JPH07116147A - Ultrasonic apparatus for detecing fingerprints - Google Patents

Abstract

PURPOSE:To detect fingerprints by atomizing a solution with elastic vibration generated by an ultrasonic exciter, spraying the mist on the surface of an object to form a thin film of a substance contained in the mist on the surface, and reacting substances contained in fingerprints on the surface with the substance contained in the mist. CONSTITUTION:When a piece of paper is fed from an inlet, the paper width is measured by a sensor 4, and rotating supports 3 support the paper according to the width and feed the paper toward an outlet. A solution of ninhydrine is sprayed uniformly on both sides of the paper by an atomizing device 1 to form a thin film of ninhydrine. The paper sprayed with the solution passes between air blowers 2 and fed toward the outlet. If there are fingerprints on the paper, coloring is observed due to the reaction with ninhydrine. Thus the structure is simple and can be driven with a low electric power consumption.

Description

Detailed Description of the Invention

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to atomizing a solution by elastic vibration generated by an ultrasonic exciter, spraying the mist onto the surface of an object, and depositing a thin film of a substance contained in the mist on the surface. The present invention relates to an ultrasonic fingerprint detection device that detects a fingerprint by forming a substance contained in the fog and a substance contained in a fingerprint attached to the surface to react with each other.

2. Description of the Related Art As a conventional method for detecting a fingerprint attached to paper or the like, a method of applying ninhydrin is generally used. This utilizes the fact that amino acids contained in human sweat react with ninhydrin to turn purple. When detecting fingerprints attached to paper such as newspaper, report paper, or high-quality paper (referred to as plain paper here), fingerprints are attached to a 0.5% ninhydrin solution using an organic solvent such as acetone as a solvent. Soak the plain paper with a solution of sufficient amount by dipping the plain paper or applying the solution to the plain paper with a brush.
Then, the reaction was completed by applying a heat treatment. The advantage of this method is that fingerprints can be detected clearly without bleeding. However, when characters are written on plain paper with an oil-based ballpoint pen, etc., the organic solvent not only adversely affects the detection of fingerprints, but also damages the powerful information that should be obtained other than fingerprints such as handwriting verification. Will be given. Further, in the case of paper such as thermal paper, alteration due to an organic solvent or heat occurs, and the surface of the paper is immediately turned blackish, which makes it difficult to detect fingerprints. In this way, it is difficult to detect fingerprints in the case of paper such as thermal paper by the conventional method, and in the case of plain paper, it damages powerful information that should be obtained other than fingerprints such as handwriting verification. was there. Furthermore, since organic solvents are used, there is a risk of environmental pollution and fire.

The object of the present invention is to efficiently print fingerprints attached to special papers such as plain paper or thermal paper by atomizing a ninhydrin solution by ultrasonic vibration. An object of the present invention is to provide an ultrasonic fingerprint detection device that can be well detected, can be driven with low power consumption and low voltage, and can be small, lightweight, and simple in structure.

