JP2004199487A - Image input device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image input device which surely reads an image with sharpness. <P>SOLUTION: A plurality of DG-Tr 20 are arranged in a matrix under the surface 32a of an image reading circuit 2. A pressure sensor 50 for detecting a pressure applied to the surface is arranged adjacently to the image reading circuit 2 so that the surface of the pressure sensor 50 is flushed with the surface 32a of the circuit 2. A detection signal showing the level of the pressure detected by the pressure sensor 50 is outputted to a comparison circuit 62. The comparison circuit 62 compares the level of the detection signal with a threshold, and outputs a trigger signal to a driving circuit 10, when the level of the detection signal exceeds the threshold, and the circuit 2 is driven by the driving circuit 10. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an image input device that includes an image reading circuit disposed below a mounting surface on which a subject is placed, and that inputs an image of the subject by reading the subject with an image reading device.
[0002]
[Prior art]
A fingerprint is a very useful means for performing personal authentication because it has a pattern peculiar to an individual. In recent years, fingerprint authentication devices that apply fingerprints to personal authentication have been developed. Specifically, the fingerprint authentication device performs personal authentication by comparing a fingerprint image read by an image reading device with fingerprint image data of a registrant registered in advance, and includes a PC (Personal Computer) and a PDA (Personal Computer). It is being considered to be installed in information devices such as Personal Digital Assistance and mobile phones.
[0003]
Patent Document 1 describes a two-dimensional image reading device used for a fingerprint authentication device. The two-dimensional image reading device includes a photosensor array in which a plurality of photosensors are arranged on a transparent substrate, a backlight arranged on the back side of the photosensor array so as to face the backside of the photosensor array, It includes a transparent electrode layer covering the surface of the sensor array, and a detection unit for detecting a change in voltage of the electrode layer. Explaining the operation and the method of use of the conventional two-dimensional reading device, the subject itself has a specific resistance and capacitance, so when the subject places a finger on the electrode layer, the finger is in contact with the electrode layer. Is detected by the detection unit, the backlight is turned on by the finger detection by the detection unit to irradiate the finger, and the photo sensor array performs an image reading operation to read the finger image by the finger detection by the detection unit. . The image of the finger read by the photosensor array is a fingerprint image represented by the intensity distribution of light reflected by the unevenness of the finger on the contact surface.
[0004]
[Patent Document 1]
JP-A-2002-94040 (pages 4-9, FIGS. 6, 14)
[0005]
[Problems to be solved by the invention]
By the way, the state of sweating of the finger differs from person to person, and the force with which the finger presses the electrode layer when the finger is placed on the electrode layer also differs from person to person. If the finger's sweating state is different, the specific voltage change due to the finger touching the electrode layer is also different, and if the pressing force on the electrode layer is different, the contact area between the finger and the electrode layer is different and the voltage change of the electrode layer is also different . Therefore, in the conventional two-dimensional image reading apparatus, if the permissible amount of the variation due to the individual difference in the sweating state or the variation in the force of pressing with the finger is too narrow, a certain person places the finger on the electrode layer, and Even if a person's finger is detected by the detection unit and the fingerprint image can be read, or if another person places the finger on the electrode layer, the detection unit does not detect the other person's finger by the detection unit May not be able to read the fingerprint image of the other person. Even in the same individual, the sweating state and the pressing force of the finger are different depending on the case, and the fingerprint image of the finger may not be read. In addition, if the allowable amount is widened, there is a possibility that an object other than the finger is erroneously recognized. Further, it is difficult to detect such a small voltage change with high accuracy due to noise such as ambient electromagnetic waves.
[0006]
In addition, if the pressing force on the electrode layer is weak, the convex portion of the finger does not come in close contact with the electrode layer, so that there is no difference in the intensity of the reflected light between the convex portion and the concave portion of the finger, and a clear fingerprint image cannot be read. is there.
[0007]
Therefore, an object of the present invention is to provide an image input device capable of easily and surely reading an image and reading a clear image.
[0008]
[Means for Solving the Problems]
In order to solve the above problems, the image input device according to the first aspect of the present invention, as shown in FIGS.
An image reading circuit (for example, the image reading circuit 2) disposed below a mounting surface (for example, the surface 32a of the image reading circuit 2, the surface of the pressure sensor 50) on which the subject (for example, the finger 100) is mounted; ,
Detecting means (for example, a pressure sensor 50, a comparison circuit 62) for detecting that the subject is mounted on the mounting surface by the pressure applied to the mounting surface,
It is characterized by having.
[0009]
According to the first aspect of the present invention, when the subject is placed on the placement surface, pressure is applied from the subject to the placement surface, and the detection means detects the subject by the pressure applied to the placement surface. Detection, the reading operation of the image reading circuit can be stopped when the subject is not placed on the placement surface, and the image reading circuit can be quickly stopped when the subject is placed on the placement surface. Since the reading operation can be stopped, power consumption when the subject is not placed on the placing surface can be suppressed, and there is no need to perform a special operation other than placing a finger to perform the reading operation. Therefore, the image of the subject can be reliably read only by placing the subject on the mounting surface.
In addition, when a finger is applied as the subject, conventionally, there has been a case where the placement of the finger cannot be detected due to the state of sweating of the finger, etc. When placed on the placement surface, pressure is applied to the placement surface, so that the placement of the finger can be reliably detected by the detection means, and the image of the finger can be reliably read.
[0010]
According to a third aspect of the present invention, as shown in FIG. 5, in the image input device according to the first aspect,
The detecting means,
A pressure sensor (for example, a pressure sensor 50) for detecting a pressure applied to the placement surface,
A trigger for comparing the pressure level detected by the pressure sensor with a threshold for partitioning between a mounted state and an unmounted state, and, when the threshold is exceeded, causing the image reading circuit to perform an image reading operation. A comparison means (for example, a comparison circuit 62) for outputting a signal.
