An ultrafast tomography system for curved transparent objects

Abstract

The present invention provides an ultrafast tomography system for a curved transparent object, wherein a dispersion medium converts a laser signal into a series of light pulses, one of which is sent to an imaging device as a detection light, and the other is sent to a third coupler as a reference light through an adjustable delay medium; the imaging device performs point scanning on the curved transparent object, and the light pulse passing through the curved transparent object is transmitted to the second coupler; the second coupler transmits one of the received light pulses to a processing device so that the processing device obtains the detection optical path of the light pulse, and the other is transmitted to the third coupler; the processing device determines the delay adjustment amount of the adjustable delay medium for the light pulse of the wavelength according to the wavelength and the detection optical path of the light pulse, so that the reference light input to the third coupler and the detection light are coupled to generate an interference light signal with the maximum light intensity; the processing device analyzes the thickness at the corresponding position of the curved transparent object based on the corresponding interference electrical signal, thereby improving the tomography speed of the sample thickness by point scanning imaging.

Description

Technical Field

[0001] The invention belongs to the field of ultrafast imaging, and in particular relates to an ultrafast tomography system for curved transparent objects. Background Art

[0002] At present, there are three main imaging technologies: the first is to use one-dimensional diffraction devices such as prisms and gratings to diffract ultrafast lasers in one dimension, thereby performing line scanning on the sample; the second is to use a combination of gratings and virtual phase arrays to diffract ultrafast lasers in two dimensions, thereby performing surface scanning on the sample; the third is to focus the light pulses to a point and incident them on the corresponding position of the sample, thereby performing point scanning on the sample. Although the first two imaging technologies belong to ultrafast imaging technologies, they can only be used to image the appearance and contour of the sample; and although the third point scanning has a slow scanning speed, it has a certain tomographic imaging capability (using time-stretched optical coherence tomography OCT technology). Specifically, the reflected light returned from the corresponding position of the sample will interfere with the reference light, and the point scanning can determine the thickness information of the sample based on the change in the interference free spectral range FSR. It can be seen that the existing imaging technology has a slow speed when performing tomography of sample thickness through point scanning. Summary of the invention

[0003] The invention provides an ultrafast tomography system for curved transparent objects, so as to solve the problem that the current imaging technology has a slow speed when performing tomography on sample thickness through point scanning.

[0004] According to a first aspect of an embodiment of the present invention, there is provided an ultrafast tomography system for a curved transparent object, comprising: a laser generating device for generating a laser signal;

[0005] A dispersive medium, used for performing time-domain stretching on the laser signal to form a series of periodically occurring optical pulses;

[0006] A first coupler is used to split the series of optical pulses into two paths, one path is sent as detection light to an imaging device, and the other path is sent as reference light to a third coupler through an adjustable delay medium;

[0007] The imaging device is used to sequentially irradiate light pulses of different wavelengths in the series of light pulses onto the same position on the curved transparent object, and the light pulses of different wavelengths are transmitted to the second coupler after passing through the curved transparent object;

[0008] The second coupler is used to divide the received optical pulse into two paths, one path is transmitted to the detector, and the other path is transmitted to the third coupler; the detector converts the optical pulse received from the second coupler into an optical path electrical signal; the signal collector collects the optical path electrical signal and sends it to the processing device;

[0009] The processing device determines the detection optical path of the optical pulse of the corresponding wavelength according to the time when the optical path electrical signal is received for each optical path electrical signal of different wavelengths, and determines the reference optical path of the optical pulse of the wavelength according to the wavelength of the optical pulse and the detection optical path determined this time, so as to determine the delay adjustment amount of the adjustable delay medium for the optical pulse of the wavelength; the adjustable delay medium performs delay processing on the optical pulse of the wavelength according to the delay adjustment amount, so as to adjust the optical path difference between the reference light and the detection light of the same wavelength input to the third coupler;

[0010] The third coupler couples the reference light and the detection light with the same wavelength received by it to generate an interference light signal with the maximum light intensity; the detector converts the interference light signal into an interference electrical signal; the signal collector collects the interference electrical signal and sends it to the processing device;

[0011] The processing device analyzes the thickness of the curved transparent object at a corresponding position based on the interference electrical signal.

[0012] In an optional implementation, the output end of the laser generating device is connected to the input end of the first coupler through a dispersive medium, the first output end of the first coupler is connected to the first end of the circulator, and the second output end is connected to the first input end of the third coupler through the adjustable delay medium; the second end and the third end of the circulator are respectively connected to the input end of the imaging device and the second coupler, a curved transparent object is provided below the imaging device, the two output ends of the second coupler are respectively connected to the second input end of the third coupler and the second input end of the detector, the output end of the third coupler is connected to the first input end of the detector, the output end of the detector is connected to the processing device through a signal collector, and the processing device is connected to the adjustable delay medium.

[0013] In another optional implementation, before determining the reference optical path of the wavelength light pulse according to the wavelength of the light pulse and the detection optical path determined this time, the processing device further determines whether the currently received optical path electrical signal corresponds to the first light pulse output from the same position of the curved transparent object, and if so, determines the reference optical path of the wavelength light pulse according to the wavelength of the light pulse and the detection optical path determined this time;

[0014] Otherwise, the reference optical path of the optical pulse of the wavelength is determined according to the wavelength of the optical pulse, the detection optical path determined this time, and the detection optical path corresponding to the previous optical pulse with the closest wavelength.

