Solid-state imaging device and imaging apparatus provided with the same

Abstract

A solid-state imaging device and an imaging apparatus including the same are provided. The solid-state imaging device includes: a pixel having a photoelectric conversion element, a floating node portion, and a reset portion; a first circuit connected to the pixel; and a second circuit connected to the first circuit, the floating node portion being capable of handling an amount of charge smaller than that of the photoelectric conversion element, the first circuit controlling the pixel to perform a plurality of combination operations including a reset of the floating node portion, a transfer of signal charge to the floating node portion, and a readout of a voltage signal from the pixel corresponding to the amount of charge of the signal charge of the floating node portion, and the second circuit coupling signals corresponding to the voltage signals read from the pixel in each of the combination operations.

Description

Technical Field

[0001] This invention relates to solid-state imaging elements and imaging apparatus having solid-state imaging elements. Background Technology

[0002] Previously, solid-state imaging elements such as CCD (Charge Coupled Device) and CMOS (Complementary Metal Oxide Semiconductor) image sensors were used in shooting devices with shooting functions, such as digital cameras, digital camcorders, and smartphones.

[0003] In this solid-state imaging element, the signal charge after photoelectric conversion of the input light is transferred to the floating node on photoelectric conversion elements such as photodiodes. Based on the amount of charge, the voltage signal (pixel signal) is output from the pixel through the source follower.

[0004] In recent years, due to the demand for shooting various scenes, it is necessary to increase the amount of signal charge that a pixel can handle in a single input (i.e., light incidence) by increasing the amount of saturated signal charge in the pixels of solid-state imaging elements and the amount of charge that floating nodes can handle by transferring the signal charge accumulated in the photoelectric conversion elements.

[0005] However, if the amount of signal charge that a pixel can process in an input is increased, the noise in the voltage signal output from the pixel (such as input conversion noise) will also increase, thus degrading the image quality of the captured image.

[0006] Existing technical documents

[0007] Patent documents

[0008] Patent Document 1: U.S. Patent No. 7075049. Summary of the Invention

[0009] The problem the invention aims to solve

[0010] Therefore, the objective of this invention is to provide a solid-state imaging element capable of suppressing the increase of noise in the signal read from the pixel and capable of increasing the amount of signal charge that the pixel can process, and an imaging apparatus having the solid-state imaging element.

[0011] Solution for solving the problem

[0012] The solid-state imaging element of the present invention includes:

[0013] A pixel having at least one photoelectric conversion element that performs photoelectric conversion on input light to generate signal charge, a floating node portion that transfers the signal charge from the at least one photoelectric conversion element, and a reset portion that resets the signal charge of the floating node portion.

[0014] A first circuit, which is connected to the aforementioned pixel; and

[0015] The second circuit is connected to the first circuit described above.

[0016] The amount of charge that can be processed by a single input in the aforementioned floating node section, i.e., the first charge, is less than the amount of charge that can be processed by a single input in the aforementioned at least one photoelectric conversion element, i.e., the second charge.

[0017] The first circuit controls the pixel to perform multiple first combination operations for a single input to the at least one photoelectric conversion element, the first combination operations including:

[0018] The reset of the signal charge of the aforementioned floating node,

[0019] The transfer of signal charge from at least one photoelectric conversion element to the floating node, and

[0020] A voltage signal is read from the pixel, and the voltage signal corresponds to the amount of charge of the signal charge transferred to the floating node.

[0021] The second circuit described above couples a signal corresponding to the voltage signal read from the pixel in each of the first combined operations for a single input to the at least one photoelectric conversion element.

[0022] Among the aforementioned solid-state imaging elements,

[0023] The first circuit controls the pixel to read the voltage signal (i.e., the reset signal) when the floating node is in the reset state during each of the first combination operations, and to read the voltage signal (i.e., the transferred charge signal) when the floating node is in the state where the signal charge is transferred from the at least one photoelectric conversion element after the reset signal is read.

[0024] During each of the first combination operations, the second circuit generates a difference signal between the transferred charge signal and the reset signal as a signal corresponding to the voltage signal.

[0025] In addition, among the aforementioned solid-state imaging elements,

[0026] The aforementioned pixels have multiple of the aforementioned photoelectric conversion elements.

[0027] The first charge quantity mentioned above can be a quantity corresponding to the number of the aforementioned photoelectric conversion elements.

[0028] In addition, among the aforementioned solid-state imaging elements,

[0029] The aforementioned pixel may have a gain switching unit, which switches the conversion gain of the voltage signal of the signal charge transferred to the aforementioned floating node between a first conversion gain and a second conversion gain lower than the first conversion gain by changing the aforementioned first charge amount.

[0030] In addition, among the aforementioned solid-state imaging elements,

[0031] The first circuit controls the pixel to perform the reset, transfer, and read operations in each of the first combination operations under the second conversion gain state, and performs the second combination operation under the first conversion gain state between the reset and read operations in the first group of first combination operations. The second combination operation includes: the reset, the transfer, and the read operation.

[0032] The second circuit described above outputs a signal corresponding to the voltage signal read in the second combined operation by inputting the amount of the signal charge generated in the at least one photoelectric conversion element at a time. Alternatively, it may couple and output a signal corresponding to the voltage signal read in each of the first combined operations.

[0033] In addition, the imaging device of the present invention includes:

[0034] Optical systems; and

[0035] Any of the above solid-state imaging elements;

[0036] The aforementioned solid-state imaging element has a pixel array in which the pixels are arranged in a matrix.

[0037] The aforementioned optical system images the subject on the aforementioned pixel array.

[0038] In addition, the imaging device of the present invention includes:

[0039] A solid-state imaging element having a plurality of pixels arranged in a matrix, each pixel having at least one photoelectric conversion element for photoelectric conversion of input light to generate signal charge and a floating node portion for transferring the signal charge from the at least one photoelectric conversion element;

[0040] The first circuit is connected to each pixel of the aforementioned solid-state imaging element;

[0041] The second circuit is connected to the first circuit described above;

[0042] An optical system that images the object being photographed on the aforementioned solid-state imaging element; and

[0043] The output section outputs the captured images to the outside.

[0044] The amount of charge that can be processed in a single input at the floating node portion of each pixel is less than the amount of charge that can be processed in a single input at at least one photoelectric conversion element of that pixel.

[0045] The first circuit controls the pixel to perform multiple first combination operations on a single input to the at least one photoelectric conversion element via the optical system, the first combination operations including:

[0046] The transfer of signal charge from at least one photoelectric conversion element to the floating node and the reading of voltage signal from the pixel, wherein the voltage signal corresponds to the amount of signal charge transferred to the floating node.

[0047] The second circuit described above, for a single input to the at least one photoelectric conversion element, couples the signal corresponding to the voltage signal read from each of the pixels in each of the first combined operations, pixel by pixel.

[0048] The output unit outputs the captured image generated based on the coupled signal to the outside.

[0049] In addition, the aforementioned filming device,

[0050] It has a mode switching unit that allows for switching shooting modes.

[0051] The aforementioned mode switching unit can also switch to a first mode that performs multiple of the aforementioned first combination operations and a second mode that performs one set of the aforementioned first combination operations. Attached Figure Description

[0052] Figure 1 This is a functional block diagram of the imaging device according to the first embodiment.

[0053] Figure 2 A diagram illustrating the structure of the solid-state imaging element in the aforementioned imaging device.

[0054] Figure 3 The circuit diagram shows the pixels of the aforementioned solid-state imaging element.

[0055] Figure 4 This is a conceptual diagram used to explain the signal processing in the pixels mentioned above.

[0056] Figure 5 A conceptual diagram illustrating the structure of a pixel in the second embodiment.

[0057] Figure 6 The circuit diagram for the aforementioned pixels is shown below.

[0058] Figure 7 This is a conceptual diagram used to illustrate the amount of charge that can be processed in each structure of the aforementioned pixels.

[0059] Figure 8 This is a conceptual diagram used to illustrate the signal processing in the pixels mentioned above.

[0060] Figure 9 A conceptual diagram illustrating the structure of a pixel in the third embodiment.

[0061] Figure 10 The circuit diagram for the aforementioned pixels is shown below.

[0062] Figure 11 This is a conceptual diagram used to illustrate the amount of charge that can be processed in each structure of the aforementioned pixels.

[0063] Figure 12 This is a conceptual diagram used to illustrate the signal processing in the pixels mentioned above. Detailed Implementation

[0064] The solid-state imaging element in this embodiment includes:

[0065] A pixel having at least one photoelectric conversion element that performs photoelectric conversion on input light to generate signal charge, a floating node portion that transfers the signal charge from the at least one photoelectric conversion element, and a reset portion that resets the signal charge of the floating node portion.

