Printing device for automatically adjusting security paper identification time point and identification method thereof

Abstract

The present invention relates to a technology applied to a printing device that allows printing only on security paper. The present invention is configured to reliably determine whether the paper is security paper, by comprehensively considering temporal and spatial patterns of a detection signal, an internal state of a printer, and a paper condition. To this end, the present invention includes the following technical features: The present invention is based on a detection value generated from a constituent material or a functional identification element included in the security paper, and applies various signal processing methods including frequency analysis or time characteristic analysis, such as a change amount, a change rate, a secondary change rate, and an occurrence frequency of the detection value. An identification time point is flexibly set on the basis of a detection time point of a sensor inside the printing device, an operation time point of a driving unit inside the printing device, or a previous printing result and a system state. Through this structure, the present invention overcomes the limitations of simplicity and fixability of the existing security paper identification technology, and provides a highly reliable security printing technology that may be applied even under various printing conditions.

Description

Printing device and identification method for automatically adjusting the timing of security paper identification

[0001] The present invention relates to a security printing device configured to enable document output only on security paper, and more specifically, to a method for automatically adjusting a determination time for determining whether a paper is security paper by considering the size and orientation of the paper loaded in the paper tray of the printing device and the operating conditions of the printing device (e.g., sensor detection time, roller driving time, etc.) and a printing device that executes the same.

[0002] In particular, the present invention relates to a technology that enables the determination of whether a paper is security paper with high reliability by precisely analyzing irregular detection signals caused by the random distribution of constituent materials or functional identification elements contained in the security paper and combining this with information obtained from sensors and driving units inside a printing device.

[0003] The device of the present invention is designed to be flexibly applied even in commercial printing device environments having various paper tray configurations and printing paths.

[0004] In high-tech companies and government agencies handling national secrets, the importance of physical security to prevent the leakage of printed documents is increasingly being emphasized, in addition to cybersecurity. Accordingly, document security technologies utilizing security paper have been developed and are being used as a means to block unauthorized printing, copying, or leakage of documents.

[0005] Security paper is distinguished from general printing paper (hereinafter referred to as non-security paper) and has the following special structure. It is manufactured by incorporating, attaching to the outside, or inserting into the paper fine metallic particles of micron size or smaller, metallic wires having a diameter or thickness of tens of μm or less (e.g., amorphous micro wires), or metallic strips (e.g., amorphous strips).

[0006] As used herein, “paper” generally refers to a printing medium used in a printing device and may be used substantially interchangeably with the term “paper.” Accordingly, in this specification, “paper” is interpreted as a concept that includes paper as a general printing medium.

[0007] A printing device configured to allow printing only on security paper includes a discrimination unit that determines whether the paper is security paper, and a detection module that detects constituent materials or functional identification elements contained in the security paper and generates a detection signal.

[0008] Based on the principle of electromagnetic induction, the detection module detects electrical changes that occur when metallic materials move or react within a magnetic field, converts them into analog or digital detection signals, and outputs them. These detection signals are transmitted to the discrimination unit, which analyzes the values ​​to determine whether the material is security paper and permits printing only if it is identified as security paper.

[0009] Therefore, in order to accurately determine whether a paper is security paper as it moves along the printing path during printing, it is necessary to consider not only the characteristics of the security paper itself but also the operational characteristics of the printing device using the paper.

[0010] The key considerations for this are as follows.

[0011] 1. Irregular distribution of constituent materials:

[0012] Depending on the manufacturing method of security paper, constituent materials may be arranged in a regular or random pattern. In particular, when incorporated into the pulp, the constituent materials are irregularly distributed within the paper, resulting in inconsistent detection values ​​and irregular signal patterns. A discrimination logic that reflects this irregularity is required.

[0013] 2. Changes in operating conditions of the printing device:

[0014] The printing device performs initial operation when power is applied or when sleep mode is released, and may temporarily suspend paper movement or adjust speed at specific locations during the printing process. Accordingly, the paper movement pattern may vary depending on the printing situation.

[0015] 3. Differences in printing behavior based on paper size and orientation:

[0016] Paper of various sizes can be loaded in either horizontal or vertical orientations, and accordingly, the printing start time, movement time per section, and printing timing vary. In other words, since the printing operation itself changes depending on the size and orientation of the paper, it is necessary to reflect this.

[0017] As such, a more precise method for identifying security paper is required that takes into account the irregularity of constituent materials, changes in internal conditions of the printing device, and the diversity of paper size and orientation.

[0018] Although various prior art technologies have been proposed regarding security paper identification technology, each technology has limitations in that it fails to comprehensively reflect the diverse variables of the overall printing environment, as it is an approach focused on specific conditions or methods. The following is an overview of major prior patents and their limitations.

[0019] 1. Application No. 10-2016-0145978

[0020] This technology installs a motion detection module near the paper tray to detect paper containing a security label and determines the presence of the security label based on the time from the moment the paper is picked up until the next paper is detected.

[0021] While this method offers the simplicity of being able to determine the presence or absence of a label, it fails to account for irregularities in detection signals, the motion detection module may interfere with paper transport, and there is a risk of device damage during prolonged use.

[0022] In addition, it is a structure that cannot flexibly respond to changes in printing operations that may occur when the paper size or orientation differs.

[0023] 2. Application No. 10-2019-0138618

[0024] This technology aims to overcome the limitations of motion detection modules by using a detection sensor to identify security paper by comparing a first detection value (no paper) with a second detection value (paper passed). While this method of comparing detection values ​​reduces the hardware burden, relying solely on simple value comparison makes it difficult to accurately identify security paper with irregular signal patterns.

[0025] In addition, during continuous printing, the distinction between individual sheets is unclear, and it cannot cope with changes in printing timing caused by printer operating conditions (feed speed, stop / speed, etc.) or changes in paper size and orientation.

[0026] 3. Application No. 10-2020-0045463

[0027] This prior patent is a structure that identifies security paper by comparing time difference detection values ​​through first and second optical sensors.

[0028] Although there have been attempts to replace existing motion detection modules with optical sensors, the limitations of simple comparison methods still exist, and there is also a possibility of interference during paper transport depending on the sensor's position or detection method.

[0029] In particular, although the detection time may change if the size or orientation of the paper the sensor faces changes, it does not include a correction or adaptation function for this.

[0030] 4. Application No. 10-2023-0062607

[0031] This technology is a method that identifies security paper by collecting time-series detection data over a specific interval from the start of printing and statistically analyzing it (variation, average, standard deviation, etc.).

[0032] Although precision has improved compared to the existing absolute value comparison method, high-dimensional signal pattern analysis (changes in rate of change, frequency components, etc.) was not reflected.

[0033] In addition, the automatic adjustment function for the determination point based on changes in printer operating conditions (e.g., changes in movement speed, drive unit response time, etc.) or paper conditions (size, orientation) is insufficient.

[0034] The aforementioned prior art implements security paper identification technology in various ways, but has the following common limitations:

[0035] 1. There is a lack of precise signal analysis and advanced pattern analysis technologies that take into account the irregular distribution of constituent materials or functional elements of security paper.

[0036] 2. Although the detection environment may change depending on variations in the internal operating conditions of the printing device, a timing adjustment and data collection method for automatic adaptation are not presented.

[0037] 3. Although paper of various sizes and orientations may be used depending on the paper tray, the design lacks consideration for changes in feed speed, detection position, and printing timing resulting from this.

[0038] In this regard, there remains a need for more sophisticated and flexible discrimination technology capable of comprehensively reflecting the detection signal characteristics of security paper and the operating variables of the printing device.

[0039] Most existing technologies determine whether a paper is security paper based solely on detection values ​​at a fixed point in time, and fail to cope with the complexity of detection signals arising from the diversity of printing environments and the physical characteristics of the security paper itself.

[0040] Therefore, the present invention aims to solve the following problems:

[0041] 1. Provision of a signal processing method capable of analyzing irregular detection signals more precisely

[0042] 2. Provision of technology that flexibly adjusts the data collection method and determination timing according to printer operating conditions

[0043] 3. Provision of a highly reliable security paper identification method that reflects feed patterns and printing operations varying by paper size and orientation

[0044] The present invention aims to solve problems that were not solved in the prior art as follows.

[0045] i) In order to analyze irregular signal patterns resulting from the random distribution of constituent materials or identification functional elements included in the security paper more precisely, it is desirable to apply a method for analyzing the signal pattern of the security paper by including not only the detection value but also the second rate of change of the detection value in the time domain, or by using at least one of an analysis method in the frequency domain or other similar transformation techniques.

[0046] It is desirable to analyze the irregular patterns of security paper using this method and apply the results to accurately identify the security paper, as well as to determine whether the paper is undetectable.

