CN113256869A - Detection method of paper money and terahertz spectrometer - Google Patents
Detection method of paper money and terahertz spectrometer Download PDFInfo
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- G07—CHECKING-DEVICES
- G07D—HANDLING OF COINS OR VALUABLE PAPERS, e.g. TESTING, SORTING BY DENOMINATIONS, COUNTING, DISPENSING, CHANGING OR DEPOSITING
- G07D7/00—Testing specially adapted to determine the identity or genuineness of valuable papers or for segregating those which are unacceptable, e.g. banknotes that are alien to a currency
- G07D7/06—Testing specially adapted to determine the identity or genuineness of valuable papers or for segregating those which are unacceptable, e.g. banknotes that are alien to a currency using wave or particle radiation
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Abstract
The application discloses a paper money detection method and a terahertz spectrometer, wherein the detection method comprises the following steps: acquiring a time domain spectral line of the paper money to be detected; acquiring characteristic parameters based on the time domain spectral line, wherein the characteristic parameters comprise peak values and timestamps corresponding to the peak values; acquiring relative delay time by using a timestamp corresponding to the peak value and a reference time domain spectral line; and inputting the relative delay time into a preset mathematical model, and acquiring the number of the paper money to be detected based on an output result of the preset mathematical model. According to the method and the device, the time domain spectral line of the paper money to be measured is obtained, the relative delay time is further obtained based on the time domain spectral line and the reference time domain spectral line, the number of the paper money to be measured can be obtained according to the preset mathematical model and the relative delay time, and the number of the paper money to be measured can be rapidly measured by using the time domain delay information of the time domain spectral line.
Description
Technical Field
The application relates to the field of paper money detection, in particular to a paper money detection method and a terahertz spectrometer.
Background
At present, the counting and rechecking of paper money mainly adopts a currency detector and a manual mode, the mode has the defects of high labor intensity, long working time, low efficiency and easy occurrence of errors in the counting of the paper money, belongs to a contact mode, easily causes certain abrasion to the paper money, seriously influences the credit of a bank and the look of national 'business cards', is also related to the requirements of national economic development and currency circulation, and directly influences commodity circulation and commodity exchange.
In the prior art, X rays, beta rays or ultrasonic waves are used for detecting paper money, but the X rays and the beta rays have ionizing radiation to a human body, so that the function of the human body can have serious consequences when the paper money works in an ionizing radiation environment for a long time, and meanwhile, couplant is required to be added on the surface of the paper money in ultrasonic sensing detection, so that the surface characteristic of the paper money is damaged, and the quality of the paper money can be adversely affected.
Disclosure of Invention
The application at least provides a paper money detection method and a terahertz spectrometer.
The application provides a detection method of paper money in a first aspect, and the detection method comprises the following steps:
acquiring a time domain spectral line of the paper money to be detected;
acquiring characteristic parameters based on the time domain spectral line, wherein the characteristic parameters comprise peak values and timestamps corresponding to the peak values;
acquiring relative delay time by using a timestamp corresponding to the peak value and a reference time domain spectral line;
and inputting the relative delay time into a preset mathematical model, and acquiring the number of the paper money to be detected based on an output result of the preset mathematical model.
Wherein, obtain the time domain spectral line of the paper currency that awaits measuring, include:
acquiring a detection area of the paper money to be detected, wherein the detection area of the paper money to be detected is arranged corresponding to a through hole on a placing clamp for placing the paper money to be detected;
emitting a terahertz signal to the detection area by utilizing a terahertz spectrometer;
and acquiring terahertz light passing through the paper money to be detected so as to acquire a time-domain spectral line of the paper money to be detected.
Obtaining the relative delay time by using the timestamp corresponding to the peak value and the reference time domain spectral line, including:
acquiring a reference time domain spectral line before placing paper money to be detected;
acquiring reference characteristic parameters based on the reference time domain spectral lines, wherein the reference characteristic parameters comprise reference peak values and reference time stamps corresponding to the reference peak values;
relative delay times are obtained using the time stamps and the reference time stamp.
Before acquiring the time domain spectral line of the paper money to be detected, the method comprises the following steps:
acquiring paper money with different numbers of preset groups;
respectively acquiring a first characteristic parameter of each group of paper money by using a terahertz spectrometer, wherein the first characteristic parameter comprises the relative delay time between the time domain spectral line peak value of the group of paper money and the reference time domain spectral line peak value;
and training a mathematical model by using the number of the paper money with the preset number and the corresponding relative delay time to obtain a preset mathematical model.
The second aspect of the present application provides a terahertz spectrometer for implementing the detection method.
Wherein, terahertz spectrum appearance one step includes:
a laser assembly for generating laser light;
the light splitting assembly is arranged on a main optical axis of the laser assembly and is used for splitting laser to generate first laser and second laser;
the emission antenna assembly is connected with the light splitting assembly and used for receiving the first laser and generating and emitting a terahertz signal by using the first laser;
the receiving antenna assembly is connected with the light splitting assembly and used for receiving the second laser and the terahertz signal penetrating through the paper money to be detected and generating a time-domain spectral line of the paper money to be detected by utilizing the terahertz signal and the second laser;
and the placing clamp is arranged between the transmitting antenna assembly and the receiving antenna assembly and used for placing the paper money to be tested.
