Image sensors for performing thermal reset, methods thereof, and devices including the same

A method of operating an image sensor includes: thermoelectrically cooling a pixel using a thermoelectric element having a thermoelectric-junction integrated to the pixel; and performing a photoelectric conversion operation using the thermoelectric element. An image sensor includes a pixel and a readout circuit. The pixel includes a thermoelectric element having a thermoelectric-junction, and the readout circuit is configured to control the pixel such that the thermoelectric element performs a thermoelectric-cooling operation and a photoelectric conversion operation.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority under 35 U.S.C. §119 to Korean Patent Application No. 10-2012-0137825, filed on Nov. 30, 2012, in the Korean Intellectual Property Office (KIPO), the entire contents of which are incorporated herein by reference.

BACKGROUND

Example embodiments of the present inventive concepts relate to image sensors, and more particularly to image sensors capable of performing a thermal reset using the Peltier effect, operation methods thereof, and devices including image sensors.

2. Description of Conventional Art

A CMOS image sensor is a solid-state image sensing device using a complementary metal-oxide semiconductor (CMOS). The CMOS image sensor has lower manufacturing costs and a smaller size than a charge coupled device (CCD) image sensor including a high voltage analog circuit, so that the CMOS image sensor consumes less power.

In recent years, as the CMOS image sensor has improved in performance, the CMOS image sensor has been widely used in various electronic products besides a portable electronic device such as a smart phone or a digital camera

SUMMARY

An example embodiment of the present inventive concepts is directed to a method of operating an image sensor. According to this example embodiment, the method includes: thermoelectrically cooling a pixel using a thermoelectric element having a thermoelectric junction integrated with the pixel; and performing a photo-electric conversion operation using the thermoelectric element. The thermoelectric-cooling may include Peltier-cooling the pixel using a Peltier-element having a Peltier-junction.

The Peltier-cooling may include: supplying a first voltage to an n-type semiconductor element forming the Peltier-junction during a reset operation; and supplying an operation voltage, which is higher than the first voltage, to a p-type semiconductor element forming the Peltier-junction while supplying the first voltage to the n-type semiconductor element during the reset operation.

The p-type semiconductor element may be a p-type phase change material, such as Ge2Sb2Te5. According to an example embodiment, the thermoelectric element may be formed through a front end of the line (FEOL) integration process. According to another example embodiment, the thermoelectric element may be formed after a back end of the line (BEOL) process.

According to at least some example embodiments, the method may further include: supplying the operation voltage to the p-type semiconductor element performing a photo-electric conversion during the photoelectric conversion operation. A path through which the operation voltage is supplied to the p-type semiconductor element during the photo-electric conversion operation may be different from a path through which the operation voltage is supplied to the p-type semiconductor element during the reset operation.

The method may further include: performing a photo-electric conversion using the p-type semiconductor element during the photo-electric conversion operation.

The method may further include: transmitting (e.g., directly transmitting) charges generated from the p-type semiconductor element to a floating diffusion node during the photo-electric conversion operation.

The method may further include: supplying the voltage to the n-type semiconductor element during reading out of a pixel signal generated based on the charges.

At least one other example embodiment of the present inventive concepts is directed to an image sensor. According to at least this example embodiment, the image sensor includes: a pixel including a thermoelectric element having a thermoelectric-junction; and a readout circuit configured to control the pixel so that the thermoelectric element performs a thermoelectric-cooling operation and a photoelectric conversion operation on the pixel.

The thermoelectric element may be a Peltier element including an n-type semiconductor element and a p-type semiconductor element, which form a Peltier-junction. According to at least one example embodiment, the image sensor may be a complementary metal oxide semiconductor (CMOS) image sensor for front side illumination (FSI). According to another example embodiment, the image sensor may be a CMOS image sensor for back side illumination (BSI).

At least one other example embodiment of the present inventive concepts is directed to an image processing device. According to at least this example embodiment, the image processing device includes: an image sensor and a control circuit configured to control operation of the image sensor. The image sensor includes: a pixel including a thermoelectric element having a thermoelectric-junction; and a readout circuit configured to control the pixel so that the thermoelectric element may perform a thermoelectric-cooling operation and a photoelectric conversion operation on the pixel.

The thermoelectric element may be a Peltier element including an n-type semiconductor element and a p-type semiconductor element, which form a Peltier-junction. While a first voltage is supplied to the n-type semiconductor element, the readout circuit may supply an operation voltage, which is higher than the first voltage, to the p-type semiconductor element during a reset operation.