[0066] A first circuit, which is connected to the aforementioned pixel; and

[0067] The second circuit is connected to the first circuit described above.

[0068] The amount of charge that can be processed by a single input in the aforementioned floating node section, i.e., the first charge, is less than the amount of charge that can be processed by a single input in the aforementioned at least one photoelectric conversion element, i.e., the second charge.

[0069] The first circuit controls the pixel to perform multiple first combination operations for a single input to the at least one photoelectric conversion element, the first combination operations including:

[0070] The reset of the signal charge of the aforementioned floating node,

[0071] The transfer of signal charge from at least one photoelectric conversion element to the floating node, and

[0072] The voltage signal is read from the pixel, and the voltage signal corresponds to the amount of charge of the signal charge transferred to the floating node.

[0073] The second circuit described above couples a signal corresponding to the voltage signal read from the pixel in each of the first combined operations for a single input to the at least one photoelectric conversion element.

[0074] In this way, by making the first charge amount smaller than the second charge amount and selecting a structure that performs multiple first combination operations in a single input to the photoelectric conversion element, even if the second charge amount (i.e., the amount of signal charge that the pixel can process in a single input) is increased, the increase in noise generated by floating nodes and the like can be suppressed. That is, according to the above structure, the amount of signal charge that the pixel can process can be increased while suppressing the increase in noise in the signal read from the pixel.

[0075] Among the aforementioned solid-state imaging elements,

[0076] The first circuit controls the pixel to read the voltage signal (i.e., the reset signal) when the floating node is in the reset state during each of the first combination operations, and to read the voltage signal (i.e., the transferred charge signal) when the floating node is in the state where the signal charge is transferred from the at least one photoelectric conversion element after the reset signal is read.

[0077] During each of the first combination operations, the second circuit generates a difference signal between the transferred charge signal and the reset signal as a signal corresponding to the voltage signal.

[0078] In this way, by selecting a structure that generates a difference signal (corresponding to a voltage signal) between the transferred charge signal and the reset signal during each first combination operation in the first circuit, reset noise such as thermal noise in the coupled signals (difference signals) in the second circuit can be suppressed, thereby obtaining higher quality captured images.

[0079] In addition, among the aforementioned solid-state imaging elements,

[0080] The aforementioned pixels have multiple of the aforementioned photoelectric conversion elements.

[0081] The first charge quantity mentioned above can be a quantity corresponding to the number of the aforementioned photoelectric conversion elements.

[0082] According to the structure involved, when multiple photoelectric conversion elements accumulate signal charge to a second charge amount through a single input, the difference between the charge amounts of the signal charge transferred to the floating node of each first combined operation is suppressed. As a result, input conversion noise (including quantization error, etc.) in the signal (image signal, etc.) output from the solid-state imaging element can be suppressed.

[0083] In addition, among the aforementioned solid-state imaging elements,

[0084] The aforementioned pixel may have a gain switching unit, which switches the conversion gain of the voltage signal of the signal charge transferred to the aforementioned floating node between a first conversion gain and a second conversion gain lower than the first conversion gain by changing the aforementioned first charge amount.

[0085] Based on the structure involved, it is possible to select the voltage signal for image processing from the voltage signals obtained from each gain according to the amount of light input, thereby improving the image quality in the captured image.

[0086] in this case,

[0087] The first circuit controls the pixel to perform the reset, transfer, and read operations in each of the first combination operations under the second conversion gain state, and performs the second combination operation under the first conversion gain state between the reset and read operations in the first group of first combination operations. The second combination operation includes: the reset, the transfer, and the read operation.

[0088] The second circuit described above outputs a signal corresponding to the voltage signal read in the second combined operation by inputting the amount of the signal charge generated in the at least one photoelectric conversion element at a time. Alternatively, it may couple and output a signal corresponding to the voltage signal read in each of the first combined operations.

[0089] Depending on the structure involved, for example, when the amount of input light is small, all the signal charge converted by multiple photoelectric conversion elements is transferred to the floating node in the first conversion gain state at one time. By applying the signal output from the signal processing circuit to image processing, high-quality images can be obtained even when shooting in low-light conditions such as dim scenes.

[0090] In addition, the imaging device of this embodiment includes:

[0091] Optical systems; and

[0092] Any of the solid-state imaging elements described above;

[0093] The aforementioned solid-state imaging element has a pixel array in which the pixels are arranged in a matrix.

[0094] The aforementioned optical system images the subject on the aforementioned pixel array.

[0095] Based on the structure involved, it is possible to increase the amount of signal charge that the pixel can process while suppressing the increase of noise in the signal read from the pixel, thereby obtaining high-quality captured images.

[0096] In addition, the imaging device of this embodiment includes:

[0097] A solid-state imaging element having a plurality of pixels arranged in a matrix, each pixel having at least one photoelectric conversion element for photoelectric conversion of input light to generate signal charge and a floating node portion for transferring the signal charge from the at least one photoelectric conversion element;

[0098] The first circuit is connected to each pixel of the aforementioned solid-state imaging element;

[0099] The second circuit is connected to the first circuit described above;

[0100] An optical system that images the object being photographed on the aforementioned solid-state imaging element; and

[0101] The output section outputs the captured images to the outside.

[0102] The amount of charge that can be processed in a single input at the floating node portion of each pixel is less than the amount of charge that can be processed in a single input at at least one photoelectric conversion element of that pixel.

[0103] The first circuit controls the pixel to perform multiple first combination operations on a single input to the at least one photoelectric conversion element via the optical system, the first combination operations including:

[0104] The transfer of signal charge from at least one photoelectric conversion element to the floating node and the reading of voltage signal from the pixel, wherein the voltage signal corresponds to the amount of signal charge transferred to the floating node.

[0105] The second circuit described above, for a single input to the at least one photoelectric conversion element, couples the signal corresponding to the voltage signal read from each of the pixels in each of the first combined operations, pixel by pixel.

[0106] The output unit outputs the captured image generated based on the coupled signal to the outside.

[0107] Based on the structure involved, it is possible to suppress the increase of noise in the signal read from each pixel while increasing the amount of signal charge that the pixel can process, thereby enabling the output unit to output (display, etc.) high-quality captured images.

[0108] In addition, the aforementioned filming device,

[0109] It has a mode switching unit that allows for switching shooting modes.

[0110] The aforementioned mode switching unit can also switch between a first mode that performs multiple of the aforementioned first combination operations and a second mode that performs one set of the aforementioned first combination operations.

[0111] Depending on the structure involved, the shooting mode can be selected (switched) according to the shooting scene. This can reduce the number of first combination operations, thereby saving power for solid imaging elements, etc., or increase the number of first combination operations to improve the image quality of images captured in dimly lit places, etc.

[0112] As described above, according to this embodiment, a solid-state imaging element that can increase the amount of signal charge that a pixel can process while suppressing the increase of noise in the signal read from the pixel, and an imaging device equipped with a solid-state imaging element can be provided.

[0113] Hereinafter, the first embodiment of the present invention will be described with reference to the accompanying drawings.

[0114] The imaging device 100 of the first embodiment, as shown in the example... Figures 1-3 As shown, the device includes an optical system 101a and a solid-state imaging element 1. The solid-state imaging element 1 includes a pixel 20, a scanning circuit (first circuit) 3 connected to the pixel 20, and a signal processing circuit (second circuit) 4 connected to the scanning circuit 3. The pixel 20 has at least one photoelectric conversion element 21 that performs photoelectric conversion on input light to generate signal charge, a floating node F that transfers signal charge from the at least one photoelectric conversion element 21, and a reset unit R that resets the signal charge of the floating node F. This imaging device 100 is a device capable of photographing objects, such as a digital camera, smartphone, or tablet computer. The imaging device 100 of this embodiment could be, for example, a smartphone.

[0115] Specifically, such as Figure 1 As shown, the shooting device 100 includes a shooting unit 101, a control unit 102, a non-volatile memory 103, a working memory 104, an operation unit 105, a display unit (output unit) 106, a recording medium 107, a connection unit 108, a short-range wireless communication unit 109, a public network connection unit 110, a microphone 111, and a speaker 112.

[0116] Under the control of the control unit 102, the imaging unit 101 converts the image of the subject object imaged by the optical system 101a into an electrical signal, performs noise reduction processing, and outputs the digital data as image data of the captured image. Specifically, the imaging unit 101 includes: an optical system 101a composed of at least one optical element such as a lens, and a solid-state imaging element 1 that converts the image of the subject object imaged by the optical system 101a into an electrical signal (i.e., captures the image).

[0117] Solid-state imaging element 1 can be embedded in smartphones, digital cameras, etc., and is an element used to photograph objects. In this embodiment, solid-state imaging element 1 can be a CMOS image sensor, for example.