[0015] In another optional implementation, the processing device locally pre-stores a set of corresponding relationships between detection optical paths and reference optical paths respectively set for each wavelength, and each set contains a plurality of corresponding relationships between detection optical paths and reference optical paths;

[0016] When the processing device determines the reference optical path of the wavelength optical pulse based on the wavelength of the optical pulse and the detection optical path determined this time, it first searches for a set corresponding to the wavelength of the optical pulse locally, compares and searches for the detection optical path determined this time in the set, and then determines the reference optical path corresponding to the detection optical path determined this time.

[0017] In another optional implementation, in the series of light pulses within a period, the wavelengths of the light pulses are different and the light pulses are arranged in chronological order according to the size of the wavelengths; when light pulses of different wavelengths are incident on the same position, the size of the detection optical path changes regularly as the size of the wavelength of the light pulse changes; the corresponding relationship between the detection optical path and the reference optical path in the set is arranged in the order of the size of the detection optical path;

[0018] When determining the reference optical path of the light pulse of the wavelength according to the wavelength of the light pulse, the detection optical path determined this time and the detection optical path corresponding to the light pulse that was closest to the wavelength last time, the processing device first searches out a set corresponding to the wavelength of the light pulse locally, and then locates the detection optical path corresponding to the light pulse that was closest to the wavelength last time in the set in order, and starting from the located position, according to the wavelength size of the last light pulse and the current light pulse, and in accordance with the law of change of the detection optical path with the wavelength size of the light pulse, searches for the detection optical path determined this time in the corresponding direction by comparison, thereby determining the reference optical path corresponding to the detection optical path determined this time.

[0019] In another optional implementation, suppose that the detection light output by the first coupler is incident on the curved transparent object, passes through the curved transparent object, and then is transmitted to the third coupler through the optical path traversed by the detection light path L1; suppose that the reference light output by the first coupler is transmitted to the third coupler through the adjustable delay medium through the optical path traversed by the reference light path L2; after the adjustable delay medium completes the adjustment of the optical path difference between the reference light and the detection light of the same wavelength input to the third coupler, the corresponding difference between the detection light path L1 and the reference light path L2 = integer multiple * period T * wavelength / 2π, so as to ensure that the reference light and the detection light of the wavelength interfere at the third coupler to form an interference light signal with the maximum intensity.

[0020] In another optional implementation, let the distance between the incident position of the light pulse output by the imaging device on the curved transparent object and the exit point of the light pulse on the imaging device be H, let the thickness at the incident position be h, let the third optical path of the corresponding wavelength light pulse propagating in the curved transparent object be L3, the third optical path L3=n*h, n represents the refractive index of the curved transparent object, which is related to the wavelength of the light pulse, so when the wavelength of the light pulse is constant, the refractive index n is constant, and the size of the detection optical path corresponding to the wavelength light pulse is determined by the size of the distance H and the thickness h;

[0021] The processing device locally pre-stores a set of corresponding relationships between detection optical paths and reference optical paths set for each wavelength, each set having multiple corresponding relationships between detection optical paths and reference optical paths, each detection optical path of each corresponding relationship in the set corresponds to a distance H and thickness h combination, and each distance H and thickness h combination is composed of multiple distance H and thickness h association relationships;

[0022] When determining the thickness at the corresponding position of the curved transparent object based on the interference electrical signal, the processing device first determines the wavelength of the corresponding light pulse according to each interference electrical signal generated for the same position on the curved transparent object, and for each light pulse of different wavelengths determined, determines the detection optical path of the light pulse of the wavelength according to the moment when the electrical signal of the optical path of the same wavelength is received, and finds out the distance H and thickness h combination corresponding to the determined detection optical path at the wavelength; after finding out the corresponding distance H and thickness h combination at different wavelengths, compares each distance H and thickness h combination found, and when there is the same distance H and thickness h correlation relationship in each distance H and thickness h combination and it is the only one, it is determined that the distance H and thickness h correlation relationship is the parameter required for imaging the position on the curved transparent object.

[0023] In another optional implementation, a shifting device is further included, and the shifting device moves the curved transparent object so that the incident position of the laser signal output by the imaging device on the curved transparent object changes.

[0024] In another optional implementation, the processing device is connected to the displacement device, and after obtaining the parameters required for imaging the position of the curved transparent object, the processing device immediately controls the displacement device to move the curved transparent object.

[0025] In another optional implementation, it also includes an optical amplifier located between the dispersive medium and the first coupler, wherein the optical amplifier optically amplifies the series of optical pulses output by the dispersive medium;

[0026] It also includes a polarization controller, which is used to adjust the polarization state of the light pulse output by the curved transparent object so that the polarization states of the reference light and the detection light input to the third coupler are consistent, thereby ensuring the efficiency of the interference light signal formed at the third coupler corresponding to the interference spectrum.

