JPH0285914A - Detecting device for surface pressure distribution - Google Patents

Abstract

PURPOSE:To detect a minute surface pressure distribution by forming a strain gauge element between the intersecting points of the 1st and 2nd scanning a electrodes consisting of plural electrodes arranged crossing each other and insulated from each other for formation of a matrix and therefore securing the connection between both scanning electrodes. CONSTITUTION:The X-direction scanning electrodes X1, X2... and the Y-direction scanning electrodes Y1, Y2, Y3... are arranged in a matrix via the spacer 103. Then the strain gauge elements 104 are formed with flexion by a vapor deposition process or the combination of the sputtering and etching processes with use of a Cu-Ni alloy material so that the elements 104 are set on the holes 101a of a blanked plate 101 and covers both types of scanning electrodes. The shape of the element 104 is decided so that the ratio between the width and the length (aspect ratio) of the element 104 is increased as much as possible. Thus, the surface pressure distribution applied to a pressure receiving plate is taken out as the electric signals by means of the change of the resistance value due to the flexion of the element 104 serving as the pressure receiving plate. Thus it is possible to detect the minute change of the pressure and a minute pressure distribution.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a surface pressure distribution detection device that detects a minute surface pressure distribution.

(Prior art) Conventionally, the two-dimensional distribution of the load acting on the surface of an object has been measured by arranging a large number of load cells in a matrix, or forming a large number of electrode pairs in a matrix, and scanning these elements. Methods are known to
No. 30), it is used to measure the distribution of load and pressure applied to automobile seats, robot hands, etc.

Since these methods involve relatively large elements such as load cells and electrode pairs, are they suitable for measuring two-dimensional pressure distribution on objects such as those mentioned above? It is not suitable for measuring pressure distribution with a fine density of 4 lines per 1 mm due to unevenness.

Therefore, in Japanese Patent Application No. 62-145030, the present applicant proposed a pressure-sensitive material such as a conductive rubber whose resistance value changes depending on the strength of the pressure, in order to measure a fine surface pressure distribution such as a fingerprint. We have proposed a detection device that uses a sheet to electrically scan and extract changes in resistance due to pressure distribution.

According to this detection device, is it possible to reliably detect a minute surface pressure distribution in combination with a matrix scanning electrode? A certain degree of thickness is required and it is impossible to make the film thinner.Since it is sheet-like, it is difficult to separate the load points because only adjacent loads affect each other, so it is difficult to accurately detect the surface distribution of pressure. The measured pressure may be slightly affected by changes in the sheet over time.
In manufacturing, it is difficult to ensure the uniformity of the pressure-sensitive sheet and it is difficult to obtain the desired characteristics, resulting in problems such as difficulty in detecting minute pressure changes and pressure distribution.

(Objective and Structure of the Invention) The present invention has been made in view of the above points, and it is an object of the present invention to propose a detection device for fine surface pressure distribution that is easy to manufacture, thin, and inexpensive, and in which load points can be easily separated. In order to achieve this purpose, between the intersections of a first scanning electrode and a second scanning electrode, which are composed of a plurality of electrodes that are insulated and arranged so as to cross each other and form a matrix. A strain gauge element is formed so as to be connected between both electrodes, and a pressure receiving plate is constructed so that the strain gauge element can be deflected by an external force, and the resistance value of the pressure receiving plate changes due to the deflection of the strain gauge element. It is configured to take out the surface pressure distribution received by the pressure receiving plate as an electrical signal using the .

(Example) The present invention will be explained below based on the drawings.

In the embodiments shown below, a surface pressure distribution detection device suitable for detecting a fingerprint pattern will be exemplified, but it goes without saying that the present invention is not limited thereto.

FIG. 1 is a block diagram showing the overall configuration of a surface pressure distribution detection device according to the present invention for detecting a fingerprint pattern.

In the figure, l is a fingerprint input board as a pressure receiving plate for inputting fingerprint data by pressing the fingertip, 2 is a controller that commands and operates according to a predetermined processing program stored in ROM 3, and 4 is a fingerprint input board that is read by the fingerprint input board l. A RAM 5 stores fingerprint data, and a contact a1a 2 of the switch SW is connected at the timing of the clock output from the controller 2.
+ a :l +...an are sequentially switched to set the X axis in XI, X2. X:l,...Electronic switch that outputs a scanning signal to Xn, 6 is the last X of electronic switch 5
Y-axis input yl + based on the scanning signal of the input xn
Analog switches sw,, sw,, sw, which sequentially switch Y2+ y3 *・”yn to the contact point.

...Selector 7 having SWo is a power supply circuit that generates a desired voltage. The voltage generated by the power supply circuit 7 is divided by resistors R3 and R2, and a desired voltage v is applied to point A.
1 and this voltage is applied to the non-inverting terminal of buffer 8. The inverting terminal of the buffer 8 is connected to the output terminal.