[0047] ii) In order to adjust the data collection method and the timing of determination according to the internal operating conditions of the printing device, it is desirable for the determination unit to selectively collect or process determination data to determine whether it is security paper among the detection values ​​continuously provided by the detection module, thereby efficiently utilizing unnecessary data processing, collection, storage space, and computing device resources.

[0048] To this end, it is desirable to process the detection values ​​provided by the detection module in at least one of the following methods: the first method of selectively collecting detection values ​​after a specific point in time; the second method of continuously providing detection values ​​but selectively using detection values ​​after a specific point in time; and the third method of prioritizing the processing of detection values ​​after a specific point in time by applying filtering based on predefined criteria, statistical analysis, or other techniques.

[0049] And, the setting of the specific point in time serving as the standard for data collection is performed by using a sensor that can be positioned in front of or behind the detection module along the printing path and a drive unit that rotates a roller positioned at a specific location,

[0050] 1. A point in time immediately or with a certain amount of time added or subtracted from the point in time when paper is detected by the sensor or the operation of the drive unit is detected.

[0051] 2. A point in time immediately or by adding or subtracting a certain amount of time from the point in time when the received detection value is above a specific standard, or when the rate of change of the detection value, the secondary rate of change of the detection value, the frequency of change of the detection value, the frequency of the rate of change, the frequency of the secondary rate of change, or the moving average value and other statistical measurements are determined to deviate from a specific standard.

[0052] 3. After the security paper identification for the previous paper is completed, if a preset time has elapsed or if the previous paper is not detected for longer than a preset threshold time.

[0053] 4. If the paper is not detected for longer than a preset threshold time.

[0054] 5. It is desirable to set it to at least one of the following: immediately after exiting sleep mode or after the system power is turned on, or after a preset time has elapsed.

[0055] In addition, it is desirable to additionally set at least one of the following based on the point in time when one of the plurality of sensors detects the paper at the aforementioned specific point in time: immediately at the time of detection, or at a time when a certain time is added or subtracted, or at other times satisfying predefined conditions.

[0056] iii) In order to reflect the characteristics of variations in printing operation (changes in paper movement patterns or printing time) according to paper size and orientation, it is preferable to use a second drive unit that drives a roller located behind the detection module equipped in the printing device, or a plurality of paper tray sensors that detect width and length guide positions when adjusting the paper tray and output an electrical signal.

[0057] In addition, the determination unit that determines whether it is security paper,

[0058] 1. A method of processing and analyzing the output signals of the plurality of paper tray sensors to derive and use size and orientation information of the paper tray in which the paper is picked up, or,

[0059] 2. It is preferable to apply at least one of the methods using the operation start detection signal of the second driving unit provided by the signal processing module above to adjust the determination point so that the size and orientation of the paper loaded in the paper tray are taken into account, and when the adjusted determination point is reached, to determine whether it is security paper using the detection value after a specific point in time.

[0060] According to the present invention, the following technical and industrial effects can be expected:

[0061] 1. Improvement in security paper identification accuracy

[0062] Since irregular detection signals caused by the random distribution of constituent materials or functional identification elements included in security paper can be precisely analyzed through various signal processing methods (time domain analysis, frequency domain analysis, pattern recognition, etc.), the accuracy and reliability of determining whether a material is security paper are significantly improved.

[0063] 2. Provides adaptability to changes in printing device operating conditions

[0064] By flexibly responding to changes in internal operating conditions, such as the operating status of the printing device's drive unit, the point of sensor detection, the power status, and the state after exiting sleep mode, and dynamically setting or adjusting the point of determination, consistent determination performance can be maintained even in various printing environments.

[0065] 3. Compatible with changes in paper size and orientation

[0066] By adjusting the determination point by considering factors such as travel distance, printing timing, and interaction with sensor positions that vary depending on the size and orientation of the paper loaded in the tray, stable determination is possible even in printing environments where horizontal / vertical orientations or paper of various sizes are mixed.

[0067] 4. Minimizing unnecessary data processing and optimizing system resources

[0068] The determination unit is configured to selectively collect or process only detection values ​​after a specific point in time, enabling data processing focused only on the necessary sections of the entire printing process. This reduces unnecessary storage space consumption and computational resource usage, while increasing applicability to low-spec devices.

[0069] 5. Expansion of industrial applicability

[0070] This invention is not limited to a specific structure and is designed so that the discrimination algorithm can be flexibly applied depending on the sensor placement location, drive unit configuration, and paper tray structure. Accordingly, it can be widely utilized in various industrial fields requiring document security, such as government agencies, military organizations, high-tech companies, and legal and financial institutions, and possesses high industrial value as a core technology capable of enhancing the physical security of printed materials.

[0071] Figure 1 illustrates the characteristics of security paper and non-security paper containing metal components.

[0072] Figure 2 illustrates the arrangement of a sensing module (sensing coil) in a paper transport path.

[0073] Figure 3 illustrates the signal pattern when printing on security paper.

[0074] Figure 4 illustrates a signal pattern according to the printing method.

[0075] FIG. 5 illustrates a printing device that provides a non-security paper printing restriction function.

[0076] Figure 6 illustrates a printing operation flowchart.

[0077] Figure 7 illustrates the paper flow during the skew correction operation and after the registration operation.

[0078] Figure 8 illustrates an example of adjusting the paper size and orientation of the paper tray.

[0079] Figure 9 shows an example of paper margin settings.

[0080] Figure 10 shows the time difference according to the printing operation.

[0081] Figure 11 shows a system configuration diagram of a printing device that provides a non-security paper printing restriction function.

[0082] (Definition of detection targets and detection modules)

[0083] The term “constituent material” as used in the present invention refers to the basic material constituting the paper used as a printing medium or the additional material included therein. The constituent material may include, for example, cellulose fibers, pigments, conductive or magnetic particles, electrically reactive coating materials, amorphous alloy wires, etc. Such constituent materials affect the electrical, magnetic, optical, physical, or chemical properties of the paper and are subject to detection.

[0084] Furthermore, in the present invention, the term “identification functional element” refers to an additional structure or device that is attached to, printed on, or inserted into paper and utilized to identify the type, security, authenticity, etc. of the paper. Accordingly, it may include not only a method of reading information stored therein (e.g., password, print data, etc.) but also a method of detecting the electromagnetic, optical, magnetic, chemical, or physical properties of the element. Examples may include, for instance, RFID (Radio Frequency Identification) tags, barcodes, QR codes, holograms, magnetic ink, amorphous alloy wires, fluorescent or luminescent materials, special inks, or surface patterns.

[0085] In particular, while RFID tags can be utilized to directly read stored data via wireless communication, they can also be used as a means to identify paper by detecting electromagnetic characteristics such as the response frequency characteristics and reflected signal intensity of the tag; similarly, barcodes or QR codes can determine security status by optically reading printed patterns while simultaneously detecting characteristics such as reflectance and contrast. Therefore, the method of direct information reading should also be interpreted as being included within the scope of 'characteristic detection' by the detection module of the present invention.

[0086] The sensing module detects the characteristics of the above-mentioned constituent material or identification functional element, and the term “characteristics” in this specification refers to

[0087] As a comprehensive concept including physical, chemical, optical, magnetic, or electrical properties, it may include the reflectance, transmittance, conductivity, magnetism, capacitance, resonance frequency, resistance value, reactivity, or other valid response signals of the detection target. These properties may be used individually or analyzed in combination of two or more properties, and the detection module generates a processed detection value based on them and provides it to the signal processing module or the discrimination unit.

[0088] In one embodiment, the sensing module includes an inductive sensor or a resonant circuit-based sensing device and can detect changes in the electromagnetic properties of a metallic component (e.g., amorphous alloy wire) contained in the paper. In this case, the sensing module utilizes changes in electrical properties (inductance, frequency, impedance, etc.) resulting from changes in the magnetic field generated by the metallic component to determine whether the security of the material incorporated, inserted, or attached to the paper is secure.

[0089] As another example, in the case of security paper containing a pattern printed with magnetic ink, the detection module can detect changes in magnetic flux density caused by magnetic particles contained in the ink.

[0090] As another example, methods for detecting the optical response characteristics of a holographic label whose reflectance changes at a specific wavelength, methods for identifying paper by analyzing the magnetic response pattern based on the Barkhausen effect that occurs when an external magnetic field is applied to an amorphous alloy wire and comparing it with a pre-registered standard, or methods for detecting the resonance characteristics or phase changes of surface acoustic waves (SAW) generated from a fine pattern formed on the surface of the paper can also be applied.

[0091] In this way, the detection module can be usefully utilized to determine whether it is security paper based on the characteristics of various constituent materials and functional elements for identification.

