KR20140136291A - Imaging device and method for driving thereof - Google Patents

Abstract

An imaging device disclosed by the present invention includes: a pixel which includes a photoelectric conversion element, a shift switching unit arranged in one side of the photoelectric conversion element, a first electric charge storage unit arranged in one side of the shift switching unit, a transfer switching unit arranged in one side of the first electric charge storage unit, a second electric charge storage unit arranged in one side of the transfer switching unit, and a reset switching unit arranged in one side of the second electric charge storage unit; and a control circuit which applies a signal on the pixel. In the imaging device, the control circuit is able to perform: a first reading operation of reading the quantity of an electric charge stored in the photoelectric conversion element; a second reading operation of reading the quantity of an electric charge stored in the first electric charge storage unit by overflowing from the photoelectric conversion element to the first electric charge storage unit; and a third reading operation of reading the quantity of an electric charge which overflows from the first electric charge storage unit to the second electric charge storage unit.

Description

[0001] IMAGING DEVICE AND METHOD FOR DRIVING THEREOF [0002]

The present invention relates to an imaging apparatus and a driving method thereof, and more particularly, to an imaging apparatus and a driving method thereof, which can achieve high sensitivity sensitivity at low illumination and at the same time realize high sensitivity sensitivity at a high degree of illumination .

In addition, the present invention can be applied to an image pickup apparatus capable of selectively driving a high sensitivity characteristic even at a low light level and a high image level, or a global shutter suitable for image pickup of a fast moving subject, An imaging apparatus and a driving method thereof.

The image sensor operates in such a manner that when a unit pixel receives incident light and converts it into charge, a voltage signal corresponding thereto is generated and output. For example, one of the parameters representing the performance of a complementary metal oxide semiconductor (CMOS) image sensor is the dynamic range (DR), which is the maximum input signal that does not saturate the CMOS image sensor, Can be expressed as a ratio of the minimum input signal that can be obtained.

However, the conventional color image sensor has a disadvantage in that it can not display the original color of the image well when the dynamic range is narrow and at least one of red, green, and blue is saturated. In order to overcome the disadvantage that the dynamic range is narrow, a method of implementing a wide dynamic range (WDR) pixel is proposed.

In particular, in order to increase the dynamic range of a CMOS image sensor in the related art, it is necessary to increase the charge storage capacity, i.e., the well capacity, of the photoelectric conversion region included in the CMOS image sensor, (FPN), and so on.

In addition, when photographing a subject moving by an image sensor, a rolling shutter (not shown) for sequentially shifting charges accumulated in a photoelectric conversion unit (for example, a photodiode) provided in a pixel array in a column unit or row, when the subject is photographed using a shutter, the image is distorted. Therefore, in order to photograph a subject with such a fast motion, a subject is photographed according to a global shutter method which simultaneously shifts the charges accumulated in the photoelectric conversion unit provided in the pixel array.

However, the pixels for realizing the wide dynamic range have difficulties in photographing the subject according to the global shutter method. Accordingly, image sensors have conventionally been used in a dual mode, such as using an image sensor suitable for a global shutter system or an image sensor suitable for realizing a wide dynamic range depending on an environment in which an image sensor is used .

An object of the present invention is to provide an imaging apparatus and a driving method thereof suitable for realizing a wide dynamic range.

Another object of the present invention is to provide an imaging apparatus and a driving method thereof that are suitable for a global shutter while realizing a wide dynamic range.

An imaging apparatus according to an embodiment of the present invention includes a photoelectric conversion element, a shift switching unit disposed at one side of the photoelectric conversion element, a first charge storage unit disposed at one side of the shift switching unit, And a reset switching unit disposed at one side of the second charge storage unit, wherein the transfer switch unit is disposed on the first charge storage unit, the second charge storage unit is disposed on one side of the transfer switch unit, and the reset switch unit is disposed on one side of the second charge storage unit. And a control circuit for applying a signal to the pixel, wherein the control circuit includes: a first read operation for reading an amount of charge stored in the photoelectric conversion element; a second read operation for overflowing from the photoelectric conversion element to the first charge storage part, A second reading operation for reading the amount of charge stored in the one charge storage unit and a third reading operation for reading the amount of the overflow from the first charge storage unit to the second charge storage unit.

The first reading operation may include an operation of moving the charge stored in the photoelectric conversion element to the second charge storage portion through the first charge storage portion.

The second read operation may include an operation of moving charges stored in the first charge storage unit overflow from the photoelectric conversion element to the first charge storage unit to the second charge storage unit and reading the same.

The second charge storage unit may be a floating diffusion node.

The control circuit may not turn on the transfer switching unit before performing the third read operation after the photoelectric conversion element is reset.

The control circuit may not operate the shift switching unit before performing the second read operation after the photoelectric conversion element is reset.

The control circuit may perform the second read operation after performing the third read operation and may perform the first read operation after performing the second read operation.

The first accumulation time for accumulating the amount of charge read by the first reading operation is longer than the second accumulation time for accumulating the amount of charge read by the second reading operation. At this time, the second accumulation time may be selected in a range of 1/5000 or more of the first accumulation time and 1/5 or less of the first accumulation time.

The second accumulation time for accumulating the amount of charge read by the second reading operation is longer than the third accumulation time for accumulating the amount of charge read by the third reading operation. At this time, the third accumulation time may be selected in a range of 1/5000 or more of the second accumulation time and 1/5 or less of the first accumulation time.

According to the present invention, the following effects occur.

First, by controlling the potential barrier formed by the overflow control unit and the potential barrier formed by the shift switching unit differently according to the set operation mode, the operation for the wide dynamic range implementation using the same pixel array And the operation for the global shutter can be selectively implemented.

Second, in the implementation of the wide dynamic range, by using at least a part of the charges overflowing from the photoelectric conversion element to the first charge storage section, the wide dynamic range can be easily realized.

Third, by implementing at least a portion of the charges overflowing from the first charge storage to the floating diffusion region, as well as using at least some of the charges overflowing from the photoelectric conversion element to the first charge storage in the implementation of the wide dynamic range , It is possible not only to easily implement the wide dynamic range but also to photograph the image in a wider dynamic range.

Fourth, it is possible to automatically set / set an operation mode based on some images obtained, so that an appropriate operation mode can be set more easily.

1 is a block diagram illustrating an imaging apparatus in accordance with an embodiment of the present invention.
2 is a diagram showing a circuit of a unit pixel of an imaging apparatus according to an embodiment of the present invention.
3 is a flowchart for explaining a driving method of an imaging apparatus according to an embodiment of the present invention.
4 is a timing chart for explaining a method of driving a pixel array of an imaging apparatus in a first mode according to an embodiment of the present invention.
5 is a timing diagram of control signals applied to the respective components of the unit pixel of the imaging apparatus in the first mode according to an embodiment of the present invention.
6 is a diagram showing a potential barrier for explaining charge transfer of a unit pixel of an imaging apparatus in a first mode according to an embodiment of the present invention.
7 is a timing chart for explaining a method of driving a pixel array of an imaging apparatus in a second mode according to an embodiment of the present invention.
8 is a timing diagram of control signals applied to the respective components of the unit pixel of the imaging apparatus in the second mode according to an embodiment of the present invention.
Figure 9 is a diagram illustrating a potential barrier for describing charge transfer within a unit pixel of an imaging device in a second mode according to an embodiment of the present invention.
10 is a flowchart illustrating a method of selecting an operation mode according to an embodiment of the present invention.
11 is a diagram showing an example of an image histogram for explaining a method of selecting an operation mode according to an embodiment of the present invention.
12 is a timing chart for explaining a method of driving a pixel array of an imaging apparatus according to another embodiment of the present invention.
13 is a timing chart of control signals applied to the respective components of the unit pixel of the imaging apparatus according to another embodiment of the present invention.
14 is a diagram showing a potential barrier for explaining charge transfer in a unit pixel of an imaging apparatus according to another embodiment of the present invention.

For the embodiments of the invention disclosed herein, specific structural and functional descriptions are set forth for the purpose of describing an embodiment of the invention only, and it is to be understood that the embodiments of the invention may be practiced in various forms, The present invention should not be construed as limited to the embodiments described in Figs.

The present invention is capable of various modifications and various forms, and specific embodiments are illustrated in the drawings and described in detail in the text. It is to be understood, however, that the invention is not intended to be limited to the particular forms disclosed, but on the contrary, is intended to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the invention.

The terms first, second, etc. may be used to describe various components, but the components should not be limited by the terms. The terms may be used for the purpose of distinguishing one component from another. For example, without departing from the scope of the present invention, the first component may be referred to as a second component, and similarly, the second component may also be referred to as a first component.

It is to be understood that when an element is referred to as being "connected" or "connected" to another element, it may be directly connected or connected to the other element, . On the other hand, when an element is referred to as being "directly connected" or "directly connected" to another element, it should be understood that there are no other elements in between. Other expressions that describe the relationship between components, such as "between" and "between" or "neighboring to" and "directly adjacent to" should be interpreted as well.