[0118] Specifically, such as Figure 2 As shown, the solid-state imaging element 1 includes a pixel array 2 having multiple pixels 20, a scanning circuit 3 connected to each pixel 20 of the pixel array 2, and a signal processing circuit 4 connected to the scanning circuit 3. The pixel array 2, the scanning circuit 3, and the signal processing circuit 4 are disposed on the same semiconductor substrate or on multiple semiconductor substrates electrically connected.

[0119] Pixel array 2 has a plurality of pixels 20 arranged in a matrix-like two-dimensional configuration. Furthermore, for the plurality of pixels 20 arranged in a matrix, pixel array 2 has pixels arranged in each row and respectively along the row direction. Figure 2 Multiple row signal lines L1 extending in the left and right directions, and configured according to each column and respectively along the column direction (in the left and right directions). Figure 2 Multiple column signal lines L2 extending in the vertical direction of the scanning circuit 3. These multiple row signal lines L1 are respectively connected to the first scanning circuit 31 of the scanning circuit 3, and the multiple column signal lines L2 are respectively connected to the second scanning circuit 32 of the scanning circuit 3.

[0120] For example Figure 3 As shown, each of the plurality of pixels 20 has at least one photoelectric conversion element 21 and a floating node 22 for transferring the signal charge generated by the at least one photoelectric conversion element 21. In the solid-state imaging element 1 of this embodiment, the pixel 20 has a photoelectric conversion element 21, which may be, for example, a photodiode. In addition, in the pixel 20 of this embodiment, the floating node 22 constitutes the floating node portion F described above.

[0121] The charge that can be processed by a single input in the floating node 22 is the first charge C1 (refer to...). Figure 4 The charge amount that can be processed by a single input in the photoelectric conversion element 21, i.e., the second charge amount C2 (refer to...) Figure 4 In this context, a single input in floating node 22 refers to a single transfer of signal charge from photoelectric conversion element 21, and a single input in photoelectric conversion element 21 refers to a single exposure during shooting. Furthermore, in this embodiment, "processable charge amount" refers to the maximum value of charge that ensures the quality of the obtained captured image (image data). This value is defined by the input dynamic range of each structure after the scanning circuit 3, signal processing circuit 4, and signal processing circuit 4, and is sometimes different from "maximum charge amount." The aforementioned "maximum charge amount" refers to the maximum value of charge that can be accumulated or stored in the structure without considering the quality (noise, etc.) of the obtained captured image.

[0122] In addition, each pixel 20 includes a transfer transistor 23 connecting the photoelectric conversion element 21 and the floating node 22, a reset transistor 24 connecting the floating node 22 and the reset power supply (reset potential) VDD1, an amplifying transistor 25 converting the signal charge of the floating node 22 into a voltage signal, and a selection transistor 26 connecting the amplifying transistor 25 and the column signal line L2. Various drive signals φRES, φTX, and φSEL are input from the first scan circuit 31 of the scan circuit 3 to these transfer transistors 23, reset transistors 24, and selection transistors 26 via the row signal line L1.

[0123] In pixel 20, reset transistor 24 constitutes the aforementioned reset section R. Furthermore, the gate electrode of amplifying transistor 25 is connected to the floating node 22, while its drain electrode is connected to the power supply VDD2. This amplifying transistor 25 serves as the input section of a readout circuit (a so-called source follower (sensor internal amplifier) ​​SF) that converts the amount of signal charge accumulated at the floating node 22 into a voltage signal and reads it out (outputs) at a predetermined gain. That is, since the source electrode of amplifying transistor 25 is connected to the column signal line L2 via select transistor 26, it constitutes a constant current source and a source follower SF connected to one end of the column signal line L2.

[0124] Multiple row signal lines L1 respectively send a reset indication signal φRES, a charge transfer signal φTX, and a selection signal φSEL output from the first scanning circuit 31 to each connected pixel 20.

[0125] Among them, the reset indication signal φRES is a signal of a switch reset transistor 24, which is used to reset the charge (signal charge) of each pixel 20 (more specifically, floating node 22). The charge transfer signal φTX is a signal of a switch transfer transistor 23, which is used to transfer the signal charge of the photoelectric conversion element 21 to the floating node 22. The selection signal φSEL is a signal of a switch selection transistor 26, which is used to convert the amount of signal charge of the floating node 22 into a voltage signal by the amplification transistor 25 and read it to the column signal line L2.

[0126] Multiple column signal lines L2 are respectively connected to each pixel 20 of the corresponding column, and the voltage signal output from the pixel 20 is sent to the second scanning circuit 32.

[0127] The scanning circuit 3 includes a first scanning circuit 31 and a second scanning circuit 32. The first scanning circuit 31 controls each pixel 20 of the pixel array 2 by outputting a reset indication signal φRES, a charge transfer signal φTX, and a selection signal φSEL to each pixel 20. The second scanning circuit 32 removes noise from the voltage signals read from each pixel 20, performs A / D (Analog / Digital) conversion on the read voltage signals, and sends the converted signals to the signal processing circuit 4 in sequence.

[0128] The signal processing circuit 4 is a part that performs various processing on the signals output by the second scanning circuit 32. In this embodiment, the signal processing circuit 4 may be, for example, an ISP (Image Signal Processor) within the sensor.

[0129] In the solid-state imaging element 1 described above, the scanning circuit 3 controls the pixel 20 to perform multiple first combination operations for a single input to the photoelectric conversion element 21. These first combination operations include: resetting the signal charge of the floating node 22, transferring the signal charge from the photoelectric conversion element 21 to the floating node 22, and reading a voltage signal from the pixel 20, the voltage signal corresponding to the amount of signal charge transferred to the floating node 22. Furthermore, the signal processing circuit 4, for each input to the photoelectric conversion element 21, couples the signal corresponding to the voltage signal read from the pixel 20 in each of the first combination operations and outputs the coupled signal.

[0130] Furthermore, when reading voltage signals from pixel 2, scanning circuit 3 controls pixel 20 to read the voltage signal (i.e., reset signal) when floating node 22 is in a reset state, and the voltage signal (i.e., transferred charge signal) when floating node 22 is in a state of signal charge transfer from photoelectric conversion element after the reset signal is read. Additionally, signal processing circuit 4 generates a difference signal between the transferred charge signal and the reset signal as a signal corresponding to the voltage signal during each first combination operation. That is, in solid-state imaging element 1, when reading voltage signals from each pixel 20, so-called correlated double sampling (CDS) is performed.

[0131] Below, also refer to Figure 4 To provide a more specific explanation, Additionally, Figure 4 In the example shown, the first charge C1 of the photoelectric conversion element 21 is Q1, and the first charge C1 of the floating node 22 is Q2.

[0132] In Step 1, when the imaging device 100 captures an image of the object, it is imaged onto the pixel array 2. That is, light (input light) is input to the photoelectric conversion element 21 of each pixel 20. Thus, the photoelectric conversion element 21 performs photoelectric conversion on the input light, generating a signal charge corresponding to the amount of input light. Figure 4 In the example shown, the signal charge (Q1, which is equal to the first charge C1) accumulates in the photoelectric conversion element 21. In this state, the floating node 22 is reset to the reset potential (the potential of the reset power supply VDD1) by switching the reset transistor 24. At this time, the voltage signal, i.e. the reset signal RL1, is read from the pixel 20 and recorded in the second scanning circuit 32.

[0133] Next, in Step 2, the signal charge accumulated in the photoelectric conversion element 21 is transferred to the switching transistor 23. Figure 4 In the example shown, the signal charge (Q1) is transferred to the floating node 22. At this time, since the second charge C2 of the floating node 22 is less than the first charge C1 of the photoelectric conversion element 21, not all the signal charge accumulated in the photoelectric conversion element 21 is transferred to the floating node 22, and a portion ( Figure 4 In the example shown, the signal charge (Q3) remains on the photoelectric conversion element 21. The amount of signal charge transferred from the photoelectric conversion element 21 to the floating node 22 is Q2, and Q3 = Q1 - Q2.

[0134] In this state, the switch selects transistor 26. At this time, the charge Q2 of the signal charge of floating node 22 is converted into a transfer charge signal (voltage signal) SL1 through the source follower SF and output to column signal line L2, and recorded in the second scan circuit 32.

[0135] Next, in Step 3, the signal charge accumulated in the floating node 22 is reset once by switching the reset transistor 24. At this time, the voltage signal, i.e. the reset signal RL2, is read from the pixel 20 and recorded in the second scanning circuit 32.

