Patent Application
20210231568
This application claims priority of Chinese Patent Application No. 201711442583.3 filed on Dec. 26, 2017 in the State Intellectual Property Office of China, the disclosure of which is incorporated herein by reference.
Embodiments of the present disclosure relate to the field of spectrum detection, and in particular to a method for inspecting the security of an object to be detected and an apparatus for inspecting the security of an object to be detected.
Spectrum analysis technologies, such as Raman spectrum analysis technology, fluorescence spectrum analysis technology, etc., are widely used for substance detection and analysis. Raman spectrum analysis technology is one of the non-contact spectrum analysis technologies based on Raman scattering effects. It can analyse the compositions of substances qualitatively and quantitatively. The Raman spectrum is one of the molecular vibration spectra. It may represent fingerprint features of molecules for inspection of substances and can be used for inspection of substances. Raman spectrum inspection can inspect and recognize substances by detecting Raman spectra produced by the Raman scattering effects of an object to be inspected to an exciting light. The Raman spectrum inspection method has been broadly used in various fields, such as liquid security inspection, gem inspection, explosive inspection, drug inspection, medicine inspection.
In recent years, Raman spectrum analysis technology has been widely applied in fields such as inspection of hazardous articles and recognition of substances. In the field of recognition of substances, people often cannot judge properties of the substances correctly as various substances have different colors and shapes. The Raman spectrum depends on the energy level structure of molecules of the object to be detected. Thus, the Raman spectrum may be used as “fingerprint” information of substances for recognizing substances. Therefore, the Raman spectrum analysis technology has been applied broadly in fields such as customs, common security, foods, drugs, environments.
In an actual spectrum analysis, it is often necessary to use exciting light with a certain energy, and since compositions of the object to be detected are often unknown, there is a certain risk of damage (such as ignition and ablation) of the object to be detected. This risk is currently only guarded by a user's pre-observation.
The present application is directed to a method and an apparatus for inspecting security of an object to be detected by spectrum analysis, which is capable of effectively avoiding the risk of inspection due to damage of the object by an exciting light in spectral signal collection.
An embodiment of the present invention provides a method for inspecting security of an object to be detected, including: guiding an exciting light to the object, collecting a first optical signal from the object and generating a first spectrum from the first optical signal; guiding the exciting light to the object again after a predetermined time interval, collecting a second optical signal from the object and generating a second spectrum from the second optical signal; and comparing the first spectrum with the second spectrum to determine whether or not the object is damaged.
In an embodiment, the comparing the first spectrum with the second spectrum to determine whether or not the object is damaged includes: comparing an overall integrated intensity of the first spectrum with an overall integrated intensity of the second spectrum to obtain a difference between the overall integrated intensity of the first spectrum and the overall integrated intensity of the second spectrum; determining that the object is damaged in response to a condition where the difference between the overall integrated intensity of the first spectrum and the overall integrated intensity of the second spectrum exceeds a first threshold, and determining that the object is not damaged in response to a condition where the difference between the overall integrated intensity of the first spectrum and the overall integrated intensity of the second spectrum does not exceed the first threshold.
In an embodiment, the comparing the first spectrum with the second spectrum to determine whether or not the object is damaged includes: extracting a fluorescent envelope of the first spectrum and a fluorescent envelope of the second spectrum, respectively; and comparing the fluorescent envelope of the first spectrum with the fluorescent envelope of the second spectrum to determine whether or not the object is damaged.
In an embodiment, the comparing the fluorescent envelope of the first spectrum with the fluorescent envelope of the second spectrum to determine whether or not the object is damaged includes: detecting a position and an intensity of one or more peaks in the fluorescent envelope of the first spectrum to obtain one or more first reference fluorescent intensities; detecting an intensity at a position in the fluorescent envelope of the second spectrum corresponding to the position of the one or more peaks to obtain one or more second reference fluorescent intensities; determining that the object is damaged in response to a condition where a difference between the first reference fluorescent intensity and the second reference fluorescent intensity exceeds a second threshold, and determining that the object is not damaged in response to a condition where the difference between the first reference fluorescent intensity and the second reference fluorescent intensity does not exceed the second threshold.
In an embodiment, the comparing the first spectrum with the second spectrum to determine whether or not the object is damaged includes: extracting a Raman spectral characteristic peak in the first spectrum and a Raman spectral characteristic peak in the second spectrum, respectively; comparing a position of the Raman spectral characteristic peak in the first spectrum with a position of the Raman spectral characteristic peak in the second spectrum, and determining that the object is damaged in response to a condition where a difference between the position of the Raman spectral characteristic peak in the first spectrum and the position of the Raman spectral characteristic peak in the second spectrum exceeds a third threshold.