[0027] The beneficial effects of the present invention are:

[0028] 1. The present invention sets a dispersive medium so that the laser signal forms a series of periodic light pulses after being stretched in the time domain by the dispersive medium, that is, the periods of the pulses in the series of light pulses are the same, and the optical path difference required to generate the interference light signal with the maximum light intensity can be associated with the wavelength of the light pulse; in order to meet the optical path difference requirement required to generate the interference light signal with the maximum light intensity, the delay adjustment amount of the adjustable delay medium is determined according to the wavelength and the detection optical path when adjusting the optical path difference, thereby improving the delay adjustment speed of light pulses with different wavelengths; in addition, the present invention adjusts the optical path difference for each light pulse with different wavelengths, so that the reference light and the detection light of different wavelengths transmitted to the third coupler in sequence interfere to generate the interference light signal with the maximum light intensity, thereby the present invention can quickly obtain a large number of interference light signals with the maximum light intensity required for determining the thickness of a curved transparent object, which not only improves the speed of tomography of the sample thickness using the point scanning imaging technology, but also reduces the requirements for the richness of the spectral components in the laser signal;

[0029] 2. The present invention sets a corresponding relationship set of detection optical path and reference optical path for each wavelength. For each light pulse of different wavelength, the detection optical path and reference optical path are searched from the set corresponding to the wavelength, thereby improving the delay adjustment speed. Since delay adjustment of multiple light pulses of different wavelengths is required at each position on the curved transparent object, the time saved by delay adjustment of light pulses of different wavelengths is accumulated, which can greatly improve the delay adjustment speed of the present invention.

[0030] 3. For the light pulses output from the same position of the curved transparent object, except for the first light pulse which needs to compare the detection optical path determined this time with each detection optical path in the set corresponding to the wavelength of the light pulse, the other light pulses only need to be located in order to the detection optical path corresponding to the last light pulse with the closest wavelength in the set, and then start from the located position, according to the wavelength size of the last light pulse and the current light pulse, and according to the change law of the detection optical path with the wavelength size of the light pulse, the detection optical path determined this time is compared and found in the corresponding direction, so as to determine the corresponding reference optical path, thereby further improving the speed of delay adjustment;

[0031] 4. The present invention is based on the principle that when the wavelength of a light pulse is constant, the size of the detection optical path corresponding to the wavelength light pulse is determined by the size of the distance H and the thickness h. When the wavelength of the light pulse is constant and the incident position of the light pulse changes, the corresponding relationship between the distance H and the thickness h of the detection optical path may be placed in the combination corresponding to the wavelength and the detection optical path. Since the distance H and the thickness h are the same when the light pulse is incident on the same position, for the same position, under different wavelength light pulses, there must be the same relationship between the distance H and the thickness h in each combination of the distance H and the thickness h corresponding to its detection optical path. By comparing each combination of the distance H and the thickness h, when there is only one same relationship between the distance H and the thickness h in each combination of the distance H and the thickness h, the distance H and the thickness h at the corresponding position of the curved transparent object can be determined. The distance H reflects the appearance contour of the curved transparent object at the corresponding position. Therefore, the present invention can simultaneously detect the appearance contour and thickness of the curved transparent object;

[0032] 5. The present invention moves the curved transparent object by setting a shifting device, so that the incident position of the light pulse output by the imaging device on the curved transparent object changes, thereby realizing the imaging of the curved transparent object surface and the imaging of the appearance contour of the three-dimensional structure;

[0033] 6. After obtaining the parameters required for imaging the position of the curved transparent object, the present invention can immediately control the shifting device to move the curved transparent object through the processing device, thereby improving the speed of converting the incident position of the light pulse on the curved transparent object;

[0034] 7. The present invention is provided with an optical amplifier, which can amplify the series of light pulses output by the dispersive medium; and a polarization controller is provided, and the polarization state controller is used to adjust the polarization state of the light pulses output by the curved transparent object, so that the polarization states of the reference light and the detection light input to the third coupler are consistent, thereby ensuring the efficiency of the interference light signal formed at the third coupler corresponding to the interference spectrum. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 It is a schematic structural diagram of an embodiment of the ultrafast tomography system for curved transparent objects of the present invention;

[0036] Figure 2 Schematic diagram of light pulses incident on a flat transparent object and a curved transparent object respectively;

[0037] Figure 3 It is a schematic structural diagram of another embodiment of the ultrafast chromatography system for curved transparent objects of the present invention. DETAILED DESCRIPTION

[0038] In order to enable those skilled in the art to better understand the technical solutions in the embodiments of the present invention and to make the above-mentioned purposes, features and advantages of the embodiments of the present invention more obvious and understandable, the technical solutions in the embodiments of the present invention are further described in detail below in conjunction with the accompanying drawings.

[0039] In the description of the present invention, unless otherwise specified and limited, it should be noted that the term "connection" should be understood in a broad sense. For example, it can be a mechanical connection or an electrical connection, or it can be the internal connection between two elements. It can be a direct connection or an indirect connection through an intermediate medium. For ordinary technicians in this field, the specific meanings of the above terms can be understood according to specific circumstances.

[0040] See also Figure 1 , is a schematic structural diagram of an embodiment of the ultrafast tomography system for curved transparent objects of the present invention. The system may include a laser generating device, a dispersive medium, a first coupler, an imaging device, a second coupler, a third coupler, a detector, a signal collector and a processing device, wherein the laser generating device is used to generate a laser signal; the dispersive medium is used to perform time domain stretching on the laser signal to form a series of periodic light pulses. Among the series of light pulses within a period, the wavelengths of the individual light pulses may be different and the individual light pulses may be arranged in chronological order according to the size of the wavelength. For example, when the dispersive medium is positively dispersed, the wavelengths of the individual light pulses arranged in chronological order gradually decrease, and when the dispersive medium is negatively dispersed, the wavelengths of the individual light pulses arranged in chronological order gradually increase.