An ultrasonic fingerprint detecting apparatus according to a first aspect of the invention is an ultrasonic fingerprint detecting apparatus U _{i in} which a vibration plate having a large number of minute through holes is fixed to a piezoelectric vibrator. (I
= 1, 2, ..., N), the solution is atomized by the elastic vibration generated, and the mist is sprayed on the surface of the object to form a thin film of the substance contained in the mist on the surface. In the ultrasonic fingerprint detecting device for detecting the fingerprint by reacting the substance contained in the surface with the substance contained in the fingerprint attached to the surface, the means for forming the thin film on the surface is a film thickness of the thin film. And a means for promoting the reaction, the film thickness control means includes means for controlling the particle size of the mist and the amount of the mist, and the reaction promoting means includes the surface on which the mist is sprayed. And a means for drying, humidifying, or heating the piezoelectric vibrator, which comprises a piezoelectric ceramic and electrodes P and Q. The electrodes P and Q are formed on both end surfaces of the piezoelectric ceramic perpendicular to the thickness direction. And the above P comprises a set of interdigital electrodes,
By applying a frequency substantially equal to the voltage and the resonance frequency of the piezoelectric vibrator between the terminal T _Q at terminal T _P1 and the electrode Q of one of the two terminals T _P1 and T _P2 of the interdigital electrodes , A circuit for driving the ultrasonic exciter is provided, wherein the drive circuit comprises a step-up coil connected between a DC power source and the terminal T _P1 , and an output voltage terminal at the terminal T _P1 . The connected input voltage terminal is the terminal T _P2
A transistor that receives the piezoelectricity appearing at the terminal T _P2 as a feedback voltage by being connected to the drive circuit, and the drive circuit constitutes an oscillation circuit using the transistor as an amplification element and the ultrasonic exciter as a resonance circuit. The resonance frequency of the piezoelectric vibrator is substantially equal to the resonance frequency of the composite of the piezoelectric vibrator and the vibration plate. The ultrasonic fingerprint detecting apparatus according to claim 2, wherein the piezoelectric vibrator has a rectangular plate whose length-width dimension ratio is close to 1 and is not equal to 1 or 2 sides out of 3 sides. Is a rectangular prism that is not close to 1 and is not equal to 1, and the vibrating plate is integrally fixed to at least one end surface of the piezoelectric vibrator having the electrode P or Q. To do. The ultrasonic fingerprint detecting device according to claim 3, wherein the solution is a ninhydrin solution of about 0.5 to 5%, and the solvent of the ninhydrin solution is acetone and n-.
It is characterized by comprising hexane or other organic solvent or water. The ultrasonic fingerprint detecting apparatus according to claim 4 is characterized in that the object is made of newspaper, thermal paper, high-quality paper or other paper. The ultrasonic fingerprint detecting device according to claim 5, wherein a means for supplying the solution to the diaphragm supports the ultrasonic exciter, a liquid storage chamber for containing the solution, and a plurality of through holes. And a liquid-retaining material that absorbs the solution, the support holding the complex in a predetermined position with respect to a fixed object, and at least the ultrasonic excitation of the support. The portion that comes into contact with the container is made of expanded polystyrene or other material having a lower acoustic impedance than the piezoelectric vibrator, and the diaphragm is constantly or intermittently contacted with the liquid retaining material and is absorbed by the liquid retaining material. The solution is atomized. The ultrasonic fingerprint detecting apparatus according to claim 6 is characterized in that the solution supply means includes a tube for supplying the solution from the liquid storage chamber to the diaphragm.

