Patent Publication Number: US-2023134771-A1

Title: Image sensor, image acquisition apparatus, and electronic apparatus including the image acquisition apparatus

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims priority to Korean Patent Application No. 10-2021-0146059, filed on Oct. 28, 2021, in the Korean Intellectual Property Office, the disclosure of which is incorporated by reference herein in its entirety. 
     BACKGROUND 
     1. Field 
     Example embodiments of the present disclosure relate to image sensors, image acquisition apparatuses, and electronic apparatuses including the image acquisition apparatuses. 
     2. Description of Related Art 
     Image sensors receive light incident thereon from an object and photoelectrically convert the received light into an electrical signal. 
     Such an image sensor uses a color filter consisting of an array of filter elements capable of selectively transmitting red light, green light, and blue light for color expression, senses the amount of light that passed through each filter element, and then forms a color image of an object through image processing. 
     Characteristics of image sensors such as resolution, frame rate, low light imaging, and high dynamic range (hereinafter, referred to as HDR) have been gradually improved. In order to simultaneously improve the HDR and frame rate, a new imaging method has been proposed, and recently, an image sensor to which photon counting imaging technology is applied has been developed. 
     Photon counting imaging uses a fast photodiode, for example, a single photon avalanche diode (hereinafter, referred to as SPAD), to count the number of photons incident on a pixel for a certain period of time on a time axis, measures the amount of light for each pixel, and generates a two-dimensional image. 
     SUMMARY 
     One or more example embodiments provide image sensors, image acquisition apparatuses, and electronic apparatuses including the image acquisition apparatuses. 
     Additional aspects will be set forth in part in the description which follows and, in part, will be apparent from the description, or may be learned by practice of example embodiments of the disclosure. 
     According to an aspect of an example embodiment, there is provided an image sensor using photon counting, the image sensor including a pixel including a plurality of sub-pixels, a plurality of counters which are respectively connected to the plurality of sub-pixels and configured to count and output a plurality of pulse signals generated based on photons incident on each of the plurality of sub-pixels, and an operator configured to perform an operation on an output value output from each of the plurality of counters. 
     Each of the plurality of sub-pixels may be a single photon avalanche diode (S PAD). 
     The plurality of sub-pixels may include a first sub-pixel and a second sub-pixel. 
     The operation may be any of an addition, a subtraction, a multiplication, and a division. 
     At least one operation from among the addition, the subtraction, the multiplication, and the division may be preset. 
     The operator may be further configured to output a result value obtained by performing a subtraction operation on a first output value output from a first counter connected to the first sub-pixel and a second output value output from a second counter connected to the second sub-pixel. 
     Sizes of the plurality of sub-pixels may be different from each other. 
     According to another aspect of an example embodiment, there is provided an image acquisition apparatus including a pixel array including a plurality of pixels that respectively includes a plurality of sub-pixels, a plurality of counters which are respectively connected to the plurality of sub-pixels and are configured to count and output a plurality of pulse signals generated based on photons incident on each of the plurality of sub-pixels, an operator configured to perform an operation on an output value output from each of the plurality of counters, and a processor configured to process an operation value output from an operator of each of the plurality of pixels. 
     Each of the plurality of sub-pixels may be a single photon avalanche diode (S PAD). 
     The operation may be any of an addition, a subtraction, a multiplication, and a division. 
     The processor may be further configured to set any operation from among the addition, the subtraction, the multiplication, and the division. 
     The plurality of sub-pixels may include a first sub-pixel and a second sub-pixel. 
     The operator may be further configured to output a result value obtained by performing a subtraction operation on a first output value output from a first counter connected to the first sub-pixel and a second output value output from a second counter connected to the second sub-pixel. 
     The processor may be further configured to perform a phase difference auto focusing (AF) based on a plurality of result values respectively output from operators of the pixel array. 
     The processor may be further configured to output a select signal for each of the plurality of sub-pixels. 
     A first sub-pixel from among the plurality of sub-pixels may be a pixel having a first luminance, and a second sub-pixel from among the plurality of sub-pixels is a pixel having a second luminance that is higher than the first luminance. 
     Sizes of the plurality of sub-pixels may be different from each other. 
     Each of the pixel array and a readout circuit may correspond to an M×N array, and, when the number of the plurality of sub-pixels is K, a resolution of an image obtained from the pixel array is K×M×N. 
     The pixel array, the plurality of counters, and the operator may be provided in a pixel, and the processor may be provided outside of the pixel. 
     According to another aspect of an example embodiment, there is provided an electronic apparatus including an image acquisition apparatus including a pixel array including a plurality of pixels that respectively includes a plurality of sub-pixels, a plurality of counters which are respectively connected to the plurality of sub-pixels and are configured to count and output a plurality of pulse signals generated based on photons incident on each of the plurality of sub-pixels, an operator configured to perform an operation on an output value output from each of the plurality of counters, and a processor configured to process an operation value output from an operator of each of the plurality of pixels. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The above and/or other aspects, features, and advantages of example embodiments of the disclosure will be more apparent from the following description taken in conjunction with the accompanying drawings, in which: 
         FIG.  1    is a schematic block diagram of an image acquisition apparatus according to an example embodiment; 
         FIG.  2    is a detailed block diagram of an image sensor shown in  FIG.  1   ; 
         FIG.  3    is a circuit diagram of the image sensor shown in  FIG.  2   ; 
         FIG.  4    is a detailed block diagram of the image sensor including a plurality of sub-pixels according to another example embodiment; 
         FIG.  5    is a circuit diagram of a pixel array including a plurality of sub-pixels according to another example embodiment; 
         FIG.  6    is a schematic block diagram of an image acquisition apparatus according to another example embodiment; 
         FIG.  7    is a schematic block diagram of an image acquisition apparatus according to another example embodiment; 
         FIGS.  8  and  9    are diagrams illustrating a phase difference autofocus (AF) according to another example embodiment; 
         FIG.  10    is a block diagram of a schematic structure of an electronic apparatus according to another example embodiment; 
         FIG.  11    is a block diagram schematically illustrating a camera module provided in the electronic apparatus of  FIG.  10   ; and 
         FIGS.  12 ,  13 ,  14 ,  15 ,  16 ,  17 ,  18 ,  19 ,  20 , and  21    are views illustrating various examples of an electronic apparatus including an image acquisition apparatus according to an example embodiment. 