The terminology used in this application is used only to describe a specific embodiment and is not intended to limit the invention. The singular expressions include plural expressions unless the context clearly dictates otherwise. In the present application, the terms "comprise", "having", and the like are intended to specify the presence of stated features, integers, steps, operations, elements, components, or combinations thereof, , Steps, operations, components, parts, or combinations thereof, as a matter of principle.

Unless otherwise defined, all terms used herein, including technical or scientific terms, have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. Terms such as those defined in commonly used dictionaries should be construed as meaning consistent with meaning in the context of the relevant art and are not to be construed as ideal or overly formal in meaning unless expressly defined in the present application .

On the other hand, if an embodiment is otherwise feasible, the functions or operations specified in a particular block may occur differently from the order specified in the flowchart. For example, two consecutive blocks may actually be performed at substantially the same time, and depending on the associated function or operation, the blocks may be performed backwards.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. The same reference numerals are used for the same constituent elements in the drawings and redundant explanations for the same constituent elements are omitted.

1. Structure of Imaging Device

1 is a block diagram illustrating an imaging apparatus in accordance with an embodiment of the present invention.

Referring to FIG. 1, an imaging apparatus 100 according to an exemplary embodiment of the present invention includes a photoelectric conversion unit 110 and a control circuit 120.

The photoelectric conversion unit 110 converts the incident light into an electrical signal. The photoelectric conversion unit 110 may include a pixel array 111 in which unit pixels are arranged in a matrix form. The unit pixels included in the pixel array 111 will be described later. According to the embodiment, the photoelectric conversion unit 110 may further include an infrared filter and / or a color filter.

The control circuit 120 includes a row driver 121, a correlated double sampling (CDS) unit 122, an analog-to-digital converting (ADC) unit 123 and a timing controller 129 ).

A row driver 121 is connected to each row of the pixel array 111 and generates a driving signal for driving each row. For example, the row driver 121 may drive a plurality of unit pixels included in the pixel array 111 in a row unit.

The CDS unit 122 calculates a difference between a reference voltage representing a reset state of the unit pixels and an output voltage representing a signal component corresponding to an incident light by using a capacitor, a switch, and the like, performs correlated double sampling, And outputs an analog sampling signal. The CDS unit 122 includes a plurality of CDS circuits respectively connected to the column lines of the pixel array 111 and is capable of outputting an analog sampling signal corresponding to the valid signal component for each column.

The ADC unit 123 converts an analog image signal corresponding to the valid signal component into a digital image signal. The ADC unit 123 includes a reference signal generator 124, a comparison unit 125, a counter 126, and a buffer unit 127. The reference signal generator 124 generates a reference signal, for example, a ramp signal having a predetermined slope, and provides the ramp signal to the comparator 125 as a reference signal. The comparing unit 125 compares the analog sampling signal output from each of the columns from the CDS unit 122 with the ramp signal generated from the reference signal generator 124 and outputs comparison signals having transition points corresponding to valid signal components do. The counter 126 performs a counting operation to generate a counting signal, and provides the counting signal to the buffer unit 127. The buffer unit 127 includes a plurality of latch circuits, for example, static random access memories (SRAM) connected to the column lines, respectively, and outputs a counting signal output from the counter 126 in response to each comparison signal transition, And outputs the latched counting signal as image data.

The ADC unit 123 may further include an adder circuit for adding the sampling signals output from the CDS unit 122 according to the embodiment. The buffer unit 127 may further include a plurality of single line buffers.

The timing controller 129 can control the operation timings of the row driver 121, the CDS unit 122, and the ADC unit 123. [ The timing controller 129 may provide a timing signal and a control signal to the row driver 121, the CDS unit 122, and the ADC unit 123.

2 is a diagram showing a circuit of a unit pixel of an imaging apparatus according to an embodiment of the present invention.

Referring to FIG. 2, a pixel of an imaging apparatus according to an exemplary embodiment of the present invention includes a photoelectric conversion element PD, an overflow control unit (OFC), a shift switching unit (SS) A first storage node (SN1), a transfer switching unit (TS), a second storage node (SN2), a reset switching unit (RS), a drive switching unit a drive switching unit (DS), and a select switching unit (SL).

The photoelectric conversion element PD performs photoelectric conversion. That is, the photoelectric conversion element PD converts the incident light during the light integration mode to generate charges. In one embodiment, the photoelectric conversion element PD may be implemented with one or a combination of a photodiode, a phototransistor, a photogate, and a pinned photo diode (PPD). The photoelectric conversion element PD may include a first terminal and a second terminal.

The overflow control unit (OFC) may be disposed on one side of the photoelectric conversion element PD. The overflow control unit (OFC) may be disposed on the first terminal side of the photoelectric conversion element (PD). That is, the overflow controller (OFC) may be connected to the first terminal.

The overflow control unit OFC may include a terminal coupled to the photoelectric conversion element PD, another terminal to which a power supply voltage is applied, and a gate to which the overflow control signal OFCx is applied. When the overflow control signal OFCx is applied to the gate of the overflow control unit OFC, the charges accumulated in the photoelectric conversion element PD can be moved through the overflow control unit OFC.

The shift switching unit SS may be disposed on the other side of the photoelectric conversion element PD. The shift switching unit SS may be disposed on the second terminal side of the photoelectric conversion element PD. That is, the shift switching unit SS may be connected to the second terminal.

One terminal of the shift switching part SS may be connected to the photoelectric conversion element PD and the shift switching part SS may include a gate to which the shift signal SSx is applied. When the shift signal SSx is applied to the gate of the shift switching unit SS, the charges accumulated in the photoelectric conversion unit PD can move to the first charge storage unit SN1.

The first charge storage unit SN1 may be disposed at one side of the shift switching unit SS. The first charge storage unit SN1 may include a gate to which the charge storage signal SNlx is applied.

The transfer switching unit TS may be disposed at one side of the first charge storage unit SN1. One terminal of the transfer switching unit TS may be connected to the second charge storage unit SN2 and the transfer switching unit TS may include a gate to which the transfer signal TSx is applied. When the transfer signal TSx is applied to the gate of the transfer switching unit TS, the charges stored in the first charge storage unit SN1 can be transferred to the second charge storage unit SN2. At this time, the charge storage signal SN1x applied to the gate of the first charge storage unit SN1 so that the charges stored in the first charge storage unit SN1 can smoothly move to the second charge storage unit SN2, Can be removed.

The second charge storage unit SN2 may be implemented as a floating diffusion node. The second charge storage unit SN2 can accumulate the charge accumulated in the first charge storage unit SN1. The second charge storage unit SN2 is turned on when the charge storage signal SN1x is removed from the gate of the first charge storage unit SN1 and the transfer signal TSx is applied to the gate of the transfer switching unit TS, Accumulate the charges to be moved from the storage section SN1, or accumulate the charges that overflow from the first charge storage section SN1.

The reset switching unit RS may include a first terminal to which the power supply voltage VDD is applied, a second terminal connected to the second charge storage unit SN2, and a gate to which the reset signal RSx is applied.

The drive switching unit DS may include a first terminal to which a power supply voltage VDD is applied, a gate connected to the second charge storage unit SN2, and a second terminal.

The selection switching unit SL may include a first terminal connected to the second terminal of the drive switching unit DS, a gate to which the selection signal SLx is applied, and a second terminal for providing an output signal.

Hereinafter, a method of driving an imaging apparatus according to embodiments of the present invention will be described in detail with reference to the drawings.

2. Method of driving imaging device

The overflow control signal OFCx applied to the gate of the overflow control unit OFC and the shift switching unit SS applied to the gate of the overflow control unit OFC in accordance with the operation mode set in the imaging apparatus, By appropriately controlling the shift signals SSx applied to the gates of the imaging apparatuses according to the present invention so that the imaging apparatus according to an embodiment of the present invention selectively operates to implement the wide dynamic range or can implement the global shutter have.

That is, according to the driving method of the imaging apparatus according to the embodiment of the present invention, the potential barrier formed by the overflow control unit (OFC) and the potential barrier formed by the shift switching unit (SS) By appropriately controlling different modes depending on the mode, it is possible to selectively implement the wide dynamic range and the global shutter using the same pixel array.

3 is a flowchart for explaining a driving method of an imaging apparatus according to an embodiment of the present invention.

Referring to FIG. 3, a method of driving an imaging apparatus according to an exemplary embodiment of the present invention includes a step S100 of confirming a set operation mode, a step S110 of applying a control signal to a pixel array in accordance with an identified operation mode, . ≪ / RTI >

In the operation mode, the charge stored in the photoelectric converter PD provided in each pixel is shifted to a charge storage node provided in each pixel by the incident light in the pixel array 111, Or to sequentially shift the charge accumulated in the photoelectric conversion element PD provided in each pixel to the charge storage unit provided in each pixel. For example, the operation mode is to convert / read a signal according to a global shutter method or to convert / read a signal according to a rolling shutter method in the process of converting and reading incident light into an electrical signal .