The ultrasonic fingerprint detecting apparatus of the present invention atomizes the solution by the elastic vibration generated by the ultrasonic exciter and sprays it on the surface of the object, and forms a thin film of the substance contained in the mist on the surface. The fingerprint is detected by reacting the substance contained in the fog with the substance contained in the fingerprint attached to the surface. The ultrasonic fingerprint detection apparatus of the present invention includes an ultrasonic wave exciter for generating fog, and means for controlling the film thickness of a thin film, means for promoting a reaction, and a circuit for driving the ultrasonic wave exciter. . By having such a simple structure, it is possible to reduce the size and weight of the device. When the ultrasonic fingerprint detecting device of the present invention is driven, an electric signal having a frequency substantially equal to the resonance frequency of the composite of the piezoelectric vibrator and the diaphragm is applied to the piezoelectric vibrator, and the piezoelectric vibrator is excited. The excitation of the piezoelectric vibrator vibrates the diaphragm, so that the solution supplied to the diaphragm is atomized through the holes provided in the diaphragm. Atomization through the holes promotes fineness and uniformity of the particles, and can increase atomization efficiency. In addition, since the atomization efficiency is high, a large amount of atomization can be realized with low power consumption, self-excited driving is possible, and it is easy to drive with a battery, so it can respond to environmental changes such as temperature and low power consumption. Can be driven. The piezoelectric vibrator is composed of a piezoelectric ceramic, electrodes P and Q, and electrodes P and Q.
Are formed on both end surfaces of the piezoelectric ceramic which are perpendicular to the thickness direction. At this time, a structure in which the electrode P is composed of a pair of interdigital electrodes is adopted, and two terminals T of the interdigital electrode are adopted.
By applying a frequency substantially equal to the voltage and the resonance frequency of the piezoelectric vibrator between the terminal T _Q at one terminal T _P1 and the electrode Q of the _P1 and T _P2, ultrasonic exciter is driven, the piezoelectric The oscillator is excited. By adopting the piezoelectric vibrator with such a simple structure, not only can the ultrasonic fingerprint detecting device be downsized, but also the atomization efficiency can be improved, and further, the self-excited driving can be performed, so that the low vibration can be achieved. It is possible to drive at low voltage with power consumption. In the circuit for driving the ultrasonic exciter, a boosting coil is connected between the DC power supply and the terminal T _P1 . It also comprises a transistor whose output voltage terminal is connected to terminal T _P1 and whose input voltage terminal is connected to terminal T _P2 . This transistor is for receiving the piezoelectricity appearing at the terminal T _P2 as a feedback voltage. In this way, the drive circuit of the ultrasonic exciter constitutes an oscillation circuit in which the transistor is an amplification element and the ultrasonic exciter is a resonance circuit, and the frequency can be automatically tracked to the resonance frequency of the piezoelectric vibrator. I am trying. In addition, by providing a circuit using the counter electromotive voltage of the coil, the piezoelectric vibrator can be driven at a voltage higher than the power supply voltage. This counter electromotive voltage circuit generates a high voltage by utilizing the characteristics of the coil, and is advantageous in terms of price, weight and volume as compared with the use of a transformer. Further, it is possible to bring about features such as a simple circuit configuration and a small size, and good power supply efficiency and frequency characteristics. FIG. 13 shows a block diagram of a three-terminal system self-exciting circuit. The three-terminal system has three terminals for connection with the piezoelectric vibrator, and each terminal is used for the purpose of being independent of each other. An electrode on one side of the piezoelectric vibrator is divided into a drive electrode D for applying a voltage and a feedback electrode F for feeding back a part of electric power to an amplifier,
The other electrode is grounded as a ground electrode G. In the ultrasonic fingerprint detecting apparatus of the present invention, the electrode P in the piezoelectric vibrator is composed of one set of interdigital electrodes, and the interdigital electrodes correspond to the D electrode and the F electrode, and the terminals T _P1 and T _P2.
