the received signal is measured, and the optical sensitivity of the system is the fixed attenuation plus the signal-to-noise ratio. However, there is no consensus in academia and industry on how to accurately measure the signal-to-noise ratio and how to obtain the sensitivity of the whole system after introducing a fixed attenuation. The most common method at present is to use an optical spectrum analyzer osa (optical spectrum analyzer) to measure the SNR of an optical signal entering a receiver, or to use a beam analyzer to measure a point spread function PSF (point spread function) of received light, where the difference between the peak of the PSF and noise is the signal-to-noise ratio, and the sensitivity is the fixed attenuation + the signal-to-noise ratio. The disadvantage of this method is that the photoelectric conversion in the OSA and the beam analyzer is actually different from the photoelectric receiver in the OCT system, and therefore the resulting signal-to-noise ratio does not represent the noise performance of the whole OCT system.
SUMMERY OF THE UTILITY MODEL
In view of the above, the present application provides a method and an apparatus for measuring sensitivity of an OCT system, which can not only conveniently adjust the attenuation in the sampling arm, but also ensure high quality of the sampled optical signal, and also directly measure the system noise by using the OCT system itself, and can simply and accurately obtain the sensitivity of the whole OCT system, and the method and the apparatus do not need an expensive optical beam analyzer and an expensive optical spectrum analyzer OSA, and also include the optical receiver noise of the OCT system itself, and are very suitable for being used in actual production.
To achieve the above object, according to one aspect of the present application, there is provided an OCT system sensitivity measurement method.
The present application provides the following technical solutions.
1. An OCT system sensitivity measuring method is characterized by comprising the following steps:
the scanning light source emits light signals;
splitting the optical signal into an initial sampled optical signal and an initial reference optical signal;
an initial reference optical signal enters a reference arm;
2N +1 times of attenuation occurs after the initial sampling optical signal enters a sampling arm;
the output reference optical signal reflected from the reference arm and the output sampling optical signal reflected from the sampling arm interfere to form an interference optical signal;
converting the interference optical signal into an electrical signal;
converting the electric signal into an FFT spectrum, and obtaining a signal-to-noise ratio through the FFT spectrum so as to calculate the sensitivity of the OCT system;
the sensitivity of the OCT system is equal to the attenuation of a sampling light signal + the signal-to-noise ratio, the sensitivity of the OCT system is S, the attenuation of the sampling light signal is FA, and the signal-to-noise ratio is SNR (signal-to-noise ratio), namely, S is equal to FA + SNR;
the attenuation amount of the sampling optical signal is 2 Nx the first attenuation amount + the second attenuation amount; n is more than or equal to 1.
2. The OCT system sensitivity measuring method according to item 1 is characterized in that the OCT system comprises a scanning light source, a spectroscope, a reference arm, an imaging system interface, an interference module, a balance detector, an FFT conversion module and a display module, wherein the imaging system interface is connected with a sampling arm, and a sampling object is arranged on one side of the sampling arm.
3. The OCT system sensitivity measuring method according to claim 2, wherein the scanning light source emits a weak coherent light signal, the spectroscope divides the weak coherent light signal into an initial sampling light signal and an initial reference light signal, the output reference light signal reflected by the reference arm and the sampling arm interferes with the output sampling light signal in the interference module to form an interference light signal, the interference light signal is converted into an electrical signal by the balance detector, and the electrical signal is converted into an FFT spectrum by the FFT conversion module and the display module and displayed on the screen of the display module.
4. The OCT system sensitivity measurement method according to item 3, wherein the sampling arm includes a variable optical attenuator and a fiber lens, an initial sampling optical signal enters the sampling arm, and first sequentially passes through the variable optical attenuator and the fiber lens to irradiate onto a sample, and the sampling optical signal is transmitted and reflected on the sample and then sequentially passes through the fiber lens and the variable optical attenuator to be output;
the variable optical attenuator is used for adjusting the attenuation amount of the initial sampling optical signal, so that the sampling optical signal output by the sampling arm is changed.