[0011]
When the subject is placed on the placement surface, pressure is applied from the subject to the placement surface, but when the pressure applied from the subject to the placement surface is small, the The contact area becomes small, and even if the image is read by the image reading circuit, a clear image cannot be read. However, according to the third aspect of the present invention, if the level of the detection signal indicating the pressure applied from the subject to the mounting surface does not exceed the threshold, the image reading circuit does not output the trigger signal and the image reading circuit reads the image. Since no operation is performed, such unclear image is not read. When the level of the detection signal indicating the pressure applied from the subject to the mounting surface exceeds the threshold value, the comparing means outputs a trigger signal and the image reading circuit performs an image reading operation. Since the image is read by the image reading circuit when the contact area with the surface is large, a clear image can be read reliably.
According to a fifth aspect of the present invention, in the image input device according to the first aspect,
The image processing apparatus further includes an adjustment unit (for example, an adjustment circuit 102) that adjusts the brightness of a light source that irradiates the subject with light in accordance with the pressure applied to the placement surface by the subject.
[0012]
According to the fifth aspect of the present invention, since the light irradiation intensity of the light source is adjusted based on the pressure of the subject on the mounting surface, light having an intensity suitable for the contact area between the subject and the mounting surface is received. It is incident on the specimen. Therefore, the image of the subject can be clearly read regardless of the contact pressure of the subject.
[0013]
The image input device according to the ninth aspect of the present invention, as shown in FIGS.
An image reading circuit (for example, the image reading circuit 2) disposed below a mounting surface on which a subject (for example, a finger 100) is mounted;
Detecting means (for example, a pressure sensor 50 and a comparison circuit 62) which is arranged below the image reading circuit and detects that the subject is mounted on the mounting surface by the pressure applied to the mounting surface. When,
It is characterized by having.
[0014]
According to the ninth aspect of the present invention, the detecting means for detecting the placement of the subject can stop the reading operation of the image reading circuit when the subject is not placed on the placement surface, and the placement of the subject can be stopped. When placed on a surface, the reading operation of the image reading circuit can be stopped quickly, and since the detecting means is arranged below the image reading circuit, the image input device can be reduced in size, and particularly excellent in portability. This is particularly effective for an authentication device of a device that has been used.
[0015]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, specific embodiments of the present invention will be described with reference to the drawings. However, the scope of the invention is not limited to the illustrated example.
[0016]
[First embodiment]
FIG. 1 is a plan view showing a fingerprint reader 1 to which the image input device of the present invention is applied. FIGS. 2A and 2B show a state where a finger is not placed and a finger, respectively. FIG. 2 is a cross-sectional view showing a state in which is mounted along a broken line BB in FIG. 1. FIG. 3 is a cross-sectional view taken along the line CC of FIG.
[0017]
The fingerprint reader 1 reads the fingerprint image of the finger 100 by converting the amount and intensity of the reflected light of the finger 100 placed on the front surface 32a into an electric signal, and a solid-state imaging device as an optical sensor and its driver. Are integrated, a driving circuit 10 for acquiring a fingerprint image of the finger 100 by detecting an electric signal from the image reading circuit 2, and a finger placed on the surface 32a of the image reading circuit 2. A light irradiating unit that irradiates light toward the image reading circuit 100; a film-type pressure sensor 50 that detects pressure generated when the finger 100 contacts the surface 32a of the image reading circuit 2; A finger holding unit 16 for holding the finger at a predetermined position in the sensor 50.
[0018]
First, the light irradiation means will be described. The light irradiation unit guides the light emitted from the light source 14 to the image reading circuit 2 and irradiates the light to the finger 100 as the subject through the image reading circuit 2. And a light guide plate 15. The light guide plate 15 has a substantially flat plate shape, and is covered with a light reflecting material except for a side surface facing the light source 14 and a surface facing the back surface of the image reading circuit 2. Light from the light source 14 is diffused in the light guide plate 15, and light radiated from the surface of the light guide plate 15 is uniformly applied to the back surface of the image reading circuit 2. Note that, instead of the light guide plate 15 and the light source 14, a surface light emitting element such as an organic EL element may be provided so as to face the back surface of the image reading circuit 2.
[0019]
Next, the image reading circuit 2 will be described with reference to FIGS. 4A is a plan view showing one pixel of the image reading circuit 2, and FIG. 4B is a cross-sectional view taken along a line AA in FIG. 4A. .
[0020]
The image reading circuit 2 has a substantially flat transparent substrate 17 and a plurality of double-gate transparent substrates 17 arranged on one surface of the transparent substrate 17 in a matrix of n rows and m columns (both n and m are integers). A transistor (hereinafter, referred to as DG-Tr) 20, 20,... And a top gate driver 11, which is formed on a transparent substrate 17 around the image input area 8 in which the DG-Tr 20, 20,. A protective insulating film 31 covering the bottom gate driver 12 and the drain driver 13, the drivers 11, 12, 13 and the DG-Trs 20, 20,..., A discharge conductive film 32 formed on the protective insulating film 31, Is provided.
[0021]
The transparent substrate 17 has a light transmitting property (hereinafter, simply referred to as a light transmitting property) and an insulating property, and is a glass substrate such as quartz glass or a plastic substrate such as polycarbonate. The transparent substrate 17 forms the back surface of the image reading circuit 2, and the light guide plate 15 faces the transparent substrate 17.
[0022]
Each DG-Tr 20 is a photoelectric conversion element serving as a pixel. Each of the DG-Trs 20 includes a bottom gate electrode 21 formed on the transparent substrate 17, an interlayer insulating film 22 formed on the bottom gate electrode 21, a bottom gate electrode 21 and the interlayer insulating film 22 interposed therebetween, and A semiconductor film 23 facing the electrode 21, a channel protective film 24 formed on the center of the semiconductor film 23, and impurity semiconductor films 25 and 26 formed on both ends of the semiconductor film 23 so as to be separated from each other; A source electrode 27 formed on the impurity semiconductor film 25; a drain electrode 28 formed on the impurity semiconductor film 26; an interlayer insulating film 29 formed on the source electrode 27 and the drain electrode 28; A top gate electrode 30 sandwiching the interlayer insulating film 29 and the channel protection film 24 and facing the semiconductor film 23.