The readout circuit may be configured to: transmit (e.g., directly transmit) charges generated by the p-type semiconductor element to a floating diffusion node during the photoelectric conversion operation; and supply the voltage to the n-type semiconductor element during a readout operation.

A portable electronic device according to an example embodiment of the present inventive concepts includes: an image processing device; a processor configured to control operation of the image processing device; and a display configured to display image data processed by the image processing device. The image processing device includes: an image sensor and a control circuit configured to control operation of the image sensor. The image sensor includes: a pixel including a thermoelectric element having a thermoelectric-junction; and a readout circuit configured to control the pixel so that the thermoelectric element may perform a thermoelectric-cooling operation and a photoelectric conversion operation on the pixel.

At least one other example embodiment of present inventive concepts provides an image sensor pixel including: a thermoelectric element configured to thermoelectrically cool the pixel, and to perform photoelectric conversion operation.

According to at least some example embodiments, the thermoelectric element may include: a thermoelectric-junction configured to perform the thermoelectric cooling of the pixel; and a photoelectric conversion portion configured to perform the photoelectric conversion operation.

The thermoelectric junction may be Peltier-junction. The photoelectric conversion portion may be a phase change material. The thermoelectric element may be configured to: thermoelectrically cool the pixel during a reset operation; and perform the photoelectric conversion operation during an integration operation.

At least one other example embodiment of present inventive concepts provides an image sensor including: a readout circuit configured to concurrently perform a thermal reset operation and an electrical reset operation on a pixel of the image sensor during a reset interval.

The readout circuit may be configured to: apply a thermal reset voltage to the pixel to perform the thermal reset operation, and apply an electrical reset voltage to the pixel to perform the electrical reset operation. The electrical reset voltage and the thermal reset voltage may be applied to the pixel concurrently.

The electrical reset voltage may be greater than the thermal reset voltage.

According to at least some example embodiments, the image sensor may further include: a pixel having a thermoelectric-element configured to: thermoelectrically cool the pixel, and perform photoelectric conversion operation.

The thermoelectric-element may further include: a thermoelectric-junction configured to perform the thermoelectric cooling of the pixel; and a photoelectric conversion portion configured to perform the photoelectric conversion operation

DETAILED DESCRIPTION

FIG. 1is a CMOS image sensor including a pixel having a thermoelectric element and a readout circuit according to an example embodiment of the present inventive concepts.

Referring toFIG. 1, a CMOS image sensor100includes a pixel110and a readout circuit120. For example, the pixel110and the readout circuit120may configure a unit pixel of a pixel array.

The pixel110may be thermoelectrically cooled on a pixel110using a thermoelectric device or thermoelectric element having thermoelectric-junction.

The thermoelectric element denotes an element that directly converts temperature differences into a voltage using a thermoelectric effect or directly converts voltage differences into temperature using the thermoelectric effect.

The thermoelectric effect includes Peltier effect, Seebak effect, and Thomson effect.

According to the thermoelectric effect, thermoelectric-cooling or thermoelectric-heating is performed on a junction of two different materials (this is called ‘thermoelectric-junction’).

The thermoelectric-effect may occur in the thermoelectric-junction, or an electrode connected to each of the materials. A direction of the thermoelectric-cooling and the thermoelectric-heating is determined based on polarities of voltages supplied to the materials or a difference between the voltages. That is, the thermoelectric-cooling and thermoelectric-heating use a thermoelectric effect generating heat flux between thermoelectric junctions.

As an example of the thermoelectric-cooling in the present inventive concepts, a process that performs Peltier-cooling on the pixel110using a Peltier-element having a Peltier-junction is described in detail; however, a technical concept of the present inventive concepts is not restricted thereto.

As described above, the Peltier-junction denotes a junction which may show Peltier-effect, and the Peltier-cooling denotes cooling using the Peltier-effect.

The pixel110includes a p-type semiconductor element111and an n-type semiconductor element112which form a thermoelectric-junction. For example, the p-type semiconductor element111and the n-type semiconductor element112which form the thermoelectric-junction may be connected to each other through an electric conductor such as metal.

The p-type semiconductor element111may be embodied in a p-type phase change material, e.g., GST, and more specifically, in Ge2Sb2Te5. The thermoelectric-junction is totally different from a p-n junction of a p-n diode in characteristics.

