Solid-state imaging device

Abstract

A solid-state imaging device (200) includes a plurality of pixel units (10) arranged in a matrix, each of the plurality of pixel units (10) including: a photoelectric conversion section (100) that generates electric charges through photoelectric conversion and holds a potential corresponding to an amount of the generated electric charges; an initialization section (101) that initializes the potential of the photoelectric conversion section (100); a comparison section (102) that compares the potential of the photoelectric conversion section (100) with a predetermined reference signal and causes the initialization section (101) to perform initialization when they are identical; and a counter section (103) that counts a number of times of initialization performed by the initialization section (101) and outputs a signal corresponding to the number of times as a first signal representing an intensity of incident light.

Description

Technical Field

[0001] This invention relates to a solid-state imaging device. Background Technology

[0002] Patent Document 1 discloses a pulse modulation method for detecting light intensity in a CMOS image sensor. Among the pulse modulation methods, pulse width modulation (PWM) is introduced. PWM is a method that reflects the intensity of incident light into the pulse width.

[0003] Existing technical documents

[0004] Patent documents

[0005] Patent Document 1: Japanese Patent Application Publication No. 2005-252743 Summary of the Invention

[0006] The problem that the invention aims to solve

[0007] However, there is a desire to further increase the speed and precision of existing solid-state imaging devices.

[0008] The purpose of this invention is to provide a solid-state imaging device that can achieve high speed and high precision.

[0009] Methods used to solve problems

[0010] A solid-state imaging device according to one embodiment of the present invention includes a plurality of pixel units arranged in a matrix; each of the plurality of pixel units includes: a photoelectric conversion unit that generates charge through photoelectric conversion and maintains a potential corresponding to the amount of charge generated; an initialization unit that initializes the potential of the photoelectric conversion unit; a comparison unit that compares the potential of the photoelectric conversion unit with a predetermined reference signal, and causes the initialization unit to perform initialization when they match; and a counter unit that counts the number of times the initialization unit has performed initialization, and outputs a signal corresponding to the number of times as a first signal representing the intensity of incident light.

[0011] Invention Effects

[0012] According to the solid-state imaging device of the present invention, high speed and high precision can be achieved. Attached Figure Description

[0013] Figure 1A This is a diagram showing the schematic structure of a solid-state imaging device according to an embodiment.

[0014] Figure 1B yes Figure 1A A diagram illustrating the operation of a solid-state camera device.

[0015] Figure 2AThis is a diagram showing a structural example of the solid-state imaging device according to Embodiment 1.

[0016] Figure 2B It means Figure 2A A diagram showing another structural example of a pixel unit.

[0017] Figure 2C It means Figure 2B The circuit diagram of the SF circuit example in the example.

[0018] Figure 3 This is a time diagram showing an example of the operation of the solid-state camera device in Embodiment 1.

[0019] Figure 4 This is a diagram showing a structural example of the solid-state camera device according to Embodiment 2.

[0020] Figure 5 This is a time diagram showing an example of the operation of the solid-state camera device in Embodiment 2.

[0021] Figure 6A This is a diagram showing a structural example of the solid-state camera device according to Embodiment 3.

[0022] Figure 6B This is a diagram showing another structural example of the solid-state imaging device according to Embodiment 3.

[0023] Figure 7 This is a time diagram showing an example of the operation of the solid-state camera device in Embodiment 3.

[0024] Figure 8 This is a diagram showing a structural example of the solid-state camera device according to Embodiment 4.

[0025] Figure 9 This is a diagram showing a structural example of the solid-state imaging device according to Embodiment 5.

[0026] Figure 10 This is a time diagram showing an example of the operation of the solid-state camera device in Embodiment 5.

[0027] Figure 11A This is a diagram showing a structural example of the solid-state imaging device according to Embodiment 6.

[0028] Figure 11B It means by Figure 11A The diagram shows the voltage waveform generated by the tapered voltage generating section.

[0029] Figure 12 This is a diagram showing a structural example of the solid-state imaging device according to Embodiment 7. Detailed Implementation

[0030] First, a summary of a solid-state imaging device according to a technical solution of the present invention will be described.

[0031] A solid-state imaging device according to one embodiment of the present invention includes a plurality of pixel units arranged in a matrix. Each of the plurality of pixel units includes: a photoelectric conversion unit that generates charge through photoelectric conversion and maintains a potential corresponding to the amount of charge generated; an initialization unit that initializes the potential of the photoelectric conversion unit; a comparison unit that compares the potential of the photoelectric conversion unit with a predetermined reference signal, and causes the initialization unit to perform initialization when they match; and a counter unit that counts the number of times the initialization unit has performed initialization, and outputs a signal corresponding to the number of times as a first signal representing the intensity of the incident light.

[0032] Therefore, the first signal can be generated as a digital signal, making high-speed generation easy. Furthermore, even when the incident light is so strong that the amount of charge generated by the photoelectric conversion exceeds the saturation charge of the photoelectric conversion unit 100, since imaging is performed along with initialization, high-precision imaging can be performed even in very bright conditions.