Hereinafter, an operation mode for converting / reading signals in accordance with the global shutter system will be referred to as a first mode, and an operation mode for converting / reading signals according to a rolling shutter system will be referred to as a second mode. For convenience of explanation, the first mode may be referred to as a global shutter mode. Further, according to the driving method of the imaging apparatus according to the embodiment of the present invention, since the operation for securing the wide dynamic range can be performed simultaneously in converting / reading signals according to the rolling shutter system, It may be called wide dynamic range mode.

The operation mode may be automatically selected / set by the imaging apparatus 100 or may be selected / set according to an input from a user by an input unit (not shown) provided in the imaging apparatus 100. [

After confirming the operation mode as described above (S100), depending on whether the set mode is the first mode or the second mode, the control circuit 120 can apply a control signal to the pixel array 111 according to different methods (S110).

When the determined operation mode is the first mode, the control circuit 120 controls each unit pixel so that the charge accumulated in the photoelectric conversion element PD during the first period is stored in the first charge storage portion SN1, and the charge stored in the photoelectric converter PD can be moved to the overflow controller (OFC) side during the second section.

On the other hand, when the determined operation mode is the second mode, the control circuit 120 controls each unit pixel so that the charge accumulated in the photoelectric conversion element PD is stored in the first charge storage section SN1 And can be prevented from moving to the overflow control unit (OFC) side. Particularly, the supersaturated charges exceeding the capacity of the photoelectric conversion element PD can be moved to the first charge storage section SN1 without moving to the overflow control section OFC.

In the second mode, the control circuit 120 controls the overvoltage control unit 120 so that charges superposed on the photoelectric conversion element PD are transferred to the first charge storage unit SN1 without moving to the overflow control unit OFC side, The control signal can be applied such that the potential barrier formed by the flow control unit (OFC) is formed higher than the potential barrier formed by the shift switching unit (SS).

Hereinafter, a method of driving the imaging apparatus 100 in the first mode and a method of driving the imaging apparatus 100 in the second mode according to an embodiment of the present invention will be described in more detail.

2-1. Operation of the first mode (global shutter mode)

4 is a timing diagram illustrating a method of driving a pixel array of an imaging apparatus in a first mode according to an embodiment of the present invention, 6 is a timing diagram of control signals applied to the respective components of a unit pixel of the imaging device in the first mode according to an embodiment of the present invention. Fig.

4, in order to acquire an image using the imaging apparatus 100 according to an embodiment of the present invention, the pixel array 111 includes an integrating operation performed during the first section DR1, A shifting operation performed during the second section DR2 and a reading operation performed during the third section DR3 are performed.

The pixel array 111 can sequentially perform the accumulation operation, the shift operation, and the read operation, and when one set of the operations is performed, one image can be obtained.

The accumulation operation includes an operation in which incident light is converted into electric charges by the photoelectric conversion element PD. The length of the first section DR1 can be varied as needed.

The accumulation operation can be performed simultaneously for all the valid pixels included in the pixel array 111. [

The shifting operation includes an operation of moving the charge accumulated in the photoelectric conversion element PD to the first charge storage section SN1 by the incident light. In addition, the shifting operation may include a cleaning operation for removing charges (charges unnecessarily accumulated) that may have already accumulated in the first charge storage section SN1. This will be described in more detail later.

As shown in Fig. 4, the shifting operation is performed simultaneously for all the effective pixels included in the pixel array 111. Fig. However, it is desirable that the clear operation is performed simultaneously for all the valid pixels, although the clear operation need not be performed simultaneously for all the valid pixels.

While the accumulation operation and the shift operation are performed as described above, the overflow control unit (OFC) can prevent the charge accumulated in the photoelectric conversion element PD from moving to the overflow control unit (OFC) side. To this end, the overflow controller (OFC) may maintain a high potential barrier state. For example, when the overflow controller (OFC) is composed of a transistor, the transistor may be kept off.

The read operation is an operation of moving the accumulated charge moved from the photoelectric conversion element PD to the first charge storage section SN1 to the second charge storage section SN2 and the operation of moving to the second charge storage section SN2, And reading the value of the amount of charge.

The read operation may be performed simultaneously for all the effective pixels included in the pixel array 111. However, instead of performing all the effective pixels at the same time, a method of sequentially reading the pixels in a line-by-line manner may be adopted. For example, as shown in FIG. 4, a read operation is simultaneously performed on the pixels arranged in the same row, and a read operation is performed on the pixels arranged in other columns An operation can be performed.

In this case, the second charge storage unit SN2 may be a floating diffusion node. That is, the potential barrier of the second charge storage unit SN2 may not be actively changed.

On the other hand, the first cycle and the second cycle including the accumulation operation, the shift operation and the read operation, respectively, may overlap each other. That is, the first time t1 at which the first period ends may be later than the second time t2 at which the second period starts. That is, the read operation included in the first period may be performed by overlapping with the accumulation operation included in the second period.

The accumulation operation, the shift operation and the read operation in each unit pixel will be described in more detail with reference to Figs. 5 and 6. Fig.

The section (1) shown in FIGS. 5 and 6 corresponds to the above-described accumulation operation, the sections (2) to (6) correspond to the above-described shifting operation, and the sections (7) It can correspond to the above-described reading operation.

6, the overflow control unit OFC and the shift switching unit SS are controlled so that the potential barrier formed by the overflow control unit OFC and the shift switching unit SS becomes And remains high. That is, the potential barrier formed by the overflow control unit (OFC) and the shift switching unit (SS) is kept higher than the photoelectric conversion element (PD). For example, when the overflow control unit (OFC) and the shift switching unit SS are implemented as transistors, the gate of the overflow control unit (OFC) and the gate of the shift switching unit (SS) The control signals (for example, the overflow signal OFCx and the shift signal SSx) may not be applied. 5 and 6, the storage signal SN1x and the reset signal RSx are applied to the gates of the first charge storage unit SN1 and the reset switching unit RS, (TSx) is not applied to the gate of the first charge storage unit SN1, the transfer switch TS and the reset switch RS in the (1) The control signals and the potential barrier formed by them need not be controlled as shown in Figs. 5 and 6. Fig. However, for convenience of explanation, the following description will be made based on a state in which a control signal is applied as shown in Figs. 5 and 6. Fig.

(2) to (5) may correspond to the above-described clear operation. That is, the (2) to (5) periods remove charges unnecessarily accumulated in the first charge storage section SN1 so that the values of the charges accumulated in the photoelectric conversion element PD can be read more accurately .

In order to perform such a clearing operation, in the section (2), the transfer switching section TS is controlled while maintaining the state of the shift switching section SS, and the potential barrier formed by the transfer switching section TS is set to To a low state. For example, the transfer signal TSx may be applied to the gate of the transfer switching unit TS. At this time, it is preferable to control the potential barrier of the transfer switching unit TS to be equal to or less than the potential barrier of the first charge storage unit SN1. Accordingly, charges unnecessarily accumulated in the first charge storage unit SN1 can move toward the transfer switching unit TS. At this time, since the second charge storage unit SN2 may be kept in the reset state, all the charges moved to the transfer switching unit TS side can be reset, and accordingly, the first charge storage unit SN1 is unnecessary The accumulated charges can be removed. However, in order to more reliably remove the charges unnecessarily accumulated in the first charge storage section SN1, operations of the (3) and (4) periods may be further performed. That is, the potential barriers of the first charge storage unit SN1 and the transfer switching unit TS can be sequentially switched to the high state. For example, control signals (for example, a storage signal SN1x and a transmission signal TSx) applied to the gates of the first charge storage unit SN1 and the transfer switching unit TS. As a result, the charges unnecessarily accumulated in the first charge storage section SN1 can be moved to the second charge storage section SN2 side which is more reliably maintained in the reset state and can be removed. Subsequently, in the period (5), the first charge storage section SN1 and the transfer switching section TS are controlled to control the shift switch SS and the transfer switching section SS, respectively, rather than the potential barrier of the first charge storage section SN1, (TS) is maintained at a high level. Accordingly, the first charge storage unit SN1 is in a state capable of receiving the charges accumulated in the photoelectric conversion element PD.

When the clear operation is completed as described above, the operation of the (6) period is performed to move the charges accumulated in the photoelectric conversion element PD toward the first charge storage section SN1. For this purpose, it is possible to control the shift switching unit SS so that the potential barrier of the shift switching unit SS becomes lower than the potential barrier of the photoelectric conversion element PD. For example, the shift signal SSx may be applied to the gate of the shift switching unit SS.

As described above, after the charges accumulated in the photoelectric conversion element PD are moved to the first charge storage portion SN1 side, the charges moved to the first charge storage portion SN1 side in the (7) It is possible to control the shift control unit SS so as to prevent the reverse flow to the device PD side so that the potential barrier of the shift control unit SS can be converted into a high state. For example, the shift signal SSx applied to the shift control unit SS can be removed.

Subsequently, in order to eliminate the possibility that charges are accumulated by the light incident to the photoelectric conversion element PD continuously in the period (8), and the accumulated charges can overflow to the first charge storage unit SN1 , The overflow control unit (OFC) can be properly controlled. That is, by controlling the potential barrier of the overflow control unit (OFC) to be lower than the potential barrier of the shift switching unit (SS), the charges that can be accumulated in the photoelectric conversion element (PD) can be overflowed to the overflow control unit . However, since the photoelectric conversion element PD must perform the accumulation operation again to acquire the next image, and the electric charges unnecessarily accumulated in the photoelectric conversion element PD need to be removed, the overflow control unit (OFC) It is preferable to control the overflow control unit (OFC) so that the potential barrier of the overflow control unit (OFC) becomes equal to or less than the potential barrier of the photoelectric conversion element (PD).