5. The OCT system sensitivity measurement method according to any one of claims 1 to 4, wherein an attenuation amount of the sampled optical signal occurring after 2N times of passing through the variable optical attenuator is 2N × a first attenuation amount; the attenuation of the sampling optical signal after being transmitted on the sampling object is a second attenuation;
the first attenuation is a fixed attenuation of the variable optical attenuator;
the reflectivity of the sampling object is R;
the second attenuation amount Δ x is 10lg (r).
6. The OCT system sensitivity measurement method of item 4, wherein the fixed attenuation of the variable optical attenuator is 0-50 dB.
7. The method for measuring the sensitivity of the OCT system according to item 4, wherein the sample is a plane mirror, and the reflectivity of the plane mirror is 30% -100%, preferably 80% -100%; the plane of the sampling object and the emergent light beam of the fiber lens are vertically arranged.
8. The OCT system sensitivity measurement method according to item 1, wherein the signal-to-noise ratio is FFT spectrum peak height-noise mean-standard deviation;
the FFT spectrum peak height is the peak height when the FFT spectrum peak reaches the maximum.
9. The OCT system sensitivity measurement method according to item 2, characterized in that the wavelength of the weak coherent optical signal emitted by the swept-frequency light source is 820 nm-1500 nm, the bandwidth is 50 nm-260 nm, and the scanning frequency is 5 kHz-10 MHz.
10. The OCT system sensitivity measuring method according to claim 2, wherein a plane mirror is disposed in the reference arm, and the initial reference light signal enters the reference arm, and is reflected by the plane mirror and then emitted, so as to form the output reference light signal.
11. The OCT system sensitivity measuring device is characterized by comprising an OCT system and a measuring mechanism, wherein the measuring mechanism comprises a sampling arm and a sample, the sampling arm comprises a variable optical attenuator and a fiber lens, the variable optical attenuator, the fiber lens and the sample are coaxial, the OCT system is connected with a first end of the variable optical attenuator, and a second end of the variable optical attenuator is connected with the fiber lens.
12. An OCT system sensitivity measuring device according to item 11, characterized in that the OCT system is provided with an imaging system interface, the first end of the variable optical attenuator is provided with an optical input interface, and the imaging system interface of the OCT system is connected to the optical input interface on the first end of the variable optical attenuator.
13. An OCT system sensitivity measuring device according to item 11, wherein a second end of the variable optical attenuator is connected to the fiber lens via an optical fiber.
14. An OCT system sensitivity measuring device according to claim 11, wherein the sample is a flat mirror, and a mirror surface of the flat mirror and an outgoing beam of the fiber lens are vertically disposed so that a light beam outgoing from the fiber lens is perpendicularly incident on the flat mirror;
the reflectivity of the plane mirror is 30-100%, preferably 80-100%.
15. An OCT system sensitivity measuring device according to claim 11, wherein the OCT system includes a scanning light source, a spectroscope, a reference arm, an interference module, a balance detector, an FFT conversion module, and a display module, the scanning light source emits a weak coherent light signal, the spectroscope divides the weak coherent light signal into an initial sampling light signal and an initial reference light signal, an output reference light signal reflected by the reference arm and the sampling arm interferes with the output sampling light signal in the interference module to form an interference light signal, the interference light signal is converted into an electrical signal by the balance detector, and the electrical signal is converted into an FFT spectrum by the FFT conversion module and the display module and displayed on a screen of the display module.
16. An OCT system sensitivity measuring device according to item 11, characterized in that the length of the sampling arm coincides with the length of the reference arm of the OCT system.
17. An OCT system sensitivity measuring device according to item 11, characterized in that the distance between the fiber lens and the sample does not exceed 1.5 mm.
18. The OCT system sensitivity measuring device according to item 11, wherein the variable optical attenuator has a fixed attenuation of 0 to 50 dB.
19. An OCT system sensitivity measuring device according to claim 11, characterized in that the reflectivity of the plane mirror is 30% to 100%, preferably 80% to 100%.
