KR101563475B1 - Infrared Detector - Google Patents

Abstract

An infrared detector of the present invention includes a cell array in which a microvolume cell for sensing an infrared ray and outputting a current signal is arranged in N rows and M rows (NxM, where N and M are integers of 2 or more); And an integrator for receiving and integrating the current signal, wherein the current signal can be simultaneously read from at least two microbolometer cells included in one of the N columns, The current signal can be read through different integrators.

Description

Infrared Detector [0002]

The present invention relates to an infrared ray detector, and more particularly, to a technique capable of greatly reducing the complexity of a read circuit and calibration in an uncooled thermal image sensor using a microbolometer array.

Infrared detectors are broadly divided into light-based detectors and thermal detectors, which generally respond to far-infrared radiation. Thermal detectors can typically implement an imaging system to generate a temperature image of the object using a thermal sensor array. An apparatus that collects the blackbody radiation energy emitted from an object and obtains a temperature image of the object is called a Far-Infrared Thermal Imaging system.

Open half detectors are known to include bolometers, microbolometers, superconductors and thermocouples. When the far infrared rays in the 8 to 14 mu m band, which is black-body copied from all the objects, are focused on the microbolometer by the lens, the temperature of the microbolometer is raised or lowered, thereby changing the electrical resistance of the microbolometer. Accordingly, the temperature distribution of the target scene can be remotely imaged by using an array of microbolometer cells, that is, a microbolometer array.

Such a microbolometer array typically has a signal amplitude of less than 0.1%, but has a substrate temperature dependency of 2 to 3% per degree of substrate temperature, a process uniformity of several percent, Represents a signal change due to a circuit mismatch of several percent.

In addition, for the temperature change characteristics of the electrical resistor, it is necessary to measure the current flowing through the electrical resistor after applying the bias voltage, or measure the voltage across the resistor after applying the current bias. At this time, the temperature of the electrical resistor rises by joule-heating. This phenomenon is referred to as self-heating, which is irrelevant to far-infrared radiation to be detected and must be corrected.

As a result, the microbolometer array has FPN (Fixed Pattern Noise) characteristics due to process / substrate temperature / self-heating variation (PTS).

Therefore, various studies have been made on techniques for improving the infrared detection performance by reducing FPN characteristics in an infrared detector including a microbolometer array.

SUMMARY OF THE INVENTION The present invention is directed to provide an infrared detector capable of improving infrared detection performance by reducing FPN characteristics and improving SNR in an infrared detector including a microbolometer array.

The technical objects to be achieved by the present invention are not limited to the above-mentioned technical problems, and other technical subjects which are not mentioned can be clearly understood by those skilled in the art from the description of the present invention .

An infrared detector according to an embodiment of the present invention includes a cell array in which a microvolume cell for sensing an infrared ray and outputting a current signal is arranged in N rows and M rows (NxM, where N and M are integers equal to or larger than 2); And an integrator for receiving and integrating the current signal, wherein the current signal can be simultaneously read from at least two microbolometer cells included in one of the N columns, The current signal can be read through different integrators.

The infrared detector according to the embodiment of the present invention further includes a controller for setting the integration time for receiving and integrating the current signal from the microbolometer cell in the integrator and transmitting a control signal indicating the integral time to the integrating circuit, (M is an integer equal to or greater than 2 and equal to or less than M) integrators for each of the N columns, and the integrating circuit integrates the current signal from at most m microbolometer cells Can be simultaneously received by the m integrators.

According to the embodiments of the present invention, it is possible to provide an infrared detector capable of reducing the influence of FPN characteristics, in particular, self heating, in an infrared detector including a microbolometer array, thereby improving the infrared detection performance and greatly reducing the dynamic range of the readout circuit .

In addition, according to the embodiment of the present invention, it is possible to provide an infrared detector capable of simultaneously reading microbolometer cells in two or more rows in a microbolometer array.

According to the embodiments of the present invention, it is possible to provide an infrared detector capable of linearly adjusting an integration time within which a signal from a microbolometer cell can be integrated in a microbolometer array within a predetermined range.

Further, according to the embodiments of the present invention, it is possible to provide an infrared detector capable of reducing an offset due to self heating of a microbolometer cell.