     
    
    
     DETAILED DESCRIPTION 
     Reference will now be made in detail to embodiments, examples of which are illustrated in the accompanying drawings, wherein like reference numerals refer to like elements throughout. In this regard, the present embodiments may have different forms and should not be construed as being limited to the descriptions set forth herein. Accordingly, the embodiments are merely described below, by referring to the figures, to explain aspects. As used herein, the term “and/or” includes any and all combinations of one or more of the associated listed items. Expressions such as “at least one of,” when preceding a list of elements, modify the entire list of elements and do not modify the individual elements of the list. For example, the expression, “at least one of a, b, and c,” should be understood as including only a, only b, only c, both a and b, both a and c, both b and c, or all of a, b, and c. 
     Hereinafter, example embodiments will be described in detail with reference to the accompanying drawings. The example embodiments described below are only examples, and thus, it should be understood that the embodiments may be modified in various forms. In the drawings, like reference numerals refer to like elements throughout, and the sizes of elements may be exaggerated for clarity. 
     In the following description, when an element is referred to as being “above” or “on” another element, it may be directly on the other element while making contact with the other element or may be above the other element without making contact with the other element. 
     Although terms such as “first” and “second” are used to describe various elements, these terms are only used to distinguish one element from another element. These terms do not limit elements to having different materials or structures. 
     As used herein, the singular forms “a,” “an,” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. In addition, it will be understood that when a unit is referred to as “comprising” another element, it does not preclude the possibility that one or more other elements may exist or may be added. 
     In the present disclosure, terms such as “unit” or “module” may be used to denote a unit that has at least one function or operation and is implemented with hardware, software, or a combination of hardware and software. 
     An element referred to with the definite article or a demonstrative pronoun may be construed as the element or the elements even though it has a singular form. 
     Operations of a method may be performed in an appropriate order unless explicitly described in terms of order or described to the contrary. In addition, examples or exemplary terms (for example, “such as” and “etc.”) are used for the purpose of description and are not intended to limit the scope of the present disclosure unless defined by the claims. 
     In an example embodiment, SPAD may be a next-generation semiconductor optical device with extremely high efficiency that is sufficient to detect a single photon with a very high gain characteristic of the device. In SPAD, when a voltage higher than a breakdown voltage of the device is applied, free electrons (carriers) are accelerated according to a very large electric field, causing a strong collision with an atom, and as a result, electrons bound to the atom are released, resulting in an impact ionization phenomenon in which the number of free electrons rapidly increases. This is called avalanche amplification, and due to this effect, the number of free electrons generated by photons irradiated from the outside to an image sensor is greatly increased. For example, even when the surrounding environment is very dark or light is irradiated from a very far distance, and only a very fine photon enters the image sensor, it may be recognized as if a lot of photons enter by amplifying these photons. 
     In imaging using photon counting, a two-dimensional image is implemented by measuring the amount of light per pixel by counting the number of photons incident on a pixel for a certain period of time on a time axis by using SPAD. 
     A related-art image sensor generates a two-dimensional image by transmitting, to an external readout circuit, a voltage change generated by accumulating incident photons in floating diffusion (FD) for a certain period of time. On the other hand, the image sensor using photon counting may make conversion into digital information in units of pixels. 
     A pixel for photon counting imaging includes a high-speed photodiode, a pulse generator, and a counter circuit. Each pixel operates independently, and when a photon is incident thereon, a current flows in the high-speed photodiode and a digital pulse is output from the pulse generator. The number of pulses of the digital pulse are continuously accumulated in a counter at a rear end. Therefore, by counting a pulse output of the counter within a given time, a digital value proportional to an amount of incident photons is obtained, and a two-dimensional image may be implemented. Photon counting imaging may implement high-speed shooting and HDR compared to existing image sensor, and a dynamic range of about 120 dB or more may be implemented. 
     In an example embodiment, an image sensor using photon counting arranges a plurality of sub-pixels in one pixel, counts and outputs a plurality of pulse signals generated according to photons incident on each of the sub-pixels, and performs an operation on the output values. Accordingly, pixel values read from the image sensor may not be transmitted to an image processing circuit (ISP) outside the pixel, and operations on the pixel values may be directly performed within the pixel. 
     In an example embodiment, the term “pixel” may be used to refer only to a photodiode that receives light, or to components or integrated circuits implemented in a pixel. For example, the term “pixel” may be used to collectively refer to a photodiode, a pulse generator, and a counter that implement one pixel. 
     In an example embodiment, the term “image sensor” may be used to refer to a photoelectric conversion device that senses light and converts the detected light into an electrical signal. Accordingly, the term “image sensor” may be used to collectively refer to a pixel or a pixel array, or a pixel a pixel circuit. 
       FIG.  1    is a schematic block diagram of an image acquisition apparatus  100  according to an example embodiment. 
     Referring to  FIG.  1   , the image acquisition apparatus  100  may include a pixel array  200  and a controller  300 . 
