Ink mark identification method based on laser desorption ionization mass spectrometer

Abstract

The invention relates to the technical field of ink mark identification, in particular to an ink mark identification method based on a laser desorption ionization mass spectrometer, which comprises the following steps: sampling from a paper file to be identified to obtain an ink mark inspection material to be detected; placing the to-be-detected ink mark inspection material in a detection instrument for spectrum acquisition and analysis so as to form a to-be-detected ink mark characteristic spectrogram; and comparing the to-be-detected ink mark characteristic spectrogram with a standard ink mark characteristic spectrogram to identify the to-be-detected ink mark characteristics. The identification method is rapid, efficient and high in accuracy, errors caused by manual operation can be reduced, sampling is convenient, a detected material does not need to be pretreated, and a detected material sample is not damaged.

Description

Technical Field

[0001] The invention relates to the technical field of ink mark identification, and in particular to an ink mark identification method based on a laser desorption ionization mass spectrometer. Background Art

[0002] The time when a document was made is an important part of criminal science identification and a difficult problem in document inspection technology. The inspection of the time when a document was made requires the provision of a comparison sample. Only when the inspection material and the comparison sample have the same type of ink can the final comparison and analysis be carried out.

[0003] In the prior art, ink comparison and analysis is often achieved through manual comparison or instrument detection. However, manual comparison has problems such as large errors, low accuracy, and low comparison efficiency; instrument comparison usually requires pretreatment of the test material, which is cumbersome to operate. In addition, high-resolution mass spectrometry is used to detect ink, but high-resolution mass spectrometry uses the principle of chemical electric power source, and its resolution is low. The volatile substances of different pens are different, which will cause the spectrum peaks to be messy, and it is not easy to compare and analyze, with low efficiency and large errors. Summary of the invention

[0004] Other features and advantages of the present invention will be described in the following description, and partly become apparent from the description, or be understood by practicing the present invention. The purpose and other advantages of the present invention can be realized and obtained by the structures specifically pointed out in the description, claims and other drawings of the description.

[0005] The purpose of the present invention is to overcome the above-mentioned shortcomings and provide an ink identification method based on laser desorption ionization mass spectrometry, which is fast, efficient, and highly accurate, can reduce errors in manual operations, is convenient for sampling, does not require pretreatment of the sample, and does not damage the sample.

[0006] To achieve the above object, the technical solution of the present invention is: an ink identification method based on laser desorption ionization mass spectrometer, comprising the following steps:

[0007] Sampling: sampling from the paper documents to be identified to obtain the ink sample to be tested;

[0008] Spectrum sampling, placing the ink sample to be tested in a detection instrument for spectrum sampling and analysis to form a characteristic spectrum of the ink to be tested;

[0009] Comparison: comparing the ink feature spectrum to be tested with the standard ink feature spectrum to identify the characteristics of the ink to be tested.

[0010] The present invention first samples from the paper document to be identified, then uses a detection instrument to collect and analyze the spectrum and form a characteristic spectrum of the ink to be tested, and then compares the characteristic spectrum of the ink to be tested with the characteristic spectrum of the standard ink to obtain the characteristics of the ink to be tested. The identification method of the present invention is fast, efficient, and highly accurate, can avoid errors caused by manual operation, and is convenient for sampling, and the sample does not need to be pre-processed and does not damage the sample.

[0011] In some embodiments, comparing the ink feature spectrum to be tested with the standard ink feature spectrum to identify the ink feature to be tested comprises the following steps:

[0012] Acquisition of standard ink feature spectrum, obtaining the standard ink feature spectrum from a standard ink feature spectrum database;

[0013] Similarity calculation, calculating the similarity between the ink feature spectrum to be tested and the standard ink feature spectrum;

[0014] The formation of the identification score is scored according to the similarity to form the identification score of the characteristic spectrum of the ink mark to be tested, so as to identify the characteristics of the ink mark to be tested.

[0015] In some embodiments, the establishment of the standard ink feature spectrum database includes:

[0016] Acquisition of original ink feature spectra: 1-100 target points of the same sample are tested with the same detection parameters, and each target point is repeatedly collected twice to obtain 1-200 original ink feature spectra;

[0017] The formation of the standard ink feature spectrum is to pre-process the original ink feature spectrum to form the standard ink feature spectrum.

