Image sensor, method of operating the same, and system including the image sensor

An image sensor includes a pixel array having a plurality of layers and a control unit. Each of the plurality of layers including pixels having a photoelectric conversion element and a transmission transistor therein. The photoelectric conversion element is configured to collect charges during an associated charge collection time period and the transmission transistor is configured to transmit the charges to a respective floating diffusion node at an end of the charge collection time period. The control unit configured to individually instruct the transmission transistors associated with different ones of the layers to transmit the charges to the respective floating diffusion nodes such that the charge collection time periods associated with the photoelectric conversion elements implemented in at least two of the layers differs in length.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority under 35 U.S.C. §119(a) from Korean Patent Application No. 10-2013-0095161 filed on Aug. 12, 2013, the disclosure of which is hereby incorporated by reference in its entirety.

BACKGROUND

Example embodiments relate to an image sensor, a method of operating the image sensor, and a system including the image sensor.

Image sensors convert an optical image into an electric signal. Recently, with developments in the computer industry and the communication industry, a demand for upgraded image sensors is increasing in various fields such as digital cameras, camcorders, personal communication systems (PCSs), game consoles, security cameras, medical micro-cameras, and robots. With the increase in the demand for such image sensors, a multi-layer image sensor including multiple layers is being developed as a next generation image sensor in order to obtain more pixel information, for example, more color information.

SUMMARY

At least one example embodiment relates to an image sensor.

According to an example embodiment of the inventive concepts, the image sensor includes a plurality of transmission transistors and a control unit. The plurality of transmission transistors each associated with one of a plurality of stacked pixel layers, the transmission transistors configured to transmit charges to respective floating diffusion nodes during respective charge transmission operations, the charges being generated during respective charge collection time periods by photoelectric conversion elements implemented in corresponding ones of the plurality of stacked pixel layers. The control unit configured to individually control the charge transmission operations of the transmission transistors associated with each of the plurality of stacked pixel layers such that the photoelectric conversion elements implemented in different ones of the plurality of stacked pixel layers may have different charge collection time periods.

In at least one embodiment, each of the plurality of stacked pixel layers may include a transmission control line configured to propagate a transmission control signal, the transmission control signal configured to control the charge transmission operation of the transmission transistors in a respective pixel layer among the plurality of stacked pixel layers.

In at least one embodiment, the charge collection time period of the photoelectric conversion elements implemented in the plurality of stacked pixel layers is different based on relative positions of the plurality of stacked pixel layers.

In at least one embodiment, at least one of the plurality of stacked pixel layers may include a pixel configured to obtain object information of an object and the control unit is configured to analyze the object information and differently control the charge transmission operations of the transmission transistors in the plurality of stacked pixel layers according to a result of the analysis.

In at least one embodiment, the object information may include information about a movement of the object. When a value of the movement is smaller than a threshold value, the control unit may differently control the respective charge transmission operations of the transmission transistors respectively implemented in the plurality of stacked pixel layers.

In at least one embodiment, the object information may include information about a distance between the object and the image sensor. When a change of the distance is smaller than a threshold value, the control unit may differently control the respective charge transmission operations of the transmission transistors respectively implemented in the plurality of stacked pixel layers.

At least one of the plurality of stacked pixel layers may include a pixel for obtaining image information of an object, and the control unit may analyze the image information and differently control the respective charge transmission operations of the transmission transistors respectively implemented in the plurality of stacked pixel layers according to a result of the analysis.

The image information may include information about a change between frames. When the change between frames is smaller than a threshold value, the control unit may differently control the respective charge transmission operations of the transmission transistors respectively implemented in the plurality of stacked pixel layers.

The image information may include information about a motion vector of an image of the object. When a value of the motion vector is smaller than a threshold value, the control unit may differently control the respective charge transmission operations of the transmission transistors respectively implemented in the plurality of stacked pixel layers.

According to another aspect of the inventive concept, there is provided an image processing system including the above-described image sensor and a processor for controlling the image sensor.