According to the OCT system sensitivity measuring method, the scanning light source emits light signals, the light signals are divided into initial sampling light signals and initial reference light signals, and an FFT spectrogram is obtained through interference, photoelectric conversion, FFT change and image sampling of two paths of light of the output reference light signals and the output sampling light signals. By moving the sampling object away from the fiber lens, the interference light intensity of the corresponding position of the sampling object can be obtained on the FFT spectrogram; the measurement method can be used for OCT systems with different wavelengths and frequencies, and has general applicability.
According to the OCT system sensitivity measuring method or device, the signal-to-noise ratio of the corresponding attenuation can be obtained by gradually increasing the fixed attenuation of the variable optical attenuator, and the OCT system ultimate sensitivity is finally obtained, so that the OCT system sensitivity measuring method is more convenient and efficient, low in cost and convenient to operate. The device has simple structure, can simply and accurately obtain the sensitivity of the whole OCT system, does not need expensive light beam analyzer and spectrum analyzer OSA, also comprises the noise of the optical receiver of the OCT system, and is very suitable for being used in actual production.
Drawings
The drawings are included to provide a further understanding of the application and are not to be construed as limiting the application. Wherein:
fig. 1 is a schematic structural diagram of an OCT system sensitivity measurement apparatus according to the present application.
Fig. 2 is a schematic structural diagram of an OCT system sensitivity measurement apparatus according to the present application.
List of reference numerals
1-OCT system, 2-optical fiber, 3-variable optical attenuator, 4-fiber lens, 5-sampling object.
Detailed Description
The following description of the exemplary embodiments of the present application, including various details of the embodiments of the present application to assist in understanding, should be taken as exemplary only. Accordingly, those of ordinary skill in the art will recognize that various changes and modifications of the embodiments described herein can be made without departing from the scope and spirit of the present application. Also, descriptions of well-known functions and constructions are omitted in the following description for clarity and conciseness.
Because the sensitivity of the sweep-frequency optical interference tomography system only depends on the light source output light power and the light path attenuation of the sweep-frequency light source, the system noise comes from the light source and the light receiving, and has no relation with the mechanical movement of the imaging guide pipe and the guide pipe design, while the sensitivity of the sweep-frequency optical interference tomography system is 90-120 dB, in order to accurately measure, all interferences such as the mechanical movement and the guide pipe design must be eliminated, therefore, the light path is adjusted in the test, the imaging guide pipe is replaced by the fiber lens and the plane mirror, the adjustment can not change the sensitivity of the system at all, and the adjustment is only used for optimizing signals, eliminating interference and improving the measurement precision.
The measurement method described in the present application is to directly obtain the SNR from the OCT system, and does not require expensive beam analyzer and spectrum analyzer OSA, but also includes the optical receiver noise of the OCT system itself. The OCT system is a point-to-point optical communication transmission link: the laser emitted by the light source irradiates the detected object from the sample arm, the reflected/scattered light returned by the object interferes with the reference arm, the interference light signal enters the balance detector for photoelectric conversion, then the obtained electric signal is sampled, the FFT image is processed, and the frequency spectrum of the FFT light intensity can be directly displayed on the display screen of the OCT system. This FFT optical intensity spectrum is the signal-to-noise ratio of the optical signal received by the system. Unlike the SNR from the beam analyzer and the spectrum analyzer OSA, the SNR of the FFT spectrum comes from the photodetector of the system itself and thus contains the photodetection noise of the system itself, and the OCT reconstructed image is based on the FFT signal, so the signal-to-noise ratio of the signal directly determines the quality of the reconstructed image.
Because the sensitivity of the scanning optical interference tomography system is very high, if the light attenuation is directly performed on the sample arm, the FFT signal peak value of the observation system is reduced to be equivalent to the noise for detection, and a stable and reliable measurement result is difficult to obtain. Therefore, a reasonable measure should be the combination of optical attenuation and signal-to-noise ratio: firstly, the optical path is attenuated to a certain degree, the optical receiver obtains the best signal-to-noise ratio, then the signal-to-noise ratio of the system is accurately measured (the signal-to-noise ratio is the peak height-the noise mean value-the standard deviation), and the attenuation amount + the signal-to-noise ratio is the sensitivity.