[0033] For example, the solid-state imaging device may further include an AD conversion unit that performs AD conversion on the potential of the photoelectric conversion unit after final initialization and outputs the AD-converted data as a second signal representing the intensity of the incident light.

[0034] Therefore, the charge that remains in the photoelectric conversion unit after the final initialization is converted by the AD converter and output as the second signal. Since the second signal corresponds to the amount of charge counted less than one time as the first signal, the intensity of the incident light can be determined with higher accuracy.

[0035] For example, the AD conversion unit described above could be configured for each pixel unit.

[0036] This makes it easy to achieve global shutter speed.

[0037] For example, the AD conversion unit described above can be configured for each specified number of pixel units.

[0038] Therefore, if the specified number of pixel units is the pixel units in each column, a rolling shutter can be easily implemented.

[0039] For example, the solid-state imaging device may further include a signal processing unit that generates a third signal representing the intensity of incident light by combining the first signal and the second signal.

[0040] Therefore, both high speed and high precision can be achieved. Regarding high speed, if the number of bits in the counter is reduced and the maximum count value is limited, that is, if the number of countable initializations within one frame is limited, the frame rate can be easily increased. Even with this limitation on the number of bits in the counter, high precision is achieved through the second signal, so both high speed and high precision can be easily realized.

[0041] For example, each of the aforementioned pixel units may further include a feedback circuit that feeds back the potential of the photoelectric conversion unit to the photoelectric conversion unit via the initialization unit when the initialization unit is initialized.

[0042] Therefore, by initializing the potential of the photoelectric converter using feedback, the kTC noise during initialization can be reduced. As a result, good imaging with low noise can be achieved even in low-light conditions.

[0043] For example, the feedback circuit may include an amplification section that outputs the difference between the voltage of the photoelectric conversion unit and a predetermined voltage as an initial voltage to the initialization section.

[0044] Therefore, a feedback path can be formed through the amplification section.

[0045] For example, the initialization unit may include a transistor, one of the source and drain of the transistor is connected to the photoelectric conversion unit, the other of the source and drain of the transistor is input with an initial voltage, the gate of the transistor is connected to an output line representing the comparison result of the comparison unit, and the amplification unit includes an amplifier that outputs the difference between the voltage of the photoelectric conversion unit and a predetermined voltage as the initial voltage to the drain of the transistor.

[0046] Therefore, since the initialization unit is composed of transistors, the initialization operation can be easily controlled at an appropriate speed. Furthermore, the feedback loop can also be constructed using simple circuitry.

[0047] For example, the initialization unit may include a transistor, one of the source and drain of the transistor is connected to the photoelectric conversion unit, the other of the source and drain of the transistor is input with an initial voltage, and the gate of the transistor is connected to an output line representing the comparison result of the comparison unit.

[0048] Therefore, since the initialization unit is composed of transistors, the initialization operation can be easily controlled at an appropriate speed.

[0049] For example, each of the aforementioned pixel units may further include an initialization control unit, which inverts the output line representing the comparison result of the comparison unit, causes the initialization unit to perform initialization, and feeds back the potential of the photoelectric conversion unit to the photoelectric conversion unit via the initialization unit.

[0050] Therefore, it is possible to easily perform control simultaneously without generating timing deviations in the initialization control and feedback control.

[0051] For example, the aforementioned pixel units may each further include: an overflow drain for charge discharge; and a transfer transistor for transferring excess charge from the photoelectric conversion unit to the overflow drain; the potential of the overflow drain is input to the comparison unit as the potential of the photoelectric conversion unit.

[0052] Therefore, the number of components connected to the aforementioned photoelectric conversion unit can be reduced, the voltage of each generated charge can be increased, and for example, the noise effect of the aforementioned AD conversion unit can be relatively suppressed.

[0053] For example, the solid-state imaging device may also include a conical voltage generating unit that, when a signal indicating that the potential of the photoelectric conversion unit is consistent with a predetermined reference signal is input from the comparison unit, generates a conical voltage that changes over time and supplies it to the gate of the transistor.

[0054] This allows for the suppression of kTC noise during initialization. As a result, good video recording with low noise can be achieved even in low-light conditions.

[0055] For example, a solid-state imaging device may include: a first semiconductor substrate having the aforementioned photoelectric conversion unit; and a second semiconductor substrate having the aforementioned counter unit; wherein the first semiconductor substrate and the second semiconductor substrate are stacked.

[0056] Thus, the solid-state camera device 200 can be miniaturized through a stacked structure.

[0057] For example, a solid-state imaging device may include: a first semiconductor substrate having the aforementioned photoelectric conversion unit; and a second semiconductor substrate having the aforementioned AD conversion unit; wherein the first semiconductor substrate and the second semiconductor substrate are stacked.

[0058] Thus, the solid-state camera device 200 can be miniaturized through a stacked structure.