Further, according to the embodiment of the present invention, it is possible to provide an infrared ray detector capable of effectively reducing the influence of thermal noise.

Further, according to the embodiment of the present invention, it is possible to provide an infrared detector having an improved SNR.

Further, according to the embodiment of the present invention, it is possible to provide an infrared ray detector having a high infrared ray detection efficiency.

1 is a basic block diagram of a signal detection circuit (ROIC) of a microbolometer-based infrared detector.
Figure 2 shows an infrared detector including a conventional microbolometer array.
FIG. 3 illustrates an infrared detector including a microbolometer array according to an embodiment of the present invention.
4 is a block diagram of an infrared detector according to an embodiment of the present invention.
FIG. 5 shows control signals generated in the controller 600 according to an embodiment of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a detailed description of preferred embodiments of the present invention will be given with reference to the accompanying drawings. However, the embodiments of the present invention may be modified into various other forms, and the scope of the present invention is not limited to the embodiments described below. The shape and the size of the elements in the drawings may be exaggerated for clarity of explanation and the same reference numerals are used for the same elements and the same elements are denoted by the same quote symbols as possible even if they are displayed on different drawings Should be. In the following description, well-known functions or constructions are not described in detail to avoid unnecessarily obscuring the subject matter of the present invention.

Generally, in the case of a microbolometer array included in an infrared detector, the resistance value of the microbolometer array usually varies by several ten percent, while the minimum signal level due to the far-infrared rays from the object has a resistance variation of about 0.001% Requires about 15 bits or more of dynamic range. The lower 8 bits indicate the signal level and the upper 7 bits are used to remove the FPN. When the readout circuit is constructed as described above, the cost efficiency is high, but it is very difficult to implement the CMOS (Complementary Metal-Oxide Semiconductor) technology having limited performance. Therefore, the following measures can be used to reduce the burden of the required dynamic range.

First, a skimming technique is used to eliminate unnecessary DC bias by using a reference microbolometer cell.

Second, the temperature of the substrate is maintained at a constant temperature by using a thermo-electric cooler.

However, even if the first skimming technique is used, additional Offset / Gain calibration may be performed due to residual offset and nonlinearity due to mismatch between the microvolume cell and the reference microvolume cell. ) Is required. The following two methods are used to solve this problem.

i) adjusting the V _FID , V _EB and V _SKIM on the analog circuit to correct the offset / gain error, and / or

ii) After the analog / digital data converter (ADC), digital correction is applied using an external memory.

Therefore, in the present invention i) performs a coarse trimming such that the analog circuit is not saturated and operates in the linear region, ii) the non-uniformity correction (NUC) for correcting the FPN between the thermal sensors, The first purpose is to make it more convenient to carry out.

In addition, a 3-dimensional calibration technique is required to correct the FPN due to a change in the general PTS. However, when the present invention is applied, a 2-dimensional calibration technique can be used to solve the FPN. Time and material resources consumed during the calibration process can be greatly reduced.

Also, in order to measure a very small change in resistance of about 0.001% generated by a far infrared ray signal in a microbolometer, the SNR (Singnal to Noise Ratio) of the readout circuit must be very large. For this purpose, It is preferable to lengthen the detection time t _sense . However, the detection time (t _sense ) is restricted in order to satisfy the frame rate required in the image system. For example, in the case of an image satisfying 30 fps at a VGA resolution (640 × 480), even if parallel reading is performed for each column, SNR is increased because it is limited to t _sense = 1 / (30 × 480) = 69 μsec or less A constraint is generated. Therefore, a second object of the present invention is to alleviate the constraint of SNR resulting from this limited detection time. Hereinafter, the present invention will be described in detail in order to achieve these objects.

In order to reduce the unnecessary dynamic range of the signal detection circuit (ROIC) by the fixed pattern noise (FPN) of the infrared detector, skimming for eliminating the unnecessary DC signal is basically performed. This technique is described below with reference to FIG.

1 is a basic block diagram of a signal detection circuit (ROIC) of a microbolometer-based infrared detector. The microbolometer-based infrared detector may comprise a microbolometer cell 10, a reference microbolometer cell 20 and an integrator 30.

