KR101804860B1 - Infrared Detector - Google Patents

Abstract

An infrared detector in which microbolometer cells to output a sensing signal by sensing infrared rays are arranged with an array shape according to the present invention includes a microbolometer array including a group in which at least two columns are grouped; a skimming cell connected to all the microbolometer cells included in the group and generating a skimming signal for removing a background component of the sensing signal; and a detection circuit connected to all the microbolometer cells included in the group and detecting a difference between the sensing signal and the skimming signal. Accordingly, the present invention can reduce power consumption and improve infrared ray detection performance.

Description

Infrared Detector [0002]

The present invention relates to an infrared detector.

Infrared detectors are generally divided into light-based detectors and open-half detectors that respond to far-infrared radiation. The thermal detector uses a thermal sensor array to generate a temperature image of the object. An apparatus for collecting the black body radiation energy emitted from a subject and obtaining a temperature image 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 has been made in view of the above problems, and it is an object of the present invention to provide an infrared detector capable of improving infrared detection performance by reducing FPN characteristics by sharing a detection circuit.

It is another object of the present invention to provide an infrared detector that reduces power consumption by sharing a detection circuit.

The technical objects to be achieved by the present invention are not limited to the technical matters mentioned above, 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 .

According to an embodiment of the present invention, an infrared detector having an array of microvolume cells for detecting infrared rays and outputting a detection signal includes a microbolometer array including at least two groups of grouped columns; A skimming cell connected to the microbolometer cells included in the group and generating a skimming signal for removing a background component of the sensing signal; And a detection circuit connected to the microbolometer cells included in the group and detecting a difference between the sensing signal and the skimming signal.

According to another aspect of the present invention, there is provided an infrared detector in which microvolume cells arranged in an array form for detecting infrared rays and outputting a detection signal include a microbolometer array including at least two groups of grouped rows; A skimming cell connected to the microbolometer cells included in the group and generating a skimming signal for removing a background component of the sensing signal; And a detection circuit connected to the microbolometer cells included in the group and detecting a difference between the sensing signal and the skimming signal. The infrared detector includes a driving circuit for driving the microbolometer cells included in the group And a driving signal generator for generating and providing a signal.

The drive signal generator may generate a drive signal that sequentially drives the microbolometer cells included in the group along the columns of the array.

The drive signal generator may generate a drive signal that sequentially drives the microvolumometer cells included in the group along the rows of the array.

The skimming cell may be a single cell or an array of a plurality of cells.

The skimming cell may include a worm cell or a cold cell.

The sensing circuit may include a capacitive trans-impedance amplifier (CTIA).

As described above, according to the infrared detector according to the embodiments of the present invention, the microbolometer array is divided into a plurality of groups, and the microbolometer cells belonging to each of the plurality of groups share one detection circuit with one skimming cell The area of the infrared detector is reduced, and the power consumption is accordingly reduced.

Specifically, according to the infrared detector according to the embodiments of the present invention, it is possible to reduce the FPN (Fixed Pattern Noise) by sharing the detection circuit, reduce the area of the detection circuit, and reduce the power consumption of the detection circuit By sharing the skimming cell, the nonuniformity of the skimming cell can be reduced and the low frequency noise generated in the skimming cell can be reduced.

In addition, the microbolometer cells in each group of the microbolometer array have the same fixed pattern noise due to the detection circuit and the skimming-cell, thereby reducing the time and cost spent in the non-uniformity correction (NUC) do. Further, even when the resolutions of the infrared detectors are different, the previously designed detection circuit can be reused.

That is, the detection circuit shared by a single row (or column) in H-by-V resolution and the detection circuit shared by n rows (or columns) in H / n-by-H / Therefore, error detection and correction of the infrared ray detector is facilitated.

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 microbolometer array.
FIG. 3 illustrates an infrared detector including a microbolometer array according to an embodiment of the present invention.
4 illustrates an infrared detector including a microbolometer array according to another embodiment of the present invention.
5 illustrates an infrared detector including a microbolometer array according to another embodiment of the present invention.
Fig. 6 shows an example of a circuit diagram of the infrared ray detector of Fig.
FIGS. 7A and 7B are diagrams illustrating a reading order of microvolumometer cells according to embodiments of the present invention.