     A certain number, for example, M×N, of a plurality of pixels  210  may be arranged in the pixel array  200 . Each of the pixels  210  may be driven independently. The pixel array  200  may include peripheral circuits, a vertical scan circuit, a horizontal scan circuit, a read circuit, an output circuit, and a control circuit. The plurality of pixels  210  and the peripheral circuits may be arranged on different layers from each other. For example, a layer on which the plurality of pixels  210  are arranged may be stacked on a chip layer of the readout circuit. In an example embodiment, the pixel  210  is a SPAD and counts a single photon, and thus may have relatively low noise and high dynamic range. 
     In an example embodiment, a plurality of sub-pixels may be arranged in each of the pixels  210  of the pixel array  200 . In the plurality of sub-pixels, the photodiode may be an avalanche photodiode (hereinafter, referred to as an APD) or a SPAD, which operate in a Geiger mode. Here, at least two sub-pixels may be arranged in one pixel  210 . Each of the sub-pixels may have the same size or different sizes. In addition, two sub-pixels may be implemented in which one of the two-sub-pixels may be used for low luminance and the other one may be used for high luminance. Therefore, the light sensing efficiency may be increased even in low luminance, which is an advantage of the SPAD, and the counter that counts photons absorbed by the SPAD may be prevented from overflowing in high luminance. 
     Each pixel  210  may include a photodiode, a pulse generator, a counter, and an operator. In an example embodiment, the pulse generator may generate a pulse signal based on an electrical signal generated according to photons incident on the photodiode. The counter may count the number of pulse signals output from the pulse generator at a certain time and output the pulse signals. The operator may calculate (obtain) and output a counting value obtained by counting photons of each of the sub-pixels. Here, the operation may be any of an addition, a subtraction, a multiplication, and a division, and may be preset. 
     A structure and detailed operation of the pixel  210  or sub-pixels are described below with reference to  FIGS.  2  and  3   . 
     The controller  300  may process operation values for a plurality of sub-pixels output from the pixel array  200 . For example, when a subtraction operation is performed on the plurality of sub-pixels, the controller  300  may perform a phase difference AF by using the subtraction operation. In addition, the controller  300  may generate an image signal by using output values of the plurality of sub-pixels. In this case, an image having a resolution as large as the number of sub-pixels may be obtained even by using a readout circuit having the same size. Here, the output values may include a counting value of a counter of each pixel or sub-pixel and a period of the pulse signal. In an example embodiment, after calculating the counting value of each sub-pixel, the calculation result value may be transmitted to the controller  300 . In addition, the counting values of the counter of each of the sub-pixels may be provided to the controller  300  without calculation. 
       FIG.  2    is a detailed block diagram of an image sensor  210  shown in  FIG.  1   . 
     Referring to  FIG.  2   , the image sensor  210  or one pixel  210  may include two sub-pixels  211  and  214 , two counters  213  and  215  respectively connected to the sub-pixels  211  and  214 , and an operator  216  may perform an operation on counting values of each of the counters  213  and  215 . Each of the sub-pixels  211  and  214  may include a pulse generator that generates a pulse according to photons absorbed by the respective sub-pixels. 
     The image sensor  210  may sense the amount of light by counting the number of photons incident on the pixel for a certain period of time, i.e., an exposure period, by using a trigger pulse induced by the photons. 
     Each of the sub-pixels  211  and  214  may include a photodiode. The photodiode may include an APD or a SPAD, which operate in a Geiger mode. In Geiger mode, a reverse voltage greater than a breakdown voltage may be applied to detect a single photon in the APD. In Geiger mode, because a strength of an electric field applied to an amplification layer is relatively large, even when a relatively small amount of photons are absorbed, a breakdown of an avalanche current occurs and a large current pulse is output, and thus, single photons may be detected. The pulse generator may generate a pulse signal based on an electrical signal generated according to photons incident on the sub-pixels  211  and  214 . The pulse generator may generate a pulse having a frequency according to a light reception frequency of photons. 
     The counters  213  and  215  may output pulse signals by counting the number of the pulse signals. A counting value or counting result value output from the counters  213  and  215  may become a pixel value. Here, the counting value may be the sum of the number of photons input in a frame period. The counters  213  and  215  may temporarily store the counting value and output the counting value according to an external control signal. 
     The operator  216  may perform an operation on the counting values output from the respective counters  213  and  215 . Here, the operation may be any of an addition, a subtraction, a multiplication, and a division, and may be preset in the image sensor  210 . In an example embodiment, the counting values output from the respective counters  213  and  215  may be numerical digital values for the number of photons. The operator  216  may perform an arithmetic operation on the digital values. The operator  216  may include an arithmetic logic unit (hereinafter, referred to as an ALU). The ALU may be designed to perform arithmetic operations on two numbers such as addition and subtraction, and logical operations such as exclusive OR, AND, and OR. The ALU may perform integer-type calculation operations including addition, subtraction, multiplication, and division. In addition, the ALU may perform a bit logic operation and a bit shift operation. 
       FIG.  3    is a circuit diagram of the sub-pixel  211  shown in  FIG.  2   . 
     Referring to  FIG.  3    together, the sub-pixel  211  may include a photodiode. In addition, the pixel  211  may include a SPAD. A cathode electrode of the photodiode  211  may be connected to an operating voltage Vop, and an anode electrode thereof may be connected to an n-channel metal-oxide-semiconductor field-effect transistor (MOSFET) (NMOS) and an input side of a pulse generator  212 . A gate electrode of the NMOS transistor may be connected to a bias voltage Vbias. 