[0023]
On the transparent substrate 17, the bottom gate electrodes 21 are formed in a matrix for each DG-Tr 20. Also, n bottom gate lines 41, 41,... Extending in the horizontal direction are formed on the transparent substrate 17, and the bottom gate electrodes 21 of the DG-Trs 20 in the same row arranged in the horizontal direction are It is formed integrally with the common bottom gate line 41. The bottom gate electrode 21 and the bottom gate line 41 have conductivity and light shielding properties, and are made of, for example, chromium, a chromium alloy, aluminum, an aluminum alloy, or an alloy thereof.
[0024]
An interlayer insulating film 22 common to all the DG-Trs 20, 20,... Is formed on the bottom gate electrode 21 and the bottom gate line 41. The interlayer insulating film 22 has an insulating property and a light transmitting property, and is made of, for example, silicon nitride or silicon oxide.
[0025]
A semiconductor film 23 is formed for each DG-Tr 20 on the interlayer insulating film 22. The semiconductor film 23 has a substantially rectangular shape in plan view, and is a layer formed of amorphous silicon or polysilicon. On the semiconductor film 23, a channel protection film 24 is formed. The channel protective film 24 has a function of protecting the interface of the semiconductor film 23 from an etchant used for patterning, has insulating properties and translucency, and is made of, for example, silicon nitride or silicon oxide. When light is incident on the semiconductor film 23, electron-hole pairs in an amount corresponding to the amount of incident light are generated around the interface between the channel protective film 24 and the semiconductor film 23. In this case, holes are generated as carriers on the semiconductor film 23 side, and electrons are generated on the channel protection film 24 side.
[0026]
On one end of the semiconductor film 23, an impurity semiconductor film 25 is formed so as to partially overlap the channel protective film 24, and on the other end of the semiconductor film 23, an impurity semiconductor film 26 is partially formed on the channel protection film. It is formed so as to overlap with the protective film 24. The impurity semiconductor films 25 and 26 are patterned for each DG-Tr 20. The impurity semiconductor films 25 and 26 are made of amorphous silicon (n) containing n-type impurity ions. ⁺ Silicon).
[0027]
On the impurity semiconductor film 25, a source electrode 27 patterned for each DG-Tr 20 is formed. A drain electrode 28 patterned for each DG-Tr 20 is formed on the impurity semiconductor film 26. Also, m source lines 42, 42, ... and drain lines 43, 43, ... extending in the vertical direction are formed on the interlayer insulating film 22, and each of the DG-s in the same column arranged in the vertical direction. The source electrode 27 of the Tr 20 is formed integrally with the common source line 42, and the drain electrode 28 of each DG-Tr 20 in the same column arranged in the vertical direction is formed integrally with the common drain line 43. The source electrode 27, the drain electrode 28, the source line 42, and the drain line 43 have conductivity and light-shielding properties, and are made of, for example, chromium, a chromium alloy, aluminum, an aluminum alloy, or an alloy thereof.
[0028]
, All the DG-Trs 20, 20,..., On the channel protective film 24, the source electrode 27, the drain electrode 28, and the source lines 42, 42,. Are formed in common with each other. The interlayer insulating film 29 has an insulating property and a light transmitting property, and is made of, for example, silicon nitride or silicon oxide.
[0029]
On the interlayer insulating film 29, a top gate electrode 30 patterned for each DG-Tr 20 is formed. Further, n top gate lines 44 extending in the horizontal direction are formed on the interlayer insulating film 29, and the top gate electrodes 30 of the DG-Trs 20 in the same row arranged in the horizontal direction share a common top. It is formed integrally with the gate line 44. The top gate electrode 30 and the top gate line 44 are conductors having conductivity and translucency. For example, indium oxide, zinc oxide, tin oxide, or a mixture containing at least one of them (for example, tin) It is formed of doped indium oxide (ITO) and zinc-doped indium oxide).
The DG-Tr 20 configured as described above is a photoelectric conversion element using the semiconductor film 23 as a light receiving unit.
[0030]
A common protective insulating film 31 is formed on the top gate electrodes 30 and the top gate lines 44, 44,... Of all the DG-Trs 20, 20,. ing. The protective insulating film 31 has an insulating property and a light transmitting property, and is made of silicon nitride or silicon oxide.
[0031]
On the protective insulating film 31, a discharge conductive film 32 is formed all over. The discharge conductive film 32 has conductivity and translucency, and is formed of, for example, indium oxide, zinc oxide, tin oxide, or a mixture containing at least one of them (for example, tin-doped indium oxide (ITO), zinc, or the like). (Doped indium oxide). The discharge conductive film 32 is grounded and kept at 0 [V], and prevents the DG-Trs 20, 20,. The surface 32a of the discharge conductive film 32 forms the surface of the image reading circuit 2 and is a mounting surface on which the finger 100 is mounted.
[0032]
In the image reading circuit 2 described above, light incident on the transparent substrate 17 from the light guide plate 15 is shielded by the bottom gate electrode 21 so that it does not directly enter the semiconductor film 23. Since the bottom gate electrode 21 is not formed between the DG-Trs 20, 20,..., Light incident on the transparent substrate 17 from the light guide plate 15 passes through the DG-Trs 20, 20,. The light is emitted from the surface of the circuit 2 to the outside.
[0033]
The driver of the image reading circuit 2 will be described. As shown in FIG. 1, the source lines 42, 42,... Are kept at a constant voltage, for example, grounded and kept at 0 [V]. The bottom gate lines 41, 41,... Are connected to the output of the bottom gate driver 12. The top gate lines 44 are connected to the output of the top gate driver 11.