Subsequently, in the period (9), the potential barrier of the overflow control unit (OFC) can be converted to a high state again. Charges accumulated in the photoelectric conversion element PD after the period (9) Can be used. That is, as described above with reference to FIG. 4, the read operation included in the first period and the accumulation operations included in the second period may be performed in a superimposed manner.

However, as in the section (9), the timing at which the potential barrier of the overflow control section (OFC) is converted back to a higher state to start the accumulation operation of the second period and the timing at which the accumulation operation starts between the Are not necessarily limited to those shown in Fig. 5 and Fig. As described above, according to the driving method of the imaging apparatus 100 according to the embodiment of the present invention, in the operation in the first mode, the shift operation is performed simultaneously for all the effective pixels included in the pixel array 111 But the read operation can be performed at different points in time for the pixels included in the pixel array 111. Therefore, for one unit pixel, the accumulation of the second period as shown in FIGS. 5 and 6 But the accumulation operation of the second period (for example, the accumulation operation of the accumulation operation of the overflow control unit (for example, the overflow control unit OFC) to the high state can be started to be performed, and for another unit pixel, the accumulation operation of the second period can be started at the time point between the period (11) and the period (12) Can begin to be executed.

Subsequently, in the section (10), the reset switch RS is controlled to convert the potential barrier of the reset switch RS into a high state. Subsequently, the potential of the second charge storage section SN2 may be sampled to generate a first output signal.

On the other hand, in the period (10), the selection switching unit SL can be turned on. For example, the selection signal SLx may be applied to the gate of the selection switching unit SL. The state of the selection switching unit SL that has been switched from the ON state to the ON state can last up to the (14) period.

Subsequently, charges accumulated in the first charge storage unit SN1 can be transferred to the second charge storage unit SN2 through the (11) to (13) periods. To this end, in the (11) period, the potential barrier of the transfer switching unit TS is changed to a low state so that the charges stored in the first charge storage unit SN1 can be moved to the second charge storage unit SN2 do. For example, the transmission signal TSx can be applied to the gate of the transfer switching unit TS. At this time, in order to more reliably move the charges accumulated in the first charge storage unit SN1 to the second charge storage unit SN2, operations of the (12) and (13) . That is, the potential barriers of the first charge storage unit SN1 and the transfer switching unit TS can be sequentially switched to the high state. For example, control signals (for example, a storage signal SN1x and a transmission signal TSx) applied to the gates of the first charge storage unit SN1 and the transfer switching unit TS. As a result, the charges stored in the first charge storage section SN1 can be more reliably moved toward the second charge storage section SN2. At this time, since the potential barrier of the reset switching unit RS keeps the high state continuously for the period (11) to the period (13), the charges stored in the first charge storage unit SN2 become the second charge And may be transferred to the storage section SN2 and accumulated in the second charge storage section SN2. That is, unlike the operation in the period (2) to (4), the charges transferred from the first charge storage unit SN1 to the second charge storage unit SN2 and the second charge storage unit SN2 The power supply voltage VDD can be accumulated in the second charge storage section SN2 without escaping to the first terminal side of the reset switching section RS to which the power supply voltage VDD is applied.

Then, in the period (14), the potential of the second charge storage section SN2 may be sampled to generate the second output signal.

At this time, it is possible to determine the amount of charge accumulated in the photoelectric conversion element PD by the incident light to the difference between the second output signal and the first output signal.

The potential of the second charge storage unit SN2 is sampled to generate the second output signal, and then the state of the selection switch unit SL is switched to the off state.

Each unit pixel is repeatedly performed as described above. More specifically, each unit pixel waits until the operation of the section (14) is completed in all the effective pixels included in the pixel array 111 after performing the operation of the section (14) And waits until the read operation is completed in the valid pixel). When the read operation is completed in all the valid pixels, the operation from the (1) interval to the (14) interval is repeatedly performed.

As described above, in the imaging apparatus 100 according to the embodiment of the present invention, when the operation mode is set to the first mode, the overflow control unit (OFC) (8)), the potential barrier is converted to a low state. The potential barrier of the overflow control unit (OFC) converted to the low state may preferably be kept in a low state until the accumulation operation of the next period is performed. However, since the potential barrier of the overflow control unit (OFC) is switched back to the high state in order to perform the accumulation operation, the state of the overflow control unit (OFC) is converted to the high state at least until the accumulation operation is performed .

2-2. Operation of the second mode (wide dynamic range mode)

7 is a timing chart for explaining a method of driving a pixel array of an imaging apparatus in a second mode according to an embodiment of the present invention, 9 is a timing diagram of the control signals applied to the respective components of the unit pixel of the imaging device in the second mode according to an embodiment of the present invention, Fig.

Referring to FIG. 7, in order to acquire an image using the imaging apparatus 100 according to an embodiment of the present invention, the pixel array 111 includes an integrating operation performed during the fourth period DR4, And performs a reading operation performed during the fifth interval DR5.

The pixel array 111 can sequentially perform the accumulation operation and the read operation, and when one set of the operations is performed, one image can be obtained.

However, unlike in the first mode, in the second mode, the accumulation operation and the read operation are not performed simultaneously for all effective pixels. That is, as shown in FIG. 8, for the effective pixels included in the same column, the accumulation operation and the read operation can be performed at the same time, but between the effective pixels included in the different columns, The operation can be performed at different points in time. That is, in the second mode, the accumulation operation and the read operation are performed, and instead of performing all the effective pixels at the same time, a method of sequentially reading line by line may be adopted.

The accumulation operation includes an operation in which incident light is converted into electric charges by the photoelectric conversion element PD. In addition, the accumulation operation is performed by a clearing operation (hereinafter referred to as a first clearing operation) of the photoelectric conversion element PD and / or the first charge storage section SN1 and a clearing operation of the first charge storage section SN1 2 clear operation). The details of the accumulation operation will be described later.

The read operation includes a first read operation for reading the amount of charge of at least a part of the charges overflowing from the photoelectric conversion element PD to the first charge storage part SN1 and a second read operation for reading the amount of charge accumulated in the photoelectric conversion element PD 2 < / RTI > read operation.

The value of the amount of charge read by the first read operation is used for acquiring a high contrast image and the value of the charge read by the second read operation can be used for acquiring a low contrast image. At this time, the first read operation may be performed earlier than the second read operation.

The time (first integration time) for accumulating the electric charge to be read by the first reading operation is shorter than the time for accumulating the electric charge to be read by the second reading operation (second integration time) . For example, the first accumulation time T1 and the second accumulation time T2 may have the following relationship.

1/5000? T1 / T2? 1/5

While the accumulation operation and the reading operation are performed as described above, the overflow control unit (OFC) prevents the charge accumulated in the photoelectric conversion element PD from moving to the overflow control unit (OFC) side. That is, in the first mode, the overflow controller (OFC) is controlled to selectively move the charges accumulated in the photoelectric converter PD to the overflow controller (OFC) in a specific period. In the second mode, however, The OFC controller controls the overflow controller (OFC) to prevent the charge from moving to the overflow controller (OFC). To this end, the overflow controller (OFC) maintains a high potential barrier state. For example, when the overflow controller (OFC) is composed of a transistor, the transistor may be kept off. Particularly, it is desirable that the potential barrier of the overflow control unit (OFC) be kept higher than the potential barrier of the shift switching unit (SS).

The accumulation operation and the read operation in each unit pixel will be described in more detail with reference to Figs. 8 and 9. Fig.

The sections (1) through (9) shown in FIGS. 8 and 9 correspond to the above-described storage operation, and the sections (10) through (22) correspond to the above-described reading operation. Particularly, the period (1) to (3) may correspond to the above-described first clear operation (operation to clear the photoelectric conversion element PD), and the period (6) (An operation of clearing the first charge storage section SN1). (10) to (15) may correspond to the first reading operation described above, and the (16) to (21) periods may correspond to the second reading operation described above.

9, unnecessary charges may be accumulated in the photoelectric conversion element PD and the first charge storage portion SN1 after the read operation is completed in the previous period. In order to obtain accurate information on the incident light, each unit pixel needs to clear charges unnecessarily accumulated in the photoelectric conversion element PD before performing the accumulation operation for accumulating the charge according to the incident light.