[0041] The first coupler is used to split the series of light pulses into two paths, one of which is sent as detection light to the imaging device, and the other is sent as reference light to the third coupler through the adjustable delay medium. The imaging device is used to sequentially irradiate the light pulses of different wavelengths in the series of light pulses to the same position on the curved transparent object, and perform point scanning on the curved transparent object. The light pulses of different wavelengths are transmitted to the second coupler after passing through the curved transparent object, and combined with the Figure 1 As shown, in this embodiment, the corresponding wavelength light pulse reflected from the position on the curved transparent object can be transmitted to the second coupler in sequence via the imaging device and the circulator. Of course, after the corresponding wavelength light pulse is incident on the corresponding position, it can also be transmitted through the curved transparent object and then transmitted to the second coupler. The second coupler is used to divide the light pulse it receives into two paths, one path is transmitted to the detector, and the other path is transmitted to the third coupler; the detector converts the light pulse it receives from the second coupler into an optical path electrical signal; the signal collector collects the optical path electrical signal and sends it to the processing device.

[0042] Assume that the detection light output by the first coupler is incident on the curved transparent object, passes through the curved transparent object, and then is transmitted to the third coupler through the detection light path L1 (e.g. Figure 1 The optical pulse output by the first coupler is incident to the corresponding position of the curved transparent object through the circulator and the imaging device, and after being reflected back from the position of the curved transparent object, it is transmitted to the third coupler through the imaging device, the circulator, and the second coupler. The optical path that the reference light output by the first coupler travels through the adjustable delay medium to the third coupler is assumed to be the reference optical path L2. The processing device determines the detection optical path of the corresponding wavelength optical pulse according to the time when the optical path electrical signal of each different wavelength is received, and determines the reference optical path of the wavelength optical pulse according to the wavelength of the optical pulse and the detection optical path determined this time, thereby determining the delay adjustment amount of the adjustable delay medium for the wavelength optical pulse.

[0043] In this embodiment, the processing device can pre-store the correspondence between the optical path electrical signal receiving time and the detection optical path locally, and the processing device can pre-store the detection optical path and reference optical path correspondence sets respectively set for each wavelength locally, and each set has a plurality of correspondences between detection optical paths and reference optical paths. When the processing device determines the reference optical path of the wavelength optical pulse according to the wavelength of the optical pulse and the detection optical path determined this time, it can first search for the set corresponding to the wavelength of the optical pulse locally, find the detection optical path determined this time by comparison in the set, and then determine the reference optical path corresponding to the detection optical path determined this time.

[0044] For curved transparent objects, the size of the detection optical path corresponding to light pulses of different wavelengths will differ due to the following two factors: the incident position of the light pulse output by the imaging device on the curved transparent object, the distance H between the light pulse exit point on the imaging device, and the third optical path L3 of the corresponding wavelength light pulse propagating in the curved transparent object, wherein the third optical path L3 = n*h, n represents the refractive index of the curved transparent object, which is related to the wavelength of the light pulse, and h represents the thickness of the light pulse output by the imaging device at the incident position on the curved transparent object. It can be seen that when the wavelength of the light pulse is constant, the refractive index n is constant, and the size of the detection optical path corresponding to the light pulse of this wavelength is determined by the distance H and the thickness h. Figure 2As shown, when the curved transparent object is moved (for example, translated) so that the light pulse output by the imaging device is incident on different positions thereof, the distance H may change with the different incident positions of the light pulse, which will cause the detection optical path of the light pulse of the corresponding wavelength to change. Therefore, unlike a flat transparent object, when measuring a curved transparent object of the same thickness, when a light pulse of a corresponding wavelength is incident on the curved transparent object, multiple detection optical paths will appear due to different incident positions. As the number of wavelengths increases, the number of detection optical paths will increase exponentially, and correspondingly, the number of corresponding relationships between the detection optical paths and the reference optical paths will increase significantly. Under this premise, if the processing device only sets one set locally to store all the corresponding relationships between the detection optical paths and the reference optical paths, and for light pulses of different wavelengths, the corresponding detection optical paths and the reference optical paths are directly compared and found one by one from the set, then the speed of delay adjustment will be reduced.

[0045] To this end, the present invention sets a corresponding relationship set of detection optical path and reference optical path for each wavelength, and for each light pulse of different wavelength, its detection optical path and reference optical path are searched from the set corresponding to the wavelength, thereby improving the delay adjustment speed; since delay adjustment of multiple light pulses of different wavelengths needs to be performed at each position on the curved transparent object, the time saved by the delay adjustment of light pulses of different wavelengths is accumulated, which can greatly improve the delay adjustment speed of the present invention.