[0018] In some embodiments, the original ink feature spectrum is preprocessed to form a standard ink feature spectrum, specifically:

[0019] The original ink characteristic spectrum is subjected to smoothing and denoising, baseline correction, normalization, characteristic peak extraction, mass axis calibration and spectrum peak alignment to form a standard ink characteristic spectrum.

[0020] In some embodiments, the detection instrument is a matrix-assisted laser desorption / ionization mass spectrometer. The matrix-assisted laser desorption / ionization mass spectrometer can perform time tracing and component analysis to form a matrix-assisted laser desorption / ionization time-of-flight mass spectrometer, in which the peaks represent compounds or compound fragments, and the intensity of the peaks represents the content of the compound and the size of the compound fragments.

[0021] In some embodiments, the ion source of the detection instrument is a matrix-assisted laser desorption ionization source.

[0022] In some embodiments, the spectrum acquisition includes

[0023] Ionization, using laser to desorb and ionize the ink sample to be tested to form ions with different mass-to-charge ratios;

[0024] Time-of-flight mass analysis, analyzing the time it takes for the ions of different mass-to-charge ratios to arrive at the detection instrument;

[0025] The detection step is to detect the ions with different mass-to-charge ratios arriving at the detection instrument to form a characteristic spectrum of the ink to be detected.

[0026] In some embodiments, the wavelength of the laser is 266 nm to 355 nm.

[0027] In some embodiments, the spectrum acquisition also includes sampling before ionization, and the sampling is to fix the ink sample to be tested on a target plate in the detection instrument, and then place the target plate in the sampling chamber. Under the action of laser energy, the matrix and sample on the sample target form ions with different mass-to-charge ratios, and reach the detector under the action of the electric field.

[0028] In some embodiments, the ink feature to be tested is one or more of ink composition, ink brand, ink model, ink color, ink production time, and ink formation time.

[0029] In some embodiments, the shape of the ink sample to be tested includes a shape composed of straight line segments, a shape composed of curved lines, or a shape composed of straight line segments and curved lines.

[0030] In some embodiments, the longitudinal length of the ink sample to be tested is 0 cm to 10 cm, and the transverse length of the ink sample to be tested is 0 cm to 10 cm.

[0031] In some embodiments, the ink to be tested in the ink sample to be tested includes ink, toner, and ink.

[0032] By adopting the above technical solution, the beneficial effects of the present invention are as follows: the present invention first samples from the paper document to be identified, then uses the detection instrument to collect spectrum and analyze to form the ink feature spectrum to be tested, and then compares the peak position, peak intensity, etc. between the ink feature spectrum to be tested and the standard ink feature spectrum to obtain the ink feature to be tested. The identification method of the present invention is fast, efficient, and highly accurate, can avoid errors caused by manual operation, and is convenient for sampling, and the sample does not need to be pre-processed and does not damage the sample.

[0033] It is to be understood that the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the present disclosure.

[0034] Undoubtedly, these and other objects of the present invention will become more apparent after the following detailed description of the preferred embodiment described with reference to various figures and drawings.

[0035] In order to make the above and other purposes, features and advantages of the present invention more obvious and easy to understand, one or several preferred embodiments are given below and described in detail with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] The accompanying drawings are used to provide further understanding of the present invention and constitute a part of the specification. They are used together with the embodiments of the present invention to explain the present invention and do not constitute a limitation of the present invention.

[0037] In the drawings, the same reference numerals are used for the same components and the drawings are schematic and not necessarily drawn to scale.

[0038] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only one or several embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on such drawings without paying creative work.