Accordingly, the first clear operation is performed through the (2) period to (4) period. (2), the potential barrier of the transfer switching unit TS can be controlled in order to remove the unnecessary accumulated charges in the first charge storage unit SN1. That is, the transfer switching unit TS can be controlled so that the potential barrier of the transfer switching unit TS becomes equal to or less than the potential barrier of the first charge storage unit SN1. For example, the transmission signal TSx can be applied to the gate of the transfer switching unit TS. Accordingly, the charges unnecessarily accumulated in the first charge storage unit SN1 are supplied to the reset switch unit (VDD) to which the power supply voltage VDD is applied through the second charge storage unit SN2 maintaining the reset state RS to the first terminal side. Subsequently, in the (3) interval, the potential barrier of the shift switching unit SS can be controlled in order to remove charges unnecessarily accumulated in the photoelectric conversion element PD. That is, the shift switching unit SS can be controlled so that the potential barrier of the shift switching unit SS becomes equal to or smaller than the potential barrier of the photoelectric conversion element PD. For example, the shift signal SSx can be applied to the gate of the shift switching unit SS. Accordingly, the electric charges unnecessarily accumulated in the photoelectric conversion element PD can move to the first electric charge storage unit SN1, and the potential barrier of the transfer switch unit TS controlled in the (2) The charges transferred to the first charge storage section SN1 are stored in the second charge storage section SN2 that maintains the reset state because the low state (for example, the state in which the transfer signal TSx is applied) To the first terminal side of the reset switching part RS to which the power supply voltage VDD is applied.

Subsequently, after the electric charges unnecessarily accumulated in the photoelectric conversion element PD and / or the first electric charge storage unit SN1 are removed through the (4) period, the potential barrier of the shift switching unit SS is reset again It can be converted into a high state. That is, the shift switching unit SS can be controlled such that the potential barrier of the shift switching unit SS is higher than the potential barrier of the photoelectric converter PD and / or the first charge storage unit SN1. For example, the shift signal SSx applied to the gate of the shift switching unit SS can be removed. Further, the potential barrier of the transfer switching unit TS can also be converted to a high state again. For example, the transmission signal TSx applied to the gate of the transfer switching unit TS can be removed. On the other hand, if the potential barrier of the first charge storage unit SN1 is in a high state, the potential barrier of the first charge storage unit SN1 can be converted to a low state. For example, the storage signal SN1x may be applied to the gate of the first charge storage unit SN1. Accordingly, it is possible to complete preparation for storing the charge generated by the incident light in the photoelectric converter PD and / or the first charge storage unit SN1. However, the potential barriers of the shift switching unit SS, the first charge storage unit SN1, and the transfer switching unit TS in the period (4) need not be simultaneously converted, and they may be sequentially converted from each other.

In this way, charges unnecessarily accumulated in the photoelectric conversion element PD and / or the first charge storage section SN1 can be removed. However, the order of the operations shown between the (2) and (4) intervals is merely an example for explaining the first clear operation, and the first clear operation is performed in the order of (2) The present invention is not limited to the operation of the section. For example, according to the above description, the potential barrier of the shift switching unit SS is first controlled and then the potential barrier of the shift switching unit SS is controlled. However, the potential of the shift switching unit SS The first clear operation can be performed according to the order of controlling the potential barrier of the transfer switching unit TS after the barrier is controlled or the potential barrier of the transfer switch SS and the transfer switch TS can be simultaneously controlled The first clear operation may be performed. Also, although the potential barrier of the first charge storage unit SN1 is always kept low during the period (2) to (4), during the first clear operation, the first charge storage unit The potential barrier of SN1 may be converted to a high state and converted to a low state.

(5), the photoelectric conversion element PD can accumulate the charges generated by the incident light. At this time, the potential barrier of the shift switching unit SS is maintained at a high state, and the potential barrier of the shift switching unit SS is lower than the potential barrier of the overflow control unit OFC. And the overflow control section OFC can be controlled. That is, the capacity of the photoelectric conversion element PD can be determined by the potential barrier of the shift switching part SS, rather than the potential barrier of the overflow control part OFC.

In general, the amount of charges accumulated in the photoelectric conversion element PD may vary depending on the amount of light incident on the photoelectric conversion element PD. For example, when the amount of incident light is large, the amount of charges accumulated increases. When the amount of incident light is small, the amount of charges accumulated is also decreased. On the other hand, when the accumulated charge amount becomes larger than the capacity of the photoelectric conversion element PD, the charges generated in the photoelectric conversion element PD exceeding the capacity of the photoelectric conversion element PD are overflowed. Hereinafter, it is assumed that charges overflowing in excess of the capacity of the photoelectric conversion element PD are transferred to the overflow.

According to the imaging apparatus 100 and the driving method thereof according to an embodiment of the present invention, the overflow control unit (OFC) and the overflow control unit (OFC) can be configured so that the potential barrier of the shift switching unit SS is lower than the potential barrier of the overflow control unit / Or the potential barrier of the shift switching unit SS, the overflow charges of the photoelectric conversion element PD overflow to the shift switching unit SS side. The overflow charge of the photoelectric conversion element PD overflows to the first charge storage section SN1 side in the section (5) shown in FIG. However, if the charge generated in the photoelectric conversion element PD in the period (5) is smaller than that of the photoelectric conversion element PD, it may not overflow to the first charge storage section SN1.

Generally, the overflow charges of the photoelectric conversion element PD can be removed without using the image formation, but according to the imaging apparatus 100 and the driving method thereof according to the embodiment of the present invention, the photoelectric conversion element PD Lt; / RTI > are used for image formation using at least some of the overflow charges.

A second clear operation for overflowing from the photoelectric conversion element PD and removing a part of the charges accumulated in the first charge storage section SN1 may be performed in the (6) and (7) periods. To this end, in the period (6), the potential barrier of the transfer switching part TS may be controlled to remove the charges accumulated in the first charge storage part SN1. That is, the potential barrier of the transfer switching unit TS can be controlled to be equal to or less than the potential barrier of the first charge storage unit SN1. Accordingly, the charges accumulated in the first charge storage unit SN1 are maintained in the reset state and the first power supply voltage VDD is applied to the first charge storage unit SN2 through the second charge storage unit SN2. It is possible to escape to the terminal side. At this time, in order to reliably remove the charges accumulated in the first charge storage unit SN1, the potential barrier of the first charge storage unit SN1 can be further converted to a high state. That is, the potential barrier of the first charge storage section SN1 can be converted into a high state as in the section (7) shown in Fig. For example, the storage signal SN1x applied to the gate of the first charge storage unit SN1 may be removed.

Subsequently, through the (8) period and the (9) period, the first charge storage section SN1 can again make a state capable of accumulating charges overflowing from the photoelectric conversion element PD. That is, the potential barrier of the transfer switching unit TS can be converted to a high state again, and further, the potential barrier of the first charge storage unit SN1 can be converted back to a low state.

However, the period (6) to (9) are operations performed to use only a part of the charges overflowing from the photoelectric conversion element PD, 9) It should not be done by the way of section. For example, FIG. 9 shows that the potential barrier of the transmission switching unit TS is converted into a high state through the period (4) to (5) and is maintained. In the period (6) (4) through (5) of the transfer switching unit (TS) through the section of (4) to (5) Even if the potential barrier is kept to be kept low, a part of the unnecessary overflow charges can escape to the first terminal side of the reset switching unit RS, so that the object of the second clear operation can be achieved.

The period (6) to (9) is an operation performed to use only a part of the charges overflowing from the photoelectric conversion element PD, If all of them are desired to be used, the operations of the (6) to (9) sections may be omitted.

Subsequently, charges to be read in the first read operation are accumulated in the first charge storage section SN1 through the section (10). That is, the charges overflowed from the photoelectric conversion element PD to the first charge storage section SN1 are accumulated in the first charge storage section SN1 through the section (10).

The time during which the operation of the section 10 is performed can be determined by the first accumulation time T1 (the time for accumulating the charge to be read by the first read operation). However, the time period during which the operation of the (10) interval may not coincide with the first accumulation time, and in the first accumulation time, a time period during which the period (11) and / May be included.

A first read operation can be performed through a period (11) to (15). That is, the charges overflow from the photoelectric conversion element PD to the first charge storage section SN1 are moved to the second charge storage section SN2 by a series of operations, and then, The first read operation can be performed by reading the amount of charge transferred to the portion SN2. The first read operation performed through the period (11) to (15) is the same as or similar to the operation described in the period (10) to (14) described with reference to FIG.

That is, in the period (11), the potential barrier of the reset switching unit RS can be converted into a high state by controlling the reset switching unit RS, thereby changing the potential of the second charge storage unit SN2 to And generate a third output signal by sampling. Further, charges accumulated in the first charge storage unit SN1 can be transferred to the second charge storage unit SN2 through the period (12) to (14), and in the period (15) The fourth output signal can be generated by sampling the potential of the charge storage section SN2. At this time, the amount of charge accumulated overflow from the photoelectric conversion element PD to the first charge storage section SN1 (hereinafter referred to as the overflow charge amount) by the incident light to the difference between the second output signal and the first output signal is determined . A method of controlling the transfer switching unit TS, the first charge storage unit SN1 and the reset switching unit RS to obtain the overflow charge amount through the period (11) to (15) (10) to (14) described above with reference to FIG. 6B, detailed description thereof will be omitted here.

The amount of overflow charge obtained by the first read operation is used to obtain a high contrast image according to the imaging apparatus 100 and the driving method thereof according to an embodiment of the present invention so that the wide dynamic range WDR Can be implemented.