The image processing system may further include at least one sensor that senses an object and outputs object information of the object to the control unit. The processor may process an image of the object and output image information of a processed image to the control unit. The control unit may analyze at least one of the object information and the image information and differently control the respective charge transmission operations of the transmission transistors respectively implemented in the plurality of stacked pixel layers according to a result of the analysis.

According to another example embodiment of the inventive concepts, there is provided a portable electric device including the above-described image sensor, a processor that controls the image sensor, and a display unit that displays an image based on an output signal of the processor.

According to another example embodiment of the inventive concepts, there is provided a method of operating an image sensor including a pixel array having a plurality of stacked pixel layers.

In one example embodiment, the method includes analyzing information of an object the information being generated by the pixel array, and individually controlling transmission transistors associated with respective ones of the plurality of stacked pixel layers according to a result of the analysis such that the photoelectric conversion elements implemented in different ones of the plurality of stacked pixel layers may have different charge collection time periods.

Each of the pixel layers may include a transmission control line via which a transmission control signal for controlling the charge transmission operation of the transmission transistor is received. The respective charge transmission collection time periods of the photoelectric conversion elements respectively implemented in the plurality of stacked pixel layers may be different according to the positions of the plurality of stacked pixel layers.

At least one example embodiment relates to an image sensor.

In at least one embodiment, the image sensor includes a pixel array having a plurality of layers, each of the plurality of layers including pixels having a photoelectric conversion element and a transmission transistor therein, the photoelectric conversion element configured to collect charges during an associated charge collection time period and the transmission transistor configured to transmit the charges to a respective floating diffusion node at an end of the charge collection time period; and a control unit configured to individually instruct the transmission transistors associated with different ones of the layers to transmit the charges to the respective floating diffusion nodes such that the charge collection time periods associated with the photoelectric conversion elements implemented in at least two of the layers differs in length.

In at least one embodiment, the control unit is configured to adjust the charge collection time period of the photoelectric conversion elements of the pixels in the layers based on a position of the layer associated with the pixels in relation to other ones of the layers.

In at least one embodiment, each of the pixels is configured to output a pixel signal, and the control unit is configured to adjust the charge collection time period of the photoelectric conversion elements of the pixels in the layers based on an attenuation in the pixel signals due to stacking of the layers.

In at least one embodiment, each of the layers include a transmission control line configured to propagate a transmission control signal to the transmission transistors associated with the layer such that the associated transmission transistor transmit the charges to the respective floating diffusion node based on the transmission control signal.

In at least one embodiment the image sensor is configured to sense an object, and the control unit is configured to adjust the charge collection time period if one or more of an amount of movement of the object and a distance between the object and the image sensor is greater than a threshold.

DETAILED DESCRIPTION OF THE EMBODIMENTS

FIG. 1is a block diagram of an image processing system10according to an example embodiment of the inventive concepts.

Referring toFIG. 1, the image processing system10may include an image sensor100, an image signal processor (ISP)200, and a display300.

In one example embodiment, the image sensor100and the ISP200may be implemented by using a printed circuit board (PCB) such as a motherboard, an integrated circuit (IC), or a system on chip (SoC). Alternatively, in another example embodiment, the image sensor100and the ISP200may be implemented by using a multi-chip package (MCP) or a system in package (SiP).

The image processing system10may be used in a digital camera or a portable electronic device including a digital camera. The image processing system10may sense an object500or an image of the object500that is received via a lens400, under the control of the ISP200. The image processing system10may further include at least one peripheral sensor600that directly generates object information OBI2 of the object500.

According to an example embodiment, the peripheral sensor600may be a depth sensor capable of generating depth information of the object500. For example, the depth sensor may include a time of flight (TOF) sensor. Alternatively, according to another example embodiment, the peripheral sensor600may be a motion sensor capable of generating motion information of the object500. For example, the motion sensor may include a dynamic vision sensor (DVS).

The image sensor100may sense the object500or the image of the object500received via the lens400, generate image data DATA based on a result of the sensing, and output image data DATA to the ISP200.

The image sensor100may differently control respective charge transmission operations of transmission transistors of photoelectric conversion elements respectively implemented in a plurality of stacked pixel layers, in order to differently control charge collection time periods of the photoelectric conversion elements.