[0136] Furthermore, in Step 4, the signal charge Q3 remaining in the photoelectric conversion element 21 is transferred to the floating node 22 as in Step 2. The transferred charge signal (voltage signal) SL2, which is the result of converting the signal charge Q3 accumulated in the floating node 22 at this time, is read from the pixel and recorded in the second scanning circuit 32.

[0137] In these Steps, the reset of the floating node 22 in Steps 1 and 3, the transfer of signal charge from the photoelectric conversion element 21 to the floating node 22 in Steps 2 and 4, and the reading of the voltage signal (transferred charge amount signal) corresponding to the amount of signal charge transferred and stored in the floating node 22 constitute the first combination operation described above. In each pixel 20 of this embodiment, two sets of first combination operations are performed in one input (shooting).

[0138] In addition, Figure 4 In the example shown, due to the two sets of first combination operations, all signal charge accumulated in the photoelectric conversion element 21 during one input is transferred to the floating node 22, and the photoelectric conversion element 21 becomes empty, but this structure is not limited to this one. Alternatively, if it does not become empty after two transfers, Step 3 and Step 4 can be repeated a specified number of times (the number of times corresponding to the second charge C2 of the photoelectric conversion element 21, i.e., the number of times that all signal charge accumulated in the photoelectric conversion element 21 is transferred). In other words, the first combination operation can also be performed in three or more sets.

[0139] After performing Steps 1 to 4 as described above (i.e., performing the two sets of first combination operations as described above), the signal processing circuit 4 generates the difference signal (SL1-RL1) between the transferred charge signal SL1 of Step 2 and the reset signal RL1 of Step 1, and creates the difference signal (SL2-RL2) between the transferred charge signal SL2 of Step 4 and the reset signal RL2 of Step 3, and couples these difference signals together. Furthermore, the signal processing circuit 4 couples this signal (Signal = (SL1-RL1) + (SL2-RL2): Refer to...) Figure 4 The output is sent to the subsequent stage (control unit 102, etc.).

[0140] In addition, in this embodiment, the source follower SF and the subsequent signal processing circuit 4 are set to the input dynamic range so as to be able to handle the maximum amplitude of the voltage on the floating node 22 generated by the transfer of signal charge in the first group, which is preferred in terms of ensuring the linearity of the coupled signal.

[0141] The control unit 102 controls each part of the imaging device 100 according to the input signals or programs. Furthermore, the control unit 102 generates an image (image data) based on the signals output from the solid-state imaging element 1 (signals that couple the aforementioned differential signals to each other) and outputs it to the display unit 106. However, the overall configuration of the imaging device 100 is not limited to the control unit 102 controlling the entire device. It is also possible to control the entire imaging device 100 by having multiple hardware components handle the processing.

[0142] The non-volatile memory 103 is a non-volatile memory that can be electrically erased and recorded. In this embodiment, the non-volatile memory 103 records the OS (operating system) which is the basic software executed by the control unit 102, and the application programs that work with the OS to implement application functions.

[0143] The working memory 104 is used as the image display memory of the display unit 106 and the working area of ​​the control unit 102, etc.

[0144] The operation unit 105 is used by users to input instructions to the shooting device 100. In this embodiment, the operation unit 105 includes a power button for indicating the ON / OFF of the power supply to the shooting device 100 and a touch panel formed on the display unit 106.

[0145] The display unit 106 displays captured images (image data) (outputs them to the outside) and displays text for operation.

[0146] Recording medium 107 records image data output from imaging unit 101.

[0147] The connection part 108 is an interface for connecting to external devices. The imaging device 100 exchanges data with external devices via the connection part 108.

[0148] The short-range wireless communication unit 109 is a communication unit for performing short-range wireless communication. The short-range wireless communication unit 109 consists of an antenna for wireless communication and a modulation / demodulation circuit or communication controller for processing wireless signals.

[0149] The public network connection unit 110 is an interface for public wireless communication. The camera device 100 communicates with other devices for calls via this public network connection unit 110. At this time, the control unit 102 realizes the aforementioned call by inputting and outputting voice signals through the microphone 111 and the speaker 112. In this embodiment, the public network connection unit 110 is an antenna, and the control unit 102 is connected to the public network through this antenna.

[0150] The solid-state imaging element 1 of the imaging device 100 described above includes a pixel 20, a scanning circuit (first circuit) 3 connected to the pixel 20, and a signal processing circuit (second circuit) 4 connected to the scanning circuit 3. The pixel 20 has a photoelectric conversion element 21 that generates signal charge by photoelectric conversion of input light, a floating node portion F that transfers signal charge (in this embodiment, a floating node 22) from the photoelectric conversion element 21, and a reset portion R (in this embodiment, a reset transistor 24) that resets the signal charge of the floating node portion F. Furthermore, the amount of charge that can be processed by a single input in the floating node portion F, i.e., the first charge, is less than the amount of charge that can be processed by a single input in the photoelectric conversion element 21, i.e., the second charge. In addition, the scanning circuit 3 controls the pixel 20 to perform multiple first combination operations for a single input to the photoelectric conversion element 21. The first combination operations include resetting the signal charge of the floating node portion F, transferring the signal charge from the photoelectric conversion element 21 to the floating node portion F, and reading voltage signals from the pixel. The voltage signals (SL1, SL2) correspond to the amount of signal charge transferred to the floating node portion F. Furthermore, for each input to the photoelectric conversion element 21, the signal processing circuit 4 couples the signal corresponding to the voltage signal read from the pixel 20 in each first combination operation (see reference). Figure 4 In the context, Signa l = (SL1-RL1)+(SL2-RL2)).

[0151] In this way, by configuring the first charge C1 to be less than the second charge C2 and performing multiple first combination operations in a single input to the photoelectric conversion element 21, even if the second charge C2 (i.e., the amount of signal charge that the pixel 20 can process in a single input) is increased, the increase in noise generated at the floating node F and the like can be suppressed. That is, according to the above configuration, the increase in noise in the signal read from the pixel 20 can be suppressed, and the amount of signal charge that the pixel 20 can process can be increased. As a result, in the imaging device 100 equipped with the solid-state imaging element 1, a high-quality captured image is output (displayed, etc.) in the display unit (output unit) 106.

[0152] Furthermore, in the solid-state imaging element 1 of this embodiment, the scanning circuit (first circuit) 3 controls the pixel 20 to read the voltage signal (i.e., reset signal (RL1, RL2) when the floating node part F (in this example, the floating node 22) is in the reset state during each first combination operation, and to read the voltage signal (i.e., transferred charge signal (SL1, SL2) when the floating node part F is in a state where the signal charge is transferred from the photoelectric conversion element 21 after the reset signal is read. Additionally, the signal processing circuit (second circuit) 4 generates differential signals ((SL1-RL1), (SL2-RL2)) between the transferred charge signal and the reset signal as signals corresponding to the voltage signal during each first combination operation. Thus, by configuring the scanning circuit 3 to generate differential signals (signals corresponding to the voltage signal) between the transferred charge signal and the reset signal during each first combination operation, reset noise such as thermal noise in the signals (differential signals) coupled in the signal processing circuit 4 can be suppressed, thereby obtaining a higher quality captured image.

[0153] Next, refer to Figures 5-8 The second embodiment of the present invention will be described in detail. The same reference numerals are used for the same configuration as those in the first embodiment described above, and the configurations that are different from those in the first embodiment will be described in detail.

[0154] In the imaging device 100 of this embodiment, such as Figure 5 As shown, each pixel 20A of the solid-state imaging element 1 has multiple (four in this embodiment) photoelectric conversion elements 21. In this pixel 20A, when the first photoelectric conversion element 21 is designated as PD0, the second photoelectric conversion element 21 as PD1, the third photoelectric conversion element 21 as PD2, and the fourth photoelectric conversion element 21 as PD3, these first to fourth photoelectric conversion elements PD0 to PD3 are arranged in a matrix, as follows: Figure 6 As shown, each photoelectric conversion element PD0, PD1, PD2, and PD3 is connected to the floating node 22 via the transfer transistor 23. Furthermore, in the pixel 20A of this embodiment, the floating node 22 also constitutes a floating node section F, and the reset transistor 24 constitutes a reset section R.

[0155] In the solid-state imaging element 1 mentioned above, such as Figure 5 As shown, the multiple photoelectric conversion elements PD0 to PD3 of each pixel 20A are divided into multiple groups g1 and g2 (two in this embodiment), and the signals of each group g1 and g2 are processed. Furthermore, in Figure 5 In the diagram, the types of smoke are used to represent the g1 and g2 groups of photoelectric conversion elements PD0, PD1, PD2, and PD3.