[0046] Although the above delay adjustment speed has been improved, for each light pulse, it is necessary to compare the detection optical path determined this time with each detection optical path in the set corresponding to its wavelength, and the delay adjustment speed still needs to be improved. Since the above refractive index n is not only related to the wavelength of the light pulse, but also usually changes regularly based on the wavelength of the light pulse, for example, as the wavelength of the light pulse increases, the refractive index increases, or as the wavelength of the light pulse increases, the refractive index decreases, and the size of the detection optical path is determined by the distance H and the third optical path L3, L3 = n*h, when the distance H and the thickness h are constant, the size of the detection optical path is determined by the wavelength of the light pulse related to the refractive index n. It can be seen that when light pulses of different wavelengths are incident on the same position, the size of the detection optical path will change regularly with the change in the size of the wavelength of the light pulse, for example, as the wavelength of the light pulse increases, the detection optical path increases; or as the wavelength of the light pulse increases, the detection optical path decreases.

[0047] Therefore, before determining the reference optical path of the wavelength optical pulse according to the wavelength of the optical pulse and the detection optical path determined this time, the processing device of the present invention also determines whether the currently received optical path electrical signal corresponds to the first optical pulse output from the same position of the curved transparent object. If so, the reference optical path of the wavelength optical pulse is determined according to the wavelength of the optical pulse and the detection optical path determined this time; otherwise, the reference optical path of the wavelength optical pulse is determined according to the wavelength of the optical pulse, the detection optical path determined this time, and the detection optical path corresponding to the last optical pulse closest to the wavelength. Specifically, in the set set for each wavelength, the corresponding relationship between the detection optical path and the reference optical path is arranged in the order of the size of the detection optical path. When the processing device determines the reference optical path of the optical pulse of the wavelength according to the wavelength of the optical pulse, the detection optical path determined this time, and the detection optical path corresponding to the last optical pulse closest to the wavelength, the processing device may first find out the set corresponding to the wavelength of the optical pulse locally, and then locate the detection optical path corresponding to the last optical pulse closest to the wavelength in the set in order, and start from the location position, according to the wavelength size of the last optical pulse and the current optical pulse, and according to the change rule of the detection optical path with the wavelength size of the optical pulse, find the detection optical path determined this time in the corresponding direction, so as to determine the reference optical path corresponding to the detection optical path determined this time. For example, when the detection optical path increases with the increase of the wavelength of the optical pulse, and the wavelength of the current optical pulse increases compared with the previous optical pulse, the detection optical path determined this time is found by comparison in the direction of the increase of the detection optical path; when the detection optical path decreases with the increase of the wavelength of the optical pulse, and the wavelength of the current optical pulse increases compared with the previous optical pulse, the detection optical path determined this time is found by comparison in the direction of the decrease of the detection optical path.

[0048] According to the present invention, for light pulses output from the same position of a curved transparent object, except for the first light pulse which needs to compare the detection optical path determined this time with each detection optical path in the set corresponding to the wavelength of the light pulse in sequence, other light pulses only need to be sequentially located to the detection optical path corresponding to the previous light pulse with the closest wavelength in the set, and then start from the located position, according to the wavelength size of the previous light pulse and the current light pulse, and according to the law of change of the detection optical path with the wavelength size of the light pulse, the detection optical path determined this time is compared and searched in the corresponding direction, so as to determine the corresponding reference optical path, thereby further improving the speed of delay adjustment.

[0049] After determining the delay adjustment amount of the adjustable delay medium for the optical pulse of the wavelength, the processing device can send the delay adjustment amount to the adjustable delay medium, and the adjustable delay medium performs delay processing on the optical pulse of the wavelength according to the delay adjustment amount to adjust the optical path difference of the reference light and the detection light of the same wavelength input to the third coupler. After the laser signal of the present invention is stretched in the time domain by the dispersive medium, a series of optical pulses that appear periodically will be generated, and the period of each optical pulse in the series of optical pulses is the same. Since the phase difference = 2π * optical path difference / wavelength, in order to form an interference optical signal with the maximum light intensity, it is necessary to satisfy the phase difference = integer multiples of the period. According to the above two formulas, it can be deduced that when the optical path difference of the reference light and the detection light input to the third coupler = L1-L2 = integer multiples * period T * wavelength / 2π, the maximum light intensity can appear after interference. Therefore, after the adjustable delay medium completes the adjustment of the optical path difference between the reference light and the detection light of the same wavelength input to the third coupler, the difference between the corresponding detection optical path L1 and the reference optical path L2 = integer multiple * period T * wavelength / 2π, so as to ensure that the reference light and the detection light of the wavelength interfere at the third coupler to form an interference light signal with the maximum light intensity.

[0050] After the adjustable delay medium completes the delay processing of the light pulse of the wavelength, the delayed light pulse is transmitted to the third coupler, and then the third coupler couples the reference light and the detection light with the same wavelength it receives to generate an interference light signal with the maximum light intensity; the detector converts the interference light signal into an interference electrical signal; the signal collector collects the interference electrical signal and sends it to the processing device; the processing device analyzes the thickness at the corresponding position of the curved transparent object based on the interference electrical signal.