According to an example embodiment, the image sensor100may analyse at least one of object information OBI1 and image information IMI of the object500, which are output by the ISP200, and may differently control the respective charge transmission operations of the transmission transistors of the photoelectric conversion elements respectively implemented in the stacked pixel layers according to a result of the analysis.

According to another example embodiment, the image sensor100may analyse the object information OBI2 output by the peripheral sensor600and may differently control the respective charge transmission operations of the transmission transistors of the photoelectric conversion elements respectively implemented in the stacked pixel layers according to a result of the analysis.

The image sensor100may be implemented by using a separate chip. For example, the image sensor100may be implemented by using a CMOS image sensor chip.

FIG. 2is a schematic block diagram of the image sensor100illustrated inFIG. 1.

Referring toFIGS. 1 and 2, the image sensor100may include a pixel array110, a control unit125, a row decoder133, a row driver135, a column decoder153, a column driver155, and a plurality of analog-digital converters (ADCs)171,173, and175.

The pixel array110may sense light reflected by the object500and may generate the object information OBI1 of the object500and/or the image information IMI of the object500. The pixel array110may include a plurality of pixels arranged in a two-dimensional matrix. The pixel array110may include a plurality of pixel layers111,113, and115.

For convenience of explanation,FIG. 2illustrates the case where the pixel array110includes three pixel layers111,113and115, but example embodiments of the inventive concepts are not limited to the 3 pixel layers. For example, the pixel array110may include at least two pixel layers.

FIG. 3illustrates a schematic structure of a pixel array110-1, which is an embodiment of the pixel array110illustrated inFIG. 2. The pixel layers111,113, and115illustrated inFIG. 2may be implemented by using a plurality of stacked pixel layers111-1,113-1, and115-1illustrated inFIG. 3, respectively.

At least one of the stacked pixel layers111-1,113-1, and115-1may sense light reflected by the object500and may generate the image information IMI of the object500. Each of the stacked pixel layers111-1,113-1, and115-1may include a plurality of pixels117and a plurality of control lines, namely, a transmission control line TGL, a reset control line RGL, and a selection control line SGL.

Each pixel117may sense light reflected by the object500and may generate the image information IMI of the object500.

Each pixel117may be a color pixel capable of generating the image information IMI of the object500. For example, the color pixel may be a red pixel that converts light in a red spectrum into an electric signal, a green pixel that converts light in a green spectrum into an electric signal, or a blue pixel that converts light in a blue spectrum into an electric signal. The color pixel may also be a white pixel, a cyan pixel, a yellow pixel, or a magenta pixel.

FIG. 4illustrates a schematic structure of a pixel array110-2, which is another example embodiment of the pixel array110illustrated inFIG. 2.

Referring toFIGS. 1 and 4, the pixel array110-2may include a plurality of stacked pixel layers111-2,113-2, and115-2.

At least one of the stacked pixel layers111-2,113-2, and115-2may sense light reflected by the object500and may generate the object information OBI1 and image information IMI of the object500.

At least one of the stacked pixel layers111-2,113-2, and115-2may include the pixels117and a plurality of different pixels119. According to an example embodiment, each of the different pixels119may be a depth pixel or motion sensor pixel capable of generating the object information OBI1 of the object500. The different pixel119may be implemented in a range other than an active range AR of the pixel array111-2, in which the pixels117are implemented. Alternatively, the different pixels119may be implemented in a part of the active range AR.

FIG. 4illustrates the case where the active range AR is all but the outermost area of the pixel array111-2, but example embodiments of the inventive concepts are not limited thereto.

FIG. 5illustrates a schematic structure of a pixel array110-3, which is another example embodiment of the pixel array110illustrated inFIG. 2.

Referring toFIGS. 1 and 5, the pixel array110-3may include a plurality of stacked pixel layers111-3and113-3.

The pixel layer111-3may be formed of an organic photoelectric-conversion film. The pixel layer111-3may include a plurality of pixels117-1. For example, each pixel117-1may be a green pixel.