The first accumulation time, which is the time for accumulating the overflow charge amount to be read in the first reading operation, may be a constant value, but it may be a value that can be changed in real time or periodically by analyzing at least one image obtained have. For example, if it is determined that the illuminance is very high as a result of analysis of at least one image that has already been acquired (i.e., if the illuminance is equal to or greater than a preset first illumination threshold value), the first accumulation time Can be made shorter. Conversely, if the analysis determines that the illuminance is not significantly high (i.e., if the illuminance is below a preset second illumination threshold value), the first accumulation time may be longer than that used to acquire the previous image.

Meanwhile, the first accumulation time may be applied to all the effective pixels included in the pixel array 111, but may be set differently for the effective pixels. For example, by analyzing at least one image that has already been obtained, the illumination distribution for each effective pixel can be confirmed, and based on the illumination distribution for each effective pixel, The first accumulation time to be set can be set differently.

The first accumulation time is closely related to the expansion of the dynamic range to be implemented in the second operation mode according to an embodiment of the present invention, so that it can be controlled by various methods not limited to the above will be.

Then, a second read operation can be performed through the (16) to (22) sections. That is, the charges generated in the photoelectric converter PD by the incident light and accumulated are moved to the second charge storage unit SN2 via the first charge storage unit SN1, and then the second charge storage unit SN2 The second read operation can be performed. The second read operation performed through the period (16) to (22) is the same as the operation described in the section (6), the section (7) and the section (9) to section similar.

That is, the charge accumulated in the photoelectric conversion element PD can be transferred to the first charge storage section SN1 through the (16) period and the (17) period. At this time, the charges stored in the second charge storage unit SN2 for the first read operation can be removed. That is, the charge stored in the second charge storage unit SN2 is controlled by the reset switching unit (VDD) to which the power supply voltage VDD is applied by controlling the potential barrier of the reset switching unit RS RS to the first terminal side. Subsequently, in the section (17), the potential barrier of the reset switching part RS can be converted into a high state by controlling the reset switching part RS, thereby changing the potential of the second charge storage part SN2 to And generate a fifth output signal by sampling. Further, charges accumulated in the first charge storage unit SN1 can be transferred to the second charge storage unit SN2 through the interval (18) to (20), and in the interval (21) The sixth output signal can be generated by sampling the potential of the charge storage section SN2. At this time, it is possible to determine the amount of charge (hereinafter referred to as " photoelectric conversion element charge amount ") generated and accumulated in the photoelectric conversion element PD by the incident light to the difference between the fifth output signal and the sixth output signal. Subsequently, in the section (22), charges accumulated in the second charge storage section SN2 can be reset.

(TS), a first charge storage (TS), a second charge storage (TS), and a second charge storage (TS) in order to obtain the amount of charge generated and accumulated in the photoelectric converter PD by the incident light, The method of controlling the unit SN1 and the reset switching unit RS is the same as or similar to the method described in the section (6), the section (7), and the section (9) to section (13) , And a detailed description thereof will be omitted here.

The amount of photoelectric conversion element charge obtained by the second reading operation is used to acquire a low-illuminance image according to the imaging apparatus 100 and the driving method thereof according to an embodiment of the present invention, and thus the wide dynamic range WDR Can be implemented.

The second accumulation time, which is the time for accumulating the charge quantity of the photoelectric conversion element to be read in the second read operation, may be a constant value, but it may be a value that can be changed in real time or periodically by analyzing at least one image It is possible. For example, if it is determined that the illuminance is very low as a result of analysis of at least one image that has already been obtained (i.e., if it is lower than a predetermined third illumination threshold value), the first accumulation time Can be longer than that. Conversely, if it is determined that the illuminance is not significantly low (i.e., the preset fourth illumination intensity threshold value or more) as a result of the analysis, the second accumulation time may be shorter than that used for acquiring the previous image.

Meanwhile, the second accumulation time may be the same for all the effective pixels included in the pixel array 111, but may be set differently for the effective pixels. For example, by analyzing at least one image that has already been obtained, the illumination distribution for each effective pixel can be confirmed, and based on the illumination distribution for each effective pixel, It is possible to set the second accumulation time to be different from each other.

The second accumulation time is closely related to the expansion of the dynamic range to be implemented in the second operation mode according to an embodiment of the present invention, so that it can be controlled by various methods not limited to the above will be.

Each unit pixel is repeatedly performed as described above. More specifically, after each of the unit pixels performs the operation of the (1) to (22) interval, the operation of the (1) to (22) interval may be performed again.

As described above, the imaging apparatus 100 according to an embodiment of the present invention can maintain the overflow control unit (OFC) at a high level throughout the whole area when the operation mode is set to the second mode. In particular, the potential barrier of the overflow control part (OFC) can be maintained higher than the potential barrier of the shift switching part (SS). This is because, in the operation of the second mode according to the embodiment of the present invention, the charge overflowing from the photoelectric conversion element PD is used for image acquisition because of the charge overflowing from the photoelectric conversion element PD, All of the charges must be transferred to the first charge storage unit SN1 side without overflowing to the OFC side.

For the sake of convenience of explanation, it is explained that the potential barrier of the overflow control unit (OFC) should always be kept at a high state (that is, higher than the potential barrier of the shift switching unit SS) The potential barrier of the overflow control unit (OFC) may be converted to a state equal to or lower than the potential barrier of the shift switching unit (SS) and then converted to a higher state within a range to achieve the object of the invention. For example, according to the embodiment of the present invention, all of the charges overflowing from the photoelectric conversion element PD may not be used for image acquisition (see section (5) to section (9) of FIG. 9) In such a period, the potential barrier of the overflow control unit (OFC) may be controlled to be equal to or lower than the potential barrier of the shift switching unit (SS).

For the sake of convenience of explanation, the potential barrier of the overflow control unit (OFC) has been described as always maintaining the same value throughout the entire range. However, in order to achieve the object of the present invention, the potential of the overflow control unit The barrier can be changed. For example, the potential barrier of the overflow control unit (OFC) may be changed if it is maintained higher than the potential barrier of the shift switching unit SS in some required period.

It is possible to obtain a final image in which the dynamic range is expanded based on the amount of overflow charge and the amount of photoelectric converter charge obtained as described above. That is, a final image with an expanded dynamic range can be obtained based on the high-contrast image that can be obtained based on the obtained amount of overflow charge and the low-luminance image that can be obtained based on the amount of photoelectric conversion element charge.

3. Automatic selection of operation mode

FIG. 10 is a flowchart for explaining a method of selecting an operation mode according to an embodiment of the present invention, FIG. 11 is an example of an image histogram for explaining a method of selecting an operation mode according to an embodiment of the present invention Fig.

The selection of the operation mode according to an embodiment of the present invention may be performed by a value input from the user through a user interface (UI) or the like, but as described below, May be automatically selected by the judgment of the imaging apparatus 100 according to the present invention.

In the following, the imaging apparatus 100 may have a mode selector (not shown) for selection of the operation mode to be described. That is, the method of automatically selecting the operation mode described below may be performed by the mode selector included in the imaging apparatus 100. [

Hereinafter, a method of automatically selecting an operation mode by the imaging apparatus 100 will be described.

First, the imaging apparatus 100 may acquire an image for operation mode selection (S200).

The image obtained in step S200 may be obtained according to the above-described imaging apparatus 100 according to an embodiment of the present invention and the driving method thereof. For example, when step S200 is performed, it may be an image obtained according to an operation mode already set in the imaging apparatus 100. [ If the already set operation mode is the second mode, the image displayed in step S200 is a high-contrast image acquired based on the amount of overflow charge, a low-luminance image acquired based on the photoelectric conversion element charge amount, And a final image acquired based on the low-illuminance image.

However, the image obtained in step 200 is not limited to that obtained in accordance with the above-described imaging apparatus 100 and its driving method according to an embodiment of the present invention described above.

The timing at which the image is acquired in step S200 is performed within a predetermined time range when the operation mode is selected / set by the step S210 described below. For example, the step S200 may be performed before a predetermined time (for example, one second before, two seconds before, one half second, etc.) before the step S210 is performed.

When a moving image is to be photographed through the imaging apparatus 100, preferably, the predetermined time may be a time interval between a frame and a frame set in the imaging apparatus 100. That is, assuming a first image (first frame) and a second image (second frame, immediately next frame of the first frame) included in the moving image, the first image is used for automatically selecting / setting the operation mode The second image can be taken in accordance with the operation mode used as the image and set based on the first image. However, this is only a preferred embodiment, and an image used for the automatic operation mode setting may be a frame before some frames other than the immediately preceding image (frame).

In the case where a still image is to be photographed through the imaging apparatus 100, preferably, immediately after the generation of a signal for capturing the still image (e.g., a signal generated by a user's shutter depression) Lt; / RTI > For example, when a still image is to be photographed by a user's shutter pressing, an image by step S200 can be obtained at a point in time before the actual shutter is fully pressed, such as a half-shutter, When the shutter is fully depressed after the operation mode is selected / set, the still image can be acquired according to the operation mode set at that time.

Subsequently, the imaging apparatus 100 selects / sets the operation mode based on the acquired image (S210).

