CN109297597A - A fixed-phase dual-channel spectral domain OCT device and method capable of eliminating OCT conjugate images - Google Patents

Abstract

OCT conjugation mirror image, which can be eliminated, the present invention relates to one kind determines difference two-way spectral coverage OCT device, including super-radiance light emitting diode, collimator, focusing objective len, the first beam splitter, the second beam splitter, third beam splitter, the 4th beam splitter, the first reflecting mirror, sample, the first spectrometer, the second spectrometer；The phase difference of interference signal of the present invention is stablized, and doubles in imaging depth while not reducing system imaging speed.

Description

A fixed-phase dual-channel spectral domain OCT device and method capable of eliminating OCT conjugate images

technical field

The present invention relates to a fixed-phase dual-channel spectral domain OCT device and method which can eliminate the conjugate image of OCT.

Background technique

The interference signal generated by the spectral domain optical coherence tomography system is the interference signal in the complex domain, with real and imaginary parts. However, the traditional spectral domain OCT spectrometer can only collect the real part information of the sample interference signal. Due to the lack of interference signal, frequency mixing will occur during fast Fourier transform, so that there are two images in the system imaging, that is, the real image and the conjugate mirror image. In the traditional method of removing the conjugate image, most of the phase shifting methods use the data acquisition card to control the voltage output to drive the piezoelectric ceramics for phase shifting. The accuracy and stability of the phase obtained by this method are greatly affected by the properties of piezoelectric ceramics, and at least two signals need to be collected at the same position, which affects the imaging speed and is not conducive to real-time imaging; 3×3 fiber coupler method The 3×3 fiber coupler is used to obtain two-phase interference signals. Although the interference signal with a fixed phase difference can also be obtained, the manufacture of the 3×3 fiber coupler is more complicated, and it is impossible to output two constants with equal interference intensities. phase difference interference signal.

SUMMARY OF THE INVENTION

In view of this, the purpose of the present invention is to provide a fixed-phase dual-channel spectral domain OCT device that can eliminate the conjugate mirror image of OCT, and can generate two interference signals with a phase difference of 90° at one time and use two spectrometers to collect the two interference signals synchronously. signal, and then combined with the two-phase deconjugate mirror method to remove the conjugate mirror.

To achieve the above object, the present invention adopts the following technical solutions:

A fixed-phase dual-channel spectral domain OCT device capable of eliminating the conjugate mirror image of OCT, comprising a superluminescent light-emitting diode, a collimator, a focusing objective lens, a first beam splitter, a second beam splitter, a third beam splitter, a third beam splitter, and a second beam splitter. A beam splitter, a first reflection mirror, a sample, a first spectrometer, and a second spectrometer; the light emitted by the superluminescent light-emitting diode is collimated into a beam of parallel light through a collimator; the parallel light is focused by a focusing objective lens, focusing After passing through the first beam splitter, it is divided into two beams of equal power, one beam is the sample beam and the other beam is the reference beam; the sample beam is directed towards the sample, and the reference beam is directed towards the first reflector; the backscattered light of the sample passes through The fourth beam splitter divides the A-port sample light and B-port sample light with the same power, and the light reflected by the first mirror is divided into the A-port reference light and the B-port reference light with the same power through the second beam splitter; When the optical path difference between the sample light and the reference light is within the coherent range of the light source and coincident at the first beam splitter, an interference signal is generated; when the optical path difference between the sample light and the reference light at port B is within the coherent range of the light source, and When the third beam splitter coincides, an interference signal is generated; the interference signal of port A is injected into the first spectrometer, and the interference signal of port B is injected into the second spectrometer.

Further, the device further includes a first collection mirror and a second collection mirror; the interference signal generated by the A port is introduced into the spectrometer through the first collection mirror; the interference signal generated by the B port is introduced into the spectrometer through the second collection mirror middle.