The readout circuit120controls or is controlled so that a thermoelectric element formed inside the pixel110may perform a thermoelectric-cooling operation and a photoelectric conversion operation on the pixel110during a reset operation. The thermoelectric element forming a thermoelectric-junction may be embodied in the p-type semiconductor element111and the n-type semiconductor element112. For example, the Peltier element includes the p-type semiconductor element111and the n-type semiconductor element112.

The readout circuit120includes a first switch121supplying a first voltage V1 to the n-type semiconductor element112in response to a first control signal cG, and a second switch122supplying an operation voltage Vdd to the p-type semiconductor element111in response to a second control signal TG. The first voltage V1 is lower than the operation voltage Vdd.

The readout circuit120further includes a reset switch123, a source follower SF, and a selection switch124. Each component121,122,123, SF, and124may be embodied in MOSFET.

The reset switch123supplies the operation voltage Vdd to a gate of the source follower SF in response to a reset signal RG. The source follower SF transmits a voltage corresponding to the operation voltage Vdd to the selection switch124based on a voltage of the gate. The selection switch124outputs a pixel signal POUT corresponding to charges generated by the pixel110in response to a selection signal SEL.

A capacitor CAP is formed in between a gate of the source follower SF and a ground. The capacitor CAP may perform a function of a floating diffusion node. In this case, the capacitor CAP may be a modeling of the floating diffusion node storing charges generated from the p-type semiconductor element111.

FIG. 2is an example timing diagram of control signals related to example operation of the readout circuit ofFIG. 1.

Referring toFIGS. 1 and 2, a first voltage V1 is supplied to the n-type semiconductor element112forming a thermoelectric-junction, e.g., Peltier-junction, through a first switch121for a thermoelectric reset in a first section T1, e.g., a reset operation. While the first voltage V1 is supplied to the n-type semiconductor element112, a voltage Vdd higher than the first voltage V1 is supplied to the p-type semiconductor element111through the reset switch123for an electric reset. As discussed herein, the first voltage V1 may be referred to as the thermal or thermoelectric reset voltage, and the voltage Vdd may be referred to as the electric or electrical reset voltage.

During a second section T2, e.g., during a charge transmission operation or a photoelectric conversion operation, a second control signal TG maintains a high level.

Accordingly, the operation voltage Vdd is supplied to the p-type semiconductor element111through a second switch122. Here, the p-type semiconductor element111may perform a function of a photo detector, a photoelectric conversion operation may be performed by the p-type semiconductor element111.

During a third section T3, when the pixel signal POUT is readout, a selection signal SEL transitions to the logic high level and a first control signal cG transitions to a high level. Accordingly, a first voltage V1 is supplied to the n-type semiconductor element112through the first switch121.

FIG. 3is a cross-sectional view of an example complementary metal oxides semiconductors (CMOS) image sensor for front end of the line (FEOL) integration front side illumination (FSI) including a portion of the pixel and the readout circuit ofFIG. 1.

Referring toFIGS. 1 to 3, an n-type semiconductor element n++is formed on or on a substrate sub, and a p-type semiconductor element, e.g., p-type Ge2Sb2Te5p-Ge2Sb2Te5, is formed on the n-type semiconductor element n++in order to form a thermoelectric-junction.

Here, the n-type semiconductor element n++and the p-type semiconductor element p-Ge2Sb2Te5are formed through a FEOL process. Thereafter, metals and/or contacts are formed through a BEOL process, and a passivation process is performed.

During the reset operation T1, the first switch121turned on in response to the first control signal cG supplies a first voltage V1 to the n-type semiconductor element n++through metals and/or contacts, and the second switch122turned on in response to the second control signal TG supplies an operation voltage Vdd to the p-type semiconductor element p-Ge2Sb2Te5through the metals and/or contacts while a first voltage V1 is supplied to the n-type semiconductor element n++. Accordingly, in a thermoelectric-junction, e.g., a junction between the n-type semiconductor element n++and the p-type semiconductor element p-Ge2Sb2Te5, thermoelectric-cooling, e.g., Peltier-cooling, is performed.

FIG. 4is a cross-sectional diagram of an example CMOS image sensor for back end of the line (BEOL) integration front side illumination (FSI) including a portion of the pixel and the readout circuit ofFIG. 1.