     The pulse generator  212  may include an inverter circuit. An output of the pulse generator  212  may be connected to the counter  213 . 
     The counter  213  may be inn bits, for example, 8 to 12 bits. A size of the counter is not limited thereto, and counters having various sizes may be used according to a pixel size or application of the image sensor  210 . The counter  213  may include a synchronous counter, an asynchronous counter, or an asynchronous ripple counter. The counter  213  may include a D-flip-flop circuit. 
     Referring to  FIG.  3   , when a reverse bias voltage greater than the breakdown voltage is applied to the cathode electrode of the SPAD  211  as the operating voltage Vop, carriers generated by incidence of a single photon cause avalanche amplification so that a large current is applied to the input side of the pulse generator  212  through the SPAD  211 . 
     The pulse generator  212  may generate an electrical signal applied to the input side thereof, as a pulse signal. Here, the pulse generator  212  may include an inverter circuit. 
     By applying a bias voltage to the gate electrode of the NMOS transistor, the NMOS transistor may be turned and off, and a current generated in the SPAD  211  may be transferred to the pulse generator  212 . Here, although the NMOS transistor is shown, embodiments are not limited thereto, and various bias voltage application circuits may be applied. 
     A quenching circuit for limiting excessive current caused by avalanche amplification generated in the SPAD  211  may be further included. As the reverse voltage applied to the SPAD increases, a probability that thermal electrons are in an excited state and a tunneling probability increase, and thus, a dark current in which an avalanche current is generated increases even without photon absorption. When the avalanche current is generated, an excess current may flow. Therefore, a continuous flow of the avalanche current may be suppressed by the quenching circuit. 
       FIG.  4    is a detailed block diagram of the image sensor  210  including a plurality of sub-pixels according to another example embodiment. 
     Referring to  FIG.  4   , a pixel structure is shown in which one pixel includes a plurality of sub-pixels, and each of the sub-pixels may convert information corresponding to the amount of light into a digital value by photon counting and calculate and output a result value. 
     Two sub-pixels  211  and  214  may be arranged in the one pixel, and the sub-pixels  211  and  214  and the counters  213  and  215  are respectively connected to each other. Accordingly, pulse signals generated by photons absorbed in the sub-pixel  211  may be counted by the counter  213 , and pulse signals generated by photons absorbed in the sub-pixel  214  may be counted by the counter  215 . Counting values (the respective sub-pixel values) counted by the counters  213  and  215  may be input to the operator  216 . 
     The operator  216  may perform an arithmetic operation and output the result value to the outside of the pixel. Here, the operation may be any of an addition, a subtraction, a multiplication, and a division, and any combinations thereof. 
     In an example embodiment, a type of operation within the pixel may be preset, and the type of operation may vary according to the application of the image sensor  210 . For example, when used in dual photodiode autofocus (hereinafter, referred to as “2PDAF”) or phase difference autofocus (PDAF), the operation is to perform an AF from a difference (phase difference) between pixel values of the respective sub-pixels, and thus, a subtraction operation may be performed. When a PDAF function is to be performed, two sub-pixels are provided, and the subtraction operation is performed. Therefore, because an in-pixel operation is possible without external ISP support, faster results may be obtained and an improved autofocusing function is possible. 
       FIG.  5    is a circuit diagram of a pixel array including a plurality of sub-pixels according to another example embodiment. 
     Referring to  FIG.  5   , a circuit design for performing a PDAF using 9 pixels each including two sub-pixels is shown. Here, the circuit design is only an example, and is not limited thereto. 
     In AF using PDAF, a difference in the amount of light incident on two individual sub-pixels in one pixel including two sub-pixels may be used. A position of a lens may be optimized by using the information to form a focus on a two-dimensional (2D) array surface so that clear image information may be ensured. A case of having a structure using the proposed method in order to perform these functions is described below. 
     First, because each pixel has an operation function, it is set as to which operation is to be performed. When the setting is completed, exposure and readout functions of the image sensor may be performed in the same way. Here, because the image information outputs a value for which “A-B” calculation is completed, AF may be completed by optimizing the position of a camera lens without additional ISP processing. 
     In  FIG.  5   , in order to perform PDAF by using two sub-pixels, a result value of a subtraction operation is output. However, embodiments are not limited thereto, and result values of various operations may be output. 
     In another example embodiment, a plurality of sub-pixels are arranged in a pixel, and thus, an arithmetic operation may be performed. However, information about the sub-pixels may be individually used. For example, a pixel structure including two sub-pixels may have an M×N array in units of pixels. Here, when the sub-pixels are individually used, image information having a 2×M×N resolution may be obtained. For example, although a readout circuit has an M×N resolution, an image may have an amount of information or resolution that is twice that of an image output from the image sensor. 
       FIG.  6    is a schematic block diagram of an image acquisition apparatus according to another example embodiment. 
     Referring to  FIG.  6   , the image acquisition apparatus may include an image sensor  600  and a processor  610 . 
     The image sensor  600  may include a plurality of sub-pixels arranged in one pixel, a plurality of counters which are respectively connected to the sub-pixels and count and output a plurality of pulse signals generated according to photons incident on each of the sub-pixels, and an operator that performs an operation on output values output from each of the counters. 
     The processor  610  may process operation values output from the operator of the image sensor  600 . Because the operation values include pixel values of the respective sub-pixels, desired operation values may be directly obtained by using various preset operation methods. Accordingly, the calculated pixel values may be used in the processor  610  without a separate operation. 
     In an example embodiment, the processor  610  may set an arithmetic operation of the image sensor  600  to suit a desired application. 
