An integrated reference arm for optical coherence tomography

Abstract

The present invention relates to an integrated reference arm for optical coherence tomography, comprising an optical fiber coupler, a polarization regulator and an optical delay device. An optical fiber connected to a port of the optical fiber coupler is wound around the polarization regulator for at least one turn and then connected to the optical delay device. In the present invention, the delay optical fiber connected to the reference arm end of the optical fiber coupler is connected to the optical delay device to extend the light travel, thereby achieving a good coupling interference effect. In addition, the internal stress of the optical fiber is changed by the polarization regulator in the middle, thereby changing the refraction state of the light, thereby performing polarization control on the light.

Description

Technical Field

[0001] The invention relates to the technical field of optical scanning imaging, and in particular to an integrated reference arm for optical coherence tomography. Background Art

[0002] Optical coherence tomography (OCT) is a real-time, non-invasive, three-dimensional imaging technology. Since the birth of OCT technology in 1996, it has been widely used in many medical fields such as ophthalmology, gastrointestinal tract, cardiovascular, and skin. At present, related laboratory research topics and commercial products are in a stage of vigorous development. OCT technology is based on the principle of low-coherence light interference, and the core of its equipment is an interferometer. Interferometers usually have two forms: free space and optical fiber. Due to the characteristics of optical fiber such as small size and high stability, OCT generally uses 2x2 fiber couplers or other variations of optical fiber devices as the core components of the interferometer. The interferometer contains four ports, corresponding to the light source, sample arm, reference arm, and optical signal acquisition device, which together constitute the core components of OCT.

[0003] Early OCT belonged to time domain OCT, which samples broadband optical signals in time space. The mainstream OCT products on the market now are frequency domain OCT, which samples optical signals in frequency space. Frequency domain OCT is divided into two forms: one is to use a broadband light source and a spectrometer as the acquisition device; the other is to use a swept frequency light source and a high-speed photodiode or balanced detector as the acquisition device. Except for the light source and optical signal acquisition device, these two forms of OCT are similar in other aspects.

[0004] The main function of the sample arm is to send the detection light to the sample to be detected and collect the return signal from the sample. The design of the sample arm mainly depends on the form of the sample to be detected. For example, for ordinary in vitro samples, the corresponding sample arm is generally an optical structure similar to a scanning microscope; for living cavities, the sample arm needs to include a scanning probe similar to an endoscope; and for the fundus, the sample arm design must ensure that the light signal passes through the pupil to the fundus as unimpeded as possible, while considering the focusing adjustment of the anterior segment of the eye.

[0005] The reference arm of OCT has relatively few changes. Its main function is to provide a stable reference signal to interfere with the signal returned by the sample arm, so as to further collect images. There are two types of reference arms: one is a free-space reference arm. The main component of this type of reference arm is an optical delay line, which generally provides optical path adjustment to match the optical path of the sample arm; the other is a fiber reference arm. This type of reference beam propagates completely in the optical fiber, is less affected by the outside world, and is relatively stable, but the optical path cannot be freely adjusted. Generally, the OCT using this type of reference arm places the optical path adjustment function in the sample arm. The free-space reference arm is larger than the fiber reference arm, but its main advantage is that the optical path is easy to adjust and has strong adaptability. Even the same reference arm can be used with different sample arms to form a complete OCT. Regardless of the type of reference arm, the signal directly reflected back is often much higher than the signal intensity returned by the sample arm. In order to match the intensity of the two signals, it is generally necessary to add an attenuator to the reference arm to appropriately weaken the reference arm signal. In addition, considering the phenomenon of birefringence of the optical fiber, it is generally necessary to add a fiber polarization adjustment device to the OCT optical path to make the two signals match as much as possible in terms of polarization, and finally obtain excellent signals. So in a broad sense, the OCT reference arm includes not only the optical delay line, but also the optical attenuator and polarization regulator.

[0006] Currently, the optical delay line products used for OCT on the market are generally single-function products. It is necessary to purchase or process the optical delay line, fiber polarization modulator, and adjustable attenuator separately for assembly and debugging. Moreover, manual adjustment is mainly used, which is only suitable for the construction of laboratory platforms, with slow development speed and great integration difficulty. Summary of the invention

[0007] In order to solve the above technical problems, the present invention provides an integrated reference arm for optical coherence tomography.

[0008] The technical solution of the present invention is: an integrated reference arm for optical coherence tomography, comprising a fiber coupler, a polarization regulator and an optical delay device, wherein an optical fiber connected to one port of the fiber coupler is wound around the polarization regulator for at least one turn and then connected to the optical delay device.