[0039] Figure 1 A flow chart of an ink identification method based on a laser desorption ionization mass spectrometer according to some embodiments of the present invention;

[0040] Figure 2 A schematic diagram of the process of collecting spectrum in ink mark identification in some embodiments of the present invention;

[0041] Figure 3 A schematic diagram of the comparison process in ink identification in some embodiments of the present invention;

[0042] Figure 4 A schematic diagram of the process of establishing a standard ink mark characteristic spectrum database in ink mark identification in some embodiments of the present invention;

[0043] Figure 5 A schematic diagram of a spectrum preprocessing process according to some embodiments of the present invention;

[0044] Figure 6 It is the ink standard spectrum;

[0045] Figure 7 Ink spectra of 4 kinds of inks to be tested;

[0046] Figure 8 It is the ink standard spectrum;

[0047] Fig. 9 The ink spectra of 4 inks to be tested are shown below;

[0048] Fig.10 It is the standard spectrum of toner ink;

[0049] Fig.11 It is the ink spectrum of the toner to be tested. DETAILED DESCRIPTION

[0050] The following will describe the implementation methods of the present invention in detail with reference to the accompanying drawings and embodiments, so that the implementation process of how the present invention applies technical means to solve technical problems and achieve technical effects can be fully understood and implemented accordingly. It should be noted that as long as there is no conflict, the various embodiments of the present invention and the various features in the embodiments can be combined with each other, and the technical solutions formed are all within the protection scope of the present invention.

[0051] Meanwhile, in the following description, many specific details are set forth for the purpose of explanation to provide a thorough understanding of the embodiments of the present invention. However, it is obvious to those skilled in the art that the present invention can be implemented without the specific details or the specific manner described herein.

[0052] Reference Figure 1 , Figure 1 The present invention is a flow chart of an ink identification method based on a laser desorption ionization mass spectrometer according to some embodiments of the present invention.

[0053] According to some embodiments of the present invention, the present invention provides an ink identification method based on laser desorption ionization mass spectrometry. The identification method comprises the following steps:

[0054] Sampling: sampling from the paper documents to be identified to obtain the ink sample to be tested;

[0055] Spectrum sampling, placing the ink sample to be tested in a detection instrument for spectrum sampling and analysis to form a characteristic spectrum of the ink to be tested;

[0056] Comparison: comparing the ink feature spectrum to be tested with the standard ink feature spectrum to identify the characteristics of the ink to be tested.

[0057] The present invention first samples from the paper document to be identified, then uses a detection instrument to collect and analyze the spectrum and form a characteristic spectrum of the ink to be tested, and then compares the characteristic spectrum of the ink to be tested with the characteristic spectrum of the standard ink to obtain the characteristics of the ink to be tested. The identification method of the present invention is fast, efficient, and highly accurate, can avoid errors caused by manual operation, and is convenient for sampling, and the sample does not need to be pre-processed and does not damage the sample.

[0058] According to some embodiments of the present invention, optionally, in the sampling step, sampling is performed from the paper document to be identified to obtain the ink sample to be tested, specifically: using tools such as a hole puncher, a cutter, scissors, etc. to drill holes or cut the paper document to be identified to obtain the ink sample to be tested.

[0059] According to some embodiments of the present invention, optionally, comparing the ink feature spectrum to be tested with a standard ink feature spectrum to identify the ink feature to be tested comprises the following steps:

[0060] Acquisition of standard ink feature spectrum, obtaining the standard ink feature spectrum from a standard ink feature spectrum database;

[0061] Similarity calculation, calculating the similarity between the ink feature spectrum to be tested and the standard ink feature spectrum;

[0062] The formation of the identification score is scored according to the similarity to form the identification score of the characteristic spectrum of the ink mark to be tested, so as to identify the characteristics of the ink mark to be tested.

[0063] According to some embodiments of the present invention, optionally, the establishment of the standard ink feature spectrum database includes:

[0064] Acquisition of original ink feature spectra: 1-100 target points of the same sample are tested with the same detection parameters, and each target point is repeatedly collected twice to obtain 1-200 original ink feature spectra;

[0065] The formation of the standard ink feature spectrum is to pre-process the original ink feature spectrum to form the standard ink feature spectrum.

[0066] According to some embodiments of the present invention, optionally, the original ink feature spectrum is preprocessed to form a standard ink feature spectrum, specifically:

[0067] The original ink characteristic spectrum is subjected to smoothing and denoising, baseline correction, normalization, characteristic peak extraction, mass axis calibration and spectrum peak alignment to form a standard ink characteristic spectrum.