Referring toFIGS. 1, 2, and 4, the n-type semiconductor element n++is formed after the BEOL process, and the p-type semiconductor element, e.g., the p-type Ge2Sb2Te5p-Ge2Sb2Te5, is formed in order to form a thermoelectric-junction on the n-type semiconductor element n++.

During the reset operation T1, the first switch121turned on in response to the first control signal cG supplies the first voltage V1 to the n-type semiconductor element n++through metals and/or contacts, and the second switch122turned on in response to the second control signal TG supplies the operation voltage Vdd to the p-type semiconductor element p-Ge2Sb2Te5through the metals and/or contacts while the first voltage V1 is supplied to the n-type semiconductor element n++.

Accordingly, in a thermoelectric-junction, e.g., a junction between the n-type semiconductor element n++and the p-type semiconductor element p-Ge2Sb2Te5, thermoelectric-cooling, e.g., Peltier-cooling, is performed.

FIG. 5is a cross-sectional diagram of an example CMOS image sensor for back side illumination (BSI) including a portion of the pixel and the readout circuit ofFIG. 1.

Referring toFIGS. 1, 2, and 5, the n-type semiconductor element n++is formed on or in a substrate sub, and the p-type semiconductor element, e.g., the p-type Ge2Sb2Te5p-Ge2Sb2Te5, is formed in order to form a thermoelectric junction on the n-type semiconductor element n++.

During the reset operation T1, the first switch121turned on in response to the first control signal cG supplies the first voltage V1 to the n-type semiconductor element n++, and the second switch122turned on in response to the second control signal TG supplies the operation voltage Vdd to the p-type semiconductor element p-Ge2Sb2Te5while the first voltage V1 is supplied to the n-type semiconductor element n++.

Accordingly, in a thermoelectric-junction, e.g., a junction between the n-type semiconductor element n++and the p-type semiconductor element p-Ge2Sb2Te5, thermoelectric-cooling, e.g., Peltier-cooling, is performed.

InFIGS. 3 to 5, IR denotes incident light incident on the pixel100, e.g., visible light or infrared light. Moreover, as illustrated inFIGS. 3 to 5, the n-type semiconductor element n++and the p-type semiconductor element p-Ge2Sb2Te5are integrated inside the pixel110, so that an additional thermoelectric element is not necessary.

FIG. 6is an example CMOS image sensor including a pixel array where pixels performing thermoelectric-cooling are integrated.

Referring toFIG. 6, a pixel array140includes a plurality of pixels110-1to110-4and a plurality of readout circuits120-1to120-4. For convenience of description inFIG. 6, a CMOS image sensor including the four pixels110-1to110-4and the four readout circuits120-1to120-4is illustrated; however, the present inventive concept is not restricted thereto.

Each structure of the four pixels110-1to110-4is substantially the same as a structure of each pixel110described referring toFIGS. 3 to 5. Here, ‘substantially the same’ denotes ‘totally the same’ or ‘the same in a deviation range’. Here, the n-type semiconductor element112may be referred to as an n-plug. Electrons supplied from the p-type semiconductor element111, e.g., GST, may be supplied toann-plug112.

A pixel signal Sig_out1and Sig_out2output from each of the plurality of pixels110-1to110-4may be output through each column in response to a plurality of control signals. Moreover, corresponding first switches embodied in a corresponding row ROW1 and ROW2 may supply the first voltage V1 to a corresponding n-plug112in response to a corresponding first control signal cG.

FIG. 7is an example CMOS image sensor including the pixel included in the pixel array and the readout circuit illustrated inFIG. 6.

Except for a third switch125supplying a second voltage V2 to the p-type semiconductor element111based on a third control signal DG, a structure and an operation of the readout circuit120inFIG. 1are substantially the same as a structure and an operation of the readout circuit120A inFIG. 7.

Each of the plurality of readout circuit120-1to120-4may be embodied in the readout circuit120ofFIG. 1or the readout circuit120A ofFIG. 7.

FIG. 8is an example timing diagram of control signals related to example operation of the readout circuit illustrated inFIG. 7.

Referring toFIGS. 7 and 8, a first control signal cG transitions first to a high level for a thermoelectric reset, and a reset signal RG transitions to the high level for an electric reset during a first interval T1.