The laser assembly comprises a laser light source, a first optical fiber, an optical fiber collimating lens and a first polaroid, wherein the laser light source, the first optical fiber, the optical fiber collimating lens and the first polaroid are sequentially arranged on a main optical axis of the laser assembly;
the laser light source is used for generating laser, and the transmission direction of the laser is parallel to the main optical axis of the laser component; the first optical fiber is used for compensating the laser; the optical fiber collimating lens is used for collimating the laser passing through the first optical fiber; the first polaroid is used for carrying out polarization processing on the laser passing through the fiber collimating lens.
Wherein, beam split subassembly includes:
the polarization beam splitter is arranged on a main optical axis of the laser assembly and used for reflecting and transmitting the laser passing through the first polaroid so as to generate a first laser and a second laser;
a first mirror for changing a transmission path of the first laser light so that the first laser light is transmitted to the radiation antenna assembly;
the laser delay line is used for delaying the second laser;
a second mirror for changing a transmission path of the second laser light passing through the laser delay line;
and the third reflector is arranged in parallel with the second reflector and is used for further changing the transmission path of the second laser light passing through the second reflector so as to transmit the second laser light to the receiving antenna assembly.
Wherein, the transmitting antenna component comprises a second polaroid, a first fiber coupling lens, a transmitting antenna and a fourth reflector which are arranged on the main optical axis of the first laser in turn,
the second polaroid is used for carrying out polarization processing on the first laser passing through the first reflector; the first optical fiber coupling lens is used for coupling the first laser light passing through the second polarizer to the transmitting antenna; the transmitting antenna receives the first laser, and generates and transmits a terahertz signal by using the first laser; the fourth reflector is used for focusing and collimating the terahertz signal so as to transmit the terahertz signal to the paper money to be detected; the transmission path of the terahertz signal is perpendicular to the surface of the paper money to be detected;
the receiving antenna assembly comprises a third polaroid, a second fiber coupling lens, a receiving antenna and a fifth reflector which are sequentially arranged on the main optical axis of the second laser,
the third polaroid is used for carrying out polarization processing on the second laser passing through the third reflector; the second fiber coupling lens is used for coupling the second laser light passing through the third polarizer to the receiving antenna; the fifth reflector is used for focusing and collimating the terahertz signal passing through the paper money to be detected so as to transmit the terahertz signal to the receiving antenna; and the receiving antenna receives the second laser and the terahertz signal penetrating through the paper money to be detected, and generates a current signal by using the terahertz signal and the second laser.
The terahertz spectrometer further comprises a transimpedance amplifier and a processor, wherein the transimpedance amplifier is connected with the receiving antenna and the processor and is used for converting the current signal into a voltage signal and transmitting the voltage signal to the processor; the processor is used for acquiring the time domain spectral line of the paper money to be detected by using the voltage signal and processing the time domain spectral line to acquire and output the number of the paper money to be detected.
The beneficial effect of this application is: different from the prior art, the number of the paper money to be measured can be obtained according to the preset mathematical model and the relative delay time by obtaining the time domain spectral line of the paper money to be measured and further obtaining the relative delay time based on the time domain spectral line and the reference time domain spectral line, and the number of the paper money to be measured can be rapidly measured by utilizing the time domain delay information of the time domain spectral line.
It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the application.
Drawings
In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings needed to be used in the description of the embodiments are 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 to obtain other drawings based on these drawings without creative efforts.
FIG. 1 is a schematic flow chart of an embodiment of a banknote testing method according to the present application;
FIG. 2 is a detailed flowchart of step S11 in FIG. 1;
FIG. 3 is a detailed flowchart of step S13 in FIG. 1;
FIG. 4 is a detailed flowchart of the process before step S11 in FIG. 1;
FIG. 5 is a detailed flowchart of FIG. 1 after step S14;
FIG. 6 is a schematic structural diagram of an embodiment of a terahertz spectrometer of the present application;
FIG. 7 is a schematic structural diagram of another embodiment of the terahertz spectrometer of the present application;
FIG. 8 is a schematic view of the placement fixture of FIG. 7;
FIG. 9 is a diagram illustrating relative delay time and number of banknotes according to the mathematical model of the present application;
FIG. 10 is a diagram illustrating the relationship between the time difference and the number of banknotes in the mathematical model of the present application;
FIG. 11 is a schematic diagram showing the relationship between the relative delay time and the amplitude of the banknote to be tested according to the present application;
FIG. 12 is a schematic diagram illustrating the relationship between the relative delay time of the banknote to be tested and the number of the banknotes in the present application;
FIG. 13 is a schematic structural diagram of an embodiment of an electronic device provided herein;
FIG. 14 is a schematic structural diagram of an embodiment of a computer-readable storage medium provided in the present application.
Detailed Description
In order to enable those skilled in the art to better understand the technical solution of the present application, the following describes in detail the banknote detection method and the terahertz spectrometer provided in the present application with reference to the accompanying drawings and the detailed description. It is to be understood that the embodiments described are only a few embodiments of the present application and not all 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.
The terms "first", "second", etc. in this application are used to distinguish between different objects and not to describe a particular order. Furthermore, the terms "include" and "have," as well as any variations thereof, are intended to cover non-exclusive inclusions. For example, a process, method, system, article, or apparatus that comprises a list of steps or elements is not limited to only those steps or elements listed, but may alternatively include other steps or elements not listed, or inherent to such process, method, article, or apparatus.