In an embodiment, the comparing the first spectrum with the second spectrum to determine whether or not the object is damaged includes: extracting a Raman spectral characteristic peak in the first spectrum and a Raman spectral characteristic peak in the second spectrum, respectively; comparing an intensity of the Raman spectral characteristic peak in the first spectrum with an intensity of the Raman spectral characteristic peak in the second spectrum, and determining that the object is damaged in response to a condition where a difference between the intensity of the Raman spectral characteristic peak in the first spectrum and the intensity of the Raman spectral characteristic peak in the second spectrum exceeds a fourth threshold.
In an embodiment, the comparing the first spectrum with the second spectrum to determine whether or not the object is damaged includes: calculating a similarity between the first spectrum and the second spectrum, and determining that the object is damaged in response to a condition where the similarity between the first spectrum and the second spectrum is less than a fifth threshold, and determining that the object is not damaged in response to a condition where the similarity between the first spectrum and the second spectrum is not less than the fifth threshold.
In an embodiment, the comparing the first spectrum with the second spectrum to determine whether or not the object is damaged includes: comparing an overall integrated intensity of the first spectrum with an overall integrated intensity of the second spectrum to obtain a difference between the overall integrated intensity of the first spectrum and the overall integrated intensity of the second spectrum; determining that the object is damaged in response to a condition where the difference between the overall integrated intensity of the first spectrum and the overall integrated intensity of the second spectrum exceeds a first threshold, and performing the following steps in response to a condition where the difference in overall integrated intensity does not exceed the first threshold: extracting a fluorescent envelope of the first spectrum and a fluorescent envelope of the second spectrum, respectively; detecting a position and an intensity of one or more peaks in the fluorescent envelope of the first spectrum to obtain one or more first reference fluorescent intensities; detecting an intensity at a position in the fluorescent envelope of the second spectrum corresponding to the position of the one or more peaks to obtain one or more second reference fluorescent intensities; determining that the object is damaged in response to a condition where a difference between the first reference fluorescent intensity and the second reference fluorescent intensity exceeds a second threshold, and performing the following steps in response to a condition where the difference between the first reference fluorescent intensity and the second reference fluorescent intensity does not exceed the second threshold: extracting a Raman spectral characteristic peak in the first spectrum and a Raman spectral characteristic peak in the second spectrum, respectively; comparing a position of the Raman spectral characteristic peak in the first spectrum with a position of the Raman spectral characteristic peak in the second spectrum, and determining that the object is damaged in response to a condition where a difference between the position of the Raman spectral characteristic peak in the first spectrum and the position of the Raman spectral characteristic peak in the second spectrum is greater than a third threshold.
In an embodiment, the comparing the first spectrum with the second spectrum to determine whether or not the object is damaged includes: comparing an overall integrated intensity of the first spectrum with an overall integrated intensity of the second spectrum to obtain a difference between the overall integrated intensity of the first spectrum and the overall integrated intensity of the second spectrum; determining that the object is damaged in response to a condition where the difference between the overall integrated intensity of the first spectrum and the overall integrated intensity of the second spectrum exceeds a first threshold, and performing the following steps in response to a condition where the difference between the overall integrated intensity of the first spectrum and the overall integrated intensity of the second spectrum does not exceed the first threshold: extracting a fluorescent envelope of the first spectrum and a fluorescent envelope of the second spectrum, respectively; detecting a position and an intensity of one or more peaks in the fluorescent envelope of the first spectrum to obtain one or more first reference fluorescent intensities; detecting an intensity at a position in the fluorescent envelope of the second spectrum corresponding to the position of the one or more peaks to obtain one or more second reference fluorescent intensities; determining that the object is damaged in response to a condition where a difference between the first reference fluorescent intensity and the second reference fluorescent intensity exceeds a second threshold, and performing the following steps in response to a condition where the difference between the first reference fluorescent intensity and the second reference fluorescent intensity does not exceed the second threshold: extracting a Raman spectral characteristic peak in the first spectrum and a Raman spectral characteristic peak in the second spectrum, respectively; comparing an intensity of the Raman spectral characteristic peak in the first spectrum with an intensity of the Raman spectral characteristic peak in the second spectrum, and determining that the object is damaged in response to a condition where a difference between the intensity of the Raman spectral characteristic peak in the first spectrum and the intensity of the Raman spectral characteristic peak in the second spectrum is greater than a fourth threshold.