[0034]
The top gate driver 11 is a shift register, and is reset in order from the top gate line 44 in the first row to the top gate line 44 in the n-th row (when the n-th row is reached, the control returns to the first row as necessary). It outputs a pulse. When a reset pulse is output to a certain top gate line 44, the top gate line 44 becomes a high-level reset potential for removing holes accumulated in the semiconductor film 23 and the channel protection film 24, and the reset pulse is reset. When a pulse is not output to a certain top gate line 44, the top gate line 44 and the top gate electrode 30 connected to the top gate line 44 are connected to the positive electrode out of the electron-hole pairs generated by light incident on the semiconductor film 23. The carrier accumulation potential at a low level such that the holes are held.
[0035]
The bottom gate driver 12 is a shift register, and has a high level in the order from the bottom gate line 41 in the first row to the bottom gate line 41 in the n-th row (when necessary, return to the first row when reaching the n-th row). Is output. When a read pulse is output to a certain bottom gate line 41, the bottom gate line 41 and the bottom gate electrode 21 connected to the bottom gate line 41 have a read potential such that a channel is formed in the semiconductor film 23, and the channel region Depends on the amount of light incident on the semiconductor film 23.
[0036]
After the top gate driver 11 outputs a reset pulse to the top gate line 44 of the i-th row (i is an integer of 1 to n), the bottom gate driver 12 reads the bottom gate line 41 of the i-th row. The top gate driver 11 and the bottom gate driver 12 shift output signals so as to output pulses.
[0037]
The drain driver 13 outputs a precharge pulse of a predetermined level (high level) to all drain lines 43, 43,... Between the output of the reset pulse and the output of the read pulse. I have. Further, the drain driver 13 amplifies the voltages of the drain lines 43, 43,... After outputting the precharge pulse, and outputs the amplified voltage to the drive circuit 10.
[0038]
Next, the drive circuit 10 will be described.
The drive circuit 10 appropriately outputs a read pulse to the bottom gate driver 12 by outputting a control signal Bcnt to the bottom gate driver 12, and appropriately resets the top gate driver 11 by outputting the control signal Tcnt to the top gate driver 11. By outputting a pulse and outputting a control signal Dcnt to the drain driver 13, the drain driver 13 outputs a precharge pulse as appropriate. Further, the drive circuit 10 detects the voltage of the drain lines 43, 43,... After a lapse of a predetermined time from the output of the read pulse, or detects the voltage of the drain lines 43, 43,. The fingerprint image of the finger 100 is obtained by detecting the time until the voltage reaches the predetermined threshold voltage.
[0039]
Next, the pressure sensor 50 will be described.
As shown in FIG. 2A, the pressure sensor 50 includes a plurality of electrode lines 51, 51,... Formed on the transparent substrate 17 and extending in the row direction in parallel with each other. , 51,... And a plurality of electrode lines 52, 52,... Extending in the column direction parallel to each other and formed on the back surface. , And a seal 54 covering the periphery of the sheet material 55 and joining the transparent substrate 17 and the sheet material 55. The plurality of electrode wires 52, 52,. Are attached to the sheet material 55 and the transparent substrate 17 so that the electrode wires 52 are orthogonal to the electrode wires 51 in plan view and the electrode wires 51 and 52 are opposed to each other. It has a combined configuration. The spacers 53, 53,... May be arranged so as to be provided between the plurality of electrode wires 52, 52,. Also, after the pressure sensor 50 is repeatedly pressed with the finger, if there is a sufficient restoring force enough to separate the plurality of electrode wires 51, 51,... And the plurality of electrode wires 52, 52,. The spacer 53 is not always required.
[0040]
A voltage is output from at least one of the electrode line 51 and the electrode line 52 of the pressure sensor 50 from a detection driving circuit 61 described later, and as shown in FIG. When the sheet material 55 is placed on the sensor 50, the sheet material 55 is bent by the pressing force of the finger, and the electrode wire 52 is bent and comes into contact with the electrode wire 51. At this time, since the electrode lines 51 and 52 conduct, the current flowing through the electrode lines 51 and 52 and the electrical characteristics such as the voltage and resistance of at least one of the electrode lines 51 and 52 change. . The change in the electrical characteristics is read by the detection drive circuit 61 to determine that the finger is placed, and the reading operation of the image reading circuit 2 is started.
[0041]
The pressure sensor 50 may have a pressure-sensitive ink layer on at least one surface of the electrode wires 51 and 52. In this case, the pressure-sensitive ink layer is arranged so as to overlap the electrode line 51 at the intersection with the electrode line 52. The electric resistance between the electrode wire 51 and the electrode wire 52 depends on the pressure applied to the pressure-sensitive ink layer, and has a characteristic that when the magnitude of the pressure changes, the electric resistance and the like change. The pressure sensor 50 can detect the pressure at the intersection between the electrode wire 51 and the electrode wire 52 based on the electrical resistance or the like at the intersection. Moreover, since the intersections of the pressure sensor 50 are arranged in a matrix when viewed in a plan view, the detection drive circuit 61 measures a change in the electrical characteristic of the electrode line 51 or the electrode line 52 at each intersection. Thus, the pressure distribution in the plane can be detected, and the pressure in the entire plane can be detected.
[0042]
As shown in FIG. 1, the pressure sensor 50 and the image reading circuit 2 are arranged at different positions in plan view (as viewed toward the surface 32a of the image reading circuit 2). In detail, the pressure sensor 50 is arranged so as to be adjacent to the image reading circuit 2, the surface of the pressure sensor 50 is flush with the surface 32a of the image reading circuit 2, and the surface of the pressure sensor 50 is This is a placement surface on which the fingertip 100 is placed.
[0043]
Next, the finger holding unit 16 will be described.
The finger holding portion 16 is formed with a finger-shaped opening 16a from the tip of the finger to the second joint of the finger, and the image input area 8 in which the DG-Trs 20, 20,... The finger holding unit 16 is attached to the surface 32a of the image reading circuit 2 and the surface of the pressure sensor 50 such that the pressure detection region in which the intersections of the electrode lines 52 and the electrode lines 52 are arranged is exposed to the opening. The opening of the finger holding unit 16 corresponding to the terminal segment of the finger is arranged in the image input area 8.