[0092] In the following description, an amorphous alloy wire (hereinafter referred to as a metal wire) is described as a representative example of a constituent material. Furthermore, while this specification describes the invention primarily with respect to a metal wire as one embodiment, the invention is not limited thereto, and other forms of constituent materials (e.g., magnetic particles, functional coating materials) or other examples of functional elements for identification (e.g., RFID tags, magnetic patterns, etc.) may also be included within the technical scope of the invention.

[0093] (Security Paper Composition Features)

[0094] Unlike paper generally used in printing devices (hereinafter referred to as non-security paper), security paper is a special paper manufactured by incorporating fine metallic particles of micro-level or smaller, or metal wires with a diameter and thickness of tens of μm or less, into the paper, attaching them to the outside, or inserting them into the inside.

[0095] For example, in the case of security paper manufactured by incorporating metal wires into pulp, as illustrated in (a) of [Fig. 1], the metal wires are arranged in a random pattern and distributed very irregularly. As a result, the metal wires may be present only in specific areas, overlap each other, or be densely packed at random intervals, and their lengths may also vary.

[0096] To determine whether it is such security paper, if the electrical or magnetic characteristic change caused by the metal wire contained in the paper is converted into an electrical signal and measured, it can be seen that a complex and irregular signal pattern is generated as in the signal pattern of [Fig. 1] a).

[0097] (Operation principle of the detection module (210))

[0098] The sensing module (210) detects changes in electrical characteristics due to changes in the magnetic field and includes a transducer (hereinafter, sensing coil (211)) that outputs changes in electrical characteristics, such as inductance, impedance, resonance frequency, amplitude, phase, and power loss, induced by a metal wire mixed with a component of paper passing through a magnetic field (hereinafter, sensing area) generated by a direct current or alternating current method, as an analog signal. The sensing coil (211) may be arranged independently of or integrated with the sensing processing unit (212) as shown in a) of [Fig. 2]. The sensing coil (211) is electrically connected to the sensing processing unit (212) through a signal transmission medium such as a wire or a pattern, and the sensing processing unit (212) converts the analog signal received from the sensing coil (211) into a digital signal and provides the converted signal as a detection value to the determination unit (200).

[0099] (Configuration method of the detection module (210))

[0100] The sensing module (210) can be configured in various ways depending on the system design. For example, a configuration in which a plurality of sensing coils (211) are connected to a single sensing processing unit (212) (1 main body : N sensing coil configuration) or a configuration in which a plurality of sensing coils (211) are connected to a plurality of sensing processing units (212) (N main bodies : N sensing coil configuration) is possible.

[0101] This structure can be flexibly applied to a printing device (10) or printing environment that requires multiple detection points.

[0102] In addition, when the sensing processing unit (212) and the sensing coil (211) are configured independently, the position of the sensing module (210) can be expressed or defined based on the position of the sensing coil (211). Such a configuration increases the flexibility of the placement of the sensing module (210), i.e., the sensing coil (211), and enables a system design that is adaptable to various printing environments and requirements.

[0103] (Selection of installation location for the detection module (210))

[0104] The independent sensing coil (211) included in the sensing module (210) may be positioned at one or more specific points on the printing path (88). It is positioned to face the moving paper at at least one specific point within the section including from a point adjacent to the pickup roller (41) to the front of the registration roller (43). Here, the point adjacent to the pickup roller (41) refers to a point where a boundary line is formed between a portion of the paper lifted by the pickup roller (41) and an area of ​​the paper remaining in a stacked state (stacked paper) when the paper is picked up by the pickup roller (41) from the paper tray (20).

[0105] For example, point A (point_A) shown in [Fig. 2] is a point adjacent to the pickup roller (41), and the front of the registration roller (43) becomes point B (point_B).

[0106] Since the sensing coil (211) detects changes in electrical characteristics due to changes in the magnetic field, its detection performance may be affected by the installation location. This is because the sensing coil is sensitive to external factors such as device operation around the location where it is placed, friction or contact with moving paper, and vibration. Additionally, some sections may be physically or structurally difficult to install the sensing coil (211), and as the number of paper trays (20) increases, the number of sensing coils (211), detection processing units (212), and detection modules (210) also increases, so an optimal placement method is required for economical and efficient operation.

[0107] (Optimal placement method of the detection module (210))

[0108] This relates to an optimal placement method for a sensing coil (211) or a sensing module (210).

[0109] In the case of an independent sensing module (210) in which the sensing processing unit (212) and the sensing coil (211) are configured independently, the sensing processing unit (212) can be freely placed inside or outside the printing device (10), so the location of the sensing module (210) is substantially used to represent the location of the sensing coil (211).

[0110] Accordingly, although the location of the sensing module (210) or the sensing coil (211) is described in this specification as the location of the sensing module (210), if the location is mentioned interchangeably, it should be understood that this refers to the same location (i.e., the location of the sensing coil (211)).

[0111] In the case of a printing device having three or more paper trays (20), including a manual feed tray (21),

[0112] At least one of the above-mentioned sensing modules (210) may be placed at a specific point on a transport path (88) through which papers supplied from a plurality of paper trays (20) commonly pass.

[0113] Looking at the printing path (88) of FIG. 5, it can be seen that the point where the detection module (210) is located is a common point through which paper supplied from the manual feed tray (21), as well as paper tray 1 (2001) and paper tray 2 (2002), all pass. Therefore, in the case of a multifunction printer having a total of three paper trays (20) including the manual feed tray (21), or having three or more paper trays (20), a certain section (hereinafter referred to as the 'common section') through which paper supplied from all paper trays (20) passes in common can be formed adjacent to the registration roller (43) or the registration sensor (33), and by installing an independent sensing coil (211) or an integrated detection module (210) in this section, efficient detection and the generation of a detection value can be achieved.

[0114] In the case of a printing device having one paper tray (20) excluding the manual feed tray (21), the specific point where the detection module (210) is placed is characterized by being a section including from a point adjacent to the pickup roller (41) to the front of the registration roller (43).

[0115] In another embodiment, for a printing device with a short printing path, a method is also provided to place the detection module (210) in an area extending from a point midway between the positions of the pickup roller (41) and the registration roller (43) in the printing path to a point adjacent to the pickup roller (41) in order to secure a number of detection values ​​greater than the level required to distinguish security paper.

[0116] (Identifying the source of the paper)

[0117] In all of the above methods, a sensing coil (211) or a detection module (210) may be additionally installed in front of another paper tray (20), and this can be used to identify the source of the supplied paper (paper tray (20)), distinguish individual papers during continuous printing, detect operation such as whether printing has started, and collect detection values.

[0118] Additionally, if a sensing module (210) or a sensing coil (211) is installed in a common section or in a part of each paper tray (20), another method of identifying the source of the supplied paper is to identify the source of the supplied paper (paper tray (20)) by checking whether the pickup roller (41) has started operating, or by sharing at least one of the output signals of the pickup sensor (31) and the feed sensor (32).

[0119] The sensing coil (211) placed at the aforementioned specific point forms a magnetic field and continuously outputs an analog signal generated according to the change in the magnetic field to the detection processing unit. The detection processing unit converts the provided analog signal into a digital signal to generate a detection value, and then stores the detection value for a certain period of time or transmits it externally according to a predetermined method. That is, the detection module (210) continuously detects changes in the magnetic field while operating and generates a detection value accordingly.

[0120] (Optional use or collection method of detection values)

[0121] Meanwhile, in the determination unit (200) using the above detection value, not all of the detection value is used,

[0122] Only data (detection values) from a specific point in time until the determination is completed is selectively used or collected to set a reference value for specific purposes, such as determining whether it is security paper, or to compare with a reference value or process the detection values.

[0123] To this end, the method by which the discrimination unit (200) selectively uses or collects the detection value may use at least one of the following methods.

[0124] 1. A method for selectively collecting detection values ​​after a specific point in time,

[0125] 2. A method that is continuously provided but selectively uses detection values ​​after a specific point in time, or

[0126] 3. A method in which detection values ​​after a specific point in time are processed primarily by applying filtering based on predefined criteria, statistical analysis, or other techniques.

[0127] (Definition of a specific point in time)

[0128] The specific point in time referred to in this specification is among the detection values ​​continuously generated by the detection module (210),

[0129] It refers to the point at which detection values ​​are selectively used or collection begins according to one of the methods explained earlier.

[0130] The printing device illustrated in [Fig. 5] includes the following configuration.

[0131] - Multiple sensors:

[0132] Paper tray sensor 1 (3001), paper tray sensor 2 (3002), feed sensor 1 (3201), feed sensor 2 (3202), registration sensor (33), exit sensor (34), empty pool sensor (35), door open sensor (39), and other sensors provided for printing operations, etc.