During a second interval T2, a third control signal DG transmits first to a high level prior to a second control signal TG for an electrical drain. Accordingly, the third switch125supplies a second voltage V2 to the p-type semiconductor element111in response to the third control signal DG. Here, the second voltage V2 is higher than the operation voltage Vdd.

FIG. 9is an example waveform diagram of signals in a conventional readout circuit connected to a conventional pixel without thermoelectric-cooling.

FIG. 10is an example waveform diagram of signals in a readout circuit according to an example embodiment of the present inventive concepts, which is connected to a pixel that performs thermoelectric-cooling.

FIG. 9shows a pixel signal POUTP outputting from a corresponding readout circuit when the n-type semiconductor element112and the first switch121are not embodied, andFIG. 10shows a pixel signal POUT output from a corresponding readout circuit120or120A when the n-type semiconductor element112and the first switch121are embodied.

Referring toFIG. 9, since a thermoelectric reset is not performed, the pixel signal POUTP is not totally reset during a reset operation. However, referring toFIG. 10, since the thermoelectric reset is performed in the pixel110according to the first control signal cG, a pixel signal POUT is almost completely reset during the reset operation.

FIG. 11is a flowchart for describing example operation of a CMOS image sensor according to an example embodiment of the present inventive concepts.

Referring toFIGS. 1 to 8, and 11, the pixel110is thermoelectric-cooled using a thermoelectric element, e.g., Peltier element, having a thermoelectric-junction, e.g., Peltier-junction, integrated to the pixel110during the reset operation T1(S110). And then, during the photoelectric conversion operation T2, a photoelectric conversion operation is performed using at least a portion of the thermoelectric element (S120).

FIG. 12is a block diagram illustrating an image processing device including a CMOS image sensor according to an example embodiment of the present inventive concepts. Referring toFIG. 12, an image processing device200includes a CMOS image sensor210and an image signal processor220.

The CMOS image sensor210includes the pixel110and the readout circuit120ofFIG. 1, or includes the pixel array140illustrated inFIG. 6. That is, the CMOS image sensor210may perform a thermoelectric-cooling operation and a photoelectric conversion operation using a thermoelectric element having a thermoelectric-junction.

The image signal processor220may process an image signal output from the CMOS image sensor210. The CMOS image sensor210and the image signal processor220may be embodied in one package, e.g., a multi-chip package or system in package (SiP).

FIG. 13is a block diagram illustrating another image processing device including a CMOS image sensor according to an example embodiment of the present inventive concepts.

Referring toFIG. 13, an image processing device300includes an application processor310, a camera module320, and a display330. The image processing device300may be a portable electronic device, e.g., a smart phone, a tablet personal computer (PC) or mobile internet device (MID).

When the camera module320includes only the CMOS image sensor210illustrated inFIG. 12, the application processor310may perform an image signal processing function processing an image signal output from the camera module320. Here, the image signal processing function may be the same as a function performed in the image signal processor220inFIG. 12.

When the camera module320is the image processing device200including the CMOS image sensor210and the image signal processor220illustrated inFIG. 12, the application processor310may process an image signal processed by the image signal processor220.

Here, the application processor310may perform a function of a control circuit or a processor controlling an operation of the CMOS image sensor included in the camera module320.

According to a control of the application processor310, the display330may display image data output from the camera module320.

FIG. 14is a block diagram of a portable electronic device including a CMOS image sensor according to still another example embodiment of the present inventive concepts. Referring toFIGS. 1 and 14, a portable electronic device400may include an application processor410, an image sensor420, a display430, and a memory441.

The portable electronic device400may be embodied in a laptop computer, a mobile phone, a smart phone, a tablet PC, a personal digital assistant (PDA), an enterprise digital assistant (EDA), a portable multimedia player (PMP), an MID, or an e-book. For example, the portable electronic device400may be a communication device which may support a mobile industry processor interface (MIPI®).

The application processor410may control an operation of the CMOS image sensor420, the display430, and the memory441.

A camera serial interface (CSI) host412embodied in the application processor410may perform a serial communication with a CSI device421of the CMOS image sensor420through a display serial interface. According to an example embodiment, a deserializer DES may be embodied in the CSI host412, and a serializer SER may be embodied in the CSI device421.

The CMOS image sensor420includes the pixel110which may perform thermoelectric-cooling and a photoelectric conversion operation. A display serial interface (DSI) host411embodied in the application processor410may perform a serial communication with a DSI device431of the display430through a display serial interface. According to an example embodiment, a serializer SER may be embodied in the DSI host411, and a deserializer DES may be embodied in the DSI device431.