In an embodiment, the comparing the first spectrum with the second spectrum to determine whether or not the object is damaged includes: comparing an overall integrated intensity of the first spectrum with an overall integrated intensity of the second spectrum to obtain a difference between the overall integrated intensity of the first spectrum and the overall integrated intensity of the second spectrum; determining that the object is damaged in response to a condition where the difference between the overall integrated intensity of the first spectrum and the overall integrated intensity of the second spectrum exceeds a first threshold, and performing the following steps in response to a condition where the difference between the overall integrated intensity of the first spectrum and the overall integrated intensity of the second spectrum does not exceed the first threshold: extracting a fluorescent envelope of the first spectrum and a fluorescent envelope of the second spectrum, respectively; detecting a position and an intensity of one or more peaks in the fluorescent envelope of the first spectrum to obtain one or more first reference fluorescent intensities; detecting an intensity at a position in the fluorescent envelope of the second spectrum corresponding to the position of the one or more peaks to obtain one or more second reference fluorescent intensities; determining that the object is damaged in response to a condition where a difference between the first reference fluorescent intensity and the second reference fluorescent intensity exceeds a second threshold, and performing the following steps in response to a condition where the difference between the first reference fluorescent intensity and the second reference fluorescent intensity does not exceed the second threshold: calculating a similarity between the first spectrum and the second spectrum, and determining that the object is damaged in response to a condition where the similarity between the first spectrum and the second spectrum is less than a fifth threshold, and determining that the object is not damaged in response to a condition where the similarity between the first spectrum and the second spectrum is not less than the fifth threshold.
In an embodiment, the exciting light is achieved by at least one set of laser pulses, and the exciting light has an energy ranging between 0.1 millijoule and 0.5 millijoule.
In an embodiment, the predetermined time interval is greater than or equal to 500 milliseconds.
In an embodiment, the exciting light configured to generate the first optical signal and the exciting light configured to generate the second optical signal are equal in power.
An embodiment of the present invention also provides an apparatus for inspecting security of an object to be detected, including: a laser device configured to emit an exciting light; an optical device configured to guide the exciting light to the object and collect an optical signal from the object; a spectrometer configured to split the optical signal from the optical device to generate a spectrum of the object; and an object state determining device configured to receive the spectrum from the spectrometer and compare the spectra which are respectively generated from the optical signals collected from the same object at least twice so as to determine whether or not the object is damaged.
In an embodiment, the object state determining device includes a first module configured to compare overall intensities of the spectra which are respectively generated from the optical signals collected from the same object at least twice.
In an embodiment, the object state determining device includes a second module configured to compare fluorescent envelopes of the spectra which are respectively generated from the optical signals collected from the same object at least twice.
In an embodiment, the object state determining device includes a third module configured to compare Raman spectral characteristics of the spectra which are respectively generated from the optical signals collected from the same object at least twice.
In an embodiment, the object state determining device includes a fourth module configured to calculate a similarity of spectrum signals which are respectively collected from the same object at least twice.
In an embodiment, the apparatus further includes: an exciting light modulation module configured to modulate the exciting light into at least two sets of laser pulses having a time interval greater than or equal to 500 milliseconds.
By means of the method and apparatus for inspecting security of the object to be detected according to the above embodiments, risk due to a sharp reaction of the object with the exciting light can be reduced or prevented.
All of circuits or structures of the apparatus for inspecting security of the object to be detected according to embodiments of the present invention are not shown in Figures. Same reference numerals represent same or similar components or features throughout all of Figures.
Technical solutions of the present disclosure will be described hereinafter in more detail by the way of embodiments with reference to the attached drawings. The same or similar reference numerals refer to the same or similar elements throughout the description. The explanation of the embodiments of the present disclosure with reference to the attached drawings is intended to interpret the general concept of the present disclosure, rather than being construed as a limiting to the present disclosure.
In addition, in the following detailed description, for purposes of explanation, numerous specific details are set forth in order to provide a thorough understanding of the disclosed embodiments. It will be apparent, however, that one or more embodiments may be practiced without these specific details. In other instances, well-known structures and devices are schematically shown in order to simplify the drawing.
As mentioned above, the use of exciting light to acquire optical signals is a fundamental step in the spectrum analysis of an object to be detected. As the exciting light itself has a certain energy, it may react with an object which is formed of one or more certain materials, thereby leading to changes in composition of the object. For example, some flammable and explosive materials may be ignited, ablated or exploded under the action of exciting light. In practice, as the compositions of objects to be detected are often unknown, it is necessary to inspect security of the object prior to formal light signal acquisition and measurement, so as to determine whether or not the object to be detected is suitable for laser detection/Raman spectrum detection. The term “security” as used herein has two meanings. In one meaning, the object to be detected may cause danger to spectrum inspection instruments and operators as it is ignited, ablated or exploded. In the other meaning, the changes in composition due to the reaction between the exciting light and the object to be detected may result in unpredictable deviation in a detection result and then result in failure of object inspection.
In order to inspect the security of the object to be detected, an embodiment of the present invention provides a method 100 for inspecting security of an object to be detected. In an embodiment, as shown in
step S10: guiding exciting light to the object to be detected, collecting a first optical signal from the object and generating a first spectrum from the first optical signal;
step S20: guiding exciting light to the object again after a predetermined time interval, collecting a second optical signal from the object and generating a second spectrum from the second optical signal; and
step S30: comparing the first spectrum with the second spectrum to determine whether or not the object is damaged.