The selector 6 selects each Y axis yl + y2 + y, 3
．． Each yn has contacts a and b, and the contacts a are connected in common to the output terminal of the buffer 8, and the contacts in common are connected to the inverting terminal of the differential amplifier 9. . A non-inverting terminal of differential amplifier 9 is connected to an output terminal of buffer 8. The inverting terminal of the differential amplifier 9 is connected to the output terminal via a resistor R3.

The output of the differential amplifier 9 is A/D converted by an A/D converter 10, and is converted to a reference voltage V by a comparator 11.
compared with ref. The reference voltages v, , mf are set by a variable resistor R4.

The fingerprint input board l has 0 X-axis lines, x 2° x 3. ”
*+xn and 0 Y-axis in 3'l l y21y31
・" Y n are arranged so that they are orthogonal to each other and insulated, and the Y axis is 3'l * 'jz l 3'3
1...yn are switches SW, SW2 of selector 6
.

SW3...Connected to the common contact of SWn.

Next, an embodiment of the fingerprint input plate l as a pressure receiving plate will be described with reference to FIGS. 2, 3, and 4.

FIG. 2 is a partially exploded perspective view of the fingerprint input board 1, FIG. 3 is an assembled perspective view with a part cut away, and FIG. 4 is an A in FIG. 3.
-A sectional view.

The fingerprint input board 1 has a circular hole 101 formed by etching or the like.
a at a predetermined interval (for example, center-to-center distance of 50 pm), and the diameter of the hole 101a on the back surface (lower surface) is 1. Groove 1oib of Sentence 2 (sentence, >nr) with a slightly larger width than Hole 101
Copper foil pressure relief plates 1 arranged and formed according to the position of a
After filling the hole 101a with a thermally decomposable material such as acrylic polymer or styrene (for example, polyα-methylstyrene), which will eventually be removed, the surface (upper surface) is polished. From then on top of that thickness 5~
A 10 gm elastic base 1t1102 made of a resin such as polyimide is glued.

This base film 102 may be applied by a roller or vapor deposited.

Next, a metal material such as N or AM is deposited on the base film 102 by vapor deposition or sputtering, and then etched to form a Y-axis in'/l+ Yz +y3. The Y-direction scanning electrodes Y,, Yt.

Ya, . . . are formed. This Y direction scanning electrode Y1.
The width of Ya and Ya is approximately 6 pm. After that, spacers 103 are formed with an insulating film such as tantalum pentoxide at the portions that intersect with the X-direction scanning electrodes Xr, X2, X:l, . . . on the scanning electrodes Yr, Yt, Y's, .
is formed by etching. Next, the Y-direction scanning electrode Yl passes through these spacers 103.

X-direction scanning electrodes X t , X z , made of metal materials such as N or An in the direction orthogonal to Yt, Ya...
Form “”. The formation method is Y-axis direction scanning electrode Y1
．． Same as Yt, y, . . ., it is a combination of vapor deposition or sputtering and etching, and the electrode width is about 6 μm.

In this way, the X-direction scanning electrodes Xs, X2, . . . and the Y-direction scanning electrodes Y□'+y,, y, . and,
Hole 101a of pressure release plate 101 straddles the rescanning electrode
Using Cu-N and alloy material on top, the line width is about a.
gm and a length of about 1100p is formed by bending by a combination of vapor deposition or sputtering and machining/nching.

The shape of this strain gauge element 104 is determined so that its width to length ratio (so-called aspect ratio) is as large as possible.

A protective film 105 provided with a large number of pressure concentration protrusions 105a at a distance from the holes 101a of the pressure relief plate 101 is adhered to the upper part of the thus produced fingerprint retention plate assembly. This protective film 105 has a thickness of about 6 gm and is made of an elastic material such as polypropylene.

Finally, the fingerprint input board l thus made is placed in a heating container, and the pyrolyzable material filled in the holes 101a and grooves 101b of the pressure release board 101 is softened and removed using a vacuum suction device. , and then adhered onto the glass substrate 100 to complete the process.

Returning again to FIG. 1, the fingerprint pattern detection procedure and the operation of the device will be explained.

When power supply voltage is supplied to each circuit part of the device, the controller 2 switches the electronic switch 5 and the selector 6 at a timing controlled by a program stored in the ROM 3. That is, the electronic switch 5 sequentially switches the contacts al+a21 and -a of the switch sw at a timing of, for example, lps, and as a result, the X-direction scanning electrodes X+, X2,
A predetermined voltage (for example, 5V) is sequentially applied to xl, . . . xl. On the other hand, the selector 6 also switches analog switches S W = , S Wz , .
Switch the contact of SW from a to b.