     In an example embodiment, the processor  610  may control to output only a pixel value of any sub-pixel from among the plurality of sub-pixels of the image sensor  600 . For example, in a case in which the plurality of sub-pixels have different sizes from one another, where one is for a relatively low luminance and the other one is for a relatively high luminance, when it is determined to be a low luminance situation, the processor  610  may control to output only a pixel value of the sub-pixel for low luminance. 
     In an example embodiment, the processor  610  may control pixel values of the plurality of sub-pixels of the image sensor  600  to be individually output. In this case, an operation of the operator may be turned off, and an output value of each of the sub-pixels may be output. In this case, when the image sensor  600  is implemented as M×N pixel arrays, and K pixel arrays are included in one sub-pixel, the obtained image may have a resolution of K×M×N. 
       FIG.  7    is a schematic block diagram of an image acquisition apparatus according to another example embodiment. 
     Referring to  FIG.  7   , the image acquisition apparatus may include the image sensor  600  and the processor  610 , and the processor  610  may include an image signal processing unit  611  and an AF performance unit  612 . 
     The image signal processing unit  611  may generate an image signal based on a pixel value obtained from the image sensor  600 . After obtaining an image from the image sensor  600 , the image signal processing unit  611  may perform basic image processing before or after the image is stored in a memory. For example, the ISP may perform bad pixel correction, fixed pattern noise correction, crosstalk reduction, remosaicing, demosaicing, false color reduction, denoising, chromatic aberration correction, or the like. 
     The AF performance unit  612  may focus by moving the position of the lens based on a pixel difference value of each of the sub-pixels obtained from the image sensor  600 . In an example embodiment, even when the pixel difference value is operated within the processor  610 , the pixel difference values may be directly received from the image sensor  600  to perform AF, and thus, fast AF may be implemented. 
       FIGS.  8  and  9    are diagrams illustrating a phase difference AF according to another example embodiment. Referring to  FIG.  8   , a related-art PDAF is shown. As an AF method of a camera, contrast detection autofocus (CDAF), phase detection autofocus (PDAF), and laser AF may be mainly used. In an example embodiment, the AF method is PDAF, and as shown in  FIG.  8   , a sensor structure including two individual pixels in a sensor may be required. The camera performs a focusing function in order to ensure clear image quality for an object. In the PDAF method, individual information within a pixel may be transmitted to an external circuit so that calculation is performed by using an ISP, and a lens position of the camera may be optimized by using the result value. 
     Referring to  FIG.  9   , the 2PDAF method is shown. The 2PDAF method is a method of using individual pixels of a sensor to operate a focus of a camera at high speed. As shown in  FIG.  9   , AF may be performed by dividing a pixel into two sub-pixels and comparing the amount of light incident on the sub-pixels with each other. 
     In the method described with reference to  FIGS.  8  and  9   , a series of operations of reading out in-pixel information, converting analog information into digital information, and performing calculation by using an ISP requires a processing time and power consumption. 
     Because digital information is generated in a pixel by using photon counting according to an example embodiment and an operation is performed thereon, PDAF may be performed without the help of an existing external ISP. Thus, the AF speed may be improved, and power consumption of the image acquisition apparatus may be reduced. 
     The image acquisition apparatus  1000  described above may be employed in various high-performance optical devices or high-performance electronic apparatuses. Examples of the electronic apparatuses may include smartphones, mobile phones, cellular phones, personal digital assistants (PDAs), laptop computers, personal computers (PCs), various portable devices, home appliances, security cameras, medical cameras, automobiles, Internet of Things (IoT) devices, and mobile or non-mobile computing devices, but are not limited thereto. 
     In addition to the image acquisition apparatus  1000 , the electronic apparatus may further include a processor for controlling image sensors provided therein, for example, an application processor (AP), may control a plurality of hardware or software components by driving an operating system or an application program through a processor, and may perform various data processing and operations. The processor may further include a graphics-processing unit (GPU) and/or an image signal processor. When the processor includes an image signal processor, an image (or video) obtained by the image sensor may be stored and/or output using the processor. 
       FIG.  10    is a block diagram including a schematic structure of an electronic apparatus ED 01  according to an embodiment. Referring to  FIG.  10   , in a network environment ED 00 , the electronic apparatus ED 01  may communicate with another electronic apparatus ED 02  through a first network ED 98  (a near-field wireless communication network or the like) or may communicate with another electronic apparatus ED 04  and/or a server ED 08  through a second network ED 99  (a far-field wireless communication network or the like). The electronic apparatus ED 01  may communicate with the electronic apparatus ED 04  through the server ED 08 . The electronic apparatus ED 01  may include a processor ED 20 , a memory ED 30 , an input device ED 50 , a sound output device ED 55 , a display device ED 60 , an audio module ED 70 , a sensor module ED 76 , an interface ED 77 , a haptic module ED 79 , a camera module ED 80 , a power management module ED 88 , a battery ED 89 , a communication module ED 90 , a subscriber identification module ED 96 , and/or an antenna module ED 97 . Some (the display device ED 60 , etc.) of the components may be omitted from the electronic apparatus ED 01 , or other components may be added to the electronic apparatus ED 01 . Some of the components may be implemented in one integrated circuit. For example, the sensor module ED 76  (a fingerprint sensor, an iris sensor, an illuminance sensor, etc.) may be embedded in the display device ED 60  (a display or the like). In addition, when an image sensor has a spectral function, some sensor-module functions (color sensing, illuminance sensing, etc.) may be implemented in the image sensor instead of being implemented in the sensor module ED 76 . 
