TWI872389B - Wavelength-swept laser light source system with signal shaping - Google Patents

Abstract

A wavelength-swept laser light source system with signal shaping, includes an optical fiber Fabry-Perot turnable filter, a beam wavelength controller, a first isolator, a laser beam amplifier, a signal shaper, a beam splitter and a second Isolator. The optical fiber Fabry-Perot turnable filter receives a voltage signal to filter a received broad-spectrum beam and output a beam with a specific wavelength. The beam wavelength controller outputs the voltage signal to the optical fiber Fabry-Perot turnable filter according to a predetermined parameter. The laser beam amplifier is provided for initially emitting the broad-spectrum beam, and continuing to amplify the beam of the specific wavelength until it becomes a main beam. The signal shaper is provided for performing a half-cycle filtering on the broad-spectrum beam and the beam of the specific wavelength according to the waveform shaping parameters, and the waveform shaping parameters have different gain values.

Description

Sweep laser source system with signal shaping

A scanning laser, in particular a scanning laser light source system with signal shaping that can adjust and optimize the authenticity of three-dimensional information of an object to be observed.

Optical coherence tomography (OCT), also known as optical coherence analysis and optical coherence tomography, is an imaging technology for acquiring and processing optical signals. It uses low-coherence light (such as near-infrared light) to scan and capture two-dimensional and three-dimensional images with micron-level resolution from inside optical scattering media (such as biological tissues); it is used in medical imaging and industrial non-destructive testing. Optical coherence tomography uses the principle of light interference and usually selects near-infrared light with a longer wavelength to take pictures, which can penetrate a certain depth of the scanning medium. Another similar technology, confocal microscopy, does not penetrate the sample as deeply as optical coherence tomography. The light sources used in optical coherence tomography include superluminescent diodes and ultrashort pulse lasers. Depending on the nature of the light source, this scanning method can even achieve sub-micron resolution, which requires the light source to have a very wide spectrum, with a wavelength variation range of about 100 nanometers.

OCT is an optical interference imaging technology, which is very similar to the Michelson Interferometer commonly used in many engineering projects. It is composed of a light source, a reference optical path, a measurement optical path and a screen. The biggest difference between OCT and Michelson Interferometer is the choice of light source: Michelson Interferometer usually uses laser light source, which can be coherent over a long distance, usually up to several meters. However, OCT usually uses special low-coherence light sources to illuminate samples, such as light-emitting diodes (LEDs) or superluminescent diodes (SLDs). It is precisely because of the difference in coherence characteristics that OCT has the ability of cross-sectional perspective. The optical interference image signal produced by the scanning laser light source used in OCT currently still has some shortcomings, such as side peaks, which affect the restoration and observation of the authenticity of the object to be tested.

Therefore, how to solve the above problems and deficiencies of the existing technology is an urgent research topic for relevant industries.

The present invention provides a sweeping laser light source system with signal shaping, which is used to be connected to an interferometer module and the interferometer module is connected to a balance detector, wherein the balance detector outputs an optical interference waveform signal. The sweeping laser light source system with signal shaping includes an optical fiber Fabry-Perot tunable filter, a beam wavelength controller, a first isolator, a laser beam amplifier, a signal shaper, a beam splitter and a second isolator. The optical fiber Fabry-Perot tunable filter is used to receive a voltage signal to filter a received wide-spectrum beam and output a specific wavelength beam, wherein the voltage signal determines the wavelength range of the specific wavelength beam. A beam wavelength controller is connected to the optical fiber Fabry-Perot tunable filter, and the beam wavelength controller is used to output the voltage signal to the optical fiber Fabry-Perot tunable filter according to a preset parameter, wherein the preset parameter determines the voltage value of the voltage signal. A first isolator is connected to the output end of the optical fiber Fabry-Perot tunable filter to receive the specific wavelength beam, and the first isolator is used to output the specific wavelength beam in a single direction. A laser beam amplifier is connected to the output end of the first isolator, and the laser beam amplifier is used to initially emit the broadband beam and continuously amplify the specific wavelength beam until the specific wavelength beam becomes the main beam, wherein the broadband beam cannot pass through the first isolator in the reverse direction. A signal shaper is connected to the laser beam amplifier, and the signal shaper is used to perform half-cycle filtering on the wide-spectrum light beam and the specific wavelength light beam according to a waveform shaping parameter, wherein the waveform shaping parameter has different gain values. A beam splitter, whose input end is connected to the laser beam amplifier, and whose first output end is connected to an interferometer module. A second isolator is connected to the second output end of the beam splitter and the input end of the optical fiber Fabry-Perot tunable filter, and the second isolator is used to output the specific wavelength light beam and the wide-spectrum light beam in a single direction.

