CN112556585A - Measuring system and measuring method - Google Patents
Measuring system and measuring method Download PDFInfo
- Publication number
- CN112556585A CN112556585A CN202011301743.4A CN202011301743A CN112556585A CN 112556585 A CN112556585 A CN 112556585A CN 202011301743 A CN202011301743 A CN 202011301743A CN 112556585 A CN112556585 A CN 112556585A
- Authority
- CN
- China
- Prior art keywords
- light
- optical fiber
- time
- pump light
- fiber
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Pending
Links
Images
Classifications
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
- G01B11/00—Measuring arrangements characterised by the use of optical techniques
- G01B11/02—Measuring arrangements characterised by the use of optical techniques for measuring length, width or thickness
- G01B11/06—Measuring arrangements characterised by the use of optical techniques for measuring length, width or thickness for measuring thickness ; e.g. of sheet material
- G01B11/0616—Measuring arrangements characterised by the use of optical techniques for measuring length, width or thickness for measuring thickness ; e.g. of sheet material of coating
- G01B11/0625—Measuring arrangements characterised by the use of optical techniques for measuring length, width or thickness for measuring thickness ; e.g. of sheet material of coating with measurement of absorption or reflection
Landscapes
- Physics & Mathematics (AREA)
- General Physics & Mathematics (AREA)
- Length Measuring Devices By Optical Means (AREA)
- Ultra Sonic Daignosis Equipment (AREA)
- Investigating Or Analyzing Materials By The Use Of Ultrasonic Waves (AREA)
Abstract
The application discloses a measuring system and a measuring method. The system comprises a fiber laser, a first fiber beam splitter, a time delay and a detector. The fiber laser generates a pulse beam, and the first fiber beam splitter splits the pulse beam into pump light and probe light. The time delayer makes the delay time between the pump light and the probe light adjustable. Both lights are finally emitted into the object to be measured. The detector is used for acquiring signal light formed by reflection of the detection light by the object to be detected under different delay times, and acquiring detection information according to the signal light. Therefore, the measurement system is used for realizing the photoacoustic measurement of the object to be measured. Part of the optical path in the system is realized through optical fibers, and the optical fiber optical path has the advantages of being soft, free in shape change, long in transmission distance and suitable for various severe environments with strong electromagnetic interference, flammability, explosiveness and the like, and the stability and the anti-interference capability of the system are improved. Complicated work such as collimation adjustment is avoided in the optical fiber light path, the convenience of adjusting devices in the measuring process is improved, and the testing time is shortened.
Description
Technical Field
The present application relates to the field of measurement technologies, and in particular, to a measurement system and a measurement method.
Background
The film thickness is measured by optoacoustic, which is a precise optical measurement technology, the film thickness measurement range is 50A-10 um, and the precision can reach 0.1A. Adopt the space light path to measure the membrane thickness among the prior art, but the space light path is adjusted loaded down with trivial details, for example: one device is fine-tuned and the other devices are adjusted accordingly, otherwise the precision and accuracy are seriously affected. Therefore, the labor cost is high, and the testing time is long. In addition, the spatial light path is easy to interfere, and is difficult to be applied to the environment with strong electromagnetic interference or flammability and explosiveness for realizing measurement, so that the stability of a measurement system is poor, and the anti-interference capability is weak. How to promote measurement system's stability and interference killing feature, promote the convenience that the device was adjusted in the measurement process, shorten test time, reduce the human cost, become the technical problem that this field urgently needed to be solved.
Disclosure of Invention
Based on the problems, the application provides a measuring system and a measuring method, so that the stability and the anti-interference capability of the measuring system are improved, the convenience of adjusting devices in the measuring process is improved, the testing time is shortened, and the labor cost is reduced.
The embodiment of the application discloses the following technical scheme:
in a first aspect, the present application provides a measurement system comprising:
the system comprises a fiber laser, a first fiber beam splitter, a time delayer and a detector;
wherein the fiber laser is used for generating a pulse beam;
the first optical fiber beam splitter is used for splitting the pulse light beam into pump light and probe light;
the time delayer is used for making the delay time between the pumping light and the probe light adjustable; the detection light and the pump light emitted by the time delayer are incident to an object to be measured; or the pumping light and the detection light emitted by the time delayer are incident to the object to be detected; the pump light is used for forming sound waves in the object to be detected;
the detector is used for acquiring signal light formed by reflecting the detection light through an object to be detected under different delay times and acquiring detection information according to the signal light.
Optionally, the time delayer is an optical fiber type time delayer or a non-optical fiber type time delayer.
Optionally, when the time delayer is specifically the non-optical fiber type time delayer, the non-optical fiber type time delayer includes: a linear stage and a reflective assembly;
the linear platform bears the reflection assembly and drives the reflection assembly to move along a first direction or a second direction, and the first direction is opposite to the second direction;
when the reflection assembly moves along the first direction, the delay time of the probe light relative to the pumping light is linearly reduced; when the reflection assembly moves along the second direction, the delay time of the probe light relative to the pumping light increases linearly.
Optionally, the reflection assembly includes a first reflection surface and a second reflection surface, and a non-zero included angle is formed between the first reflection surface and the second reflection surface; the probe light or the pump light is incident to the first reflecting surface, reflected by the first reflecting surface, reaches the second reflecting surface, and is emitted through the second reflecting surface.
Optionally, the non-optical fiber type time delayer specifically comprises a first reflecting component and a second reflecting component which are oppositely arranged; the first reflecting assembly is fixed, and the second reflecting assembly can move along the first direction and the second direction under the drive of the linear platform;
the probe light or the pump light is used for reflecting between the reflecting surface of the first reflecting component and the reflecting surface of the second reflecting component; the probe light or the pump light is incident from one of the first reflection element and the second reflection element and exits from the other reflection element.
Optionally, when the time delayer is specifically the non-optical fiber type time delayer, the system further includes: a first fiber collimator disposed between any output port of the first fiber splitter and the non-fiber time delayer;
the first optical fiber collimator is configured to collimate the pump light split by the first optical fiber beam splitter into parallel light and provide the parallel light to the non-optical fiber time delay unit, or is configured to provide the parallel probe light split by the first optical fiber beam splitter to the non-optical fiber time delay unit.