[0044]
Next, a circuit configuration of the fingerprint reader 1 will be described with reference to FIG.
As shown in FIG. 5, in addition to the image reading circuit 2, the driving circuit 10, and the pressure sensor 50, the fingerprint reading device 1 includes a detection driving circuit 61, a comparing circuit 62, a CPU 63, a RAM 64, a ROM 65, A storage unit 66.
[0045]
The detection drive circuit 61 drives the pressure sensor 50 and inputs a change in the electrical characteristics of a signal output to at least one of the electrode lines 51 and 52 of the pressure sensor 50, and the surface detected by the pressure sensor 50 is input. The detection signal indicating the pressure level of the whole of the inside is output to the comparison circuit 62. The detection drive circuit 61 outputs pressure distribution data representing the pressure distribution detected by the pressure sensor 50 to the CPU 63.
[0046]
The comparison circuit 62 receives the detection signal from the detection drive circuit 61, compares the detection signal level with a threshold value for partitioning between the finger placement state and the finger non-placement state, and the detection signal level exceeds the threshold value. In such a case, a trigger signal is output to the drive circuit 10 when the trigger signal is output.
The detecting means for detecting that the finger 100 is placed on the surface 32a of the image reading circuit 2 by the pressure applied to the surface of the pressure sensor 50 includes the above-described pressure sensor 50, the detection driving circuit 61, and the comparison circuit. 62.
[0047]
When a trigger signal is input from the comparison circuit 62, the drive circuit 10 first outputs a signal for causing the light source 14 to emit light, and causes the light source 14 to emit light. Further, the drive circuit 10 outputs a control signal Bcnt to the bottom gate driver 12, outputs a control signal Tcnt to the top gate driver 11, and outputs a control signal group Dcnt to the drain driver 13 after the light source 14 emits light. Has become. Thus, the image reading circuit 2 starts operating. When the image reading circuit 2 operates, a fingerprint image of the finger 100 is acquired by the driving circuit 10, and the data of the fingerprint image is output to the CPU 63.
[0048]
The storage unit 66 stores the registered fingerprint image data of the last segment of the finger for each registrant. The storage unit 66 has a data storage area storing various data in addition to the area storing the registered fingerprint image data, and the data storage area includes a specific area and a normal area. The registered image data may be data representing the relative positions of a plurality of feature points extracted from the fingerprint, or may be the image itself.
[0049]
The ROM 65 stores programs executable by the CPU 63. The CPU 63 uses the RAM 64 as a work area, inputs fingerprint image data from the drive circuit 10, inputs pressure distribution data from the detection drive circuit 61, and uses the input pressure distribution data according to the program stored in the ROM 65. It is determined whether or not the object placed on the surface of the sensor 50 can be regarded as the middle segment of the finger, or if the object placed on the surface of the pressure sensor 50 can be regarded as the middle segment of the finger, the driving circuit 10 Is compared with the registered fingerprint image data stored in the storage unit 66 to determine whether or not the fingerprint image data can be regarded as matching the registered fingerprint image data. Further, the CPU 63 starts the secret mode when it is determined that the fingerprint image data matches the registered fingerprint image data, and starts the normal mode when it determines that the fingerprint image data does not match the registered fingerprint image data. It has become.
[0050]
The operation and usage of the fingerprint reading device 1 according to the present embodiment will be described.
When nothing is in contact with the surface of the pressure sensor 50, since the level of the detection signal representing the entire pressure in the surface detected by the pressure sensor 50 is equal to or less than the threshold value, the trigger signal is sent from the comparison circuit 62 to the drive circuit 10. No output.
[0051]
On the other hand, when the subject places the last segment of the finger 100 on the surface 32 a of the discharge conductive film 32 and places the middle segment of the finger 100 on the surface of the pressure sensor 50, the light source 14 emits light and the light guide plate 15 emits light. The reflected light is incident on the finger 100 via the image reading circuit 2, and the reflected light reflected by the finger 100 is incident on the semiconductor film 23 of the DG-Trs 20, 20,. The in-plane intensity distribution of the reflected light incident on the semiconductor film 23 of the DG-Trs 20, 20,... Depends on the unevenness of the finger 100, and the reflected light reflected by the convex part of the finger 100 close to the surface 32a is high. Although the light is incident on the semiconductor film 23 with high intensity, the reflected light reflected on the concave portion of the finger 100 away from the surface 32a is incident on the semiconductor film 23 with low intensity due to irregular reflection or the like, or hardly incident on the semiconductor film 23.
[0052]
Here, since the middle segment of the finger 100 is placed on the pressure sensor 50, pressure is applied from the finger 100 to the pressure sensor 50, and a detection signal representing the entire pressure in the plane detected by the pressure sensor 50 is generated. Level exceeds threshold. Therefore, a trigger signal is output from the comparison circuit 62 to the drive circuit 10.
[0053]
The drive circuit 10 that has received the trigger signal from the comparison circuit 62 outputs a control signal Bcnt to the bottom gate driver 12, outputs a control signal Tcnt to the top gate driver 11, and outputs a control signal Dcnt to the drain driver 13. Then, the drivers 11, 12, and 13 are operated, and an electric signal corresponding to the intensity and the amount of the reflected light incident on the DG-Trs 20, 20,... Is transferred to the drive circuit 10 via the drain driver 13, and the drive circuit 10 is driven. By detecting the level of the electric signal, the fingerprint image data of the fingertip 100 is obtained, and the fingerprint image data is output to the CPU 63.
[0054]
Further, since the middle segment of the finger 100 is placed on the pressure sensor 50, the CPU 63 recognizes that the middle segment of the finger is placed on the surface of the pressure sensor 50 based on the input pressure distribution data. Then, the CPU 63 determines whether or not the input fingerprint image data can be regarded as matching the registered fingerprint image data in the storage unit 66. Then, when the CPU 63 determines that the fingerprint image data matches the registered fingerprint image data, the CPU 63 starts the secret mode. The secret mode is a mode in which the CPU 63 can access a specific area and a normal area of the storage unit 66. On the other hand, if the CPU 63 does not consider that the fingerprint image data matches the registered fingerprint image data, it starts the normal mode. The normal mode is a mode in which the CPU 63 can access the normal area of the storage unit 66 and cannot access the specific area.