The pixel layer113-3may include pixels117-2and pixels117-3. The pixels117-2and117-3may be arranged in a checker pattern. The checker pattern may be such each of the pixels117-2are surrounded by pixels117-3and each of the pixels117-3are surrounded by pixels117-2.

Each pixel117-2may be a red pixel, and each pixel117-3may be a blue pixel. In this case, each pixel117-2may include a yellow organic color filter, and each pixel117-3may include a cyan organic color filter.

FIG. 6is a schematic sectional view of the pixel array110-3illustrated inFIG. 5.

Referring toFIG. 6, the pixel array110-3may further include a microlens11, an epitaxial layer13, a dielectric layer17, and a substrate21.

A photo detector (PD)15may generate photons in response to externally incident light. The externally incident light may be focused by the microlens. However, the pixel array110-3may be implemented without the microlens11.

The photo detector PD15may be formed in the epitaxial layer13. The photo detector PD15is a photosensitive element, and may be implemented by a photodiode, a phototransistor, a photogate or a pinned photodiode. However, example embodiments are not limited thereto and the photo detector PD15may be implemented using other photosensitive elements.

The dielectric layer17may be an oxide layer or a composite layer of an oxide layer and a nitride layer. For example, the oxide layer may be a silicon oxide layer. The dielectric layer17may include metals19.

Electrical wiring for a sensing operation of the pixel array110-3may be formed by the metals19. According to an example embodiment, the metals19may be used to reflect light received via the PD15back to the PD15.

The metals19may copper, titanium, or a titanium nitride and the substrate21may be a silicon substrate.

FIG. 7illustrates a schematic structure of a pixel array110-4, which is another example embodiment of the pixel array110illustrated inFIG. 2.

Referring toFIG. 7, the pixel array110-4may include a plurality of stacked pixel layers111-4,113-4, and115-4.

Each of the pixel layers111-4,113-4, and115-4may be formed of an organic photoelectric-conversion film.

The pixel layer111-4may include pixels117-1, the pixel layer113-4may include pixels117-2, and the pixel layer115-4may include pixels117-3.

According to an embodiment, each pixel117-1may be a green pixel, each pixel117-2may be a blue pixel, and each pixel117-3may be a red pixel. In this case, each pixel117-3implemented in the pixel layer115-4may include no filters (for example, a red color filter or a yellow organic color filter).

According to another embodiment, each pixel117-1may be a green pixel, each pixel117-2may be a red pixel, and each pixel117-3may be a blue pixel. In this case, each pixel117-3implemented in the pixel layer115-4may include no color filters (for example, a blue color filter or a cyan organic color filter).

FIG. 8illustrates a schematic structure of a pixel array110-5, which is another example embodiment of the pixel array110illustrated inFIG. 2.

Referring toFIG. 8, the pixel array110-5may include a plurality of stacked pixel layers111-5,113-5, and115-5.

Each of the stacked pixel layers111-5,113-5, and115-5may be formed of an organic photoelectric-conversion film. Each pixel117-1implemented in the pixel layer111-5may be a blue pixel, each pixel117-2implemented in the pixel layer113-5may be a green pixel, and each pixel117-3implemented in the pixel layer115-5may be a red pixel, but example embodiments of the inventive concepts are not limited to the order of red, green, and blue pixels.

FIG. 9is a schematic sectional view of the pixel array110-5illustrated inFIG. 8.

Referring toFIG. 9, the pixel array110-5may include a plurality of electrodes31,32,33, and34, insulation layers35, and a substrate37.

The electrode31may be formed of a patterned indium tin oxide (ITO), a conducting polymer, or a semitransparent metal. The electrode32may be formed of a semitransparent metal. The electrode33may be formed of an ITO, a conducting polymer, or a semitransparent metal. The electrode34may be formed of a metal.

Each of the insulation layers35may be formed of an oxide layer or a composite layer of an oxide layer and a nitride layer. For example, the oxide layer may be a silicon oxide layer. The substrate37may be a transparent substrate. In other words, the substrate37may transmit externally-incident light39.