Optionally, the system further comprises: the second optical fiber collimator, the third optical fiber collimator and the first group of lenses are positioned between the non-optical fiber type time delayer and the object to be detected, and the second optical fiber collimator is connected with the third optical fiber collimator through optical fibers; the pump light or the probe light emitted by the time delay device enters the optical fiber through the second optical fiber collimator and is transmitted to the third optical fiber collimator through the optical fiber;
the third optical fiber collimator is used for collimating the detection light transmitted by the connected optical fiber into parallel light;
the first group of lenses is used for converging the parallel light emitted by the third optical fiber collimator onto the surface of the object to be measured.
Optionally, the method further comprises: a time difference system; the time difference system is arranged on a transmission light path of the pumping light;
the time difference system is used for performing time difference processing on the pump light to obtain two pump light pulse sequences with fixed time delay, and synthesizing the two pump light pulse sequences with fixed time delay to obtain synthesized pump light.
Optionally, the time difference system is specifically an optical fiber type time difference system, and the optical fiber type time difference system specifically includes: the optical fiber coupler comprises a second optical fiber beam splitter, a first optical fiber, a second optical fiber and an optical fiber coupler;
wherein the first and second optical fibers are different lengths; the first end of the first optical fiber and the first end of the second optical fiber are respectively connected with two different emergent ends of the second optical fiber beam splitter, and the second end of the first optical fiber and the second end of the second optical fiber are respectively connected with two different incident ends of the optical fiber coupler;
the second optical fiber beam splitter is used for splitting the pump light incident to the optical fiber type time difference system into a first light beam and a second light beam, wherein the first light beam is transmitted to the optical fiber coupler through the first optical fiber, and the second light beam is transmitted to the optical fiber coupler through the second optical fiber;
the optical fiber coupler is used for receiving two light beams which have the fixed time delay through the first optical fiber and the second optical fiber, and is specifically used for coupling the two received light beams and outputting the combined pump light.
Optionally, the system further comprises: and the fourth optical fiber collimator is used for collimating the synthesized pump light into parallel light, and the second group of lenses is used for converging the parallel light emitted by the fourth optical fiber collimator to the surface of the object to be measured.
Optionally, the system further comprises: and the modulator is arranged on a transmission light path of the pump light and is used for carrying out amplitude modulation or polarization modulation on the pump light.
Optionally, when the modulator is used for amplitude modulating the pump light, the modulator includes any one of:
an electro-optic modulator, an acousto-optic modulator, or a chopper.
Optionally, the system further comprises: the device comprises a signal generator, a phase-locked amplifier and a signal processor;
the signal generator is used for transmitting a first signal to the modulator and transmitting a second signal to the lock-in amplifier;
the modulator is specifically configured to output the modulated pump light at a preset frequency according to the first signal;
the signal processor is used for acquiring a relation curve between the time delay and the detection information according to the detection information when the detection light and the pumping light have different time delays, and searching a peak of the relation curve to acquire echo time; and calculating the thickness of the object to be measured according to the sound velocity in the object to be measured and the echo time.
Optionally, the lock-in amplifier is configured to demodulate, according to the second signal and at the preset frequency, the signal detected by the detector and output the demodulated signal to the signal processor;
and the signal processor is used for acquiring the detection information according to the signal demodulated by the phase-locked amplifier.
Optionally, the pulse width of the pulsed light beam generated by the fiber laser is less than or equal to 1 ps.
Optionally, the fixed delay is between 0.1ps and 10 ps.
In a second aspect, the present application provides a measurement method, which applies the measurement system of the first aspect, the method includes:
generating a pulsed light beam with the fiber laser;
dividing the pulse light beam into pump light and probe light by using the first optical fiber beam splitter;
receiving the pump light or the probe light by the time delayer, and adjusting the delay time between the pump light and the probe light; the detection light and the pump light emitted by the time delayer are incident to an object to be measured; or the pumping light and the detection light emitted by the time delayer are incident to the object to be detected; the pump light is used for forming sound waves in the object to be detected;
and acquiring a plurality of signal lights formed by reflecting the detection light through an object to be detected under different delay times by using the detector, and acquiring detection information according to the signal lights.
Optionally, the measurement system further comprises a time difference system; the time difference system is arranged on a transmission light path of the pumping light; the method further comprises the following steps:
and carrying out time difference processing on the pump light by using the time difference system to obtain two pump light pulse sequences with fixed time delay, and synthesizing the two pump light pulse sequences with fixed time delay to obtain the synthesized pump light.
Compared with the prior art, the method has the following beneficial effects:
the application provides a measurement system includes: the optical fiber laser comprises an optical fiber laser, a first optical fiber beam splitter, a time delayer and a detector. The fiber laser generates a pulse beam, and the first fiber beam splitter divides the pulse beam into pump light and probe light. The time delayer is positioned on the transmission light path of the pumping light or the detection light and is used for enabling the delay time between the pumping light and the detection light to be adjustable. The two paths of light are finally emitted into the object to be measured, wherein the pump light is used for forming sound waves in the object to be measured, and therefore the reflectivity of the object to be measured is changed. The detector is used for acquiring signal light formed by reflection of the detection light by the object to be detected under different delay times so as to acquire detection information according to the signal light. Therefore, the measurement system is used for realizing the photoacoustic measurement of the object to be measured. Part of the optical path in the measurement system is realized through optical fibers, and the optical fiber optical path has the advantages of flexibility, randomly changeable shape, long transmission distance and applicability to various severe environments with strong electromagnetic interference, flammability, explosiveness and the like, so that the stability and the anti-interference capability of the system are improved. In addition, complicated work such as collimation adjustment is avoided in the optical fiber light path, convenience of device adjustment in the measuring process is improved, testing time is shortened, and labor cost is reduced.
Furthermore, the optical fiber laser and the first optical fiber beam splitter are both optical fiber elements, so that complicated work such as collimation adjustment can be avoided; meanwhile, the time delayer adopts a non-optical fiber type time delayer, so that the adjustment precision of the delay time can be improved, and the instability of an optical path caused by the adjustment of the delay time of the time delayer can be compensated by matching the time delayer with the optical fiber laser and the first optical fiber divider chip, so that the system performance is improved.
Drawings
In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings needed to be used in the description of the embodiments or the prior art will be briefly introduced below, and it is obvious that the drawings in the following description are only some embodiments of the present application, and it is obvious for those skilled in the art that other drawings can be obtained according to the drawings without inventive exercise.