Referring to fig. 1, fig. 1 is a schematic flow chart of an embodiment of a banknote detection method according to the present application. Specifically, the method for detecting banknotes in this embodiment may include the following steps:
step S11: and acquiring a time domain spectral line of the paper money to be detected.
In this embodiment, the banknote to be measured is a banknote with a denomination of 100. In other embodiments, banknotes with other denominations can be used as the banknotes to be measured, for example, 50 denominations, 20 denominations, 10 denominations, and the like; the type of banknote may also be RMB, USD, Euro, etc.
Please refer to fig. 2, in detail, please refer to the process of obtaining the time-domain spectral line of the banknote to be measured, and fig. 2 is a schematic flowchart of step S11 in fig. 1. Specifically, the method comprises the following steps:
step S111: and acquiring a detection area of the paper money to be detected.
In the process of printing the paper money, the content and the times of printing in different areas are different, so that the thickness and the material of the different areas of the paper money are different. The thicker the thickness of the paper money is, the more the terahertz time-domain signal passing through the paper money is attenuated, and the test result is further influenced. Therefore, the embodiment selects the region of the banknote to be detected with the minimum attenuation to the terahertz time-domain signal as the detection region.
Specifically, when a certain number of paper money to be detected is placed on the placing fixture, the detection area of the paper money to be detected is arranged corresponding to the through hole on the placing fixture, so that the terahertz signal sequentially passes through the detection area and the through hole and is transmitted to the lower system.
Step S112: and emitting a terahertz signal to the detection area by utilizing a terahertz spectrometer.
The terahertz spectrometer emits a terahertz signal to a detection area of the paper money to be detected, and the terahertz signal of the paper money to be detected carries time domain information of the paper money to be detected.
Step S113: and acquiring a terahertz signal passing through the paper money to be detected so as to acquire a time-domain spectral line of the paper money to be detected.
The terahertz spectrograph receives the terahertz signal penetrating through the paper money to be detected, so that the time domain information of the paper money to be detected can be obtained, and the time domain spectral line of the paper money to be detected can be generated based on the time domain information of the paper money to be detected.
Specifically, the terahertz spectrometer emits a terahertz signal to the paper money to be detected through a receiving antenna, and the terahertz signal sequentially passes through a detection area and a through hole and is transmitted to the receiving antenna so that the receiving antenna generates a current signal; the receiving antenna converts the current signal into a voltage signal through the trans-group amplifier, the voltage signal is transmitted to the processor, and the processor forms a spectrogram according to the voltage signal, namely, a time-domain spectral line of the paper money to be detected is obtained.
Step S12: and acquiring characteristic parameters based on the time domain spectral line, wherein the characteristic parameters comprise peak values and timestamps corresponding to the peak values.
The processor extracts characteristic parameters of the time domain spectral line to obtain a peak value of the time domain spectral line and a timestamp corresponding to the peak value.
Specifically, a terahertz optical signal passes through paper money to be detected with a certain thickness to generate a main wave peak value and an echo peak value, and the main wave peak value and the echo peak value can be well separated in a time domain spectral line. Therefore, in the embodiment, the main wave peak value is used as a peak value of the time domain spectral line, and the time from the emission of the terahertz signal to the reception of the main wave peak value by the terahertz spectrometer is the timestamp corresponding to the peak value.
Step S13: and acquiring the relative delay time by using the time stamp corresponding to the peak value and the reference time domain spectral line.
In the embodiment, the reference time-domain spectral line is a time-domain spectral line obtained by the terahertz spectrometer when the paper money to be detected is not placed. The processor may obtain a peak value of the reference time domain spectral line and a timestamp corresponding to the peak value.
Please refer to fig. 3 for the process of obtaining the relative delay time, wherein fig. 3 is a schematic flowchart of step S13 in fig. 1. Specifically, the method comprises the following steps:
step S131: and acquiring a reference time domain spectral line before the paper money to be detected is placed.
The reference time-domain spectral line is a time-domain spectral line formed by a terahertz signal output by the terahertz spectrometer when the paper money to be detected is not placed.
Step S132: reference characteristic parameters are obtained based on the reference time-domain spectral lines, wherein the reference characteristic parameters comprise reference peaks and reference timestamps corresponding to the reference peaks.
The processor extracts the reference characteristic parameters of the reference time-domain spectral line to obtain a reference peak value of the reference time-domain spectral line and a reference timestamp corresponding to the reference peak value.
Step S133: relative delay times are obtained using the time stamps and the reference time stamp.
The processor compares the time stamp corresponding to the peak value of the time domain spectral line of the paper money to be detected with the time stamp corresponding to the peak value of the reference time domain spectral line, namely compares the time stamp with the reference time stamp, so that the time delay of the time domain spectral line of the paper money to be detected relative to the reference time domain spectral line can be obtained, the relative time delay time is obtained, and the spectral diagram of the relative time delay time and the relative amplitude is obtained according to the relative time delay time.
For example, in the present embodiment, a test is performed in which five sets of banknotes to be tested with different numbers of banknotes are set, and the test result is a spectral line as shown in fig. 11. Referring to fig. 11, fig. 11 is a schematic diagram of a relationship between a relative delay time and an amplitude of the banknote to be tested according to the present application. As shown in fig. 11, a1, a2, A3, a4 and a5 correspond to five groups of spectral lines of relative delay time and amplitude of the test when different numbers of banknotes to be tested are set. In this embodiment, 10 times of repeated tests are required for each set of tests.
