JP3425945B2 - Surface shape recognition sensor device - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a surface shape recognition sensor device, and more particularly to a surface shape recognition sensor device for detecting minute irregularities such as a human fingerprint or an animal nose print.

[0002]

2. Description of the Related Art As an application example of a surface shape recognition sensor device, many fingerprint sensors for detecting a fingerprint pattern have been proposed (for example, "ISSCC DIGEST OF TECHNICAL PAPE
RS "FEBRUARY 1998 pp.284-285 etc.). this is,
Detects the electrostatic capacitance formed between the sensor electrodes provided inside the cells (hereinafter referred to as sensor cells) arranged two-dimensionally on the LSI chip and the skin of the finger touched through the passivation film. Then, the uneven pattern of the fingerprint is sensed. Since the value of the capacitance formed by the unevenness of the fingerprint is different, the unevenness of the fingerprint can be sensed by detecting this capacitance difference.

FIG. 23 shows a conceptual diagram of the structure of a sensor cell of a conventional surface shape recognition sensor device used in such a surface shape recognition sensor device. The sensor cell 11 is the detection element 1
And the sensor circuit 2. The detection element 1 is an element for converting the surface shape into an electric signal. The sensor circuit 2 is a circuit that measures the amount of electricity of the detection element that changes depending on the surface shape. The output signal 2A output from the sensor cell 11 is input to the A / D conversion circuit 4 via the data line L _D and output as a digital output signal 4A. The data line L _D is shared by the plurality of sensor cells 11, the sensor cells 11 are sequentially selected, and the output signal 2A of the sensor cells 11 is sequentially input to the A / D conversion circuit 4.

FIG. 2 shows the structure of a specific sensor cell of a conventional example.
4 shows. The detection element 1 is an element for converting the surface shape into an electric signal 1A. The sensor circuit 2 is a circuit that measures the amount of electricity of the detection element 1 that changes depending on the surface shape.
The detection element 1 is formed on the insulating layer 16 and the passivation film 1
The electrostatic capacitance C _F , which is realized by the sensor electrode 1B covered with 5, is formed between the fingerprint (skin) 14 of the finger and the sensor electrode 1B as an electric signal. The sensor circuit 2 is Pch
It is composed of a MOSFET Q ₁ , Nch MOSFETs Q ₂ and Q ₃ , a constant current source I and a resistor R. C _P0 is a parasitic capacitance.

FIG. 25 shows an operation timing chart.
Before the time T1, the sensor circuit control signal PRE₀Power
Voltage V_DDControlled by Q₁Turns off, sensor circuit control
Signal RE is controlled to 0V and Q₂Is off
, Node N₁Is 0V. Signal PRE at time T1₀Is 0
Q controlled by V₁Turns on and node N₁Is V_DDRise to
It Then, at time T2, the signal PRE₀And the signal RE is V
_DDControlled to Q₁Turns off and Q₂Turns on
It As a result, the capacitance C_FCharge accumulated in the
And node N₁Potential gradually decreases. From time T2
At time T3 when Δt has passed, the signal RE is controlled to 0V.
Q₂When is turned off, the node N at that point₁Potential V _DD-Δ
V is maintained and Q₃Is output from. This allows electrostatic
Capacity C_FThe output signal 2A having a voltage corresponding to the value of
And by measuring the magnitude of this voltage signal
You can see the irregularities on the skin surface.

[0006]

However, in such a conventional surface shape recognition sensor device, although each sensor cell is manufactured with the same layout, the detection sensitivity of each sensor circuit 2 is actually different due to process variations. Not exactly the same. As a result, noise due to the sensitivity variation of the sensor circuit is included in the detected image, and the image quality deteriorates.
Further, a sensor having a poor detection performance is generated due to a variation between chips or a wafer variation. This lowers the yield of the sensor chip and raises the manufacturing cost. This becomes a big problem especially when the sensor chip is to be supplied at a low cost.

Further, even if the sensor has good detection performance, the detection performance will deteriorate if the surface of the sensor changes depending on the usage condition. This shortens the performance guarantee period, renders the module incorporating the sensor unusable, and necessitates frequent replacement of sensor components in a system using the sensor. For this reason, the cost of returned goods and system maintenance increases, which is a big problem. Therefore, as described above, the conventional surface shape recognition sensor device has a problem of increasing manufacturing cost and maintenance cost because it does not have means for individually adjusting the detection sensitivities of a plurality of sensor circuits. The present invention is intended to solve such a problem, and an object of the present invention is to provide a surface shape recognition sensor device having a higher yield than ever before.

[0008]

In order to achieve such an object, a surface shape recognition sensor device according to the present invention comprises:
A large number of detection elements adjacent to each other, a large number of sensor circuits connected to each detection element, and an output signal level correction circuit for correcting the output signal level of each sensor circuit are provided. A calibration circuit connected to the sensor circuit, and a comparison circuit that compares the output of the sensor circuit and the reference signal for calibration and outputs the difference output to the calibration circuit as a control signal are provided in the calibration circuit. Based on the control signal, the output signal level of the sensor circuit is corrected so that there is no difference between the output of the sensor circuit and the calibration reference signal.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, embodiments of the present invention will be described with reference to the drawings. (First Embodiment) FIG. 1 is an external view showing a surface shape recognition sensor device according to an embodiment of the present invention. This surface shape recognition sensor device 10 authenticates the recognition target by comparing and collating the shape of the verification target surface of the recognition target having fine irregularities with the verification data, for example. As shown in FIG. 1, the surface shape recognition sensor device 10 is composed of a large number of sensor cells adjacent to each other, and typically includes a large number of sensor cells 11 arranged two-dimensionally (in an array or a lattice). It is configured. When a recognition target such as a finger 13 is brought into contact with the sensor surface 12 of the surface shape recognition sensor device 10, the recognition target surface (here, the uneven shape of the fingerprint 14) is individually detected by each sensor cell 11, and the recognition target Two-dimensional data indicating the surface shape is output.