[0068] Among them, smoothing and denoising can adopt but not limited to mean filtering, Gaussian filtering, SG filtering, median filtering, frequency-based Fourier transform, wavelet transform, least squares fitting method based on fitting and other algorithms. Baseline correction can adopt but not limited to polynomial fitting method, local minimum method, wavelet transform method, linear interpolation method, etc. Normalization can adopt but not limited to total ion flow method, maximum value method, maximum and minimum peak method, LOG transformation, etc. Characteristic peak extraction can adopt but not limited to local extreme value method. Mass cycle calibration can adopt but not limited to the "three-point calibration method" of cubic fitting. Spectral peak alignment can adopt but not limited to methods based on dynamic calibration.

[0069] According to some embodiments of the present invention, optionally, in the comparison step, the ink feature spectrum to be tested is compared with the standard ink feature spectrum to identify the ink feature to be tested, specifically: the ink feature spectrum to be tested is compared with the standard ink feature spectrum for similarity to identify the ink feature to be tested. Among them, the similarity comparison can adopt but is not limited to the spectrum similarity scoring method based on the Euclidean distance formula (for example: Chinese invention patent CN106650779B, named as a method for calculating spectrum similarity), an infrared spectrum analysis and comparison similarity algorithm of the absolute difference method (for example: Chinese patent CN111426648B, named as a method and system for determining the similarity of infrared spectra), Pearson correlation coefficient method, improved m / z weighted and unweighted difference comparison algorithm, etc. In addition, the similarity comparison can also be judged by human identification.

[0070] According to some embodiments of the present invention, optionally, the detection instrument is a matrix-assisted laser desorption / ionization mass spectrometer. The matrix-assisted laser desorption / ionization mass spectrometer can perform time tracing and component analysis to form a matrix-assisted laser desorption / ionization time-of-flight mass spectrometer, in which the peaks in the mass spectrometer represent the compound or compound fragments, and the intensity of the peaks represents the content of the compound and the size of the compound fragments.

[0071] According to some embodiments of the present invention, optionally, the ion source of the detection instrument is a matrix-assisted laser desorption ionization source.

[0072] Reference Figure 2 , Figure 2 The figure is a schematic diagram of the process of spectrum collection in ink mark identification according to some embodiments of the present invention.

[0073] According to some embodiments of the present invention, optionally, the spectrum acquisition includes

[0074] Ionization, using laser to desorb and ionize the ink sample to be tested to form ions with different mass-to-charge ratios;

[0075] Time-of-flight mass analysis, analyzing the time it takes for the ions of different mass-to-charge ratios to arrive at the detection instrument;

[0076] The detection step is to detect the ions with different mass-to-charge ratios arriving at the detection instrument to form a characteristic spectrum of the ink to be detected.

[0077] According to some embodiments of the present invention, optionally, the wavelength of the laser is 266nm-355nm.

[0078] Optionally, the wavelength of the laser is 266nm, 276nm, 286nm, 296nm, 305nm, 315nm, 325nm, 335nm, 345nm, 355nm, or its value is within the range obtained by combining / intermediate values ​​of any two of the above values.

[0079] According to some embodiments of the present invention, the spectrum acquisition may further include sampling before ionization, wherein the sampling is to fix the ink sample to be tested on a target plate in the detection instrument, and then place the target plate in the sampling chamber. Under the action of laser energy, the matrix and sample on the sample target form ions with different mass-to-charge ratios, and reach the detector under the action of the electric field.

[0080] According to some embodiments of the present invention, optionally, the ink features to be measured include but are not limited to one or more of ink composition, ink brand, ink model, ink color, ink production time, and ink formation time.

[0081] According to some embodiments of the present invention, optionally, the shape of the ink sample to be tested includes a shape composed of straight line segments, a shape composed of curved lines, or a shape composed of straight line segments and curved lines.

[0082] Optionally, the shape of the ink sample to be tested is a shape composed of straight line segments, including but not limited to a triangle, a quadrilateral, a pentagon, etc.

[0083] Optionally, the shape of the ink sample to be tested is a shape composed of curves, including but not limited to a circle, an ellipse, etc.

[0084] Optionally, the shape of the ink sample to be tested is a shape composed of straight line segments and curves, including but not limited to a sector shape, a semicircle, etc.