[0051] When the light pulse is incident on the corresponding position of the curved transparent object and is reflected and transmitted back to the second coupler, the connection diagram of each component of the system of the present invention is as follows: Figure 1As shown, the output end of the laser generating device is connected to the input end of the first coupler through a dispersive medium, the first output end of the first coupler is connected to the first end of the circulator, and the second output end is connected to the first input end of the third coupler through the adjustable delay medium; the second end and the third end of the circulator are respectively connected to the input end of the imaging device and the second coupler, a curved transparent object is provided below the imaging device, the two output ends of the second coupler are respectively connected to the second input end of the third coupler and the second input end of the detector, the output end of the third coupler is connected to the first input end of the detector, the output end of the detector is connected to the processing device through a signal collector, and the processing device is connected to the adjustable delay medium. Wherein, the imaging device may include a collimator and an objective lens, the collimator collimates the light pulses provided by the circulator, and the objective lens concentrates the light pulses of different wavelengths to a point to irradiate the corresponding position of the curved transparent object; the adjustable delay medium may be an adjustable delay line, the dispersive medium may be a dispersion compensation optical fiber, and the signal collector may be a high-speed oscilloscope.

[0052] As can be seen from the above embodiments, the present invention sets a dispersive medium so that the laser signal forms a series of periodic light pulses after being stretched in the time domain by the dispersive medium, that is, the period of each pulse in the series of light pulses is the same, and the optical path difference required to generate the interference light signal with the maximum light intensity can be associated with the wavelength of the light pulse; in order to meet the optical path difference requirement required to generate the interference light signal with the maximum light intensity, the delay adjustment amount of the adjustable delay medium is determined according to the wavelength and the detection optical path when adjusting the optical path difference, thereby improving the delay adjustment speed of light pulses with different wavelengths; in addition, the present invention adjusts the optical path difference for each light pulse with different wavelengths, so that the reference light and the detection light of different wavelengths transmitted to the third coupler in sequence interfere to generate the interference light signal with the maximum light intensity, thereby the present invention can quickly obtain a large number of interference light signals with the maximum light intensity required for determining the thickness of a curved transparent object, which not only improves the speed of tomography of the sample thickness using the point scanning imaging technology, but also reduces the requirements for the richness of the spectral components in the laser signal.

[0053] Although the traditional tomography technology can obtain the thickness of transparent objects, it cannot determine the appearance of transparent objects, especially the curved transparent objects in the present invention. For this reason, the present invention further designs the thickness determination algorithm. As described above, when the wavelength of the light pulse is constant, the refractive index n is constant, and the size of the detection optical path corresponding to the wavelength light pulse is determined by the size of the distance H and the thickness h. Therefore, the processing device of the present invention pre-stores a set of corresponding relationships between the detection optical path and the reference optical path set for each wavelength locally, and each set has multiple corresponding relationships between detection optical paths and reference optical paths. The detection optical path of each corresponding relationship in the set corresponds to a distance H and thickness h combination, and each distance H and thickness h combination is composed of multiple distance H and thickness h association relationships. When determining the thickness at the corresponding position of the curved transparent object based on the interference electrical signal, the processing device can first determine the wavelength of the corresponding light pulse according to each interference electrical signal generated for the same position on the curved transparent object, and for each light pulse of different wavelengths determined, determine the detection optical path of the light pulse of the wavelength according to the moment when the electrical signal of the optical path of the same wavelength is received, and find out the distance H and thickness h combination corresponding to the determined detection optical path at the wavelength; after finding out the corresponding distance H and thickness h combination at different wavelengths, compare the found distance H and thickness h combinations, and when there is the same distance H and thickness h correlation relationship in each distance H and thickness h combination and it is the only one, determine that the distance H and thickness h correlation relationship is the parameter required for imaging the position on the curved transparent object.

[0054] Since the distance H and thickness h are constant for the same position on a curved transparent object, the detection optical path corresponding to each wavelength pulse will be different as the wavelength of the incident light pulse changes, but for this position, the detection optical path corresponding to each wavelength pulse is also fixed. The present invention is based on the principle that when the wavelength of a light pulse is constant, the size of the detection optical path corresponding to the wavelength light pulse is determined by the size of the distance H and the thickness h. When the wavelength of the light pulse is constant and the incident position of the light pulse changes, the corresponding relationship between the distance H and the thickness h of the detection optical path that may appear is placed in a combination corresponding to the wavelength and the detection optical path. Since the distance H and the thickness h are the same when the light pulse is incident on the same position, for the same position, under different wavelength light pulses, there must be the same distance H and thickness h correlation relationship in each distance H and thickness h combination corresponding to its detection optical path. By comparing each distance H and thickness h combination, when there is only one same distance H and thickness h correlation relationship in each distance H and thickness h combination, the distance H and thickness h at the corresponding position of the curved transparent object can be determined. The distance H reflects the appearance contour of the curved transparent object at the corresponding position. Therefore, the present invention can simultaneously detect the appearance contour and thickness of the curved transparent object.

[0055] In addition, in order to realize the imaging of the three-dimensional structure appearance contour of the curved transparent object, the present invention may also include a shifting device, which moves the curved transparent object so that the incident position of the laser signal output by the imaging device on the curved transparent object changes. The shifting device can be used to translate the curved transparent object in the left-right and / or front-back directions, and the left-right and front-back directions are perpendicular to the emission direction of the laser signal output by the imaging device; of course, the shifting device can also be set at the center position of the arc segment corresponding to the curved transparent object to drive the curved transparent object to rotate. At this time, the rotation angle needs to be combined to restore the three-dimensional structure of the curved transparent object. In order to increase the conversion speed of the incident position of the light pulse on the curved transparent object, the processing device of the present invention is connected to the shifting device, which can immediately control the shifting device to move the curved transparent object after obtaining the parameters required for imaging the position of the curved transparent object.