FIG. 2 shows the basic functional arrangement of such a surface shape recognition sensor device 10. The basic functional configuration of the surface shape recognition sensor device 10 is shown by representing one sensor cell 11 in consideration of the fact that many sensor cells have the same configuration. That is, as shown in FIG. 2, the sensor cell 11 is composed of a detection element 1, a sensor circuit 2, and an output signal level correction circuit 9, and this level correction circuit 15 takes in the output of the sensor circuit 2 and The output of 2 is supplied to one of the inputs of the comparison circuit 6.
The comparison circuit 6 compares the output of the sensor circuit 2 with the calibration reference value (signal) that is the output of the calibration reference signal generation circuit 7, and the input side of the sensor circuit 2 or The output level of the sensor circuit 2 is adjusted by controlling the gain of the sensor circuit 2 or the like.

Calibration reference signal generation circuit 7
Is preferably configured to generate the same level of calibration reference signal for each sensor cell. This output signal level correction circuit 9 is provided for each sensor cell 1
1 has a function of working so as to eliminate variations in the output of 1 as much as possible, and various known configurations can be applied as long as they perform such an operation. The details will be sequentially described in the following embodiments. If you do this,
The output of each sensor circuit, that is, the output level of each sensor cell 11 can be adjusted to the same level, and the yield of the sensor device can be increased more than before.

(Second Embodiment) FIG. 3 shows a second embodiment of the present invention.
It is composed of a large number of sensor cells 11 arranged two-dimensionally (in an array or a lattice). By bringing a recognition target such as a finger 13 into contact with the sensor surface 12 of the surface shape recognition sensor device 10, the recognition target surface (here, the fingerprint 14
The uneven shape) is individually detected by each sensor cell 11, and two-dimensional data indicating the surface shape of the recognition target is output.

Surface shape recognition sensor device 1 shown in FIG.
Each of the sensor cells 0 of 0 has the same configuration, and the detection element 1, the sensor circuit 2 and the calibration circuit (sensitivity adjustment circuit) are the same as in the above-described embodiment.
3, and has a means for adjusting the detection sensitivity of each sensor cell 11 using the calibration circuit 3 as a main feature. The biggest difference is that the calibration circuit 3, the signal processing circuit 5, and the control line L _C are provided as compared with the above-described conventional sensor cell (see FIG. 23).

The sensor cell 11 comprises a detection element 1, a sensor circuit 2 and a calibration circuit 3. The detection element 1 is an element for converting the surface shape into an electric signal. The sensor circuit 2 is a circuit that measures the amount of electricity of the detection element 1 that changes depending on the surface shape. Each sensor cell 11
When the output level correction, that is, the calibration is performed, the sensor cell 11 detects a reference sample having no unevenness as an object to be measured, or the detection is performed without placing anything on the sensor cell, so that the same measurement is performed on each sensor cell 11. Let the value be detected. The signal output from the sensor cell 11 is input to the A / D conversion circuit 4 via the data line L _D and output as a digital output signal 4A.

The digital output signal 4A output from the A / D conversion circuit 4 is also input to the signal processing circuit 5. The signal processing circuit 5 adjusts the detection sensitivity of the sensor circuit 2 by comparing the digital output signal 4A output from the A / D conversion circuit 4 with a digital output signal that should be originally output (hereinafter, referred to as an expected value). The adjustment parameter for calculating is calculated. Then, the calibration circuit 3 is controlled using the control line L _C based on the calculated adjustment parameter.

The data line L _D and the control line L _C are shared by the respective sensor cells 11, the sensor cells 11 are sequentially selected, and the output signal 2A of the sensor cells 11 is sequentially A / A.
The signal is input to the D conversion circuit 4, and the signal processing circuit 5 controls the calibration circuit 3 in the sensor cell 11.
By repeating this operation once or plural times for each sensor cell 11, the sensitivity of each sensor circuit 2 is adjusted,
The performance of each sensor cell 11 is made uniform.

In this case, the signal processing circuit 5 has the comparison circuit 6 described in FIG. 2 and the calibration reference signal generation circuit 7. In this example, the input signal is digital, and thus the comparison circuit 6 remains the digital signal.
In the case of inputting to, a known digital comparison circuit is used as the comparison circuit. If the comparison circuit is a path below the normal analog comparison, it is once D / A converted and supplied to the comparison circuit. Of course, the same applies to the calibration reference signal generation circuit.

FIG. 4 shows an implementation example of the calibration circuit 3 shown in FIG. The calibration circuit 3 includes a load circuit 31 and a memory circuit 32. The adjustment parameter calculated by the signal processing circuit 5 is written in the memory circuit, and the load circuit 31 is controlled by the data written in the memory circuit 32.

FIG. 5 shows a specific calibration circuit 3
An example of the circuit configuration of the sensor cell 11 having the is shown. In the load circuit 31, N (N is a natural number) load elements Z _{1 to} Z _N are connected to the sensor circuit 2 via switches, respectively.
The memory circuit 32 is an N-bit memory circuit, and controls the conduction state of each switch of the load circuit 31 based on the written data. The memory circuit 32 is SRAM or DRA.
It can be realized by M or a writable non-volatile memory.