[0085] According to some embodiments of the present invention, optionally, the longitudinal length of the ink sample to be tested is 0 cm to 10 cm, and the transverse length of the ink sample to be tested is 0 cm to 10 cm.

[0086] Optionally, the longitudinal length of the ink sample to be tested is 0 cm, 1 cm, 2 cm, 3 cm, 4 cm, 5 cm, 6 cm, 7 cm, 8 cm, 9 cm, 10 cm, or its value is within the range obtained by combining any two of the above values / intermediate values.

[0087] Optionally, the lateral length of the ink sample to be tested is 0 cm, 1 cm, 2 cm, 3 cm, 4 cm, 5 cm, 6 cm, 7 cm, 8 cm, 9 cm, 10 cm, or its value is within the range obtained by combining any two of the above values / intermediate values.

[0088] According to some embodiments of the present invention, optionally, the size of the ink sample to be tested can be adjusted according to the size of the target plate.

[0089] In some embodiments, the ink to be tested in the ink sample to be tested includes ink, toner, and ink.

[0090] Reference Figure 6-Figure 7 , Figure 6 is the ink standard spectrum, Figure 7 The following are the ink spectra of 4 kinds of inks to be tested. Figure 7 (a) in the figure is the ink spectrum of the first ink to be tested. Figure 7 (b) in the figure is the ink spectrum of the second ink to be tested. Figure 7 (c) in the figure is the ink spectrum of the third ink to be tested. Figure 7 (d) in the figure is the ink spectrum of the fourth ink to be tested.

[0091] By comparing Figure 7 and Figure 6 It can be seen that the brand, model, color and production time of the first type of ink to be tested are the same as those of the standard ink, but the ink formation time is different; the brand, model, color and ink formation time of the second type of ink to be tested are the same as those of the standard ink, but the production time is different; the brand, color, ink formation time and production time of the third type of ink to be tested are the same as those of the standard ink, but the model is different; the color and ink formation time of the fourth type of ink to be tested are the same as those of the standard ink, but the brand and model are different.

[0092] Reference Figure 8-Figure 9 , Figure 8 is the standard spectrum of ink, Fig. 9 The following are the ink spectra of 4 inks to be tested. Fig. 9 (a) is the ink spectrum of the first ink to be tested. Fig. 9 (b) is the ink spectrum of the second ink to be tested. Fig. 9 (c) in the figure is the ink spectrum of the third ink to be tested. Fig. 9 (d) in the figure is the ink spectrum of the fourth ink to be tested.

[0093] By comparing Fig. 9 and Figure 8 It can be seen that the brand, model, color and production time of the first ink to be tested are the same as those of the standard ink, but the ink formation time is different; the brand, model, color and ink formation time of the second ink to be tested are the same as those of the standard ink, but the production time is different; the brand, color, ink formation time and production time of the third ink to be tested are the same as those of the standard ink, but the model is different; the color and ink formation time of the fourth ink to be tested are the same as those of the standard ink, but the brand and model are different.

[0094] Reference Figure 10-11 , Fig.10 This is the standard spectrum of toner ink. Fig.11 is the ink trace spectrum of the toner to be tested. Fig.11 1 in the figure is the ink trace spectrum of the first toner to be tested. Fig.11 2 in the figure is the ink trace spectrum of the second toner to be tested. Fig.11 3 in the figure is the ink trace spectrum of the third toner to be tested. Fig.11 The 4 in the figure is the ink trace spectrum of the fourth toner to be tested.

[0095] By comparing Fig.11 and Fig.10 It can be seen that the ink mark of the first type of toner to be tested is the same as the ink mark of the standard toner in terms of brand, model, color and ink mark formation time, but the production time is different; the ink mark of the second type of toner to be tested is the same as the ink mark of the standard toner in terms of brand, color, ink mark formation time and production time, but the model is different; the ink mark of the third type of toner to be tested is the same as the ink mark of the standard toner in terms of color and ink mark formation time, but the brand and model are different; the ink mark of the fourth type of toner to be tested is the same as the ink mark of the standard toner in terms of brand, model, color and production time, but the ink mark formation time is different.