As shown in FIG. 1, the microbolometer cell 10 may include a first source follower 11, a microbolometer 12, and a first switch 13. Likewise, the reference microbolometer cell 20 may also comprise a second source follower 21 and a reference microbolometer 22. The reference microbolometer 22 does not react to the remote temperature signal and the current Ir flowing in the reference microbolometer 22 can have a fixed value independent of the remote temperature signal. In addition, the reference microbolometer cell 20 can share cells located in the same row or column of the microbolometer array.

In FIG. 1, the integrator 30 may be a capacitive trans-impedance amplifier (CTIA). Through the integrator 30, the current signal input to the integrator 30 can be converted into a voltage signal, amplified, and output as Vout. The signal input to the integrator 30 will be described below. The capacitor 31 is coupled between the input and output of the integrator 30, that is, the feedback path. The gain of the output of the integrator 30 can be controlled according to the size of the capacitor 31. [ The integrator 30 performs the current-to-voltage conversion by accumulating the charge on the capacitor 31. The integrator 30 may be further provided with a reset switch (not shown) to reset the current to voltage conversion performed by the integrator 30.

Although not shown in FIG. 1, the signal output from the integrator 30 is transmitted to an amplifier, a multiplexer, and / or an analog-to-digital converter (ADC) A signal can be output. At this time, an unnecessary DC signal may be removed from the integrator 30 to reduce the dynamic range of the circuits including the ADC at the rear end of the integrator 30.

That is, only the difference signal Ir-Ia between the current Ia flowing in the microvolume cell 10 and the current Ir flowing in the reference microbolometer cell 20 can be input to the integrator 30. Preferably, the difference signal (Ir-Ia) may represent a signal variation amount due to an infrared object in the microbolometer cell (10). Therefore, the microbolometer cell 10 and the reference microbolometer cell 20 can be designed to have the same electrical characteristics and the like.

The signal Iout at the point A in Fig. 1 can be expressed as follows.

Iout = Ia-Ir = Va / Ra-Vr / Rr Equation (1)

Here, Ra and Rr are the electrical resistance values of the microbolometer 12 and the reference microbolometer 22, respectively, and Va = Vfid-Vthn, which is the voltage across the microbolometer 12, and Vr = Vskim-Veb-Vthp And is a voltage across both ends of the reference microbolometer 22.

Here, Vfid is a DC voltage commonly applied to the source follower 11 of the microvolume cell 10, and Vskim-Veb is a DC voltage commonly applied to the source follower 21 of the reference microvolume cell 20 .

In FIG. 1, a first source follower 11 is an NMOS transistor and a second source follower 21 is a PMOS transistor. Vthn denotes a voltage applied between the gate and the source of the NMOS transistor 11 and Vthp denotes a voltage between the gate and the source of the PMOS transistor 21. [

Skimming refers to reducing the dynamic range that is unnecessarily consumed by removing the DC bias as shown in equation (1). In addition, calibration due to mismatch between microvolometer and reference microbolometer is required, which can be calibrated by adjusting V _FID , V _EB and V _SKIM .

Further, in order to reduce the FPN different from the temperature of the substrate including the microbolometer array, the temperature of the substrate can be fixed to a predetermined value by using a thermoelectric cooler (TEC). However, such a thermoelectric cooler consumes a lot of electric power for temperature control while increasing the cost in manufacturing the infrared detector.

Therefore, in the present invention, the temperature dependency is reduced without using the thermoelectric cooler. In order to enable such an operation, it can be seen from Equation (1) that the following two conditions must be satisfied.

&Lt; Va / Ra > = < Vr / Rr &

< d (Va / Ra) / dT > = &

Where the symbol (< ... >) represents the mean value during the integration time of the integrator 30, i.e. during the sensing time tsense of the microvolume cell 10. d / dT means the differential with respect to temperature.

The temperature of the microbolometer 12 during the sensing time tsense can be obtained from the following equation.

수학식 (4)

Equation (4)

Here, Cth represents the heat capacity of the microbolometer 12. From the equation (4), the following equation can be derived.

수학식(5)

Equation (5)

T-To is the temperature change value during the sensing time (tsense). Similarly, for the reference microbolometer 22, the following equation can be derived.

수학식(6)

Equation (6)

Here, Rth represents the thermal resistance of the reference microbolometer 22.