The switch has a switching control signal S as shown in FIG.
It can be realized by a MOSFET operating in W. In Figure 6, Nch
Although an example using a MOSFET is shown, Pch MOSFET
However, both may be used.

As the load elements Z _{1 to} Z _N, there are capacitance elements and resistance elements as shown in FIG. As shown in FIG. 5, when the shape of the recognition target is detected by the detection element 1 as a change in the capacitance value, a capacitance element may be used as the load element, and the PIP capacitance or MIM capacitance, or FIG. It can be realized with a MOS capacitor as shown in a). Also,
When the surface shape is detected by the detection element 1 as a change in resistance value, a resistance element may be used as the load element,
Although an example using an Nch MOSFET is shown here, which can be realized by a polysilicon resistor or a MOS resistor as shown in FIG. 7B, a Pch MOSFET may be used.

Next, the operating principle of the calibration circuit 3 will be briefly described. For example, it is assumed that the value of the parasitic capacitance C _P0 generated in the sensor circuit 2 of FIG. Capacitance elements are used as the load elements Z _{1 to} Z _N , and an appropriate number of switches are made conductive to connect to the sensor circuit 2. If data is written in the memory circuit 32 such that the sum of the parasitic capacitance C _P0 connected to the sensor circuit 2 and the load elements Z _{1 to} Z _N composed of capacitive elements becomes the same for each sensor circuit 2, process variations will occur. The variation in the performance of the sensor cells 11 due to the above is not visible, and as a result, the performance of each sensor cell 11 can be made uniform.

FIG. 8 shows another circuit configuration example of the sensor cell having a specific calibration circuit. In the load circuit 31, N (N is a natural number) load elements Z _{1 to} Z _N are respectively connected to the sensor circuit 2, and each load element is individually controlled to either an active state or an inactive state. be able to. The memory circuit 32 is an N-bit memory circuit, and controls the active state of each load circuit 31 based on the written data. The memory circuit 32 is SRAM
Or a DRAM or a writable non-volatile memory. As load elements that can be controlled to be switched between the active state and the inactive state, there are a capacitive element and a resistive element as shown in FIG.

As shown in FIG. 9A, the capacitive element controls the potential of the gate terminal or the source terminal and the drain terminal of the MOS capacitor which is activated or deactivated by the switching control signal SW. realizable. Similarly, the resistance element can be realized by a MOS resistance as shown in FIG. Although the case where the Nch MOSFET is used is shown here, a Pch MOSFET may be used. By using a load element that can be controlled to either the active state or the inactive state, the parasitic capacitance and the parasitic resistance of the switch are not connected as compared to the case of using the switch as in the configuration example of FIG. The effect is that sensitivity can be adjusted.

(Third Embodiment) Next, a surface shape recognition sensor device according to a third embodiment of the present invention will be described with reference to FIG. The surface shape recognition sensor device shown in FIG. 10 is different from the above-described second embodiment (see FIG. 3) in that the holding circuit 52 is provided and the control line L _C is not used in FIG. 10.

When calibrating each sensor cell 11, the sensor cell 11 detects a reference sample having no unevenness as an object to be measured, or the detection is performed without placing anything on the sensor cell 11, so that the same sensor cell 11 is obtained. Detect the measured value. The output signal 2A output from the sensor cell 11 is input to the A / D conversion circuit 4 via the data line L _D and is output as a digital output signal 4A.

The digital output signal 4A output from the A / D conversion circuit 4 is also input to the signal processing circuit 5. The signal processing circuit 5 compares the digital output signal 4A output from the A / D conversion circuit 4 with an expected value to calculate an adjustment parameter for the detection sensitivity of the sensor circuit 2. The calculated adjustment parameter is held in the holding circuit 52. Sensor cell 1
After the signal output from 1 is completed, the calibration circuit 3 is controlled by the data held in the holding circuit 52 via the data line L _D. Data line L _D is for each sensor cell 1
1 is shared, the sensor cells 11 are sequentially selected, and the above operation is performed. By repeating this operation once or plural times for each sensor cell, the sensitivity of each sensor circuit 2 is adjusted, and the performance of each sensor cell 11 is made uniform. Therefore, as compared with the first embodiment, the data line L _D and the control line L _C can be shared, and the number of wirings can be reduced.

In the third embodiment shown in FIG. 10, the signal processing circuit 5 has the comparison circuit 6 and the calibration reference signal generation circuit 7 described in FIG. In this example, the input signal is digital,
When the digital signal is input to the comparison circuit 6 as it is, a known digital comparison circuit is used as the comparison circuit. If the comparison circuit is a normal analog comparison circuit, it is once D / A converted and supplied to the comparison circuit. Of course, the same applies to the calibration reference signal generation circuit.

(Fourth Embodiment) Next, a surface shape recognition sensor device according to a fourth embodiment of the present invention will be described with reference to FIG. The fourth embodiment of the present invention shown in FIG. 11 and the above-described second embodiment (FIG. 3)
2) is different from that of FIG. 2) in that the signal of the data line L _D , which is an analog signal, is input to the input side of the comparison circuit 6 included in the signal processing circuit 5.

When each sensor cell 11 is calibrated, the reference sample having no unevenness as the object to be measured is detected by the sensor cell 11 or the sensor cell 11 is not placed and the detection is performed so that the same sensor cell 11 is obtained. Detect the measured value.

Output signal 2 output from the sensor cell 11
A is input to the A / D conversion circuit 4 via the data line L _D and output as a digital output signal 4A. At the same time, the output signal 2A from the sensor cell 11 is also input to the comparison circuit 6. The comparison circuit 6 compares the analog output signal 2A output from the sensor cell 11 with the signal to be originally output, that is, the reference signal, and controls the calibration circuit 3 via the control line L _{C according} to the result.