[0096] It should be understood that the embodiments disclosed in the present invention are not limited to the specific processing steps or materials disclosed herein, but should be extended to equivalent substitutions of such features understood by ordinary technicians in the relevant field. It should also be understood that the terms used herein are only used for the purpose of describing specific embodiments and are not meant to be limiting.

[0097] The "embodiment" mentioned in the specification means that the specific features or characteristics described in conjunction with the embodiment are included in at least one embodiment of the present invention. Therefore, the phrases or "embodiment" appearing in various places throughout the specification do not necessarily refer to the same embodiment.

[0098] It should be noted that many specific details are set forth in the above description to facilitate a full understanding of the present invention. However, the present invention may also be implemented in other ways different from those described herein. Therefore, the protection scope of the present invention is not limited to the specific embodiments disclosed above.

Claims

1. A method for identifying ink marks based on laser desorption ionization mass spectrometry, characterized in that: The following steps are involved: Sampling: sampling from the paper documents to be identified to obtain the ink sample to be tested; Spectrum sampling, placing the ink sample to be tested in a detection instrument for spectrum sampling and analysis to form a characteristic spectrum of the ink to be tested; Comparison: comparing the ink feature spectrum to be tested with the standard ink feature spectrum to identify the characteristics of the ink to be tested.

2. The ink identification method based on laser desorption ionization mass spectrometry according to claim 1 is characterized in that: The ink feature spectrum to be tested is compared with the standard ink feature spectrum to identify the ink feature to be tested; comprising the following steps: Acquisition of standard ink feature spectrum, obtaining the standard ink feature spectrum from a standard ink feature spectrum database; Similarity calculation, calculating the similarity between the ink feature spectrum to be tested and the standard ink feature spectrum; The formation of the identification score is scored according to the similarity to form the identification score of the characteristic spectrum of the ink mark to be tested, so as to identify the characteristics of the ink mark to be tested.

3. The ink identification method based on laser desorption ionization mass spectrometer according to claim 2 is characterized in that: The establishment of the standard ink feature spectrum database includes: Acquisition of original ink feature spectra: 1-100 target points of the same sample are tested with the same detection parameters, and each target point is repeatedly collected twice to obtain 1-200 original ink feature spectra; The formation of the standard ink feature spectrum is to pre-process the original ink feature spectrum to form the standard ink feature spectrum.

4. The ink identification method based on laser desorption ionization mass spectrometry according to claim 3 is characterized in that: The original ink feature spectrum is preprocessed to form a standard ink feature spectrum, specifically: The original ink characteristic spectrum is subjected to smoothing and denoising, baseline correction, normalization, characteristic peak extraction, mass axis calibration and spectrum peak alignment to form a standard ink characteristic spectrum.

5. The ink identification method based on laser desorption ionization mass spectrometry according to claim 1 is characterized in that: The detection instrument is a matrix-assisted laser desorption ionization mass spectrometer.

6. The ink identification method based on laser desorption ionization mass spectrometer according to claim 1 or 5, characterized in that: The ion source of the detection instrument is a matrix-assisted laser desorption ionization source.

7. The ink identification method based on laser desorption ionization mass spectrometry according to claim 1 is characterized in that: The spectrum acquisition includes Ionization, using laser to desorb and ionize the ink sample to be tested to form ions with different mass-to-charge ratios; Time-of-flight mass analysis, analyzing the time it takes for the ions of different mass-to-charge ratios to arrive at the detection instrument; The detection step is to detect the ions with different mass-to-charge ratios arriving at the detection instrument to form a characteristic spectrum of the ink to be detected.

8. The ink identification method based on laser desorption ionization mass spectrometry according to claim 1 is characterized in that: The ink feature to be tested is one or more of ink composition, ink brand, ink model, ink color, ink production time, and ink formation time.

9. The ink identification method based on laser desorption ionization mass spectrometry according to claim 1, characterized in that: The shape of the ink sample to be tested includes a shape composed of straight line segments, a shape composed of curved lines, or a shape composed of straight line segments and curved lines.

10. The ink identification method based on laser desorption ionization mass spectrometry according to claim 1, characterized in that: The ink to be tested in the ink sample to be tested includes ink, toner and ink.

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