[0009] Preferably, the optical fiber is wound before and after the polarization adjuster and fixed respectively.

[0010] Preferably, the polarization adjuster includes a deflection adjustment motor and a deflection adjustment rocker arm, the deflection adjustment rocker arm is connected to the output shaft of the deflection adjustment motor through a crank, the optical fiber is wound around the deflection adjustment rocker arm for at least one circle, and fixing seats for fixing the optical fiber are provided on both sides of the deflection adjustment rocker arm.

[0011] Preferably, the optical delay device includes a collimator and a delay component, the optical fiber is a delay optical fiber and is connected to the collimator optical fiber port of the collimator, the delay component includes a sliding reflection angle cone and a fixed reflection angle cone, the sliding reflection angle cone is installed on a slider sliding along a linear slide rail, the light beam outlet of the collimator faces the sliding reflection angle cone, the fixed reflection angle cone is installed between the sliding reflection angle cone and the collimator and is close to the collimator, the distance between the center line of the fixed reflection angle cone and the center line of the sliding reflection angle cone is equal to the distance between the center line of the fixed reflection angle cone and the center line of the collimator, and the center line of the fixed reflection angle cone, the center line of the sliding reflection angle cone, and the center line of the collimator are located in the same plane.

[0012] Preferably, the slider is fixedly connected to the adjusting nut of the screw nut pair, and the adjusting screw of the screw nut pair is connected to the output shaft of the optical delay motor.

[0013] Preferably, the integrated reference arm also includes an adjustable optical attenuator, which includes an attenuation motor and an attenuation plate, wherein the attenuation plate is connected to the output shaft of the attenuation motor, the attenuation plate is an eccentrically arranged semicircular structure, and the attenuation plate is located in front of the collimating mirror.

[0014] Preferably, the center of the attenuation plate and the output shaft of the attenuation motor are eccentrically arranged along the straight edge of the attenuation plate, and the arc edge of the attenuation plate is located directly in front of the collimating mirror.

[0015] Preferably, the integrated reference arm comprises a closed shell, the deflection adjustment motor, the fixed seat, the optical delay motor, the linear slide rail, the attenuation motor and the collimating mirror are all fixed at the bottom of the shell, a fiber optic positioning groove is provided at the bottom of the shell, a drive controller for controlling the deflection adjustment motor, the optical delay motor and the attenuation motor is provided inside the shell, and a power interface and a USB interface connected to the drive controller are provided on the side wall of the shell.

[0016] Preferably, the fiber optic coupler is a 2x2 fiber optic coupler, and the four ports of the fiber optic coupler are respectively an input end, a reference arm end, a sample arm end and an optical signal collection end, the delay optical fiber is connected to the reference arm end, the input end is connected to the input optical fiber, the sample arm end and the optical signal collection end are respectively connected to the sample optical fiber and the signal collection optical fiber, the sample optical fiber and the signal collection optical fiber extend from the optical fiber output port on the side wall of the shell, and the input optical fiber is connected to the optical fiber connector on the side wall of the shell.

[0017] Preferably, half of the optical fiber connector is located inside the housing and connected to the input optical fiber, and the other half is located outside the housing and connected to the light source optical fiber.

[0018] The beneficial effects of the present invention are:

[0019] The delay fiber connected to the reference arm end of the fiber coupler in the present invention is connected to an optical delay device to extend the light travel distance, thereby achieving a good coupling interference effect. The internal stress of the fiber is changed by a polarization regulator in the middle, thereby changing the refraction state of the light, thereby controlling the polarization of the light.

[0020] The present invention also provides an adjustable optical attenuator, which can make the collimated light beam emitted by the collimator pass through the outer circumference of the attenuation plate, so that part of the light beam is blocked by the outer circumference of the attenuation plate. The attenuation plate is an eccentrically arranged semicircular structure, and the area of ​​the light beam blocked by the attenuation plate can be changed by rotating the attenuation plate, thereby achieving the purpose of continuously adjusting the light attenuation.

[0021] The integrated reference arm of the present invention electrically controls the polarization regulator, the adjustable optical attenuator and the optical delay device to adjust the optical path of the delay optical fiber in the integrated reference arm in real time to make it correspond to the optical path of the sample optical fiber, so that the light returned by the delay optical fiber and the sample optical fiber interferes in the optical fiber coupler, thereby improving the stability of the output optical path of the signal acquisition optical fiber.