For example, when the analog output signal 2A output from the sensor cell 11 is a voltage signal, a PchMOSFETQ as shown in FIG.
A general comparator circuit configuration using ₄ , Q ₅ and Nch MOSFETs Q ₆ , Q ₇ may be used.

In the comparison circuit 6 shown in FIG. 12, the reference signal for calibration becomes the reference voltage V _REF , and the input voltage V _IN of the output signal 2A of the sensor cell 11 and the reference voltage V _REF .
_REF is compared. The comparison circuit 6 depends on the size of this comparison.
A high-level or low-level control signal 5A is output as an output OUT of the calibration circuit 3 is controlled by the control signal 5A. The data line L _D and the control line L _C are shared by the respective sensor cells 11, and the sensor cells 11 are sequentially selected and the sensor cells 1 are sequentially selected.
The output signal 2A of 1 controls the calibration circuit 3 in the sensor cell by the comparison circuit 6.

By repeating this operation once or multiple times for each sensor cell, each sensor circuit 2
Output level is adjusted, and the performance of each sensor cell 11 is made uniform. Therefore, as compared with the signal processing circuit 5 that calculates the adjustment parameter by comparing the digital output signal 4A as in the first embodiment, there is an effect that a circuit for comparison can be realized on a small scale. Further, since the calibration circuit 3 can be controlled without going through the A / D conversion circuit 4, as a result, there is an effect that the calibration can be performed at high speed.

FIG. 13 shows an example of the structure of a memory cell including a calibration circuit when a comparison circuit is used as in the fourth embodiment (see FIG. 11). The calibration circuit 3 includes a load circuit 31 and a shift register circuit 3
It consists of three. Control signal 5 output from the comparison circuit 6
A is written in the shift register 33, and the load circuit 31 is controlled by the data written in the shift register 33.

FIG. 14 shows a specific example of the calibration circuit 3 shown in FIG. Load circuit 31 here
Has N (N is a natural number) load elements Z _{1 to} Z _N each connected to the sensor circuit 2, and each load element can be individually controlled to either an active state or an inactive state. . The load circuit 31 may be a load circuit using the switch shown in FIG.

The shift register 33 is an N-bit shift register, and controls the active state of the load circuit 31 based on the data written in the shift register 33. The operation principle of the calibration circuit 3 having the shift register 33 will be briefly described. First, the value of the shift register 33 is previously set all the load elements Z ₁ to Z _N to the initial setting value such as to control the inactive state. In the first sensing operation, when the output signal 2A from the sensor circuit 2 and the reference signal do not match (for example, when the output signal 2A is smaller than the reference signal), the comparison circuit 6 controls the load element to activate. The signal 5A (write data for the shift register 33: for example, "1") is output as data, and the data is written to the shift register 33 for one bit.

Next, in the second sensing operation, the output signal 2
When A and the reference signal do not match (for example, output signal 2A
Is smaller than the reference signal), the comparison circuit 6 outputs the control signal 5A for activating the load element as data as in the previous case. This data is further written in the shift register 33 as one bit. Since the shift register 33 has a function of shifting the previous data by one,
As a result, the two load elements are activated.
Such an operation is repeated until the output signal 2A and the reference signal match each other, strictly speaking, until the output signal 2A of the sensor cell 11 exceeds the reference signal (for example, becomes larger than the reference signal).

When the output signal 2A exceeds the level of the reference signal, the control signal 5A (shift register 3) from the comparison circuit 6 to the sist register 33 controls the load element to the inactive state.
For 3, the write data: "0", for example, is output as data. This data is only added to the shift register 33, and the new load element is not controlled to be in the active state, and the load element is not connected to the sensor circuit 2 any more. Therefore, the control signal 5A from the comparison circuit 6
Thus, the load elements are sequentially connected, and the output signal 2A equal to the reference signal is output from the sensor cell 11. In this case, a change in the control signal 5A from the comparison circuit 6 may be used to control so that writing to the shift register cannot be performed.

FIG. 15 shows another configuration example of the calibration circuit when the comparison circuit is used as in the fourth embodiment (see FIG. 11). This calibration circuit 3
Is composed of a load circuit 31 and a counter circuit 34. Here, the counter circuit 34 is controlled by the signal output from the comparison circuit 6, and the load circuit is controlled by the data of the counter circuit 34.

FIG. 16 shows a specific example of a sensor cell having a calibration circuit using the counter circuit of FIG. In the load circuit 31 here, N (N is a natural number) load elements Z _{1 to} Z _N are connected to the sensor circuit 2, and each load element is individually in an active state or an inactive state. Can be controlled. The load circuit 31 may be a load circuit using the switch shown in FIG. The counter circuit 34 is an N-bit counter circuit, and controls the activation state of the load circuit 31 based on the data of the counter circuit 34.

The operation principle of the calibration circuit using the counter circuit 34 will be briefly described. First, the value of the counter circuit 34 is set in advance all the load elements Z ₁ to Z _N to the initial setting value such as to control the inactive state. In the first sense operation, when the output signal 2A from the sensor circuit 2 does not match the reference signal (for example, the output signal 2
When A is smaller than the reference signal), the output of the comparison circuit 6, that is, the control signal 5A changes. Due to the change in the control signal 5A, the counter circuit 34 increments by one. As a result, the data of the counter circuit changes so as to activate one load element. Then, the output signal of the comparison circuit is returned to the initial setting value.