Correspond to the terminals provided on the D electrode and the F electrode, respectively. The electrode Q corresponds to the ground electrode G. Even when the piezoelectric vibrator is thin, self-excited oscillation driving can be performed by using the interdigital transducer as shown in the present invention. FIG.
In this method, since the phase is shifted by 180 ° by the power amplifier, self-excited oscillation occurs at the frequency at which the phase is shifted by 180 ° between the D electrode and the F electrode of the piezoelectric vibrator. As the piezoelectric vibrator, a rectangular plate having a length-width dimension ratio close to 1 and not equal to 1 or a rectangular prism having a dimension ratio of two sides out of three sides close to 1 and not equal to 1 is adopted. As a result, the combined vibration of the composite of the piezoelectric vibrator and the vibration plate is enhanced, and the atomization efficiency is promoted. Further, since the vibration plate is integrally and continuously fixed to at least one end surface having the electrode P or Q of the piezoelectric vibrator, the vibration plate serves as a fixed end at the joint between the piezoelectric vibrator and the vibration plate. It vibrates in the form of a cantilever. Therefore, the liquid supplied to the vibrating plate is atomized by the elastic vibration, and is efficiently dissipated as a mist toward the upper side perpendicular to the vibrating plate. The means for supplying the solution to the vibrating plate includes a support for supporting the ultrasonic exciter, a liquid storage chamber for storing the solution, and a liquid retaining material having a large number of through holes and having a large liquid absorption ability. . The liquid retaining material sucks the solution from the liquid storage chamber and supplies the solution to the diaphragm. The support holds the composite body of the piezoelectric vibrator and the vibration plate at a predetermined position with respect to the fixed object. At this time, it is desirable to reduce the contact area between the support and the ultrasonic exciter as much as possible, but at least the portion of the support that contacts the ultrasonic exciter has a higher acoustic impedance than a piezoelectric vibrator such as Styrofoam. By adopting a substance with low vibration, it is possible to prevent the excitation of the piezoelectric vibrator from being dissipated by propagating in the support itself, the fixed object, or the solution, and to vibrate the diaphragm efficiently. Can be increased. In this way, the vibrating plate constantly or intermittently contacts the liquid retaining material, whereby the solution absorbed in the liquid retaining material can be efficiently atomized. Further, since the means for supplying the solution is provided with the tube for supplying the solution from the liquid storage chamber to the diaphragm, the solution can be supplied to the diaphragm without using the liquid retaining material. The ninhydrin reaction can be used to detect fingerprints because the atomized solution is composed of about 0.5 to 5% ninhydrin solution. This utilizes the fact that amino acids contained in human sweat react with ninhydrin to give a purple coloration. In the ultrasonic fingerprint detection apparatus of the present invention, a ninhydrin solution having an organic solvent such as acetone as a solvent or a ninhydrin solution having water as a solvent is atomized, and the mist is sprayed onto a surface of paper or the like to form a ninhydrin thin film on the surface of the paper. To form. At this time, since the means for controlling the film thickness of the thin film includes means for controlling the fog particle diameter and the fog amount,
It is possible to generate a large amount of fog having a very small particle size. Further, the means for accelerating the reaction includes a means for drying, heating, or heating and drying while humidifying the surface of the paper after spraying the ninhydrin solution, so that the paper is attached to the surface of the paper. The reaction between the amino acid contained in the fingerprint and ninhydrin can be completed.
In this way, the fingerprint can be detected. Moreover, the ultrasonic fingerprint detection device of the present invention can detect fingerprints using an aqueous ninhydrin solution, and can detect fingerprints without using an organic solvent. Therefore, it can be applied to a special paper such as a thermal paper, and the problem of environmental pollution and the risk of fire can be eliminated, and the adverse effect on the human body can be eliminated. Further, the structure of the device is simple and can be automated, which can bring about a great improvement in the working environment.