[0059] Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. Furthermore, the embodiments described below represent specific examples of the present invention. The numerical values, shapes, materials, constituent elements, arrangement and connection methods of constituent elements, and drive timing shown in the following embodiments are examples and are not intended to limit the present invention. In addition, constituent elements in the following embodiments that are not described in the independent claims representing the highest concept of the present invention will be described as arbitrary constituent elements. Furthermore, the figures are not necessarily strictly illustrative. In the figures, for substantially identical structures, repeated descriptions will be omitted or simplified.

[0060] Next, the general structure of a solid-state imaging device according to one technical solution of the present invention will be described.

[0061] Figure 1A This is a diagram showing a schematic structure of the solid-state imaging device 200 according to the embodiment. Furthermore, Figure 1B yes Figure 1A A diagram illustrating the operation of the solid-state camera device 200.

[0062] like Figure 1A As shown, the solid-state imaging device 200 includes a plurality of pixel units 10 arranged in a matrix. Each of the plurality of pixel units 10 includes a photoelectric conversion unit 100, an initialization unit 101 for initializing the photoelectric conversion unit 100, and a counter unit 103.

[0063] The photoelectric conversion unit 100 generates charge through photoelectric conversion and maintains a potential corresponding to the amount of charge generated. Regarding the potential of the photoelectric conversion unit 100, for example... Figure 1B As shown, since a charge is generated corresponding to the amount of incident light, the voltage decreases from the initial voltage over time.

[0064] The initialization unit 101 initializes the voltage of the photoelectric conversion unit 100 to an initial voltage when the voltage drops to a reference voltage. For example, the initialization unit 101 initializes the voltage of the photoelectric conversion unit 100 to an initial voltage when the voltage drops to a reference voltage. Figure 1B The timing of the arrow line turns the photoelectric conversion unit 100 into the on state, initializing it. The initial voltage can be, for example, the power supply voltage Vdd, or a preset voltage value. By being initialized to the initial voltage, the initialization unit 101 turns the initialization unit into the off state, deactivating the initialization.

[0065] The counter unit 103 counts the number of times the initialization unit 101 initializes the photoelectric conversion unit 100, and outputs the signal corresponding to that number of times as a first signal representing the intensity of the incident light. Figure 1B In this example, the counter unit 103 starts counting from an initial value of 0 and counts to 3. The digital signal OUT1 is an example of the first signal. Figure 1BThe number in the middle is a numerical value representing the value of 3.

[0066] Thus, the solid-state imaging device 200 generates the digital signal OUT1 for each pixel unit. As a result, high-speed imaging can be performed. Furthermore, in a state where intense light beyond the level at which the photoelectric conversion unit 100 cannot perform photoelectric conversion (i.e., the degree to which the electric charge due to photoelectric conversion exceeds the saturation electric charge) is irradiated on the photoelectric conversion unit 100, the photoelectric conversion unit 100 generates a digital signal while being initialized. Therefore, imaging can also be performed in a bright situation beyond the conversion ability of the photoelectric conversion unit 100.

[0067] (Embodiment 1)

[0068] In Embodiment 1, a more specific structural example of the solid-state imaging device 200 will be described. Figure 2A It is a diagram showing a structural example of the solid-state imaging device 200 of Embodiment 2. Figure 3 It is shown in Figure 2A It is a timing chart showing an operation example of the solid-state imaging device 200 shown in.

[0069] As shown in Figure 2A , Figure 3 The difference between the solid-state imaging device 200 of the present embodiment and the solid-state imaging device 200 shown in Figure 1A is that the pixel unit 10 further includes a comparison unit 102, and the solid-state imaging device 200 further includes a reset voltage generation unit 20, a REF voltage generation unit 30, and a count control signal generation unit 40 connected to the pixel unit 10. In addition, REF refers to a reference signal for comparison. Hereinafter, in order to avoid repetition of the description, the description will be centered on the differences.

[0070] The comparison unit 102 compares the potential of the photoelectric conversion unit 100 with a prescribed reference signal REF, and when they match, causes the initialization unit 101 to perform initialization. Specifically, the comparison unit 102 compares the level relationship between the voltage of the output signal PD of the photoelectric conversion unit 100 and the voltage of the reference signal REF output from the REF voltage generation unit 30, and outputs a low level as the reset signal RST when the voltage of the output signal PD is high, and outputs a high level as the reset signal RST when it is not high.

[0071] The reset voltage generation unit 20 generates the output signal VINI. The output signal VINI can be, for example, the power supply voltage VDD, or can be other voltage values. The output signal VINI is supplied to the photoelectric conversion unit 100 as an initial voltage or a reset voltage via the initialization unit 101.

[0072] The REF voltage generation unit 30 generates a reference signal REF. The reference signal REF may be, for example, the voltage value of the photoelectric conversion unit 100 when the charge held by the photoelectric conversion unit 100 reaches saturation, or the voltage value between the photoelectric conversion unit 100 and the power supply voltage VDD.

[0073] The counting control signal generation unit 40 generates a counting initialization signal INIT and a counting stop signal STOP to control the counter unit 103. The counting initialization signal INIT is a control signal used to initialize the count value of the counter unit 103 to 0. The counting stop signal STOP is a signal that controls whether the counting operation of the counter unit 103 is started or stopped.