In one embodiment of the present invention, the signal shaper performs signal shaping on the broadband light beam and the specific wavelength light beam according to different gain values.

In one embodiment of the present invention, the balance detector is connected to an operation processor, which is used to perform Fourier transformation on the optical interference waveform signal to obtain a three-dimensional information waveform signal.

In one embodiment of the present invention, after the signal shaper performs half-cycle filtering on the broadband light beam and performs signal shaping on the broadband light beam according to different gain values, the optical interference waveform signal is also half-cycle filtered and signal shaped so that both sides of the peak of the three-dimensional information waveform signal are converted to be flat and symmetrical.

In one embodiment of the present invention, the beam splitter splits the light beam of the specific wavelength in a one-to-one light intensity ratio.

In summary, the sweeping laser light source system with signal shaping disclosed in the present invention can achieve the following effects: 1.        Obtain better optical interference waveform signal waveform and three-dimensional information waveform signal by performing half-cycle filtering and signal waveform adjustment on the specific wavelength beam of the wide-spectrum beam; and 2.        Adjust the three-dimensional information authenticity of the object to be observed simply by adjusting the gain value.

The following detailed description is based on specific embodiments to make it easier to understand the purpose, technical content, features and effects of the present invention.

In order to solve the problem of insufficient authenticity of the objects to be inspected under existing three-dimensional tomography scanning, the inventor has improved the shortcomings of existing products after years of research and development. The following will introduce in detail how the invention uses a scanning laser light source system with signal shaping to achieve the most efficient functional requirements.

Please refer to the first and second figures. The first figure is a block diagram of the sweeping laser light source system with signal shaping of the present invention. The second figure is a block diagram of the sweeping laser light source system with signal shaping of the present invention applied to an interferometer system. As shown in the figure, the sweeping laser light source system with signal shaping 100 is connected to the interferometer module 200 and the interferometer module 200 is connected to a balance detector 300, wherein the balance detector 300 outputs an optical interference waveform signal LS, and the balance detector 300 is connected to an operation processor 400, so that the operation processor 400 further processes and operates the optical interference waveform signal LS. In frequency domain optical coherence tomography, the signal of broadband interference is obtained by frequency domain separation detectors. The separation can be achieved by using variable frequency light source to time encode the frequency at different times or using dispersion detectors such as gratings and linear detector arrays. According to the Wiener-Schinchen theorem in Fourier transform, the autocorrelation function of the signal and its power spectrum density are Fourier transform pairs, so the depth scan can be obtained immediately by Fourier transforming the obtained spectrum. In addition, a loop is formed inside the sweeping laser light source system 100 with signal shaping, and a beam splitter is used to split the light beam in the loop to the interferometer module 200 to perform optical interference effect.

Next, the relevant details of the swept-frequency laser light source system 100 with signal shaping will be further described.

Please refer to Figures 1 to 5B simultaneously. Figure 3A is a schematic diagram of the ideal low-pass waveform of the signal shaper of the present invention. Figure 3B is another schematic diagram of the ideal low-pass waveform of the signal shaper of the present invention. Figure 3C is a schematic diagram of the actual low-pass waveform of the signal shaper of the present invention. Figure 4A is a schematic diagram of the optical interference waveform signal without signal shaping of the present invention. Figure 4A is a schematic diagram of the optical interference waveform signal without signal shaping of the present invention under the prior art. Figure 4B is a schematic diagram of the three-dimensional information waveform signal without signal shaping of the present invention under the prior art. Figure 5A is a schematic diagram of the optical interference waveform signal processed by the sweeping laser light source system with signal shaping of the present invention. 5B is a schematic diagram of a three-dimensional information waveform signal processed by the swept-frequency laser light source system with signal shaping of the present invention. The swept-frequency laser light source system with signal shaping 100 includes an optical fiber Fabry-Perot tunable filter 110, a beam wavelength controller 120, a first isolator 130, a laser beam amplifier 140, a signal shaper 150, a beam splitter 160 and a second isolator 170. The optical fiber Fabry-Perot tunable filter 110 is used to receive a voltage signal VS to filter a received wide-spectrum light beam WS and output a specific wavelength light beam AS, wherein the voltage signal VS determines the wavelength range of the specific wavelength light beam AS, and the specific wavelength light beam AS refers to a light beam within a certain wavelength range. The beam wavelength controller 120 is connected to the optical fiber Fabry-Perot tunable filter 110. The beam wavelength controller 120 is used to output a voltage signal VS to the optical fiber Fabry-Perot tunable filter 110 according to a preset parameter, wherein the preset parameter determines the voltage value of the voltage signal VS. The first isolator 130 is connected to the output end of the optical fiber Fabry-Perot tunable filter 110 to receive a specific wavelength beam AS. The first isolator 130 is used to output a specific wavelength beam AS in a single direction. The laser beam amplifier 140 is connected to the output end of the first isolator 130 to receive the specific wavelength beam AS. The laser beam amplifier 140 is used to initially emit the broadband beam WS and continuously amplify the specific wavelength beam AS filtered by the optical fiber Fabry-Perot tunable filter 110 until the specific wavelength beam AS becomes the main beam in the loop, wherein the broadband beam WS cannot pass through the first isolator 130 in the reverse direction. The signal shaper 150 is connected to the laser beam amplifier 140. The input end of the beam splitter 160 is connected to the laser beam amplifier 140, and the first output end and the second output end of the beam splitter 160 are respectively connected to an interferometer module 200 and a second isolator 170, wherein the beam splitter 160 splits the specific wavelength beam AS as the main beam in the loop in a one-to-one light quantity ratio. The second isolator 170 is connected to the second output end of the beam splitter 160 and the input end of the optical fiber Fabry-Perot tunable filter 110, and the second isolator 170 is used to output the specific wavelength beam AS and the wide-spectrum beam WS in a unidirectional manner, wherein the function of the second isolator 170 is the same as that of the first isolator 130, allowing the beam to pass only in one direction.