Further, the first spectrometer includes a first cylindrical lens, a first slit, a second cylindrical lens, a first reflecting mirror, a third cylindrical lens, a first reflective grating and a first line scan camera; The second spectrometer includes a sixth cylindrical lens, a second slit, a fifth cylindrical lens, a third reflecting mirror, a fourth cylindrical lens, a second reflective ruled diffraction grating and a second line array camera.

Further, the device further includes a host computer, the host computer controls the first line scan camera and the second line scan camera and controls the two line scan cameras to synchronously collect two interference signals with a phase difference of 90° of the sample.

Further, a control method for a fixed-phase dual-path spectral domain OCT device capable of eliminating the OCT conjugate mirror image is characterized in that, comprising the following steps:

Step S1: the light emitted by the superluminescent light-emitting diode is collimated into a parallel light through a collimator;

Step S2: the parallel light is focused through the focusing objective lens, and is divided into two beams of equal power through the first beam splitter after focusing, one beam is the sample light, and the other is the reference light; the sample light is directed towards the sample, and the reference light towards the first reflector;

Step S3: The backscattered light of the sample is divided into the sample light of port A and the sample light of port B with equal power through the fourth beam splitter, and the light reflected by the first mirror is divided into the reference of port A with equal power through the second beam splitter. light and reference light of port B; when the optical path difference of the sample light and reference light of port A is within the coherent range of the light source and coincident at the first beam splitter, an interference signal is generated; when the light of the sample light and reference light of port B is When the path difference is within the coherent range of the light source and coincides at the third beam splitter, an interference signal is generated;

Step S4: adjust the 3rd beam splitter and the 4th beam splitter so that the phase difference of the A port interference signal and the B port interference signal is 90°, and the A port interference signal is injected into the first spectrometer, and the B port interference signal is injected into to the second spectrometer;

Step S5: the interference signal enters the spectrometer, is expanded by the wavelength of the reflective grating diffraction grating and is captured by the line scan camera; the interference signal captured by the line scan camera is shown in formula (1):

Among them, DC is the direct current signal, AC is the self-coherent signal of each layer of the sample arm, is the intensity distribution function of the light source, and is the optical path length of the sample arm, is the optical path length of the reference arm, is the wave number;

Step S6: performing signal reconstruction on the interference signals of different phases captured by the first line scan camera and the second line scan camera to obtain the interference signals in the complex domain;

Step S7: Fourier transform is performed on the interference signal in the complex domain, and the conjugate mirror image is removed to obtain the depth information of the sample.

Further, the step S6 is specifically:

Step S61: Simplify formula (1) into formula (4)

(4)

in, is the combined phase of the interference signals of each reflection layer, is the phase difference of the interference signal between port A and port B;

Step S62: The formula expression of the interference signal captured by the line scan camera at port A is shown in formula (5):

(5)

The formula of the interference signal captured by the line scan camera at port B is shown in formula (6):

(6)

After collecting the DC signal of the reference arm and the sample arm, after deducting the DC signal, formulas (5) and (6) can be expressed as:

(7)

By formula (6), the intensity and phase of the interference signal at each wavelength are calculated:

(8)

(9)

Step S43: The reconstructed interference signal is expressed as:

(10).

Compared with the prior art, the present invention has the following beneficial effects:

The invention can obtain two interference signals with a phase difference of 90° without a phase shifter, the phase difference of the interference signals is not affected by the performance of the phase shifter, and the anti-interference ability is strong. The interference information will not reduce the imaging speed of the system.