The present invention will now be described in detail with reference to the accompanying drawings, which show specific embodiments in which the present invention may be practiced. For a specific embodiment shown in the accompanying drawings, those skilled in the art will be described in detail so as to be sufficient for practicing the present invention. Other embodiments than the particular embodiment need not be mutually exclusive but different from each other. It is to be understood that the following detailed description is not to be taken in a limiting sense.

The detailed description of the specific embodiments shown in the accompanying drawings is read in conjunction with the accompanying drawings, which are considered a part of the description of the entire invention. The reference to direction or orientation is for convenience of description only and is not intended to limit the scope of the invention in any way.

Specifically, terms indicating positions such as "lower, upper, horizontal, vertical, upper, lower, upper, lower, upper, lower ", or their derivatives (e.g.," horizontally, Etc.) should be understood with reference to both the drawings and the associated description. In particular, such a peer is merely for convenience of description and does not require that the apparatus of the present invention be constructed or operated in a specific direction.

It should also be understood that the term " attached, attached, connected, connected, interconnected ", or the like, refers to a state in which the individual components are directly or indirectly attached, And it should be understood as a term that encompasses not only a movably attached, connected, fixed state but also a non-movable state.

1 is a basic block diagram of a signal detection circuit (ROIC) of a microbolometer-based infrared detector. The microbolometer-based infrared detector may be configured to include a microbolometer cell 10, a skimming cell 20, and a detection circuit 30. The detection circuit 30 may include an integrator. In the following description, the detection circuit 30 may be referred to as 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 skimming cell 20 may also comprise a second source follower 21 and a reference microbolometer 22. The second microbolometer 22 does not react to the remote temperature signal and the current Ir flowing through the second microbolometer 22 may have a fixed value independent of the remote temperature signal. In addition, the skimming cell 20 may 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 microbolometer cell 10 and the current Ir flowing in the skimming 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 skimming 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-Vgsn is the voltage across both ends of the microbolometer 12, and Vr = Vskim-Vgsk-Vgsp And is a voltage across both ends of the reference microbolometer 22.

Here, Vfid is a DC voltage commonly applied to the first source follower 11 of the microvolume cell 10, and Vskim-Vgsk is a DC voltage applied commonly to the second source follower 21 of the skimming cell 20, Voltage.

In FIG. 1, a first source follower 11 is an NMOS transistor and a second source follower 21 is a PMOS transistor. Vgsn is the voltage across the gate and source of the NMOS transistor 11, and Vgsp is the voltage across the gate and 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 VFID, VEB and VSKIM.

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.

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. An infrared ray detector having the above-described configuration will be described with reference to Fig.

Figure 2 shows an infrared detector including a microbolometer array.

More specifically, as shown in FIG. 2, one detection circuit 300 is correspondingly connected to each of a plurality of columns in the microbolometer array. In other words, the microbolometers in each column share a single detection circuit 300. In addition, the microbolometers in each column may share a single skimming cell 200.

The infrared detector having such a configuration requires the detection circuit 300 and the skimming cell 200 for each column, which increases the circuit area and power consumption. Therefore, the cost of the infrared detector increases.

FIG. 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 microbolometer 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 of 2 or more) (NXM array). For example, the infrared detector may comprise a microbolometer focal plane array (FPA) composed of a plurality of rows / columns.

These microbolometer arrays are grouped into groups 400-1, 400-2, ..., 400-I each having at least two columns. In FIG. 3, each of the plurality of groups 400-1, 400-2, ..., and 400-I is shown to include two columns, but the present invention is not limited thereto. Each group may include a predetermined number of columns depending on the design conditions and applications of the infrared detector.

According to another embodiment of the present invention, each of the plurality of groups may include at least two rows.

4 illustrates an infrared detector including a microbolometer array according to another embodiment of the present invention.

Referring to FIG. 4, the microbolometer array is grouped into groups 500-1, 500-2,..., 500-J each having at least two rows. In FIG. 4, each of the plurality of groups 500-1, 500-2,..., 500-J is shown to include two rows, but the present invention is not limited thereto. Each group may include a predetermined number of rows, depending on the design conditions and use of the infrared detector. Also, an infrared detector may correspond to each of the one or more groups and may remove background components of the sensed signals from each group A skimming cell (200) for generating a skimming signal for detecting a difference between the detection signal and the skimming signal, the detection signal corresponding to each of the one or more groups and being connected to all microbolometer cells of each group, Circuit 300. < / RTI >

More specifically, the infrared detector includes a skimming cell 200 and a detection circuit 300 for each group. In other words, the microblogging cells belonging to one group share one skimming cell 200 and one detection circuit 300. The skimming cell 200 is connected to all the microbolometer cells 100 included in each group. The skimming cell 200 generates a skimming signal to remove the background component of the sensing signal generated from the microbolometer cell.