[0074] exist Figure 3 The timeline shows two frames of camera action. The first frame corresponds to relatively strong incident light, and the second frame corresponds to relatively weak incident light.

[0075] like Figure 3 As shown, when the reset signal RST is high, the initialization unit 101 initializes the output signal PD of the photoelectric conversion unit 100 to the output signal VINI output by the reset voltage generation unit 20.

[0076] When the counting stop signal STOP output by the counting control signal generation unit 40 is low, the counter unit 103 counts the number of times the reset signal RST changes from low to high and outputs the counting result to the counting signal OUT. When the counting stop signal STOP is high, the counting stops. If the counting initialization signal INIT becomes high, the count value is initialized to 0.

[0077] In addition, by setting the reference signal REF to a power supply voltage VDD that is higher than the output signal VINI, the reset signal RST becomes high, the photoelectric conversion unit 100 is initialized, and by setting the count initialization signal INIT and the count stop signal STOP to high, the count signal OUT1 is initialized to 0.

[0078] Furthermore, by setting the counting initialization signal INIT and the counting stop signal STOP to low levels and setting the reference signal REF to a voltage lower than the output signal VINI, the reset signal RST becomes low, initialization stops, the voltage of the output signal PD decreases from the output signal VINI at a rate corresponding to the amount of light irradiation, and at the time point when the voltage of the output signal PD reaches the voltage REF, the reset signal RST changes to high level, the counting signal OUT becomes 1, and the photoelectric conversion unit 100 is initialized, the voltage of the output signal PD becomes the output signal VINI, and the reset signal RST becomes low.

[0079] Furthermore, the voltage of the output signal PD decreases from the output signal VINI at a rate corresponding to the amount of light irradiation. When the voltage VERF is reached, the reset signal RST changes to a high level, the count signal OUT becomes 2, and the photoelectric conversion unit 100 is initialized. The voltage of the output signal PD becomes the output signal VINI.

[0080] Furthermore, when the counting stop signal STOP becomes high, the counting signal continues to maintain the count value at that point in time, thereby generating a digital signal OUT1 corresponding to the amount of light irradiated onto the photoelectric conversion unit 100 for each pixel unit.

[0081] The above, in Figure 2A , Figure 3 The solid-state imaging device 200 of this embodiment, as described in the description, resets after accumulating a certain amount of charge and outputs the number of resets as a digital value. By generating digital signals for each pixel unit, the solid-state imaging device 200 can perform high-speed imaging. Furthermore, even when strong light, insufficient for photoelectric conversion by the photoelectric conversion unit 100, illuminates the photoelectric conversion unit 100, the photoelectric conversion unit 100 generates digital signals while being initialized, thus enabling imaging even in bright conditions exceeding the conversion capability of the photoelectric conversion unit 100.

[0082] Furthermore, since the photoelectric conversion unit 100 can perform imaging even when the light-receiving area is reduced, the solid-state imaging device 200 can be miniaturized and its cost reduced.

[0083] Additionally, if the counter section 103 has M bits, then the initialization count can be counted up to (2^30) times. M -1) times. M can be determined, for example, based on the difference between VINI and REF.

[0084] Additionally, pixel unit 10 can also be as follows Figure 2B The circuit 108, which has an SF (source follower), is shown. Figure 2C This illustrates the structure of the SF108 circuit. For example... Figure 2C As shown, the SF circuit 108 consists of an amplifying transistor 108a and a current source 108b. The amplifying transistor 108a converts the potential generated by the charge in the photoelectric conversion unit 100 into a voltage and outputs it to the comparator unit 102. The current source 108b is a load that supplies load current to the amplifying transistor 108a, and can be, for example, composed of a resistor, diode, transistor, etc. Figure 2B This configuration can suppress the destruction of the charge in the photoelectric conversion unit 100, thereby stabilizing its operation.

[0085] (Implementation Method 2)

[0086] In Embodiment 2, a solid-state imaging device that can achieve higher precision than Embodiment 1 by having an AD conversion unit 50 will be described.

[0087] Figure 4 This is a diagram showing a structural example of the solid-state imaging device 200 according to Embodiment 2. Figure 5 It means Figure 4 The timeline of the operation of the solid-state camera device 200 shown is shown.

[0088] according to Figure 4 , Figure 5 The solid-state imaging device 200 of this embodiment is relative to the solid-state imaging device 200 in the present embodiment. Figure 2A The difference between the solid-state imaging device 200 shown in the figure is that it has an AD conversion unit 50 connected to the pixel unit 10 and a digital signal processing unit 60. Hereinafter, the description will focus on the differences to avoid repetition.

[0089] The AD conversion unit 50 performs AD conversion on the potential of the photoelectric conversion unit 100 after it is last initialized within the frame, and outputs the AD-converted data as a second signal representing the intensity of the incident light. Specifically, the AD conversion unit 50 outputs a digital signal OUT2 corresponding to the voltage of the output signal PD after the counter unit 103 stops counting. The AD conversion unit 50 can be, for example, a single-slope AD converter. Alternatively, the AD conversion unit 50 can be, for example, a successive approximation type or other types.