Specifically, as can be seen from FIG. 10, when the A1 group test was performed, the peak values of the time domain spectral lines of the A1 group had relative delay times ranging from 20ps to 21ps and amplitudes ranging from 0.5 to 0.6.
When tested in group A2, the peaks of the time domain spectral lines in group A2 had relative delays ranging from 20ps to 21ps and amplitudes ranging from 0.5 to 0.6.
When tested in group A3, the peaks of the time domain spectral lines in group A3 had relative delays ranging from 20.5ps to 21ps and amplitudes ranging from 0.5 to 0.6.
When tested in group A4, the peaks of the time domain spectral lines in group A4 had relative delays ranging from 20.5ps to 21.5ps and amplitudes ranging from 0.5 to 0.6.
When the A5 group test is performed, the relative delay time range of the peak value of the time domain spectral line of the A5 group is 21ps-21.5ps, and the amplitude range is 0.5-0.6.
Step S14: and inputting the relative delay time into a preset mathematical model, and acquiring the number of the paper money to be detected based on an output result of the preset mathematical model.
The processor is stored with a preset mathematical model in advance, the preset mathematical model comprises the relation between the relative delay time and the number of the paper money, and the number of the paper money to be detected corresponding to the relative delay time can be output by inputting the relative delay time.
For example, the processor may extract the relative delay times corresponding to the peaks in the five groups of tests through the spectral lines shown in fig. 11, and input the relative delay times into a preset mathematical model to obtain the relationship curve shown in fig. 12.
Referring to FIG. 12, FIG. 12 is a schematic diagram illustrating a relationship between a relative delay time of a banknote to be tested and the number of the banknotes according to the present application. As shown in fig. 12, when the group a1 tests were performed, the relative delay time obtained from 10 test results ranged from 20.3ps to 20.43 ps; and the processor inputs the relative delay time obtained by the 10 times of test results into a preset mathematical model in sequence to obtain 98 banknotes to be tested in the A1 group test.
When the A2 group test is carried out, the relative delay time range obtained by 10 times of test results is 20.48ps-20.67 ps; and the processor inputs the relative delay time obtained by the 10 times of test results into a preset mathematical model in sequence to obtain that the number of the paper money to be tested of the A2 group is 99.
When the A3 group test is carried out, the relative delay time range obtained by 10 times of test results is 20.7ps-20.87 ps; and the processor inputs the relative delay time obtained by the 10 times of test results into a preset mathematical model in sequence to obtain that the number of the banknotes to be tested of the A3 group is 100.
When the A4 group test is carried out, the relative delay time range obtained by 10 times of test results is 20.92ps-21.1 ps; and the processor inputs the relative delay time obtained by the 10 times of test results into a preset mathematical model in sequence to obtain that the number of the paper money to be tested of the A4 group is 101.
When the A5 group test is carried out, the relative delay time range obtained by 10 times of test results is 21.2ps-21.32 ps; and the processor inputs the relative delay time obtained by the 10 times of test results into a preset mathematical model in sequence to obtain that the number of the banknotes to be tested of the A4 group is 102.
In summary, during the same set of repeated tests, although the relative delay time obtained by each measurement has a deviation, the deviation is within 0.2 ps.
In the embodiment, the time domain spectral line of the paper money to be measured is obtained, the relative delay time is further obtained based on the time domain spectral line and the reference time domain spectral line, the number of the paper money to be measured can be obtained according to the preset mathematical model and the relative delay time, and the number of the paper money to be measured can be rapidly measured by using the time domain delay information of the time domain spectral line; meanwhile, the terahertz signal has non-ionization property, higher signal-to-noise ratio and shorter time pulse length in the transmission process, so that the terahertz signal can penetrate through the paper money to be measured, the receiving antenna receives the terahertz signal passing through the paper money to be measured so as to obtain a time-domain spectral line of the paper money to be measured, an extra coupling agent is not required to be arranged on the paper money to be measured, the damage to the paper money to be measured is avoided, and non-contact nondestructive measurement is realized.
Optionally, before the banknote detecting method of the present embodiment is executed, a mathematical model may be trained in advance, please refer to fig. 3 for a specific training step, and fig. 3 is a specific flowchart before step S11 in fig. 1. Specifically, the method comprises the following steps:
step S21: and acquiring the paper money with different numbers in the preset group number.
The attenuation rates of the paper money with different denominations to the terahertz signal are different, and the attenuation rates of different areas of the paper money with the same denomination to the terahertz signal are different, so that the paper money with the same denomination as the paper money to be detected is required to be used when a preset mathematical model is trained, and the area which is the same as the detection area of the paper money to be detected is arranged at the through hole for placing the clamp.
Optionally, the present embodiment presets 150 sets of banknotes, and the number of the banknotes corresponds to 1 to 150.
Step S22: and respectively acquiring a first characteristic parameter of each group of paper money by using a terahertz spectrometer, wherein the first characteristic parameter comprises the relative delay time between the time domain spectral line peak value of the group of paper money and the reference time domain spectral line peak value.
Step S23: and training a mathematical model by using the number of the paper money with the preset number and the corresponding relative delay time to obtain a preset mathematical model.
Specifically, in this embodiment, a test is performed from 0 opening, a time domain spectral line corresponding to the time domain spectral line is obtained, and the time domain spectral line is used as a reference spectral line; and successively adding 1 banknote, acquiring the corresponding time domain spectral line, and comparing the peak value of the corresponding time domain spectral line with the peak value of the reference spectral line to obtain the corresponding relative delay time until the number of the banknotes is increased to 150.