[0055]
The effect of the present embodiment will be described.
As shown in FIG. 2B, as the finger 100 is placed on the surface of the image reading circuit 2, the middle segment of the finger 100 is also placed on the surface of the pressure sensor 50, and the pressure sensor 50 is moved from the finger 100. , The detection that the finger 100 is placed on the surface 32a of the image reading circuit 2 is reliably performed by the pressure sensor 50 and the comparison circuit 62, and the image reading by the image reading circuit 2 is also reliably performed. . Therefore, the fingerprint image can be reliably read only by placing the finger 100 on the surface 32a of the image reading circuit 2 and the surface of the pressure sensor 50.
If the contact pressure between the finger 100 and the surface of the pressure sensor 50 is smaller than the threshold value, the convex portion of the finger 100 does not sufficiently contact the surface 32a of the image reading circuit 2, so that the fingerprint image may be unclear. If the level of the detection signal indicating the pressure applied from the finger 100 to the surface of the pressure sensor 50 does not exceed the threshold, the image reading circuit 2 does not perform the image reading operation. If the pressing force is at the determined level, the image reading circuit 2 can surely read the image as a clear fingerprint image, and there is no possibility that the read fingerprint image data is in an unclear state due to insufficient pressing.
Further, by adjusting the level of the threshold value in the comparison circuit 62, the image reading circuit 2 can perform the image reading operation only when the contact pressure between the finger 100 and the surface of the pressure sensor 50 becomes appropriate. . By doing so, the subject who has confirmed that no operation is performed can surely read clear fingerprint image data by strongly pressing the finger 100 against the image reading circuit 2 and the pressure sensor 50.
[0056]
[Second embodiment]
Next, as shown in FIGS. 6 to 8, a fingerprint reader 101 different from the fingerprint reader 1 of the first embodiment will be described.
[0057]
In the second embodiment, the light guide plate 15 overlaps the image reading circuit 2, and the surface of the light guide plate 15 facing the back surface of the image reading circuit 2 is in contact with the back surface of the image reading circuit 2.
[0058]
In the first embodiment, the surface of the pressure sensor 50 is flush with the surface 32a of the image reading circuit 2. However, in the second embodiment, the pressure sensor 50 overlaps the light guide plate 15 and the surface of the pressure sensor 50 overlaps. Are in contact with the back surface of the light guide plate 15. That is, the fingerprint reader 101 is configured by stacking the pressure sensor 50, the light guide plate 15, and the image reading circuit 2 in this order from the bottom. Therefore, the pressure applied to the surface 32 a of the image reading circuit 2 is also applied to the pressure sensor 50, and the pressure sensor 50 can detect the pressure of the surface 32 a of the image reading circuit 2. The pressure sensor 50 includes a plurality of electrode lines 51, 51,... Formed on a substrate 56 and extending in a row direction parallel to each other, and a plurality of electrode lines 52 extending in a column direction parallel to each other. , 52,... Are formed on the back surface, and a seal 54 covering the periphery of the sheet material 55 and joining the substrate 56 and the sheet material 55 is provided. Are separated from the plurality of electrode wires 51, 51,..., And are arranged such that the electrode wires 52 are orthogonal to the electrode wires 51 in plan view and the electrode wires 51 and 52 face each other. The material 55 and the substrate 56 are bonded together. Further, a pressure-sensitive ink layer may be provided on at least one surface of the electrode lines 51 and 52. In this case, the pressure-sensitive ink layer is arranged so as to overlap the electrode line 51 at the intersection with the electrode line 52. The electric resistance between the electrode wire 51 and the electrode wire 52 depends on the pressure applied to the pressure-sensitive ink layer, and has a characteristic that when the magnitude of the pressure changes, the electric resistance and the like change. The pressure sensor 50 can detect the pressure at the intersection between the electrode wire 51 and the electrode wire 52 based on the electrical resistance or the like at the intersection.
[0059]
Further, the fingerprint reading apparatus 101 of the second embodiment has an adjustment circuit 102 for adjusting the light emission intensity of the light source 14 as shown in FIG. 8, in addition to the circuit configuration shown in FIG.
Here, the detection drive circuit 61 outputs to the comparison circuit 62 a detection signal indicating the level of the entire pressure in the plane detected by the pressure sensor 50. When the pressure level is within the allowable range in which the finger is recognized as a finger, the comparison circuit 62 outputs a pressure information signal of the pressure level to the drive circuit 10 instead of the trigger signal. The drive circuit 10 outputs a light emission gradation signal of the light source 14 to the adjustment circuit 102 according to the pressure level of the pressure information signal. The adjustment circuit 102 causes the light source 14 to emit light with the brightness according to the emission gradation signal. That is, the adjustment circuit 102 starts the light emission of the light source 14 according to the pressure level, and adjusts the level of the power supplied to the light source 14 based on the pressure level, thereby adjusting the light emission intensity of the light source 14. In addition, the drive circuit 10 outputs the control signal Bcnt to the bottom gate driver 12 after the light source 14 emits light so that the bottom gate driver 12 appropriately outputs a read pulse, and outputs the control signal Tcnt to the top gate driver 11. By causing the top gate driver 11 to output a reset pulse as appropriate and outputting the control signal Dcnt to the drain driver 13, the drain driver 13 can output a precharge pulse as appropriate. Here, when the pressure level of the pressure information signal from the comparison circuit 62 is within the allowable range and low (the pressing force is small), the drive circuit 10 adjusts the light emission gradation signal such that the light emission luminance of the light source 14 becomes low. When the pressure level of the pressure information signal output from the comparison circuit 62 is within an allowable range and high (the pressing force is large), the light emission gradation signal that increases the light emission luminance of the light source 14 is output to the adjustment circuit 102. Is set to output to
[0060]
The components of the fingerprint reading apparatus 101 are the same as those of the fingerprint reading apparatus 1 except for the above description. The image reading circuit 2, the pressure sensor 50, the detection driving circuit 61, the CPU 63, the RAM 64 , The ROM 65 and the storage unit 66 will not be described in detail.