[0090] The digital signal processing unit 60 generates a third digital signal OUT3, representing the intensity of the incident light, by combining the counting signal OUT1 (as a first signal) with the digital signal OUT2 (as a second signal). For example, the digital signal processing unit 60 combines the counting signal OUT1 with the digital signal OUT2 to generate a new digital signal OUT3. Figure 5 In this example, the counting signal OUT1 is 5, and the digital signal OUT2 is 6. Assume the AD converter 50 is 4-bit with a resolution of 16. Furthermore, assume the counter 103 is 12-bit with a resolution of 2. 12 In this case, the digital signal OUT3 is 16 bits with a resolution of 2. 16 The digital signal OUT3 becomes (16 × counting signal OUT1 + digital signal OUT2) = (16 × 5 + 6) = 96.

[0091] If the number of bits in the counter section 103 is M and the number of bits in the AD converter section 50 is L, then the number of bits in the digital signal OUT3 is M+L bits.

[0092] Alternatively, the digital signal processing unit 60 can also simply link the M-bit data of the counting signal OUT1 and the L-bit data of the digital signal OUT2 as MSB-side data and LSB-side data.

[0093] In addition, the digital signal processing unit 60 can also combine the M-bit data of the counting signal OUT1 and the L-bit data of the digital signal OUT2 as MSB-side data and LSB-side data through calculation into a digital signal OUT3 with fewer bits than (M+L).

[0094] Conversely, the digital signal processing unit 60 can also combine the M-bit data of the counting signal OUT1 and the L-bit data of the digital signal OUT2 as MSB-side data and LSB-side data through calculation into a digital signal OUT3 with more bits than (M+L).

[0095] The above, in Figure 4 , Figure 5 The solid-state imaging device of this embodiment, as described herein, performs AD conversion on the margin and outputs a digital signal corresponding to the number of resets. This enables the output of a higher-resolution digital signal, corresponding to the amount of light irradiation, achieving excellent imaging that more closely reproduces the brightness and tone of the external environment.

[0096] Alternatively, the AD conversion unit 50 can be set for each pixel unit 10. This makes it easy to implement a global shutter.

[0097] Furthermore, the AD conversion unit 50 can also be configured according to a predetermined number of pixel units 10. The predetermined number of pixel units 10 can be pixel units 10 belonging to the same column. If the predetermined number of pixel units is pixel units per column, a so-called rolling shutter can be easily implemented.

[0098] In addition, Figure 5 In this configuration, the digital signal processing unit 60 can also perform CDS (correlated double sampling) during the AD conversion with margin. Furthermore, the digital signal processing unit 60 can also perform CDS using the AD conversion unit 50 in each interval from the initialization of the output signal PD (excluding margin) to the next initialization. Furthermore, it is also possible to selectively determine in advance or dynamically whether to perform CDS in each interval. For example, CDS can be performed on the output signal PD up to the first initialization, or CDS can be performed only in low illumination conditions.

[0099] (Implementation Method 3)

[0100] In Embodiment 3, a structure comprising a feedback circuit that feeds back the potential of the photoelectric conversion unit 100 to the photoelectric conversion unit 100 via the initialization unit 101 during initialization will be described. By feeding back the initial voltage, kTC noise during initialization can be eliminated.

[0101] Figure 6A This is a diagram illustrating a structural example of the solid-state imaging device 200 according to an embodiment. Figure 7 It means in Figure 6A The timeline of the operation of the solid-state camera device 200 is shown in the figure.

[0102] according to Figure 6A , Figure 7 The solid-state imaging device 200 of this embodiment is relative to the solid-state imaging device 200 in the present embodiment. Figure 2A The difference between the solid-state imaging device 200 shown in the figure is that the pixel unit 10 has an inverting amplifier 104 and an inverting amplifier 105 instead of the comparator 102, and has a feedback circuit for the inverting amplifier 105 that includes the output signal VINI of the input reset voltage generation unit 20.

[0103] The inverting amplifier 104 is an operational amplifier. Similar to the comparator 102, it compares the voltage of the output signal PD of the photoelectric conversion unit 100 with the voltage of the reference signal REF output by the REF voltage generation unit 30. As a reset signal RST, it outputs a low level when the voltage of the output signal PD is high and a high level when it is low.

[0104] Furthermore, the inverting amplifier 105 is an operational amplifier that forms a feedback circuit that feeds back the potential of the photoelectric conversion unit 100 to the photoelectric conversion unit 100 via the initialization unit 101 during initialization. Specifically, the inverting amplifier 105 amplifies and outputs the difference between the voltage of the output signal PD and the output signal VINI output by the reset voltage generation unit 20.