[0156] In this embodiment, the first photoelectric conversion element PD0 and the second photoelectric conversion element PD1 are designated as the first group g1, and the third photoelectric conversion element PD2 and the fourth photoelectric conversion element PD3 are designated as the second group g2. In this example, as... Figure 7 As shown, the processable charge (third charge) C3 obtained by adding the processable charge of the first photoelectric conversion element PD0 to the processable charge of the second photoelectric conversion element PD1 is Q11, the processable charge (fourth charge) C4 obtained by adding the processable charge of the third photoelectric conversion element PD2 to the processable charge of the fourth photoelectric conversion element PD3 is Q12, and the first charge C1 of the floating node 22 is Q13. At this time, the second charge C2 of the multiple photoelectric conversion elements PD0, PD1, PD2, and PD3 is the value obtained by adding the third charge C3 and the fourth charge C4 (Q11 + Q12). That is, when a pixel 20A has multiple photoelectric conversion elements PD0, PD1, PD2, and PD3, the second charge C2 is the value obtained by adding the processable charge of each photoelectric conversion element PD0, PD1, PD2, and PD3 (total value).

[0157] In this solid-state imaging element 1, the signal is processed as follows during imaging.

[0158] In Step 1, when the imaging device 100 takes a picture, the image of the object is formed on the pixel array 2. That is, light (input light) is input to multiple photoelectric conversion elements PD0, PD1, PD2, and PD3 in each pixel 20A. Thus, each photoelectric conversion element PD0, PD1, PD2, and PD3 performs photoelectric conversion on the input light, accumulating a signal charge (in the amount of light corresponding to the amount of input light)... Figure 8 In the example shown, signal charges Q11 and Q12 (third charge C3 and fourth charge C4) are accumulated in the first group g1 and the second group g2, respectively. In this state, by switching the reset transistor 24, the floating node 22 is reset to the reset potential (the potential of the power supply VDD1), and the voltage signal at this time, i.e., the reset signal RL1, is read from the pixel 20A and recorded in the second scan circuit 32.

[0159] Next, in Step 2, by switching the transfer transistors 23 of the first photoelectric conversion element PD0 and the second photoelectric conversion element PD1 respectively, the signal charge Q11 accumulated in the first photoelectric conversion element PD0 and the second photoelectric conversion element PD1 is transferred to the floating node 22. At this time, since the signal charge Q12 accumulated in the third photoelectric conversion element PD2 and the fourth photoelectric conversion element PD3 is not transferred to the floating node 22, under one input to the floating node 22, not all the signal charge accumulated in the first to fourth photoelectric conversion elements PD0 to PD3 is transferred, and a portion (in Figure 8 In the example shown, the signal charge Q12 accumulated in the third electrical conversion element PD2 and the fourth photoelectric conversion element PD3 remains in the photoelectric conversion elements PD2 and PD3. By switching the selection transistor 26 in this state, the signal charge Q11 of the floating node 22 at this time is converted into a voltage signal (transfer charge signal) SL1 through the source follower SF, and output to the column signal line L2, which is recorded in the second scan circuit 32.

[0160] Next, in Step 3, by switching the reset transistor 24, the signal charge accumulated in the floating node 22 is reset once, and the voltage signal at this time, i.e. the reset signal RL2, is read from the pixel 20A and recorded in the second scan circuit 32.

[0161] Furthermore, in Step 4, by switching on and off the transfer transistors 23 of the third electrical conversion element PD2 and the fourth photoelectric conversion element PD3 respectively, the signal charge Q12, which was not transferred to the floating node 22 in Step 2 but remained in the third photoelectric conversion element PD2 and the fourth photoelectric conversion element PD3, is transferred to the floating node 22. Thus, the transferred charge signal (voltage signal) SL2 obtained by converting the signal charge Q12 remaining in the floating node 22 is read from the pixel 20A and recorded in the second scanning circuit 32.

[0162] Here, according to the design of each photoelectric conversion element PD0, PD1, PD2, PD3 and floating node 22, sometimes there is residual signal charge in the first photoelectric conversion element PD0 and the second photoelectric conversion element PD1 in Step 2. However, in Step 4, when each transfer transistor 23 of the third photoelectric conversion element PD2 and the fourth photoelectric conversion element PD3 is switched, each transfer transistor 23 of the first photoelectric conversion element PD0 and the second photoelectric conversion element PD1 is also switched, thereby enabling the reading of the residual signal charge.

[0163] In this embodiment, in each Step, the reset of the floating node 22 in Step 1 and 3, the transfer of signal charge from the photoelectric conversion elements PD0, PD1, PD2, and PD3 of each group g1 and g2 in Step 2 and 4 to the floating node 22, and the reading of the voltage signal (transferred charge amount signal) corresponding to the amount of signal charge transferred and accumulated in the floating node 22 constitute the first combination operation. In each pixel 20A of this embodiment, two sets of first combination operations are also performed in one input (shooting).

[0164] If Steps 1 through 4 are executed (i.e., two sets of first combination operations are performed), then the signal processing circuit 4 generates the differential signal (SL1-RL1) between the transferred charge signal SL1 of Step 2 and the reset signal RL1 of Step 1, and generates the differential signal (SL2-RL2) between the transferred charge signal SL2 of Step 4 and the reset signal RL2 of Step 3, and couples these differential signals together. Then, the signal processing circuit 4 converts the coupled signal (LCG signal = (SL1-RL1) + (SL2-RL2) to (see reference). Figure 8 The output is configured to the subsequent stage (control unit 102, etc.).

[0165] Similar to the first embodiment, the solid-state imaging element 1 of the imaging apparatus 100 described above, by configuring the first charge C1 to be less than the second charge C2 (in this embodiment, it is the value obtained by adding the third charge C3 and the fourth charge C4) and performing multiple first combination operations in a single input to multiple photoelectric conversion elements PD0, PD1, PD2, and PD3, even if the second charge C2 (i.e., the amount of signal charge that the pixel 20 can handle in a single input) is increased, the increase in noise generated in the floating node (in this embodiment, the floating node 22) and the like can be suppressed. In other words, the solid-state imaging element 1 of this embodiment can suppress the increase in noise in the signal read from the pixel 20 and increase the amount of signal charge that the pixel 20 can handle. Therefore, in the imaging apparatus 100 equipped with the solid-state imaging element 1, a high-quality captured image is output (displayed, etc.) in the display unit (output unit) 106.

[0166] Furthermore, in the solid-state imaging element 1 of this embodiment, the pixel 20A has a plurality of photoelectric conversion elements PD0, PD1, PD2, PD3, and the first charge C1 is the amount corresponding to the number of photoelectric conversion elements PD0, PD1, PD2, PD3 (specifically, the amount of processable charge C3, C4 corresponding to each group g1, g2 of photoelectric conversion elements 21).

[0167] According to this configuration, when multiple photoelectric conversion elements PD0, PD1, PD2, and PD3 accumulate signal charge to a second charge amount C2 through a single input, the difference in the amount of signal charge transferred to each floating node F (floating node 22 in this embodiment) of the first combined operation can be suppressed, thereby suppressing input conversion noise (including quantization errors, etc.) in the signal (image signal, etc.) output from the solid-state imaging element 1. Details are as follows.

[0168] As in the first embodiment, if the difference between the amount of signal charge transferred to the floating node F in the first combination operation of the first group and the amount of signal charge transferred to the floating node F in the first combination operation of the second group is large, the input dynamic range of the subsequent reading system (A / D converter, etc.) must be set to correspond to the first combination operation with the large amount of charge. In this case, the input dynamic range becomes larger, and as a result, the input conversion noise (including the quantization error of A / D conversion) increases.

[0169] Therefore, in the solid-state imaging element 1 of this embodiment, the number of photoelectric conversion elements PD0, PD1, PD2, and PD3 that are transferred simultaneously is controlled to suppress the difference between the amount of signal charge transferred to the floating node 22 of each first combined operation.

[0170] Specifically, in each pixel 20A of this embodiment, the four photoelectric conversion elements PD0, PD1, PD2, and PD3 are configured to be divided into a first group g1 and a second group g2 in pairs. For a single input to the multiple photoelectric conversion elements PD0, PD1, PD2, and PD3, the signal charge is transferred to the floating node 22 in groups g1 and g2 (75,000 electrons are transferred each time). Therefore, the input dynamic range of the subsequent readout system (A / D converter, etc.) can be suppressed (reduced), thereby suppressing input conversion noise (including quantization errors, etc.), resulting in high-quality captured images.

[0171] Next, refer to Figures 9-12 The third embodiment of the present invention will be described, with the same reference numerals used for components that are the same as those in the first and second embodiments described above, and detailed descriptions provided for components that are different from those in the first and second embodiments.