The processor performs mathematical model training to obtain a curve S1 shown in FIG. 9 according to the relative delay time and the number of banknotes corresponding to 1-150 banknotes.
Referring to fig. 9, fig. 9 is a diagram illustrating relative delay time and number of banknotes according to the mathematical model of the present application. As shown in fig. 9, S1 is a fitting curve obtained by the mathematical model training performed by the processor, which is specifically shown as a relationship that the relative delay time is proportional to the number of banknotes, that is, as shown in formula 1:
m＝Δt/k (1)
where m is the number of banknotes, Δ t is the relative delay time, and k is the fitting coefficient, which is related to the refractive index of the banknote detection area.
Since the preset mathematical model is obtained by fitting the processor, there is a certain deviation from the data, and a schematic diagram as shown in fig. 10 can be obtained according to the deviation of the corresponding fitting data and the experimental data.
Referring to fig. 10, fig. 10 is a schematic diagram illustrating a relationship between a time difference and the number of banknotes in the mathematical model of the present application. As shown in fig. 10, in the actual test, the delay time added for each additional banknote is the same; the delay time increases in steps for each additional note according to the fitted data curve S2. However, the difference between the time difference of 0 sheets and the time difference of 150 sheets is less than 0.025ps, which is negligible, and the predetermined mathematical model obtained by fitting can be considered to be correct.
Optionally, after acquiring the number of the banknotes to be tested, corresponding steps may be further performed to check the reliability of the result, please refer to fig. 5 for the specific checking step, and fig. 5 is a specific flowchart after step S14 in fig. 1. Specifically, the method comprises the following steps:
step S31: and acquiring the corresponding preset relative delay time of the quantity based on the preset mathematical model.
Step S32: and acquiring the time difference between the preset relative delay time and the relative delay time.
After acquiring the number of the banknotes to be detected, the processor searches for the preset relative delay time corresponding to the number of the banknotes according to the curve S1 shown in fig. 10, and acquires the time difference between the preset relative delay time and the relative delay time.
Step S33: and judging whether the time difference is within a preset time difference range.
In this embodiment, the predetermined time difference may be 0.025 ps.
The processor determines whether the time difference is within a predetermined time difference range, if so, performs step S34, otherwise, performs step S35.
Step S34: and judging the quantity to be an accurate value.
When the processor judges that the time difference is within the preset time difference range, the judgment number is an accurate value, and information for confirming accuracy is output.
Step S35: the number is judged to be an inaccurate value.
When the processor judges that the time difference is out of the preset time difference range, the judgment number is an inaccurate value, and error confirmation information is output to prompt a user to measure again.
To implement the above-mentioned detection method, the present application further provides a terahertz spectrometer, please continue to refer to fig. 6, where fig. 6 is a schematic structural diagram of an embodiment of the terahertz spectrometer of the present application. As shown in fig. 6, the terahertz spectrometer 1 includes a laser assembly 10, a light splitting assembly 20, a transmitting antenna assembly 30, a placing jig 40, and a receiving antenna assembly 50.
Wherein the laser assembly 10 is used to generate laser light.
The light splitting assembly 20 is disposed on a main optical axis of the laser assembly 10, and is configured to split laser light generated by the laser assembly 10 to generate first laser light and second laser light.
The transmitting antenna assembly 30 is connected to the light splitting assembly 20, and is configured to receive the first laser light, generate and transmit a terahertz signal using the first laser light.
The receiving antenna assembly 50 is connected to the light splitting assembly 20, and is configured to receive the second laser and the terahertz signal that passes through the paper money to be detected, and generate a time-domain spectral line of the paper money to be detected by using the terahertz signal and the second laser.
The placing clamp 40 is arranged between the transmitting antenna assembly 30 and the receiving antenna assembly 50 and is used for placing paper money to be tested; the terahertz signal penetrates through the paper money to be detected so as to generate a time-domain spectral line of the paper money to be detected.
In the terahertz spectrometer 1, the laser component 10 excites the emission antenna component 30 to emit terahertz light to measure the paper money to be measured arranged on the placing clamp 40, and a coupling agent is not required to be additionally arranged, so that the damage to the paper money to be measured is avoided; meanwhile, the terahertz light has non-ionization property, higher signal-to-noise ratio and shorter time pulse length, can realize rapid measurement of the number of paper money to be measured, and reduces damage to human bodies.
Referring further to fig. 6 and 7, fig. 7 is a schematic structural diagram of another embodiment of the terahertz spectrometer of the present application. As shown in fig. 7, the laser module 10 includes a laser light source 11, a first optical fiber 12, a fiber collimating lens 13, and a first polarizer 14, which are sequentially disposed on a main optical axis of the laser module 10.
The laser light source 11 is configured to generate laser light, and a transmission direction of the laser light is parallel to a main optical axis of the laser assembly 10. Specifically, the laser light source 11 may be a femtosecond laser, and the femtosecond laser is connected to the first optical fiber 12 through a flange. Alternatively, in other embodiments, the laser light source 11 may be other light sources capable of generating laser light.
The first optical fiber 12 is used to compensate the laser light generated by the laser light source 11. Specifically, the first optical fiber 12 is a dispersion compensation fiber, and since laser light is easily dispersed in long-distance transmission, the first optical fiber 12 is disposed in the laser light path in the present embodiment to compensate for the dispersed laser light.