[0056] See also Figure 3 , is a schematic structural diagram of another embodiment of the ultrafast chromatography system for curved transparent objects of the present invention. Figure 3 and Figure 1 The difference between the illustrated embodiments is that the system may further include an optical amplifier located between the dispersive medium and the first coupler, and the optical amplifier optically amplifies the series of optical pulses output by the dispersive medium; the system may further include a polarization controller, and the polarization state controller is used to adjust the polarization state of the optical pulses output by the curved transparent object, so that the polarization states of the reference light and the detection light input to the third coupler are consistent, thereby ensuring the efficiency of the interference light signal formed at the third coupler corresponding to the interference spectrum. In this embodiment, the polarization controller can be arranged between the third end of the circulator and the input end of the second coupler.

[0057] As can be seen from the above embodiments, the present invention sets a dispersive medium so that the laser signal forms a series of periodic light pulses after being stretched in the time domain by the dispersive medium, that is, the period of each pulse in the series of light pulses is the same, and the optical path difference required to generate the interference light signal with the maximum light intensity can be associated with the wavelength of the light pulse; in order to meet the optical path difference requirement required to generate the interference light signal with the maximum light intensity, the delay adjustment amount of the adjustable delay medium is determined according to the wavelength and the detection optical path when adjusting the optical path difference, thereby improving the delay adjustment speed of light pulses with different wavelengths; in addition, the present invention adjusts the optical path difference for each light pulse with different wavelengths, so that the reference light and the detection light of different wavelengths transmitted to the third coupler in sequence interfere to generate the interference light signal with the maximum light intensity, thereby the present invention can quickly obtain a large number of interference light signals with the maximum light intensity required for determining the thickness of a curved transparent object, which not only improves the speed of tomography of the sample thickness using the point scanning imaging technology, but also reduces the requirements for the richness of the spectral components in the laser signal.

[0058] Those skilled in the art will readily appreciate other embodiments of the present invention after considering the specification and practicing the invention disclosed herein. This application is intended to cover any variations, uses or adaptations of the present invention that follow the general principles of the present invention and include common knowledge or customary techniques in the art that are not disclosed by the present invention. The specification and examples are to be considered exemplary only, and the true scope and spirit of the present invention are indicated by the following claims.

[0059] It will be appreciated that the invention is not limited to the precise construction that has been described above and shown in the drawings and that various modifications and changes may be made without departing from its scope. The scope of the invention is governed solely by the appended claims.

Claims

1. An ultrafast tomography system for curved transparent objects, characterized in that: include: A laser generating device, used for generating a laser signal; A dispersive medium, used for performing time-domain stretching on the laser signal to form a series of periodically occurring optical pulses; A first coupler is used to split the series of optical pulses into two paths, one path is sent as detection light to an imaging device, and the other path is sent as reference light to a third coupler through an adjustable delay medium; The imaging device is used to sequentially irradiate light pulses of different wavelengths in the series of light pulses onto the same position on the curved transparent object, and the light pulses of different wavelengths are transmitted to the second coupler after passing through the curved transparent object; The second coupler is used to divide the received optical pulse into two paths, one path is transmitted to the detector, and the other path is transmitted to the third coupler; the detector converts the optical pulse received from the second coupler into an optical path electrical signal; the signal collector collects the optical path electrical signal and sends it to the processing device; The processing device determines the detection optical path of the optical pulse of the corresponding wavelength according to the time when the optical path electrical signal is received for each optical path electrical signal of different wavelengths, and determines the reference optical path of the optical pulse of the wavelength according to the wavelength of the optical pulse and the detection optical path determined this time, so as to determine the delay adjustment amount of the adjustable delay medium for the optical pulse of the wavelength; the adjustable delay medium performs delay processing on the optical pulse of the wavelength according to the delay adjustment amount, so as to adjust the optical path difference between the reference light and the detection light of the same wavelength input to the third coupler; The third coupler couples the reference light and the detection light with the same wavelength received by it to generate an interference light signal with the maximum light intensity; the detector converts the interference light signal into an interference electrical signal; the signal collector collects the interference electrical signal and sends it to the processing device; The processing device analyzes the thickness at the corresponding position of the curved transparent object based on the interference electrical signal; Suppose the detection light output by the first coupler is incident on the curved transparent object, passes through the curved transparent object, and the optical path it travels to be transmitted to the third coupler is the detection optical path L1. Suppose the optical path that the reference light output by the first coupler travels to be transmitted to the third coupler through the adjustable delay medium is the reference optical path L2. After the adjustable delay medium completes the adjustment of the optical path difference between the reference light and the detection light of the same wavelength input to the third coupler, the difference between the corresponding detection optical path L1 and the reference optical path L2 = integer multiple * period T * wavelength / 2π, so as to ensure that the reference light and the detection light of the wavelength interfere at the third coupler to form an interference light signal with the maximum intensity.

2. The curved transparent object ultrafast tomography system according to claim 1, characterized in that: The output end of the laser generating device is connected to the input end of the first coupler through a dispersive medium, the first output end of the first coupler is connected to the first end of the circulator, and the second output end is connected to the first input end of the third coupler through the adjustable delay medium; the second end and the third end of the circulator are respectively connected to the imaging device and the input end of the second coupler, a curved transparent object is provided below the imaging device, the two output ends of the second coupler are respectively connected to the second input end of the third coupler and the second input end of the detector, the output end of the third coupler is connected to the first input end of the detector, the output end of the detector is connected to the processing device through a signal collector, and the processing device is connected to the adjustable delay medium.