Referring back toFIGS. 1 to 3, for convenience of explanation, a plurality of control lines, namely, the transmission control line TGL, the reset control line RGL, and the selection control line SGL, are only illustrated inFIG. 3. However, the pixel layers111-1through111-5(collectively,111), the pixel layers113-1through113-5(collectively,113), and the pixel layers115-1through115-5(collectively,115) illustrated inFIGS. 3 through 9may each include the control lines TGL, RGL, and SGL illustrated inFIG. 3.

The control lines, namely, the transmission control line TGL, the reset control line RGL, and the selection control line SGL, may transmit control signals to each row of pixels117. The control lines, namely, the transmission control line TGL, the reset control line RGL, and the selection control line SGL, may be implemented in units of rows.

The transmission control line TGL may transmit to a transmission transistor a transmission control signal for controlling a charge transmission operation of the transmission transistor. The reset control line RGL may transmit to a reset transistor a reset control signal for controlling a floating diffusion node.

The selection control line SGL may transmit to a selection transistor a selection control signal for transmitting a signal (for example, a noise signal or a pixel signal) generated by the pixels117to a column line, namely, an output line.

InFIG. 3, the control signal lines RGL and SGL are implemented in each pixel layer. However, according to an example embodiment, the control signal lines RGL and SGL may be shared in units of rows by the pixel layers111,113, and115.

FIG. 10is a circuit diagram of a pixel117implemented in each pixel layer illustrated inFIG. 3. AlthoughFIG. 10illustrates the case where the pixel117has a four-transistor structure, the pixel117may be implemented as a three-transistor structure, a five-transistor structure, or a gate structure similar to a four-transistor structure. For convenience of explanation,FIG. 10illustrates only one of the pixels117ofFIG. 3.

Referring toFIGS. 1 to 3and10, the pixel117may include a photoelectric conversion element PD, a transmission transistor TX, a reset transistor RX, a selection transistor SX, and an amplification transistor DX.

The photoelectric conversion element PD may generate photo charges corresponding to light reflected by the object500and may accumulate the generated photo charges. The photoelectric conversion element PD may be implemented by using a photo diode, a photo transistor, a photo gate, or a pinned photo diode. The photoelectric conversion element PD may be connected with the transmission transistor TX.

The transmission transistor TX may perform charge transmission operations of transmitting the photo charges generated by a photoelectric conversion operation of the photoelectric conversion element PD to a floating diffusion node FD.

The transmission transistor TX may be controlled according to a transmission control signal TG provided to a gate of the transmission transistor TX via a transmission control line TGL. In other words, the transmission control signal TG may be a control signal for controlling a charge transmission operation of the transmission transistor TX. For example, when the transmission control signal TG is input to the transmission transistor TX, the gate of the transmission transistor TX may be turned on.

The floating diffusion node FD may accumulate the photo charges received from the photoelectric conversion element PD via the transmission transistor TX, and may generate a voltage corresponding to the accumulated photo charges. The floating diffusion node FD may be connected with a gate of the amplification transistor DX, and thus may control the amplification transistor DX.

The reset transistor RX may reset the floating diffusion node FD. The reset transistor RX may be connected between the floating diffusion node FD and a power line that supplies a driving voltage VDD. The reset transistor RX may be controlled according to a reset control signal RS that a gate of the reset transistor RX receives via a reset control line RGL. For example, when the reset transistor RX is turned on in response to the reset control signal RS, the floating diffusion node FD is reset.

The amplification transistor DX may be a common-drain amplifier which performs a source follower operation. The amplification transistor DX may output a voltage associated with the driving voltage VDD to the selection transistor SX, based on the voltage corresponding to the photo charges accumulated in the floating diffusion node FD.

The selection transistor SX may be controlled according to a selection control signal SEL that a gate of the selection transistor SX receives via a selection control line SGL. The selection transistor SX may select pixels117in units of columns. The selection transistor SX may output the voltage output by the amplification transistor DX to an output line OUT.

The control signal lines RGL, TGL, and SGL, which transmit the control signals RS, TG, and SEL for respectively controlling the transmission transistor TX, the reset transistor RX, and the selection transistor SX, may be extended in a row direction.