Fig. 1 is a schematic structural diagram of a measurement system according to an embodiment of the present disclosure;
fig. 2 is a schematic structural diagram of another measurement system provided in an embodiment of the present application;
FIG. 3 is a schematic diagram of an implementation of a reflective assembly according to an embodiment of the present disclosure;
FIG. 4 is a schematic diagram of another implementation of a reflective assembly provided by an embodiment of the present application;
FIG. 5 is a schematic diagram of another implementation of a reflective assembly provided by an embodiment of the present application;
fig. 6 is a schematic structural diagram of an optical fiber type time difference system according to an embodiment of the present disclosure;
fig. 7 is a schematic structural diagram of another measurement system provided in an embodiment of the present application;
fig. 8 is a flowchart of a measurement method according to an embodiment of the present application.
Detailed Description
In order to make the technical solutions of the present application better understood, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application, and it is obvious that the described embodiments are only a part of the embodiments of the present application, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present application.
System embodiment
Fig. 1 is a schematic structural diagram of a measurement system according to an embodiment of the present application. As shown in fig. 1, the measuring system includes: a fiber laser 100, a first fiber splitter 200, a time delay 300, and a detector 400. The connection and function of each device in the measurement system will be described below.
In the measurement system shown in fig. 1, the fiber laser 100 is connected to the first fiber splitter 200 through an optical fiber, and the first fiber splitter 200 is also optically connected to the time delay 300. The time delay device 300 has various implementations, such as a fiber type or a non-fiber type, and when the time delay device 300 is a fiber type, the first fiber splitter 200 can be connected to the time delay device 300 through an optical fiber.
The fiber laser 100 is used to generate a pulsed beam. As an example, the pulse width to produce the ultrashort pulse beam is less than or equal to 1ps (picosecond).
The first fiber splitter 200 splits the pulse beam transmitted by the fiber laser 100 into two beams, one of which is referred to as pump light and the other is referred to as probe light. The pump light and the probe light are both incident to the same incident position of the object to be measured. The pump light is used for forming sound waves in the object to be detected and exciting an ultrasonic signal. Thus, the reflectivity of the corresponding position of the object to be measured is changed. The photoacoustic measurement uses the change of the reflectivity of the object to be measured by the pump light. The pump light and the probe light are pulse lights. It can be understood that there is no time delay between the pump light and the probe light emitted from the first fiber splitter 200. When performing photoacoustic measurement (e.g., measuring film thickness) on an object to be measured, the present embodiment requires that a time delay exists between the pump light and the probe light incident on the object to be measured, and the time delay is adjustable. For this, the time delay 300 may be disposed on the transmission path of the pumping light as shown in fig. 1, and the time delay 300 may be disposed on the transmission path of the probe light as shown in fig. 2. Fig. 2 is a schematic structural diagram of another measurement system provided in an embodiment of the present application. The time delay device 300 only needs to adjust the time delay of one path of light.
The detector 400 may particularly be a photodetector for converting an optical signal into an electrical signal. In the technical solution of the embodiment of the present application, the detector 400 is right to acquire signal light formed by reflection of the detection light by the object to be detected under different delay times in the scanning process of the delay time, and acquires detection information according to the signal light through photoelectric conversion processing of the signal light. Specifically, the detection information may be obtained according to the light intensity information of the signal light, or may be detected according to the polarization information of the signal light and the position of the light spot. The scanning is specifically realized by a time delay device 300: the time delayer 300 continuously adjusts the delay time between the pump light and the probe light during the scanning of the delay time between the pump light and the probe light. The time delayer 300 may specifically implement the scanning of the delay time in dependence on the electrical drive signal.
Since the time delay device 300 continuously adjusts the delay time between the pump light and the detection light during the operation of the measurement system, the detection information obtained during the continuous acquisition detection of the detector 400 also varies with the delay time. In this way, corresponding measurement results can be obtained according to the change situation. For example, the thickness, the sound velocity, the young's modulus, and the like of the object to be measured are obtained.
The specific content of the photoacoustic measurement of the object to be measured is not limited here. Therefore, the implementation process of obtaining the detection information and obtaining the measurement result is not limited. The object to be measured may be a metal film, a dielectric film, or the like, and the specific type of the object to be measured is not limited in this embodiment.
The above is the measurement system provided in the embodiments of the present application. Part of the optical path in the measurement system is realized through optical fibers, and the optical fiber optical path has the advantages of flexibility, randomly changeable shape, long transmission distance and applicability to various severe environments with strong electromagnetic interference, flammability, explosiveness and the like, so that the stability and the anti-interference capability of the system are improved. In addition, complicated work such as collimation adjustment is avoided in the optical fiber light path, convenience of device adjustment in the measuring process is improved, testing time is shortened, and labor cost is reduced.
The time delay device 300 described above may be an optical fiber type time delay device or a non-optical fiber type time delay device. For the optical fiber type time delayer, the input and output of light thereto are realized by optical fibers, i.e., the optical path from the first optical fiber splitter 200 to the time delayer 300 is an optical fiber optical path. For non-fiber type time delayers, it can be considered that both the input and output of light thereto are realized through spatial light paths. Several implementations of the non-fiber type time delayer are described below.
In an embodiment of the present application, a non-fiber type time delayer includes: a linear stage and a reflective assembly. Wherein, linear platform bears reflection assembly, can drive its reflection assembly linear movement who bears: the linear movement can be performed along a first direction and a second direction opposite to the first direction. The linear stage can be implemented in various forms, for example, the linear stage can be entirely movable, or the linear stage includes a slide rail capable of linearly moving, and the reflection assembly is located on the slide rail and moves along with the slide rail.
When the reflection assembly moves along the first direction, the delay time of the probe light relative to the pump light is linearly reduced; when the reflection assembly moves along the second direction, the delay time of the probe light relative to the pump light increases linearly.
The reflective component encompasses many possible implementations. Fig. 3, 4 and 5 are schematic views of three different implementations of a reflective assembly, respectively.