[0022] The integrated reference arm of the present invention combines a polarization regulator, an adjustable optical attenuator and an optical delay device with a simple and ingenious design, has high integration and is easy to maintain.

[0023] The present invention is connected with a host computer and other OCT components through a driving controller and various interfaces to form a closed-loop system, which can compensate for the drift change of the optical signal in the system in real time, thereby improving the stability and availability of the OCT system. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 It is a top view schematic diagram of the internal structure of the present invention;

[0025] Figure 2 It is a schematic diagram of the three-dimensional structure of the housing of the present invention;

[0026] Figure 3 It is a structural schematic diagram of the attenuation sheet;

[0027] Figure 4 This is the control principle block diagram of the drive controller;

[0028] Figure 5 This is the circuit schematic diagram of the drive controller;

[0029] Figure 6 It is the schematic diagram of the stepper motor driving circuit in the driving controller;

[0030] Figure 7 This is the circuit schematic diagram of the USB adapter chip in the driver controller;

[0031] Figure 8 This is the schematic diagram of the power supply circuit in the drive controller;

[0032] Fig. 9 It is a principle block diagram of the present invention when applied in OCT;

[0033] In the figure: 1—drive controller; 2—deflection adjustment motor; 3—deflection adjustment rocker arm; 4—fixed seat; 5—fiber coupler; 6—fiber positioning slot; 8—attenuation motor; 9—collimation fiber port; 10—collimation mirror; 11—optical delay motor; 12—photoelectric switch; 13—linear guide rail; 14—adjustment nut; 15—sliding reflection cone; 16—slider; 17—attenuation plate; 18—fixed reflection cone; 20—power interface; 21—USB interface; 22—housing; 23—fiber connector; 24—fiber output port. DETAILED DESCRIPTION

[0034] The specific implementation of the present invention is shown in Figure 1-Figure 9 :

[0035] The technical solution of the present invention is:

[0036] Embodiment 1, an integrated reference arm for optical coherence tomography, such as Figure 1 , including a fiber coupler 5, a polarization adjuster and an optical delay device. The optical fiber connected to one port of the fiber coupler 5 is wound around the polarization adjuster for at least one turn and then connected to the optical delay device. The optical fiber is wound around the polarization adjuster and fixed before and after it is respectively wound.

[0037] like Figure 1 The polarization regulator in the integrated reference arm includes a deflection adjustment motor 2 and a deflection adjustment rocker arm 3, the deflection adjustment rocker arm 3 is connected to the output shaft of the deflection adjustment motor 2 through a crank, the optical fiber is wound around the deflection adjustment rocker arm 3 for at least one circle, and a fixing seat 4 for fixing the optical fiber is arranged on both sides of the deflection adjustment rocker arm 3. The optical delay device in the integrated reference arm includes a collimator 10 and a delay component, the optical fiber is a delay optical fiber and is connected to the collimator optical fiber port 9 of the collimator 10, the delay component includes a sliding reflection angle cone 15 and a fixed reflection angle cone 18, the sliding reflection angle cone 15 is installed on a slider 16 sliding along a linear slide rail 13, and the light beam output of the collimator 10 The opening faces the sliding reflection angle cone 15, the fixed reflection angle cone 18 is installed between the sliding reflection angle cone 15 and the collimating lens 10 and is close to the collimating lens 10, the distance between the center line of the fixed reflection angle cone 18 and the center line of the sliding reflection angle cone 15 is equal to the distance between the center line of the fixed reflection angle cone 18 and the center line of the collimating lens 10, the center line of the fixed reflection angle cone 18, the center line of the sliding reflection angle cone 15, and the center line of the collimating lens 10 are located in the same plane, the slider 16 is fixedly connected to the adjusting nut 14 of the screw nut pair, and the adjusting screw of the screw nut pair is connected to the output shaft of the optical delay motor 11.

[0038] Example 2 is substantially the same as Example 1, except that Figure 1 , 3 4. The integrated reference arm further comprises an adjustable optical attenuator, which comprises an attenuation motor 8 and an attenuation plate 17. The attenuation plate 17 is connected to the output shaft of the attenuation motor 8. The attenuation plate 17 is an eccentrically arranged semicircular structure. The attenuation plate 17 is located in front of the collimator 10. The center of the attenuation plate 17 and the output shaft of the attenuation motor 8 are eccentrically arranged along the straight edge of the attenuation plate 17. The arc edge of the attenuation plate 17 is located directly in front of the collimator 10. Figure 4 , the center B of the attenuation plate 17 is offset to one side relative to the center A of the output shaft of the attenuation motor 8.