FIG. 11is a timing diagram for describing a charge collection time period of the photoelectric conversion element PD of the pixel117illustrated inFIG. 10.

Referring toFIGS. 1 to 3,10, and11, the reset transistor RX may be turned on from a first time point T1 to a fourth time point T4 in response to the reset control signal RS.

The transmission transistor TX may be turned on from a second time point T2 to a third time point T3 in response to the transmission control signal TG. As the transmission transistor TX is turned on, photo charges generated by the photoelectric conversion element PD, for example, photons, may be transmitted to the power line supplying the driving voltage VDD via the floating diffusion node FD and the reset transistor RX.

The selection transistor SX may be turned on from a fifth time point T5 to a tenth time point T10 in response to the selection control signal SEL. As the reset transistor RX is turned on from a sixth time point T6 to a seventh time point T7 in response to the reset control signal RS, the selection transistor SX may output a signal corresponding to a voltage of the floating diffusion node FD, for example, a noise signal, to the output line OUT.

As the transmission transistor TX is turned off from the third time point T3 to an eighth time point T8, the photoelectric conversion element PD may generate photo charges corresponding to incident light from the third time point T3 to the eighth time point T8 (for example, during a charge collection time period P), and may accumulate the generated photo charges.

As the transmission transistor TX is turned on from the eighth time point T8 to a ninth time point T9 in response to the transmission control signal TG, the selection transistor SX may output a signal corresponding to the photo charges generated by the photoelectric conversion element PD, for example, a pixel signal, to the output line OUT.

The charge collection time period may denote an integration time or an exposure time.

Referring toFIG. 2, the control unit125may generate a control signal(s) for controlling respective operations of the row decoder133, the row driver135, the column decoder153, the column driver155, and the ADCs171,173, and175. For example, the control unit125may generate a plurality of row control signals for selecting a specific row line from among a plurality of row lines included in each of the pixel layers111,113, and115.

The row control signals may include the transmission control signal TG, the reset control signal RS, and the selection control signal SEL, and the like. The control unit125may individually control respective charge transmission operations of the transmission transistors TX implemented in each of the pixel layers111,113, and115. By individually controlling the charge transmission operations, the control unit may individually adjust respective charge collection time periods P of the photoelectric conversion element PD of the pixels117respectively implemented in the pixel layers111,113, and115. Therefore, each of the photoelectric conversion elements PD may have a different charge collection time period P.

By controlling the charge collection time P of each of the pixel layers111,113and115, the image sensor100may decrease signal attenuation that may occur due to the stacking of the pixel layers111,113and115

According to an example embodiment, the control unit125may analyze the object information OBI1 and/or image information IMI of the object500received from the ISP200, and may differently control the respective charge transmission operations of the transmission transistors TX respectively implemented in the pixel layers111,113, and115according to a result of the analysis.

In one example embodiment, the object information OBI1 may include information about a movement (or motion) of the object500, and the control unit125may differently control the respective charge transmission operations of the transmission transistors TX respectively implemented in the pixel layers111,113, and115, when a value of the movement is less than a threshold value.

In one example embodiment, the object information OBI1 may include information about a distance between the object500and the image sensor100, and the control unit125may differently control the respective charge transmission operations of the transmission transistors TX respectively implemented in the pixel layers111,113, and115, when a variation of the distance is less than a threshold value.

The image information IMI may include information about a change between frames, and the control unit125may differently control the respective charge transmission operations of the transmission transistors TX respectively implemented in the pixel layers111,113, and115, when the change between frames is less than a threshold value.

The image information IMI may include information about a motion vector of an image of the object500, and the control unit125may differently control the respective charge transmission operations of the transmission transistors TX respectively implemented in the pixel layers111,113, and115, when a value of the motion vector is less than a threshold value.

According to another embodiment, rather than receiving the information to analyse from, the ISP200, the control unit125may analyze the object information OBI2 of the object500received from the peripheral sensor600, and may differently control the respective charge transmission operations of the transmission transistors TX respectively implemented in the pixel layers111,113, and115, according to a result of the analysis. For example, the object information OBI2 may include information about a movement of the object500, and the control unit125may differently control the respective charge transmission operations of the transmission transistors TX respectively implemented in the pixel layers111,113, and115, when a value of the movement (or motion) is less than a threshold value.