The portable electronic device400may further include a radio frequency (RF) chip450which may communicate with the application processor410. A PHY (physical layer)413of the application processor410and a PHY451of the RF chip45may transmit and receive data each other according to a communication protocol, e.g., MIPI DigRF. The application processors410may store data processed by the CMOS image sensor420in the memory441.

The portable electronic device400may further include a data storage device442which is embodied in a non-volatile memory such as a NAND flash memory, a mike443, or a speaker444.

The data storage device442may be an external memory, e.g., an embedded multimedia card (eMMC) or a universal flash storage (UFS).

The portable electronic device400may communicate with an external communication device using at least one communication protocol or communication standard, e.g., an ultra-wideband (UWB)445, a wireless local area network (WLAN)446, a worldwide interoperability for microwave access (WiMAX)447, or a long term evolution (LTE™). The portable electronic device400may further include a global positioning system (GPS) receiver448.

FIG. 15is a block diagram of a portable electronic device including a CMOS image sensor according to still another example embodiment of the present inventive concepts. Referring toFIG. 15, a portable electronic device500may be embodied in a digital camera, a smart phone, or a tablet personal computer (PC).

The portable electronic device500includes an optical lens503, a CMOS image sensor510, a digital signal processor (DSP)600, and a display700.

The CMOS image sensor510generates image data IDATA for an object501or a scene incident through the optical lens503. The CMOS image sensor510includes a pixel array520, a row driver530, a timing generator540, a correlated double sampling (CDS) block550, a comparator block552, an analog-to-digital converter (ADC) block554, a control register block560, a ramp signal generator570, and a buffer580.

The pixel array520includes a plurality of unit pixels521arranged in a matrix form. As described referring toFIGS. 1 to 8, each of the plurality of unit pixels521includes the pixel110and the readout circuit120. That is, the pixel110may perform thermoelectric-cooling and a photoelectric conversion operation.

The row driver530supplies a plurality of control signals e.g., RG, TG, cG, and SEL for controlling an operation of each of the plurality of unit pixels521to the pixel array520according to a control of the timing generator540. According to an example embodiment, the row driver530may further include a control signal DG.

The timing generator540may control an operation of the row driver530, the CDS block550, the ADC block554, and the ramp signal generator570according to a control of the control register block560.

The CDS block550performs CDS on each pixel signal output from each of a plurality of column lines embodied in the pixel array520. The comparator block552compares each of a plurality of correlated double sampled pixel signals output from the CDS block550with a ramp signal output from the ramp signal generator570, and outputs a plurality of comparison signals according to a result of the comparison.

The ADC block554converts each of a plurality of comparison signals output from the comparator block552into a digital signal, and the buffer180stores digital signals output from the ADC block554.

The control register block560controls an operation of at least one of the timing generator540, the ramp signal generator570, and the buffer580according to a control of the DSP600. The buffer580transmits image data IDATA corresponding to a plurality of digital signals output from the ADC block554to the DSP600.

The DSP600includes an image signal processor610, a CMOS image sensor controller620, and the display interface630. The image signal processor610controls the display interface630and the CMOS image sensor controller620controlling the control register block160. According to an example embodiment, the CMOS image sensor510and the DSP600may be embodied in one package, e.g., a multi-chip package.

According to another example embodiment, the image sensor510and the image signal processor610may be embodied in one package, e.g., a multi-chip package.

The image signal processor610processes the image data IDATA transmitted from the buffer580, and transmits the processed image data to the display interface630. The CMOS image sensor controller620generates various control signals for controlling the control register block160according to a control of the image signal processor610.

The display interface630transmits image data processed by the image signal processor610to a display700. The display700displays image data output from the display interface630. The display700may be embodied in a thin film transistor-liquid crystal display (TFT-LCD), a light emitting diode (LED) display, an organic LED (OLED) display, an active-matrix OLED (AMOLED) display, or a flexible display.

Image sensors according to example embodiments of the present inventive concepts may perform a thermoelectric reset and an electrical reset during a reset operation, so that the image sensors may adapt to changes in temperature.

While inventive concepts have been particularly shown and described with reference to example embodiments thereof, it will be understood by those of ordinary skill in the art that various changes in forms and details may be made therein without departing from the spirit and scope of inventive concepts as defined by the following claims.