[0039] Example 3 is substantially the same as Example 2, except that Figure 1-Figure 3 The integrated reference arm includes a closed shell 22, a deflection adjustment motor 2, a fixing seat 4, an optical delay motor 11, a linear slide 13, an attenuation motor 8, a fiber coupler 5 and a collimator 10 are all fixed at the bottom of the shell 22, a fiber positioning groove 6 is provided at the bottom of the shell 22, a driving controller 1 for controlling the deflection adjustment motor 2, the optical delay motor 11 and the attenuation motor 8 is provided inside the shell 22, a power interface 20 and a USB interface 21 connected to the driving controller 1 are provided on the side wall of the shell 22, the fiber coupler 5 is a 2x2 fiber coupler 5, and the four ports of the fiber coupler 5 are respectively an input end, a reference arm end, a sample arm end and an optical signal collection end, the delay fiber is connected to the reference arm end, and the input end is connected to The input optical fiber, the sample arm end and the optical signal collection end are connected to the sample optical fiber and the signal collection optical fiber respectively. The sample optical fiber and the signal collection optical fiber extend from the optical fiber output port 24 on the side wall of the shell 22. The input optical fiber is connected to the optical fiber connector 23 on the side wall of the shell 22. Half of the optical fiber connector 23 is located inside the shell 22 and connected to the input optical fiber, and the other half is located outside the shell 22 and connected to the light source optical fiber. Three photoelectric switches 12 are also arranged at the bottom of the shell. The three photoelectric switches 12 are distributed below the deflection adjustment rocker arm 3, on the left side of the linear slide rail 13, and below the attenuation plate 17. The three photoelectric switches 12 are distributed and connected to the control circuits of the deflection adjustment motor 2, the optical delay motor 11 and the attenuation motor 8 to play a limiting role.

[0040] In Examples 1-3, the deflection motor 2, the optical delay motor 11 and the attenuation motor 8 are all stepper motors controlled by the drive controller 1. The drive controller 1 uses an STM32F103VE chip. The drive controller 1 is connected to a stepper motor drive circuit. The specific connection is as follows: Figure 5 and 6 , the USB adapter chip circuit and power supply circuit of the driving controller 1 are as follows Figure 7 and 8 .

[0041] The delay optical fiber connected to the reference arm end of the fiber coupler in the present invention is connected to the optical delay device to extend the light travel. The light beam emitted from the reference arm end is collimated by the delay optical fiber to the collimator 10, and then propagates to the sliding reflection angle cone 15. The light beam is reflected by the sliding reflection angle cone 15 and then returns in the opposite direction. Since the incident light beam slightly deviates upward from the center of the sliding reflection angle cone 15, the returned light beam has a translation downward, and the reflected light beam is antiparallel to the incident light beam and has an equal distance from the center of the sliding reflection angle cone 15. The reflected light beam continues to propagate to the center of the fixed reflection angle cone 18, and the light beam reflected by the fixed reflection angle cone 18 returns completely along the original path to the reference arm end of the fiber coupler, wherein the sliding reflection angle cone 15 and the fixed reflection angle cone 18 are parallel to each other. The reflection angle cone 18 preferably uses a total internal reflection angle cone, and the incident surface can be coated with an anti-reflection film to improve the light transmission efficiency. The sliding reflection angle cone 15 can be moved back and forth along the linear slide rail 13 driven by the optical delay motor 11 to change the optical path of the light beam at the reference arm end and match it with the optical path of the light beam at the sample arm end, so as to achieve a good interference effect and then output it to the optical signal acquisition device through the signal acquisition optical fiber. The internal stress of the optical fiber is changed by a polarization regulator in the middle, thereby changing the refraction state of the light, thereby controlling the polarization of the light. The position state of the optical fiber in the reference arm will directly affect the interference signal, so the optical fiber is fixed by the optical fiber positioning groove 6 at the bottom of the shell 22 to prevent the optical fiber from moving uncontrolled.

[0042] An adjustable optical attenuator is arranged in the reference arm, which can make the collimated light beam emitted by the collimating mirror 10 pass through the outer circumference of the attenuation plate 17, so that part of the light beam is blocked by the outer circumference of the attenuation plate 17. The attenuation plate 17 is an eccentrically arranged semicircular structure, and the area of ​​the light beam blocked by the attenuation plate 17 can be changed by rotating the attenuation plate 17, thereby achieving the purpose of continuously adjusting the light attenuation.