By means of the above method, two spectra of the same object may be obtained by two measurements separated by the predetermined time interval. The two measurements aim to determine whether or not the object is suitable for laser detection/Raman spectrum inspection, so the duration of pulses emitted by the exciting light in these two measurements are shorter than the duration of pulses emitted by the exciting light in the normal Raman spectrum inspection/laser detection, and the energy of pulses emitted by the exciting light in these two measurements are less than the energy of pulses emitted by the exciting light in the normal Raman spectrum inspection/laser detection, thereby avoiding accidents such as explosions. By comparing the two spectra obtained from the two measurements, it can be determined whether or not there is change in the composition of the object after it is irradiated with the exciting light. It will be understood by those skilled in the art that there are usually certain changes in the composition whether the object is ignited, ablated, exploded, or otherwise reacted with the exciting light. In particular, when the energy of the exciting light is small and the reaction is not severe, the composition has often been changed. The spectra corresponding to different compositions are also different. Therefore, by comparing the above two spectra, it can be known whether or not the composition of the object has been changed, that is, whether or not the object has been damaged. If the object is not damaged, it is proved that the object can be normally analyzed and inspected on the basis of a spectrum. If the object has been changed or damaged, the object needs to be re-evaluated instead of continuing the normal spectrum analysis and inspection. For example, another inspection method without using exciting light may be selected to inspect the object.
As an example, in the above steps S10 and S20, the irradiation time of each exciting light may be relatively short, for example, within a range of from 0.5 milliseconds to 5 milliseconds, so as to prevent the exciting light having excessively large energy which may otherwise react with certain objects to be detected to cause a danger. The predetermined time interval may be relatively long, for example, greater than or equal to 500 milliseconds, so as to avoid any accumulation effect (primarily referring to the accumulation of generated heat) of two irradiations of the exciting light. For security reasons, the irradiation energy of each exciting light typically in the above steps S10 and S20 is less than or much less than the energy of the exciting light in the normal spectrum inspection. As an example, in practice, the above two signal collections may be initiated by generating two or two sets of laser pulses having the above predetermined time interval as the exciting light. In this way, it is not necessary to move or replace the object or re-adjust the inspection apparatus, thus the operation is relatively easy.
Specific examples of the energy of the exciting light are given below:
It is assumed that the specific heat capacity of the object to be detected is 1 KJ/kg° C., the density thereof is 2 g/cm3, the irradiation spot diameter of the exciting light is 100 μm, the irradiation depth of the exciting light is 100 μm, and the temperature rise due to the exciting light irradiation is 100° C. According to the formula “absorbed heat=specific heat capacity of the object×temperature rise×mass of a portion of the object irradiated by the exciting light”, it can be calculated that the total heat absorbed by the object is about 0.16 mJ. According to the absorption rate of 80%, the irradiation energy required for each exciting light is 0.2 mJ. If the exciting light is achieved by a laser pulse from a 200 mW laser, each pulse width is about 1 millisecond. For some flammable substances, such as charcoal, the specific heat capacity is 0.8 KJ/kg° C., the density is 0.4 g/cm3, and the ignition point is about 300° C. According to the calculation similar to the above, it can be understood, that for a 200 mW laser pulse, charcoal may be partially ignited within 0.5 milliseconds, thereby causing a change in composition. It will be understood by those skilled in the art that embodiments of the present invention are not limited thereto, and methods and apparatus according to embodiments of the present invention may also inspect other substances. For example, for each irradiation, the energy of the exciting light may range from 0.1 millijoule to 0.5 millijoule.
It can be understood from the above examples that for a flammable or explosive dangerous product, a short-time laser pulse may cause a change in composition, and by means of two optical signal collections separated by the predetermined time interval, in particular, by means of collecting two optical signals before and after the irradiation of the exciting light and comparing two spectra from the two optical signals, it can be determined whether or not there has been a change in composition of the object, that is, whether or not the object has been damaged.
The following examples are given for explaining a specific manner for comparing the first spectrum with the second spectrum.
In an example, as shown in
As an example, the first threshold may be set according to actual conditions. First, an absolute value of the intensity of the spectrum may vary due to different objects to be detected and different corrections for optical devices in actual operation, thus the first threshold may take the form of a ratio (percent), that is, the difference between the overall integrated intensity of the first spectrum and the overall integrated intensity of the second spectrum is generally expressed in the form of “(the overall integrated intensity of the second spectrum being subtracted from the overall integrated intensity of the first spectrum) divided by the overall integrated intensity of the first spectrum.” For example, in this case, the first threshold may be ±20%. Secondly, even if the first threshold is in the form of a percentage, the percentage may fluctuate due to factors such as instability of the laser power. For a system with high stability such as high stability of laser power, a relatively small first threshold will be adopted. For example, the first threshold can be set to ±5%. For a system with poor stability, the first threshold can be set to ±25%. In the example shown in
In another example, as shown in
First of all, the first spectrum signal is discretized into a discrete numerical form. If the superposition signal is a continuous analog curve, then it needs to be converted into a discrete numerical form by a sampling process. However, in practice, the first spectrum signal is often in the discrete numerical form. In this case, one only needs to acquire numerical sample points directly.