[0133] - Multiple rollers and drive units:

[0134] Pickup drive unit (pickup drive unit 1 (5101), pickup drive unit 2 (5102)), registration drive unit (53), discharge drive unit (54), transfer drive unit (61), fixing drive unit (62), etc., for driving rollers positioned at specific locations such as pickup roller 1 (4101), pickup roller 2 (4102), registration roller (43), transfer roller (44), fixing roller (45), etc.

[0135] According to one embodiment of the present invention, the printing device includes one or more sensors positioned on the printing path (88) among the plurality of sensors and positioned in front of or behind the detection module (210) along the printing path (88), and the driving unit includes a driving unit for driving a roller positioned at a specific location.

[0136] Here, the front of the detection module (210) refers to an area including from a point adjacent to the pickup roller to the front of the detection module (210), and the rear refers to an area including from the detection module (210) to the front of the registration roller (43).

[0137] (Setting a specific point in time)

[0138] The determination unit (200) can set the time based on various conditions such as the following to determine whether it is security paper based on a specific time.

[0139] 1. Sensor detection or drive unit operation criteria

[0140] A specific point in time can be set by adding or subtracting a certain amount of time immediately or based on the point in time when paper is detected by one or more sensors placed in front or behind the detection module (210), or based on the point in time when the operation of the drive unit driving the roller placed at the specific location is detected.

[0141] For example, the point in time when paper is detected by the register sensor located in the middle of the print path can be set as a specific point in time, or a point in time obtained by adding a certain amount of time (e.g., 0.3 seconds) from that point. Alternatively, the point in time when the rotation of the register roller begins can be set as a specific point in time immediately or 0.2 seconds later.

[0142] 2. When the detected value / processed data deviates from the standard

[0143] A specific point in time can be set immediately or by adding or subtracting a certain amount of time from the point in time when it is determined that at least one of the received detection value or the processing data generated based on the detection value deviates from a specific criterion. For example, a point in time when the rate of change of the detection value changes rapidly above a threshold is detected, and a point in time after a certain amount of time has elapsed since that point in time is set as the specific point in time.

[0144] 3. Previous paper identification completed or non-detected status

[0145] A specific point in time can be set when a preset time has elapsed after the security paper identification for the previous paper is completed, or when the state in which the previous paper is not detected exceeds a preset threshold time.

[0146] For example, if 0.5 seconds have elapsed since the time when the security status of the previous paper was determined, or if the state in which the previous paper is no longer detected exceeds a certain threshold time (e.g., 1 second), that time is set as a new specific time.

[0147] 4. A state where the detected value is maintained below a certain threshold.

[0148] A specific point in time can be set as a point in time after a preset threshold time has elapsed, in which at least one of the received detection value or the processing data generated based on the detection value is below a specific standard.

[0149] For example, if a state where the rate of change of the detected value is almost non-existent persists for more than 2 seconds, the period thereafter can be considered as the reference point.

[0150] 5. After waking from sleep mode or applying power

[0151] A specific point in time can be set based on the time immediately after sleep mode is released, the time immediately after the system power is turned on, or after a preset time has elapsed. In this case, the system can be configured to collect detection values ​​and start analysis after a preset time (e.g., 1 second) has elapsed for system stabilization.

[0152] (Additional settings at a specific point in time)

[0153] In addition, the above specific point in time may be additionally set in combination with at least one of the following conditions.

[0154] 1. At the point in time when paper is detected by one of the plurality of sensors, immediately or at a point in time with a certain amount of time added or subtracted.

[0155] For example, after paper is detected by the feed sensor (32), if paper is also detected by the registration sensor (33, register sensor) within a preset time (e.g., 800ms), it is determined that the paper has been transported normally through the linkage between the detection times of the two sensors, and the detection time of the registration sensor (33) can be set to a specific time.

[0156] Another example is a timing correction based on the detection repeatability of a single specific sensor, in which the feed sensor (32) can output detection signals multiple times when the paper is transported while shaking intermittently. In this case, the specific time point can be set to 0.2 seconds after the last detection signal is collected, so that only the signal after the paper is stably positioned can be analyzed.

[0157] 2. Based on the point in time when the operation of the above-mentioned driving unit is detected, immediately or at a point in time with a certain amount of time added or subtracted.

[0158] For example, if paper is detected by the registration sensor (33) within a preset time (e.g., 800ms) after the operation of the pickup drive unit (51) driving the pickup roller (41) is detected, it is determined that the paper has been transported normally through the linkage between the pickup roller (41) and the registration sensor (33) detection point, and the registration sensor (33) detection point can be set to a specific point.

[0159] 3. A point in time that satisfies other predefined conditions may be combined with the specific point in time condition set above and utilized at a specific point in time. These other conditions may include software or environmental conditions, such as system settings, status history, or external inputs, which are not directly related to sensor detection or drive unit operation.

[0160]

[0161] (Definition of processing data based on detection values)

[0162] In one embodiment of the present invention,

[0163] Processing data used to set a specific point in time or to determine whether it is security paper is,

[0164] It is generated based on a detected value and can be generated according to at least one of the following signal processing methods.

[0165] 1. Data generated using time-domain signal processing:

[0166] The result of statistical processing of the detected value itself (e.g., mean, minimum value, median, moving average, etc.), the amount of change, rate of change, secondary amount of change of the detected value (e.g., change in the rate of change with respect to time, i.e., acceleration component), or the frequency of occurrence thereof,

[0167] Alternatively, processing data may be included that is set based on an average value, minimum value, median value, or similar statistical reference value calculated in a predetermined reference interval within a time series of detected values, and includes the result of comparing the reference value with the detected value, change amount, change rate, or secondary change amount in a subsequent interval.

[0168] 2. Data generated using frequency domain signal processing:

[0169] Processing data including the result of a Fourier transform for the detected value or the amount of change, rate of change, or second-order change, and the result of frequency spectrum analysis calculated therefrom, the result of detection of a specific frequency component, the result of peak analysis, or the result of spectrogram analysis, etc.

[0170] 3. Data generated using pattern recognition and extended signal processing methods:

[0171] It may include wavelet transform results for detection values, distribution results or judgment scores derived through machine learning or deep learning-based signal pattern recognition algorithms, reinforcement learning-based analysis results based on pre-learned policies or value functions, or judgment information generated by analyzing time series patterns of detection values ​​collected at regular intervals.

[0172] (Function of the signal processing module (220))

[0173] The above-mentioned determination unit (200) determines whether paper is detected by a plurality of sensors or whether operation of a specific driving unit has started, in order to set a specific point in time for a detection value or to set a determination point for determining whether it is security paper. This is made possible through the configuration of a signal processing module (220).

[0174] The signal processing module (220) according to the present invention may be configured to perform at least one of the following functions: sharing a signal output from a sensor placed at a specific location among the plurality of sensors with the printer controller (300) and providing it to the determination unit (200); or detecting the start of operation of a roller placed at a specific location among the drive units and converting it into an electrical signal or a digital signal and providing it.

[0175] Such a function can be specifically implemented through the following embodiments.

[0176] As a first embodiment, there is a method of sharing the output signal of a sensor. The signal processing module (220) shares the signal output from a sensor placed at a specific location among the plurality of sensors (multiple sensors that detect a state related to a printing operation and output an electrical signal including paper position information and paper tray (20) loading information) with the printer controller (300), and provides the shared signal to the discrimination unit (200) so that it can recognize that paper has been detected by the corresponding sensor. At this time, the sharing method may be selected and applied appropriately according to the sensor configuration characteristics of the printing device (10), and can be broadly classified into two methods.

[0177] The first method is a method of sharing through direct electrical connection. This involves connecting a separate signal line in parallel to the signal line (including a line or pattern) of a sensor placed at a specific location among the plurality of sensors, or including a filtering electronic circuit using passive components such as a resistor, inductor, or capacitor on the corresponding signal line, thereby providing the output signal of the sensor to the determination unit (200) as a signal having a logic value such as that of the printer controller (300).

[0178] Such examples may include a structure as illustrated in ① of [Fig. 11].

[0179] Additionally, the signal may be shared by configuring the circuit in an open collector or open drain manner on the signal line. In this case, the output signal of the sensor is set as the input signal of the circuit, including a logic gate or a microprocessor, and the method provides the determination unit (200) with a signal having a new logic value that maintains the logic value of the input signal or a signal having a new logic value that has undergone a specific operation.

[0180] Such examples can be implemented in the form of the example shown in ① or ② of [Fig. 11].

[0181] Here, electrical connection means transmitting the output signal of a sensor to other components (e.g., microcontrollers, PLCs, data acquisition devices, etc.) through wires or circuits, and this may include various forms of digital signals such as logic signals, analog voltage or current signals, PWM, SPI, I²C, and UART.