The fiber collimating lens 13 is connected to the first optical fiber 12 and is configured to collimate the laser light passing through the first optical fiber 12.
The first polarizer 14 is used to polarize the laser light passing through the fiber collimator lens 13. Specifically, the first polarizer 14 is a λ/4 polarizer. Alternatively, in other embodiments, the first polarizer 14 may be selected from a λ/2 polarizer or other polarizers, as desired.
The light splitting assembly 20 further includes a polarizing beam splitter 21, a first mirror 22, a laser delay line 23, a second mirror 24, and a third mirror 25.
The polarization beam splitter 21 is disposed on a main optical axis of the laser assembly 10, and is configured to reflect and transmit the laser light passing through the first polarizer 14 to generate the first laser light and the second laser light. Specifically, the polarizing beam splitter 21 may be a beam splitter prism.
The first mirror 22 is used to change the transmission path of the first laser light so that the first laser light is transmitted to the radiating antenna assembly 30 to excite the radiating antenna assembly 30 to operate. The first reflecting mirror 22 is arranged at an angle of 45 degrees with the transmission direction of the first laser, and after the first laser is reflected by the first reflecting mirror 22, the transmission direction of the first laser is parallel to the transmission direction of the laser.
The laser delay line 23 is disposed on the main optical axis of the laser module 10, and is used for delaying the second laser.
The second mirror 24 is used to change the transmission path of the second laser light passing through the laser delay line 23. Wherein the second mirror 24 is disposed at 45 ° to the transmission direction of the second laser light passing through the laser delay line 23.
The third mirror 25 is disposed in parallel with the second mirror 24 for further changing the transmission path of the second laser light passing through the second mirror 24 so that the second laser light is transmitted to the receiving antenna assembly 50 to excite the receiving antenna assembly 50 to operate. After the second laser is reflected by the third reflector 25, the transmission direction of the second laser is parallel to the transmission direction of the laser and the transmission direction of the first laser.
Optionally, in the present embodiment, the first mirror 22, the second mirror 24, and the third mirror 25 may be plane mirrors.
The radiation antenna assembly 30 includes a second polarizer 31, a first fiber coupling lens 32, a radiation antenna 33, and a fourth mirror 34, which are sequentially disposed on the main optical axis of the first laser light. Optionally, the main optical axis of the first laser light and the main optical axis of the laser assembly 10 are parallel to each other.
The second polarizing plate 31 is used to polarize the first laser light passing through the first reflecting mirror 22. Specifically, the second polarizing plate 31 is a λ/2 polarizing plate.
The first fiber coupling lens 32 is used to couple the first laser light passing through the second polarizer 31 to the transmitting antenna 33. Alternatively, in this embodiment, the first fiber coupling lens 32 may include a coupling fiber and a coupling lens, the first laser light is coupled into the coupling fiber through the coupling lens, and the transmitting antenna 33 is connected through the coupling fiber.
The transmitting antenna 33 receives the first laser, is excited by the first laser, and the transmitting antenna 33 starts to work and emits terahertz light.
The fourth mirror 34 is used to focus and collimate the terahertz light so that the terahertz light is transmitted to the paper money to be measured disposed on the placing jig 40. The transmission path of the terahertz light is perpendicular to the surface of the paper money to be detected.
The receiving antenna assembly 50 includes a third polarizer 51, a second fiber coupling lens 52, a receiving antenna 53, and a fifth mirror 54, which are sequentially disposed on the main optical axis of the second laser light. Optionally, the main optical axis of the second laser and the main optical axis of the laser assembly 10 are parallel to each other.
The third polarizing plate 51 is for polarizing the second laser light passing through the third reflecting mirror 25. Specifically, the third polarizing plate 51 is a λ/2 polarizing plate.
The second fiber coupling lens 52 is used to couple the second laser light passing through the third polarizer 51 to the receiving antenna 53. Alternatively, in this embodiment, the second fiber coupling lens 52 may include a coupling fiber and a coupling lens, the second laser light is coupled into the coupling fiber through the coupling lens, and the receiving antenna 53 is connected through the coupling fiber.
The fifth mirror 54 is used to focus and collimate the terahertz light passing through the paper money to be measured, so that the terahertz light is transmitted to the receiving antenna 53.
The receiving antenna 53 receives the second laser light, and the receiving antenna 53 starts to operate when excited by the second laser light. The receiving antenna 53 receives the terahertz signal passing through the paper money to be measured, and generates a current signal from the second laser and the terahertz signal.
Specifically, the fourth reflector 34 and the fifth reflector 54 are off-axis parabolic mirrors, focal lengths are both 50mm, a distance between the fourth reflector 34 and the fifth reflector 54 is 100mm, and an area between the fourth reflector 34 and the fifth reflector 54 is a detection area for setting the placing fixture 40.
Alternatively, in other embodiments, the focal length of the fourth mirror 34 and the fifth mirror 54 may be 60mm or 40mm, and the distance between the fourth mirror 34 and the fifth mirror 54 may be 120mm or 80 mm.
Referring further to fig. 8 in conjunction with fig. 7, fig. 8 is a schematic structural view of the placement fixture of fig. 7. As shown in fig. 8, the placing jig 40 includes a body 41 and a through hole 42 provided on the body 41, and the through hole 42 is provided on the upper right of the center of the body 41. When the paper money to be tested is set on the placing jig 40, the detection area of the paper money to be tested is set corresponding to the through hole 42.