The average temperature change amount of the microbolometer 12 and the average temperature change amount of the reference microbolometer 22 must be the same during the sensing time tsense in order to always satisfy the expressions (2) and (3). From this, it is necessary to satisfy the following three conditions.

i) Va = Vr

ii) Ra = Rr

iii) Cth * Rth = tsense / 2

Here, it is assumed that the temperature of Ra during the self heating increases linearly with time and the temperature of Rr is in a steady state.

The microbolometer is a resistive infrared detector, and the electrical energy applied during the infrared detection process is consumed by the resistor and converted into thermal energy. That is, during the infrared detection process, the temperature of the microbolometer rises itself and is referred to as self-heating.

Therefore, since the microbolometer needs time to cool the elevated temperature after the infrared ray detection process, several microbolometer cells can share a read-out integrated circuit (ROIC) in order to increase the efficiency of the hardware.

As described above, a process variation, a temperature variation, and an error due to a difference in self-heating between a micro-bore meter and a reference micro-bore meter at the time of manufacturing the micro-bore meter 12 and the reference micro- The unnecessary offset DC signal in the current signal input to the integrator 30 can not be sufficiently removed. As a result, the dynamic range of the integrator 30 may be reduced and the circuit may be saturated at the time of signal amplification. Further, there arises a problem that the dynamic range of the ADC must be increased later.

Preferably by matching the average temperature change amount through the self heating of the microbolometer 12 and the average temperature change amount of the reference microbolometer 22 during the detection time tsense equally to each other, It is possible to efficiently remove an unnecessary DC signal.

However, in the case of reading the microbolometer included in the microbolometer array as in the conventional technique, the temperature change amount through the self-heating of the microbolometer 12 and the temperature change amount of the reference microbolometer 22 during the detection time tsense There is a difficulty in matching the same to each other.

Figure 2 shows an infrared detector including a conventional microbolometer array. 2, the infrared detector comprises a cell array arranged in the form of N rows and M rows (N X M, where N and M are integers greater than or equal to 2); And an integrator 30 for each of the N columns.

The conventional infrared detector has one integrator 30 in one column, and the integrator 30 is connected to all microbolometer cells 10 included in each column. During a particular time interval, only the microbolometer cells 10 in a row are read, i.e. sensed and integrated, via respective integrators 30. For example, during the first time interval, N microbolometer cells 10 included in the first row are read through respective integrators 30, and during the subsequent second time interval, N microbolometer cells 10 included in the second row (10) can be read through each integrator (30). This may be done up to the last M rows and then repeat from the first row. The switch 13 included in each cell 10 is configured to close so that it can send a signal to the integrator 30 only during its sensing time.

However, 30 frames per second is required to allow N X M arrays to be used for video graphics as a 640 X 480 array. Therefore, there is a need to scan 30 times repeatedly for 480 rows per second. In this case, the scan time allocated to one microbolometer cell 10 is approximately 69 mu s.

At this time, the self-heating time of the conventional microbolometer 12 is 34 μs, but the thermal time constant of the reference microbolometer 22 is generally much larger than this. For example, the thermal time constant of the reference microbolometer 22 may be approximately 50 μs. In this case, a difference occurs between the average temperature change amount through self-heating of the microbolometer 12 and the temperature change amount of the reference microbolometer 22 during the detection time tsense.

At this time, if the sensing time for sensing one microbolometer cell 10 is increased to a long time, for example, 100 microseconds, two temperature variations can be matched. However, according to the reading method as shown in FIG. 2, it is impossible to increase the sensing time tsense while making use of the characteristics of a VGA (Video Graphic Array). Moreover, this is more so when the demand for current high definition (HD) video becomes large. For HD imaging, more pixels than 640 X 480 are required, which means that the number of microbolometer cells 10 to be scanned per second increases. Therefore, the detection time can not be reduced any more.

Accordingly, in the embodiment of the present invention, an infrared detector capable of increasing the time for reading a signal from one microbolometer cell 10, that is, the detection time, is provided.

3 illustrates an infrared detector including a microbolometer array according to an embodiment of the present invention. An infrared detector according to an embodiment of the present invention includes a micro array array in which a microbolometer cell for sensing an infrared ray and outputting a current signal is arranged in an array of N columns and M rows (NXM, where N and M are integers of 2 or more) NXM array); And an integrator (30) for each of the N columns, wherein a current signal from the microvolume cells (10) contained in two of the M rows is applied to a corresponding integrator (30).