1 is a sectional view showing an embodiment of an ultrasonic fingerprint detecting apparatus of the present invention. This embodiment comprises an atomizing device 1, a blower 2, a rotary support 3, a sensor 4 and a self-excited drive circuit 5. However, in FIG. 1, the drive circuit 5 is omitted. Further, two sets of the rotation support tools 3 are provided in a direction perpendicular to the traveling direction of the paper inserted from the entrance and discharged from the exit, and press the both sides of the inserted paper. When the ultrasonic fingerprint detecting device is driven, when the paper is inserted from the entrance, the width of the paper is measured by the sensor 4, and the rotation support tool 3 is set so as to hold the minimum necessary portions on both sides of the paper according to the width. . The rotary supports 3 of each set rotate in the direction of the arrow, and the paper inserted from the entrance of the apparatus is sequentially sent by the rotary supports 3 toward the exit. Two of the four atomizing devices 1 are located near the entrance of the device at the top and bottom of the paper, respectively, and the other two are located near the center of the device at the top and bottom of the paper, respectively. A 0.5% aqueous solution of ninhydrin is uniformly sprayed on the front and back of the paper by the two atomizing devices 1 near the inlet, and after a short distance, the two atomizing devices 1 near the center.
Is sprayed again, and a thin film of ninhydrin is formed on the front and back of the paper. The blower 2 can blow not only normal-temperature air but also warm air and high-temperature steam onto the paper, and the paper after the solution is sprayed passes between the air blowers 2 as described above and the outlet. Sent to. In this way, a series of operations is automated. If fingerprints are attached to the paper, coloring due to the ninhydrin reaction is seen.
It should be noted that an exhaust port is provided in the ceiling part or other part of the device, and a system for collecting exhaust gas in the device from the exhaust port, collecting ninhydrin or a ninhydrin solution from the exhaust gas, and supplying the system to the atomization device 1 again Is also possible. By introducing such a system, ninhydrin can be used without being leaked to the outside and without waste. Therefore, the problem of environmental pollution and the adverse effect on the human body can be eliminated, and the working environment can be greatly improved. FIG. 2 is a partial perspective view showing the inside of the ultrasonic fingerprint detecting apparatus of FIG. In this embodiment, four atomizing devices 1 located at the bottom of the paper are arranged side by side so that the entire paper is sprayed with mist. One set of rotary support 3 is composed of two rotary bodies 6, and when the two rotary bodies 6 sandwich and rotate the paper, the paper is delivered to the adjacent rotary support 3. In this way, the paper for which the atomization operation has been completed is sent to the blower 2. FIG. 3 is a cross-sectional view showing an embodiment of the atomizing device 1 and its periphery. The atomizing device 1 is composed of a piezoelectric vibrator 7 and a vibration plate 8, and the vibration plate 8 is fixed to one end surface of the piezoelectric vibrator 7 so as to be integrally connected to the piezoelectric vibrator 7. The atomization device 1 is supported by a support 9. One end of the liquid retaining material 10 is in contact with one end surface of the diaphragm 8, and the solution sucked from the other end of the liquid retaining material 10 is supplied to the one end surface of the diaphragm 8. And is atomized from the other end surface of the diaphragm 8. FIG. 4 is a plan view of the piezoelectric vibrator 7 and the diaphragm 8. The piezoelectric vibrator 7 is composed of a piezoelectric ceramic 11, an electrode Q (not shown in FIG. 4) and a comb-shaped electrode P. The piezoelectric ceramic 11 is made of a rectangular plate-shaped TDK72A material (product name), and has a length of 17 mm, a width of 20 mm, and a thickness of 1 mm. The direction of the polarization axis of the piezoelectric ceramic 11 coincides with the thickness direction, and the electrodes Q and the interdigital electrodes P are formed on both end surfaces perpendicular to the thickness direction. The electrode Q is made of an aluminum thin film and covers almost the entire one end surface of the piezoelectric ceramic 11. The interdigital electrode P is made of an aluminum thin film,
It has 6 pairs of electrode fingers, the electrode period length is 2 mm, and the electrode crossing width is 4.8 mm. A terminal T _Q is attached to the electrode Q, and terminals T _P1 and T _P2 are attached to the interdigital electrode P. The diaphragm 8 is made of nickel and has a length of 2
The width is 3 mm, the width is 20 mm, and the thickness is 0.05 mm. The vibration plate 8 has a length of 2 mm at one end face in the length direction,
The bonding area has a width of 20 mm, and the bonding area is fixed to the piezoelectric vibrator 7 via the electrode Q. FIG. 5 is a partially enlarged sectional view of the diaphragm 8 taken along a plane perpendicular to the plate surface. The diaphragm 8 is provided with a large number of fine holes 12 penetrating in its thickness direction. In FIG. 5, the vertical cross-sectional shape and dimensions of the hole 12 are shown. The holes 12 have a mortar shape and are arranged at equal pitches. One opening area is larger than the other opening area. The larger opening area is the inlet side and its diameter is 0.1 mm, and the smaller opening area is the outlet side, and its diameter is 0.01 mm. FIG. 6 is a partially enlarged plan view of the diaphragm 8. However, the diaphragm 8 is provided with holes 12