[0172] In the imaging device 100 of this embodiment, similar to the second embodiment, each pixel 20B of the solid-state imaging element 1 has multiple (four in this example) photoelectric conversion elements PD0, PD1, PD2, PD3 (see reference). Figure 9 Additionally, such as Figure 10As shown, pixel 20B has a holding capacitor 27 and a switching transistor 28. The holding capacitor 27 is a capacitor connected to the floating node 22 via the switching transistor 28 and connected to the reset power supply VDD1 via the reset transistor 24.

[0173] Furthermore, the pixel 20B in this embodiment has a gain switching unit G, which switches between high gain (first conversion gain) and low gain (second conversion gain lower than the first conversion gain) to change the conversion gain of the signal charge transferred to the floating node unit F by changing the first charge amount C1 to the voltage signal. In this embodiment, the floating node unit F is composed of a floating node 22 and a holding capacitor 27, and the gain switching unit G is composed of a switching transistor 28. Additionally, the reset unit R is composed of a reset transistor 24.

[0174] In the pixel 20B having the floating node section F and the gain switching section G, by turning the switching transistor 28 OFF, the amount of charge that can be processed in the floating node section F (the first charge) C1 is made equal to the amount of charge that can be processed in the floating node 22, so that the conversion gain when the amount of signal charge accumulated in the floating node section F is converted into a voltage signal by the source follower SF becomes a high gain.

[0175] On the other hand, by turning the switching transistor 28 ON, the amount of charge that can be processed in the floating node F (first charge) C1 is equal to the amount of charge that can be processed in the floating node 22 and the amount of charge that can be processed in the holding capacitor 27 (i.e. the capacitance of the holding capacitor 27), so that the conversion gain when the amount of signal charge accumulated in the floating node F is converted into a voltage signal by the source follower SF becomes low gain.

[0176] In the above pixel 20B, the control pixel 20B performs the reset of the floating node F, the transfer of signal charge to the floating node F, and the reading of the amount of signal charge accumulated in the floating node F in each first combination operation in a low gain state (conversion of the voltage signal to the above charge amount), and performs a second combination operation between the reset and the reading in the first combination operation of the first group, the second combination operation including: the reset, the transfer and the reading are performed in a high gain state.

[0177] In addition, the second scanning circuit 32 outputs a signal corresponding to the voltage signal read in the second group, or in combination with the signal corresponding to the voltage signal read in each first combination operation, based on the amount of signal charge generated in each photoelectric conversion element PD0, PD1, PD2, PD3 through a single input.

[0178] In the solid-state imaging element 1 described above, similarly to the second embodiment, the multiple photoelectric conversion elements PD0, PD1, PD2, and PD3 of each pixel 20B are divided into multiple (two in this embodiment) groups g1 and g2, and the signals of each group g1 and g2 are processed (see [reference]). Figure 9 Additionally, in Figure 9 In the diagram, the types of smoke are used to represent the g1 and g2 groups of photoelectric conversion elements PD0, PD1, PD2, and PD3.

[0179] In this embodiment, similar to the second embodiment, the first photoelectric conversion element PD0 and the second photoelectric conversion element PD1 are designated as the first group g1, and the third photoelectric conversion element PD2 and the fourth photoelectric conversion element PD3 are designated as the second group g2. In this example, as... Figure 11 As shown, the processable charge (third charge) C3 obtained by adding the processable charge of the first photoelectric conversion element PD0 to the processable charge of the second photoelectric conversion element PD1 is Q21, and the processable charge (fourth charge) C4 obtained by adding the processable charge of the third photoelectric conversion element PD2 to the processable charge of the fourth photoelectric conversion element PD3 is Q22. Similarly to the second embodiment, the second charge C2 is the value obtained by adding the third charge C3 and the fourth charge C4 (Q21 + Q22). That is, when a pixel 20B has multiple photoelectric conversion elements PD0, PD1, PD2, and PD3, the second charge C2 is the value (total value) obtained by adding the processable charge of each photoelectric conversion element PD0, PD1, PD2, and PD3 respectively.

[0180] Furthermore, the first charge C1(HCG) of the floating node F in the high-gain state (i.e., when the switching transistor 28 is OFF) is Q(HCG), and the first charge C1(LCG) of the low-gain state (i.e., when the switching transistor 28 is ON) is Q(LCG) (see reference). Figure 11 Furthermore, in the case of a configuration where the conversion gain can be switched when the signal charge of the floating node F is converted into a voltage signal (transferred charge signal), as in the solid-state imaging element 1 of this embodiment, the maximum value (maximum charge) of the transferred signal charge when the charge transferred from the photoelectric conversion element 21 to the floating node F in the high-gain state is sufficiently greater than the first charge C1 (HCG) is Qmax. However, C1 (LCG) > Qmax > C1 (HCG). Additionally, the maximum charge refers to the maximum value of the charge that can be accumulated or stored in this configuration, regardless of the quality of the captured image (input dynamic range of subsequent circuits, etc.).

[0181] In this solid-state imaging element 1, the signal is processed as follows during imaging.

[0182] In Step 1, when the imaging device 100 takes a picture, the image of the object is formed on the pixel array 2. That is, light (input light) is input to multiple photoelectric conversion elements PD0, PD1, PD2, and PD3 in each pixel 20B. Thus, each photoelectric conversion element PD0, PD1, PD2, and PD3 performs photoelectric conversion on the input light, accumulating a signal charge (in the amount of light corresponding to the amount of input light)... Figure 12 In the example shown, signal charges Q21 and Q22 (third charge C3 and fourth charge C4) are accumulated in the first group g1 and the second group g2, respectively. At this time, by switching the reset transistor 24 while the switching transistor 28 is ON, the floating node part F (floating node 22 and holding capacitor 27) in the low gain state is reset to the reset potential. The voltage signal at this time, i.e., the reset signal RL1, is read from the pixel 20B and recorded in the second scanning circuit 32.

[0183] Next, in Step 2, while maintaining the signal charge accumulated by each photoelectric conversion element PD0, PD1, PD2, and PD3, the reset transistor 24 is switched while the switching transistor 28 is OFF, so that the floating node part F (floating node 22) in the high gain state is reset to the reset potential. The voltage signal at this time, i.e., the reset signal RH, is read from the pixel 20B and recorded in the second scanning circuit 32.

[0184] Next, in Step 3, by switching each transfer transistor 23 while the floating node F is in a high-gain state, the signal charge accumulated in each photoelectric conversion element PD0, PD1, PD2, PD3 is transferred to the floating node F.

[0185] At this time, the total amount of signal charge accumulated in all photoelectric conversion elements PD0, PD1, PD2, and PD3 (the sum of the signal charges of each photoelectric conversion element PD0, PD1, PD2, and PD3) is significantly greater than the first charge C1 of the floating node F in the high-gain state. Figure 11 In the example shown, Q(HCG)) is used. Figure 11 In the example shown, when the charge is greater than the maximum charge Qmax, all the signal charge (the signal charge of charge (Q21+Q22)) accumulated in each photoelectric conversion element PD0, PD1, PD2, and PD3 does not transfer to the floating node F, and a portion remains in each photoelectric conversion element PD0, PD1, PD2, and PD3 (in Figure 12 In the example shown, the signal charge residue of charge Q23 remains in the first group g1, and the signal charge residue of charge Q24 remains in the second group g2. Here, Q23 = Q21 - (Qmax / 2), Q24 = Q22 - (Qmax / 2).

[0186] On the other hand, when the total amount of signal charge accumulated in all photoelectric conversion elements PD0, PD1, PD2, and PD3 is less than or equal to the maximum charge Qmax of the floating node part F in the high-gain state, all signal charge accumulated in each photoelectric conversion element PD0, PD1, PD2, and PD3 is transferred to the floating node part F.

[0187] In addition, Figure 12 In the example shown, the maximum charge Qmax is reached when the total charge accumulated in all photoelectric conversion elements PD0, PD1, PD2, and PD3 is equal to the maximum charge Qmax (refer to...). Figure 12 Up to Step 3), all signal charge accumulated in each photoelectric conversion element PD0, PD1, PD2, and PD3 is transferred to the floating node F. However, since the obtained voltage signal has a larger input dynamic range than the subsequent circuits, when the amount of signal charge transferred to the floating node F is greater than the first charge C1 (HCG), i.e., the charge Q (HCG), the voltage signal read in the high-gain state is not used for image generation. The voltage signal read after switching to the low-gain state is used for image generation. On the other hand, when the amount of signal charge transferred to the floating node F is less than or equal to the first charge C1, i.e., the charge Q (HCG), the voltage signal read in the high-gain state is used for image generation.

[0188] Next, by switching the selection transistor 26, the charge amount of the signal charge of the floating node F at this time is converted into a voltage signal (transfer charge signal) SH through the source follower SF, and output to the column signal line L2 and recorded in the second scan circuit 32.