Although it is shown that two integrators 30 are connected to one n-th row in Fig. 3, this is only an example, and m integrators 30 may be included in each column. Here, m may be an integer of 2 or more and M or less. Hereinafter, m will be described as an example for the sake of understanding.

3 and the following description are based on only one column, for example, the n-th column. However, when the microbolometer cell 10 in a specific row of the n-th column is read, the microbolometer cell 10 included in the N- (10) is read through each of the integrators (30).

The integrator 30 that receives and integrates the current signal of the first column may include a first integrator 33_1 and a second integrator 33_2. At this time, the first integrator 33_1 includes the first row, the third row, The second integrator 33_2 can receive the current signal from the microbolometer cell 10 included in the second row, the fourth row ... The current signal from the microbolometer cell 10 included in the microbolometer cell 10 can be input.

In this case, in FIG. 3, it is also possible to read the current signal from the microbolometer cell 10 included in one row for each predetermined time interval, and to read the current signal from the microbolometer cell 10 included in two rows It is also possible to simultaneously read the current signal.

For example, when it is set to read the current signal from the microbolometer cell 10 included in one row for each predetermined time interval, as in the case of FIG. 2, in the first time period, Can be read through the first integrator 33_1 and the current signal from the cell 10 included in the second row can be read through the second integrator 33_2 during the subsequent second time period. This can be repeated from the first row after the third to Mth rows are performed. However, this is merely an example, and it is also possible to read the current signal from all the cells 10 in the first column in either the first integrator 33_1 or the second integrator 33_2. The first integrator 33_1 and the second integrator 33_2 are connected to all the cells 10 in the first column and are connected to the first integrator 33_1 or the second integrator 33_2 in accordance with the setting. Can be realized by blocking all transmission. At this time, in each cell 10, a signal is connected to a third switch (not shown) and a second integrator 33_2 branching from the first switch 13 and controlling signal connection to the first integrator 33_1, A fourth switch (not shown), which is connected to the first switch (not shown). That is, the fourth switch may be all open and the third switch may be all closed. Or vice versa.

In addition, according to the embodiment of the present invention, it is also possible to simultaneously read the current signal from the microbolometer cell 10 included in two rows for each predetermined time interval. For example, during a first time interval, the first integrator 33_1 reads the current signal from the cell 10 of the first row and the second integrator 33_2 reads the current signal from the cell 10 of the second row can do. During the following second time interval, the first integrator 33_1 reads the current signal from the cell 10 in the third row and the second integrator 33_2 reads the current signal from the cell 10 in the fourth row . This process is performed up to the Mth cell by two cells, and can be repeated from the first row. At this time, the connection of the first integrator 33_1 and the second integrator 33_2 is also connected to the cell 10 in all the rows through the opening and closing of the third switch (not shown) and the fourth switch (not shown) And no connection may be determined. In addition, the selection of the row in which the first integrator 33_1 and the second integrator 33_2 are connected and / or the cell to be simultaneously read may vary from embodiment to embodiment.

3, in the embodiment of the present invention, it is possible to read the current signal from the cell 10 included in two or more rows at the same time, but the integrator that reads the cell 10 included in one column It is not necessary to distinguish the drive signals applied to the microbolometer cell 10 to be read at the same time by including a plurality of the drive signals, and the decrease of the SNR caused by applying different drive signals can be prevented.

For example, as shown in FIG. 3, the infrared detector according to the embodiment of the present invention includes reference microbolometer cells 20_1 and 20_2 for outputting reference signals for the integrators 33_1 and 33_2 included in the column (n column) Respectively. For example, each of the integrators 33_1 and 33_2 may include a reference cell array arranged in N rows and m rows so as to have one reference microbolometer cell 20. 1, a current signal output from the microbolometer cell 10 included in the column and a corresponding reference microbolometer cell 20 positioned in the same column as the microbolometer cell 10 are connected to the respective integrators 30, The differential signal of the reference signal output from the differential amplifier 20 may be input. This is merely an example and any reference microbolometer cell 10 array can be used.