The shape, arrangement and dimensions of the holes 12 are shown as viewed from the outlet side of the. When the atomizing device 1 of FIG. 3 is driven, when an electric signal having a frequency substantially equal to the resonance frequency of the composite of the piezoelectric vibrator 7 and the diaphragm 8 is input to the piezoelectric vibrator 7 via the terminal T _P1 , the piezoelectric vibrator 7 Vibration is piezoelectrically excited in the vibrator 7. Since the vibrating plate 8 has a structure in which the vibrating plate 8 is integrally connected and fixed to one end surface of the piezoelectric vibrator 7, the vibrating plate 8 is bonded to the piezoelectric vibrator 7 as the piezoelectric vibrator 7 vibrates. It is vibrated in the form of a cantilever whose fixed end is the area. This vibration is bending vibration and effectively functions to atomize the liquid. The contact portion of the support tool 9 with the piezoelectric vibrator 7 is made of expanded polystyrene or the like having a lower acoustic impedance than the piezoelectric vibrator 7, so that ultrasonic waves from the piezoelectric vibrator 7 propagate to the support tool 9 itself and are lost. It is preventing. The liquid-retaining material 10 is made of sponge or the like having a lower acoustic impedance and a larger liquid-absorbing ability than the piezoelectric vibrator 7, and ultrasonic waves from the piezoelectric vibrator 7 propagate through the liquid-retaining material 10 into the solution and dissipate. To prevent it. In this way, the diaphragm 8 is efficiently vibrated. With the vibration of the diaphragm 8, the solution sucked up by the liquid retaining material 10 is guided to the hole 12 by the capillary phenomenon. When the solution passes through the holes 12, the passing area of the solution in the holes 12 decreases from the inlet side to the outlet side, so that the solution is subjected to the squeezing action by the holes 12 and vibrates as fine and uniform particles. It flows out to the upper part of the plate 8 and is efficiently atomized. FIG. 7 is a block diagram showing an embodiment of the drive circuit 5. In FIG. 7, M, F, and G denote the main electrode M, the return electrode F, and the ground electrode G, respectively.
The return electrode F corresponds to a pair of interdigital electrodes P, and the ground electrode G corresponds to the electrode Q. Terminals T _P1 and T _P2 are provided on the main electrode M and the return electrode F, respectively,
The terminal T _Q is provided on the ground electrode G. Terminal T _P1
Most of the vibration excited in the piezoelectric vibrator 7 by applying a voltage to the piezoelectric vibrator 7 via the electromagnetic wave is propagated to the diaphragm 8 and the rest is applied to the piezoelectric vibrator 7 according to the vibration. It is output from the terminal T _P2 as a voltage having a phase opposite to the applied voltage. By repeating this operation, positive feedback self-excited oscillation occurs. That is, an electric signal having a frequency substantially equal to the resonance frequency of the composite body is stably supplied to the piezoelectric vibrator 7 following the change in ambient temperature. In this way, it is possible to always maintain its own optimum oscillation state.
Therefore, the problem that the resonance frequency of the composite is deviated due to heat generation or the like, which is a problem during the separately-excited driving, and the oscillation condition is deteriorated, is solved. In addition, it is possible to configure the circuit with a very small number of components such as one coil L ₁ , one transistor _Tr , two resistors R ₁ and R ₂ , and one diode D. Moreover, even though the number of parts is small, a DC power supply can be used and power efficiency is high, which enables downsizing of the power supply. When a direct current voltage of, for example, 0 to 10 V is applied to the drive circuit 5 of FIG. 7 by adjusting the value of the coil L ₁ ,
An alternating voltage of about 60 V _pp at maximum can be applied to the main electrode M. At this time, an electric signal of about 1 V _pp is taken out from the feedback electrode F. In this way, the drive circuit 5 can apply an AC voltage, which is about 6 times the DC power supply voltage, to the piezoelectric vibrator 7. In the atomizing device 1 of FIG. 3, the atomizing operation was confirmed by applying a DC voltage of 6 V or more to the main electrode M. The fog particles were extremely small and uniform. According to the atomizing device 1 of FIG. 3, it is possible to stably atomize a very small amount of fog over a long period of time. FIG. 8 is a characteristic diagram showing the relationship between the amplitude and frequency of the admittance between the main electrode M and the ground electrode G in the composite body of the piezoelectric vibrator 7 and the diaphragm 8. The admittance has a frequency of approximately 94.
A peak was shown at 1 kHz, and the maximum atomization amount was obtained in the vicinity of this peak. FIG. 9 is a characteristic diagram showing the relationship between the phase and frequency of the admittance in FIG. Since the frequency when the phase is zero indicates the resonance frequency, it can be seen that one of the resonance frequencies is approximately 94.1 kHz. Further, it was confirmed that the resonance frequency of 94.1 kHz substantially matches the resonance frequency of the piezoelectric vibrator 7 alone. FIG. 10 is a characteristic diagram showing the relationship between the susceptance and the conductance in the vicinity of the resonance frequency in the composite of the piezoelectric vibrator 7 and the diaphragm 8, that is, the diagram showing the admittance circle in the vicinity of the resonance frequency. The maximum value of the conductance when the susceptance is zero occurs at 94.2 kHz, and this value almost coincides with the resonance frequency in the composite body of the piezoelectric vibrator 7 and the diaphragm 8. FIG. 11 shows a fingerprint detected on the fine paper. Hot steam was blown from the blower 2. Without using acetone as a solvent
It was confirmed that the detection can be performed at almost the same level even in an aqueous solution. At the same time, it can be seen that the use of the ultrasonic fingerprint detection device of the present invention requires a very small amount of the solution, which leads to a great improvement in the working environment. FIG. 12 shows a fingerprint detected on the thermal paper. A blower at room temperature was blown from the blower 2. It was confirmed that fingerprint detection on thermal paper was possible by adopting the atomization process of ninhydrin aqueous solution.