Therefore, when the finger F whose fingerprint pattern is to be detected is placed on the fingerprint input board L and pressed lightly, the strain gauge element 104 is pushed and bent by the portion that hits the ridges of the fingerprint pattern. There is a pressure relief plate l directly below the strain gauge element 104.
Since the hole 101a drilled in the ot is located, the strain gauge element 104 is easy to bend, and when it bends, the air in the hole 101a is pushed out and passes through the groove 101b formed on the back side of the pressure relief plate 101, allowing fingerprint input. The deflection of the strain gauge element 104 is not hindered in any way because it escapes to the side surface of the plate l.

When the strain gauge element 104 is bent, its inherent resistance value increases. Therefore, the electronic switch 5 sequentially applies the above-mentioned voltages to the X-direction scanning electrodes X L I X t , X Y , . In Figure 1, electronic switch 5
) selector 6 whose contact a2 is connected to the power supply circuit 7
Switch SW.

SW2. . . . When the contacts of SW, , are sequentially switched from a to b (in FIG. 1, the switch SW2 contact is switched and the Y-direction scanning electrode y2 is connected to the contact).
Strain gauge element 10 at each point on the fingerprint input board l
The resistance values of 4 are sequentially input to the inverting terminal of the differential amplifier 9.

The non-inverting terminal of the buffer 8 has a connection point A between resistors R1 and R2.
, and this potential v1 is also applied to the non-inverting terminal of the differential amplifier 9 and the contacts a of all the switches of the selector 6. Therefore, the area M surrounded by the broken line circle in FIG. The fingerprint data indicates that the current flowing through the Y-direction scanning electrode (Y2 in FIG. 1) connected to the contact point of the n switches constituting the selector 6 decreases due to an increase in resistance due to the deflection of the strain gauge element 104. However, due to the feedback effect of the resistor R3, the output voltage of the differential amplifier 9 appears to increase by the amount of the decrease in current. In this way, only one switch of the selector 6 is connected to contact a, and all other switches are connected to contact a, so
Only the fingerprint pattern data of one point to be measured is extracted, and the selector 6 excludes the fingerprint data of other points that are extracted to the Y-direction scanning electrode via other X-direction scanning electrodes and strain gauge elements. will be done.

The fingerprint data at each point taken out to the output terminal of the differential amplifier 9 is an analog signal that depends on the resistance value of the strain gauge element 104. This analog fingerprint data is A/D
The data is digitized by the converter 10 and taken out as, for example, 8-bit digital fingerprint data from the output terminal OI, and is compared with a threshold value V r e f set by the variable resistor R4 in the comparator 11 to determine the peaks and valleys of the fingerprint. The fingerprint pattern signal is extracted from the output terminal 02 as a fingerprint pattern signal. The fingerprint data and fingerprint pattern signals from these output terminals 0 and 02 are processed depending on the subsequent use and used for displaying or registering the fingerprint pattern or for comparison with already registered fingerprint patterns.

FIG. 5 is a perspective view partially showing only a fingerprint input plate as a pressure receiving plate of another embodiment of the surface pressure distribution detection device according to the present invention, which is also suitable for detecting a fingerprint pattern. In the figures, the same reference numerals as in FIG. 3 indicate the same components.

The manufacturing method of the fingerprint input plate l of this embodiment is different from the embodiment shown in FIG. Scanning electrodes Xs, X2.

. . . Apply a thermally decomposable substance to a thickness of about 204 m uniformly over the front surface using a roller or the like, and then vapor-deposit an approximately square metal mask on the coating film at a position corresponding to the hole 101a of the pressure relief plate 101. Formed by etching. The position of this mask is exactly within a square area surrounded by two X-direction scanning electrodes and two Y-direction scanning electrodes.

Next, the thermally decomposable substance in areas other than the metal mask is removed by etching, and then the metal mask is also removed. As a result, a pedestal 106 of the thermally decomposable material is formed at the position of the metal mask as shown in FIG. Next, strain gauge elements 104 are bent and formed on this base 106 in the same manner as in the previous embodiment, and one end of each strain gauge element 104 is
The electrode is electrodeposited on the direction scanning electrode, and the other end is electrodeposited on the Y direction scanning electrode. Since the surface of this platform 106 is located at a higher position than the base film 102, the strain gauge element 104 is approximately 10 to 20 gm higher than the X-direction scanning electrode and the Y-direction scanning electrode.
gm is formed at a high position.

After the strain gauge element 104 is thus formed, a protective film 105' having a thickness of several gm is applied to the front surface as in the previous embodiment. Unlike the protective film 105 of the previous embodiment, this protective film 105' does not require a protrusion such as the pressure concentration protrusion 105a, because the pedestal part 106 is formed higher than the base film 102. Protected with [105
This is because, as shown by the reference numeral in FIG. 5, it rises high upwards and has a shape similar to the pressure concentration protrusion 105a of the previous embodiment, and performs the same function.