The fluorescent signal changes more slowly and smoothly in comparison with a signal such as a Raman characterizing signal. As an example, the fluorescent envelope may be calculated by iteration as follows:
assuming that {yn} is a sequence of numerical sample points of the first spectrum signal, yn(i) is a value of the ith numerical sample point, and {yn+1} is the sequence which is calculated out after one iteration and yn+1(i) is a value of the itn numerical sample point in {yn+1}, then
where m is a positive integer and has an initial value of 1, and the above iteration is performed repeatedly until m meets a predetermined threshold, where m is added by 1 per iteration. By the above iterative calculation, the fluorescent envelope can be obtained.
In the above equation (1), “min[ . . . , . . . ]” represents an operation of selecting a minimum. Obviously, the serial number of the numerical point in each iterative calculation should meet the condition that i-m >0 and i+m is not greater than the total length of the sequence {yn}. If a numerical point does not meet the condition, it may maintain its original value constantly in the iterative calculation.
In an example, the predetermined threshold of m is determined depending on the smoothness of the first spectrum signal. For example, when two points spaced by a distance of 2×m in a sequence of iterative results have a width of wave number which is greater than a minimum peak width but smaller than a fluorescent envelope width, it may be determined that m meets the predetermined threshold.
In an example, in order to further improve the calculation accuracy, the first spectrum signal may be subject to a logarithm treatment or a square treatment before the above iterative calculation is performed.
Although in the above example, the calculation of the fluorescence interference signal is explained with reference to the iterative method as shown in equation (1), it should be understood that it is not necessary. Methods for solving a smooth spectrum signal in the art may also be used to solve the above fluorescent envelope, but the method may be more complex and cause a low calculation efficiency.
The extraction method of a fluorescent envelope of the second spectrum is similar to the extraction method of the fluorescent envelope of the first spectrum described above, and thus its details will be omitted herein.
As an example, the above step S32 may include:
step S321: detecting a position and an intensity of one or more peaks in the fluorescent envelope of the first spectrum to obtain the intensity of the one or more fluorescent envelope peaks of the first spectrum (may be referred to as one or more first reference fluorescent intensities);
step S322: detecting an intensity at a position of the fluorescent envelope of the second spectrum corresponding to the position (indicated by wave number of the fluorescent envelope peak of the first spectrum) of the one or more peaks to obtain one or more second reference fluorescent intensities (it is noted that the fluorescent intensity at the position of the fluorescent envelope of the second spectrum corresponding to the wave number of the one or more peaks of the fluorescent envelope of the first spectrum is not necessarily a peak value);
step S323: determining the object is damaged if a difference between the first reference fluorescent intensity and the second reference fluorescent intensity exceeds a second threshold; otherwise, determining the object is not damaged.
In the above example, it is preferable to make the pulse powers of the exciting light in the two measurements be equal. Obviously, if the powers of the exciting light in the two measurements are different, it is necessary to correct one of the two detected spectra. The method is similar to the method as mentioned above, and thus its details will be omitted herein.
With regard to the example shown in
As an example, the second threshold may be set according to actual needs. Similar to the difference between the overall integrated intensity of the first spectrum and the overall integrated intensity of the second spectrum, the difference between the first reference fluorescent intensity and the second reference fluorescent intensity is usually expressed in the form of “(the second reference fluorescent intensity being subtracted from the first reference fluorescent intensity) is divided by the first reference fluorescent intensity.” For example, in this case, the second threshold may be ±20%, ±10% or other suitable value. For systems with high stability such as stable laser power, the second threshold may be relatively small. For systems with poor stability, the second threshold may be relatively large. In the example shown in
For the case where the fluorescent envelope of the first spectrum has multiple peaks, the difference between each of the first reference fluorescent intensities and the corresponding second reference fluorescent intensities may be separately calculated and then compared with the second threshold, respectively. It will be determined that the object is damaged if any one of the differences exceeds the second threshold. Alternatively, the difference between each of the first reference fluorescent intensities and the corresponding second reference fluorescent intensities may be firstly calculated, a single metric value (for example, a root mean square average value, a geometric mean value, etc.) is then calculated from the differences and compared to the second threshold. It will be determined that the object is damaged if the single metric value exceeds the second threshold.