As shown in fig. 3, the reflective assembly includes a first reflective surface R1 and a second reflective surface R2, the first reflective surface R1 and the second reflective surface R2 having a non-zero included angle therebetween. The probe light or the pump light enters the first reflection surface R1, is reflected by the first reflection surface R1, reaches the second reflection surface R2, and exits through the second reflection surface R2. Here, the size of the incident angle of the pump light or the probe light incident on the first reflection surface R1 is not limited. In this implementation, the light incident on the reflective element and the light exiting from the reflective element are parallel to each other and located on the same side of the reflective element, so that the adjustment of the delay time during linear movement is more convenient.
In addition, the non-fiber type time delayer may further include two reflection components. In fig. 4, the non-optical fiber type time delayer includes two oppositely disposed reflection assemblies, a first reflection assembly K1 and a second reflection assembly K2, respectively. Wherein the first reflective assembly K1 is fixed and the second reflective assembly K2 is movable by the linear stage (not shown in fig. 4). The first reflection assembly K1 and the second reflection assembly K2 shown in fig. 4 each include two reflection surfaces R1 and R2. In fig. 4, the pump light or the probe light is incident from the first reflection unit K1 and finally exits from the second reflection unit K2. In practical applications, the pump light or the probe light may be incident on the second reflection assembly K2 first, and then the first reflection assembly K1 emits the light beam (i.e. along the direction opposite to the arrow shown in fig. 4).
In the implementation of the present application, there is no limitation on the number of the reflection elements included in the non-fiber type time delayer. One, two or even more than two reflecting assemblies may be included. Referring to fig. 5, the structure of a non-fiber type time delayer comprising four components is illustrated. The non-fiber type time delay device shown in fig. 5 requires that at least one of the reflective elements is fixed and at least one of the reflective elements moves along with the linear stage.
In the non-fiber type time delay device shown in fig. 3 and 4, when the linear stage moves by a distance Δ x, the optical path difference between the probe light and the pump light changes by 2 × Δ x. In the embodiment of the present application, in order to enhance a smaller pump light signal that is easily submerged in noise, an amplitude modulator may be disposed on a transmission optical path of the pump light, so as to implement amplitude modulation on the pump light. In practical applications, the amplitude modulator may be implemented by an electro-optical modulator (EOM), an acousto-optical modulator (AOM), or a Chopper (Chopper). The modulator may also be a polarization modulator, and the modulation of the periodic variation of the pump light signal is achieved by amplitude modulation or polarization modulation of the modulator. The modulator may receive a first signal emitted from the signal generator, and output the modulated pump light at a predetermined frequency according to the first signal. And outputting the modulated pump light at a preset frequency, which is beneficial to the subsequent extraction of signals. The description is as follows. The signal generator can also transmit a second signal to a phase-locked amplifier, the phase-locked amplifier is connected with the detector, and the phase-locked amplifier can demodulate the signal output by the detector according to the second signal and the preset frequency. The signal processor is electrically connected with the phase-locked amplifier and can obtain detection information according to the signal demodulated by the phase-locked amplifier.
As mentioned above, the measurement system provided in the embodiment of the present application applies a photoacoustic measurement technology, and the pump light excites an ultrasonic wave on the object to be measured and affects the reflectivity in the material. The signal light reflected by the object to be detected to the detector reflects the light intensity when the reflectivity changes along with the delay time of the pumping light and the detection light. And thus can be used to find peaks and obtain measurements.
Assuming that the purpose of the photoacoustic measurement isThe thickness of the object to be measured is measured, in the embodiment of the application, the signal processor can acquire a relation curve between delay time and detection information according to the detection information when the detection light and the pumping light have different delay times, and the relation curve is subjected to peak searching to obtain echo time techo. The signal processor is used for further processing the sound velocity v in the object to be measuredsAnd the echo time techoAnd calculating the thickness d of the object to be measured. The calculation formula of the thickness of the object to be measured is as follows:
d＝vs*techo/2 formula (1)
In the above-described relationship curve, the initial time is a time when the optical path difference between the pump light and the pulse light is 0. The echo time is the time corresponding to the first peak value after the initial time except the noise when the peak is searched. The echo time t can be obtained by making difference between the echo time and the initial timeecho. Alternatively, the echo time is the time difference between adjacent peaks other than noise.
In the measurement system provided in the embodiment of the present application, in order to eliminate a background signal and a low-frequency component in a signal, reduce noise, and improve sensitivity of measurement, the measurement system may further include a time difference system. The time difference system is also beneficial to extracting effective detection information from the signal light subsequently. The time difference system is specifically arranged on a transmission optical path of the pump light. The time difference system is used for carrying out time difference processing on the pump light to obtain two pump light pulse sequences with fixed time delay, and synthesizing the two pump light pulse sequences with fixed time delay to obtain synthesized pump light. As an example, the fixed delay Δ t is between 0.1ps and 10 ps.
In the embodiment of the present application, the time difference system may be an optical fiber type time difference system or a non-optical fiber type time difference system. The former is internally provided with a fiber optical path, and the latter is internally provided with a space optical path. An implementation of the optical fiber type time differential system is described below.
When the time delayer is of an optical fiber type, the time difference system is of an optical fiber type; when the time delayer is of the non-fiber type, the time differential system is of the non-fiber type. The time delayer is the same as the time difference system in type, so that the coupling efficiency can be improved, and the signal strength can be increased. Fig. 6 is a schematic structural diagram of an optical fiber time difference system according to an embodiment of the present disclosure. The optical fiber type time difference system 600 includes: a second fiber splitter 601, a first fiber 602, a second fiber 603, and a fiber coupler 604. The first optical fiber 602 and the second optical fiber 603 are both connected to the second optical fiber splitter 601 at one end and to the optical fiber coupler 604 at the other end.
It should be noted that in the optical fiber type time difference system 60, the lengths of the first optical fiber 602 and the second optical fiber 603 are different, so that two paths of pump light in the first optical fiber 602 and the second optical fiber 603 keep a fixed delay.
The second fiber splitter 601 is used to split the pump light incident to the fiber-type time difference system 60 into a first beam and a second beam, wherein the first beam is transmitted to the fiber coupler 604 through the first fiber 602, and the second beam is transmitted to the fiber coupler 604 through the second fiber 603. The optical fiber coupler 604 couples the two received light beams with a fixed delay through the first optical fiber 602 and the second optical fiber 603, and outputs the combined pump light (combined into a pulse sequence).