As the skimming cell 200, a cold cell having no self-heating effect or a warm cell capable of self-heating can be used.

A cold cell is a cell that has almost no self-heating with a thermal conductivity of almost infinite, and there is a thermal illicit synthesis with a sensing cell with self-heating, but such a problem can be solved by using a worm cell.

The worm cell is manufactured using the same process as the sensing cell, has the same body part as the sensing cell, but has the same electrical characteristics, but is a type of skimming cell that is capable of arbitrarily adjusting the thermal conductivity by creating an additional heat transfer path in the leg part. Using a worm cell, the mean temperature rise of the self-heated sensing cell during the sensing time can be offset by the normal worm cell temperature rise. Such a warm-cell capable of self-heating cancellation has the following characteristics.

(1) Electrical matching with the microbolometer cell 100 with respect to electrical resistance value and current flow is excellent.

(2) thermal compatibility with the microbolometer cell 100 with respect to heat flow in the body part is excellent.

(3) 1 / f noise is small and reactivity to infrared rays is low.

(4) The magnetic heating effect with respect to the microbolometer cell 100 can be canceled by arbitrarily adjusting the amount of magnetic heating by adjusting the thermal conductivity in a predetermined range.

In addition, the detection circuit 300 is connected to all the microbolometer cells 100 included in each group. The microvolume cells 100 of each group are read, i.e. sensed, and integrated through the connected detection circuit 300. For example, one of the groups of microvolume cells 100 in the first time period is read through the detection circuit 300, and the next microbolometer cell 100 of each group of microbolometer cells 100 100) can be read out through the detection circuit 300. In this manner, the microbolometer cells 100 belonging to a plurality of groups are sequentially read. That is, the microbolometer cells 100 included in one group can be read one at a time.

Although the microbolometer cells belonging to each group share one skimming cell in FIGS. 3 and 4, they may share two or more skimming cells. For example, the skimming cell may be comprised of a single cell or an array of a plurality of cells. In addition, the type of cells used in the skimming cell 300 may include a worm cell or a cold cell.

Although not shown in FIGS. 3 and 4, the infrared detector may further include a drive signal generator for generating and supplying a drive signal for driving the micro-ballpoint cell to each of the one or more groups.

In this manner, the microbolometer array is divided into a plurality of groups, and the microbolometer cells belonging to each of the plurality of groups are configured to share one detection circuit 300 and one skimming cell 200, thereby reducing the area of the infrared detector , And the power consumption is accordingly reduced.

Also, FPN (Fixed Pattern Noise) due to process / substrate temperature / self-heating variation (PTS) is reduced as the area of the infrared detector decreases.

On the other hand, each of the plurality of groups may be modularized including the detection circuit and the skimming cell connected to each group. Accordingly, an infrared detector having a small array size may use one group of microvolomic cells as one detection component, and an infrared detector having a large array size may use a plurality of groups as one detection component.

5 illustrates an infrared detector including a microbolometer array according to another embodiment of the present invention. An infrared detector according to an embodiment of the present invention includes a microbolometer array in which a microbolometer cell for sensing an infrared ray and outputting a signal is arranged in N rows and N rows (NXM, where N and M are integers equal to or larger than 2) NXM arrays). The present embodiment includes one skimming cell 200 and one detection circuit 300 for the N X M microbolometer array. That is, the infrared detector of FIG. 5 includes an array of microbolometer cells grouped into one group and one skimming cell 200 and one detection circuit 300 connected to the one group. The specific configuration of the infrared ray detector of Fig. 5 is shown in Fig.

Fig. 6 shows an example of a circuit diagram of the infrared ray detector of Fig.

Referring to FIG. 6, a plurality of columns of the microbolometer array share one skimming cell 200 and one detection circuit 300. As described above, since the microvolume cells 100 of the microbolometer array share one skimming cell 200 and one detection circuit 300, they must be sequentially read. The microvolume cells 100 of the microbolometer array are driven by a drive signal comprising a column switching signal CSEL and a row switching signal RSEL. To this end, although not shown in FIGS. 5 and 6, the infrared detector may further include a drive signal generator for generating a drive signal. The drive signal may be provided to each microbolometer cell via a logic circuit or logic component not shown.