The application provides an OCT system sensitivity measuring method, which comprises the following steps:
the method comprises the following steps: the scanning light source emits light signals;
step two: splitting the optical signal into an initial sampled optical signal and an initial reference optical signal;
step three: an initial reference optical signal enters a reference arm;
step four: 2N +1 times of attenuation occurs after the initial sampling optical signal enters a sampling arm;
step five: the output reference optical signal reflected from the reference arm and the output sampling optical signal reflected from the sampling arm interfere to form an interference optical signal;
step six: converting the interference optical signal into an electrical signal;
step seven: converting the electric signal into an FFT spectrum, and obtaining a signal-to-noise ratio through the FFT spectrum so as to calculate the sensitivity of the OCT system;
the OCT system sensitivity is S, the attenuation of the sampling light signal is FA, and the signal-to-noise ratio is SNR, that is, S is FA + SNR.
The attenuation amount of the sampling optical signal is 2 Nx the first attenuation amount plus the second attenuation amount, and N is larger than or equal to 1.
According to the OCT system sensitivity measuring method, the scanning light source emits light signals, the light signals are divided into initial sampling light signals and initial reference light signals, the initial sampling light signals are output after being attenuated by the sampling arm, the initial reference light signals are output through the reference arm to output reference light information, the output sampling light signals and the output reference light signals are subjected to interference, photoelectric conversion, FFT change and image sampling, and FFT spectrums are obtained. From the FFT spectrum the signal to noise ratio can be read.
In this application, the OCT system includes scanning light source, spectroscope, reference arm, imaging system interface, interference module, balanced detector, FFT transform module and display module, imaging system interface connection has measurement mechanism, measurement mechanism includes sampling arm and sample thing, imaging system interface with the first end of sampling arm is connected, the sample thing is close to the second end setting of sampling arm, just the sample thing with adopt the coaxial and interval setting of wall.
The scanning light source is used for providing a light signal, the beam splitter is used for splitting the light signal into an initial reference light signal and an initial sampling light signal, the reference arm is used for outputting the initial reference light signal through reflection, the sampling arm is used for attenuating the light quantity of the initial sampling light signal and outputting the initial sampling light signal through reflection, the interference module is used for providing a condition for interference of the output sampling light signal and the output reference light signal, the balance detector is used for converting the interference light signal into an electric signal, the FFT conversion module is used for converting the electric signal into an FFT spectrum, and the display module is used for displaying the FFT spectrum.
The reference arm and the sampling arm have the same length, and the output reference optical signal and the output sampling optical signal are output simultaneously and interfere with each other.
In this application, scanning light source transmission weak coherent light signal, the spectroscope will weak coherent light signal divides into initial sampling light signal and initial reference light signal, through reference arm and sampling arm reflect the output reference light signal that comes out and take place to interfere with output sampling light signal in interfering the module, form and interfere the light signal, it converts the signal of telecommunication into the signal of telecommunication through balanced detector, the signal of telecommunication changes the FFT spectrum through FFT transform module and display module and shows on display module's screen into.
In the application, the sampling arm comprises a variable optical attenuator, a fiber lens and a sampling object, an initial sampling optical signal enters the sampling arm and is irradiated on the sampling object through the variable optical attenuator and the fiber lens in sequence, and the sampling optical signal is transmitted and reflected on the sampling object and then is output through the fiber lens and the variable optical attenuator in sequence;
the variable optical attenuator is used for adjusting the attenuation amount of the initial sampling optical signal, so that the sampling optical signal output by the sampling arm is changed.
The variable optical attenuator is an important passive optical device in optical fiber communication, and realizes real-time control on signals by attenuating transmission optical power.