Description of drawings

Fig. 1 is the structural principle diagram of the present invention;

Fig. 2 is a port A interference spectrum and FFT result diagram in an embodiment of the present invention;

Fig. 3 is the interference spectrum and FFT result diagram of B port in one embodiment of the present invention;

4 is a graph of the real part and the imaginary part of the reconstructed interference signal according to an embodiment of the present invention;

5 is a diagram of an FFT result of the reconstructed interference signal according to an embodiment of the present invention;

In the figure: 1- superluminescent light-emitting diode, 2- collimator, 3- focusing objective lens, 4- first beam splitter, 5- first collecting lens, 6- first cylindrical lens, 7- first slit, 8- The second cylindrical lens, 9- The first reflecting mirror, 10- The third cylindrical lens, 11- The first line scan camera, 12- The first reflective grating diffraction grating, 13- The second beam splitter, 14- The second reflector, 15-host computer, 16-second line scan camera, 17-fourth cylindrical lens, 18-second reflective grating diffraction grating, 19-third reflector, 20-fifth cylindrical lens, 21 - second slit, 22 - sixth cylindrical lens, 23 - second acquisition lens, 24 - third beam splitter, 25 - sample, 26 - fourth beam splitter.

Detailed ways

The present invention will be further described below with reference to the accompanying drawings and embodiments.

Please refer to FIG. 1 , the present invention provides a fixed-phase dual spectral domain OCT device capable of eliminating the conjugate mirror image of OCT, comprising a superluminescent light-emitting diode 1, a collimator 2, a focusing objective lens 3, a first beam splitter 4, a first The second beam splitter 13, the third beam splitter 24, the fourth beam splitter 26, the first mirror 9, the sample 25, the first spectrometer, and the second spectrometer; the light emitted by the superluminescent diode 1 is collimated The device 2 is collimated into a beam of parallel light; the parallel light is focused by the focusing objective lens 3, and then divided into two beams of equal power by the first beam splitter 4 after focusing, one beam is the sample beam, and the other beam is the reference beam. The light is directed to the sample 25, and the reference light is directed to the first mirror 9; the backscattered light of the sample 25 is divided into the sample light of port A and the sample light of port B with equal power through the fourth beam splitter 26, and the first mirror 9 reflects The returned light passes through the second beam splitter 13 and is divided into A port reference light and B port reference light with equal power; when the optical path difference between the A port sample light and the reference light is within the coherent range of the light source and is within the The interference signal is generated when the 4 places overlap; the interference signal is generated when the optical path difference between the sample light and the reference light at port B is within the coherent range of the light source and coincides at the third beam splitter 24; the interference signal at port A is injected into the first Spectrometer, the B port interference signal is injected into the second spectrometer.

In an embodiment of the present invention, the device further includes a first acquisition mirror 5 and a second acquisition mirror 23; the interference signal generated by the A port is introduced into the spectrometer through the first acquisition mirror 5; the interference generated by the B port The signal is introduced into the spectrometer via the second acquisition mirror 23 .

In an embodiment of the present invention, the first spectrometer includes a first cylindrical lens 6, a first slit 7, a second cylindrical lens 8, a first reflecting mirror 9, a third cylindrical lens 10, and a first reflective reticle Diffraction grating 12 and first line scan camera 11; the second spectrometer includes a sixth cylindrical lens 22, a second slit 21, a fifth cylindrical lens 20, a third reflecting mirror 19, a fourth cylindrical lens 17, a second reflecting mirror A type-ruled diffraction grating 18 and a second line scan camera 16 are provided.

In an embodiment of the present invention, the device further includes a host computer 15, the host computer 15 is connected to the first line scan camera 11 and the second line scan camera 16, and controls the two line scan cameras to synchronously collect the two phase differences of the sample is the 90° interference signal.