The object information OBI2 may include information about a distance between the object500and the image sensor100, and the control unit125may differently control the respective charge transmission operations of the transmission transistors TX respectively implemented in the pixel layers111,113, and115, when a variation of the distance is less than a threshold value.

The row decoder133may decode the row control signals output by the control unit125, for example, row address signals, and may output a plurality of row selection signals according to a result of the decoding. The row driver135may drive the pixels included in at least one of a plurality of rows included in each of the pixel layers111,113, and115in response to each of the row selection signals output by the row decoder133.

The column decoder153may decode a plurality of column control signals output by the control unit125, for example, column address signals, and may output a plurality of column selection signals according to a result of the decoding. The column driver155may drive a plurality of column lines included in each of the pixel layers111,113, and115in response to the column selection signals output by the column decoder153, respectively.

For convenience of explanation, the image sensor100includes the single row driver135and the single column driver155. However, according to an embodiment, the image sensor100may include a plurality of row drivers for driving respective row lines of each of the pixel layers111,113, and115and/or a plurality of column drivers for driving respective column lines of each of the pixel layers111,113, and115. For example, the row lines may include the transmission control line TGL, the reset control line RGL, and the selection control line SGL.

In this case, the image sensor100may include a plurality of row decoders and/or a plurality of column decoders.

The ADCs171,173and175may perform ADC on signals output by each of the pixel layers111,113, and115, respectively, and may output results of the ADC as image data DATA to the ISP200. For example, the image data DATA may include the object information OBI1 and/or the image information IMI.

According to an embodiment, each of the ADCs171,173, and175may further include a correlated double sampling (CDS) circuit (not shown) which performs CDS on the signals output by each of the pixel layers111,113, and115.

In this case, each of the ADCs171,173and175, may compare a signal corresponding to a result of the CDS with a ramp signal, and may output a result of the comparison as the image data DATA.

The ISP200may generate an image by processing the image data DATA output by the image sensor100, and may output the generated image to the display300.

The ISP200may also extract the object information OBI1 and/or image information IMI of the object500from the image data DATA output by the image sensor100, and may transmit the extracted object information OBI1 and/or image information IMI to the image sensor100.

For convenience of explanation,FIG. 1illustrates the case where the ISP200is implemented outside the image sensor100, however, the ISP200may be implemented within the image sensor100.

The display300may be any display devices capable of displaying images. For example, the display300may be implemented using a touch screen, a liquid crystal display (LCD), 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.

FIG. 12is a conceptual diagram for describing a method of operating the image sensor100according to an example embodiment of the inventive concepts.

Referring toFIGS. 1 to 3and10to12, the control unit125may individually control respective charge transmission operations of the transmission transistors TX implemented in each of the pixel layers111,113, and115. By individually controlling the charge transmission operations, the control unit125may individually adjust respective charge collection time periods P of the photoelectric conversion elements PDs respectively implemented in the pixel layers111,113, and115. Therefore, the photoelectric conversion elements PD of each of the pixel layers111,113and115may have a different charge collection time period P. By controlling the charge collection time P of each of the pixel layers111,113and115, the image sensor100may decrease signal attenuation that may occur due to the stacking of the pixel layers111,113and115.

The control unit125may control the respective charge collection time periods P of the photoelectric conversion elements PDs respectively implemented in the pixel layers111,113, and115, as illustrated inFIG. 12.

A charge collection time period (P=P2) of a photoelectric conversion element PD implemented in each of a plurality of rows ROW1 through ROWn of the second pixel layer113are longer than a charge collection time period (P=P1) of a photoelectric conversion element PD implemented in each of a plurality of rows ROW1 through ROWk of the first pixel layer111. A charge collection time period (P=P3) of a photoelectric conversion element PD implemented in each of a plurality of rows ROW1 through ROWm of the third pixel layer115are longer than the charge collection time period (P=P2) of the photoelectric conversion element PD implemented in each of the rows ROW1 through ROWn of the second pixel layer113.