Assuming that the length difference between the first optical fiber 602 and the second optical fiber 603 is Δ L and the speed of light in the fiber core is v, the fixed delay Δ t of the synthesized pump light is calculated as follows:
Δ t ═ Δ L/v equation (2)
In the measurement system provided by the embodiment of the application, the time difference system is arranged, so that background signals and low-frequency components in signals are eliminated, noise signals are reduced, the convenience and accuracy of signal extraction are correspondingly improved, weak signals can be detected, and the measurement sensitivity is improved. Meanwhile, for an object to be measured comprising a plurality of stacked thin films, the technology improves the signal-to-noise ratio of the measurement of the thickness of each layer and improves the selectivity of a thin layer buried under a thicker layer.
Fig. 7 is a schematic structural diagram of another measurement system provided in an embodiment of the present application. As shown in fig. 7, the measuring system includes: a fiber laser 100, a first fiber splitter 200, a non-fiber type time delayer 300, a detector 400, an amplitude modulator 500, a time difference system 600, a signal generator 700, a lock-in amplifier 800, and a signal processor 900.
In the measurement system shown in fig. 7, since the non-optical fiber type time delay device 300 is used, the optical path inside the delay device 300 is a spatial optical path. The non-fiber type time delayer 300 is disposed on a transmission path of the probe light, and it is understood that it may be disposed on a transmission path of the pumping light. Also included in the system is a first fiber collimator C1, in the example of fig. 7, a first fiber collimator C1 is disposed between the port of the first fiber splitter 200 that outputs probe light and the non-fiber type time delay 300.
And a first fiber collimator C1, for providing the probe light split by the first fiber splitter 200 to the non-fiber type time delay device 300 after the probe light is collimated by the first fiber splitter 200. If the non-fiber type time delay 300 is specifically disposed on the transmission path of the pump light, the first fiber collimator C1 is also disposed on the transmission path of the pump light: the first fiber collimator C1 is disposed between the port of the first fiber splitter 200 for outputting the pump light and the non-fiber type time delay device 300 (this connection is not shown in fig. 7), and is used for providing the pump light split by the first fiber splitter 200 to the non-fiber type time delay device 300 in parallel.
The conversion from the fiber optic path to the spatial path is achieved by the first fiber collimator C1. Further, as shown in fig. 7, a lens or lens group L0 may be provided between the first fiber collimator C1 and the non-fiber type time delay 300, and the lens or lens group L0 may be used for expanding the beam, adjusting the spot size, and the like.
As shown in fig. 7, the measurement system may further include: a second fiber collimator C2, a third fiber collimator C3 and a first group of lenses L1 which are positioned between the non-fiber type time delay device 300 and the object to be tested. Wherein the second fiber collimator C2 is connected with the third fiber collimator C3 through optical fibers. As shown in fig. 7, the probe light (or pump light) emitted from the time delay device 300 enters the optical fiber through the second fiber collimator C2, and is transmitted to the third fiber collimator C3. The third fiber collimator C3 is used to collimate the probe light transmitted by the connected optical fiber into parallel light. The first group of lenses L1 may include at least one lens for converging the parallel light emitted from the third fiber collimator C3 onto the surface of the object.
Further alternatively, as shown in fig. 7, a lens or lens group L0 may be further provided between the third fiber collimator C3 and the first group lens L1 for expanding, converging, adjusting the spot size, and the like. Further alternatively, a lens or lens group L0 may be provided between the non-fiber type time delay device 300 and the second fiber collimator C2 for expanding, converging, adjusting the spot size, and the like. The second fiber collimator C2 realizes the conversion of the spatial light path into the fiber light path. The third fiber collimator C3 realizes the conversion of the fiber optical path into the spatial optical path.
As shown in fig. 7, the measurement system may further include: a fourth fiber collimator C4 and a second group lens L2 on the transmission path of the pump light. The fourth optical fiber collimator C4 is configured to collimate the synthesized pump light output by the time difference system 600 into parallel light, and the second group of lenses L2 is configured to converge the parallel light emitted by the fourth optical fiber collimator C4 onto the surface of the object to be measured. Among them, the second group lens L2 may include at least one lens. Optionally, a lens or lens group L0 may be further disposed between the fourth fiber collimator C4 and the second group lens L2 for expanding, converging, adjusting the spot size, and the like.
As other possible implementations, the modulator 500 may also be on the output side of the time difference system 600. That is, the pump light is subjected to the time difference processing by the time difference system 600 and then modulated by the modulator 500.
As can be seen from fig. 7 and the above-described measurement system, when the time difference system 600 is a fiber-type time difference system, the pump light path is a complete fiber structure path. When the time delayer 300 is embodied as an optical fiber type time delayer, the optical path of the probe light can also realize a complete optical fiber structure optical path. In addition, the optical fiber type time difference system is an optical path with an all-optical fiber structure, so that the stability and the coupling efficiency of the system can be improved, and the signal intensity is increased. At this time, the fourth fiber collimator C4 realizes the conversion of the fiber optical path into the spatial optical path.
The covering of the optical fiber light path in the measuring system avoids most light path adjusting work, the construction process of the whole system is shortened time-consuming, and the efficiency is improved. In addition, the stability and the anti-interference performance of the system are greatly improved. Can be suitable for more complex application scenes.
In other embodiments, the first fiber splitter 200 may be replaced with a polarizing splitter. For example, p light is split as pump light and s light is split as probe light; or separating s light as pumping light and p light as probe light. The polarization directions of the p light and the s light are perpendicular to each other.
Based on the measurement system provided by the foregoing embodiment, correspondingly, the present application further provides a measurement method for implementing measurement by using the system. The measurement method will be described and explained with reference to the drawings.
Method embodiment
Fig. 8 is a flowchart of a measurement method according to an embodiment of the present application. As shown in fig. 8, the measurement method includes:
s801: generating a pulsed light beam using a fiber laser;
s802: dividing the pulse light beam into pump light and probe light by using a first optical fiber beam splitter;
s803: receiving the pump light or the probe light by using a time delayer, and adjusting the delay time between the pump light and the probe light; the detection light and the pump light emitted by the time delayer are incident to an object to be measured; or the pumping light and the detection light emitted by the time delayer are incident to the object to be detected; the pump light is used for forming sound waves in the object to be measured;
s804: and acquiring signal light formed by the reflection of the detection light by the object to be detected under different delay times by using the detector, and acquiring detection information according to the signal light.