According to the ultrasonic fingerprint detecting apparatus of the present invention,
Approximately equal to the resonance frequency of the composite of the piezoelectric vibrator and the diaphragm.
Applying an AC signal with a certain frequency to the piezoelectric vibrator
This causes the piezoelectric vibrator to vibrate. The vibration of this piezoelectric vibrator
Since the vibrating plate vibrates, the vibrating plate must have the necessary objects for fingerprint detection.
Atomizing a solution by supplying a solution containing the quality
You can At this time, the diaphragm should be provided with many fine holes.
Therefore, the solution supplied to the vibrating plate
It is atomized through. Atomization through the holes is the fineness of the particles,
Can promote homogeneity and yet increase atomization efficiency
It In addition, the opening area of one of the holes is
If you use a large structure, the larger opening
By setting the smaller one as the outlet side, the solution passing through the hole
The area decreases from the inlet side to the outlet side. Therefore,
When the liquid passes through the hole, it is subjected to the throttling action. as a result,
The diameter of the particles becomes even finer and more uniform. Therefore, the fingerprint
By spraying such a mist on the surface of the worn object
A thin film of the substance contained in the solution is formed on the surface of the object.
Is made. When the substance reacts with the fingerprint component,
The fingerprint can be detected. Ultrasonic fingerprint detection device of the present invention
In addition to an ultrasonic exciter for generating fog, a thin film
Thickness control means, reaction promoting means, and ultrasonic exciter drive circuit
Is equipped with. Hot steam is used as a solution to accelerate the reaction.
It includes means for spraying the paper after spraying. Thin film
The thickness control means controls the voltage applied to the piezoelectric vibrator.
Means, etc. are included. In this way, a series of operations
Automation is possible. About 0.5 to 5 as a solution to be atomized
% Ninhydrin solution to detect fingerprints
The ninhydrin reaction can be used for output. Ninhi
As the solvent for the drin solution, an organic solvent such as acetone or
Can use water. Ninhide like this
Atomize the phosphorus solution and spray the mist onto a surface such as paper.
When forming a thin film of nhydrin on the surface of the paper, the thin film
The thickness control means includes means for controlling the fog particle size and the fog amount.
This creates a large amount of fog with a very small particle size.
It becomes possible. Also, the reaction promoting means is ninhydr
Dry or heat the surface of the paper after spraying the phosphorus solution,
This includes means such as heating and drying while humidifying.
And can complete the ninhydrin reaction
It In this way, the fingerprint can be detected. Only
Also, in the ultrasonic fingerprint detection device of the present invention, ninhydrin aqueous solution is used.
It is possible to detect fingerprints using a liquid and use an organic solvent.
The fingerprint can be detected without being present. Therefore, the feeling
It can be used for special paper such as hot paper,
It also eliminates pollution problems and fire hazards, and has a negative impact on the human body.
The sound can be eliminated. Furthermore, the structure of the device is simple and can be automated.
Because it is possible, it can bring about an improvement in the working environment.
it can. As a piezoelectric vibrator, a piezoelectric ceramic and its piezoelectric ceramic
Electrodes formed on both end faces perpendicular to the thickness direction
By adopting a simple structure consisting of P and Q,
Atomization of liquid with high efficiency, which can downsize the device.
It is possible to drive with low power consumption. Also, the electrode P
Piezoelectric vibrator by using the interdigital transducer as
Even if the thickness is small, self-excited driving is possible. Obey
Low power consumption in a form that can respond to environmental changes such as temperature.
Driving with low power and low voltage is possible. Long as a piezoelectric vibrator
Rectangular shape whose dimensional ratio of width and width is close to 1 and not equal to 1
The dimensional ratio of the plate or two of the three sides is close to 1, and
By adopting a rectangular prism that is not equal to 1,
The combined vibration of the composite of the electric vibrator and the diaphragm is enhanced, and the fog
Efficiency is promoted. In addition, the vibration plate
Structure in which at least one end face is integrally connected and fixed
By adopting, the vibrating plate joins the piezoelectric vibrator.
Since it vibrates with the fixed end as, it is supplied to the diaphragm.
The liquid is atomized by its elastic vibration and directed toward the upper side of the diaphragm.
It is released as fog. Composite of piezoelectric vibrator and diaphragm
The resonance frequency at
By adopting a structure that is almost equal, the piezoelectric vibration
Since the combined vibration of the complex of the pendulum and the diaphragm is enhanced,
The amount generated will increase further. For the drive circuit of ultrasonic exciter
Is a DC power supply and terminal T_P1And a voltage booster connected between
And the output voltage terminal is terminal T_P1Connected to the input voltage end
Child is terminal T_P2Includes a transistor connected to
This transistor is used as an amplification element and an ultrasonic exciter
An oscillation circuit serving as a vibration circuit is configured. Like this
The frequency automatically tracks the resonance frequency of the piezoelectric vibrator.
I am trying to do it. In addition, the back electromotive force of the coil
Since the circuit used for the
The piezoelectric vibrator can be driven with a high voltage. The opposite
The electromotive voltage circuit has a simple circuit configuration and is small in size.
And good frequency characteristics. The means for supplying the liquid to the diaphragm is
A support for supporting the ultrasonic exciter and a reservoir for containing the liquid
From the chamber and the substance with large liquid absorption capacity that has many through holes
Stable for a long time by including
It is possible to realize various atomization. Also supply liquid
Means for supplying liquid from the liquid storage chamber to the diaphragm.
By installing a tube, liquid can be stored without using a liquid retaining material.
It becomes possible to supply to the diaphragm. Such as support tools and liquid retention materials
The surface of what is in direct contact with an ultrasonic exciter
A material that makes it difficult for the vibration of the pendulum to propagate to the surface or liquid.
Quality has been adopted. In this way, the diaphragm can be used efficiently.
Since it vibrates, it is possible to atomize the liquid efficiently.
Become.