[0182] The second method is a method of sharing the output signal of a sensor by electrically isolating it. This method interposes an isolation circuit between the sensor placed at a specific location where the output signal is to be shared and the signal processing module (220), thereby ensuring that the sensor signal is safely transmitted without being directly connected. For example, the signal of a sensor placed at a specific location can be detected using an isolation circuit based on an optocoupler, transformer, capacitor, or capacitance or magnetic field method, and transmitted to the discrimination unit (200) in an isolated state. This configuration can be selectively applied for the purpose of protecting the signal processing module (220) and the discrimination unit (200) from external electrical interference and reducing electromagnetic interference.

[0183] Such an example can be implemented as a structure shown as ① or ② in [Fig. 11].

[0184] Next, the second embodiment is a method of providing a detection signal generated by detecting the start of operation of a drive unit to a determination unit (200). In order to accurately determine the internal operating state of the printing device (10), the start of operation of a drive unit that drives a roller placed at a specific location is detected, and the detected detection signal is provided to the determination unit (200). To this end, an electronic circuit may be configured to be connected in series or in parallel to one of the signal line or power line connecting the drive unit to be operated and the printer controller (300).

[0185] The printer controller (300) can detect a change in voltage or current caused by the operation of a specific drive unit or a control signal transmitted to control the drive unit, or can separately detect whether the drive unit is operating by using a sensor to check the operating status. The detected signal is converted into an electrical signal or a digital signal and provided as a detection signal to the determination unit (200). The signal provision method can be implemented by selecting one or more of a push-pull, open collector, or open drain structure.

[0186] This example can be implemented with the configuration shown in ③ of [Fig. 11].

[0187] (Characteristics of the detection value signal pattern)

[0188] As shown in the distribution of metal wires in the security paper of [Fig. 1] a), the metal wires included in the security paper are irregularly distributed, and accordingly, the signal pattern of the security paper shown indicates that the detection values ​​detected by the detection module (210) are irregularly measured, such as changes in height and the time of appearance, depending on the area with metal wires and the area without metal wires and the density of the metal wires.

[0189] In addition, as shown in [Fig. 7], which illustrates the signal pattern measured when printing one sheet of security paper, and in [Fig. 8] b), which shows the signal pattern that appears during continuous printing, the detection value provided by the detection module (210) shows an irregular signal pattern that changes continuously over time.

[0190] In addition, high-frequency signals generated during the operation of the printing device, which appear superimposed on the irregular signal patterns according to the characteristics of the security paper, can also make the aforementioned irregular signal patterns into more complex signal patterns.

[0191] The high-frequency signal components that can be generated depending on the operation of the printing device are as follows.

[0192] For example, when power is applied, the sensing module (210) continuously detects changes in the electrical characteristics of the sensing coil (211) according to a preset cycle without a separate detection start or end criterion (condition) and outputs the detection result.

[0193] Therefore, even if no object (non-security paper, security paper) exists in the detection area of ​​the sensing coil (211), a change occurs in the magnetic field formed by the sensing coil (211) due to the motor and high-voltage device driven when the printing device performs a self-check function, transfer, or fixing process, and this causes a change in the inductance and impedance of the sensing coil (211), thereby generating an incorrect detection value. The discrimination unit (200) that receives such a detection value causes a discrimination error in which it incorrectly identifies the paper as security paper even though it is actually ordinary paper.

[0194] Another example involves physical contact (including intermittent contact) between the paper and the sensing module. The sensing coil (211) of the sensing module (210) is positioned to face the paper on the printing path. Since the paper does not move flat but moves up and down in a swaying motion, intermittent physical contact occurs between the sensing coil (211) and the paper as the paper moves along the transport path, depending on changes in movement speed and pattern.

[0195] In addition, if the sensing coil (211) is positioned adjacent to the pickup roller, re-pickup operations occur frequently due to wear or malfunction of the roller, and if the transfer roller is worn or malfunctions, the movement speed and paper flow fluctuate, so the time to reach the next position becomes inconsistent.

[0196] In addition, as shown in [Fig. 5], when the sensing coil (211) is positioned in front of the registration sensor (35), the up-and-down shaking of the paper increases during the skew correction process, and as a result, physical contact frequently occurs between the sensing coil (211) adjacent to the registration sensor (35).

[0197] Such physical contact exerts mechanical (physical), electrical, and magnetic effects on the sensing coil (211), changes the impedance and inductance of the sensing coil (211), and causes magnetic field distortion, thereby changing the electrical characteristics of the current or voltage. As a result, an incorrect detection result (false detection) occurs. The detection unit (200), which collects and uses these detection results to determine whether it is security paper, causes a detection error in which it incorrectly identifies it as security paper even though it is actually ordinary paper.

[0198] In conclusion, the structural characteristics of the security paper induce complex changes in the temporal continuity and frequency characteristics of the detection values. Electromagnetic interference factors caused by the internal operation of the printing device and mechanical transport characteristics of the moving paper (contact, friction, etc.) interact in combination, resulting in a complex signal pattern that is non-linear and highly likely to have signals concentrated in a specific frequency spectrum or peaks occurring at specific frequencies. In contrast, since the non-security paper is composed of relatively uniform material and components, the signal detected when passing through the detection module (210) is highly likely to exhibit a constant pattern or uniform frequency components.

[0199] (How to identify security paper)

[0200] According to one embodiment, the determination unit (200) can determine whether it is security paper in real time or at the time of determination by using a detection value collected through a detection module (210) and processing data generated based on the detection value. At this time, analysis beyond simple comparison of detection values ​​is required, and at least one of time domain analysis, frequency domain analysis, pattern recognition, and extended signal processing methods may be applied.

[0201]

[0202] i) Security paper identification using Time-Domain Analysis

[0203] 1. It is possible to determine whether a detected value or the result of statistically processing the detected value (e.g., mean, minimum value, median, standard deviation, moving average, etc.) is a security paper by comparing it with the security paper standard.

[0204] For example, by comparing the detected value or the statistically processed value with the detected value or the result of statistical processing of the detected value (average, minimum value, median, standard deviation, moving average, etc.) when there is no paper or when general paper is detected, if the comparison value satisfies the security paper criteria (above a specific threshold or outside a specific threshold range), it can be determined as security paper.

[0205] 2. A predetermined reference interval is set within the time series of the detected value, and an average value, minimum value, median value, or similar statistical reference value derived from that interval is set as a reference. If the result of comparing the reference value with the detected value, change amount, change rate, or secondary change amount of the subsequent interval satisfies the security paper criteria (specific threshold value or threshold range), it can be determined as security paper.

[0206] 3. If the pattern analyzed for the amount of change, rate of change, and secondary amount of change (e.g., change in rate of change over time, i.e., acceleration component) of the detected value satisfies the security paper criteria (presence of a specific pattern), it can be identified as security paper.

[0207] For example, if the slope of the rate of change exceeds a certain threshold, it can be identified as security paper.

[0208] 4. By analyzing the frequency of the detected value or its derived value (statistical processing result, amount of change, rate of change, secondary amount of change, etc.), if a pattern exceeding a specific condition is repeated, this can be utilized as a characteristic of the security paper.

[0209] For example, it can be identified as security paper at a frequency where a specific detection value or rate of change exceeds a specific range.

[0210]

[0211] ii) Security paper identification using Frequency-Domain Analysis

[0212] 1. A Fourier transform (e.g., FFT, DFT) is performed on the detected value or its change amount, rate of change, or second change amount to derive frequency components, and if the security paper criteria (presence of specific frequency components) are satisfied, it can be determined to be security paper.

[0213] 2. It is possible to determine whether it is security paper by analyzing the frequency spectrum of the Fourier transform result, comparing the energy concentration in a specific band (detection of specific frequency components) and peak analysis results with security paper standards (whether there is a section concentrated at a specific frequency, whether a peak exceeding a specific value occurs, etc.).

[0214] 3. If necessary, the frequency change pattern over time can be visually identified through spectrogram analysis, and if the security paper criteria (whether there is a specific section of the security paper) are met, it can be identified as security paper.

[0215]

[0216] iii) Security paper identification based on pattern recognition and extended signal analysis

[0217] The presence of specific patterns within regularly collected detection signals can play a crucial role in identifying security paper, and security paper can be identified by applying various signal processing and artificial intelligence technologies.

[0218] 1. Patterns within time series data can be compared with previously learned security paper patterns (standards) to determine if they are security paper if they exhibit a similarity of a certain level or higher (e.g., 85% or higher). Similarity can be expressed as distance-based calculation, a score matrix, or probability-based classification.

[0219] 2. By extracting local signal characteristics in the time-frequency domain through wavelet transform and comparing them with security paper criteria (local high-frequency component change patterns in a specific time interval), it is possible to determine whether it is security paper.