In an embodiment of the present invention, a method for controlling a phase-fixed dual-channel spectral domain OCT device capable of eliminating the conjugate mirror image of the OCT is characterized in that, it includes the following steps:

Step S1: the light emitted by the superluminescent light-emitting diode 1 is collimated into a parallel light through the collimator 2;

Step S2: the parallel light is focused through the focusing objective lens 3, and is divided into two beams of equal power through the first beam splitter 4 after focusing, one beam is the sample light, and the other is the reference light; the sample light is directed to the sample 25 , the reference light is directed to the first mirror 9;

Step S3: the backscattered light of the sample 25 is divided into the A port sample light and the B port sample light with equal power through the fourth beam splitter 26, and the light reflected by the first reflector 9 is divided into the same power through the second beam splitter. The reference light of port A and the reference light of port B; when the optical path difference of the sample light of port A and the reference light is within the coherent range of the light source and coincident at the first beam splitter 4, an interference signal is generated; when the sample light of port B and the When the optical path difference of the reference light is within the coherent range of the light source and coincides at the third beam splitter 24, an interference signal is generated;

Step S4: adjust the 3rd beam splitter 24 and the 4th beam splitter 26 so that the phase difference of the A mouth interference signal and the B mouth interference signal is 90 °, and the A mouth interference signal is injected into the first spectrometer, the B mouth interference signal into the second spectrometer;

Step S5: the interference signal enters the spectrometer, is expanded by the wavelength of the reflective grating diffraction grating and is captured by the line scan camera; the interference signal captured by the line scan camera is shown in formula (1):

Among them, DC is the direct current signal, AC is the self-coherent signal of each layer of the sample arm, is the intensity distribution function of the light source, and is the optical path length of the sample arm, is the optical path length of the reference arm, is the wave number;

Step S6: performing signal reconstruction on the interference signals of different phases captured by the first line scan camera and the second line scan camera to obtain the interference signals in the complex domain;

Step S7: Fourier transform is performed on the interference signal in the complex domain, and the conjugate mirror image is removed to obtain the depth information of the sample.

In an embodiment of the present invention, the step S6 is specifically:

Step S61: Simplify formula (1) into formula (4)

(4)

in, is the combined phase of the interference signals of each reflection layer, is the phase difference of the interference signal between port A and port B;

Step S62: The formula expression of the interference signal captured by the line scan camera at port A is shown in formula (5):

(5)

The formula of the interference signal captured by the line scan camera at port B is shown in formula (6):

(6)

After collecting the DC signal of the reference arm and the sample arm, after deducting the DC signal, formulas (5) and (6) can be expressed as:

(7)

By formula (6), the intensity and phase of the interference signal at each wavelength are calculated:

(8)

(9)

Step S43: The reconstructed interference signal is expressed as:

(10).

The above descriptions are only preferred embodiments of the present invention, and all equivalent changes and modifications made according to the scope of the patent application of the present invention shall fall within the scope of the present invention.

Claims (6)

1. A phasing difference double-path spectral domain OCT device capable of eliminating OCT conjugate mirror images is characterized in that: the device comprises a superluminescent light-emitting diode, a collimator, a focusing objective lens, a first beam splitter, a second beam splitter, a third beam splitter, a fourth beam splitter, a first reflector, a sample, a first spectrometer and a second spectrometer; the light emitted by the superluminescent light-emitting diode is collimated into a beam of parallel light by the collimator; the parallel light is focused through a focusing objective lens, and is divided into two beams of light with equal power through a first beam splitter after being focused, wherein one beam of light is sample light, and the other beam of light is reference light; the sample light is emitted to the sample, and the reference light is emitted to the first reflector; the back scattering light of the sample is divided into a port A sample light and a port B sample light with equal power through a fourth beam splitter, and the light reflected by the first reflector is divided into a port A reference light and a port B reference light with equal power through a second beam splitter; when the optical path difference of the port A sample light and the reference light is within the coherent range of the light source and is superposed at the first beam splitter, an interference signal is generated; when the optical path difference of the sample light at the port B and the reference light is within the coherent range of the light source and is superposed at the third beam splitter, an interference signal is generated; the interference signal of the port A is transmitted to the first spectrometer, and the interference signal of the port B is transmitted to the second spectrometer.

2. The apparatus of claim 1, wherein the apparatus comprises a dual-spectral-domain OCT apparatus with a phased difference capable of eliminating OCT conjugate mirror images, and further comprises: the device also comprises a first collecting mirror and a second collecting mirror; the interference signal generated by the port A is introduced into the spectrometer through the first collecting mirror; and an interference signal generated by the port B is introduced into the spectrometer through the second collecting mirror.