[0105] The above, in Figure 6A , Figure 7 The solid-state imaging device of this embodiment described herein performs feedback reset. Based on these structures and drives, by generating digital signals per pixel unit, high-speed imaging is possible. Furthermore, even when strong light, insufficient for photoelectric conversion by the photoelectric conversion unit 100, illuminates the photoelectric conversion unit 100, the photoelectric conversion unit 100 generates digital signals while being initialized. Therefore, imaging is possible even in bright conditions exceeding the conversion capability of the photoelectric conversion unit 100. Moreover, by adding an inverting amplifier 105 to feed back the amplified signal for initialization, noise during initialization can be reduced. Figure 7 As shown, the newly initialized output signal PD can be made consistent with a level that has less deviation caused by noise. As a result, good video recording with less noise can be achieved even in low-light conditions.

[0106] in addition, Figure 6A Pixel unit 10 can also be like Figure 6B As shown, it includes a transfer transistor 109, an overflow drain section 110, and an overflow drain control transistor 111.

[0107] The transfer transistor 109 is a transfer transistor that transfers excess charge from the photoelectric conversion unit 100 to the overflow drain unit 110. The gate of the transfer transistor 109 is set with a voltage Vov that allows excess charge to pass through.

[0108] The overflow drain section 110 is set as a port for discharging charge at voltage Vd when the overflow drain control transistor 111 is in the on state. Voltage Vd can be, for example, the power supply voltage Vdd, or other voltage values.

[0109] according to Figure 6B By setting the overflow drain control transistor 111 to the off state during photoelectric conversion, the voltage of the overflow drain 110 changes corresponding to the charge overflowing from the photoelectric conversion unit 100. When the potential of the overflow drain 110 drops to the voltage of the reference signal REF, the inverting amplifier 104 and the initialization unit 101 reset the photoelectric conversion unit 100. This reduces the number of components connected to the photoelectric conversion unit 100, increases the voltage of each charge generated, and, for example, relatively suppresses the noise effects of the AD converter 50.

[0110] (Implementation Method 4)

[0111] In Embodiment 4, a structural example combining Embodiment 2 and Embodiment 3 will be described.

[0112] Figure 8 This is a diagram showing a structural example of the solid-state imaging device 200 according to Embodiment 4. Figure 8 The solid-state imaging device 200 replaces the one in Embodiment 2. Figure 4 The pixel unit 10 is provided with the embodiment 3. Figure 6A Pixel unit 10.

[0113] Figure 8 The solid-state imaging device 200 shown includes an AD conversion unit 50 and a digital signal processing unit 60 connected to the pixel unit 10. The AD conversion unit 50 outputs a digital signal OUT2 corresponding to the voltage of the output signal PD after the counter unit 103 stops counting. The digital signal processing unit 60 combines the counting signal OUT with the digital signal OUT2 to generate a new digital signal OUT3.

[0114] also, Figure 8In addition to feedback reset, the solid-state camera device 200 shown also performs AD conversion on the margin and outputs digital data corresponding to the number of resets. This enables it to output a higher precision digital signal based on the amount of light irradiation, thereby achieving the reproduction of brightness and hue that are closer to the outside world.

[0115] (Implementation Method 5)

[0116] In Embodiment 5, a structural example is described where the initialization unit 101 performs initialization when the output line representing the comparison result of the comparison unit is reversed, and the potential of the photoelectric conversion unit 100 is fed back to the photoelectric conversion unit 100 via the initialization unit 101.

[0117] Figure 9 This is a diagram showing a structural example of the solid-state imaging device 200 according to Embodiment 5. Figure 10 It means in Figure 9 The timeline of the operation of the solid-state camera device 200 is shown in the figure.

[0118] according to Figure 9 , Figure 10 The solid-state imaging device 200 of this embodiment is relative to the solid-state imaging device 200 in the present embodiment. Figure 1A As shown in the solid-state imaging device 200, the pixel unit 10 further includes an amplification unit 106 and an initialization control unit 107. The solid-state imaging device 200 also includes a reset voltage generation unit 20, a REF voltage generation unit 30, a counting control signal generation unit 40, an AD conversion unit 50, a digital signal processing unit 60, and an initialization control unit 107 connected to the pixel unit 10.

[0119] In addition, the amplification unit 106 amplifies and outputs the difference between the voltage of the output signal PD of the photoelectric conversion unit 100 and the voltage of the reference signal REF2 output by the REF voltage generation unit 30.

[0120] Furthermore, when the initialization selection signal SEL output from the initialization control unit 107 is low, the initialization control unit 107 connects the output signal CNT of the amplification unit 106 to the input signal SET for the initialization unit 101, and connects the initialization signal CTL output from the initialization control unit 107 to the reset signal RST for the initialization unit 101. When the initialization selection signal SEL is high, the output signal CNT is connected to the reset signal RST, and the initialization voltage signal INI2 output from the initialization control unit 107 is connected to the input signal SET.

[0121] Furthermore, when the reset signal RST is high, the initialization unit 101 initializes the voltage of the output signal PD by connecting the output signal PD of the photoelectric conversion unit 100 to the input signal SET. When the reset signal RST is low, the input signal SET is disconnected from the output signal PD, causing the output signal PD to become a floating state.