[0220] 3. By applying machine learning or deep learning techniques (CNN, LSTM, transfer learning, etc.) to train the model on the temporal pattern of the detected values, and comparing the input detected values ​​with security paper criteria (security paper model), it is possible to classify whether they correspond to security paper.

[0221] 4. Reinforcement learning-based methods can also be applied, in which case the security paper status can be determined based on whether the security paper criteria are met, based on a pre-learned policy or value function.

[0222] In this way, by analyzing detection values ​​using various methods based on time, frequency, and pattern recognition, the presence of security paper can be determined with high precision. Each analysis method can be used individually or in combination, which can contribute to increasing the accuracy and reliability of the system.

[0223] (Selection of security paper standard values)

[0224] According to one embodiment, it is preferable that the security paper standard be set for each model, taking into account the differences in structure and operation mechanism of the printing device (10) by model. In addition, even for the same model, the detection signal pattern and numerical value may differ depending on environmental factors such as the sensing sensitivity of the detection module (210), electromagnetic interference inside and outside the device, and mechanical vibration. Therefore, even within the same model, adjustment (tuning) of the security paper standard value may be required depending on the installation environment. To set the security paper standard, multiple types of non-security paper and one or more security papers are secured, and individual printing is performed on each paper to collect detection values. Subsequently, one or more of the following feature extraction methods are applied to the collected data to derive valid security paper features that can clearly distinguish between security paper and non-security paper, and then the security paper standard is set by using the corresponding features individually or in combination.

[0225] i) Feature extraction based on time domain analysis

[0226] Time domain analysis is a method that applies the same analysis method to the detection values ​​of security paper and non-security paper, respectively, and then compares the numerical or pattern differences between the two groups to derive features (e.g., specific thresholds or distribution differences, specific threshold ranges, etc.) capable of distinguishing whether a material is security paper.

[0227] 1. Comparison based on detected values ​​or statistical processing

[0228] The detection values ​​of each paper group are directly compared, and values ​​or distribution ranges that appear specifically in security paper are derived as security paper characteristics.

[0229] Alternatively, for the detection values ​​of each group, statistical values ​​such as the average, median, standard deviation, and moving average are calculated for a portion or the entire range, and then security paper characteristics are derived based on the statistical distribution and numerical differences.

[0230] 2. Analysis of Change Amount and Rate of Change Compared to Default Values

[0231] A predetermined reference interval is set within the time series of detection values ​​of each paper group, and the average value, minimum value, median value, or similar statistical processing result derived from that interval is set as the default value, and security paper characteristics are derived by comparing the default value with the detection value, amount of change, rate of change, or secondary rate of change of subsequent intervals.

[0232] 3. Analysis of Change Amount and Rate of Change

[0233] For the time series of detection values ​​of each group, the amount of change, the rate of change, or the secondary rate of change (acceleration component) is calculated, and the pattern difference of the derived values ​​is compared to derive security paper features.

[0234] 4. Frequency-based analysis

[0235] Measure the frequency at which a detection value or statistical processing data of the detection value, a change amount, a change rate, and a secondary change rate appear within a specific value or range, and derive frequency characteristics that can distinguish between security paper and non-security paper.

[0236] ii) Feature extraction based on frequency domain analysis

[0237] Frequency domain analysis converts the detection signal into the frequency domain and derives the characteristics of the security paper based on the differences in frequency components appearing in the security paper and non-security paper, respectively.

[0238] 1. Fourier transform (e.g., FFT, DFT) based analysis: The detection values ​​or derived data (statistical processing values, change amounts, change rates, second-order change rates, etc.) of each group are converted into the frequency domain to analyze the presence of specific frequency components and derive features that can distinguish between security paper and non-security paper.

[0239] 2. By analyzing the frequency spectrum from the Fourier transform results of each group, analyzing the frequency components of the amount or rate of change of each group's detection value, analyzing the frequency components of the second rate of change of each group's detection value, comparing peak detection and specific frequencies, or using spectrogram analysis results if necessary, features (specific frequency range, specific interval between the two groups, etc.) that can distinguish between security paper and non-security paper are derived.

[0240] iii) Feature extraction based on pattern recognition and extended signal analysis

[0241] 1. Wavelet transform-based analysis: Features of security paper are extracted by analyzing changes in local high-frequency components in a specific time interval.

[0242] 2. Machine learning and deep learning-based pattern analysis: By applying CNN, LSTM, or Transfer Learning models, the time-series characteristics of the detected values ​​are learned, and signal patterns meaningful for classifying security paper and non-security paper are derived.

[0243] 3. Reinforcement learning-based signal analysis: A dataset is constructed and trained using two groups of detection values ​​in various scenarios combining different types of paper and printing device operating environments, and characteristics exhibiting high reliability or policy classification success rates in security paper detection signals are derived as features to distinguish between security paper and non-security paper.

[0244] By systematically comparing and analyzing security and non-security paper in this manner, it is possible to derive security paper characteristics optimized for device models and installation environments, and establish security paper standards (reference values) based on these characteristics. These security paper reference values ​​provide benefits such as improved accuracy in security paper identification, correction of deviations between devices, and reduction of false positive rates.

[0245] (Setting and adjusting the determination point)

[0246] Below, an example of the setting and adjustment of the determination point of the present invention is described in more detail.

[0247] The printing device (10) according to the present embodiment includes a plurality of sensors, a signal processing module (220), and a discrimination unit (200).

[0248] It is configured so that the determination point can be dynamically set or adjusted based on detection information of the paper moving along the printing path (88) and operation information of the driving unit. That is, if the size of the paper to be printed is small or the paper has a short length in the direction, the printing timing can be advanced, and if the paper is large or has a long length, the determination point can be delayed by taking into account the relatively long travel time.

[0249] According to one embodiment, a second sensor positioned at a specific location among a plurality of sensors, for example, behind the detection module (210), detects the presence of paper and provides the detection result to a signal processing module. The signal processing module (220) is configured to share the signal with a determination unit (200), and the determination unit uses this signal to recognize that paper has been detected by the second sensor and can set a determination time immediately or considering a preset delay time based on that time. This configuration corresponds to that described in claim 6.

[0250] According to another embodiment, the printing device (10) may include one or more paper tray sensors (30), and as shown in [Fig. 8], the paper tray sensors (30) are configured to output an electrical signal in response to the operation of a detection switch that detects the position of the paper width guide and the paper length guide of the paper tray (20).

[0251] Accordingly, a printing device (20) having multiple paper trays (20) can provide information on the size and orientation of the paper loaded in each paper tray (20) through each paper tray sensor (30), and can utilize information on the distance the picked-up paper travels according to the position of each paper tray (20) and the sensors placed on the traveling printing path.

[0252] Additionally, a roller is positioned at the rear of the sensing module (210), and a second driving unit for driving this roller is included.

[0253] The signal processing module (220) can provide the output signal of the paper tray sensor (30) or the signal detecting the start time of operation of the second driving unit to the determination unit (200). Here, as a preferred embodiment for the second driving unit, the second driving unit that rotates a roller placed at a specific position among the driving units may be a registration driving unit (53) that drives the registration roller (43).

[0254] The determination unit (200) may adjust the determination point set in claim 6 by considering various input information such as the size and orientation of the paper, the start time of operation of the driving unit, etc., or may set a new determination point based on the information itself.

[0255] In addition, the drive start signal of the second drive unit can be utilized as a separate determination reference point, and can be used to adjust the determination point set based on the second sensor detection, or to set the determination point based on an independent standard.

[0256] In addition, a detailed embodiment in which the drive start signal of the second drive unit is utilized for setting or adjusting the determination point is described by including it in the example of optimized adjustment of the determination point considering the transfer operation characteristics described below.

[0257] In this way, the method of utilizing the paper tray sensor (30) or the driving start signal of the second driving unit enables flexible judgment by statically setting or dynamically adjusting the determination point according to various variables such as the type, direction, size, travel length, and feeding method of the paper, and can contribute to improving printing stability and accuracy.

[0258] (Optimization of determination timing using warrior behavior characteristics)

[0259] According to one embodiment of the present invention, by optimizing the timing of security paper identification by utilizing the transfer operation characteristics of a printing device, the accuracy and reliability of security paper identification can be improved.

[0260] A typical laser printing device has a non-printable area of ​​about 3-5 mm at the edge of the paper due to its hardware characteristics, i.e., a margin, and as shown in [Fig. 9], the margin settings of commercial document creation software are often set to 1 inch (2.54 cm) on all sides.

[0261] Under such margin settings, when the paper passes through the registration roller (43) and between the transfer roller (44) and the transfer drum / transfer belt (60) during printing, a non-transfer section is formed where no image is transferred to the paper for a length of the margin. (See FIG. 7)

[0262] In particular, when a document containing margins is printed, no image is transferred to the paper over a certain section while passing through the transfer area; thus, more identification data can be collected by utilizing this non-transferred section. As a result, the error probability of incorrectly identifying security paper as non-security paper is reduced, and consequently, the performance of the security document protection function is improved.