4 is a block diagram of an infrared detector according to an embodiment of the present invention. The infrared detector according to the embodiment of the present invention may further include the controller 600 as well as the N X M array 200 and the integrating circuit 300.

The controller 600 according to the embodiment of the present invention calculates the integration time for integrating the current signal from one microbolometer cell 10 through the integrator 30 at the time of sensing one microbolometer cell 10, And can transmit a control signal indicating the control signal to the integrating circuit 300.

In accordance with the control signal, the integrating circuit 300 can be configured to simultaneously receive the current signals from the m total number of microbolometer cells 10 for every column in the m integrators 30. [ Even if m integrators 30 are included in each column, the number of microbolometer cells 10 to be read at the same time can be set to m, but less than m.

FIG. 5 shows control signals generated in the controller 600 according to an embodiment of the present invention. When each row includes m integrators 30, a maximum of m control signals can be generated in the controller 600. [

In Figure 5, it is a timing plot when the microbolometer cells 10 located in two rows are read simultaneously. At the top, the clock of the controller is shown. The first control signal and the second control signal are respectively transmitted to the first integrator 33_1 and the second integrator 33_2 and the first control signal and the second control signal are transmitted to the microbolometer cell 10 of each row . The sensing time tsense during which the microbolometer cell 10 is integrated through the integrator 30 has a time width equal to a positive integral multiple k1 and k2 of the basic clock tclk of the controller 600. [ For example, the first sense signal tsense1 for the microvolume cell 10 through the first integrator 33_1 has a value of k1 X tclk and the second sense signal tsense1 for the microbolometer cell 10 through the second integrator 33_2 The second sensing signal tsense2 may have a value of k2 X tclk. Here, k1 and k2 are positive integers. However, when there is a detection signal of k3 or more, the remaining two signals may be zero.

Although k1 = k2 is shown in Fig. 5, k values for each sensing signal may be set differently. Therefore, the signal widths of tsense1 and tsense2 can be set differently. Also, according to the embodiment, the width of the detection signal for the microbolometer cell 10 detected through the same integrator can be set differently. For example, the widths of the sensing signals for the microbolometer cells 10 positioned in the first row and the second row detected through the first integrator 33_1 may be set to be different from each other.

The controller 600 may transmit the number of rows and rows to be driven simultaneously to the driving circuit 100 so that the microbolometer cell 10 can be driven accordingly. The infrared detector according to an embodiment of the present invention may further include a multiplexer 400 and an ADC 500. The ADC 500 receives the analog voltage signal from the multiplexer 400 that receives and processes the output voltage vout from the integrator 30 included in the integrating circuit 300 and converts the analog voltage signal into a digital voltage signal. The ADC 500 may include any combination of hardware and / or software that enables analog-to-digital conversion.

At this time, when the detection time or integration time for one microbolometer cell 10 in the case where only one row is read during a predetermined time interval is t, it is set to be read for two rows at the same time The detection time for the microvolume cell 10 of FIG. Similarly, the detection time for one microbolometer cell 10 when set to be read for m rows at the same time can be expressed in mt. Therefore, the detection time of one microbolometer cell 10 can be increased up to a maximum of m times when m integrators are combined for each column.

As described above, according to the embodiment of the present invention, the time at which one microbolometer cell 10 is read, that is, the sensing time or the integration time, can be set through the controller 600. [ At this time, the sensing time can be linearly controlled as needed. For example, even if the cells 10 in the m rows are simultaneously read, the detection time does not necessarily have to be set to mt, but can be set to have any time interval of mt or less.

3, according to an embodiment of the present invention, up to m integrators m already connected to one column at a chip level may be provided and may be used at a time according to the setting of the controller 600 The number of integrators can be designed to be variable. Thereafter, the number of integrators to be used for one column may be set to a maximum m according to the required sensing time through the controller 600, thereby controlling the operation of the integrating circuit 300. The number of rows that can be driven simultaneously at a time can be set via the controller 600 so that the integration circuit 300 and / or the NXM array 200 can be controlled by the number of integrators 30 and / (For example, opening and closing of the third switch and the fourth switch, etc.) from the cell 10 to the respective integrator 30.