[0122] Furthermore, when the counting stop signal STOP output by the counting control signal generation unit 40 is low, the counter unit 103 counts the number of times the reset signal RST changes from low to high, and outputs the counting result to the counting signal OUT. When the counting stop signal STOP is high, the counting stops. When the counting initialization signal INI becomes high, the count value is initialized to 0.

[0123] Furthermore, by setting the reference signal REF2 to the output signal VINI, setting the initialization selection signal SEL to low level, and setting the initialization signal CTL to high level, the photoelectric conversion unit 100 is initialized to the output signal VINI, and by setting the counting initialization signal INT and the counting stop signal STOP to high level, the counting signal OUT is initialized to 0.

[0124] Furthermore, by setting the count initialization signal INI and the count stop signal STOP to low level, setting the reference signal REF to a voltage VERF lower than the output signal VINI, and setting the initialization selection signal SEL to high level, the feedback path between the input and output of the amplifier 106 is disconnected, and the amplifier 106 essentially functions as a comparator. The output signal CNT becomes low level, initialization stops, and the voltage of the output signal PD decreases from the output signal VINI at a rate corresponding to the amount of light irradiation. At the point when the voltage of the output signal PD reaches the voltage VERF, the reset signal RST changes to high level, the count signal OUT becomes 1, and the photoelectric conversion unit 100 is initialized. The voltage of the output signal PD becomes the output signal VINI2 of the count initialization signal INI2, and the reset signal RST becomes low level.

[0125] Furthermore, the voltage of the output signal PD decreases from the output signal VINI at a rate corresponding to the amount of light irradiation. When the voltage VERF is reached, the output signal CNT changes to a high level, the counting signal OUT becomes 2, and the photoelectric conversion unit 100 is initialized. The voltage of the output signal PD becomes the output signal VINI2.

[0126] Furthermore, by making the counting stop signal STOP high and by continuously maintaining the count value at that time point by the counting signal, a digital signal corresponding to the amount of light irradiated onto the photoelectric conversion unit 100 is generated for each pixel unit.

[0127] The above, in Figure 9 , Figure 10 The solid-state imaging device of this embodiment described herein has a structure that shares an inverting amplification unit with the comparison unit. Through these structures and driving mechanisms, digital signals are generated for each pixel unit, enabling high-speed imaging. Furthermore, even when strong light, insufficient for photoelectric conversion by the photoelectric conversion unit 100, illuminates the photoelectric conversion unit 100, the photoelectric conversion unit 100 generates digital signals while being initialized. Therefore, imaging is possible even in bright conditions exceeding the conversion capability of the photoelectric conversion unit 100. Moreover, by using a structure and driving mechanism that initializes only the initial signal by feeding back the amplified signal, good imaging with low noise can be achieved, even in darker conditions where low noise is particularly important. Furthermore, by reducing the number of components, it achieves low power consumption and smaller pixel sizes, thereby enabling imaging with higher spatial precision.

[0128] (Implementation Method 6)

[0129] In Embodiment 6, a structural example of supplying a tapered gate signal to the gate of the transistor constituting the initialization unit 101 will be described.

[0130] Figure 11A This is a diagram showing a structural example of the solid-state imaging device according to Embodiment 6. Furthermore, Figure 11B It means by Figure 11A A diagram of the voltage waveform generated by the tapered voltage generating section 70.

[0131] Figure 11A Compared to Figure 8 The difference lies in the addition of a tapered voltage generating section 70. The following explanation focuses on these differences.

[0132] When a signal indicating that the potential of the photoelectric conversion unit 100 is consistent with a predetermined reference signal is input from the inverting amplifier unit 104, the cone-shaped voltage generation unit 70 generates a cone-shaped voltage that changes over time and supplies it to the gate of the transistor in the initialization unit 101.

[0133] Therefore, the solid-state imaging device 200 of this embodiment 6, by using a conical reset to control the switching on and off of a signal whose voltage changes proportionally over time by limiting the bandwidth of the photoelectric conversion unit 100 during initialization, increases the noise reduction effect in the output signal PD superimposed on the photoelectric conversion unit 100, and can perform good imaging with less noise even in darker environments.

[0134] (Implementation Method 7)

[0135] In Embodiment 7, an example is described that consists of two semiconductor substrates on which the solid-state imaging device 200 is stacked.

[0136] Figure 12 This is a diagram illustrating a structural example of a solid-state imaging device 200 according to an embodiment. The solid-state imaging device 200 in this diagram includes a first semiconductor substrate 201 having a photoelectric conversion unit 100 and a second semiconductor substrate 202 having a counter unit 103. The first semiconductor substrate 201 and the second semiconductor substrate 202 are stacked and electrically connected.

[0137] according to Figure 12 The photoelectric conversion unit 100 and the counter unit 103 are disposed on different semiconductor substrates. Furthermore, the photoelectric conversion unit 100 and the counter unit 103 can employ... Figures 1A to 11B One of the solid-state camera devices 200 described herein.