In other words, the respective charge collection time periods P1, P2, and P3 of the photoelectric conversion element PDs respectively implemented in the pixel layers111,113, and115may differ according to the positions of the pixel layers. According to an example embodiment, as a pixel layer is positioned to be relatively lower as compared to other ones of the pixel layers, a charge collection time period of a photoelectric conversion element PD of the pixel layer may increase or decrease.

FIG. 13is a flowchart of the method of operating the image sensor100.

Referring toFIGS. 1 through 13, the control unit125may analyze at least one of the object information OBI1 and image information IMI of the object500generated by the pixel array110, in operation S110. Alternatively, the control unit125may analyze the object information OBI2 of the object500generated by the peripheral sensor600.

In operation S130, the control unit125may differently control respective charge transmission operations of the transmission transistors TXs for transmitting charges generated by the photoelectric conversion operations of the photoelectric conversion element PDs respectively implemented in the stacked pixel layers111,113, and115to the floating diffusion node FD, in order to differently control respective charge collection time periods P of the photoelectric conversion elements PDs.

FIG. 14is a block diagram of an image processing system1000according to another example embodiment of the inventive concepts.

Referring toFIG. 14, the image processing system1000may be implemented by an image processing device capable of using or supporting a mobile industry processor interface (MIPI). Examples of the image processing device may include a personal digital assistant (PDA), a portable multimedia player (PMP), an internet protocol television (IPTV), a smart phone, a tablet PC, and a mobile internet device (MID).

The image processing system1000includes the image sensor100, an application processor (AP)1010, and a display1050.

A camera serial interface (CSI) host1012implemented in the AP1010may serially communicate with a CSI device1041of the image sensor100via a CSI. The CSI host1012may include a deserializer (DES) and the CSI device1041may include a serializer (SER).

A display serial interface (DSI) host1011implemented in the AP1010may serially communicate with a DSI device1051of the display1050via a DSI. The DSI host1011may include an SER and the DSI device1051may include a DES.

According to an example embodiment, the image processing system1000may further include a RF chip1060capable of communicating with the AP1010.

A Physical layer (PHY)1013included in the AP1010and a PHY1061included in the RF chip1060may exchange data according to a MIPI DigRF protocol.

According to an example embodiment, the image processing system1000may further include a global positioning system (GPS)1020, a storage1070, a microphone (MIC)1080, a dynamic random access memory (DRAM)1085, and a speaker1090.

The image processing system1000may communicate with an external device by using a world interoperability for microwave access (Wimax) module1030, a wireless LAN (WLAN) module1100, and/or an ultra wideband (UWB) module1110.

FIG. 15is a block diagram of an image processing system1200according to another example embodiment of the inventive concepts.

Referring toFIG. 15, the image processing system1200may include the image sensor100, a processor1210, a memory1220, a display unit1230, and an interface (I/F)1240.

According to an example embodiment, the image processing system1200may be implemented by a medical device or a portable electric device. The portable electric device may be implemented by a smart phone, a tablet PC, a personal digital assistant (PDA), an enterprise digital assistant (EDA), a portable multimedia player (PMP), a mobile internet device (MID), or an e-book.

The processor1210may control an operation of the image sensor100, or may process image data output by the image sensor100. According to an example embodiment, the ISP200may be embodied as the processor1210.

The memory1220may store a program for controlling an operation of the image sensor100and an image generated by the processor1210, via the bus1250under the control of the processor1210, and the processor1210may access stored information to execute the program. For example, the memory1220may be implemented by using a non-volatile memory.

The display unit1230may receive an image from the processor1210or the memory1220and display the image. The I/F1240may be implemented using an interface for inputting and outputting a 2-dimensional or a 3-dimensional image. According to an example embodiment, the interface1240may be implemented by using a wireless interface.

An image sensor according to an example embodiment of the inventive concepts may prevent signal attenuation from occurring due to stacking of a plurality of pixel layers, by differently controlling respective charge collection time periods of photoelectric conversion elements respectively implemented in the pixel layers.