Alternatively, in the present embodiment, the banknote to be measured uses a 100-denomination banknote, the size of the banknote is the same as that of the placement jig 40, and the attenuation rate of the terahertz light is the smallest in the region above and to the right of the center of the 100-denomination banknote. Therefore, when the banknote to be tested is set on the setting jig 40, the area of the banknote with the denomination of 100, which is on the upper right side from the center, is just set corresponding to the through hole 42.
Alternatively, in another embodiment, the measurement may be performed using 50 denomination, 20 denomination, 10 denomination, or the like banknotes, and since 50 denomination, 20 denomination, or the like banknotes are different in size from 100 denomination banknotes, when placing the banknotes, it is necessary to manually adjust the positions of 50 denomination, 20 denomination, or the like banknotes so that the corresponding regions having the smallest attenuation rate against terahertz light are provided in correspondence with the through holes 42.
As shown in fig. 7, the terahertz spectrometer 1 further includes a transimpedance amplifier 60 and a processor 70, the transimpedance amplifier 60 is connected to the receiving antenna 53 and the processor 70, and is configured to convert the current signal of the receiving antenna 53 into a voltage signal and transmit the voltage signal to the processor 70; the processor 70 is configured to obtain a time-domain spectral line of the paper money to be tested by using the voltage signal, process the time-domain spectral line to obtain a relative delay time, input the relative delay time into a preset mathematical model, and output the number of the paper money to be tested according to an output result of the preset mathematical model.
To implement the above method for detecting paper money, the present application further provides an electronic device, please refer to fig. 13, where fig. 13 is a schematic structural diagram of an embodiment of the electronic device provided in the present application. The electronic device 80 comprises a memory 81 and a processor 82 coupled to each other, the processor 82 being configured to execute program instructions stored in the memory 81 to implement the steps in any of the above-described embodiments of the banknote detection method. In one particular implementation scenario, the electronic device 80 may include, but is not limited to: a microcomputer, a server, and the electronic device 80 may also include a mobile device such as a notebook computer, a tablet computer, and the like, which is not limited herein.
In particular, the processor 82 is configured to control itself and the memory 81 to implement the steps in any of the above-described embodiments of the banknote detection method. The processor 82 may also be referred to as a CPU (Central Processing Unit). The processor 82 may be an integrated circuit chip having signal processing capabilities. The Processor 82 may also be a general purpose Processor, a Digital Signal Processor (DSP), an Application Specific Integrated Circuit (ASIC), a Field Programmable Gate Array (FPGA) or other Programmable logic device, discrete Gate or transistor logic, discrete hardware components. A general purpose processor may be a microprocessor or the processor may be any conventional processor or the like. In addition, the processor 82 may be collectively implemented by an integrated circuit chip.
In order to realize the detection method of the paper money, the application also provides a computer readable storage medium. Referring to fig. 14, fig. 14 is a schematic structural diagram of an embodiment of a computer-readable storage medium provided in the present application. The computer readable storage medium 90 stores program instructions 91 executable by the processor, the program instructions 91 for implementing the steps in any of the banknote detection method embodiments described above.
In some embodiments, functions of or modules included in the apparatus provided in the embodiments of the present disclosure may be used to execute the method described in the above method embodiments, and specific implementation thereof may refer to the description of the above method embodiments, and for brevity, will not be described again here.
The foregoing description of the various embodiments is intended to highlight various differences between the embodiments, and the same or similar parts may be referred to each other, and for brevity, will not be described again herein.
In the several embodiments provided in the present application, it should be understood that the disclosed method and apparatus may be implemented in other ways. For example, the above-described apparatus embodiments are merely illustrative, and for example, a division of a module or a unit is merely one type of logical division, and an actual implementation may have another division, for example, a unit or a component may be combined or integrated with another system, or some features may be omitted, or not implemented. In addition, the shown or discussed mutual coupling or direct coupling or communication connection may be an indirect coupling or communication connection of devices or units through some interfaces, and may be in an electrical, mechanical or other form.
In addition, functional units in the embodiments of the present application may be integrated into one processing unit, or each unit may exist alone physically, or two or more units are integrated into one unit. The integrated unit can be realized in a form of hardware, and can also be realized in a form of a software functional unit.
The integrated unit, if implemented in the form of a software functional unit and sold or used as a stand-alone product, may be stored in a computer readable storage medium. Based on such understanding, the technical solution of the present application may be substantially implemented or contributed to by the prior art, or all or part of the technical solution may be embodied in a software product, which is stored in a storage medium and includes instructions for causing a computer device (which may be a personal computer, a server, or a network device) or a Processor (Processor) to execute all or part of the steps of the method according to the embodiments of the present application. And the aforementioned storage medium includes: a U-disk, a removable hard disk, a Read-Only Memory (ROM), a Random Access Memory (RAM), a magnetic disk or an optical disk, and other various media capable of storing program codes.
Claims (10)
1. A method of detecting a banknote, the method comprising:
acquiring a time domain spectral line of the paper money to be detected;
acquiring characteristic parameters based on the time-domain spectral lines, wherein the characteristic parameters comprise peak values and timestamps corresponding to the peak values;
acquiring relative delay time by using the timestamp corresponding to the peak value and a reference time domain spectral line;
and inputting the relative delay time into a preset mathematical model, and acquiring the number of the paper money to be detected based on an output result of the preset mathematical model.