Next, in the second sense operation, the output signal 2A
And the reference signal do not match (for example, output signal 2A
Is smaller than the reference signal), the control signal 5A from the comparison circuit 6 changes again. As a result, the counter circuit 34
Is incremented by one. Where, for example, Z
_{1 = Z, Z 2 = 2Z} , Z 3 = 4Z, ..., Z N = 2 (N-1) may be set as Z, so as to control the Z ₁ to Z _N from the lower bits of the counter circuit 34 in order If this is done, the value of the load element connected to the sensor circuit 2 will increase by Z each time it is counted up.

This operation corresponds to the output signal 2 of the sensor cell 11.
Strictly speaking, the output signal 2A exceeds the reference signal (for example, becomes larger than the reference signal) until A matches the reference signal.
Is repeated until. When they match, the output of the comparison circuit 6 does not change, so the counter signal 34
Is not counted up, and no more load elements are connected to the sensor circuit 2.

As described above, when the counter circuit 34 is used, the control can be simplified as compared with the case where the shift register is used, and if the value of the load element is set as described above, 2 ⁽ It is possible to increase the set number of load circuits by ^N-1) -N. Further, if the set numbers are the same, the number of bits of the counter circuit 34 can be reduced, and the circuit scale can be made smaller than that of the shift register.

FIG. 17 shows a configuration example of the counter circuit 34 and the load circuit 31 shown in FIGS. Regarding the load circuit 31, the connection relationship when a MOS capacitor is used as a load element which can be switched between an active state and an inactive state is also shown. The counter circuit 34 here is 3
This is a counter circuit with a bit clear, which uses a RAM type latch circuit, and can reduce the circuit scale as compared with the case where a latch circuit composed of a transfer gate or a clocked CMOS circuit is used. In particular, the sensor cell 11 used in the surface shape recognition sensor device has a size of 50
Since it is as small as about μm square, it is desirable that the calibration circuit arranged therein is small. Therefore, there is an effect that the calibration circuit can be downsized by using the counter circuit of FIG. Also, the shift register 33 described above can be downsized by implementing it using a RAM type latch circuit.

(Fifth Embodiment) Next, a surface shape recognition sensor device 10 according to a fifth embodiment of the present invention will be described with reference to FIG. A fifth embodiment of the present invention shown in FIG. 18 and the above-described fourth embodiment (FIG. 1)
1) has a holding circuit 52 and a control line L
_The difference is that there is no _C. When each sensor cell 11 is calibrated, the sensor cell detects the same measurement value by detecting a reference sample having no irregularities as an object to be measured by the sensor cell or by placing nothing on the sensor cell. .

The output signal 2A from the sensor cell 11 is
Data line L_DIs input to the A / D conversion circuit 4 via
Is output as the output signal 4A. At the same time the sensor
The output signal 2A from the cell 11 is also input to the comparison circuit 6.
It The comparator circuit 6 compares the analog output signal 2A with the calibration signal.
Comparison reference signal from the reference signal generation circuit
Then, the result is held in the holding circuit 52. Sensor cell
Hold in holding circuit 52 after signal output from 11 is completed
The comparison result is the data line L as the control signal 5A. _DThrough
Then, it is output to the calibration circuit 3 and controlled.
Data line L_DIs shared by multiple sensor cells 11.
The sensor cell 11 is sequentially selected and the above operation is performed.
Be seen. Repeat this operation once for each sensor cell 11.
Is repeated multiple times, the sensitivity of each sensor circuit 2
The performance of each sensor cell is adjusted to be uniform. But
Therefore, as compared with the fourth embodiment, the data line L_DAnd control
Line L_CAnd can be shared, and the number of wires can be reduced.
It

(Sixth Embodiment) Next, a surface shape recognition sensor device 10 according to a sixth embodiment of the present invention will be described with reference to FIG. The surface shape recognition sensor device 10 according to the sixth embodiment of the present invention shown in FIG. 19 and the fifth embodiment (see FIG. 18) are compared with each other by a comparison circuit 6
Is different from the sensor cell 11 in that it is built in the sensor cell 11 and there is no holding circuit 52. When calibrating each sensor cell 11, each sensor cell 11 can be detected by detecting a reference sample having no unevenness as the object to be measured with the sensor cell or by placing nothing on the sensor cell.
To detect the same measured value.

The output signal 2A from the sensor cell 11 is input to the A / D conversion circuit 4 via the data line L _D and output as a digital output signal 4A. At the same time, the output signal 2A is input to the comparison circuit 6 inside the sensor cell 11. The comparison circuit 6 compares the analog output signal 2A with the reference signal from the calibration reference signal generation circuit, and controls the calibration circuit 3 according to the result. The data line L _D is shared by a plurality of sensor cells 11, the sensor cells 11 are sequentially selected, and the above operation is performed. By repeating this operation once or plural times for each sensor cell 11, the output level of each sensor circuit 2 is adjusted, and the performance of each sensor cell is made uniform.

Therefore, as compared with the fifth embodiment described above, the control of the calibration circuit 3 by the comparison circuit 6 can be performed without passing through the data line L _D , so that the calibration is performed regardless of the signal output timing of the sensor cell 11. As a result, there is an effect that calibration can be performed at high speed. Further, even if a plurality of sensor cells 11 are selected at the same time, the calibration can be performed in parallel for each sensor cell 11, and as a result, the calibration can be performed at a higher speed.

(Seventh Embodiment) Next, a surface shape recognition sensor device 10 according to a seventh embodiment of the present invention will be described with reference to FIG. In the seventh embodiment of the present invention shown in FIG. 20 and the sixth embodiment described above, in the sensor cell 11, the sensor circuit 21 with the voltage-time conversion function and the time signal comparison circuit 57 are used as sensor circuits.
Is different.