The initial sampling optical signal is attenuated for 2N +1 times in the sampling arm, wherein 2N times are attenuated by the variable optical attenuator, the attenuation of 2N times is the same, and the attenuation is determined by the parameter of the variable optical attenuator. Namely, the attenuation generated by the sampling optical signal passing through the variable optical attenuator twice is 2 Nx first attenuation; the attenuation of the sampling optical signal after being emitted on the sampling object is a second attenuation;
the first attenuation is a fixed attenuation of the variable optical attenuator;
the reflectivity of the sampling object is R;
the second attenuation amount Δ x is 10lg (r).
One or more variable optical attenuators can be arranged in the sampling arm, and the variable optical attenuators are determined according to actual conditions. When the number of the variable optical attenuators in the sampling arm is 1, the initial sampling optical signal is attenuated for 3 times in the sampling arm, and the number of the variable optical attenuators is N.
In the present application, the fixed attenuation of the variable optical attenuator is 0-50 dB.
The fixed attenuation amounts of the variable optical attenuators may be 0, 5dB, 10dB, 15dB, 20dB, 25dB, 30dB, 35dB, 40dB, 45dB, 50 dB.
In the present application, the sample is a plane mirror, and the reflectivity of the plane mirror is 30% to 100%, preferably 80% to 100%; the plane of the sampling object and the emergent light beam of the fiber lens are vertically arranged to reduce the loss of light.
The reflectivity of the plane mirror can be 30%, 40%, 50%, 60%, 70%, 80%, 90% and 100%.
In the present application, the signal-to-noise ratio is FFT spectral peak height-noise mean-standard deviation;
the FFT spectrum peak height is the peak height when the FFT spectrum peak reaches the maximum. Wherein the FFT spectrum peak height, the noise average value and the standard deviation can be obtained by an OCT system.
In the application, the wavelength of the weak coherent optical signal emitted by the sweep frequency light source is 820 nm-1500 nm, the bandwidth is 50 nm-260 nm, and the scanning frequency is 5 kHz-10 MHz.
In the present application, a plane mirror is disposed in the reference arm, and the initial reference optical signal enters the reference arm and is emitted after being reflected by the plane mirror, so as to form the output reference optical signal.
As shown in fig. 1 and 2, the present application further provides an OCT system sensitivity measuring apparatus, including an OCT system 1 and a measuring mechanism, where the measuring mechanism includes a sampling arm and a sample 5, the sampling arm includes a variable optical attenuator 3 and a fiber lens 4, the variable optical attenuator 3, the fiber lens 4, and the sample 5 are coaxial, the OCT system 1 is connected to a first end of the variable optical attenuator, and a second end of the variable optical attenuator is connected to the fiber lens 4.
The initial sampling optical signal enters the variable optical attenuator 3 and then is attenuated, the attenuated sampling optical signal passes through the optical fiber lens 4 and is not attenuated in the optical fiber lens 4, the sampling optical signal is irradiated on the sample 5, then the sampling optical signal is reflected on the sample 5, and the reflected sampling optical signal is sequentially irradiated into the optical fiber lens 4 and the variable optical attenuator 3 and enters the OCT system 1.
The OCT system 1 may be an optical interference tomography system.
The OCT system sensitivity measurement method described above is a method of measuring by means of an OCT system sensitivity measurement device.
In the present application, the OCT system 1 is provided with an imaging system interface, the first end of the variable optical attenuator 3 is provided with an optical input interface, and the imaging system interface of the OCT system 1 is connected to the optical input interface at the first end of the variable optical attenuator 3. The imaging system interface communicates with the light input interface via an optical fibre 2.
In the present application, the second end of the variable optical attenuator 3 is connected to the fiber lens via an optical fiber 2.
In this application, the sampling object 5 is a plane mirror, and the mirror surface of the plane mirror is arranged right opposite to the optical fiber lens 4, so that the light emitted from the optical fiber lens 4 is perpendicularly incident on the plane mirror.