[Brief description of drawings]

FIG. 1 is a sectional view showing an embodiment of an ultrasonic fingerprint detecting device of the present invention.

FIG. 2 is a partial perspective view showing the inside of the ultrasonic fingerprint detection apparatus of FIG.

FIG. 3 is a sectional view showing an embodiment of the atomizing device 1 and its periphery.

FIG. 4 is a plan view of a piezoelectric vibrator 7 and a diaphragm 8.

FIG. 5 is a partially enlarged cross-sectional view of the diaphragm 8 taken along a plane perpendicular to the plate surface.

FIG. 6 is a partially enlarged plan view of a diaphragm 8.

FIG. 7 is a configuration diagram showing an embodiment of a drive circuit 5.

8 is a characteristic diagram showing the relationship between the amplitude and frequency of the admittance between the main electrode M and the ground electrode G in the composite of the piezoelectric vibrator 7 and the diaphragm 8. FIG.

9 is a characteristic diagram showing the relationship between the phase and frequency of admittance in FIG.

FIG. 10 is a characteristic diagram showing a relationship between susceptance and conductance in the vicinity of a resonance frequency in a composite body of the piezoelectric vibrator 7 and the diaphragm 8.

FIG. 11: Fingerprints detected on wood free paper.

FIG. 12: Fingerprint detected on thermal paper.

FIG. 13 is a block diagram of a three-terminal system self-exciting circuit.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Atomization device 2 Blower 3 Rotation support tool 4 Sensor 5 Drive circuit 6 Rotating body 7 Piezoelectric vibrator 8 Vibration plate 9 Support tool 10 Liquid retaining material 11 Piezoelectric ceramic 12 Hole P Interdigital electrode Q electrode T _P1 , T _P2 , T _Q terminal L ₁ Boost coil T _r transistor R ₁ , R ₂ resistance D diode

Claims (6)

[Claims] 1. An N number of ultrasonic wave exciters U _i (i = i = i = i = i = _i ), which is formed by fixing a vibration plate having a large number of minute through holes to a piezoelectric vibrator.
1, 2, ..., N) atomizes the solution by the elastic vibration, sprays the mist on the surface of the object, forms a thin film of the substance contained in the mist on the surface, and In an ultrasonic fingerprint detection device for detecting the fingerprint by reacting the contained substance and the substance contained in the fingerprint attached to the surface, the means for forming the thin film on the surface is the film thickness of the thin film. Control means and means for promoting the reaction, the film thickness control means includes means for controlling the particle size of the mist and the amount of the mist, the reaction promoting means for the surface sprayed with the mist. The piezoelectric vibrator includes a piezoelectric ceramic and electrodes P and Q, and the electrodes P and Q are formed on both end surfaces perpendicular to the thickness direction of the piezoelectric ceramic, respectively. , The Pole P comprises a set of interdigital electrodes, the resonance of the piezoelectric vibrator between the terminal T _Q at one terminal T _P1 and the electrode Q of the two terminals T _P1 and T _P2 of the interdigital electrodes A circuit for driving the ultrasonic exciter by applying a voltage having a frequency substantially equal to the frequency is provided, and the drive circuit is for boosting voltage and is connected between the DC power supply and the terminal T _P1 . The drive circuit includes a coil, and a transistor that receives the piezoelectricity appearing at the terminal T _P2 as a feedback voltage by connecting the output voltage terminal to the terminal T _P1 and the input voltage terminal to the terminal T _P2. An oscillation circuit in which the transistor is an amplification element and the ultrasonic exciter is a resonance circuit, and the resonance frequency of the piezoelectric vibrator is approximately equal to the resonance frequency of a composite of the piezoelectric vibrator and the diaphragm. Ultrasonic fingerprint detection apparatus according to claim that no. 2. The piezoelectric vibrator has a dimensional ratio of length to width of 1
Is a rectangular plate close to 1 and not equal to 1 or a rectangular prism having a dimensional ratio of 2 out of 3 sides close to 1 and not equal to 1, wherein the vibrating plate is the electrode of the piezoelectric vibrator. 2. The one-sided end face having P or Q is integrally connected and fixed.
The ultrasonic fingerprint detecting device according to. 3. The solution comprises a ninhydrin solution of about 0.5-5%, wherein the solvent of the ninhydrin solution is acetone,
The ultrasonic fingerprint detecting device according to claim 1 or 2, which is made of n-hexane or another organic solvent or water. 4. The ultrasonic fingerprint detecting apparatus according to claim 1, wherein the object is a newspaper, a thermal paper, a high-quality paper or another paper. 5. The means for supplying the solution to the vibrating plate has a support for supporting the ultrasonic exciter, a liquid storage chamber for storing the solution, and a large number of through holes, which has a large liquid absorption capability. And a liquid retaining material configured to absorb the solution, wherein the support holds the complex in a predetermined position with respect to a fixed object, and at least a portion of the support that contacts the ultrasonic exciter is It is made of expanded polystyrene or other substance having a lower acoustic impedance than a piezoelectric vibrator, and the diaphragm constantly or intermittently contacts the liquid retaining material to atomize the solution absorbed in the liquid retaining material. The ultrasonic fingerprint detecting device according to claim 1, 2, 3 or 4. 6. The ultrasonic fingerprint detecting apparatus according to claim 5, wherein the solution supply unit includes a tube for supplying the solution from the liquid storage chamber to the diaphragm.