The driving signal generator generates driving signals for sequentially reading the microbolometer cells 100 included in each group. If a plurality of columns of the microbolometer array 400 are grouped into a plurality of groups instead of one, driving signals for the respective groups can be simultaneously generated.

The drive signal generator may generate a drive signal based on the order of driving the microbolometer cells 100 belonging to each group.

FIGS. 7A and 7B are diagrams illustrating a reading order of microvolumometer cells according to embodiments of the present invention.

As shown in FIG. 7A, according to one embodiment, the microbolometer arrays in the first column are read first and the microcolumns in the second column are read out. Thus, the microvolume cells in the first column and the first row are read first, and the microvolume cells in the first column and the second row are read.

In this case, the driving signal generator generates driving signals for sequentially driving the microbolometer cells included in each group according to the columns of the array, and provides the driving signals to the groups. As shown in FIG. 7B, according to another embodiment, the microbolometer arrays are read in such a manner that the microbolometer cells belonging to the first row are read first and the microcells of the second row are read. Thus, the microvolume cells of the first column and the first row are read first, and the microvolume cells of the second column and the first row are read. The driving signal generator generates driving signals for sequentially driving the microbolometer cells included in the respective groups according to the rows, and provides the driving signals to the groups.

As described above, according to the infrared detector according to the embodiments of the present invention, the microbolometer array is divided into a plurality of groups, and the microbolometer cells belonging to each of the plurality of groups are connected to one skimming cell 200 and one detection circuit 300 ), The area of the infrared detector becomes small, and the power consumption becomes small accordingly.

Further, according to the infrared ray detector according to the embodiments of the present invention, the area of the detection circuit can be reduced by sharing the detection circuit, the power consumption of the detection circuit can be reduced, and the nonuniformity of the skimming cell can be reduced And the low frequency noise generated in the skimming cell can be reduced.

In addition, the microbolometer cells in each group of the microbolometer array have the same fixed pattern noise due to the detection circuit and the skimming-cell, thereby reducing the time and cost spent in the non-uniformity correction (NUC) do. Further, even when the resolutions of the infrared detectors are different, the previously designed detection circuit can be reused.

That is, the detection circuit shared by a single row (or column) in H-by-V resolution and the detection circuit shared by n rows (or columns) in H / n-by-H / Therefore, error detection and correction of the infrared ray detector is facilitated.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is to be understood that the invention is not limited to the disclosed embodiments, but, on the contrary, It will be understood that various modifications and applications are possible. For example, each component specifically shown in the embodiments can be modified and implemented. It is to be understood that all changes and modifications that come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein.

100: Microbolometer cell
200: Skimming cell
300: Detection circuit
400: Microbolometer array

Claims (8)

1. An infrared detector in which microbolometer cells for detecting an infrared ray and outputting a detection signal are arranged in an array,
A microbolometer array including a plurality of groups each including at least two microbolometer cells disposed in the same column and at least two microbolometer cells disposed in the same row;
A plurality of skimming cells connected in parallel to the microbolometer cells included in each group of the plurality of groups and generating a skimming signal for removing a background component of the detection signal;
A plurality of detection circuits connected in parallel to the microbolometer cells included in each group of the plurality of groups and detecting a difference between the sense signal and the skimming signal; And
And a driving signal generator for generating driving signals for sequentially driving the microbolometer cells included in each group of the plurality of groups,
The microbolometer cells of each group are connected to each other, all the microbolometer cells arranged in the same column or row are connected in parallel to each other,
Columns or rows of microvolume cells connected in parallel in each group are connected in parallel and connected to one of the plurality of skimming cells and one of the plurality of detection circuits,
Wherein the driving signal generator generates driving signals for sequentially driving the microbolometer cells included in each group along at least two columns or rows of the respective groups,
Wherein the driving signal comprises a column switching signal and a row switching signal.
delete delete delete delete The method according to claim 1,
Wherein the skimming cell comprises a single cell or an array of a plurality of cells.
The method according to claim 1,
Wherein the skimming cell includes a worm cell or a cold cell.
The method according to claim 1,
Wherein the detection circuit comprises a capacitive trans-impedance amplifier (CTIA).

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