     The processor ED 20  may execute software (a program ED 40  or the like) to control one or more other components (hardware or software components, etc.) of the electronic apparatus ED 01  connected to the processor ED 20 , and may perform a variety of data processing or operations. As a portion of the data processing or operations, the processor ED 20  may load instructions and/or data received from other components (the sensor module ED 76 , the communication module ED 90 , etc.) into a volatile memory ED 32 , process the instructions and/or data stored in the volatile memory ED 32 , and store result data in a nonvolatile memory ED 34 . The processor ED 20  may include a main processor ED 21  (a central processing unit, an application processor, or the like) and an auxiliary processor ED 23  (a GPU, an ISP, a sensor hub processor, a communication processor, or the like), which is operated independently or together with the main processor ED 21 . The auxiliary processor ED 23  may consume less power than the main processor ED 21  and may perform specialized functions. 
     The auxiliary processor ED 23  may control functions and/or states related to some (the display device ED 60 , the sensor module ED 76 , the communication module ED 90 , etc.) of the components of the electronic apparatus ED 01  on behalf of the main processor ED 21  while the main processor ED 21  is in an inactive (e.g., sleep) state or together with the main processor ED 21  while the main processor ED 21  is in an active (e.g., application execution) state. The auxiliary processor ED 23  (an ISP, a communication processor or the like) may be implemented as a portion of other functionally relevant components (the camera module ED 80 , the communication module ED 90 , etc.). 
     The memory ED 30  may store a variety of data required by the components (the processor ED 20 , the sensor module ED 76 , etc.) of the electronic apparatus ED 01 . The data may include, for example, software (the program ED 40 , etc.) and input data and/or output data for commands related thereto. The memory ED 30  may include the volatile memory ED 32  and/or the nonvolatile memory ED 34 . The nonvolatile memory ED 32  may include an internal memory ED 36  fixed to the electronic apparatus ED 01  and an external memory ED 38  removable from the electronic apparatus ED 01 . 
     The program ED 40  may be stored as software in the memory ED 30 , and may include an operating system ED 42 , middleware ED 44 , and/or an application ED 46 . 
     The input device ED 50  may receive commands and/or data to be used for the components (the processor ED 20 , etc.) of the electronic apparatus ED 01  from the outside (a user, etc.) of the electronic apparatus ED 01 . The input device ED 50  may include a microphone, a mouse, a keyboard, and/or a digital pen (a stylus pen or the like). 
     The audio output device ED 55  may output an audio signal to the outside of the electronic apparatus ED 01 . The audio output device ED 55  may include a speaker and/or a receiver. The speaker may be used for general purposes such as multimedia playback or record playback, and the receiver may be used to receive incoming calls. The receiver may be provided as a portion of the speaker or may be implemented as a separate device. 
     The display device ED 60  may visually provide information to the outside of the electronic apparatus ED 01 . The display device ED 60  may include a display, a hologram device, or a projector, and a control circuit for controlling devices. The display device ED 60  may include touch circuitry set to sense a touch, and/or sensor circuitry (a pressure sensor, etc.) configured to measure the intensity of force generated by the touch. 
     The audio module ED 70  may convert sound into an electrical signal, and vice versa. The audio module ED 70  may obtain sound through the input device ED 50 , or may output sound through the audio output device ED 55  and/or speakers and/or headphones of another electronic apparatus (the electronic apparatus ED 02  or the like) directly or wirelessly connected to the electronic apparatus ED 01 . 
     The sensor module ED 76  may detect an operating state (power, temperature, etc.) of the electronic apparatus ED 01  or an external environmental state (user status, etc.), and may generate an electrical signal and/or a data value corresponding to the detected state. The sensor module ED 76  may include a gesture sensor, a gyro sensor, a barometric sensor, a magnetic sensor, an acceleration sensor, a grip sensor, a proximity sensor, a color sensor, an infrared (IR) sensor, a biological sensor, a temperature sensor, a humidity sensor, and/or an illuminance sensor. 
     The interface ED 77  may support one or more designated protocols, which may be used to directly or wirelessly connect the electronic apparatus ED 01  with other electronic apparatuses (the electronic apparatus ED 02 , etc.). The interface ED 77  may include a high definition multimedia interface (HDMI), a universal serial bus (USB) interface, a secure digital (SD) card interface, and/or an audio interface. 
     A connection terminal ED 78  may include a connector through which the electronic apparatus ED 01  may be physically connected to other electronic apparatuses (the electronic apparatus ED 02 , etc.). The connection terminal ED 78  may include an HDMI connector, a USB connector, an SD card connector, and/or an audio connector (a headphone connector, etc.). 
     The haptic module ED 79  may convert an electrical signal into a mechanical stimulus (vibration, movement, etc.) or an electrical stimulus that a user may perceive through tactile sensation or kinesthesia. The haptic module ED 79  may include a motor, a piezoelectric element, and/or an electric stimulation device. 
     The camera module ED 80  may capture a still image and a moving image. The camera module ED 80  may include the image acquisition apparatus  1000  described above, and may further include a lens assembly, an ISP, and/or a flash. The lens assembly included in the camera module ED 80  may collect light coming from an object to be imaged. 
     The power management module ED 88  may manage power supplied to the electronic apparatus ED 01 . The power management module ED 88  may be implemented as a portion of a power management integrated circuit PMIC. 
     The battery ED 89  may supply power to components of the electronic apparatus ED 01 . The battery ED 89  may include a non-rechargeable primary battery, a rechargeable secondary battery, and/or a fuel cell. 