According to an embodiment of the present invention, the sensing time and integration time for one microbolometer cell 10 is programmable via the controller 600. [ That is, the sensing time and the integration time can be digitally adjusted through the controller 600. [

According to the embodiment of the present invention, by adjusting the integration time for one microbolometer cell 10 as described above, the temperature variation due to self-heating in the microbolometer cell 10 and the temperature variation due to the reference microbolometer cell 20, The offset due to self-heating can be reduced.

In addition, by increasing the integration time for one microbolometer cell 10, it is possible to reduce noise due to thermal resistance, that is, thermal noise. In general, thermal noise is randomly changed over time, so it can be canceled if integration is performed for a sufficiently long period of time. More specifically, the thermal noise contained in the current signal from the microbolometer cell 10 is inversely proportional to the square root of the integration time tsense that integrates the current signal in the integrator 30. [ Therefore, by increasing the integration time tsense, the signal-to-noise ratio (SNR) can be improved in the integrator 30 integrated signal.

However, the longer the integration time, the more the gain of the integrator 30 increases and saturates at the time of amplification. In this case, the gain of the integrator 30 can be further adjusted by changing the capacitance of the capacitor 31 coupled to the integrator 30. [ That is, the smaller the capacitance of the capacitor 31, the larger the gain of the integrator 30, and the larger the capacitance, the smaller the gain of the integrator 30 is.

Accordingly, the controller 600 according to the embodiment of the present invention can control the magnitude of the offset according to the temperature change between the microvolume cell 10 and the reference microbolometer cell 20, the FPN according to the process change, The integration time tsense can be set in consideration of at least one of the FPN, the thermal noise generated in the microvolume cell 10, and the gain of the integrator 30.

In addition, the controller 600 may set gains for each of the N x m integrators included in the N columns. For example, different gains may be set for every N x m integrators.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is evident that many alternatives, modifications and variations will be apparent to those skilled in the art. will be. Therefore, it should be understood that the above-described embodiments are to be considered in all respects as illustrative and not restrictive, the scope of the invention being indicated by the appended claims rather than the foregoing description, It is intended that all changes and modifications derived from the equivalent concept be included within the scope of the present invention.

10: Microbolometer cell
20: Reference microbolometer cell
30: integrator

Claims (6)

A cell array in which a microbolometer cell for sensing an infrared ray and outputting a current signal is arranged in N rows and M rows (NXM, where N and M are integers equal to or larger than 2); And
And an integrator for receiving and integrating the current signal,
The current signal can be simultaneously read from at least two microbolometer cells included in one of the N columns,
Wherein the current signals read simultaneously are read through different integrators,
Infrared detector. The method according to claim 1,
Further comprising a controller for setting an integration time for integrating and receiving the current signal from the microbolometer cell in the integrator and for transmitting a control signal indicative thereof to the integration circuit,
Wherein the integrating circuit includes m integrators (m is an integer of 2 or more and M or less) for each of the N columns,
Wherein the integrating circuit is configured to be able to simultaneously receive the current signals from at most m number of microbolometer cells for each column in the m integrators in accordance with the control signal,
Infrared detector. 3. The method of claim 2,
The integrator is a capacitive trans-impedance amplifier (CTIA)
Wherein the controller is operable to set a gain for each of the N x m integrators included in the N columns,
Infrared detector. The method according to claim 2 or 3,
Further comprising a reference cell array in which reference microbolometer cells outputting a reference signal are arranged in N rows and m rows,
Wherein the reference microbolometer cell located in m rows included in one of the N columns corresponds to the m integrators included in the same column as the one column,
Wherein the integrator is supplied with the differential signal of the reference signal output from the corresponding reference microbolometer cell located in the same column as the microbolometer cell and the current signal output from the microbolometer cell included in the column,
Infrared detector. The method according to claim 2 or 3,
The integration time is:
At least one of an offset size according to a temperature change between the microbolometer cell and the reference microbolometer cell, an FPN according to a process change, an FPN according to a substrate temperature change, a thermal noise generated in the microbolometer cell, &Lt; / RTI &gt;
Infrared detector. 5. The method of claim 4,
The resistance of the microbolometer included in the microbolometer cell is equal to the resistance of the reference microbolometer included in the corresponding reference microbolometer cell located in the same column as the microbolometer cell,
And a voltage applied to both ends of the microbolometer is equal to a voltage applied to both ends of the reference microbolometer.
Infrared detector.

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