In order to set / select the operation mode in step S210, a method by one of the methods described below or a combination thereof may be used.

First, the imaging apparatus 100 confirms the histogram of the acquired image, and sets the operation mode to the second mode (wide dynamic range mode) when the attribute of the acquired image conforms to the preset reference based on the confirmed histogram .

For example, the imaging device 100 may analyze the image obtained in step S200 to obtain a histogram, and thus the intra-scene dynamic range of the acquired image may be determined. That is, when the histogram of the obtained image is as shown in Fig. 11, the intradewy dynamic range of the acquired image for each histogram (a), (b) and (c) can be determined. 11 (a) and 11 (b), it can be seen that the histogram is formed over a wide illuminance range, whereby the intra-scene dynamic range of the acquired image can be determined to be wide , It can be seen that the histogram is formed over a relatively narrow illuminance range as shown in FIG. 11 (c), whereby it can be judged that the intradewy dynamic range of the obtained image is narrow. In this case, the imaging apparatus 100 sets a threshold value for the intra-scene dynamic range in advance, and when the value of the intra-scene dynamic range obtained in step S200 is equal to or greater than a predetermined threshold value, .

In the above-described example, the imaging apparatus 100 selects / sets the operation mode considering only the intra-scene dynamic range among the attributes of the acquired image. However, even if other attributes other than the intra- It will be acceptable.

Second, the imaging apparatus 100 may acquire at least two images at step S200, confirm a difference between the obtained two or more images, and select / set an operation mode according to the identified difference. More preferably, the obtained two or more images are sequentially acquired images.

In general, a global shutter is a method used to acquire an image without image distortion when acquiring an image of a fast-moving subject.

On the other hand, when the difference between the two or more images (consecutive frames) sequentially obtained at the time of shooting the moving picture is large, it can be determined that the movement of the subject is fast.

Thus, the imaging device 100 may preset a threshold for the difference between images, and if the difference between at least two images identified is greater than or equal to the threshold, the imaging device 100 may set the mode of operation to a first mode (Global shutter mode). At this time, the imaging apparatus 100 may acquire two images to check the difference, but it may be used to acquire three or more images to identify differences between three or more images to select / set an operation mode will be.

Even when the user wants to capture a still image other than a moving image by using the imaging apparatus 100 according to the present invention, at least two images may be acquired immediately before the still image is captured through step S200.

As described above, after the imaging apparatus 100 automatically sets the operation mode, the imaging apparatus 100 can operate according to the set operation mode.

The imaging apparatus 100 may continue to perform such operations for setting the operation mode periodically or in real time. Alternatively, the imaging device 100 may perform operations for setting the operation mode as described above only when there is a special request from the user.

As described above, the use of the acquired image for the automatic mode selection according to the embodiment of the present invention has been described. In this case, it is assumed that the sensor used for image acquisition and the sensor used for automatic mode selection are the same, but the two sensors may not be identical to each other. That is, a sensor for acquiring an image for automatic mode selection may be separately provided.

4. Another embodiment of the wide dynamic range mode driving method

The driving method of the imaging apparatus described with reference to Figs. 7 to 9 is an example of a driving method for realizing the wide dynamic range. A driving method of an imaging apparatus according to another embodiment of the present invention to be described below also relates to a driving method for implementing a wide dynamic range. That is, the method of driving an imaging apparatus according to another embodiment to be described below may replace the method of driving an imaging apparatus according to an embodiment of the present invention for the operation of the second mode described above. However, It can be used as a driving method for realizing a wide dynamic range.

The method of driving the imaging apparatus 100 according to another embodiment to be described below may be implemented in the pixel array 111 described with reference to FIG. 2. However, in the imaging apparatus 100 according to another embodiment of the present invention, The overflow control unit OFC may not be included.

FIG. 12 is a timing chart for explaining a method of driving a pixel array of an imaging apparatus according to another embodiment of the present invention. FIG. 13 is a timing chart Fig. 14 is a diagram showing a potential barrier for explaining charge transfer in a unit pixel of an imaging apparatus according to another embodiment of the present invention. Fig.

12, in order to acquire an image using the imaging apparatus 100 according to an embodiment of the present invention, the pixel array 111 includes an integrating operation performed during the sixth section DR6, And performs a reading operation performed during the seventh section DR7.

The pixel array 111 can sequentially perform the accumulation operation and the read operation, and when one set of the operations is performed, one image can be obtained.

The accumulation and read operations may not be performed simultaneously for all valid pixels. That is, as shown in FIG. 12, for the effective pixels included in the same column, the accumulation operation and the read operation can be performed at the same time, but between the effective pixels included in the different columns, The operation can be performed at different points in time. That is, instead of performing all the effective pixels at the same time, a method of sequentially reading line by line may be adopted.

The accumulation operation includes an operation in which incident light is converted into electric charges by the photoelectric conversion element PD. In addition, the accumulation operation is performed by a clearing operation (hereinafter referred to as a third clearing operation) of the photoelectric conversion element PD and / or the first charge storage section SN1, a clearing operation of the first charge storage section SN1 4 clear operation) and a second charge storage section SN2 clear operation (hereinafter referred to as a fifth clear operation). The details of the accumulation operation will be described later.

The read operation is a third read operation for reading the amount of charge of at least a part of the charges overflowing from the first charge storage unit SN1 to the second charge storage unit SN2, And a fifth reading operation for reading the amount of charge accumulated in the photoelectric conversion element PD.

The value of the charge amount read by the third read operation is used for acquiring the high contrast image, the value of the charge read by the fourth read operation can be used for acquiring the contrast image, The value of the charge read out can be used to obtain a low-illuminance image. At this time, the third read operation may be performed earlier than the fourth read operation, and the fourth read operation may be performed earlier than the fifth read operation.

The time (third accumulation time, third integration time) for accumulating the electric charge to be read by the third reading operation is shorter than the time for accumulating the electric charge to be read by the fourth reading operation (fourth accumulation time) And the fourth accumulation time may be shorter than the fifth accumulation time (fifth accumulation time) by the fifth reading operation. For example, the third accumulation time T3, the fourth accumulation time T4, and the fifth accumulation time T5 may have the following relationship.

1/5000? T3 / T4? 1/5

1/5000? T4 / T5? 1/5

If the driving method of the imaging apparatus 100 according to another embodiment of the present invention is applied instead of the driving method according to the second mode described above, while the accumulation operation and the reading operation described above are performed, (OFC) prevents the electric charge accumulated in the photoelectric conversion element PD from moving to the side of the overflow control unit (OFC). That is, the overflow control unit (OFC) is controlled to prevent the charge from moving to the overflow control unit (OFC) side in all the intervals. To this end, the overflow controller (OFC) maintains a high potential barrier state. For example, when the overflow controller (OFC) is composed of a transistor, the transistor may be kept off. Particularly, it is desirable that the potential barrier of the overflow control unit (OFC) be kept higher than the potential barrier of the shift switching unit (SS).

The accumulation operation and the read operation in each unit pixel will be described in more detail with reference to Figs. 13 and 14. Fig.

(1) to (4) is a section corresponding to the third clear operation. In order to obtain accurate information on the incident light, each unit pixel is subjected to photoelectric conversion This is a period for clearing charges unnecessarily accumulated in the element PD. The operations therefor are the same as or similar to those described in the section (1) to (4) described with reference to FIG. 9, and therefore a detailed description thereof will be omitted.

(5), the photoelectric conversion element PD can accumulate the charges generated by the incident light. At this time, the potential barrier of the shift switching unit SS can maintain a high state. That is, the potential barrier of the shift switching unit SS can be controlled to be higher than the potential barrier of the photoelectric conversion element PD. However, when the driving method according to another embodiment of the present invention is applied to the second mode described above, the potential barrier of the shift switching unit SS is shifted to a lower state than the potential barrier of the overflow control unit (OFC) The SS and the overflow control unit OFC can be controlled. That is, the capacity of the photoelectric conversion element PD can be determined by the potential barrier of the shift switching part SS, rather than the potential barrier of the overflow control part OFC.

Although the overflow charge of the photoelectric conversion element PD overflows to the first charge storage section SN1 side in the section (5) shown in FIG. 14, in the section (5) If the generated charge is smaller than the capacity of the photoelectric conversion element PD, it may not overflow to the first charge storage section SN1.

Generally, the overflow charges of the photoelectric conversion element PD can be removed without using image formation, but according to the imaging apparatus 100 and the driving method thereof according to another embodiment of the present invention, the photoelectric conversion element PD Lt; / RTI > are used for image formation using at least some of the overflow charges.

The fourth clear operation and the fifth clear operation for removing a part of the charges accumulated in the first charge storage portion SN1 overflow from the photoelectric conversion element PD are performed in the (6) and (7) . Subsequently, through the (8) period and the (9) period, the first charge storage section SN1 can again make a state capable of accumulating charges overflowing from the photoelectric conversion element PD. The explanation of the section (6) to (9) is replaced with the description of the section (6) to (9) of FIG.