[0061]
Next, the operation and usage of the fingerprint reader 101 will be described.
As shown in FIG. 6A, when nothing is in contact with the front surface 32a of the image reading circuit 2, the pressure level of the detection signal output from the detection driving circuit 61 to the comparison circuit 62 is low, and Does not output the pressure information signal to the drive circuit 10, the drive circuit 10 does not cause the light source 14 to emit light via the adjustment circuit 102.
[0062]
On the other hand, as shown in FIGS. 6B and 7, when the subject places the last segment of the finger 100 on the surface 32 a of the discharge conductive film 32, pressure is applied from the finger 100 to the pressure sensor 50 via the image reading circuit 2. Is given. Since the pressure level of the detection signal output from the detection driving circuit 61 to the comparison circuit 62 is high, the comparison circuit 62 recognizes that the finger is placed according to the pressure level of the detection signal and determines how much pressure is applied. A pressure information signal including information on whether the pressure is present is output to the drive circuit 10. The drive circuit 10 outputs a light emission gradation signal to the adjustment circuit 102 according to the pressure information signal. The adjusting circuit 102 causes the light source 14 to emit light at a predetermined brightness according to the light emission gradation signal. Here, the adjustment circuit 102 adjusts the light emission intensity of the light source 14 so as to increase based on information in the light emission gradation signal, that is, as the pressing force on the surface 32a of the image reading circuit 2 decreases or decreases. When the detection signal output from the detection drive circuit 61 to the adjustment circuit 102 becomes lower than the level when nothing is placed on the discharge conductive film 32, that is, when pressure is applied to the pressure sensor 50, When the level falls below the level when the light source 14 is not in operation, the adjustment circuit 102 turns off the light source 14.
[0063]
When the light source 14 emits light, light enters the finger 100 from the light guide plate 15 via the image reading circuit 2, and the light reflected by the finger 100 enters the semiconductor film 23 of the DG-Trs 20, 20,. The in-plane intensity distribution of the reflected light incident on the semiconductor films 23 of the DG-Trs 20, 20,...
[0064]
The drive circuit 10 outputs a light emission gradation signal to cause the light source 14 to emit light, and then outputs a control signal to the drivers 11, 12, and 13 of the image reading circuit 2. The electric signals corresponding to the intensity of the reflected light incident on the DG-Trs 20, 20,... In the image reading circuit 2 are transferred to the drive circuit 10 via the drain driver 13 by the drivers 11, 12, 13, and the drive circuit The fingerprint image of the fingertip 100 is acquired by detecting the level of the electric signal by 10, and the fingerprint image data is output to the CPU 63. Then, the CPU 63 determines whether or not the inputted fingerprint image data can be regarded as matching the registered fingerprint image data in the storage unit 66. If the fingerprint image data can be regarded as matching the registered fingerprint image data, the CPU 63 starts the secret mode. If the fingerprint image data cannot be considered as matching the registered fingerprint image data, the CPU 63 starts the normal mode. .
[0065]
The effect of the present embodiment will be described.
As the pressure exerted by the finger 100 decreases or decreases, the contact area between the convex portion of the finger 100 and the surface 32a decreases, and the convex portion of the finger 100 does not come into close contact with the surface 32a. There is a possibility that the light enters the film 23. However, since the light emission intensity of the light source 14 increases as the pressure by the finger 100 decreases, the light incident on the finger 100 also increases, and even if the convex portion of the finger 100 is not in close contact with the surface 32a, the reflection of the convex portion does not occur. Light enters the semiconductor film 23 with light intensity.
If the light intensity of the light source 14 is high when the pressure by the finger 100 is large, the reflected light from the concave portion of the finger 100 also enters the semiconductor film 23 with high intensity, and the semiconductor of the DG-Trs 20, 20,. The in-plane intensity distribution of the reflected light incident on the film 23 becomes almost uniform and becomes bright. However, such a problem does not occur because the light emission intensity of the light source 14 decreases as the pressure by the finger 100 increases.
Therefore, in the present embodiment, the fingerprint image of the finger 100 can be clearly read by the image reading circuit 2 regardless of the pressure by the finger 100.
Further, the fingerprint reader 101 of the second embodiment has the same effect as the fingerprint reader 1 of the first embodiment.
Such an image input device can be applied as a personal identification system for doors or a solid identification image input device for restricting access to a personal computer or the like. It is especially effective for portable devices with limited size.
[0066]
The present invention is not limited to the above embodiments, and various improvements and design changes may be made without departing from the spirit of the present invention.
[0067]
In the above embodiments, the finger 100 is read. However, the reading is not limited to the finger 100, and may be performed by pressing various other subjects against the surface 32a of the discharge conductive film 32. When the subject is pressed against the surface 32a of the discharge conductive film 32, the pattern (including characters, numbers, pictures, etc.) drawn on the surface of the subject can be read by the image reading circuit 2, The pattern defined by the irregularities on the surface of the sample can be read by the image reading circuit 2.
In the above embodiments, the mounting surface on which the subject is mounted is the surface 32a of the conductive film 32 for discharge, but may be the surface of the insulating film provided on the conductive film 32 for discharge. The conductive film for discharge 32 may not be provided.
The fingerprint reading apparatus 101 having the structure in which the pressure sensor 50 is provided below the image reading circuit 2 in the second embodiment does not necessarily need to include the adjustment circuit 102 as shown in FIG. 8, and the circuit configuration shown in FIG. It may be. The fingerprint reading device 1 having the structure in which the pressure sensor 50 disposed so as not to overlap with the image reading circuit 2 in the first embodiment may not necessarily have the circuit configuration as shown in FIG. It may have the circuit configuration shown.