It should be noted that the signal shaper 150 of the present invention is used to perform half-cycle filtering on the wide-spectrum light beam WS and the specific wavelength light beam AS according to a waveform shaping parameter, wherein the waveform shaping parameter has different gain values, wherein the gain value of the waveform shaping parameter can be set by the designer according to actual conditions to meet various actual requirements. The signal shaper 150 performs signal shaping on the wide-spectrum light beam WS and the specific wavelength light beam AS according to different gain values to make the signal waveform closer to or equivalent to the authenticity of the three-dimensional information of the object to be observed. After the signal shaper 150 performs half-cycle filtering on the wide-spectrum light beam WS and performs signal shaping on the wide-spectrum light beam WS according to different gain values, the rear-end optical interference waveform signal LS will also be half-cycle filtered and signal shaped to convert the two sides of the peak of the three-dimensional information waveform signal TS into flat and symmetrical ones.

Further, as shown in FIG. 3A and FIG. 3B, it is an ideal signal shaper 150 filter waveform and the gain value is the same, the wide-spectrum light beam WS and the specific wavelength light beam AS will be filtered in half a cycle, but the signal waveform cannot be reshaped. At this time, the first half cycle or the second half cycle can be selected. In order to improve the side peak effect, the signal shaper 150 filter waveform shown in FIG. 3C will be used. The wide-spectrum light beam WS and the specific wavelength light beam AS can be signal shaped according to different gain values to make the half-cycle optical interference waveform signal LS more perfect, so that the optical interference waveform signal LS can be sent to the operation processor 400 for Fourier transformation to improve the side peak effect, so that the signal waveform is closer to or equivalent to the truth. Therefore, according to the above description, the optical interference waveform signal of the prior art of FIG. 4A will become the optical interference waveform signal LS of FIG. 5A after being processed by the sweeping laser light source system 100 with signal shaping of the present invention; the three-dimensional information waveform signal of the prior art of FIG. 4B will become the three-dimensional information waveform signal TS of FIG. 5B after being processed by the sweeping laser light source system 100 with signal shaping of the present invention.

Comparing Figure 4A with Figure 5A, it can be seen that in each cycle of the optical interference waveform signal LS of Figure 5A, only the first half has a waveform signal, while the second half has no waveform signal, and the curvature at the side peak has also been optimized and deformed. Next, comparing Figure 4B with Figure 5B, it can be seen that the side peak of the three-dimensional information waveform signal TS is different from the three-dimensional information waveform signal under the previous technology. The side peak of the three-dimensional information waveform signal under the previous technology of Figure 4B is slightly higher, which will affect the authenticity of the three-dimensional information of the object to be observed. However, the side peak of the three-dimensional information waveform signal TS of Figure 5B has been eliminated to zero, so it can more completely present the authenticity of the three-dimensional information of the object to be observed.

In summary, the sweeping laser light source system with signal shaping disclosed in the present invention can achieve the following effects: 1.        Obtain better optical interference waveform signal waveform and three-dimensional information waveform signal by performing half-cycle filtering and signal waveform adjustment on the specific wavelength beam of the wide-spectrum beam; and 2.        Optimize the three-dimensional information authenticity of the object to be observed simply by adjusting the gain value.