Finally, the entire fingerprint input board assembly made in this way is placed in a heating container, and the holes 101a and grooves 101 of the pressure relief plate 101 are
The thermally decomposable material packed in b and the thermally decomposable material constituting the platform 106 are softened and removed using a vacuum suction device. As a result, the strain gauge element 104
It is attached and held on the back side of 5'.

The structure of this embodiment other than the fingerprint input board is completely the same as the embodiment shown in FIG. 1, and therefore the explanation of the structure and circuit operation will be omitted.

In either of the above two embodiments, the pressure increment that occurs when detecting a fingerprint pattern is released through a groove provided on the back side of the pressure relief plate, or the pressure relief structure of the pressure relief plate has a pressure relief structure as shown in FIG. A protrusion 1 is provided at a position corresponding to the intersection of the X-direction scanning electrode and the Y-direction scanning electrode on the punched plate 101.
01C may be formed. If you do this, the four 1
The area surrounded by 01c corresponds to the hole 101a of the pressure relief plate 101 used in the above-mentioned embodiment, and the area between the protrusions 101c becomes the pressure relief passage, so the structure is simpler than that of the previous embodiment. You can get a pressure relief effect.

In the above embodiment, an example was shown in which the surface pressure distribution measuring device according to the present invention was used to detect a fingerprint pattern as a preferred application example, but the present invention is not limited thereto. Needless to say, it is also suitable for other application fields such as measurement.

(Effects of the Invention) As explained above, in the present invention, the first scanning electrode and the second scanning electrode are composed of a plurality of electrodes that are insulated and arranged so as to cross each other to form a matrix. A strain gauge element was formed to be connected between both electrodes at the intersection with the electrode, and the pressure receiving plate was configured so that the strain gauge element could be deflected by an external force, so that a load with a pressure distribution could be applied from the outside. A fine surface pressure distribution can be detected by applying the first scanning electrode and the second scanning electrode to the pressure receiving plate and scanning them in a predetermined order.

By using a strain gauge as a pressure-sensitive element, there is no restriction on the thickness of the element, it is possible to eliminate the influence of aging on the measured pressure, and it is possible to separate the load points.
It becomes possible to detect surface pressure distribution in a thin and inexpensive manner.

Furthermore, if a space for actively amplifying the deflection of the element due to an external load is provided at the position of the strain gauge element, or a structure such as an air escape that does not impede the deflection, the sensitivity of pressure detection can be improved.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing the overall configuration of a surface pressure distribution detection device according to the present invention, and FIG. 2 is a partial exploded view of an embodiment of a fingerprint input board when the surface pressure distribution detection device is used to detect a fingerprint pattern. FIG. 3 is an assembled perspective view with a part of the fingerprint input board cut away, FIG. 4 is a sectional view taken along line A-A in FIG. 3, and FIG. 5 is an example of another embodiment of the fingerprint input board. FIG. 6 is a partial perspective view showing a state in which the fingerprint input board shown in FIG. 5 is being manufactured, and FIG. 7 is a perspective view of another example of the pressure release plate. l... Fingerprint input board (pressure receiving board), 2... Controller, 5... Electronic switch, 6... Selector, 8...
Buffer, 9...Differential amplifier, lO.-A/D converter, 100...Glass substrate, 101...Pressure plate, 102...Base film, 103...Spacer, 10
4... Strain gauge element, 105... Protective film, 1
06... Taibe Patent Applicant Enix Co., Ltd. Agent Patent Attorney Hiroo Suzuki 1st

Claims (6)

[Claims] (1) Between a plurality of first and second scanning electrodes that are insulated and arranged so as to intersect at predetermined minute intervals to form a matrix, and the intersection of the first and second scanning electrodes. a pressure receiving plate having a strain gauge element connected between both electrodes and formed to be deflectable by an external force; and a scanning signal is applied to the first and second scanning electrodes in a predetermined order. and output means for sequentially extracting changes in the resistance value of the strain gauge element, which is deflected in response to surface pressure applied to the pressure receiving plate from the outside, as an electric signal at each intersection using a scanning signal from the scanning circuit. A surface pressure distribution detection device comprising: (2) The surface pressure distribution detection device according to claim 1, wherein the pressure receiving plate has a space below the strain gauge element. (3) The surface pressure distribution detection device according to claim 2, wherein the space communicates with the atmosphere. (4) The surface pressure distribution detection device according to claim 1, 2 or 3, wherein the pressure receiving plate has a surface pressure concentration protrusion above the strain gauge element. (5) The surface pressure distribution detection device according to claim 1, wherein the strain gauge element of the pressure receiving plate is formed in a diaphragm shape on the pressure side of the first and second scanning electrode forming surfaces. (6) The surface pressure distribution detection device according to claim 1, wherein the strain gauge element has a large aspect ratio.