In an example, the first spectrum and the second spectrum may both be spectra acquired by a Raman spectrometer, and it may be determined whether or not the composition of the object is changed by mainly comparing Raman spectral characteristic peaks in the first spectrum with those in the second spectrum. Specifically, as an example, as shown in
step S31′: extracting a Raman spectral characteristic peak in the first spectrum and a Raman spectral characteristic peak in the second spectrum, respectively;
step S32′: comparing position (wave number) and intensity of the Raman spectral characteristic peak in the first spectrum with position and intensity of the Raman spectral characteristic peak in the second spectrum, respectively; and determining that the object is damaged if a difference between the position of the Raman spectral characteristic peak in the first spectrum and the position of the Raman spectral characteristic peak in the second spectrum is greater than a third threshold or if a difference between the intensity of the Raman spectral characteristic peak in the first spectrum and the intensity of the Raman spectral characteristic peak in the second spectrum is greater than a fourth threshold, and determining that the object is not damaged if the difference in position is less than the third threshold and the difference in intensity is less than the fourth threshold.
In another embodiment, another setting may be made, that is, it is determined that the object is damaged if both the difference in position is greater than the third threshold and the difference in intensity is greater than the fourth threshold. It is determined that the object is not damaged if either the difference in position is less than the third threshold or the difference in intensity is less than the fourth threshold. Of course, this embodiment may not be the most desired, but can be set as needed.
Any peak detection method known in the art (e.g., Gaussian fitting method) may be employed to extract the peak positions of the fluorescent envelopes of the first and second spectra as well as the Raman spectra characteristic peaks in the first and second spectra.
As an example, the third threshold may be set according to actual conditions. For example, the third threshold may be 10 or 20 (Raman shift, in cm−1) or other suitable value. The fourth threshold may also be set according to actual conditions. In the case where the stability of the power of the exciting light source is relatively high, the fourth threshold may be set to 10%. The fourth threshold may be set in the range of 5% to 30%.
Further, the comparison between the first spectrum and the second spectrum may be achieved on basis of a similarity between the first spectrum and the second spectrum. For example, the above step S30 may include: calculating the similarity between the first spectrum and the second spectrum; and determining that the object is damaged if the similarity between the first spectrum and the second spectrum is less than a fifth threshold; otherwise, determining that the object is not damaged.
The above similarity may be calculated by various methods. For example, if A(x) represents the first spectrum and B(x) represents the second spectrum, in an example, the above similarity may be calculated by using the maximum likelihood algorithm on basis of the following equation (2):
where Corr is the similarity between the first spectrum and the second spectrum, and the operator of “.” represents a dot product operation.
In another example, A(x) and B(x) may be sampled respectively to obtain respective n sample points. These sample points are defined as A1, A2, . . . , An and B1, B2, . . . , Bn, respectively. The similarity Corr between the first spectrum and the second spectrum may be calculated on basis of the following equation (3):
where the operator of “.” also represents a dot product operation.
In another example, A(x) and B(x) may be sampled respectively to obtain their respective n sample points. These sample points are defined as A1, A2, . . . , An and B1, B2, . . . , Bn, respectively. The similarity Corr between the first spectrum and the second spectrum may be calculated on basis of the following equation (4):
The above calculations of the similarity may be performed for the whole spectrum, or may be performed for local parts with the characterizing portion in the first spectrum and the second spectrum. The above paragraphs only give some examples of calculation of the similarity. Alternatively, other calculation methods of the similarity in the art are also applicable. Determining whether or not the difference between the first spectrum and the second spectrum is within a predetermined range may be achieved by determining whether or not the similarity exceeds the fifth threshold. As an example, the fifth threshold may be such as 0.9, 0.8 or the like. The embodiments of the present invention are not limited thereto, and other values may be set for the fifth threshold according to actual needs.
In the above embodiments, it is described that it is determined whether or not the object is damaged by comparing the first spectrum with the second spectrum based on the overall integrated intensity, the fluorescent envelope peak intensity (the reference fluorescent intensity) and the Raman spectral characteristics or by calculating the similarity between the spectra. Among these methods, it is easiest to calculate the overall integrated intensity of the spectrum, it is more complex to calculate the intensity and position of the fluorescent envelope peak as well as the similarity between the spectra, and it is most complex to calculate the Raman spectral characteristics, especially when the fluorescent intensities in the first spectrum and the second spectrum are relatively high, it is necessary to remove the fluorescent interference to find the characteristic peak of the Raman spectrum. But it is most accurate to determine whether or not the object to be detected is damaged based on the Raman spectral characteristics. Therefore, in practice, the above three methods may be used in any combination, for example, firstly comparing the first spectrum with the second spectrum based on the overall integrated intensity or the fluorescent envelope peak intensity, and then comparing the first spectrum with the second spectrum based on the Raman spectral characteristics. Two examples of combining the above three methods are provided as follows.