In this application, the OCT system 1 includes a scanning light source, a spectroscope, a reference arm, an interference module, a balance detector, an FFT conversion module, and a display module, where the scanning light source emits a weak coherent light signal, the spectroscope divides the weak coherent light signal into an initial sampling light signal and an initial reference light signal, an output reference light signal reflected by the reference arm and the sampling arm interferes with the output sampling light signal in the interference module to form an interference light signal, the interference light signal is converted into an electrical signal by the balance detector, and the electrical signal is converted into an FFT spectrum by the FFT conversion module and the display module and displayed on a screen of the display module.
In the present application, the length of the sampling arm coincides with the length of the reference arm of the OCT system 1, so that the optical signal reflected from the reference arm and the optical signal output from the sampling arm can interfere.
In the present application, the distance between the fiber lens 4 and the sample object 5 is not more than 1.5mm, so as to reduce the error of the attenuation of the sampled optical signal, thereby improving the measurement accuracy of the detection device and reducing the error.
Example 1
An OCT system sensitivity measuring method comprises the following steps:
the method comprises the following steps: the scanning light source emits light signals;
step two: splitting the optical signal into an initial sampled optical signal and an initial reference optical signal;
step three: an initial reference optical signal enters a reference arm;
step four: an initial sampling optical signal enters a sampling arm, the sampling optical signal is subjected to two times of fixed attenuation (the fixed attenuation is a first attenuation) in the sampling arm, the attenuation of the two times of fixed attenuation is 2 multiplied by 35dB, namely the first attenuation is 35dB, and the sampling optical signal is reflected back to an optical fiber lens after reaching a plane mirror through the optical fiber lens, wherein the emissivity of the plane mirror is 80%;
step five: the output reference optical signal reflected from the reference arm and the output sampling optical signal reflected from the sampling arm interfere to form an interference optical signal;
step six: converting the interference optical signal into an electrical signal;
step seven: and converting the electric signal into an FFT frequency spectrum, and obtaining a signal-to-noise ratio through the FFT frequency spectrum so as to calculate the sensitivity of the OCT system.
Examples 2 and 3 are different from example 1 in that the first attenuation amount and the plane mirror emissivity are different in examples 2 and 3. The first delta attenuation for example 2 was 37.5dB and the plane mirror reflectance was 90%. The first attenuation of example 3 was 40dB and the reflectance of the mirror was 100%.
Comparative example 1
The OCT system sensitivity measuring method comprises the following steps:
the method comprises the following steps: the scanning light source emits light signals;
step two: splitting the optical signal into an initial sampled optical signal and an initial reference optical signal;
step three: an initial reference optical signal enters a reference arm;
step four: an initial sampling optical signal enters a sampling arm, the sampling optical signal is subjected to 2 x 30dB fixed attenuation in the sampling arm, and is transmitted back to an imaging guide pipe after reaching a planar mirror through a connected imaging guide pipe, and the emissivity of the planar mirror is 0.1% (due to the limitation of the light-emitting angle of the imaging guide pipe and the relative position of the planar mirror, the optical signal returned by the reflector is very weak);
step five: the output reference optical signal reflected from the reference arm and the output sampling optical signal reflected from the sampling arm interfere to form an interference optical signal;
step six: converting the interference optical signal into an electrical signal;
step seven: and converting the electric signal into an FFT frequency spectrum, and calculating the sensitivity of the OCT system by the observation system with equivalent FFT signal peak value and noise.
Comparative examples 2 and 3 differ from comparative example 1 in that the first delta attenuation and the imaging catheter trans-plane emissivity in comparative example 2 and comparative example 3 differ. The first attenuation of comparative example 2 was 35dB and the in-plane mirror reflectance was 0.2%. The first attenuation of comparative example 3 was 40dB, and the reflectance of the mirror was 0.4%.