     The communication module ED 90  may support establishment of a direct (wired) communication channel and/or a wireless communication channel between the electronic apparatus ED 01  and other electronic apparatuses (the electronic apparatus ED 02 , the electronic apparatus ED 04 , the server ED 08 , etc.), and communication through the established communication channel. The communication module ED 90  operates independently of the processor ED 20  (an application processor, etc.) and may include one or more communication processors supporting direct communication and/or wireless communication. The communication module ED 90  may include a wireless communication module ED 92  (a cellular communication module, a short-range wireless communication module, a global navigation satellite system (GNSS), or the like) and/or a wired communication module ED 94  (a local area network (LAN) communication module, a power line communication module, or the like). A corresponding communication module from among these communication modules may communicate with other electronic apparatuses through the first network ED 98  (a local area network such as Bluetooth, WiFi Direct, or infrared data association (IrDA)) or the second network ED 99  (a telecommunication network such as a cellular network, the Internet, or computer networks (LAN, WAN, etc.)). These various types of communication modules may be integrated into a single component (a single chip or the like) or may be implemented as a plurality of separate components (multiple chips). The wireless communication module ED 92  may identify and authenticate the electronic apparatus ED 01  within a communication network such as the first network ED 98  and/or the second network ED 99  using subscriber information (an international mobile subscriber identifier (IMSI), etc.) stored in the subscriber identification module ED 96 . 
     The antenna module ED 97  may transmit and/or receive signals and/or power to and/or from the outside (other electronic apparatuses, etc.). An antenna may include a radiator made of a conductive pattern formed on a substrate (a PCB, etc.). The antenna module ED 97  may include one or more such antennas. When a plurality of antennas are included in the antenna module ED 97 , the communication module ED 90  may select an antenna suitable for a communication method used in a communication network, such as the first network ED 98  and/or the second network ED 99 , among the plurality of antennas. Signals and/or power may be transmitted or received between the communication module ED 90  and other electronic apparatuses through the selected antenna. Other components (an RFIC, etc.) besides the antenna may be included as part of the antenna module ED 97 . 
     Some of the components may be connected to each other and exchange signals (commands, data, etc.) through a communication method between peripheral devices (a bus, general purpose input and output (GPIO), a serial peripheral interface (SPI), a mobile industry processor interface (MIPI), or the like). 
     Commands or data may be transmitted or received between the electronic apparatus ED 01  and an external apparatus such as the electronic apparatus ED 04  through the server ED 08  connected to the second network ED 99 . The other electronic apparatuses ED 02  and ED 04  may be the same as or different from the electronic apparatus ED 01 . All or some of the operations of the electronic apparatus ED 01  may be executed by one or more of the other electronic apparatuses ED 02 , ED 04 , and ED 08 . For example, when the electronic apparatus ED 01  needs to perform certain functions or services, the electronic apparatus ED 01  may request one or more other electronic apparatuses to perform some or all of the functions or services instead of directly executing the functions or services. One or more other electronic apparatuses that have received the request may execute an additional function or service related to the request, and may transfer results of the execution to the electronic apparatus ED 01 . To this end, cloud computing, distributed computing, and/or client-server computing techniques may be used. 
       FIG.  11    is a block diagram schematically illustrating the camera module ED 80  included in the electronic apparatus ED 01  shown in  FIG.  10   . The camera module ED 80  may include the image acquisition apparatus  1000  described above, or may have a structure modified therefrom. Referring to  FIG.  11   , the camera module ED 80  may include a lens assembly CM 10 , a flash CM 20 , an image sensor CM 30 , an image stabilizer CM 40 , a memory CM 50  (a buffer memory, etc.), and/or an ISP CM 60 . 
     The image sensor CM 30  is an image sensor described with reference to  FIGS.  1  to  3   , and includes a plurality of sub-pixels arranged in one pixel, a plurality of counters which are respectively connected to the sub-pixels and count and output a plurality of pulse signals generated according to photons incident on the respective sub-pixels, and an operator that performs an operation on an output value output from each of the counters. Accordingly, by using photon counting technology, the image sensor CM 30  may directly perform an operation on pixel values in a pixel without transmitting a pixel value read from the image sensor CM 30  to an ISP outside the pixel. In addition, by performing, in a pixel, a processing operation in which pixel values may be operated, for example, a pixel value operation for 2PDAF, the AF speed may be improved, and power consumption of the image acquisition apparatus may be reduced. In addition, by including a plurality of sub-pixels, the individual sub-pixels may be selectively driven to obtain a pixel value, and thereby an image having a resolution as large as the number of sub-pixels may be obtained even by using a readout circuit having the same size. 
     The lens assembly CM 10  may collect light coming from an object to be imaged. The camera module ED 80  may include a plurality of lens assemblies CM 10 , and in this case, the camera module ED 80  may be a dual camera, a 360-degree camera, or a spherical camera. Some of the plurality of lens assemblies CM 10  may have the same lens properties (field of view, focal length, autofocus, F Number, optical zoom, etc.) or different lens properties. Each of the lens assemblies CM 10  may include a wide-angle lens or a telephoto lens. 
     The lens assembly CM 10  may be configured and/or focused such that an image sensor included in the image sensor CM 30  may form optical images of an object. 
     The flash CM 20  may emit light used to enhance light emitted or reflected from an object. The flash CM 20  may include one or more light emitting diodes (a red-green-blue (RGB) LED, a white LED, an infrared LED, an ultraviolet LED, etc.), and/or a xenon lamp. 
     The image stabilizer CM 40  may move one or more lenses included in the lens assembly CM 10  or the image sensor CM 30  in a specific direction in response to a movement of the camera module ED 80  or the electronic apparatus ED 01  including the camera module ED 80 , or may control operating characteristics of the image sensor CM 30  (adjustment of read-out timing, etc.) to compensate for negative effects caused by movement. The image stabilizer CM 40  may detect a movement of the camera module ED 80  or the electronic apparatus ED 01  by using a gyro sensor (not shown) or an acceleration sensor (not shown) arranged inside or outside the camera module ED 80 . The image stabilizer CM 40  may be an optical image stabilizer. 