3. The curved transparent object ultrafast tomography system according to claim 1, characterized in that: Before determining the reference optical path of the optical pulse of the wavelength according to the wavelength of the optical pulse and the detection optical path determined this time, the processing device further determines whether the optical path electrical signal currently received corresponds to the first optical pulse output from the same position of the curved transparent object, and if so, determines the reference optical path of the optical pulse of the wavelength according to the wavelength of the optical pulse and the detection optical path determined this time; Otherwise, the reference optical path of the optical pulse of the wavelength is determined according to the wavelength of the optical pulse, the detection optical path determined this time, and the detection optical path corresponding to the previous optical pulse with the closest wavelength.

4. The curved transparent object ultrafast tomography system according to any one of claims 1 to 3, characterized in that: The processing device locally pre-stores a set of corresponding relationships between detection optical paths and reference optical paths respectively set for each wavelength, and each set contains a plurality of corresponding relationships between detection optical paths and reference optical paths; When the processing device determines the reference optical path of the wavelength optical pulse based on the wavelength of the optical pulse and the detection optical path determined this time, it first searches for a set corresponding to the wavelength of the optical pulse locally, compares and searches for the detection optical path determined this time in the set, and then determines the reference optical path corresponding to the detection optical path determined this time.

5. The curved transparent object ultrafast tomography system according to claim 4, characterized in that: In the series of light pulses within the period, the wavelengths of the light pulses are different and the light pulses are arranged in chronological order according to the size of the wavelengths; when light pulses of different wavelengths are incident on the same position, the size of the detection optical path changes regularly as the size of the wavelength of the light pulse changes; the corresponding relationship between the detection optical path and the reference optical path in the set is arranged in the order of the size of the detection optical path; When determining the reference optical path of the light pulse of the wavelength according to the wavelength of the light pulse, the detection optical path determined this time and the detection optical path corresponding to the light pulse that was closest to the wavelength last time, the processing device first searches out a set corresponding to the wavelength of the light pulse locally, and then locates the detection optical path corresponding to the light pulse that was closest to the wavelength last time in the set in order, and starting from the located position, according to the wavelength size of the last light pulse and the current light pulse, and in accordance with the law of change of the detection optical path with the wavelength size of the light pulse, searches for the detection optical path determined this time in the corresponding direction by comparison, thereby determining the reference optical path corresponding to the detection optical path determined this time.

6. The curved transparent object ultrafast tomography system according to claim 1, characterized in that: Assume that the distance between the incident position of the light pulse output by the imaging device on the curved transparent object and the exit point of the light pulse on the imaging device is H, the thickness at the incident position is h, and the third optical path of the corresponding wavelength light pulse propagating in the curved transparent object is L3, the third optical path L3=n*h, n represents the refractive index of the curved transparent object, which is related to the wavelength of the light pulse, so when the wavelength of the light pulse is constant, the refractive index n is constant, and the size of the detection optical path corresponding to the wavelength light pulse is determined by the size of the distance H and the thickness h; The processing device locally pre-stores a set of corresponding relationships between detection optical paths and reference optical paths set for each wavelength, each set having multiple corresponding relationships between detection optical paths and reference optical paths, each detection optical path of each corresponding relationship in the set corresponds to a distance H and thickness h combination, and each distance H and thickness h combination is composed of multiple distance H and thickness h association relationships; When determining the thickness at the corresponding position of the curved transparent object based on the interference electrical signal, the processing device first determines the wavelength of the corresponding light pulse according to each interference electrical signal generated for the same position on the curved transparent object, and for each light pulse of different wavelengths determined, determines the detection optical path of the light pulse of the wavelength according to the moment when the electrical signal of the optical path of the same wavelength is received, and finds out the distance H and thickness h combination corresponding to the determined detection optical path at the wavelength; after finding out the distance H and thickness h combination corresponding to the different wavelengths, compares the found distance H and thickness h combinations, and when there is the same distance H and thickness h correlation relationship in each distance H and thickness h combination and it is the only one, it is determined that the distance H and thickness h correlation relationship is the parameter required for imaging the position on the curved transparent object.

7. The curved transparent object ultrafast tomography system according to claim 1, characterized in that: It also includes a shifting device, which moves the curved transparent object so that the incident position of the laser signal output by the imaging device on the curved transparent object changes.

8. The curved transparent object ultrafast tomography system according to claim 7, characterized in that: The processing device is connected to the displacement device, and after obtaining the parameters required for imaging the position of the curved transparent object, the processing device immediately controls the displacement device to move the curved transparent object.

9. The curved transparent object ultrafast tomography system according to claim 1, characterized in that: Also included is an optical amplifier located between the dispersive medium and the first coupler, the optical amplifier optically amplifies the series of optical pulses output by the dispersive medium; It also includes a polarization controller, which is used to adjust the polarization state of the light pulse output by the curved transparent object so that the polarization states of the reference light and the detection light input to the third coupler are consistent, thereby ensuring the efficiency of the interference light signal formed at the third coupler corresponding to the interference spectrum.

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