[0263] The determination point must be set to secure sufficient data for determination, and at the same time, ensure that even if printing is stopped due to the document being identified as non-security paper, no document content is printed at all or only a very small portion is printed, making reproduction difficult.

[0264] For example, in an environment where a document with default margin settings is printed, the optimal determination point is the point adjusted by the time it takes for the paper leading edge to pass through the non-transfer section within the transfer area.

[0265] In order to calculate the above optimal determination point, it is necessary to determine the distance of the transmission-free section and the time required to pass through that section.

[0266] This time can be derived by sharing signals or other control information received from multiple sensors connected to the printer controller (300) without adding a separate sensor.

[0267] In particular, during the time calculation process, a section in which the paper moves at a constant speed is identified, and the starting point of that section is specified as a reference position. Then, a determination point can be set or adjusted based on the time required for the paper to move a specified distance (e.g., 1 inch) from that position. At this time, the reference point must be the point in time when the paper begins to move from the specified reference position, and a preset time value is added to this reference point to determine the final determination point.

[0268] This is intended to ensure that the determination point is adjusted in conjunction with the reference point when the reference point changes due to paper size, orientation, or internal driving characteristics of the printing device.

[0269] As a result, the timing of determination can be flexibly and accurately determined through time calculation based on a fixed distance and speed, which is an effective method that can provide high determination reliability.

[0270] By comparing and analyzing the printing operation signals of the printing process through an exemplary embodiment, the above-described method for setting the reference time is presented.

[0271] (1-1), (2-1), and (3-1) of FIG. 10 are graphs showing the time difference that occurs between the operation of the feed sensor 2 (3202, FEED#2) and the registration drive unit (53, RG CL) when printing three sheets of the same paper in succession.

[0272] Specifically, the time taken from the point in time when the feed sensor 2 (3202) detects the paper (LOW→HIGH transition) to the point in time when the registration drive unit (53) starts operating (LOW→HIGH transition) was measured, and it was confirmed that a significant time difference of about 71ms to 178ms occurs depending on the variation in internal operating conditions.

[0273] In this way, if the detection time of feed sensor 2 (3202) is used as a reference time, a time difference of up to about 178 ms may occur, so there is a limit to reliability in security paper detection systems that require setting a fixed detection time or precise timing adjustment.

[0274] On the other hand, (1-2) and (2-2) of [Fig. 10] represent the flow of detection signals from the start of operation of the registration drive unit (53) until the paper traveling along the printing path (88) reaches and is detected by the exit sensor (36, EXIT) of the fuser exit unit. In the measurement, only a minute difference of about 5 ms occurred, which falls within the acceptable error range for most printing devices (10), so the time required from the registration drive unit (53) to the exit sensor (34) can be evaluated as virtually constant.

[0275] Generally, the printing device (10) performs a registration operation to precisely align the leading edge of the paper with the image starting point in order to accurately transfer the image formed on the transfer drum / transfer belt (60) onto the paper. Once this operation is completed, the paper, which was stopped in front of the registration roller (43), is transported at a constant speed to the transfer starting position (the point where the transfer roller (44) and the transfer drum / belt (60) meet) to perform the transfer operation. In the transfer section of this printing path (88), the speed is maintained at a constant speed, and the accuracy of the time calculation is ensured.

[0276] Accordingly, according to one aspect of the present invention, when the discrimination unit (200) selects a reference point for setting or adjusting the discrimination point, it is most preferable to use the point at which the movement of the paper begins in the registration roller (43) as the reference. Since this reference point almost exactly coincides with the start of operation of the registration drive unit (53) due to the structure of the printing device, deviations caused by signal fluctuations between sensors or mechanical delays are minimized, and accurate and consistent setting of the discrimination point becomes possible. This method of selecting a reference point can operate stably in various environments and printing conditions, and is particularly advantageous in printing environments where minute differences between security paper and non-security paper must be quickly and accurately distinguished.

[0277] The present invention is sufficiently usable even in a printing device (10) that provides a borderless printing function.

[0278] When applying a determination point where printing is limited to a maximum length of 1 inch on a printing device that provides a non-security paper restriction function by modifying a laser printer that supports borderless printing, if the paper to be printed is determined to be non-security paper, and the paper is Letter size (8.5 inches × 11 inches, 21.59 cm × 27.94 cm), the actual printing area is limited to a maximum of 11.76% in width and 9.09% in height. Since this is a level where the document content cannot be fully reproduced, it can be effectively applied even in environments where printing restrictions are required for security policies.

[0279] In conclusion, the present invention optimizes the timing of security paper identification by utilizing the transfer operation characteristics and non-transfer section of the printing device (10), thereby limiting the output to 0% in a printing environment where basic margin settings are applied, and limiting the output to only up to 12% of the content even in a special printing environment where printing is done without margins.

[0280] Furthermore, the analysis time for security paper identification can be adjusted by the time spent moving through the non-transfer section, thereby securing more detection data. This increase in data enables precise analysis of the irregular signal patterns of security paper, which consequently improves identification performance and allows for more reliable identification.

[0281] Accordingly, by utilizing the transfer operation characteristics and non-transfer section of the printing device (10), it will not only maximize security paper identification performance but also serve as a realistic alternative that can effectively support the security policies of companies and institutions.

[0282] (Other: Method for distinguishing individual sheets)

[0283] According to one embodiment of the present invention, the detection value provided from the detection module (210) to the determination unit (200) is a result value that comprehensively reflects the physical characteristics of the security paper and the operating conditions of the printing device (10). This detection value is continuously collected during the printing operation, and if the magnitude of the detection value is graphed with respect to the time axis, a signal pattern according to the flow of time is shown.

[0284] [Fig. 3] is an example of a graph showing the magnitude values ​​of paper moving along a printing path (88) and the corresponding detection values ​​of a detection module (210) in chronological order when printing a single-page document.

[0285] The X-axis of the graph is set to time and the Y-axis to the magnitude of the detection value, and continuous detection values ​​are expressed from the point in time when paper is picked up from the paper tray (20) (①), when the leading edge of the paper enters the detection module (210) (②), and when the trailing edge of the paper passes through the detection area of ​​the detection module and exits (③).

[0286] [Fig. 4] represents the entire detection value received by the detection module (210) for a certain period of time, including the standby state, printing operation execution state, and printing end state of the printing device (10), as a signal pattern.

[0287] [Fig. 4] a) shows the signal pattern when printing only one single page, and b) shows the signal pattern when printing multiple pages or a single document continuously.

[0288] Looking at the signal pattern b) of [Fig. 4], it is confirmed that there are limitations to simply comparing the magnitudes of detection values ​​in order to identify individual papers passing through the detection module (210) in a continuous printing situation. For example, there are sections where it is difficult to clearly distinguish whether the detection value is due to the paper, due to noise, the trailing area of ​​the previous paper, or the leading area of ​​the current paper.

[0289] Therefore, criteria or conditions are required to clearly distinguish individual sheets.

[0290] In one embodiment of the present invention, as a condition for accurately identifying a section where paper is not detected,

[0291] A paper non-detection state is determined when one or more of the detection values ​​during a specific time interval or processing data based on the detection values ​​(statistical processing values ​​of the detection values, amount of change of the detection values, rate of change, secondary rate of change, or frequency analysis of the values, pattern analysis results, etc.) are below a preset standard. This method serves as an important basis for determining the spacing between individual papers in a continuous printing environment and for independently setting each paper as a target for determining whether it is a security paper. In another embodiment, instead of adding a separate sensor or detection means to distinguish individual papers, the signal of a sensor placed at a specific location on the printing path (88) among a plurality of sensors already included in the existing printing device is utilized.

[0292] For example, the output signals of a pickup sensor (31) that detects paper picked up by a pickup roller (41) from a paper tray (20), a feed sensor (32) that detects paper when the picked-up paper is fed and moved, and a registration sensor (33) that detects paper moving to a registration roller (43) are shared and used to distinguish individual papers. The output signals of each sensor are shared with the discrimination unit (200) through a signal processing module (220).