In an example, as shown in
comparing the overall integrated intensity of the first spectrum with the overall integrated intensity of the second spectrum to obtain a difference between the overall integrated intensity of the first spectrum and the overall integrated intensity of the second spectrum; determining that the object is damaged if the difference between the overall integrated intensity of the first spectrum and the overall integrated intensity of the second spectrum exceeds the first threshold; otherwise, the following steps are performed:
extracting the fluorescent envelope of the first spectrum and the fluorescent envelope of the second spectrum, respectively; detecting the position and the intensity of one or more peaks in the fluorescent envelope of the first spectrum to obtain one or more reference fluorescent intensities of the first spectrum;
detecting the intensity at a position in the fluorescent envelope of the second spectrum corresponding to the position of the one or more peaks to obtain one or more second reference fluorescent intensities;
determining that the object is damaged if the difference between the first reference fluorescent intensity and the second reference fluorescent intensity exceeds the second threshold; otherwise, the following steps are performed:
extracting a Raman spectral characteristic peak in the first spectrum and a Raman spectral characteristic peak in the second spectrum, respectively;
comparing the position and the intensity of the Raman spectral characteristic peak in the first spectrum with the position and the intensity of the Raman spectral characteristic peak in the second spectrum, respectively; determining that the object is damaged if the difference between the position of the Raman spectral characteristic peak in the first spectrum and the position of the Raman spectral characteristic peak in the second spectrum exceeds the third threshold or if the difference between the intensity of the Raman spectral characteristic peak in the first spectrum and the intensity of the Raman spectral characteristic peak in the second spectrum exceeds the fourth threshold; and determining that the object is not damaged if the difference between the position of the Raman spectral characteristic peak in the first spectrum and the position of the Raman spectral characteristic peak in the second spectrum is less than the third threshold and the difference between the intensity of the Raman spectral characteristic peak in the first spectrum and the intensity of the Raman spectral characteristic peak in the second spectrum is less than the fourth threshold.
In the above example, the first threshold and the second threshold may be set to be relatively large, such that when the difference between the first spectrum and the second spectrum is relatively large, it may be directly determined that the object is damaged by comparing the first spectrum with the second spectrum based on the overall integrated intensity or the reference fluorescent intensity, which can improve the calculation efficiency. When the difference between the first spectrum and the second spectrum is relatively small, in order to improve the accuracy of the detection, it may be determined whether or not the object to be detected is damaged by comparing the first spectrum with the second spectrum based on the differences in the position and the intensity of the Raman spectral characteristic peak. It is also possible to decide whether or not to use a method of calculating the similarity between the spectra as needed. This can take full advantage of these methods.
In another example, when the similarity calculation may be performed only on a partial portion including the characteristic portion in the first spectrum and the second spectrum, as shown in
comparing the overall integrated intensity of the first spectrum with the overall integrated intensity of the second spectrum to obtain the difference between the overall integrated intensity of the first spectrum and the overall integrated intensity of the second spectrum; determining that the object is damaged if the difference between the overall integrated intensity of the first spectrum and the overall integrated intensity of the second spectrum exceeds the first threshold; otherwise, the following steps are performed:
extracting the fluorescent envelope of the first spectrum and the fluorescent envelope of the second spectrum, respectively;
detecting the position and the intensity of one or more peaks in the fluorescent envelope of the first spectrum to obtain one or more fluorescent envelope intensities (first reference fluorescent intensity) of the first spectrum;
detecting the intensity at a position in the fluorescent envelope of the second spectrum corresponding to the position of the one or more peaks to obtain one or more second reference fluorescent intensities;
determining that the object is damaged if the difference between the first reference fluorescent intensity and the second reference fluorescent intensity exceeds the second threshold; otherwise, the following steps are performed:
calculating the similarity between the first spectrum and the second spectrum; determining that the object is damaged if the similarity between the first spectrum and the second spectrum is less than the fifth threshold; otherwise, determining that the object is not damaged.
In the example shown in
In another example, when the similarity calculation is preferably performed on the entire spectrum, the method including the similarity calculation and the comparison between the similarity and the fifth threshold may replace the method including the comparison between the difference between the first reference fluorescent intensity and the second reference fluorescent intensity and the second threshold.
In an example, the exciting light is achieved by a laser pulse, each pulse having an energy of 0.1 millijoule to 0.5 millijoule.
In an embodiment of the present invention, in order to improve the inspection effect, the first spectrum and the second spectrum may be smoothed before the first spectrum and the second spectrum are compared with each other. However, embodiments of the present invention are not limited thereto, and for example, the first spectrum and the second spectrum may not be smoothed.
An embodiment of the present invention also discloses an apparatus 100 for inspecting security of an object to be detected. As shown in
With the above-described the apparatus 100 for inspecting security of the object to be detected, it is possible to determine whether or not the object is damaged, for example, by using the aforementioned method S100 for detecting security of the object to be detected, to reduce or eliminate the risk due to the reaction of the object with the exciting light.