[0043] The integrated reference arm of the present invention electrically controls the polarization regulator, the adjustable optical attenuator and the optical delay device to adjust the optical path of the delay optical fiber in the integrated reference arm in real time to make it correspond to the optical path of the sample optical fiber, so that the light returned by the delay optical fiber and the sample optical fiber interferes in the optical fiber coupler, thereby improving the stability of the output optical path of the signal acquisition optical fiber.

[0044] The integrated reference arm of the present invention combines a polarization regulator, an adjustable optical attenuator and an optical delay device with a simple and ingenious design, has high integration and is easy to maintain.

[0045] like Fig. 9 In the figure, the dotted line represents the optical path and the solid line represents the circuit. The present invention is connected with the host computer (PC) and other OCT components through the driving controller 1 and various interfaces to form a closed-loop system. The drift change of the optical signal in the system can be compensated in real time through the integrated reference arm, thereby improving the stability and availability of the OCT system.

Claims

1. An integrated reference arm for optical coherence tomography, characterized in that: The invention comprises a fiber coupler, a polarization regulator and an optical delay device, wherein the optical fiber connected to one port of the fiber coupler is wound around the polarization regulator for at least one circle and then connected to the optical delay device, the optical fiber is wound around the polarization regulator for fixing before and after the polarization regulator, the polarization regulator comprises a deflection adjustment motor and a deflection adjustment rocker arm, the deflection adjustment rocker arm is connected to the output shaft of the deflection adjustment motor through a crank, the optical fiber is wound around the deflection adjustment rocker arm for at least one circle, and fixing seats for fixing the optical fiber are arranged on both sides of the deflection adjustment rocker arm, the optical delay device comprises a collimator and a delay component, the optical fiber is a delay optical fiber and is connected to the collimation optical fiber end of the collimator. The delay component includes a sliding reflection angle cone and a fixed reflection angle cone, the sliding reflection angle cone is installed on a slider sliding along a linear slide rail, the light beam outlet of the collimator is toward the sliding reflection angle cone, the fixed reflection angle cone is installed between the sliding reflection angle cone and the collimator and is close to the collimator, the distance between the center line of the fixed reflection angle cone and the center line of the sliding reflection angle cone is equal to the distance between the center line of the fixed reflection angle cone and the center line of the collimator, and the center line of the fixed reflection angle cone, the center line of the sliding reflection angle cone, and the center line of the collimator are located in the same plane.

2. The integrated reference arm for optical coherence tomography according to claim 1, characterized in that: The slider is fixedly connected to the adjusting nut of the screw nut pair, and the adjusting screw of the screw nut pair is connected to the output shaft of the optical delay motor.

3. The integrated reference arm for optical coherence tomography according to claim 2, characterized in that: The integrated reference arm also includes an adjustable optical attenuator, which includes an attenuation motor and an attenuation plate. The attenuation plate is connected to the output shaft of the attenuation motor. The attenuation plate is an eccentrically arranged semicircular structure and is located in front of the collimator.

4. The integrated reference arm for optical coherence tomography according to claim 3, characterized in that: The center of the attenuation plate and the output shaft of the attenuation motor are eccentrically arranged along the straight edge of the attenuation plate, and the arc edge of the attenuation plate is located directly in front of the collimating mirror.

5. The integrated reference arm for optical coherence tomography according to claim 4, characterized in that: The integrated reference arm includes a closed shell, and the deflection adjustment motor, the fixed seat, the optical delay motor, the linear slide rail, the attenuation motor, the fiber coupler and the collimating mirror are all fixed on the bottom of the shell. The bottom of the shell is provided with a fiber positioning groove, and a drive controller for controlling the deflection adjustment motor, the optical delay motor and the attenuation motor is arranged inside the shell. A power interface and a USB interface connected to the drive controller are provided on the side wall of the shell.

6. The integrated reference arm for optical coherence tomography according to claim 5, characterized in that: The fiber coupler is a 2x2 fiber coupler, and the four ports of the fiber coupler are respectively an input end, a reference arm end, a sample arm end and an optical signal collection end. The delay fiber is connected to the reference arm end, the input end is connected to the input fiber, the sample arm end and the optical signal collection end are respectively connected to the sample fiber and the signal collection fiber, the sample fiber and the signal collection fiber extend from the fiber output port on the side wall of the shell, and the input fiber is connected to the fiber connector on the side wall of the shell.

7. The integrated reference arm for optical coherence tomography according to claim 6, characterized in that: One half of the optical fiber connector is located inside the housing and connected to the input optical fiber, and the other half is located outside the housing and connected to the light source optical fiber.

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