2. The detection method according to claim 1,
the acquiring of the time domain spectral line of the paper money to be detected comprises the following steps:
acquiring a detection area of the paper money to be detected, wherein the detection area of the paper money to be detected is arranged corresponding to a through hole on a placing clamp for placing the paper money to be detected;
emitting a terahertz signal to the detection area by using a terahertz spectrometer;
and acquiring a terahertz signal passing through the paper money to be detected so as to acquire a time-domain spectral line of the paper money to be detected.
3. The detection method according to claim 1,
the obtaining of the relative delay time by using the timestamp corresponding to the peak value and the reference time domain spectral line includes:
acquiring a reference time domain spectral line before the paper money to be detected is placed;
acquiring reference characteristic parameters based on the reference time domain spectral lines, wherein the reference characteristic parameters comprise reference peaks and reference timestamps corresponding to the reference peaks;
and acquiring the relative delay time by using the time stamp and the reference time stamp.
4. The detection method according to claim 1,
before the time domain spectral line of the paper money to be detected is obtained, the method comprises the following steps:
acquiring paper money with different numbers of preset groups;
respectively utilizing the terahertz spectrograph to obtain a first characteristic parameter of each group of paper money, wherein the first characteristic parameter comprises the relative delay time between the time domain spectral line peak value of the group of paper money and the reference time domain spectral line peak value;
and training a mathematical model by using the number of the paper money with the preset number and the corresponding relative delay time to obtain the preset mathematical model.
5. A terahertz spectrometer is characterized by being used for realizing the detection method of any one of claims 1-4.
6. The terahertz spectrometer of claim 5, further comprising:
a laser assembly for generating laser light;
the light splitting assembly is arranged on a main optical axis of the laser assembly and is used for splitting the laser to generate a first laser and a second laser;
the transmitting antenna assembly is connected with the light splitting assembly and used for receiving the first laser and generating and transmitting a terahertz signal by using the first laser;
the receiving antenna assembly is connected with the light splitting assembly and used for receiving the second laser and a terahertz signal penetrating through the paper money to be detected and generating a time-domain spectral line of the paper money to be detected by using the terahertz signal and the second laser;
and the placing clamp is arranged between the transmitting antenna assembly and the receiving antenna assembly and used for placing the paper money to be tested.
7. The terahertz spectrometer of claim 6, wherein the laser assembly comprises a laser light source, a first optical fiber, a fiber collimating lens and a first polarizer, which are sequentially arranged on a main optical axis of the laser assembly;
the laser light source is used for generating laser, and the transmission direction of the laser is parallel to the main optical axis of the laser component; the first optical fiber is used for compensating the laser; the optical fiber collimating lens is used for collimating the laser passing through the first optical fiber; the first polaroid is used for carrying out polarization processing on the laser passing through the fiber collimating lens.
8. The terahertz spectrometer of claim 7, wherein the spectroscopy assembly comprises:
the polarization beam splitter is arranged on a main optical axis of the laser assembly and is used for reflecting and transmitting the laser passing through the first polaroid so as to generate a first laser and a second laser;
a first mirror for changing a transmission path of the first laser light so that the first laser light is transmitted to the transmitting antenna assembly;
the laser delay line is used for delaying the second laser;
a second mirror for changing a transmission path of the second laser light passing through the laser delay line;
and the third reflector is arranged in parallel with the second reflector and is used for further changing the transmission path of the second laser light passing through the second reflector so as to transmit the second laser light to the receiving antenna assembly.
9. The terahertz spectrometer of claim 8,
the transmitting antenna component comprises a second polaroid, a first optical fiber coupling lens, a transmitting antenna and a fourth reflector which are arranged on the main optical axis of the first laser in sequence,
the second polaroid is used for carrying out polarization processing on the first laser passing through the first reflector; the first optical fiber coupling lens is used for coupling the first laser light passing through the second polarizer to the transmitting antenna; the transmitting antenna receives the first laser, and generates and transmits a terahertz signal by using the first laser; the fourth reflector is used for focusing and collimating the terahertz signal so as to transmit the terahertz signal to the paper money to be detected; the transmission path of the terahertz signal is perpendicular to the surface of the paper money to be detected;
the receiving antenna assembly comprises a third polaroid, a second fiber coupling lens, a receiving antenna and a fifth reflector which are sequentially arranged on the main optical axis of the second laser,
the third polarizer is used for carrying out polarization processing on the second laser passing through the third reflector; the second fiber coupling lens is used for coupling the second laser light passing through the third polarizer to the receiving antenna; the fifth reflector is used for focusing and collimating the terahertz signal passing through the paper money to be detected so as to transmit the terahertz signal to the receiving antenna; and the receiving antenna receives the second laser and a terahertz signal penetrating through the paper money to be detected, and generates a current signal by using the terahertz signal and the second laser.
10. The terahertz spectrometer of claim 9, further comprising a transimpedance amplifier and a processor, wherein the transimpedance amplifier is connected to the receiving antenna and the processor, and is configured to convert the current signal into a voltage signal and transmit the voltage signal to the processor; the processor is used for acquiring the time domain spectral line of the paper money to be detected by using the voltage signal, and processing the time domain spectral line to acquire and output the number of the paper money to be detected.
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