When each sensor cell 11 is calibrated, a reference sample having no unevenness as an object to be measured is detected by the sensor cell or is placed without any sensor cell, and the same measurement value is obtained for each sensor cell 11. To be detected.

Sensor circuit 21 with voltage-time conversion function
Converts a signal having analog information as a voltage value into a signal having analog information in the time axis direction and outputs it as an output signal 2B as shown in FIG. 22 (see FIG. 22: t _S is the output time). , This t _S changes). The output signal 2B is input to the A / D conversion circuit 4 via the data line L _D and output as a digital output signal. At the same time, this output signal 2B is supplied to the calibration circuit 3 via the time signal comparison circuit 57 inside the sensor cell. This time signal comparison circuit 57 corresponds to the comparison circuit 6 of FIG. 2 and calculates the time difference between the digital output 2B of the sensor circuit 21 and the reference pulse signal having the reference time t _R from the calibration reference signal generation circuit. Ask.

The time signal comparison circuit 57 includes the sensor circuit 21.
The voltage-time converted signal is compared with the reference pulse signal and the comparison pulse signal representing the time difference is sent to the calibration circuit. As a result, the calibration circuit 3 performs control operation so that there is no time difference between the reference pulse signal and the sensor circuit output. The data line L _D is shared by the plurality of sensor cells 11, and the sensor cells 11 are sequentially arranged.
Is selected and the above operation is performed.

By repeating this operation once or plural times for each sensor cell 11, the sensitivity of each sensor circuit 21 is adjusted and the performance of each sensor cell 11 is made uniform.
Of course, similarly to the fifth embodiment described above, even if a plurality of sensor cells 11 are selected at the same time, the calibration can be performed in parallel for each sensor cell, and the calibration can be performed at high speed.

FIG. 21 shows a sensor with a voltage-time conversion function.
The specific structural example of the sensor cell which has a circuit is shown. Cat
As the calibration circuit 3, the counter shown in FIG. 16 is used.
This is the same as that using the input circuit 34. Voltage-time conversion
The internal configuration of the sensor circuit with function 21 has been described above.
Compared with the sensor circuit 2 of FIG. 4, Nch MOSFETQ ₃
And a voltage-time conversion circuit 22 is provided instead of the resistor R.
Has been.

As the voltage-time conversion circuit 22, a general-purpose one may be used, and as shown in FIG.
It may be composed of a constant current circuit, a capacitor C _L, and a threshold circuit 23 (for example, see Japanese Patent Application No. 11-157755).

The operation principle of the calibration circuit when the sensor circuit 21 with the voltage-time conversion function is used will be briefly described with reference to FIG. First, the time signal comparison circuit 57 is typically composed of an AND circuit, and ANDs the output signal 2B of the sensor circuit 21 with the voltage-time conversion function and the reference pulse signal from the reference pulse signal generation circuit, The result is output to the counter circuit 34 as a comparison pulse signal.

The value of the counter circuit 34 is preset to an initial setting value for controlling all the load elements Z _{1 to} Z _N to the inactive state, and further, the sensor circuit 2 with the voltage-time conversion function.
The output signal 2B of 1 is also set to the initial setting value. In the first sense operation, when the output signal 2B changes earlier than a predetermined time (for example, when the sensing operation is performed without placing the finger 13 and the output signal of the sensor cell changes during the sensing time), the time signal Based on the output of the comparison circuit 57, the counter circuit 34 increments by one. As a result, the data in the counter circuit 34 changes so as to activate one load element. Then, the output signal 2B of the sensor circuit 21 with the voltage-time conversion function is also returned to the initial setting value.

Next, when the output signal changes faster than a predetermined time even in the second sensing operation (for example, when the sensing operation is performed without placing the finger 13 and the output signal of the sensor cell changes during the sensing time). The counter circuit 34 is further incremented by one. Here, if the value of the load element is set to be doubled according to the digit of the counter, as a result, double the number of load elements will be activated.
For example, Z ₁ = Z, Z ₂ = 2Z, Z ₃ = 4Z, ..., Z _N = 2
^{If (N-1)} Z is set and Z _{1 to} Z _N are controlled in order from the lower bit of the counter circuit 34, the value of the load element connected to the sensor circuit 21 will be Z at each count up. It will become bigger and bigger.

This operation is performed until the output signal of the sensor circuit 21 with the voltage-time conversion function does not change within a predetermined time (for example, the sensing operation is performed without placing the finger 13 and the output of the sensor cell is output during the sensing time). Repeat until the signal stops changing). When the output signal does not change within the predetermined time, the counter circuit 34 is not counted up and the load element is not connected to the sensor circuit 21 any more.

By performing the voltage-time conversion in this manner, the direct current does not flow in the output level correction system including the calibration, so that the power consumption of the entire apparatus can be reduced as compared with the other embodiments.

As described above, by adding the calibration circuit 3 to the sensor circuit 2 and connecting an appropriate number of load elements inside the calibration circuit 3 to the sensor circuit 2, the performance of the sensor cell due to process variations and the like can be improved. The variation becomes invisible, and as a result, the performance of each sensor cell can be made uniform.

[0065]

As described above, in the surface shape recognition sensor device of the present invention, since the calibration circuit is built in the sensor cell, the detection sensitivity of each sensor cell is adjusted by using this calibration circuit. be able to. Therefore, by applying the sensor of the present invention to the surface shape recognition sensor device, it is possible to individually adjust the detection sensitivities of a plurality of sensor circuits, and the performance variation of the sensor cell due to process variation or the like becomes invisible, and as a result, each sensor cell The performance can be made uniform. As a result, it is possible to prevent the image quality from being deteriorated due to the noise due to the variation in the sensitivity of the sensor circuit in the detected image, and it is possible to improve the manufacturing yield of the device as compared with the conventional case.