3. The apparatus of claim 1, wherein the apparatus comprises a dual-spectral-domain OCT apparatus with a phased difference capable of eliminating OCT conjugate mirror images, and further comprises: the first spectrometer comprises a first cylindrical lens, a first slit, a second cylindrical lens, a first reflector, a third cylindrical lens, a first reflective reticle diffraction grating and a first linear array camera; the second spectrometer comprises a sixth cylindrical lens, a second slit, a fifth cylindrical lens, a third reflector, a fourth cylindrical lens, a second reflective reticle diffraction grating and a second linear array camera.

4. The apparatus of claim 3, wherein the apparatus comprises a dual-spectral-domain OCT apparatus with a phased difference for eliminating OCT conjugate mirror image: the device also comprises an upper computer, the first linear array camera and the second linear array camera control the two linear array cameras to synchronously acquire two interference signals of which the phase difference is 90 degrees of the samples.

5. The control method of the two-way spectrum domain OCT device capable of eliminating the phasing difference of the OCT conjugate mirror image according to claim 4, is characterized by comprising the following steps:

step S1, collimating the light emitted by the superluminescent diode into a beam of parallel light by a collimator;

step S2, the parallel light is focused through a focusing objective lens, and is divided into two beams of light with equal power through a first beam splitter after being focused, wherein one beam of light is sample light, and the other beam of light is reference light; the sample light is emitted to the sample, and the reference light is emitted to the first reflector;

step S3, back scattering light of the sample is divided into A port sample light and B port sample light with equal power through a fourth beam splitter, and light reflected by the first reflector is divided into A port reference light and B port reference light with equal power through a second beam splitter; when the optical path difference of the port A sample light and the reference light is within the coherent range of the light source and is superposed at the first beam splitter, an interference signal is generated; when the optical path difference of the sample light at the port B and the reference light is within the coherent range of the light source and is superposed at the third beam splitter, an interference signal is generated;

step S4, adjusting the third beam splitter and the fourth beam splitter to enable the phase difference between the interference signal of the port A and the interference signal of the port B to be 90 degrees, and transmitting the interference signal of the port A into the first spectrometer and the interference signal of the port B into the second spectrometer;

step S5, the interference signal enters into the spectrometer, is expanded according to the wavelength by the reflection type reticle diffraction grating and is captured by the linear array camera; interference signals captured by the line camera are as shown in formula (1):

wherein DC is a direct current signal, AC is an autocorrelation signal of each layer of the sample arm,is a function of the light intensity distribution of the light source,andis the optical path of the sample arm,is the optical path of the reference arm,is the wave number;

s6, carrying out signal reconstruction on interference signals with different phases captured by the first linear-array camera and the second linear-array camera to obtain interference signals of a complex field;

step S7: and carrying out Fourier transform on the interference signal of the complex field, removing the conjugate mirror image and obtaining the depth information of the sample.

6. The control method of the dual-spectral-domain OCT device capable of eliminating the phasing difference of the OCT conjugate mirror image according to claim 5, wherein: the step S6 specifically includes:

step S61, simplifying the formula (1) into a formula (4)

（4）

wherein ,for the combined phase of the interference signals of each reflective layer,the phase difference of interference signals of the port A and the port B is obtained;

step S62: the formula of the interference signal captured by the linear array camera with the port A is expressed as the following formula (5):

（5）

the formula of the interference signal captured by the line-scan camera of port B is shown in formula (6):

（6）

after taking the dc of the reference arm and the sample arm and deducting the dc signal, equations (5) and (6) can be expressed as:

（7）

the intensity and phase of the interference signal at each wavelength are calculated by equation (6):

（8）

（9）

step S43: the reconstructed interference signal is expressed as:

（10）。