In the measurement system for implementing the measurement method shown in fig. 8, part of the optical path is implemented by the optical fiber, and the optical fiber optical path has the advantages of being flexible, randomly changeable in shape, long in transmission distance, and applicable to various severe environments with strong electromagnetic interference, flammability, explosiveness and the like, so that the stability and the anti-interference capability of the system are improved. In addition, complicated work such as collimation adjustment is omitted in the optical fiber light path, convenience of device adjustment in the application process and before application of the measurement method is improved, test time is shortened, and labor cost is reduced.
In a possible implementation manner, in order to eliminate a background signal and a low-frequency component in a signal, reduce noise, and improve sensitivity of measurement, the measurement method provided in the embodiment of the present application may further include:
and carrying out time difference processing on the pump light by using a time difference system to obtain two pump light pulse sequences with fixed time delay, and synthesizing the two pump light pulse sequences with fixed time delay to obtain the synthesized pump light.
Through the time difference processing of the time difference system, background signals and low-frequency components in the signals are eliminated, noise signals are reduced, the convenience and the accuracy of signal extraction are correspondingly improved, and the measurement sensitivity is improved. Meanwhile, for an object to be measured comprising a plurality of stacked thin films, the technology improves the signal-to-noise ratio of the measurement of the thickness of each layer and improves the selectivity of a thin layer buried under a thicker layer.
In one possible implementation, in order to enhance the smaller pump light signal that is easily submerged in noise, the measurement method may further include: and amplitude modulation is carried out on the pump light by utilizing an amplitude modulator arranged on a transmission light path of the pump light.
The amplitude modulator modulates the amplitude of the pumping light, so that the effective signal is not easily submerged in noise.
In one possible implementation, the measurement method may further include: acquiring a relation curve between time delay and detection information by a signal processor according to the detection information when the detection light and the pumping light have different time delays, and searching a peak of the relation curve to acquire echo time; and calculating the thickness of the object to be measured according to the sound velocity in the object to be measured and the echo time.
By executing the measuring method, the thickness of the object to be measured is accurately measured. In other scenarios, the detection information may be used to obtain surface defect information (e.g., position, size) of the dut, or obtain size parameters of the dut, etc. The specific scenario for implementing photoacoustic measurement by using the above measurement system and measurement method is not limited here.
It should be noted that, in the present specification, all the embodiments are described in a progressive manner, and the same and similar parts among the embodiments may be referred to each other, and each embodiment focuses on the differences from the other embodiments. One of ordinary skill in the art can understand and implement it without inventive effort.
The above description is only one specific embodiment of the present application, but the scope of the present application is not limited thereto, and any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope of the present application should be covered by the scope of the present application. Therefore, the protection scope of the present application shall be subject to the protection scope of the claims.
Claims (18)
1. A measurement system, comprising:
the system comprises a fiber laser, a first fiber beam splitter, a time delayer and a detector;
wherein the fiber laser is used for generating a pulse beam;
the first optical fiber beam splitter is used for splitting the pulse light beam into pump light and probe light;
the time delayer is used for making the delay time between the pumping light and the probe light adjustable; the detection light and the pump light emitted by the time delayer are incident to an object to be measured; or the pumping light and the detection light emitted by the time delayer are incident to the object to be detected; the pump light is used for forming sound waves in the object to be detected;
the detector is used for acquiring signal light formed by reflecting the detection light through an object to be detected under different delay times and acquiring detection information according to the signal light.
2. The measurement system of claim 1, wherein the time delayer is an optical fiber type time delayer or a non-optical fiber type time delayer.
3. The measurement system according to claim 2, wherein when the time delayer is embodied as the non-fiber type time delayer, the non-fiber type time delayer includes: a linear stage and a reflective assembly;
the linear platform bears the reflection assembly and drives the reflection assembly to move along a first direction or a second direction, and the first direction is opposite to the second direction;
when the reflection assembly moves along the first direction, the delay time of the probe light relative to the pumping light is linearly reduced; when the reflection assembly moves along the second direction, the delay time of the probe light relative to the pumping light increases linearly.
4. The measurement system of claim 3, wherein the reflective assembly comprises a first reflective surface and a second reflective surface, the first reflective surface and the second reflective surface having a non-zero included angle therebetween; the probe light or the pump light is incident to the first reflecting surface, reflected by the first reflecting surface, reaches the second reflecting surface, and is emitted through the second reflecting surface.
5. The measurement system according to claim 3, wherein the non-fiber type time delayer particularly comprises a first reflection component and a second reflection component which are oppositely arranged; the first reflecting assembly is fixed, and the second reflecting assembly can move along the first direction and the second direction under the drive of the linear platform;
the probe light or the pump light is used for reflecting between the reflecting surface of the first reflecting component and the reflecting surface of the second reflecting component; the probe light or the pump light is incident from one of the first reflection element and the second reflection element and exits from the other reflection element.
6. The measurement system according to any of claims 2-5, wherein when the time delayer is in particular the non-fiber time delayer, the system further comprises: a first fiber collimator disposed between any output port of the first fiber splitter and the non-fiber time delayer;
the first optical fiber collimator is configured to collimate the pump light split by the first optical fiber beam splitter into parallel light and provide the parallel light to the non-optical fiber time delay unit, or is configured to provide the parallel probe light split by the first optical fiber beam splitter to the non-optical fiber time delay unit.
7. The measurement system of claim 6, further comprising: the second optical fiber collimator, the third optical fiber collimator and the first group of lenses are positioned between the non-optical fiber type time delayer and the object to be detected, and the second optical fiber collimator is connected with the third optical fiber collimator through optical fibers; the pump light or the probe light emitted by the time delay device enters the optical fiber through the second optical fiber collimator and is transmitted to the third optical fiber collimator through the optical fiber;
the third optical fiber collimator is used for collimating the detection light transmitted by the connected optical fiber into parallel light;
the first group of lenses is used for converging the parallel light emitted by the third optical fiber collimator onto the surface of the object to be measured.
8. The measurement system of any one of claims 1-5, 7, further comprising: a time difference system; the time difference system is arranged on a transmission light path of the pumping light;
the time difference system is used for performing time difference processing on the pump light to obtain two pump light pulse sequences with fixed time delay, and synthesizing the two pump light pulse sequences with fixed time delay to obtain synthesized pump light.