Further, variations in the detection performance of the sensor due to variations among chips and variations in wafers can be made uniform, which has the effect of improving the yield of sensor chips and reducing the manufacturing cost. This is a great advantage especially when the sensor chip is to be supplied inexpensively. Further, even if the sensor surface having a good detection performance can be calibrated at the time of use even when the sensor surface changes depending on the usage state, there is an effect of preventing the detection performance from deteriorating. This can prolong the performance guarantee period, prolong the service life of the module incorporating the sensor, and reduce the frequency of replacement of sensor parts in a system using the sensor. As a result, there is an effect that costs for handling returns and system maintenance can be reduced.

[Brief description of drawings]

FIG. 1 is an external view showing a surface shape recognition sensor device according to an embodiment of the present invention.

FIG. 2 is a functional block diagram showing a basic configuration of the first embodiment.

FIG. 3 is a functional block diagram of a surface shape recognition sensor device according to a second embodiment.

FIG. 4 is a configuration example of a calibration circuit shown in FIG.

FIG. 5 is a circuit configuration example of a sensor cell having a calibration circuit.

FIG. 6 is a configuration example of a switch.

FIG. 7 is a configuration example of a load element.

FIG. 8 is another circuit configuration example of a sensor cell having a calibration circuit.

FIG. 9 is another configuration example of the load element.

FIG. 10 is a functional block diagram of a surface shape recognition sensor device according to a third embodiment.

FIG. 11 is a functional block diagram of a surface shape recognition sensor device according to a fourth embodiment.

12 is a configuration example of the comparison circuit shown in FIG.

FIG. 13 is a configuration example of a calibration circuit using a comparison circuit.

FIG. 14 is a configuration example of a sensor cell having a calibration circuit using a shift register.

FIG. 15 is another configuration example of the calibration circuit using the comparison circuit.

FIG. 16 is a specific configuration example of a sensor cell having a calibration circuit using a counter circuit.

FIG. 17 is a configuration example of a counter circuit.

FIG. 18 is a functional block diagram of a surface shape recognition sensor device according to a fifth embodiment.

FIG. 19 is a functional block diagram of a surface shape recognition sensor device according to a sixth embodiment.

FIG. 20 is a functional block diagram of a surface shape recognition sensor device according to a seventh embodiment.

21 is a specific configuration example of the surface shape recognition sensor device shown in FIG.

22 is a timing chart showing a specific operation of FIG.

FIG. 23 is a functional block diagram of a conventional surface shape recognition sensor device.

FIG. 24 is a specific configuration example of the sensor cell of FIG. 23.

FIG. 25 is an operation timing chart of the sensor cell of FIG. 23.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Detection element, 1A ... Electric signal (electric quantity), 1B ... Sensor electrode, 2 ... Sensor circuit, 2A ... Output signal, 21 ... Sensor circuit with voltage-time conversion function, 2B ... Output signal, 22
... voltage-time conversion circuit, 23 ... threshold circuit, 3 ... calibration circuit, 31 ... load circuit, 32 ... memory circuit, 33 ... shift register, 34 ... counter circuit, 4 ...
A / D conversion circuit, 4A ... Digital output signal, 5 ... Signal processing circuit, 5A ... Control signal, 52 ... Holding circuit, 57 ... Time signal comparison circuit, 6 ... Comparison circuit, 7 ... Calibration reference signal generation circuit, 9 ... Output signal level correction circuit, 1
0 ... Surface shape recognition sensor device, 11 ... Sensor cell, 12
... sensor surface, 13 ... finger 14 ... fingerprint, 15 ... passivation film, 16 ... insulating layer, R ... resistance, C ... capacitance, I ... current source, SW ... switching control signal, L _D ... data line, L _C ... Control line, Z _{1 to} Z _N ... Load element, V _B ... Bias voltage, V _DD ...
Power supply voltage, V _IN ... Input voltage, V _REF ... Reference voltage, C _F ... Detection capacitance, C _P0 ... Parasitic capacitance, C _L ... Capacitance element, Q ₁ , Q ₄ ,
Q ₅ ... Pch MOSFET, Q ₂ , Q ₃ , Q ₆ , Q ₇ ... NchM
OSFET, RE, PRE ₀ ... Sensor circuit control signal, N ₁
…node.

─────────────────────────────────────────────────── ─── Continued Front Page (72) Inventor Katsuyuki Machida 2-3-3 Otemachi, Chiyoda-ku, Tokyo Inside Nippon Telegraph and Telephone Corporation (72) Inventor Tsuru Kuraki 2-3-3 Otemachi, Chiyoda-ku, Tokyo No. 1 in Nippon Telegraph and Telephone Corporation (56) Reference JP-A-9-292410 (JP, A) JP-A-2000-322559 (JP, A) JP-A-4-98633 (JP, A) JP-A-60- 5324 (JP, A) JP 2000-28311 (JP, A) JP 2000-5151 (JP, A) JP 10-300610 (JP, A) JP 11-103419 (JP, A) JP Flat 10-239093 (JP, A) JP 4-313020 (JP, A) JP 3-51714 (JP, A) Special Table 10-508943 (JP, A) Special Table 11-508698 (JP , A) (58) Fields surveyed (Int.Cl. ⁷ , DB name) G01B 7/28 A61B 5/117 G01D 18/00

Claims (15)