[0189] Next, in Step 4, after the switching transistor 28 is OFF and the floating node F is switched to a low-gain state, the transfer transistors 23 of the first photoelectric conversion element PD0 and the second photoelectric conversion element PD1 are switched on and off, thereby transferring the signal charge accumulated in the first photoelectric conversion element PD0 and the second photoelectric conversion element PD1 to the floating node F. During this transfer, in the high-gain state, signal charge (a portion of the signal charge accumulated in each photoelectric conversion element PD0, PD1, PD2, PD3) is transferred from each photoelectric conversion element PD0, PD1, PD2, PD3 to the floating node F. Therefore, the signal charge in the first photoelectric conversion element PD0 and the second photoelectric conversion element PD1 is not transferred at all (in...). Figure 12 In the example shown, the signal charge of charge Q26 is transferred, leaving a portion of the signal charge (in...). Figure 12In the example shown, the residual charge is Q25 (signal charge). Here, Q25 = Q23 - Q26.

[0190] At this time, since the transfer transistors 23 of the third photoelectric conversion element PD2 and the fourth photoelectric conversion element PD3 remain OFF, the signal charge accumulated in the third photoelectric conversion element PD2 and the fourth photoelectric conversion element PD3 (in Figure 12 In the example shown, the signal charge (Q24) is not transferred to the floating node F but remains in the third photoelectric conversion element PD2 and the fourth photoelectric conversion element PD3.

[0191] Furthermore, by switching the selection transistor 26 in this state, the amount of signal charge at the floating node F at this time (in...) Figure 12 In the example shown, the signal charge Q27 is converted into a transferred charge signal (voltage signal) SL1 by the source follower SF, output to the column signal line L2, and recorded in the second scan circuit 32. Here, Q27 = Qmax + Q26, and Q27 ≥ Q(HCG). Furthermore, in this embodiment, the charge Q27 is a value slightly larger than the first charge C1(LCG) of the floating node F in the low-gain state, i.e., Q(LCG).

[0192] Next, in Step 5, by switching the reset transistor 24, the signal charge accumulated in the floating node F is reset once, and the voltage signal at this time, i.e. the reset signal RL2, is read from the pixel 20B and recorded in the second scanning circuit 32.

[0193] Furthermore, in Step 6, when the floating node F is in a low-gain state, the transfer transistors 23 of the third photoelectric conversion element PD2 and the fourth photoelectric conversion element PD3 are switched on and off respectively, causing the residual signal charge in the third photoelectric conversion element PD2 and the fourth photoelectric conversion element PD3 (in Figure 12 In the example shown, the signal charge (Q24) is transferred to the floating node F. Furthermore, in Step 6, when the transfer transistors 23 of the third photoelectric conversion element PD2 and the fourth photoelectric conversion element PD3 switch on and off, the transfer transistors 23 of the first photoelectric conversion element PD0 and the second photoelectric conversion element PD1 also switch on and off. This transfers the signal charge (Q24) that was not transferred to the floating node F in Step 4 and remains in the first photoelectric conversion element PD0 and the second photoelectric conversion element PD1. Figure 12 In the example shown, a signal charge of Q25 is transferred to the floating node F. As a result, a signal charge product of Q28 exists in the floating node F. Here, Q28 = Q24 + Q25.

[0194] In this state, by switching the selection transistor 26, the charge Q28 of the signal charge of the floating node F is converted into a transfer charge signal SL2 through the source follower SF, and output to the column signal line L2 and recorded in the second scan circuit 32.

[0195] In this embodiment, in each Step, the reset of the floating node F in the low-gain state in Step 1 and 5, the transfer of signal charge from the photoelectric conversion elements PD0, PD1, PD2, and PD3 in Step 4 and 6 to the floating node F in the low-gain state, and the reading of the voltage signal (transfer charge amount signal) corresponding to the amount of signal charge accumulated in the floating node F in the low-gain state constitute the first combination operation. In each pixel 20B of this embodiment, two sets of first combination operations are also performed in one input (shooting).

[0196] In addition, the reset of the floating node F in the high-gain state in Step 2, the transfer of signal charge from each photoelectric conversion element PD0, PD1, PD2, PD3 in Step 3 to the floating node F in the high-gain state, and the reading of the voltage signal (transfer charge amount signal) corresponding to the amount of signal charge accumulated in the floating node F in the high-gain state constitute the second combination operation. The second combination operation is performed between the reset and reading of the first combination operation in the first group, or more specifically, between the reset and the transfer.

[0197] If Steps 1 through 6 are executed, and the transferred charge signal SH read in Step 3 (reading of the second combined operation) is below the voltage signal of the first charge C1 (HCG) of the floating node part F (floating node 22) in the high-gain state, the signal processing circuit 4 generates a differential signal (SH-RL) between the transferred charge signal SH of Step 3 and the reset signal RH of Step 2. This generated differential signal (corresponding to the signal / HCG signa l=(SH-RL) read in the second combined operation) is then referred to... Figure 12 The output is configured to the subsequent stage (control unit 102, etc.).

[0198] On the other hand, when the transferred charge signal SH read in Step 3 (reading of the second combined operation) is greater than the voltage signal of the first charge C1 (HCG) of the floating node part F (floating node 22) in the high-gain state, the signal processing circuit 4 generates the differential signal (SL1-RL1) of the transferred charge signal SL1 of Step 4 and the reset signal RL1 of Step 2, and generates the differential signal (SL2-RL2) of the transferred charge signal SL2 of Step 6 and the reset signal RL2 of Step 5. These differential signals are coupled, and the coupled signal (LCG signal = (SL1-RL1) + (SL2-RL2) is: refer to Figure 12 The output is configured to the subsequent stage (control unit 102, etc.).

[0199] According to the solid-state imaging element 1 of the imaging apparatus 100 described above, by making the first charge C1 (LCG) in the low-gain state less than the second charge C2 (in this embodiment, the total value of the third charge C3 and the fourth charge C4) and by performing multiple first combination operations on a single input to the photoelectric conversion elements PD0, PD1, PD2, and PD3, the increase in noise generated at the floating node part F, etc., can be suppressed when the first charge C1 (LCG) in the low-gain state (i.e., the amount of signal charge that the pixel 20B can process in a single input) is increased. That is, according to the solid-state imaging element 1 of this embodiment, the increase in noise in the signal read from the pixel 20B can be suppressed, and the amount of signal charge that the pixel 20B can process can be increased. As a result, in the imaging apparatus 100 equipped with the solid-state imaging element 1, a high-quality captured image is output (displayed, etc.) in the display unit (output unit) 106.

[0200] Furthermore, in the solid-state imaging element 1 of this embodiment, pixel 20B has a gain switching unit G. This gain switching unit G switches between high gain (first conversion gain) and low gain (second conversion gain lower than the first conversion gain) to convert the amount of signal charge transferred to the floating node unit F by changing the first charge amount C1 into a voltage signal conversion gain. Therefore, a voltage signal for image processing can be selected from the voltage signals (SH-RH, (SL1-RL1)+(SL2-RL2), etc.) obtained from each gain according to the amount of input light, thereby improving the image quality of the captured image.

[0201] Furthermore, in the solid-state imaging element 1 of this embodiment, the scanning circuit (first circuit) 3 controls the pixel 20B to perform multiple first combination operations, and performs a second combination operation between the reset and readout in the first combination operation of the first group. The first combination operation is performed in a low gain (second conversion gain) state for reset, transfer, and readout, and the second combination operation is performed in a high gain (first conversion gain) state for reset, transfer, and readout. In addition, the signal processing circuit (second circuit) 4 outputs a signal (SH-RH) corresponding to the voltage signal SH readout in the second combination operation based on the amount of charge (total amount of charge) of the signal charge generated in the photoelectric conversion elements PD0, PD1, PD2, and PD3 through a single input, or combines the signals (SL1-RL1, SL2-RL2) corresponding to the transferred charge amount signals (voltage signals) SL1 and SL2 readout in each first combination operation ((SL1-RL1)+(SL2-RL2)) and outputs them.

[0202] According to this configuration, for example, when the amount of input light is small and all the signal charges converted by multiple photoelectric conversion devices PD0, PD1, PD2, and PD3 are transferred to the floating node F in a high-gain state at one time, the signal output from the signal processing circuit 4 is used for image processing, so that even when shooting in a dark scene or other conditions with low input light, a high-quality image can be obtained.

[0203] Furthermore, the solid-state imaging element 1 and imaging device 100 of the present invention are not limited to the first to third embodiments described above, and various modifications can be made without departing from the spirit of the present invention. For example, the configuration of another embodiment can be added to the configuration of one embodiment, and a part of the configuration of one embodiment can be replaced by the configuration of another embodiment. Moreover, a part of the configuration of one embodiment can be deleted.