9. The measurement system according to claim 8, wherein the time differential system is in particular a fiber-optic time differential system, in particular comprising: the optical fiber coupler comprises a second optical fiber beam splitter, a first optical fiber, a second optical fiber and an optical fiber coupler;
wherein the first and second optical fibers are different lengths; the first end of the first optical fiber and the first end of the second optical fiber are respectively connected with two different emergent ends of the second optical fiber beam splitter, and the second end of the first optical fiber and the second end of the second optical fiber are respectively connected with two different incident ends of the optical fiber coupler;
the second optical fiber beam splitter is used for splitting the pump light incident to the optical fiber type time difference system into a first light beam and a second light beam, wherein the first light beam is transmitted to the optical fiber coupler through the first optical fiber, and the second light beam is transmitted to the optical fiber coupler through the second optical fiber;
the optical fiber coupler is used for receiving two light beams which have the fixed time delay through the first optical fiber and the second optical fiber, and is specifically used for coupling the two received light beams and outputting the combined pump light.
10. The measurement system of claim 9, further comprising: and the fourth optical fiber collimator is used for collimating the synthesized pump light into parallel light, and the second group of lenses is used for converging the parallel light emitted by the fourth optical fiber collimator to the surface of the object to be measured.
11. The measurement system of any of claims 1-5, 7, 9-10, further comprising: and the modulator is arranged on a transmission light path of the pump light and is used for carrying out amplitude modulation or polarization modulation on the pump light.
12. The measurement system of claim 11, wherein when the modulator is used for amplitude modulating the pump light, the modulator comprises any one of:
an electro-optic modulator, an acousto-optic modulator, or a chopper.
13. The measurement system of claim 11, further comprising: the device comprises a signal generator, a phase-locked amplifier and a signal processor;
the signal generator is used for transmitting a first signal to the modulator and transmitting a second signal to the lock-in amplifier;
the modulator is specifically configured to output the modulated pump light at a preset frequency according to the first signal;
the signal processor is used for acquiring a relation curve between the time delay and the detection information according to the detection information when the detection light and the pumping light have different time delays, and searching a peak of the relation curve to acquire echo time; and calculating the thickness of the object to be measured according to the sound velocity in the object to be measured and the echo time.
14. The measurement system of claim 13,
the lock-in amplifier is used for demodulating the signal detected by the detector at the preset frequency according to the second signal and outputting the demodulated signal to the signal processor;
and the signal processor is used for acquiring the detection information according to the signal demodulated by the phase-locked amplifier.
15. The measurement system of claim 1, wherein the pulse width of the pulsed light beam generated by the fiber laser is less than or equal to 1 ps.
16. The measurement system of claim 8, wherein the fixed delay is between 0.1ps and 10 ps.
17. A measuring method, characterized in that the measuring system of any one of claims 1-16 is applied, the method comprising:
generating a pulsed light beam with the fiber laser;
dividing the pulse light beam into pump light and probe light by using the first optical fiber beam splitter;
receiving the pump light or the probe light by the time delayer, and adjusting the delay time between the pump light and the probe light; the detection light and the pump light emitted by the time delayer are incident to an object to be measured; or the pumping light and the detection light emitted by the time delayer are incident to the object to be detected; the pump light is used for forming sound waves in the object to be detected;
and acquiring a plurality of signal lights formed by reflecting the detection light through an object to be detected under different delay times by using the detector, and acquiring detection information according to the signal lights.
18. The method of claim 17, wherein the measurement system further comprises a time differencing system; the time difference system is arranged on a transmission light path of the pumping light; the method further comprises the following steps:
and carrying out time difference processing on the pump light by using the time difference system to obtain two pump light pulse sequences with fixed time delay, and synthesizing the two pump light pulse sequences with fixed time delay to obtain the synthesized pump light.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202011301743.4A CN112556585A (en) | 2020-11-19 | 2020-11-19 | Measuring system and measuring method |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202011301743.4A CN112556585A (en) | 2020-11-19 | 2020-11-19 | Measuring system and measuring method |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CN112556585A true CN112556585A (en) | 2021-03-26 |
Family
ID=75044311
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN202011301743.4A Pending CN112556585A (en) | 2020-11-19 | 2020-11-19 | Measuring system and measuring method |
Country Status (1)
| Country | Link |
|---|---|
| CN (1) | CN112556585A (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN115684629A (en) * | 2022-11-03 | 2023-02-03 | 江苏光微半导体有限公司 | Quantum acoustic wave sensor and quantum voiceprint recognition system |
Citations (16)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPH05346309A (en) * | 1991-05-23 | 1993-12-27 | Nippon Steel Corp | Simultaneous measuring method for thickness of transparent thin film and sound speed |
| WO1997041418A1 (en) * | 1996-04-26 | 1997-11-06 | Brown University Research Foundation | Optical method for determining the mechanical properties of a material |
| US5748318A (en) * | 1996-01-23 | 1998-05-05 | Brown University Research Foundation | Optical stress generator and detector |
| CN1363820A (en) * | 2002-02-05 | 2002-08-14 | 北京大学 | Short-pulse laser and ultrasonic method and equipment for presisely measuring thickness |
| CN1555479A (en) * | 2001-07-13 | 2004-12-15 | ³��ƽ | Method and apparatus for increasing signal to noise ratio in a photoacoustic film thickness measurement system |