Subsequently, charges overflowing from the photoelectric conversion element PD to the first charge storage section SN1 are accumulated in the first charge storage section SN1 through the section (10). If the amount of charge overflowed from the photoelectric conversion element PD to the first charge storage section SN1 is larger than that of the first charge storage section SN1, the charge accumulated in the first charge storage section SN1 Can also be overflowed. At this time, the potential barrier of the transfer switching part TS is set so that the potential barrier of the shift switching part SS can be set to the potential barrier of the transfer switch part SS so that the charges overflowing from the first charge storage part SN1 can overflow to the second charge storage part SN2 side. Lt; RTI ID = 0.0 > and / or < / RTI >

The potential barrier of the reset switching unit RS can be converted into a high state in order to store the charges overflowing from the first charge storage unit SN1 in the second charge storage unit SN2 . That is, the potential barrier of the reset switching unit RS can be controlled to be larger than the potential barrier of the second charge storage unit SN2. For example, the reset signal RSx applied to the reset switching unit RS can be removed.

The time during which the operation of the section 11 is performed can be determined by the third accumulation time T3, the time for accumulating the charge to be read by the third reading operation.

In addition, a third read operation may be performed in the (11) interval. That is, the amount of charge that overflows from the photoelectric conversion element PD to the first charge storage section SN1 and overflows from the first charge storage section SN1 to the second charge storage section SN2 is referred to as a third read operation Can be read by.

The amount of overflow charge obtained by the third reading operation is used to obtain a high-contrast image according to the imaging apparatus 100 and the driving method thereof according to another embodiment of the present invention, so that the wide dynamic range WDR Can be implemented.

The third accumulation time, which is the time for accumulating the overflow charge amount to be read in the third reading operation, may be a constant value, but it may be a value that can be changed in real time or periodically by analyzing at least one image already obtained have. For example, if it is determined that the illuminance is very high as a result of the analysis of at least one image that has already been obtained (i.e., the illuminance is equal to or greater than a preset fifth illuminance threshold), the third accumulation time Can be made shorter. Conversely, if the analysis determines that the illumination is not significantly high (i.e., if the preset sixth illumination threshold value is less than or equal to the predetermined sixth illumination threshold value), the third accumulation time may be longer than that used for acquiring the previous image.

Meanwhile, the third accumulation time may be the same for all the effective pixels included in the pixel array 111, but may be set differently for the effective pixels. For example, by analyzing at least one image that has already been obtained, the illumination distribution for each effective pixel can be confirmed, and based on the illumination distribution for each effective pixel, The third accumulation time to be set can be set differently.

The third accumulation time is closely related to the expansion of the dynamic range to be implemented according to another embodiment of the present invention, so that it can be controlled by various methods not limited to the above.

Subsequently, the charges stored in the second charge storage unit SN2 can be reset through the period (12). That is, by converting the potential barrier of the reset switching part RS into a low state, the charges accumulated in the second charge storage part SN2 are supplied to the first switch SW of the reset switching part RS to which the power supply voltage VDD is applied It can be made to be able to escape to the terminal side.

Then, a fourth read operation can be performed through the (13) to (17) intervals. That is, the amount of charge accumulated in the first charge storage section SN1 can be read by overflowing from the photoelectric conversion element PD to the first charge storage section SN1. To this end, the charges stored in the first charge storage unit SN1 can be transferred to the second charge storage unit SN2 through the (14) to (16) The amount of charge accumulated in the charge storage section SN2 can be read. A detailed description thereof will be replaced with a description of the section (10) to (15) described with reference to FIG.

The amount of photoelectric conversion element charge obtained by the fourth read operation is used to acquire a contrast enhancement image according to the imaging apparatus 100 and the driving method thereof according to another embodiment of the present invention, WDR) can be implemented.

The fourth accumulation time, which is the time for accumulating the overflow charge amount to be read in the fourth read operation, may be a constant value, but it may be a value that can be changed in real time or periodically by analyzing at least one image obtained have. For example, if it is determined that the illuminance is very high as a result of analysis of at least one image that has already been obtained (i.e., the preset seventh illumination threshold value or more), the fourth accumulation time is the one used for acquiring the previous image Can be made shorter. Conversely, if it is determined that the illuminance is not significantly high (i.e., the preset eighth illumination threshold value or less) as a result of the analysis, the fourth accumulation time may be longer than that used for acquiring the previous image.

Meanwhile, the fourth accumulation time may be the same for all the effective pixels included in the pixel array 111, but may be set differently for the effective pixels. For example, by analyzing at least one image that has already been obtained, the illumination distribution for each effective pixel can be confirmed, and based on the illumination distribution for each effective pixel, The fourth accumulation time to be set can be set differently.

The fourth accumulation time is closely related to the expansion of the dynamic range to be implemented according to another embodiment of the present invention, so that it can be controlled by various methods not limited to the above.

Then, a fifth read operation can be performed through the (18) to (23) sections. That is, the charges generated in the photoelectric converter PD by the incident light and accumulated are moved to the second charge storage unit SN2 via the first charge storage unit SN1, and then the second charge storage unit SN2 The fifth read operation can be performed. The fifth read operation performed through the (18) to (23) sections is the same as or similar to the operation described in the section (16) to (22) described with reference to FIG.

The overflow charge amount obtained by the fifth read operation is used to acquire a low-illuminance image according to the imaging apparatus 100 and the driving method thereof according to another embodiment of the present invention, . ≪ / RTI >

The fifth accumulation time, which is the time for accumulating the overflow charge amount to be read in the fifth read operation, may be a constant value, but it may be a value that can be changed in real time or periodically by analyzing at least one image obtained have. For example, if it is determined that the illuminance is very high as a result of analysis of at least one image that has already been obtained (i.e., the preset ninth illumination is above the threshold value), the fifth accumulation time may be the one used for acquiring the previous image Can be made shorter. Conversely, if the analysis determines that the illuminance is not significantly high (i.e., the preset tenth dimension is below the threshold value), the fifth accumulation time may be longer than that used for acquiring the previous image.

Meanwhile, the fifth accumulation time may be applied to all the effective pixels included in the pixel array 111, but it may be set differently for the effective pixels. For example, by analyzing at least one image that has already been obtained, the illumination distribution for each effective pixel can be confirmed, and based on the illumination distribution for each effective pixel, The fifth accumulation time to be set can be set differently.

The fifth accumulation time is closely related to the expansion of the dynamic range to be implemented in accordance with another embodiment of the present invention, and thus it can be controlled by various methods not limited to the above.

Each unit pixel is repeatedly performed as described above. More specifically, after each of the unit pixels performs the operation of the (1) to (23) interval, the operation of the (1) to (23) interval may be performed again.

As described above, according to the driving method of the imaging apparatus 100 according to another embodiment of the present invention, at least a part of the charges overflowing in the first charge storage unit SN1 can be used for image acquisition, It is possible to allow the imaging apparatus 100 to have a wider dynamic range than the driving method described with reference to FIGS.

Claims (11)

A shift switching unit disposed at one side of the photoelectric conversion element, a first charge storage unit disposed at one side of the shift switching unit, a transfer switching unit disposed at one side of the first charge storage unit, A pixel including a second charge storage portion disposed therein and a reset switching portion disposed on one side of the second charge storage portion; And
And a control circuit for applying a signal to the pixel,
The control circuit includes a first reading operation for reading the amount of charge stored in the photoelectric conversion element, a second reading operation for overflowing from the photoelectric conversion element to the first charge storage section and reading the amount of charge stored in the first charge storage section And a third reading operation for reading the amount of charge overflow from the first charge storage unit to the second charge storage unit
Imaging device.
The method according to claim 1,
Wherein the first reading operation includes an operation of moving the charge stored in the photoelectric conversion element to the second charge storage portion through the first charge storage portion and reading out
Imaging device.
The method according to claim 1,
And the second read operation includes an operation of moving charges stored in the first charge storage unit overflow from the photoelectric conversion element to the first charge storage unit to the second charge storage unit and reading out
Imaging device.
The method according to claim 1,
Wherein the second charge storage portion is a floating diffusion node
Imaging device.
2. The control circuit according to claim 1,
After the photoelectric conversion element is reset, before the third read operation is performed, the transfer switching unit is not turned on
Imaging device.
2. The control circuit according to claim 1,
After resetting the photoelectric conversion element, before performing the second read operation, the shift switching unit
Imaging device.
2. The control circuit according to claim 1,
Performing the second read operation after performing the third read operation,
And performs the first read operation after performing the second read operation
Imaging device.
The method according to claim 1,
Wherein the first accumulation time for accumulating the amount of charge read by the first reading operation is longer than the second accumulation time for accumulating the amount of charge read by the second reading operation.
9. The method of claim 8,
The second accumulation time is selected in a range of 1/5000 or more of the first accumulation time and 1/5 or less of the first accumulation time
Imaging device.
The method according to claim 1,
Wherein the second accumulation time for accumulating the amount of charge read by the second reading operation is longer than the third accumulation time for accumulating the amount of charge read by the third reading operation.
11. The method of claim 10,
The third accumulation time is selected in a range of 1/5000 or more of the second accumulation time and 1/5 or less of the first accumulation time
Imaging device.

Images