In an embodiment, the object state determining device 50 may include at least one of a first module 51, a second module 52, a third module 53 and a fourth module 54. The first module 51 is configured to compare the overall intensities of the spectra which are respectively generated from the optical signals collected from the same object at least twice. The second module 52 is configured to compare the fluorescent envelopes of the spectra which are respectively generated from the optical signals collected from the same object at least twice. The third module 53 is configured to compare the Raman spectral characteristics of the spectra which are respectively generated from the optical signals collected from the same object at least twice. The fourth module 54 is configured to calculate the similarity between the spectrum signals which are collected from the same object at least twice. The first module 51, the second module 52, the third module 53 and the fourth module 54 are respectively used to perform the above methods in which it is determined whether or not the object is damaged by comparing the first spectrum with the second spectrum based on the overall integrated intensity, the reference fluorescent intensity, the Raman spectral characteristic and the similarity of the spectrum signals. The first module 51, the second module 52, the third module 53 and the fourth module 54 may be used independently or in combination. For example, the first module 51 can provide a start signal for the second module 52 to make the second module 52 operate in a case where the first module 51 cannot determine whether or not the object is damaged, and the second module 52 can provide a start signal for the third module 53 or the fourth module 54 to make the third module 53 or the fourth module 54 operate in a case where the second module 52 cannot determine whether or not the object is damaged, so as to finally determine whether or not the object is damaged.
In an embodiment, the apparatus 100 for inspecting security of the object to be detected may further include an exciting light modulation module 60. The exciting light modulation module 60 may modulate the exciting light into at least two sets of laser pulses having a time interval greater than or equal to 500 milliseconds. As mentioned above, it is necessary to collect the optical signals for the object at least twice for purpose of inspecting security of the object. There may be a time interval, for example, more than 500 milliseconds, between two adjacent collections. The exciting light modulation module 60 can directly control the exciting light to achieve at least two collections as required for the modulation manner of the exciting light, without adjusting the optical device and the object, thereby improving the inspection efficiency.
In an embodiment of the present invention, it is ensured that the object is not ignited after two pulsed irradiations by controlling the laser power and the light emitting time. If the difference between two signals exceeds the threshold, the detection will be stopped and it is warned that the substance is easily damaged by the laser.
As an example, as shown in
However, embodiments of the present invention are not limited thereto, for example, optical devices employed in the Raman spectroscopy inspecting apparatus in the related art can be used as the optical device of the apparatus 100 for inspecting security of the object to be detected.
The comparison of the first spectrum and the second spectrum may be performed, for example, by a computer or a processor.
The above description has explained various embodiments of the above method and apparatus for inspecting security of the object to be detected by schematic views, flow charts and/or examples. In case that the schematic views, flow charts and/or examples each include one or more functions and/or operations, the skilled person in the art should understand that each function and/or operation in such schematic views, flow charts and/or examples may be implemented separately and/or collectively by various structures, hardware, software, firmware or any combination of them. In an embodiment, some parts of the subject of the embodiments of the present disclosure may be implemented by Application Specific Integrated Circuits (ASIC), Field Programmable Gate Arrays (FPGA), Digital Signal Processors (DSP) or other integrated forms. However, the skilled person in the art should understand that some aspects of the embodiments disclosed herein may be implemented equally in an integrated circuit entirely or partly, implemented as one or more computer programs running on one or more computers (for example, implemented as one or more programs running on one or more computer systems), implemented as one or more programs running on one or more processors (for example, implemented as one or more programs running on one or more microprocessors), implemented as firmware, or implemented as any combination of the above methods. From the present disclosure, the skilled person in the art has the capability of designing circuits and/or writing software and/or firmware codes. Furthermore, the skilled person in the art will appreciate that the mechanism of the subject of the present disclosure may be delivered as various forms of program products, and the exemplified embodiments of the subject of the present disclosure may be applicable independent of the specific types of signal carrying media that perform the delivery in practice. Examples of the signal carrying media include, but not limited to: recordable media, such as a floppy disc, a hard disk drive, an optical disc (CD, DVD), a digital magnetic tape, a computer memory or the like; and transmission media such as digital and/or analog communication media (for example, an optical fiber cable, a wave guide, a wired communication link, a wireless communication link or the like).
All of the above embodiments of the present disclosure may be combined freely to form other embodiments unless there are technical obstacles or contradictions. All of these other embodiments fall within the protection range of the present disclosure.
Although the present disclosure has been explained with reference to the drawings, the embodiments shown in the drawings are only illustrative, instead of limiting the present disclosure. Scales in the drawings are only illustrative, instead of limiting the present disclosure.
Although some embodiments of the general inventive concept are illustrated and explained, it would be appreciated by those skilled in the art that modifications and variations may be made in these embodiments without departing from the principles and spirit of the general inventive concept of the present disclosure, the scope of which is defined in the appended claims and their equivalents.
| Number | Date | Country | Kind |
|---|---|---|---|
| 201711442583.3 | Dec 2017 | CN | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/CN2018/122839 | 12/21/2018 | WO | 00 |