| CN201072406Y (en) * | 2007-08-06 | 2008-06-11 | 苏州大学 | Pump detecting device based on 4f phase coherent imaging |
| CN101975626A (en) * | 2010-10-13 | 2011-02-16 | 华中科技大学 | Brillouin scattering based distributive fiber sensing system |
| CN103207033A (en) * | 2013-04-22 | 2013-07-17 | 中国人民解放军国防科学技术大学 | Distributed fiber sensing method and device for simultaneously measuring temperature and strain |
| CN103954226A (en) * | 2014-04-03 | 2014-07-30 | 华南理工大学 | Long-distance distributed type large-measuring-range rapid response optical fiber dynamic strain sensing device |
| CN104199044A (en) * | 2014-09-18 | 2014-12-10 | 中国工程物理研究院流体物理研究所 | Dual-mode superspeed moving object movement speed measurement device and method |
| CN106525092A (en) * | 2016-11-03 | 2017-03-22 | 华南理工大学 | High-spatial resolution long-distance distributed optical fiber temperature strain sensing system |
| CN106796899A (en) * | 2014-05-29 | 2017-05-31 | 布朗大学 | Optical system and method for determining the stress in substrate |
| CN108226047A (en) * | 2017-12-29 | 2018-06-29 | 山东大学 | Optoacoustic spectroscopy multiple spot gas detecting system based on optical fiber laser annular cavity |
| CN108414443A (en) * | 2018-03-09 | 2018-08-17 | 苏州大学 | A kind of method and system realized ultrashort one pulse time and differentiate pump probe |
| CN111307756A (en) * | 2019-11-20 | 2020-06-19 | 南京航空航天大学 | Frequency-adjustable ultrafast time resolution transient reflection spectrometer |
| CN111638192A (en) * | 2020-06-08 | 2020-09-08 | 南京大学 | Tunable pumping-detection system based on super-continuum spectrum light source |
-
2020
- 2020-11-19 CN CN202011301743.4A patent/CN112556585A/en active Pending
Patent Citations (16)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPH05346309A (en) * | 1991-05-23 | 1993-12-27 | Nippon Steel Corp | Simultaneous measuring method for thickness of transparent thin film and sound speed |
| US5748318A (en) * | 1996-01-23 | 1998-05-05 | Brown University Research Foundation | Optical stress generator and detector |
| WO1997041418A1 (en) * | 1996-04-26 | 1997-11-06 | Brown University Research Foundation | Optical method for determining the mechanical properties of a material |
| CN1555479A (en) * | 2001-07-13 | 2004-12-15 | ³��ƽ | Method and apparatus for increasing signal to noise ratio in a photoacoustic film thickness measurement system |
| CN1363820A (en) * | 2002-02-05 | 2002-08-14 | 北京大学 | Short-pulse laser and ultrasonic method and equipment for presisely measuring thickness |
| CN201072406Y (en) * | 2007-08-06 | 2008-06-11 | 苏州大学 | Pump detecting device based on 4f phase coherent imaging |
| CN101975626A (en) * | 2010-10-13 | 2011-02-16 | 华中科技大学 | Brillouin scattering based distributive fiber sensing system |
| CN103207033A (en) * | 2013-04-22 | 2013-07-17 | 中国人民解放军国防科学技术大学 | Distributed fiber sensing method and device for simultaneously measuring temperature and strain |
| CN103954226A (en) * | 2014-04-03 | 2014-07-30 | 华南理工大学 | Long-distance distributed type large-measuring-range rapid response optical fiber dynamic strain sensing device |
| CN106796899A (en) * | 2014-05-29 | 2017-05-31 | 布朗大学 | Optical system and method for determining the stress in substrate |
| CN104199044A (en) * | 2014-09-18 | 2014-12-10 | 中国工程物理研究院流体物理研究所 | Dual-mode superspeed moving object movement speed measurement device and method |
| CN106525092A (en) * | 2016-11-03 | 2017-03-22 | 华南理工大学 | High-spatial resolution long-distance distributed optical fiber temperature strain sensing system |
| CN108226047A (en) * | 2017-12-29 | 2018-06-29 | 山东大学 | Optoacoustic spectroscopy multiple spot gas detecting system based on optical fiber laser annular cavity |
| CN108414443A (en) * | 2018-03-09 | 2018-08-17 | 苏州大学 | A kind of method and system realized ultrashort one pulse time and differentiate pump probe |
| CN111307756A (en) * | 2019-11-20 | 2020-06-19 | 南京航空航天大学 | Frequency-adjustable ultrafast time resolution transient reflection spectrometer |
| CN111638192A (en) * | 2020-06-08 | 2020-09-08 | 南京大学 | Tunable pumping-detection system based on super-continuum spectrum light source |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN115684629A (en) * | 2022-11-03 | 2023-02-03 | 江苏光微半导体有限公司 | Quantum acoustic wave sensor and quantum voiceprint recognition system |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| US10578740B2 (en) | Coherent optical distance measurement apparatus and method | |
| JP5752040B2 (en) | Compact optical fiber arrangement for anti-chirp FMCW coherent laser radar | |
| WO2018170478A1 (en) | Fmcw lidar methods and apparatuses including examples having feedback loops | |
| CN108873007B (en) | Frequency modulation continuous wave laser ranging device for inhibiting vibration effect | |
| JPH10213485A (en) | Light measuring apparatus | |
| JP2004527765A5 (en) | ||
| CN109031340B (en) | Continuous frequency modulation laser radar device for measuring object movement speed | |
| JP2004527765A (en) | Optical sensor for distance measurement | |
| US10310085B2 (en) | Photonic integrated distance measuring pixel and method of distance measurement | |
| CN103154720A (en) | Measuring apparatus and measuring method for metallic microstructures ormaterial properties | |
| CN109031341B (en) | Object movement speed measuring method using continuous frequency modulation laser radar device | |
| CN112556585A (en) | Measuring system and measuring method | |
| CN107064539A (en) | A kind of big visual field photon Doppler speed measuring device and method | |
| JP7315154B2 (en) | Distance and speed measuring device | |
| CN113534104A (en) | Frequency modulation continuous wave laser imaging system based on Fourier domain mode locking fiber laser | |
| CN114562942A (en) | Measuring system and measuring method | |
| CN114894123B (en) | High-precision optical wedge angle measuring device and measuring method thereof | |
| CN114543685B (en) | Interferometer modulator, measurement system and measurement method | |
| KR102598511B1 (en) | Ultrafast camera system and measurement method thereof | |
| JPS63196829A (en) | Method and apparatus for searching fault point of light waveguide | |
| US20240353289A1 (en) | Light intensity distribution pattern measuring device and method | |
| RU2788568C1 (en) | Device of doppler velocity measurement based on interferometer with fiber input of radiation | |
| US11656268B2 (en) | Apparatus and method for testing coupled AC circuit | |
| JP2024056589A (en) | Optical distance meter | |
| CN117687005A (en) | Laser radar for inhibiting Doppler frequency shift based on positive and negative dispersion chirped fiber bragg grating |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| PB01 | Publication | ||
| PB01 | Publication | ||
| SE01 | Entry into force of request for substantive examination | ||
| SE01 | Entry into force of request for substantive examination |