(57) [Claims] 1. An output signal level comprising: a plurality of detection elements adjacent to each other; a plurality of sensor circuits connected to each detection element; and an output signal level correction circuit for correcting an output signal level of each sensor circuit. The correction circuit is a calibration circuit connected to each of the sensor circuits, and a comparison circuit that compares the output of the sensor circuit and a calibration reference signal and outputs the difference output to the calibration circuit as a control signal. The surface shape recognition, wherein the calibration circuit corrects the output signal level of the sensor circuit based on the control signal so that there is no difference between the output of the sensor circuit and the calibration reference signal. Sensor device. 2. The surface shape recognition sensor device according to claim 1, wherein one of the detection elements, a sensor circuit connected to the detection element, and an output connected to the sensor circuit and correcting the output signal level thereof. At least the calibration circuit among the elements constituting the signal level correction circuit constitutes one sensor cell, and the surface shape recognition sensor device. 3. The surface shape recognition sensor device according to claim 1, further comprising a conversion circuit for converting each of the output signals obtained from each of the sensor circuits via a common data line into a digital output signal. The digital output signal from the conversion circuit is subjected to signal processing to generate the control signal for controlling the calibration circuit, and the control signal is output to the calibration circuit corresponding to each digital output signal via a shared control line. And a signal processing circuit for performing comparison between the output of the sensor circuit and the calibration reference signal and supplying the difference output to the calibration circuit. A surface shape recognition sensor device characterized by being present. 4. The surface shape recognition sensor device according to claim 1, further comprising a conversion circuit for converting each of the output signals obtained via the common data line from each of the sensor circuits into a digital output signal. A signal processing circuit that processes each digital output signal from the conversion circuit to generate the control signal that controls the calibration circuit; and a holding circuit that holds an output of the signal processing circuit. The circuit is configured by the comparison circuit that compares the output of the sensor circuit and the calibration reference signal and supplies the difference output to the calibration circuit, and the output of the holding circuit is a common data line. A surface shape recognition sensor device, which is output to a calibration circuit corresponding to the digital output signal via the surface shape recognition sensor device. 5. The surface shape recognition sensor device according to claim 1, further comprising a conversion circuit for converting each of the output signals obtained from the sensor circuit via a common data line into a digital output signal, A signal processing circuit that receives the output of the sensor circuit and generates the control signal that controls the calibration circuit, and the signal processing circuit compares the output of the sensor circuit with the calibration reference signal. The surface shape recognition sensor device, which is configured by the comparison circuit that supplies the difference output to the calibration circuit, and the output of the signal processing circuit is output to the calibration circuit through a control line. . 6. The surface shape recognition sensor device according to claim 1, further comprising a conversion circuit that converts each of the output signals obtained from the sensor circuit via a common data line into a digital output signal. And a signal processing circuit for generating the control signal for controlling the calibration circuit by signal-processing the output from the sensor circuit, wherein the signal processing circuit outputs the sensor circuit and the calibration reference signal. A comparison circuit for comparing and supplying the difference output to the calibration circuit;
And a holding circuit that holds the output of the comparison circuit, wherein the output of the signal processing circuit is output as the control signal to the corresponding calibration circuit via a common data line. Recognition sensor device. 7. The surface shape recognition sensor device according to claim 2, further comprising a conversion circuit that converts each of the output signals obtained from the sensor circuit via a common data line into a digital output signal. In addition to the calibration circuit, the output signal level correction circuit includes a comparison circuit that compares the output of the sensor circuit with the calibration reference signal and supplies the difference output to the calibration circuit. Characteristic surface shape recognition sensor device. 8. The surface shape recognition sensor device according to claim 1, wherein each of the sensor circuits converts an output signal corresponding to an amount of electricity from a corresponding detection element into a signal that changes in a time axis direction-time. A sensor circuit with a conversion function, the comparison circuit compares the voltage-time conversion signal that is the output of the sensor circuit and the calibration reference signal, and the difference signal to the calibration circuit as the control signal. A surface shape recognition sensor device characterized by being a time signal comparison circuit for outputting. 9. The surface shape recognition sensor device according to claim 8, further comprising a conversion circuit for converting an output of each of the sensor circuits into a digital output signal via a common data line. Shape recognition sensor device. 10. The surface shape recognition sensor device according to claim 1, wherein the calibration circuit is updated by a load circuit having at least one load element connected to the sensor circuit, and the control signal. A surface shape recognition sensor device comprising: a memory circuit that controls connection of the load element to the sensor circuit based on stored contents. 11. The surface shape recognition sensor device according to claim 1, wherein the calibration circuit is updated by a load circuit having at least one load element connected to the sensor circuit, and the control signal. A surface shape recognition sensor device comprising: a shift register that controls connection of the load element to the sensor circuit based on stored contents. 12. The surface shape recognition sensor device according to claim 1, wherein the calibration circuit is updated by a load circuit having at least one load element connected to the sensor circuit, and the control signal. A surface shape recognition sensor device, comprising: a counter circuit that controls connection of the load element to the sensor circuit based on stored contents. 13. The surface shape recognition sensor device according to claim 1, wherein the calibration circuit has a plurality of load elements, a storage capacity equal to the number of these load elements, and a memory updated by the control signal. A surface shape recognition sensor device including a load circuit including a switch for selectively connecting and controlling each load element to the sensor circuit based on contents. 14. The surface shape recognition sensor device according to claim 1, wherein the calibration circuit includes a load circuit including a plurality of load elements, and the load elements have the same storage capacity as the number of the load elements. A surface shape recognition sensor device comprising an element which is controlled to be switched between an active state and an inactive state based on the stored content updated by the control signal. 15. The surface shape recognition sensor device according to claim 10, wherein the memory circuit comprises an SRAM.