However, the above is only the preferred embodiment of the present invention and is not intended to limit the scope of the present invention. Therefore, all equivalent changes or modifications based on the features and spirit described in the scope of the present invention should be included in the scope of the patent application of the present invention.

100: Sweep laser light source system with signal shaping 110: Fiber Fabry-Perot tunable filter 120: Beam wavelength controller 130: First isolator 140: Laser beam amplifier 150: Signal shaper 160: Beam splitter 170: Second isolator 200: Interferometer module 300: Balance detector 400: Calculation processor LS: Optical interference waveform signal TS: Three-dimensional information waveform signal VS: Voltage signal WS: Broadband spectrum beam AS: Specific wavelength beam

The first figure is a block diagram of the sweeping laser light source system with signal shaping of the present invention. The second figure is a block diagram of the sweeping laser light source system with signal shaping of the present invention applied to the interferometer system. The third figure A is a schematic diagram of the ideal low-pass waveform of the signal shaper of the present invention. The third figure B is another schematic diagram of the ideal low-pass waveform of the signal shaper of the present invention. The third figure C is a schematic diagram of the actual low-pass waveform of the signal shaper of the present invention. The fourth figure A is a schematic diagram of the optical interference waveform signal without signal shaping of the present invention under the prior art. The fourth figure B is a schematic diagram of the three-dimensional information waveform signal without signal shaping of the present invention under the prior art. Figure 5A is a schematic diagram of an optical interference waveform signal processed by the sweeping laser light source system with signal shaping of the present invention. Figure 5B is a schematic diagram of a three-dimensional information waveform signal processed by the sweeping laser light source system with signal shaping of the present invention.

100: Sweep laser light source system with signal shaping

110: Fiber Optic Fabry-Perot Tunable Filter

120: Beam wavelength controller

130: First isolator

140: Laser beam amplifier

150:Signal Shaper

160: Beam splitter

170: Second isolator

200: Interferometer module

300:Balance detector

400: Computing processor

LS: Optical interference waveform signal

TS: Three-dimensional information waveform signal

VS: voltage signal

WS: Wide spectrum beam

AS: Specific wavelength beam

Claims (2)

A sweeping laser light source system with signal shaping is used to be connected to an interferometer module and the interferometer module is connected to a balance detector, wherein the balance detector outputs an optical interference waveform signal. The sweeping laser light source system with signal shaping includes: an optical fiber Fabry-Perot tunable filter, which is used to receive a voltage signal to filter a received wide-spectrum light beam and output a specific wavelength light beam, wherein the voltage signal determines the wavelength range of the specific wavelength light beam; a beam wavelength controller, which is connected to the optical fiber Fabry-Perot tunable filter, The beam wavelength controller is used to output the voltage signal to the optical fiber Fabry-Perot tunable filter according to a preset parameter, wherein the preset parameter determines the voltage value of the voltage signal; a first isolator is connected to the output end of the optical fiber Fabry-Perot tunable filter to receive the specific wavelength beam, and the first isolator is used to output the specific wavelength beam in a single direction; a laser beam amplifier is connected to the output end of the first isolator, and the laser beam amplifier is used to initially emit the wide-spectrum beam and continuously amplify the specific wavelength beam until the specific wavelength The invention relates to a first isolator, wherein the broadband light beam becomes the main light beam, wherein the broadband light beam cannot pass through the first isolator in the reverse direction; a signal shaper, which is connected to the laser beam amplifier, and the signal shaper is used to perform half-cycle filtering on the broadband light beam and the specific wavelength light beam according to a waveform shaping parameter, wherein the waveform shaping parameter has different gain values; a beam splitter, whose input end is connected to the laser beam amplifier and whose first output end is connected to the interferometer module; and a second isolator, which is connected to the second output end of the beam splitter and the optical fiber Fabry-Perot tunable filter. At the input end, the second isolator is used to output the specific wavelength beam and the broadband beam in one direction, wherein the balance detector is connected to an operation processor, and the operation processor is used to perform Fourier transformation on the optical interference waveform signal to obtain a three-dimensional information waveform signal, wherein after the signal shaper performs half-cycle filtering on the broadband beam and performs signal shaping on the broadband beam according to different gain values, the optical interference waveform signal will also be half-cycle filtered and signal shaped, so that the two sides of the peak of the three-dimensional information waveform signal are converted to be flat and symmetrical. A sweeping laser light source system with signal shaping as described in claim 1, wherein the beam splitter splits the specific wavelength light beam in a one-to-one ratio of light intensity.

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