Table 1 shows the sensitivity of detection and other parameters of the comparative methods of the examples
| Signal to noise ratio/dB | Plane mirror reflectivity | First attenuation/dB | Second attenuation/dB | sensitivity/dB | |
| Example 1 | 48.16 | 80％ | 35 | 0.97 | 119.13 |
| Example 2 | 43.81 | 90％ | 37.5 | 0.46 | 119.27 |
| Example 3 | 39.35 | 100％ | 40 | 0 | 119.35 |
| Comparative example 1 | 0 | 0.1％ | 30 | 30 | 90 |
| Comparative example 2 | 0 | 0.2％ | 35 | 26.99 | 96.99 |
| Comparative example 3 | 0 | 0.4％ | 40 | 23.98 | 103.98 |
And (3) knotting: as can be seen from the above table, with the method described in the present application, the detected sensitivity is close to the ultimate sensitivity (120dB) of the OCT system, whereas in comparative examples 1-3, due to the limitation of the light-emitting angle of the imaging catheter and the relative position of the plane mirror, the optical signal returned by the mirror is very weak, so the signal-to-noise ratio is 0, the detected sensitivity is greatly different from the ultimate sensitivity, and the measurement result fluctuates greatly. Therefore, by adjusting the attenuation in the sampling arm and simultaneously ensuring very small attenuation through the plane mirror, the method ensures the high quality of the sampling optical signal, avoids uncertain attenuation introduced by the imaging catheter, and can directly obtain the signal-to-noise ratio by utilizing the noise and interference signals of the measurement system of the OCT system, thereby simply, conveniently and accurately obtaining the sensitivity of the whole OCT system.
While embodiments of the present application have been described above in connection with specific embodiments thereof, the present application is not limited to the above-described embodiments and fields of application, which are intended to be illustrative, instructive, and not restrictive. Those skilled in the art, having the benefit of this disclosure, may effect numerous modifications thereto and changes may be made without departing from the scope of the invention as defined by the appended claims.
Claims (10)
1. The OCT system sensitivity measuring device is characterized by comprising an OCT system and a measuring mechanism, wherein the measuring mechanism comprises a sampling arm and a sample, the sampling arm comprises a variable optical attenuator and a fiber lens, the variable optical attenuator, the fiber lens and the sample are coaxial, the OCT system is connected with a first end of the variable optical attenuator, and a second end of the variable optical attenuator is connected with the fiber lens.
2. The OCT system sensitivity measurement device of claim 1, wherein the OCT system is configured with an imaging system interface, the first end of the variable optical attenuator is configured with an optical input interface, and the imaging system interface of the OCT system is connected to the optical input interface at the first end of the variable optical attenuator.
3. The OCT system sensitivity measuring device of claim 1, wherein a second end of the variable optical attenuator is connected to the fiber lens via an optical fiber.
4. The OCT system of claim 1, wherein the sample is a flat mirror, and a mirror surface of the flat mirror and the exit beam of the fiber lens are vertically disposed such that the light exiting from the fiber lens is perpendicularly incident on the flat mirror.
5. The OCT system of claim 1, further comprising a scanning light source, a beam splitter, a reference arm, an interference module, a balance detector, an FFT transformation module, and a display module, wherein the scanning light source emits a weak coherent light signal, the beam splitter splits the weak coherent light signal into an initial sampling light signal and an initial reference light signal, an output reference light signal reflected by the reference arm and the sampling arm interferes with the output sampling light signal in the interference module to form an interference light signal, the interference light signal is converted into an electrical signal by the balance detector, and the electrical signal is converted into an FFT spectrum by the FFT transformation module and the display module and displayed on a screen of the display module.
6. The OCT system sensitivity measurement device of claim 1, wherein a length of the sampling arm is substantially the same as a length of a reference arm of the OCT system.
7. The OCT system of claim 1, wherein said fiber lens is spaced from said sample by a distance not exceeding 1.5 mm.
8. The OCT system sensitivity measuring device of claim 1, wherein the fixed attenuation of the variable optical attenuator is 0-50 dB.
9. The OCT system sensitivity measuring device of claim 4, wherein the reflectivity of the planar mirror is between 30% and 100%.
10. The OCT system sensitivity measuring device of claim 4, wherein the reflectivity of the planar mirror is between 80% and 100%.
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