     In the memory CM 50 , some or all of data obtained through the image sensor CM 30  may be stored for the next image processing operation. For example, when a plurality of images are obtained at a high speed, the obtained original data (Bayer-patterned data, high-resolution data, or the like) may be stored in the memory CM 50  and only a low-resolution image may be displayed. Then, the original data of a selected image (user selection, etc.) may be transferred to the ISP CM 60 . The memory CM 50  may be integrated into the memory ED 30  of the electronic apparatus ED 01  or may be configured as a separate memory that may be independently operated. 
     The ISP CM 60  may perform one or more image processes on an image obtained through the image sensor CM 30  or image data stored in the memory CM 50 . 
     In addition, the one or more image processes may include depth map generation, three-dimensional modeling, panorama generation, feature point extraction, image synthesis, and/or image compensation (noise reduction, resolution adjustment, brightness adjustment, blurring, sharpening, softening, etc.). The ISP CM 60  may control (exposure time control, read-out timing control, etc.) components (the image sensor CM 30 , etc.) included in the camera module CM 80 . An image processed by the ISP CM 60  may be stored again in the memory CM 50  for additional processing or may be provided to external components (the memory ED 30 , the display device ED 60 , the electronic apparatus ED 02 , the electronic apparatus ED 04 , the server ED 08 , etc.) of the camera module ED 80 . The ISP CM 60  may be integrated into the processor ED 20  or may be configured as a separate processor that operates independently of the processor ED 20 . When the ISP CM 60  is provided separately from the processor ED 20 , an image processed by the ISP CM 60  may be displayed on the display device ED 60  after being further processed by the processor ED 20 . 
     The electronic apparatus ED 01  may include a plurality of camera modules ED 80  having different attributes or functions. In this case, one of the plurality of camera modules ED 80  may be a wide-angle camera, and another of the plurality of camera modules ED 80  may be a telephoto camera. Similarly, one of the plurality of camera modules ED 80  may be a front camera, and another of the plurality of camera modules ED 80  may be a rear camera. 
       FIGS.  11  to  21    are views illustrating various examples of an electronic apparatus including the image acquisition apparatus  1000  according to example embodiments. 
     According to example embodiments, the image acquisition apparatus  1000  may be applied to a mobile phone or smartphone  5100   m  shown in  FIG.  12   , a tablet or smart tablet  5200  shown in  FIG.  13   , a digital camera or camcorder  5300  shown in  FIG.  14   , a laptop computer  5400  shown in  FIG.  15   , or a television or smart television  5500  shown in  FIG.  19   . For example, the smartphone  5100   m  or the smart tablet  5200  may include a plurality of high-resolution cameras each having a high-resolution image sensor mounted thereon. The high-resolution cameras may be used to extract depth information of objects in an image, adjust out of focus of an image, or automatically identify objects in an image. 
     In addition, the image acquisition apparatus  1000  may be applied to a smart refrigerator  5600  shown in  FIG.  17   , a security camera  5700  shown in  FIG.  18   , a robot  5800  shown in  FIG.  19   , a medical camera  5900  shown in  FIG.  20   , and the like. For example, the smart refrigerator  5600  may automatically recognize food contained in the smart refrigerator  5600  by using the image acquisition apparatus  1000 , and may inform a user of whether a specific food is contained in the smart refrigerator  5600 , the type of food put into or out of the smart refrigerator  5600 , and the like through a smartphone. The security camera  5700  may provide an ultra-high-resolution image and may recognize an object or a person in the ultra-high-resolution image even in a dark environment owing to high sensitivity of the security camera  5700 . The robot  5800  may be sent to a disaster or industrial site that cannot be directly accessed by humans and may provide high-resolution images. The medical camera  5900  may provide a high-resolution image for diagnosis or surgery, and may have a dynamically adjustable field of view. 
     In addition, the image acquisition apparatus  1000  may be applied to a vehicle  6000  as shown in  FIG.  21   . The vehicle  6000  may include a plurality of vehicle cameras  6010 ,  6020 ,  6030 , and  6040  arranged at various positions. Each of the vehicle cameras  6010 ,  6020 ,  6030 , and  6040  may include an image acquisition apparatus according to an embodiment. The vehicle  6000  may use the vehicle cameras  6010 ,  6020 ,  6030 , and  6040  to provide a driver with various information about the interior or surroundings of the vehicle  6000 , and may provide information necessary for autonomous driving by automatically recognizing objects or people in images. 
     According to an example embodiment, by using photon counting technology, the image sensor may directly perform an operation on pixel values in a pixel without transmitting a pixel value read from the image sensor CM 30  to an ISP outside the pixel. 
     In addition, by performing, in a pixel, a processing operation in which pixel values may be operated, for example, a pixel value operation for 2PDAF, the AF speed may be improved, and power consumption of the image acquisition apparatus may be reduced. 
     In addition, by including a plurality of sub-pixels, the individual sub-pixels may be selectively driven to obtain a pixel value, and thereby an image having a resolution as large as the number of sub-pixels may be obtained even by using a readout circuit having the same size. 
     It should be understood that example embodiments described herein should be considered in a descriptive sense only and not for purposes of limitation. Descriptions of features or aspects within each example embodiment should typically be considered as available for other similar features or aspects in other embodiments. While example embodiments have been described with reference to the figures, it will be understood by those of ordinary skill in the art that various changes in form and details may be made therein without departing from the spirit and scope as defined by the following claims and their equivalents.