[0204] In the imaging apparatus 100 of the first to third embodiments described above, there is only one imaging mode regarding the number of first combination operations (combination operation number) during imaging (i.e., one input to the pixel array 2), but it is not limited to this configuration. The imaging apparatus 100 may also be configured to have multiple imaging modes. That is, the imaging apparatus 100 may also include a mode switching unit capable of switching imaging modes, which can switch between a first mode that performs multiple first combination operations and a second mode that performs one set of first combination operations.

[0205] In this way, by having a mode switching unit in the shooting device, the shooting mode can be selected (switched) according to the shooting scene. As a result, the number of first combination operations can be reduced to save power of the solid-state shooting element 1, etc., or the number of the first group can be increased to achieve high image quality of the captured image obtained by shooting in darker places, etc.

[0206] Furthermore, by making the first charge C1 of the floating node F smaller than the second charge C2 of at least one photoelectric conversion element 21 such as the solid-state imaging element 1 in the first to third embodiments described above, and performing multiple first combination operations (specifically, including: resetting the signal charge of the floating node F, transferring the signal charge from the photoelectric conversion element 21 to the floating node F, and reading the voltage signal from the pixel 20, the voltage signal corresponding to the charge of the signal charge of the floating node F), it can also be applied to a shooting device of the so-called image plane phase difference detection autofocus method, which determines focus based on the phase difference of the input light to the two photoelectric conversion elements 21 contained in a pixel 20, or the solid-state imaging element of such a shooting device.

[0207] Furthermore, in the imaging device 100 of the first to third embodiments described above, the solid-state imaging element 1 includes a scanning circuit (first circuit) 3 and a signal processing circuit (second circuit) 4, but is not limited to this structure.

[0208] At least one of the first and second circuits can be configured in a different position from the solid-state imaging element 1 in the imaging device. For example, the imaging device 100 may be configured to include the solid-state imaging element 1, the first circuit 3, the second circuit 4, the optical system 101a, and the display unit (output unit) 106, or to include the solid-state imaging element 1 with the first circuit 3, the second circuit 4, the optical system 101a, and the display unit (output unit) 106. With these configurations, it is also possible to suppress the increase of noise in the signal read from each pixel 20 and increase the amount of signal charge that the pixel 20 can handle, thereby outputting (displaying, etc.) a high-quality captured image in the display unit (output unit) 106.

[0209] To illustrate the invention, it has been appropriately and fully described above with reference to the accompanying drawings and embodiments. However, those skilled in the art should understand that the above embodiments can be easily modified and / or improved. Therefore, any modifications or improvements implemented by those skilled in the art that do not depart from the scope of the claims are to be construed as being included within the scope of the claims.

[0210] Explanation of reference numerals in the attached figures:

[0211] 1…Solid-state imaging element, 2…Pixel array, 20, 20A, 20B…Pixels, 21…Photoelectric conversion element, 22…Floating node, 23…Transfer transistor, 24…Reset transistor, 25…Amplifying transistor, 26…Selection transistor, 27…Holding capacitor, 28…Switching transistor, 3…Scanning circuit (first circuit), 31…First scanning circuit, 32…Second scanning circuit, 4…Signal processing circuit (second circuit), 100…Imaging device, 101…Imaging unit, 101a…Optical system, 102…Control unit, 103…Non-volatile memory, 104…Working memory, 105…Operation unit, 106…Display unit (output unit), 107…Recording medium, 108…Connection unit, 109…Near-field wireless communication unit, 110…Public network connection unit, 111…Microphone , 112…speaker, C1…first charge, C2…second charge, C3…third charge, C4…fourth charge, F…floating node, G…gain switching, g1…first group, g2…second group, L1…row signal line, L2…column signal line, PD0…first photoelectric conversion element, PD1…second photoelectric conversion element, PD2…third photoelectric conversion element, PD3…fourth photoelectric conversion element, R…reset section, RH, RL1, RL2…reset signal (voltage signal), SF…source follower, SH, SL1, SL2…transfer charge signal (voltage signal), VDD1…reset power supply, VDD2…power supply, φRES…reset indicator signal, φSEL…selection signal, φTX, φTX1, φTX2, φTX3, φTX4…charge transfer signal.

Claims

1. A solid-state imaging device, characterized by comprising: have: A pixel having at least one photoelectric conversion element for photoelectric conversion of input light to generate signal charge, a floating node portion for transferring the signal charge from the at least one photoelectric conversion element, and a reset portion for resetting the signal charge of the floating node portion; A first circuit is connected to the pixel; as well as The second circuit is connected to the first circuit. The amount of charge that can be processed by a single input in the floating node section, i.e., the first charge, is less than the amount of charge that can be processed by a single input in the at least one photoelectric conversion element, i.e., the second charge. The first circuit controls the pixel to perform multiple first combination operations for a single input to the at least one photoelectric conversion element, the first combination operations including: The reset of the signal charge of the floating node, The transfer of signal charge from the at least one photoelectric conversion element to the floating node, and A voltage signal is read from the pixel, and the voltage signal corresponds to the amount of signal charge transferred to the floating node. The second circuit, for a single input to the at least one photoelectric conversion element, couples a signal corresponding to the voltage signal read from the pixel in each of the first combined operations. The pixel has a gain switching unit that switches the conversion gain of the voltage signal of the signal charge transferred to the floating node between a first conversion gain and a second conversion gain lower than the first conversion gain by changing the first charge amount.

2. The solid-state imaging element according to claim 1, wherein, The first circuit controls the pixel to read the voltage signal (i.e., the reset signal) when the floating node is in a reset state during each of the first combined operations, and to read the voltage signal (i.e., the transferred charge signal) when the floating node is in a state where the signal charge is transferred from the at least one photoelectric conversion element after the reset signal is read. During each of the first combination operations, the second circuit generates a difference signal between the transferred charge signal and the reset signal as a signal corresponding to the voltage signal.

3. The solid-state imaging element according to claim 1 or 2, wherein, The pixel has multiple photoelectric conversion elements. The first charge quantity is a quantity corresponding to the number of the photoelectric conversion elements.

4. The solid-state imaging element according to claim 1 or 2, wherein, The first circuit controls the pixel to perform the reset, transfer, and readout operations in each of the first combination operations under the second conversion gain state, and performs the second combination operation under the first conversion gain state between the reset and readout operations in the first group of first combination operations. The second combination operation includes: the reset, the transfer, and the readout. The second circuit outputs a signal corresponding to the voltage signal read in the second combined operation based on the amount of the signal charge generated in the at least one photoelectric conversion element through a single input, or couples and outputs a signal corresponding to the voltage signal read in each of the first combined operations.

5. An imaging device, characterized by comprising: have: Optical systems; and The solid-state imaging element according to any one of claims 1 to 4, The solid-state imaging element has a pixel array in which the pixels are arranged in a matrix. The optical system images the object being photographed on the pixel array.

6. An imaging device, characterized by comprising: have: A solid-state imaging element having a plurality of pixels arranged in a matrix, each pixel having at least one photoelectric conversion element for photoelectric conversion of input light to generate signal charge and a floating node portion for transferring the signal charge from the at least one photoelectric conversion element; A first circuit is connected to each pixel of the solid-state imaging element; The second circuit is connected to the first circuit; An optical system that images the object on the solid-state imaging element; and The output section outputs the captured images to the outside. The amount of charge that can be processed by a single input in the floating node portion of each pixel, i.e., the first charge, is less than the amount of charge that can be processed by a single input in at least one photoelectric conversion element of that pixel, i.e., the second charge. The first circuit controls the pixel to perform multiple first combination operations for a single input through the optical system to the at least one photoelectric conversion element, the first combination operation including: The transfer of signal charge from the at least one photoelectric conversion element to the floating node, and the reading of a voltage signal from the pixel, wherein the voltage signal corresponds to the amount of signal charge transferred to the floating node. The second circuit, for a single input to the at least one photoelectric conversion element, couples the signal corresponding to the voltage signal read from each pixel in each of the first combined operations, pixel by pixel. The output unit outputs the captured image generated based on the coupled signal to the outside. The pixel has a gain switching unit that switches the conversion gain of the voltage signal of the signal charge transferred to the floating node between a first conversion gain and a second conversion gain lower than the first conversion gain by changing the first charge amount.

7. The imaging device according to claim 5 or 6, wherein, The shooting device has a mode switching unit that can switch shooting modes. The mode switching unit can switch between a first mode for performing the multiple first combined operations and a second mode for performing a set of the first combined operations.

Images