[0068]
In each of the above embodiments, the image reading circuit 2 using the DG-Tr 20, 20,... As the photoelectric conversion element has been described as an example, but the present invention is applied to an image reading circuit using a photodiode as the photoelectric conversion element. May be applied. Examples of an image reading circuit using a photodiode include a CCD image sensor and a CMOS image sensor.
[0069]
In a CCD image sensor, photodiodes are formed in a matrix on a substrate for each pixel, and a vertical CCD for transferring an electric signal photoelectrically converted by the photodiode is provided around each photodiode. , A horizontal CCD is formed.
[0070]
In a CMOS image sensor, photodiodes are formed in a matrix on a substrate for each pixel, and a pixel circuit for amplifying an electric signal photoelectrically converted by the photodiode is provided around each photodiode. Is provided.
Further, an image such as a fingerprint may be read by not only the optical sensor described above but also a contact sensor of a capacitance type.
[0071]
【The invention's effect】
According to the first aspect of the present invention, the image of the subject can be reliably read only by placing the subject on the placement surface.
According to the third aspect of the present invention, when the level of the detection signal indicating the pressure applied from the subject to the mounting surface exceeds the threshold, the comparing means outputs a trigger signal, and the image reading circuit performs the reading operation. Therefore, when the contact area between the subject and the mounting surface is large, the image is selectively read by the image reading circuit, so that a clear image can be reliably read.
According to the fifth aspect of the invention, the image of the subject can be read clearly regardless of the pressure applied from the subject to the mounting surface.
According to the ninth aspect of the present invention, since the detecting means for detecting the placement of the subject is disposed below the image reading circuit, the size of the image input device can be reduced.
[Brief description of the drawings]
FIG. 1 is a plan view showing a fingerprint reader to which the present invention is applied.
FIG. 2A is a cross-sectional view showing a state where a finger is not placed on a broken line BB in FIG. 1, and FIG. FIG. 2 is a cross-sectional view showing a state in which the cutting is performed along a line BB in FIG. 1.
FIG. 3 is a cross-sectional view showing an image reading circuit provided in the fingerprint reading apparatus in a cutaway manner.
FIG. 4A is a plan view showing one pixel of the image reading circuit, and FIG. 4B is a cross-sectional view taken along the line AA.
FIG. 5 is a block diagram showing a circuit configuration of the fingerprint reader.
FIG. 6A is a cross-sectional view showing a state in which a finger is not placed on a fingerprint reader different from the fingerprint reader, and FIG. 6B is a sectional view showing a state where the finger is placed on the fingerprint reader; FIG. 4 is a cross-sectional view showing a state where
FIG. 7 is a cross-sectional view of the fingerprint reader shown in FIG. 6 cut away.
8 is a block diagram showing a circuit configuration of the fingerprint reader shown in FIG.
[Explanation of symbols]
1,101 Fingerprint reader (image input device)
2 Image reading circuit
10 Drive circuit (drive means)
14. Light source (light irradiation means)
15 Light guide plate (light irradiation means)
32a Surface of image reading circuit (mounting surface)
50 pressure sensor (detection means)
62 Comparison circuit (detection means, comparison means)
100 fingertips (subject)
102 Adjustment circuit (adjustment means)

Claims (16)

An image reading circuit arranged below the mounting surface on which the subject is mounted,
Detecting means for detecting that the subject is mounted on the mounting surface by the pressure applied to the mounting surface,
An image input device comprising: 2. The image forming apparatus according to claim 1, further comprising a driving unit configured to cause the image reading circuit to perform an image reading operation when the detection unit detects that the subject is mounted on the mounting surface. Image input device. The detecting means,
A pressure sensor for detecting pressure applied to the mounting surface,
A trigger for comparing the pressure level detected by the pressure sensor with a threshold for partitioning between a mounted state and an unmounted state, and, when the threshold is exceeded, causing the image reading circuit to perform an image reading operation. 2. The image input device according to claim 1, further comprising a comparison unit that outputs a signal. The image input device according to claim 3, further comprising a light source that emits light from the subject based on the trigger signal. 2. The image input device according to claim 1, further comprising an adjustment unit configured to adjust brightness of a light source for irradiating the subject with light according to a pressure applied by the subject to the placement surface. 3. apparatus. The image input device according to claim 1, wherein the image reading circuit and the detection unit are arranged at different positions when viewed from the placement surface. The image input device according to claim 1, wherein the image reading circuit has an optical sensor. The image input device according to claim 7, wherein the optical sensor includes a plurality of double-gate transistors arranged in a matrix. An image reading circuit arranged below the mounting surface on which the subject is mounted,
Detecting means disposed below the image reading circuit and detecting that the subject is mounted on the mounting surface by the pressure applied to the mounting surface,
An image input device comprising: The apparatus according to claim 9, further comprising: a driving unit configured to cause the image reading circuit to perform an image reading operation when the detection unit detects that the subject is mounted on the mounting surface. Image input device. The detecting means,
A pressure sensor for detecting pressure applied to the mounting surface,
A trigger for comparing the pressure level detected by the pressure sensor with a threshold for partitioning between a mounted state and an unmounted state, and, when the threshold is exceeded, causing the image reading circuit to perform an image reading operation. The image input device according to claim 10, further comprising a comparison unit that outputs a signal. The image input device according to claim 9, wherein a light irradiation unit that irradiates light to the subject is arranged between the image reading circuit and the detection unit. The image input device according to claim 12, wherein the light irradiation unit includes a light guide plate that guides light from a light source that emits light when the object is detected by the detection unit to the object. apparatus. The image input device according to claim 9, further comprising an adjustment unit configured to adjust brightness of a light source that irradiates the subject with light according to the pressure applied to the placement surface by the subject. The image input device according to claim 9, wherein the image reading circuit includes an optical sensor. 16. The image input device according to claim 15, wherein the optical sensor has a plurality of double-gate transistors arranged in a matrix.

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