[0293] [Explanation of the symbol]

[0294] 10 printing device

[0295] 20 Paper Tray (Tray) 21 Manual Feed Tray (MP Tray)

[0296] 23 Bin

[0297] 2001 Tray 1 (Tray 1) 2002 Tray 2 (Tray 2)

[0298] 30 Paper tray sensor 31 Pickup sensor

[0299] 32 Feed Sensor 33 Registration Sensor

[0300] 34 Exit Sensor 35 BinFull Sensor

[0301] 39 Door Open Sensor

[0302] 3001 Tray Sensor 1 3002 Tray Sensor 2 3201 Feed Sensor 1 3202 Feed Sensor 2

[0303] 41 Pickup roller 42 Feed roller

[0304] 43 Registration Roller 44 Transfer Roller

[0305] 45 Fixing Roller

[0306] 4101 Pickup Roller 1 4102 Pickup Roller 2

[0307] 51 Pickup drive unit 52 Feed drive unit

[0308] 53 Registration drive unit 54 Discharge drive unit

[0309] 5101 Pickup Drive Unit 1 5102 Pickup Drive Unit 2

[0310] 60 Transfer Drum / Transfer Belt 61 Transfer Drive

[0311] 62 Fixing drive unit

[0312] 88 Transfer Path (Paper Path)

[0313] 200 Discrimination unit 210 Detection module

[0314] 211 Sensing coil 212 Detection processing unit

[0315] 220 Signal Processing Module

[0316] 300 printer controller

Claims

1. In a printing device that restricts printing on non-security paper, A paper tray capable of loading paper of various sizes in horizontal or vertical directions and a manual feed unit; A plurality of sensors that detect a state related to a printing job and output an electrical signal including paper position information and paper tray loading information; A printer controller that analyzes electrical signals output from the plurality of sensors to determine the paper transport state and the operating state of the printing device, and controls a drive unit that drives a roller to move the paper to the next position; A sensing module that detects the characteristics of a constituent material or an identification functional element included in or attached to the above paper, and provides a processed sensing value based thereon; Sharing the signal output from a sensor placed at a specific location among the plurality of sensors with the printer controller, A signal processing module that detects the initiation of operation of a drive unit of a roller positioned at a specific location among the above drive units, and converts this into an electrical signal or a digital signal and provides it; Using the detection value provided from the above detection module and / or the signal provided from the signal processing module, Compares in real-time detection values ​​collected after a specific point in time or processing data generated based on detection values, and if predefined security paper criteria are satisfied, immediately determines whether it is security paper, or A printing device comprising a determination unit that, when a determination point arrives, determines whether a predefined security paper standard is satisfied using a detection value collected up to that point or processing data generated based on the detection value.

2. In Claim 1, The above-mentioned determination unit is, The detection value used to determine whether the above paper is security paper is characterized by being processed in at least one of the following ways: (i) A method for selectively collecting detection values ​​after a specific point in time, (ii) a method that is continuously provided but selectively uses detection values ​​after a specific point in time, or (iii) A method in which detection values ​​after a specific point in time are processed primarily, including filtering based on predefined criteria, statistical analysis, frequency analysis, pattern analysis, or artificial intelligence-based signal processing techniques.

3. In Claims 1 and 2, The above printing device is, Among the above plurality of sensors, they are arranged along the printing path, and It includes a sensor whose position is in front or behind the detection module, and It includes a drive unit that drives a roller positioned at a specific location among the above drive units, A printing device characterized in that a specific point in time is set as a point in time derived according to at least one of the following conditions: (i) A point in time immediately or with a certain amount of time added or subtracted from the point in time when paper is detected by the sensor or operation of the drive unit is detected. (ii) A point in time immediately or with a certain amount of time added or subtracted from the point in time when at least one of the received detection value or the processing data generated based on the detection value is determined to deviate from a specific criterion. (iii) After the security paper identification of the previous paper is completed, a preset time has elapsed or the state in which the previous paper is not detected exceeds a preset threshold time. (iv) a point in time after a preset threshold time has elapsed, in which at least one of the received detection value or the processing data generated based on the detection value is below a specific criterion. (v) Immediately after exiting sleep mode or after the system power is turned on, or after a preset time has elapsed 4. In claim 1 or claim 3, The processing data generated based on the above detection value is, A printing device characterized by being generated by at least one of the following signal processing methods: (i) Time domain signal processing method: Comparing the detected value itself or the results of statistical processing it with predefined criteria, Analyze the amount of change, rate of change, secondary change (acceleration component), or frequency of occurrence of the detected value, Processed data generated by setting an average value, minimum value, median value, or a similar statistical reference value calculated within a predetermined reference interval in a time series of detected values, and comparing the reference value with the detected value, change amount, rate of change, or secondary change amount of a subsequent interval, or by comparing and analyzing the frequency of occurrence thereof. ii) Frequency domain signal processing method: Processed data including the results of a Fourier transform for a detected value or its change amount, rate of change, or second-order change amount, frequency spectrum analysis, detection of a specific frequency component, peak analysis, or spectrogram analysis. (iii) Pattern recognition and extended signal processing methods: Wavelet transform on detected values, machine learning or deep learning-based signal pattern recognition, reinforcement learning-based analysis, or processed data generated by analyzing patterns of detected values ​​collected at regular intervals.

5. In Claim 3, A printing device characterized in that the above specific point in time can be additionally set to at least one of the following: (i) at the point in time when paper is detected by one of the plurality of sensors, immediately or at a point in time with or without a certain amount of time added or subtracted, (ii) Based on the point in time when the operation of the above-mentioned driving unit is detected, immediately or at a point in time with a certain amount of time added or subtracted, (iii) A point in time when other predefined conditions are satisfied.

6. In Claim 1, The above printing device is, A sensor positioned at a specific location among the plurality of sensors above, comprising a second sensor positioned at the rear of the detection module, The above signal processing module is characterized by sharing the corresponding signal with the discrimination unit when the second sensor detects paper. The above-mentioned determination unit is, Using the output signal of the second sensor received from the signal processing module, it is recognized that paper has been detected by the second sensor, and A printing device characterized by setting a determination point based on the time when paper is detected, either immediately or based on a pre-set time.

7. In Claim 1 or Claim 6, As a sensor placed at a specific location among the plurality of sensors above, It includes a plurality of paper tray sensors that detect width and length guide positions when adjusting the paper tray and output an electrical signal, As a driving unit for driving a roller positioned at the above specific location, It includes a second driving unit that drives a roller positioned at the rear of the sensing module, The above signal processing module is, The above multiple paper tray sensor output signals are shared and provided to the determination unit, or Detects the start of operation of the second driving unit and converts it into an electrical signal or a digital signal to provide to the determination unit. The above-mentioned determination unit is, A printing device characterized by performing one or more of the following methods to set a determination point by considering the size and orientation of the paper to be determined, or to adjust a determination point set according to claim 6: i) A method of analyzing the output signals of the plurality of paper tray sensors to derive paper size and paper orientation for each paper tray and setting or adjusting the determination point based thereon, ii) A method for setting or adjusting a determination point using an operation start detection signal of a second driving unit provided by the signal processing module.

8. In Claim 7, The above second driving unit is, A printing device characterized by being a driving unit that drives a registration roller.

9. In Claims 1 and 7, The above-mentioned determination unit is, Based on the start time of operation of the drive unit that rotates the roller positioned at a specific location among the above drive units, In setting or adjusting the determination point, After the leading edge of the above paper reaches between the transfer roller and the transfer belt or the transfer roller and the transfer drum, Set the time required to move up to 1 inch (2.54 cm) as the maximum elapsed time, and The determination point is within the range from 0 seconds to the maximum elapsed time, A printing device characterized by being adjustable to a predetermined time.

10. In Claim 1, The above-mentioned determination unit, in order to determine whether it is security paper, A printing device characterized by applying at least one of the following discrimination logics: (i) Time domain analysis logic: Logic for determining whether a value is security paper based on the result of directly comparing a detected value, comparing a statistically processed value (e.g., mean, minimum value, median, standard deviation, moving average, etc.), or comparing at least one of a change amount, rate of change, secondary rate of change (acceleration component), and the frequency of occurrence of such values ​​with a predefined security paper standard; (ii) Frequency domain analysis logic: Logic for performing a Fourier transform on a detected value or its amount of change, rate of change, or second rate of change, and determining at least one of the corresponding frequency component, spectrum analysis result, whether a peak in a specific frequency band is detected, or spectrogram analysis result by comparing it with a security paper standard; (iii) Pattern recognition and extended signal analysis logic: A logic for determining whether a signal is security paper by analyzing the pattern of signal data and applying at least one of wavelet transform, machine learning or deep learning-based signal analysis, and reinforcement learning-based signal discrimination method.

11. In Claim 1, The above detection module is, A printing device characterized by being positioned to face the moving paper at at least one specific point within a section of the transfer path including from a point adjacent to a pick-up roller to the front of a registration roller.

12. In Claim 11, In the case of a printing device having a total of three or more paper trays, including a manual feed tray, At least one of the above-mentioned sensing modules is characterized by being positioned at a specific point on a transport path through which the papers supplied from the plurality of paper trays commonly pass.

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