[0138] Therefore, by stacking the photoelectric conversion unit 100 and the counter unit 103, the area of ​​each pixel unit can be reduced, enabling higher spatial resolution imaging.

[0139] In addition, the second semiconductor substrate 202 may include an AD conversion unit 50.

[0140] Industrial availability

[0141] The ranging camera device of the present invention can be used, for example, in cameras and ranging sensors.

[0142] Label Explanation

[0143] 10-pixel unit

[0144] 20 Reset voltage generation unit

[0145] 30 REF voltage generation section

[0146] 40 Counting control signal generation unit

[0147] 50 AD Conversion Unit

[0148] 60 Digital Signal Processing Department

[0149] 70 Conical voltage generating section

[0150] 100 Photoelectric Conversion Unit

[0151] 101 Initialization Section

[0152] 102 Comparison Section

[0153] 103 Counter Section

[0154] 104 Inverting Amplifier Section

[0155] 105 Inverting Amplifier Section

[0156] 106 Enlarged section

[0157] 107 Initialization Control Unit

[0158] 108 SF circuit

[0159] 108a Amplifying Transistor

[0160] 108b Current Source

[0161] 109 Transmission Transistors

[0162] 110 Overflow Drain

[0163] 111 Overflow Drain Controlled Transistor

[0164] 200 Solid-State Camera Device

[0165] 201 First Semiconductor Substrate

[0166] 202 Second Semiconductor Substrate

Claims

1. A solid-state imaging device characterized by comprising a plurality of pixel units arranged in a matrix shape; the plurality of pixel units each comprising: a photoelectric conversion section that generates electric charges through photoelectric conversion and holds a potential corresponding to an amount of the generated electric charges; an initialization section that initializes the potential of the photoelectric conversion section; an amplification section that amplifies and outputs a difference between a voltage of an output signal of the photoelectric conversion section and a voltage of a reference signal; a counter section that counts a number of times of initialization performed by the initialization section and outputs a signal corresponding to the number of times as a first signal indicating intensity of incident light; and an initialization control section that, in a case where an initialization selection signal output from the initialization control section is at a high level, connects an output line of the amplification section to a reset signal line for the initialization section, and in a case where the reset signal is at the high level, causes the initialization section to perform initialization and feeds back the potential of the photoelectric conversion section to the photoelectric conversion section via the initialization section.

2. The solid-state imaging device according to claim 1, characterized by further comprising an AD conversion section that AD-converts the potential of the photoelectric conversion section after the last initialization and outputs AD-converted data as a second signal indicating intensity of incident light.

3. The solid-state imaging device according to claim 2, characterized in that the AD conversion section is provided for each pixel unit.

4. The solid-state imaging device according to claim 2, characterized in that the AD conversion section is provided for each predetermined number of pixel units.

5. The solid-state imaging device according to any one of claims 2 to 4, characterized by further comprising a signal processing section that generates a third signal indicating intensity of incident light by synthesizing the first signal and the second signal.

6. The solid-state imaging device according to any one of claims 1 to 4, characterized in that the initialization control section, in a case where the initialization selection signal is at a low level, connects the output line of the amplification section to an input signal line for the initialization section and connects a signal line from which an initialization signal is output from the initialization control section to the reset signal line for the initialization section, and in a case where the initialization selection signal is at the high level, connects the output line of the amplification section to the reset signal line and connects a signal line from which an initialization voltage signal is output from the initialization control section to the input signal line for the initialization section, the initialization section, in a case where a signal of the reset signal line is at the high level, initializes the potential of the photoelectric conversion section by connecting an output of the photoelectric conversion section to the input signal line, and in a case where the signal of the reset signal line is at the low level, causes the output of the photoelectric conversion section to be in a floating state by cutting off the input signal line from the output of the photoelectric conversion section.

7. The solid-state imaging device according to any one of claims 1 to 4, characterized in that the plurality of pixel units each further comprise: an overflow drain section for discharging electric charges; and an overflow drain section for discharging electric charges; and ​ ​ ​ ​ ​ ​ ​ a transfer transistor that transfers the charge exceeding the prescribed amount of the photoelectric conversion section to the overflow drain section; a potential of the overflow drain section is input to the amplification section as a potential of the photoelectric conversion section.

8. The solid-state imaging device according to any one of claims 1 to 4, characterized by comprising: a first semiconductor substrate having the photoelectric conversion section; and a second semiconductor substrate having the counter section. comprising: a first semiconductor substrate having the photoelectric conversion section; and a second semiconductor substrate having the counter section; the first semiconductor substrate and the second semiconductor substrate are stacked.

9. The solid-state imaging device according to any one of claims 2 to 4, characterized by comprising: a first semiconductor substrate having the photoelectric conversion section; and a second semiconductor substrate having the AD conversion section; comprising: a first semiconductor substrate having the photoelectric conversion section; and a second semiconductor substrate having the AD conversion section; the first semiconductor substrate and the second semiconductor substrate are stacked.

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